ITS2.5/CL4.14 | Aeolian dust: initiator, player, and recorder of environmental change
EDI PICO

The interactions between aerosols, climate, and weather are among the large uncertainties of current atmospheric research. Mineral dust is an important natural source of aerosol with significant implications on radiation, cloud microphysics, atmospheric chemistry and the carbon cycle via the fertilization of marine and terrestrial ecosystems. In addition, properties of dust deposited in sediments and ice cores are important (paleo-)climate indicators.

This interdivisional session --building bridges between the EGU divisions CL, AS, SSP, BG and GM-- had its first edition in 2004 and it is open to contributions dealing with:

(1) measurements of all aspects of the dust cycle (emission, transport, deposition, size distribution, particle characteristics) with in situ and remote sensing techniques,

(2) numerical simulations of dust on global, regional, and local scales,

(3) meteorological conditions for dust storms, dust transport and deposition,

(4) interactions of dust with clouds and radiation,

(5) influence of dust on atmospheric chemistry,

(6) fertilization of ecosystems through dust deposition,

(7) any study using dust as a (paleo-)climate indicator, including sediment archives in loess, ice cores, lake sediments, ocean sediments and dunes.

We especially encourage the submission of papers that integrate different disciplines and/or address the modelling of past, present and future climates.

ISAR
Convener: Jan-Berend Stuut | Co-conveners: Martina Klose, Mingjin Tang, Adolfo Gonzalez RomeroECSECS, Claire Ryder
PICO
| Tue, 25 Apr, 08:30–12:30 (CEST), 14:00–15:45 (CEST)
 
PICO spot 2
Tue, 08:30

PICO: Tue, 25 Apr | PICO spot 2

Chairpersons: Jan-Berend Stuut, Martina Klose
08:30–08:35
Physical and chemical properties of dust particles
08:35–08:45
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PICO2.1
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EGU23-3721
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ITS2.5/CL4.14
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ECS
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solicited
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Virtual presentation
Adeyemi Adebiyi, Jasper Kok, Benjamin Murray, Claire Ryder, Jan-Berend Stuut, Ralph Kahn, Peter Knippertz, Paola Formenti, Natalie Mahowald, Carlos Perez García-Pando, Martina Klose, Albert Ansmann, Bjørn Samset, Akinori Ito, Yves Balkanski, Claudia Di Biagio, Manolis Romanias, Yue Huang, and Jun Meng

Mineral dust is an important aerosol specie in the atmosphere that impacts the Earth’s climate system through its interactions with radiation, clouds, hydrology, atmospheric chemistry, and biogeochemistry. Because dust sizes span more than three orders of magnitude in diameter and dust properties are size-dependent, most previous studies separate dust particles into different classes – broadly defined as fine and coarse dust – which could produce distinct impacts on the Earth system. However, there are general inconsistencies in the terminology, the diameter boundaries, and diameter ranges currently attributed to dust size classes across the literature. As part of a comprehensive review of coarse dust recently completed, we propose, with justification, a new uniform classification that defines coarse and super-coarse dust as particles between 2.5 - 10 µm and 10 - 62.5 µm in diameter, respectively. In addition, we will show several lines of observational evidence that indicate coarse and super-coarse dust particles are transported much farther than previously expected and that the abundance of these particles is substantially underestimated in current global models. Despite the limitations of representing coarse and super-coarse dust aerosols in models, we will highlight their unique impacts on several aspects of the Earth's climate system.

How to cite: Adebiyi, A., Kok, J., Murray, B., Ryder, C., Stuut, J.-B., Kahn, R., Knippertz, P., Formenti, P., Mahowald, N., Perez García-Pando, C., Klose, M., Ansmann, A., Samset, B., Ito, A., Balkanski, Y., Di Biagio, C., Romanias, M., Huang, Y., and Meng, J.: What are coarse dust aerosols, and how do they impact the Earth's climate system?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3721, https://doi.org/10.5194/egusphere-egu23-3721, 2023.

08:45–08:47
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PICO2.2
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EGU23-8190
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ITS2.5/CL4.14
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On-site presentation
Claudia Di Biagio, Jean Francois Doussin, Mathieu Cazaunau, Edouard Pangui, Paul Kleiber, Juan Cuesta, Mila Rodenas, and Paola Formenti

The mineralogy of dust aerosols (i.e. the abundance, relative proportions and state of mixing of the different minerals composing the aerosols, including mainly silicates in the form of clays, quartz, and feldspars, carbonates, sulfates, and iron and titanium oxides) is of key relevance in driving its climatic and environmental effects. Ground–based and airborne observations support the evidence that the dust mineralogy is heterogeneous in the atmosphere, varying from local to global scale due to changes in the mineralogical composition of the emitting source soils and atmospheric processing. However, the capability to get regional and global mapping of airborne dust mineralogy is still missing to date. This gap represents a fundamental limitation for properly developing and validating the representation of dust in Earth System Models and constraining its regional and global climate forcing.

Because the different minerals composing the fine and coarse fractions of dust show different spectral absorption signatures, remote sensing spectral and hyperspectral observations can be used to fill this gap by detecting the presence of diverse minerals and reconstructing their relative proportions in the dust aerosols. Based on this idea, recent efforts move into this direction, including the EMIT mission (Earth Surface Mineral Dust Source Investigation) started in 2022.

In this study we demonstrate, starting from exemplary data acquired in the CESAM simulation chamber on dust aerosols from global sources (Di Biagio et al., 2017), that the extinction signature of suspended dust aerosols in the 740−1475 cm−1 infrared spectral range (6.8−13.5 µm) can be used to derive dust mineralogy in terms of its infrared−active and coarse−sized minerals: quartz, clays, feldspars and calcite. We show that diverse spectral infrared signatures allow to distinguish dust aerosols from different sources worldwide with variable composition, and that following the changes of the dust extinction spectra with time informs on particles size−selective mineralogy changes during atmospheric transport. Results from the present study confirm the major advance that hyperspectral infrared remote sensing observations, as those by IASI (Infrared Atmospheric Sounding Interferometer) and the IASI−NG (Next Generation) instruments, can provide to dust science.

 

Di Biagio, C., Formenti, P., Balkanski, Y., Caponi, L., Cazaunau, M., Pangui, E., Journet, E., Nowak, S., Caquineau, S., Andreae, M. O., Kandler, K., Saeed, T., Piketh, S., Seibert, D., Williams, E., and Doussin, J.-F.: Global scale variability of the mineral dust long-wave refractive index: a new dataset of in situ measurements for climate modeling and remote sensing, Atmos. Chem. Phys., 17, 1901–1929, https://doi.org/10.5194/acp-17-1901-2017, 2017.

How to cite: Di Biagio, C., Doussin, J. F., Cazaunau, M., Pangui, E., Kleiber, P., Cuesta, J., Rodenas, M., and Formenti, P.: The mineralogy of coarse dust aerosols retrieved from its mid−infrared extinction spectra: a laboratory testbed study on dust from worldwide sources, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8190, https://doi.org/10.5194/egusphere-egu23-8190, 2023.

08:47–08:49
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PICO2.3
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EGU23-16902
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ITS2.5/CL4.14
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Virtual presentation
Kalliopi Violaki, Andrea Mario Arangio, and Athanasios Nenes

Aeolian dust plays a major role in Earth’s climate, by absorbing and scattering radiation, and by influencing the hydrological and biogeochemical cycles. Saharan dust is a significant carrier of limited nutrients (e.g., iron and phosphorus) in many regions of the global ocean but also transfer toxic elements such as chromium, cadmium, arsenic, and lead, influencing public health and ecosystems. Annually, Europe receives millions of tons of Saharan dust while climate change is expected to increase the frequency and severity of dust episodes, especially in the south and central part, with unknown impact on sensitive ecosystems.  

During this study, aerosol particles were collected with a size-segregated hi-volume sampler (Tisch 230-High Volume Cascade Impactor). The impactor separated the particles in six different stages; from larger than 7.2 µm to less than 0.49 µm. Those samples were used to characterize the properties of dust particles during the severe dust episodes in Spring, 2021 in a forest site near Lausanne, Switzerland. We analyzed trace metals and nutrients (Fe, Cu, P, N), inorganic ions, sugars, and phospholipids. Preliminary results showed that a single dust episode can cause an increase of poisonous metals, such as lead and arsenic, by up to four times, affecting public health. In addition, it could be responsible for a large fraction of nutrients deposition - accounting for a significant part of the total annual deposition in the terrestrial and lake ecosystems in the area.

How to cite: Violaki, K., Arangio, A. M., and Nenes, A.: Size distribution of atmospheric particles during the Saharan dust episodes over central Europe in Spring 2021, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16902, https://doi.org/10.5194/egusphere-egu23-16902, 2023.

08:49–08:51
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PICO2.4
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EGU23-466
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ITS2.5/CL4.14
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ECS
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On-site presentation
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Francesco Battaglia, Paola Formenti, Mathieu Cazaunau, Vincent Michoud, Antonin Berge, Edouard Pangui, Gael Noyalet, Servanne Chevaillier, Chiara Giorio, Sara D'Aronco, Philippe Decorse, and Jean-Francois Doussin

Mineral dust aerosols, which account for about 40% of global annual aerosol emissions, contribute to the persistent and large uncertainties on the global radiative budget and the oxidative capacity of the atmosphere.

Indeed, the uptake of atmospheric volatile organic compounds (VOCs) on mineral dust particles can contribute to the formation of secondary organic aerosols (SOA), with consequent modification of the chemical and optical properties of the dust.

Glyoxal, one of the most important VOC in the atmosphere, is a precursor of SOA, capable of interacting with mineral dust and forming SOA as a consequence of the interaction.

In this experimental study we investigate the formation of SOA by the uptake of glyoxal on mineral dust particles. We present the results of the heterogeneous interaction obtained in the CESAM atmospheric simulation chamber (Chambre Expérimentale de Simulation Atmosphérique Multiphasique), used to conduct aging experiments in various controlled conditions in terms of relative humidity, irradiation, and gas phase composition. Prior entering the chamber, particles from a real soil sample (Gobi Desert) are size-selected using an aerodynamic aerosol classifier (AAC) in order to obtain a monodispersed size distribution centered at 300 nm in mobility diameter, narrow enough to be able to appreciate a dimensional variation from glyoxal condensation.

In experiments conducted in humid conditions (RH=80%), a rapid uptake of glyoxal was observed on sub micrometric dust particles. 15 minutes after the injection of 1 ppm of glyoxal into the chamber, the mass of the particles increased by about 10%, with a variation of the modal diameter of the size distribution. As a consequence of glyoxal uptake in humid conditions, an increase of the aerosol organic mass concentration occurred immediately after the interaction, which was not observed in dry conditions. At the same time, the aerosol chemical speciation monitor (ACSM) mass spectra of the organic fraction show the increase in intensity of the glyoxal marker signals at m/z 58 and m/z 29. It is interesting to note also the drop of O/C ratio of the dust organic fraction after the injection of the glyoxal from 1.5 (the one of the dust itself) to a value close to 1, that is the one of the glyoxal.

Hence, the first results of the study suggest the presence of a fast glyoxal uptake on submicronic mineral dust particles in high relative humidity conditions. This process modifies the mass and the size distribution of the aerosol, as well as the chemical composition of its organic fraction.

How to cite: Battaglia, F., Formenti, P., Cazaunau, M., Michoud, V., Berge, A., Pangui, E., Noyalet, G., Chevaillier, S., Giorio, C., D'Aronco, S., Decorse, P., and Doussin, J.-F.: Climate relevant processing of mineral dust by volatile organic compounds: first results on composition of complex dust/organic systems from the uptake of glyoxal, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-466, https://doi.org/10.5194/egusphere-egu23-466, 2023.

08:51–08:53
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PICO2.5
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EGU23-17385
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ITS2.5/CL4.14
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ECS
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On-site presentation
Quantification of major and trace elements in atmospheric dust over arid/semi-arid region of the Western India
(withdrawn)
Suresh Karunanithi, Athiyarath Sudheer, Mahesh Gaddam, and Ashwini Kumar
08:53–08:55
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PICO2.6
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EGU23-13991
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ITS2.5/CL4.14
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On-site presentation
Zongbo Shi and Clarissa Baldo

Millions of tonnes of dust are emitted into the atmosphere every year, a large proportion of which is transported and deposited to the oceans. Dust particles can directly affect the climate via dust–radiation interaction and indirectly via dust–cloud interaction, the snow/ice albedo effect and impacts on ocean biogeochemical cycles. Dust impacts on the climate and ecosystems depend on their mineralogical, chemical, microphysical, and optical properties. Over the past 20 years, important progress has been made in determining the properties of low-latitude dust and understanding how they change in the atmosphere.

The mineralogical compositions, including iron mineralogy, of northern African and Asian dust are now better known and show a large variability depending on the source region. Distinctive patterns were found. For example, more calcium minerals (such as calcite) are found in dust from the Taklamakan Desert and palaeolakes in northern Africa than in dust from the Gobi and Sahara Desert; the contribution of iron oxides to the total iron in Saharan dust (25%-40%) is lower than in Sahel dust (ca. 60%), whereas dust from palaeolakes, including that from the Bodele depression, has lower iron oxide content (<25%). Most of the Fe oxide particles from the Sahara and Gobi Desert are as goethite, while more hematite is found in Sahel dust. These new data have allowed a much better modelling of the role of low-latitude dust in the Earth system.

Only until recently, we started to study the properties of high-latitude dust, including from Iceland, Canada (Yukon), and Alaska. Icelandic dust particles are distinguished by the fact that most of them consist primarily of amorphous basaltic materials, up to 90 wt %. The total Fe content is usually very high (10%–13%), and hematite and goethite contribute only 1%–6% of the total Fe, which is significantly lower than in low-latitude dust (except in palaeolakes). Magnetite accounts for 7%–15% of the total Fe, which is orders of magnitude higher than in dust from northern Africa. Nevertheless, about 80%–90% of the Fe is contained in pyroxene and amorphous glass. Data from both low- and high-latitude dust showed that the iron mineralogy is associated with the degree of chemical weathering and the composition of the parent sediments.

The spectral single scattering albedo (SSA) of Icelandic dust falls within the range of low-latitude dust. The complex refractive index of dust is highly dependent on its source region, with Sahel and Icelandic dust showing highest values of imaginary index - k(λ). This indicates that Sahel and Icelandic dust is likely to be more absorbing. The measured spectral optical properties of both low- and high- latitude dust in the short-wave spectrum are consistent with what was predicted from their iron mineralogy.

The iron mineralogy in dust also determines the rate of dissolution during atmospheric processing, and thus its impact on ocean biogeochemical processes after dust deposition. For example, the high dissolution rate in the first few minutes in dust under acidic conditions is related to the content of amorphous Fe oxides.

How to cite: Shi, Z. and Baldo, C.: Key role of iron oxyhydroxides in dust aerosol from high and low latitudes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13991, https://doi.org/10.5194/egusphere-egu23-13991, 2023.

08:55–08:57
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PICO2.7
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EGU23-14832
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ITS2.5/CL4.14
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On-site presentation
Llorenç Cremonesi, Luca Teruzzi, Claudio Artoni, Claudia Ravasio, Mirko Siano, Marco A. C. Potenza, Barbara Delmonte, and Valter Maggi

Mineral dust aerosol plays an important role in climate and biogeochemical processes by providing nutrients to marine and terrestrial ecosystems and by influencing the radiation balance of the atmosphere. In turn, mineral dust responds to natural and anthropogenic alterations of land cover and land use resulting from several environmental changes that occurred on different timescales. Contamination by aerosols is a very tangible threat to the cryosphere in the European Alps due to its proximity to highly urbanized areas, cultivated landscapes, and the largest hot desert in the world. We recently developed and assembled a continuous flow analysis system for studying the solid content of ice cores with a high time resolution, focusing on optical characterization methods based on light scattering. The line is designed to provide an integrated measurement of dust particles with Single-Particle Extinction and Scattering (SPES), digital holography, and an optical particle sizer (Abakus). Many of the particles found in ice are efficient scatterers and absorbers close to the size range of the visible light wavelength. We report some preliminary results from ice cores drilled during the ADA270 project, aiming at an in-depth characterization of the samples that provide essential information on the fast climate evolution, which is causing a severe degeneration of glaciers, among other consequences.

How to cite: Cremonesi, L., Teruzzi, L., Artoni, C., Ravasio, C., Siano, M., Potenza, M. A. C., Delmonte, B., and Maggi, V.: Continuous flow analysis of Alpine ice cores: preliminary data and perspectives, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14832, https://doi.org/10.5194/egusphere-egu23-14832, 2023.

Dust variability and environmental impacts
08:57–08:59
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PICO2.8
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EGU23-9569
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ITS2.5/CL4.14
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ECS
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On-site presentation
Jerónimo Escribano, Enza Di Tomaso, Oriol Jorba, María Gonçalves Ageitos, Martina Klose, Sara Basart, and Carlos Pérez García-Pando

Mineral dust emissions play a fundamental role in the simulation of the dust cycle in numerical models. The emission of dust depends on a number of atmospheric and surface conditions that span a large range of time and spatial scales. Due to the inherent difficulties to physically represent this complexity in a simplified way, the emission of mineral dust is usually parameterized in the atmospheric numerical models. The heterogeneity of available dust emission parametrizations, along with the soil characteristics and meteorological information, the atmospheric models themselves, their tuning, and their boundary and initial conditions, contribute to the large spread of net dust flux estimated with different modeling frameworks.

This work presents a novel approach to estimate dust emissions through the assimilation of dust optical depth filtered retrievals from satellite measurements, by means of an ensemble-based data assimilation scheme. Because of the lagged nature of the emission inversion problem, the assimilation is produced with a slightly modified version of the ensemble Kalman Filter algorithm. We show results of the inversion for 5-year global numerical experiments (2017 to 2021), by using dust-only simulations with three of the available state-of-the-art dust emission schemes implemented in the chemical MONARCH model.

In these three experiments, we assimilate dust optical depth obtained from the SNPP-VIIRS Deep Blue retrievals. The control vector consists of model dust emissions at native spatial resolution (1.4 by 1 degrees) and a 3-days time resolution. We find regional and temporal corrections in the estimated emissions after assimilation that are consistent across the different dust emission scheme experiments, making our findings robust. We compare the dust optical depth of our simulations with the assimilated observations, as well as with independent dust-filtered optical depth from ground-based AERONET sun-photometers. The dust optical depth resulting from the simulations that use the corrected emissions show substantial improvements in the skill scores than the dust optical depth simulated with the uncorrected emissions. Our work paves the road toward quantifying and eventually reducing uncertainties in dust emission schemes and toward better constraining the contribution to climate of the dust sources at sub-regional scale.

How to cite: Escribano, J., Di Tomaso, E., Jorba, O., Gonçalves Ageitos, M., Klose, M., Basart, S., and Pérez García-Pando, C.: Constraining spatio-temporal variations in dust emission at global scale with ensemble data assimilation of satellite optical depth retrievals, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9569, https://doi.org/10.5194/egusphere-egu23-9569, 2023.

08:59–09:01
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PICO2.9
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EGU23-6167
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ITS2.5/CL4.14
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On-site presentation
Outi Meinander, Pavla Dagsson-Waldhauserova, and Ana Vucovic Vimic and the HLD team

Identifying the locations of local dust sources and their emission, transport, and deposition processes is important for understanding the multiple impacts of dust on the Earth's systems. We have recently provided a significant update to the scientific understanding on the climatically and environmentally significant high-latitude dust (HLD) sources. Based on the presented evidence (Meinander et al. 2022), we have suggested a “northern high latitude dust belt” (Meinander et al. 2022), defined as the area north of 50 N, with a “transitional HLD-source area” extending at latitudes 50–58 N in Eurasia and 50–55 N in Canada and a “cold HLD-source area” including areas north of 60 N in Eurasia and north of 58 N in Canada, with currently “no dust source” area between the HLD and low-latitude dust (LLD) dust belt, except for British Columbia. We estimate the high-latitude land area with potential dust activity to cover over 560 000 km2 with very high potential for dust emission, and over 240 000 km2 with the highest potential for dust emission.

We have identified, described, and quantified the source intensity (SI) values, which show the potential of soil surfaces for dust emission scaled to values 0 to 1 concerning globally best productive sources, using the Global Sand and Dust Storms Source Base Map (G-SDS-SBM). This includes 64 HLD sources in our collection for the northern (Alaska, Canada, Denmark, Greenland, Iceland, Svalbard, Sweden, and Russia) and southern (Antarctica and Patagonia) high latitudes. Our work also included model results on HLD emission, long-range transport, and deposition at various scales of time and space, and we have specified key climatic and environmental impacts of HLD and related research questions, which could improve our understanding of HLD sources, on clouds and climate feedback, atmospheric chemistry, marine environment, cryosphere, and cryosphere–atmosphere feedbacks. For example, we estimated that about 57% of the dust deposition in snow- and ice-covered Arctic regions was from high latitude dust sources.

We gratefully acknowledge Douglas Hamilton.

Citation: Meinander, O. et al. Newly identified climatically and environmentally significant high-latitude dust sources, Atmos. Chem. Phys., 22, 11889–11930, https://doi.org/10.5194/acp-22-11889-2022, 2022.

How to cite: Meinander, O., Dagsson-Waldhauserova, P., and Vucovic Vimic, A. and the HLD team: The northern hight latitude dust belt, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6167, https://doi.org/10.5194/egusphere-egu23-6167, 2023.

09:01–09:03
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PICO2.10
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EGU23-2678
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ITS2.5/CL4.14
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ECS
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On-site presentation
Rovina Pinto and Stephanie Fiedler

Arid and semi-arid regions are sources of mineral-dust aerosols but very little is known of the dust activity in the hyper-arid Atacama Desert. The limited moisture supply and barren landscape should promote dust emission via wind erosion but the Atacama rarely sees strong dust outbreaks. Our study is the first detailed assessment of the observed dust reports for the Atacama. We analysed dust reports and meteorological data from surface synoptic observations spanning 72 years (1950-2021) to quantify the frequency distribution of dust events in the Atacama Desert, analyze changes over time, and evaluate influencing factors on dust events. Furthermore, we computed the threshold wind speeds for dust events at the different stations. A total of 1920 dusty days were recorded over a period of 72 years across the Atacama, where a dusty day is defined as a day with at least one recorded dust event. There is no perceptible trend visible but the results indicate several year-long periods with enhanced dust activity. Most dust events were observed in the 1990s with a rapid decline in dust activity post the early 2000s. Of the 1920 dust days, 72 days had a visibility of less than a kilometre, of which 12 days also reported dust storms. Chañaral was the dustiest station in the region with about 20 dust days per year. There is little seasonality in the dust activity, but a strong diurnal cycle with most dust events between 1500 and 1800 local time. Threshold wind speeds, t5, t25 and t50, are estimated as the minimum wind speed required for 5, 25 and 50% of the dust event frequency distribution. The thresholds allow us to determine the lowest winds capable of emitting dust from the surface and infer spatial differences in soil conditions due to soil moisture or land cover. Given the varying geomorphology of the surfaces in the Atacama, different threshold wind speeds are found at the stations in the Atacama. The t5 threshold wind speeds range from 6 ms-1to 14 ms-1across the desert. The evaluation of all stations yields annual mean threshold wind speeds of 10.9 ±1.6 ms-1, 13.2 ±1.9 ms-1and 15.6 ±2.3 ms-1for t5, t25 and t50. Ongoing research aims to evaluate the findings for the threshold wind speed against measurements from the pi-swerL Atacama Measurement EXperiment (LAMEX) conducted in October 2022.

How to cite: Pinto, R. and Fiedler, S.: A Climatology of Dust Activity in the Atacama for 1950-2021, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2678, https://doi.org/10.5194/egusphere-egu23-2678, 2023.

09:03–09:05
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PICO2.11
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EGU23-17139
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ITS2.5/CL4.14
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On-site presentation
Ina Tegen and Anne Kubin

Mineral dust contributes significantly to the global atmospheric aerosol burden and is an important climate factor. Its model-based description of the atmospheric life cycle and impacts largely depends on an accurate parameterization of dust emissions. The large variability of near-source dust distribution in current forecast and aerosol-climate models is an indication that accurate simulation of dust emissions remains problematic. The occurrence and strength of dust emissions depends on both surface properties and surface winds. While satellite remote sensing offers great potential for determining relevant surface properties such as surface roughness and land use, model simulations of surface winds remain problematic in resolving strong wind events that occur on small spatial and temporal scales. The peak wind speeds of such events have the potential to cause strong dust emissions, but are unlikely to be captured in model simulations with parameterized convection.  Advances in high-resolution convection atmospheric modelling are a major opportunity for overcoming these limitations. Convection permitting simulations and multi-scale model approaches become feasible with the new ICON model framework which has been developed jointly by the German Weather Service (DWD) and the Max Planck Institute for Meteorology in Hamburg. Results of dust simulations with the HAM aerosol model coupled to ICON will be presented. The new model system will advance the flexibility and possibilities to work on understanding the role of mineral dust aerosol and their interactions within the changing climate. The new model system will improve the ability to understand the role of mineral dust aerosols and their interactions with the climate system.

How to cite: Tegen, I. and Kubin, A.: Towards improving dust emission simulations with the ICON-HAM model framework, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17139, https://doi.org/10.5194/egusphere-egu23-17139, 2023.

09:05–10:15
Coffee break
Chairpersons: Claire Ryder, Adolfo Gonzalez Romero
10:45–10:47
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PICO2.1
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EGU23-15181
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ITS2.5/CL4.14
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ECS
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On-site presentation
Anouk van Boxtel, Addison Rice, Gert de Lange, Francien Peterse, and Jan-Berend Stuut

Dust deposition can trigger phytoplankton growth in oligotrophic low nutrient low chlorophyl (LNLC) regions by providing essential nutrients to the surface ocean. As LNLC regions comprise 60% of the global ocean, dust fertilisation and potential subsequent increased downward carbon export could affect the strength of the biological carbon pump considerably. Additionally, ballasting effects of large dust particles could enhance downward carbon export even further, independent from fertilisation effects. However, compared to high nutrient low chlorophyl (HNLC) regions, the biogeochemical effect of dust deposition and its sensitivity to future climate change is less well understood for LNLC regions. For the LNLC Mediterranean Sea mesocosm experiments and satellite data suggest that some, but not all, dust events lead to increased primary production. However, the exact relationship between dust deposition, productivity and carbon export remains unresolved.  

Here, we aim to identify and quantify the relationships between Saharan dust deposition (deposition mode, dust source), phytoplankton response (changes in community composition, phytoplankton vs heterotrophic bacterial growth) and carbon export in the eastern Mediterranean Sea by studying an exceptional high-resolution, 30-year sediment-trap time series of settling Saharan dust particles and phytoplankton remains (partly at 500m, 1500m, and 2500m water depth), combining sedimentological, biogeochemical, and remote sensing techniques. We here present a combined record of dust and organic matter fluxes for one full year of the time series (April 2017 to May 2018, 2200m water depth). Furthermore, the response of specific phytoplankton groups to dust input as well as the input of terrestrial plant material associated with desert dust is determined based on the presence and distribution of lipid biomarkers in the trap material.

Dust fluxes vary substantially over this one-year period, but peaks occur during spring 2017 and 2018, summer 2017, as well as some smaller, less pronounced peaks during autumn 2017. Some of these dust events indeed correspond to increased fluxes of lipid biomarkers, suggesting a relationship between dust input and enhanced sinking of organic material. However, due to the depth of trap deployment, the record does not allow to differentiate between the influence of dust input as fertiliser or as ballasting effect. This will later be assessed by comparing biomarker records from sediment traps from different depths representing the surface and deep ocean. Nevertheless, the lipid biomarkers representing different phytoplankton groups (e.g., long-chain alkenones for coccolithophores, 23,24-dimethylcholesta-5,22E-dien-β-ol for diatoms, dinosterol for dinoflagellates, long-chain diols for eustigmatophytes) do not show a uniform response to dust input, indicating that the response of these phytoplankton groups depends on different conditions. Moreover, some dust events do not seem to trigger any phytoplankton response at all as they do not coincide with enhanced biomarker fluxes. This indicates that other factors such as dust source, deposition mode and/or trophic state of the surface ocean determine whether dust input triggers enhanced export of organic material or not. Differences in grain-size distribution and terrestrial plant content (indicated by terrestrial plant biomarkers) indeed suggest that the observed contrasting response might be due to differences in dust source and composition. 

How to cite: van Boxtel, A., Rice, A., de Lange, G., Peterse, F., and Stuut, J.-B.: Assessing the relationship between Saharan dust input and export of organic material in the deep eastern Mediterranean Sea using a one-year sediment-trap record, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15181, https://doi.org/10.5194/egusphere-egu23-15181, 2023.

10:47–10:49
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PICO2.2
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EGU23-990
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ITS2.5/CL4.14
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On-site presentation
Hamish McGowan, Nadav Lensky, Shai Abir, Yonathan Shaked, and Eyal Wurgaft

Coral reefs are complex biophysical, geochemical and hydrodynamic marine environments impacted by meteorological processes. In continental coastal and oceanic locations bordering or downwind of dust source areas, coral reefs are affected by the deposition of dust. Dust may supply nanomolar amounts of nitrate and essential bio-elements including iron, manganese, zinc and copper from natural, industrial and agricultural processes to coral reefs; in turn these are absorbed by the coral algae symbionts, thereby enhancing chlorophyll concentrations. This fertilization of coral reefs by dust increases photosynthesis which lowers the aqueous CO2 partial pressure relative to the overlying air. If this causes a reversal of the coral reef water to air CO2 gradient, then a coral reef will switch from a source to sink of CO2.

Here we present the first direct measurements of air-sea CO2 exchange measured by an eddy covariance tower exclusively over the fringing coral reefs in the Gulf of Eilat, Israel. These show a strong relationship to atmospheric dust load entrained from the surrounding hyper-arid deserts in Israel, Saudi Arabia and North Africa. The coral reefs became CO2 sinks most notably during episodes of moderate to high atmospheric dust load. We conclude that the coral reefs in the Gulf of Eilat are net sinks of atmospheric CO2 due to the deposition of dust and suggest that direct measurements of air – sea CO2 exchange are required over coral reefs in other locations impacted by dust to increase accuracy of marine and global carbon budgets.          

How to cite: McGowan, H., Lensky, N., Abir, S., Shaked, Y., and Wurgaft, E.: Dust fertilization: Measurements of CO2 sequestration by coral reefs in the Gulf of Eilat, Israel after atmospheric dust loading., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-990, https://doi.org/10.5194/egusphere-egu23-990, 2023.

10:49–10:51
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PICO2.3
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EGU23-6171
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ITS2.5/CL4.14
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On-site presentation
Jan-Berend Stuut, Catarina Guerreiro, Blanda Matzenbacher, and Michèlle Van der Does

Mineral dust plays an important role in the ocean’s carbon cycle through the input of nutrients

and metals which potentially fertilise phytoplankton, and by ballasting organic matter from the surface ocean to the sea floor. However, time series and records of open-ocean dust deposition fluxes are sparse. Here, we present a series of Saharan dust collected between 2015 and 2022 by dust-collecting buoys that are monitoring dust in the equatorial North Atlantic Ocean, as well as by moored sediment traps at the buoys' positions at ~21°N/21°W and ~11°N/23°W directly below the major dust Saharan-dust plume offshore northwest Africa. We present dust-flux data as well as particle-size distribution data, and make a comparison of the dust collected from the atmosphere at the ocean surface with the dust settling through the ocean and intercepted by the submarine sediment traps.
See: www.nioz.nl/dust

How to cite: Stuut, J.-B., Guerreiro, C., Matzenbacher, B., and Van der Does, M.: Monitoring present-day Saharan dust above and below the ocean surface, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6171, https://doi.org/10.5194/egusphere-egu23-6171, 2023.

10:51–10:53
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PICO2.4
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EGU23-1698
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ITS2.5/CL4.14
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On-site presentation
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Anton Lokshin, Daniel Palchan, and Avner Gross

Desert dust, volcanic ash and fire ash are the most abundant natural atmospheric particles. These particles considered as an important nutrient source that controls the long-term productivity of infertile terrestrial ecosystems, by replenishing soil nutrient stocks. However, currently we do not know whether atmospheric deposition can act as a direct, alternative source for nutrients. These are particles enriched with phosphorus (P) and other essential macro and micronutrients such as: K, Ca, Mg, Zn, Cu, Fe, Mn, Zn, and Mo. These nutrients are vital for plants and support their growth.

The current research shows that elevated CO2 (eCO2) in the atmosphere has positive and negative effects: On the positive side, increase of CO2 levels is predicted to result with an increase in photosynthesis leading to improved primary biomass production and thus enhancement of CO2 capture. On the other hand, at eCO2 plants show decreased concentrations of mineral nutrients in most of their organs, suggesting downregulation of the activity of the membrane transporters involved in root nutrient uptake; a decreased ability to assimilate nutrients from the roots system.

Preliminary results of recent studies had shown that plants can utilize P via foliar nutrient uptake mechanism, directly from dust that settled on the plant’s leaves. Since the efficiency of roots to assimilate nutrients is projected to decrease in future eCO2, foliar nutrient uptake may be a significant alternative pathway for plants to gain needed nutrients. In this work, we used atmospheric fertilization experiments – where we deposited dust directly on plant leaves – to show that atmospheric deposition boosts plant growth and fertilizes them through direct foliar nutrient uptake pathway. The foliar nutrient uptake mechanism was shown both in an ambient and eCO2 levels for the three primary atmospheric particles mentioned above. We saw that volcanic ash had significantly increased biomass at eCO2 compared with ambient CO2 levels. Our results demonstrate that foliar nutrient uptake is a significant mechanism at immediate timescales. Furthermore, that the direct alternative pathway of foliage nutrients assimilation has a potential to regulate carbon sink processes in a terrestrial ecosystem in a future climate.

How to cite: Lokshin, A., Palchan, D., and Gross, A.: Desert dust as a plant fertilizer in an ambient and elevated CO2, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1698, https://doi.org/10.5194/egusphere-egu23-1698, 2023.

10:53–10:55
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PICO2.5
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EGU23-986
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ITS2.5/CL4.14
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On-site presentation
John Gillies, Eden Furtak-Cole, George Nikolich, and Vic Etyemezian

The flux of wind-driven dust emissions from a susceptible area is determined by a complex relation between the driving force of the wind and the emissivity of the surface.  This relation is also modulated by the availability of sand-sized particles available for saltation, the roughness of the surface, and environmental conditions related to moisture, i.e., soil moisture and relative humidity.  The flux (F, µg m-2 s-1) of dust-sized particles from the surface scales non-linearly with the shear stress (τ, N m-2, or shear velocity u*, m s-1 [τ=ρu*2, where ρ is fluid density]) created by the wind flowing over the surface.  Shear stress or shear velocity are not easily measured without the use of multiple instruments to characterize the vertical gradient of wind speed; vertical flux of particles requires measurement of vertical gradient of particle concentration or application of the eddy covariance method.  Here we describe a simple but effective metric to track changes through time due to physical alteration of a surface or due to changes in the environment.  The metric is based on measuring mean hourly concentrations of particulate matter, e.g., PM10 (µg m-3) and mean hourly wind power density (WPD=0.5×ρ×A×wind speed3, W m-2), which quantifies the power in the moving air.  A is area, that we arbitrarily set at 1 m2.  These hourly values are individually summed over a period of interest (e.g., monthly) to calculate the ratio value of total PM10:total WPD.  These data can also be filtered to isolate the effect of the source area emissions on the receptor site, for example, by wind direction range.  Tracking this metric on a monthly basis across multiple years at the Oceano Dunes State Vehicular Recreation Area has allowed for the characterization of the change in dust (PM10) production due to dust control measures (i.e., hectares of dust control) being placed onto the dunes, as well as the changes to the dust emission system during a period in 2020 when the area was left relatively undisturbed due to restrictions due to COVID-19.  We suggest, and demonstrate, that this method can be broadly applied, is effective in quantifying change, and cost-effective.

How to cite: Gillies, J., Furtak-Cole, E., Nikolich, G., and Etyemezian, V.: A Simple Metric, Total PM10:Total Wind Power Density, to Quantify Changes in Dust Emission from Areas of Interest as a Function of Environmental Change, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-986, https://doi.org/10.5194/egusphere-egu23-986, 2023.

10:55–10:57
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PICO2.6
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EGU23-1097
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ITS2.5/CL4.14
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Virtual presentation
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Mingjin Tang, Huanhuan Zhang, and Rui Li

This work investigated seasonal variation of aerosol iron (Fe) solubility for coarse (>1 μm) and fine (<1 μm) particles at Xi’an, a megacity in northwestern China impacted by anthropogenic emission and desert dust. Total Fe concentrations were lowest in summer and similar in other seasons for coarse particles, while lowest in summer and highest in spring for fine particles; for comparison, dissolved Fe concentrations were higher in autumn and winter than spring and summer for coarse particles, while highest in winter and lowest in spring and summer for fine particles. Desert dust aerosol was always the major source of total Fe for both coarse and fine particles in all the four seasons, but it may not be the dominant source for dissolved Fe. Fe solubility was lowest in spring for both coarse and fine particles, and highest in winter for coarse particles and in autumn for fine particles. In general aerosol Fe solubility was found to be higher in air masses originating from local and nearby regions than those arriving from desert regions after long-distance transport. Compared to coarse particles, Fe solubility was similar for fine particles in spring but significantly higher in the other three seasons, and at a given aerosol pH range Fe solubility was always higher in fine particles. Aerosol Fe solubility was well correlated with relative abundance of aerosol acidic species, implying aerosol Fe solubility enhancement by acid processing; moreover, such correlations were better for coarse particles than fine particles in all the four seasons. Fe solubility was found to increase with relative humidity and acid acidity for both coarse and fine particles at Xi’an, underscoring the importance of aerosol liquid water and aerosol acidity in regulating Fe solubility via chemical processing.

How to cite: Tang, M., Zhang, H., and Li, R.: Seasonal variation of aerosol iron solubility in coarse and fine particles at an inland city in northwestern China, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1097, https://doi.org/10.5194/egusphere-egu23-1097, 2023.

10:57–10:59
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PICO2.7
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EGU23-9012
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ITS2.5/CL4.14
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On-site presentation
Jeffrey Munroe

The transport of mineral dust from arid lowlands to higher elevations has profound consequences for the geoecology of mountain ecosystems.  With expanding human populations and widespread disturbance due to land use, dust deposition rates and compositions are changing, presenting unique challenges for human and ecosystem health.  The American Southwest, a region that has experienced a massive increase in dust deposition rates in the past century, is no exception to this trend.  Understanding the flux and composition of dust can help identify where dust is coming from, and can inform management strategies for dust emitting landscapes.  As part of the DUST^2 Critical Zone Thematic Cluster, this project utilized a network of 18 passive dust traps in the southwestern US, 15 of which were deployed on high mountains summits and ridgelines.  The dust traps were emptied biannually between 2020 and 2022 to reveal spatial and temporal differences in dust compositions and depositional fluxes.  Results demonstrate that dust flux is higher in the summer compared to winter; at the 13 collectors with the most complete data, summer fluxes averaged 47.9 mg/m2/day whereas winter fluxes averaged 24.2 mg/m2/day.  Interannual variability is notable: for instance, some collectors received 2x as much dust in summer 2022 vs. 2021, whereas for others the pattern was reversed.  In contrast, all collectors received more dust during winter 2021-22 than in 2020-21.  Superimposed on these temporal differences is a spatial disparity in accumulation rates, with the highest values at the urban sampler in Salt Lake City and at sites immediately downwind.  In contrast, lower fluxes are common at high elevation sites in Nevada, particularly during the winter.  Overall, measured dust fluxes span a wide range from 5.3 to 255 mg/m2/day.   The grain size distribution, color, mineralogy, and geochemistry of dust also vary notably between sites, supporting the interpretation that much of the dust is sourced from the immediately surrounding lowlands.

How to cite: Munroe, J.: Seasonal and Interannual Variability in Dust Flux to High-Elevation Ecosystems in the Southwestern United States, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9012, https://doi.org/10.5194/egusphere-egu23-9012, 2023.

10:59–11:01
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PICO2.8
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EGU23-1839
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ITS2.5/CL4.14
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On-site presentation
|
Pinhas Alpert and Pavel Kishcha

Barkan investigated the synoptics of dust trajectories to Europe, Arctic, E. & W. Mediterranean, and the Atlantic Ocean (Barkan et al. 2004). His most recent research just before he passed away Barkan studied the outstanding Red Snow Event in Eastern Europe on March 2018. In April 2018 the European media published in great headlines a strange occurrence. Red colored snow fell in Bulgaria, Rumania, Ukraine and what was most interesting to the media, was reported in the mountains around Sochi the location of the former winter Olympic Games. Barkan showed that the phenomenon of the red snow in southwestern Europe is the result of a cold trough which penetrated from the north toward the central Mediterranean and Saharan Africa, together with its movement eastward. Consequently, a strong southwesterly flow formed along the eastern flank of the trough. This flow transported a large amount of red Saharan dust which upon mixing with the snowfall in the area painted the snow red (Barkan and Alpert, 2020). In this case the trough developed further east which is not a common occurrence. This has caused heavy dust storms in central Sahara near the most ample dust sources (Barkan, Kutiel and Alpert, 2004). So, it will be shown that the transported dust reached the area together with snow flakes and probably painted it in red or brown.

Another interesting study by late Barkan is on the difference in the synoptic situation between years with a large amount of dust and years with relatively small amount, in the Sahara- this was examined for 1979-1992 (Barkan and Alpert, 2008). For every month the dustiest and the non-dustiest year were chosen and the average of the three months in the season of these years was examined. The examination was made for the atmospheric variables: wind flow, wind velocity, geopotential height and temperature, at the 700 hPa level. The data used were the daily aerosol index from the TOMS satellite born instrument and the daily NCEP/NCAR reanalysis data of the variables mentioned above between the years 1979-1992.

 Other interesting studies will be reviewed including, a novel climatic index for the total Saharan dust being discovered as the Sun insolation; a unique case-study of near-circular Saharan dust transport over the Atlantic Ocean; and dust as a potential tracer for the flow over different topographical shapes employing MODIS-Terra observations.

References:

  • Barkan, P. Kishcha, H. Kutiel, and P. Alpert, "The Synoptics of Dust Intrusion Days from the African Continent into the Atlantic Ocean", J. Geophys. Res., Vol. 109, No. D8, D08201=2010.1029/2003JD004416=20, 2004.
  • Barkan, H. Kutiel and P. Alpert, "Climatology of dust sources over the North African region, based on TOMS data", Indoor-Built Environ., Vol. 13, 407-419, 2004.
  • Barkan, P. Alpert, H. Kutiel, and P. Kishcha,"The Synoptics of dust transportation days from Africa toward Italy and Central Europe", J. Geophy. Res., 110, doi:10.1029/2003 JD004416, 2005.
  • Alpert, J. Barkan, and P. Kishcha, "A potential climatic index for total Saharan dust: the Sun insolation", J Geophy. Res., 111, D01103, doi:10.1029/2005JD006105, 2006.

How to cite: Alpert, P. and Kishcha, P.: Saharan Dust Sources and their World Trajectories - A review in memory of J. Barkan (deceased 27 May 2020), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1839, https://doi.org/10.5194/egusphere-egu23-1839, 2023.

11:01–11:03
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PICO2.9
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EGU23-2699
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ITS2.5/CL4.14
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On-site presentation
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Diana Francis, Ricardo Fonseca, Narendra Nelli, Deniz Bozkurt, Juan Cuesta, and Emmanuel Bosc

Large amounts of dust in the air can disrupt daily activities and pose a threat to human health. In May 2022, consecutive major dust storms occurred over the Middle East resulting in severe environmental, social and health impacts. In this study, we investigate the exceptional factors driving these storms and the effects of the dust clouds. Using a combination of satellite, in-situ and reanalysis datasets, we identify the atmospheric triggers for the occurrence of these severe dust storms, characterize their three-dimensional structure and evaluate the dust radiative impact. The dust emission was promoted by density currents emanating from deep convection over Turkey. The convective systems were triggered by cut-off lows from mid-latitudes fed by moisture from African atmospheric rivers. Data from the Infrared Atmospheric Sounding Interferometer (IASI) showed that the dust clouds were transported southward at 4 km in altitudes but sunk to ground levels when they reached the southern Arabian Peninsula due to strong subsidence. At a station in coastal UAE, the dust caused a 350 W m−2 drop in the surface downward shortwave flux and a 70 W m−2 increase in the longwave one during the dust episodes. This contributed to a 9 °C increase in nighttime temperatures which exacerbated the effects of the heat for the population. The newly highlighted mechanism for dust emission in the Middle East, in which a cut-off low interacts with an atmospheric river, as well as direct observations of the dust impact on the radiative budget can contribute to reducing associated uncertainties in climate models.

How to cite: Francis, D., Fonseca, R., Nelli, N., Bozkurt, D., Cuesta, J., and Bosc, E.: On the Middle East's severe dust storms in spring 2022: Triggers and impacts, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2699, https://doi.org/10.5194/egusphere-egu23-2699, 2023.

11:03–11:05
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PICO2.10
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EGU23-13450
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ITS2.5/CL4.14
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ECS
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On-site presentation
Feifei Mu, Eduardo Weide Luiz, and Stephanie Fiedler

The Gobi and the Taklamakan Desert are the two main dust source regions in East Asia. Extra-tropical cyclones are known as atmospheric driver for severe dust outbreaks in East Asia. Although previous studies show that dust storm frequency in Northern China have decreased associated with a decrease in near-surface wind speed, a severe dust storm occurred in mid-March 2021. This exceptional dust storm was driven by a Mongolian extra-tropical cyclone and had adverse socio-economic and health impacts. The aim of our study is to investigate the atmospheric dynamics, dust-aerosol contributions from the Gobi Desert and the Taklamakan Desert, as well as dust emission mechanisms involved in the event. We use ground-based observations from Chinese observational networks, satellite images from MODIS, data from ERA5 re-analysis, CAMS forecasts, and MERRA-2 re-analysis.

The passage of the Mongolian cyclone first induced high dust-emitting winds along its cold front. The maximum wind speeds at 10m a.g.l. over the Gobi Desert exceeded the 99th percentile of the 30-year climatology (1992-2021) for March by around 6 ms−1 . The dust aerosols were emitted by these exceptionally strong near-surface winds and transported southeastwards along with the passage of the frontal system of the Mongolian cyclone from the afternoon of 14th March to the morning of 15th March 2021. Hence, high atmospheric PM10 concentrations were first recorded in Northern China on 15th March. As a consequence of the associated poor air quality caused by the high PM10 concentrations, 19 out of 218 stations recorded the lowest atmospheric visibility for March since the past 30 years.

The passage of the Mongolian cyclone then led to a cold air intrusion into the Taklamakan Desert from the afternoon of the 15th onward, which was a few hours after the dust emissions in the Gobi Desert. The cold air intrusion with the associated near-surface temperature inversion was favourable for the formation of Nocturnal Low-Level Jets (NLLJs), which are known as an important mechanism for dust emissions in the dust source regions (e.g., East Asia and North Africa). By comparing the NLLJs from radiosonde observations and an automated detection algorithm applied to ERA5, stronger NLLJs were seen in the Taklamakan Desert in the mornings of 16, 17, and 18 March. The NLLJs breakdown during the morning hours led to sufficiently strong dust-emitting winds in this desert. Consequently, dust emissions are simulated in the mornings of 16, 17, and 18 March 2021 by both CAMS forecasts and MERRA-2 re-analysis. The impacts of the dust aerosols from the Taklamakan Desert were, however, limited to the west of China, supported by spatio-temporal distributions of station observations of the atmospheric PM10 concentrations and visibility.

How to cite: Mu, F., Luiz, E. W., and Fiedler, S.: On the severe East Asian dust outbreak in March 2021: from atmospheric dynamics to air quality impact, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13450, https://doi.org/10.5194/egusphere-egu23-13450, 2023.

Dust emission, transport, and deposition processes
11:05–11:07
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PICO2.11
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EGU23-3512
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ITS2.5/CL4.14
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ECS
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Virtual presentation
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Narendra Nelli, Diana Francis, Mamadou Sow, Emmanuel Bosc, and Gilles Bergametti

The Arabian Peninsula is among the major dust sources on Earth. Here, dust storms occur frequently as a result of the action of surface winds on desert surface such as the Empty Quarter Desert located in southern Arabian Peninsula. Despite being a frequent occurrence, no direct measurement of dust emission in this region existed to date. In summer 2022, the WInd-blown Sand Experiment (WISE) kicked off in the Empty Quarter area located in southern United Arab Emirates (UAE). The aim of the experiment is to quantify dust emission from this major dust source through direct observations. A full set of instrumentation is being operated to study saltation, winds, temperature, humidity, radiative fluxes, physical and optical properties of dust aerosols, atmospheric electric field, and soil properties. In this presentation, we describe the instrumentation being used in WISE UAE and we show some preliminary results during different weather regimes such as strong wind erosion, local convection, dense radiation fog and land-sea breeze. The analysis of atmospheric electric field data suggests the presence of relatively higher electric field at the onset of sea breeze occurrence and wind erosion events. The detailed investigation on relative humidity, frictional velocity, dust particle size distribution impact on the electric field will be presented. WISE is a first-of-its-kind experiment in the region and it aims ultimately at improving dust parametrizations in numerical models. We hope that this presentation at the EGU can trigger collaborations in this direction.

How to cite: Nelli, N., Francis, D., Sow, M., Bosc, E., and Bergametti, G.: The WInd-blown Sand Experiment (WISE) – UAE: Introduction and first results, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3512, https://doi.org/10.5194/egusphere-egu23-3512, 2023.

11:07–11:09
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PICO2.12
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EGU23-8286
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ITS2.5/CL4.14
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On-site presentation
Martina Klose and Carlos Pérez García-Pando and the J-WADI Team

Knowledge about the particle-size distribution and mineralogical composition of mineral dust at emission are fundamental to advance our understanding and quantification of dust climate effects, yet comprehensive measurements are still largely lacking, especially of super-coarse and giant particles and particle composition. Here, we introduce the Jordan Wind erosion And Dust Investigation (J-WADI), an intensive field measurement campaign conducted in September 2022 north of Wadi Rum in Jordan. The aim of J-WADI is to improve our fundamental understanding of the emission of mineral dust, in particular its full-range size distribution (from fine to giant dust particles) and mineralogical composition. For this purpose, in-situ and ground-based remote sensing instrumentation was installed to measure aerosol properties, e.g. particle numbers and sizes up to about 100 μm, optical  properties, and aerosol distributions; collect soil and aerosol samples for laboratory analysis and experimentation; and to measure meteorological parameters including wind cross sections at high temporal and spatial resolutions and near-surface turbulence. In this contribution, we will present an overview of the J-WADI measurement setup and campaign conditions, together with preliminary results of observed dust events. In the future, J-WADI measurements will serve as a basis to investigate, e.g., (a) the mechanisms leading to the emission and continued suspension of super-coarse and giant dust particles and the possible variability of the emitted dust particle-size distribution; (b) the size-resolved mineralogy of dust at emission, its relationship with the parent soil, and spectroscopic measurement, and (c) dust-radiation and dust-cloud interactions.

How to cite: Klose, M. and Pérez García-Pando, C. and the J-WADI Team: The Jordan Wind erosion And Dust Investigation (J-WADI), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8286, https://doi.org/10.5194/egusphere-egu23-8286, 2023.

11:09–11:11
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PICO2.13
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EGU23-3887
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ITS2.5/CL4.14
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On-site presentation
Paola Formenti

While the most extensive and active sources of mineral dust are found at mid-latitudes (Sahara, East Asia and the Arabic peninsula), source areas at high latitudes both in northern and the southern Hemispheres, are gaining attention because of their distinct characteristics and impacts at the appropriate regional and semi-hemispheric scales.

Southern Africa is estimated to account for approximately 5% of the global annual emissions of mineral dust and the long-range transport of dust emitted from these regions are shown to head towards the South Atlantic, the southern Oceans, and across the subcontinent by both observations and modelling.

In particular, hundreds distinct point sources have been identified in Namibia, including the topographical lows of the Etosha pan alluvial basin, the dry lands (Kalahari Desert, gravel plains bordering the Namib Deserts), but mostly the numerous ephemeral riverbeds, pans, wetlands and possibly mines along the coastline. By deposition, this windblown dust could impact to the productivity of the waters offshore, but also the formation and the chemical composition of the fog and low marine clouds. Through the fog, the dust emitted has the potential of redistributing nutrients not only to the marine but also to the continental ecosystems. Likewise, the strong and almost omnipresent southerly trade winds driven by the temperature contrast between the cold Benguela current and warm and dry continental desert air masses also provide an opportunity to transport sediment influenced by the nutrient rich aerosols of the ocean further onto land to nourish the nearshore ecosystems. To date, the majority of dust emissions observations from this region have relied heavily on the improved ability of satellite platforms to optically isolate dust aerosols over the ocean surface and despite the consistent high winds from the south, have excluded the potential for dust emission transport processes towards the interior.

This presentation illustrates the new results of recent coordinated research exploring the emissions, the transport, and properties of net transported mineral dust from Namibia sources. These new results rely on model simulations at different spatial resolution, on the analysis of local and regional wind regimes, on field observations, and on laboratory-based experiments on airborne dust generated from natural soils. Our results demonstrate that the frequency of emission might be higher than expected by only easterly berg winds. We also suggest that the Namibian dust may be transported to Antartica and that its processing by marine biogenic emissions could be responsible for the seasonal increase in the dust iron solubility observed in the Austral fall.

How to cite: Formenti, P.: Mineral dust in Namibia: new research on emissions, transport and properties, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3887, https://doi.org/10.5194/egusphere-egu23-3887, 2023.

11:11–12:30
Lunch break
Chairpersons: Adolfo Gonzalez Romero, Jan-Berend Stuut
14:00–14:02
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PICO2.1
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EGU23-1682
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ITS2.5/CL4.14
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On-site presentation
Georgiy Stenchikov, Suleiman Mostamandi, Ilia Shevchenko, and Alex Ukhov

In dust source regions, such as the Middle East, dust is a major environmental factor affecting climate, air quality, and human health. Dust also hampers solar energy harvesting by weakening downward solar flux and depositing on optically active surfaces of solar energy devices. In this study, we combine fine-resolution WRF-Chem simulations with size-segregated measurements of dust deposition to quantify the contribution of coarse (2.5 um < r < 10 um) and giant (10 um <r < 100 um) dust particles in aerosols radiative forcing and deposition rates. Most up-to-date models do not represent the particles with r > 10 um. The absence of large particles in the models does not significantly affect the radiative fluxes, as their contribution to AOD is relatively small, but they comprise the most dust-deposited mass. We found that dust deposition rates calculated in WRF-Chem and reanalysis products are 2-3 times smaller than the observed. However, the deposition rate of particulate matter with a diameter smaller than 10 um (PM10) is in good agreement between the models and observations. In the Middle East, fine dust particles are predominantly responsible for the significant reduction (> 5 %) of the downward solar flux hampering solar energy production. Still, dust-deposited mass, primarily associated with coarse particles, causes about a 2% loss of PV panel efficiency daily due to soiling. As was suggested previously, WRF-Chem, like many other models, tends to overestimate the atmospheric concentration of fine (r < 2.5 um) dust particles and underestimate the concentration of coarse particles. As seen from the comparison of the size distribution of deposited dust in simulations and observations, the latter is caused not as much by too fast deposition of large particles but due to underestimating their emission in the models.

 

How to cite: Stenchikov, G., Mostamandi, S., Shevchenko, I., and Ukhov, A.: The effects of coarse dust in the models and observations in the dust source regions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1682, https://doi.org/10.5194/egusphere-egu23-1682, 2023.

14:02–14:04
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PICO2.2
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EGU23-2075
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ITS2.5/CL4.14
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ECS
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On-site presentation
Mega Octaviani, Rong Tian, Gholamali Hoshyaripour, Roland Rhunke, Oliver Kirner, Christian Scharun, and Martina Klose

Mineral dust is known to play an important role in weather and climate through its interactions with clouds, radiation, and nutrient cycles. Dust aerosols are emitted as water-insoluble particles which experience chemical aging (conversion to water-soluble mixtures) through the accumulation of soluble materials like sulfate and nitrate. This aging process affects the chemical composition and size distribution of the dust particles as well as their optical properties. Within the context of the dust aging mechanism, different approaches are applied in atmospheric models regarding the representation of the aerosol size distribution (bin or modal representation) and the number of microphysical processes included. The ICOsahedral Nonhydrostatic model with Aerosols and Reactive Trace gases (ICON-ART) and the new AERODYN aerosol dynamic module consider the nucleation and condensation of sulfuric acid gas, coagulation and aging of aerosols, size-dependent wet and dry deposition, and sedimentation. The aerosol size distribution in the model is represented by eight unimodal lognormal distributions (also called modes) with constant width. These modes describe four different size groups, two in the submicron range (typically <1 μm) and two in the coarse range (>1 μm), and two hygroscopic classes in a homogeneous or core-shell mixture (insoluble, soluble, and mixed). This approach is a common technique in global aerosol simulations yet implies simplifications of complex aerosol size distributions. It may cause uncertainties in simulating the aging processes of dust aerosols and inaccuracies in representing their observed size distributions. We conduct global simulations using ICON-ART to analyze the sensitivity of simulated dust to parameters representing properties of the modes, namely initial geometric median diameter and standard deviations, and threshold diameters for shifting between modes. We also aim to explore the impact of the mineral dust aging process on the range of dust direct radiative feedback.  This study will show the importance of aerosol size distribution parameter combinations for representing the chemical aging of mineral dust and its climate impacts.

How to cite: Octaviani, M., Tian, R., Hoshyaripour, G., Rhunke, R., Kirner, O., Scharun, C., and Klose, M.: Exploring the sensitivity of mineral dust aging to parameters of aerosol size distribution in the ICON-ART model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2075, https://doi.org/10.5194/egusphere-egu23-2075, 2023.

14:04–14:06
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PICO2.3
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EGU23-9364
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ITS2.5/CL4.14
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On-site presentation
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Eleni Drakaki, Sotirios Mallios, Vassilis Amiridis, Alexandra Tsekeri, Demetri Bouris, and Petros Katsafados

One of the deficiencies of atmospheric dust models is that they struggle to accurately reproduce the transport of coarse and giant dust particles, according to observational evidence. Among the reasons behind that model incapacity that have been proposed in the literature, is the issue of numerical diffusion inside the advection codes of the models. In this study, we examine the importance of that issue in the WRF-L model. To do so, we update the default numerical scheme (UPWIND) which is used for the vertical advection of dust due to gravitational settling. The diffusive UPWIND scheme is replaced with a non-diffusive one, named UNO3 (third-order Upstream Non-Oscillatory scheme). To test the code performance, we perform simulations reproducing the 2D transport of a dust plume which is released at 4 km height above Cabo Verde towards Barbados. The model is initialized on 13/06/2014 at 12 UTC (which coincides with the day of the SALTRACE flight above Cabo Verde) using meteorological conditions of radiosonde from Tenerife airport and wind profile based on ECMWF model climatology. The results suggest that, in the UNO3 simulation, dust particles with a diameter 26 μm can be transported more than 500 km longer than in the BASE simulation and the dust in the atmosphere can be 10% more in the UNO3 simulation compared to the BASE simulation. In future studies, the UNO3 scheme will be tested in other aerosol types also (e.g. volcanic ash, smoke from fires).

Acknowledgements: Authors acknowledge support by the Hellenic Foundation for Research and Innovation (H.F.R.I.) under the “2nd Call for H.F.R.I. Research Projects to support Post-Doctoral Researchers” (Project Acronym: StratoFIRE, Project number:  3995) and the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Project Acronym: D-TECT, Grant Agreement: 725698).

How to cite: Drakaki, E., Mallios, S., Amiridis, V., Tsekeri, A., Bouris, D., and Katsafados, P.: Numerical diffusion on vertical advection due to gravitational settling in WRF: 2D simulations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9364, https://doi.org/10.5194/egusphere-egu23-9364, 2023.

14:06–14:08
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PICO2.4
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EGU23-11139
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ITS2.5/CL4.14
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Virtual presentation
Stephanie Fiedler, Angela Benedetti, Vassilis Amiridis, Carlos Pérez García-Pando, Jan-Berend Stuut, and Jan Griesfeller and the DOMOS team

The ESA-funded “4D-Atlantic Dust-Ocean Modelling & Observing Study” (DOMOS) kicked off in September 2021, with the overarching objective to advance our fundamental understanding on the complex atmospheric dust-ocean interactions in the Atlantic Ocean in the context of climate change. The project has an innovative approach with the integrated use of modelling, EO-based products and in-situ datasets. 

DOMOS has created and validated a novel EO-based product of dust deposition fluxes against in-situ observations and previously existing datasets of dust deposition. Specifically, the project has developed a product of pure-dust deposition fluxes across the Atlantic Ocean for 2007-2020, based on the exploitation of (1) the CALIPSO-based ESA-LIVAS pure-dust database, (2) the MODIS-MIDAS and Metop-IASI MAPIR/IMARS/LMD/ULB atmospheric pure-dust products, and (3) ERA5 U/V wind components. Moreover, DOMOS has provided a validation of the dust deposition field from the CAMS reanalysis and has performed assimilation tests of IASI and Aeolus aerosol products with the goal of providing a better description of the dust aerosol transport over the Tropical Atlantic. The DOMOS products also contribute to an improved representation of the physical and chemical characteristics of dust deposition over the ocean, which is crucial to interpret past changes in the atmosphere and ocean and to better understand the possible future development. This includes a better understanding and quantification of the contributions from natural and anthropogenic dust to the deposition of soluble iron, compared to depositions associated with biomass burning and anthropogenic aerosols. This has been achieved through new experiments with the climate model EC-Earth3-Iron. 

Finally, DOMOS foresees providing a scientific roadmap to highlight the findings of the project and identify possible gaps in the modeling and the observing approaches of atmospheric dust-ocean interactions. In this presentation, we give an overview of the project and highlight the most important results from the DOMOS dust deposition products and model experiments.

More information can be found at https://www.ecmwf.int/en/research/projects/domos



How to cite: Fiedler, S., Benedetti, A., Amiridis, V., Pérez García-Pando, C., Stuut, J.-B., and Griesfeller, J. and the DOMOS team: 4D-Atlantic Dust-Ocean Modelling & Observing Study (DOMOS), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11139, https://doi.org/10.5194/egusphere-egu23-11139, 2023.

14:08–14:10
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PICO2.5
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EGU23-12893
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ITS2.5/CL4.14
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ECS
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On-site presentation
Stephan Krätschmer, Alexandre Cauquoin, Gerrit Lohmann, and Martin Werner

In this study, we perform simulations with the ECHAM6.3-HAM2.3 aerosol-climate model with two prescribed different reconstructions of sea surface temperatures (SST) for the Last Glacial Maximum (LGM) as boundary conditions. While one of the datasets suggests a global cooling of 4.1°C (GLOMAP; Paul et al., 2021), the other suggests a much stronger cooling of 6.1°C (Tierney et al., 2020) during the LGM compared to pre-industrial climate conditions. The comparison of our simulation results to LGM land surface temperatures reconstructed based on noble gas concentrations in groundwater (Seltzer et al., 2021) does not indicate clearly which SST dataset results in a better agreement between our simulation results and observational data. For further assessment, we also compare for both SST datasets the simulated mineral dust deposition in the Southern Hemisphere to observational data (Kohfeld et al., 2013). While GLOMAP SSTs result in a strong overrepresentation of Australian mineral dust deposited over Antarctica, the SSTs provided by Tierney et al. (2020) indicate Patagonia to be the dominant dust source during the LGM in terms of deposition over Antarctica with minor contributions from Australia and South Africa. Such dominant Patagonian dust source is in agreement with geochemical data from East Antarctic ice cores (Basile et al., 1997; Delmonte et al., 2008). The differences in individual source contributions can be traced back on the one hand to changes in the meteorological conditions in the source regions, including vegetation, wind speed and precipitation. On the other hand, both SST datasets result in different characteristic high- and low-pressure patterns in the Southern Hemisphere, which allow for a more efficient transport of Australian dust for the warmer GLOMAP SSTs and Patagonian dust for the colder Tierney et al. SSTs to Antarctica.

How to cite: Krätschmer, S., Cauquoin, A., Lohmann, G., and Werner, M.: Investigating the Effects of Prescribing Different Sea Surface Temperature Reconstructions on the Mineral Dust Cycle During the Last Glacial Maximum, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12893, https://doi.org/10.5194/egusphere-egu23-12893, 2023.

Source to sink studies of present and past dust
14:10–14:12
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PICO2.6
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EGU23-1303
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ITS2.5/CL4.14
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On-site presentation
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Olivier Evrard, Octave Bryskere, Charlotte Skonieczny, Anthony Foucher, Rémi Bizeul, Thomas Chalaux Clergue, Jean-Sébastien Barbier, Jean-Eudes Petit, José A. Corcho‑Alvarado, Stefan Röllin, Pierre-Alexis Chaboche, and Germán Orizaola

Air masses loaded with mineral dust and originating from the Sahara arrive frequently in Europe, which has multiple impacts on global and regional cycles. However, the occurrence of these processes may further accelerate in the future in response to climate change, and more knowledge is therefore required on the characteristics of the particles transported during these massive dust transport and deposition episodes. Furthermore, questions arise regarding the content of this dust in radionuclides, in relationship with the atmospheric nuclear bomb testing conducted around the world between the 1950s and the 1970s in general, and those tests conducted by France in the Sahara in the early 1960s in particular.

The Saharan dust episode that took place from 13th to 16th March 2022 led to the occurrence of dense dust deposition across multiple European countries, which raised concerns among the population regarding the potential radioactivity content of this dust. To address this question with a representative sample set, a participative science campaign to collect dust across Europe was launched on Twitter on 17th March 2022. Thanks to this initiative, 110 dust samples could be collected along a transect from Southern Spain to Austria.

This unique sample bank was regrouped at University Paris-Saclay, France, to conduct a set of physico-chemical analyses on a selection or on the totality of these dust samples including particle size, colourimetry, mineralogy and fallout radionuclides.

Backward trajectories of air masses that have led to these deposits were calculated, and this analysis confirm their potential origin from Algeria. 137Cs was detected in all dust samples, with variable activity concentrations. A strong relationship was found between the particle size of the analysed particles and the 137Cs activity concentrations, which is consistent with the literature on this topic. Particle size was found to decrease with increasing distances from the source. The colour and mineralogy analyses demonstrated that the dust collected in Austria showed different properties than those samples collected in Spain, France, Luxembourg and Germany, which likely indicates that this material did not fully consist of Saharan dust deposited during the March 2022 episode. Accordingly, the following interpretations did not take the properties of Austrian dust into account.

The mineralogical analyses confirmed the potential origin of the dust from the Maghreb region, including a vast area in Southern Morocco and Southern Algeria. In contrast, the analysis of plutonium isotopic ratios (240Pu/239Pu) and 137Cs/239+240Pu activity ratios, which provide diagnosis tools to investigate the source of artificial radionuclides, in a selection of dust samples collected between Southern Spain and Luxembourg showed that the dust signature was consistent with that of the global fallout largely dominated by the nuclear tests conducted by the USA and the Soviet Union. The 137Cs contained in the dust transported and deposited during this episode was therefore very likely not associated with the French nuclear tests conducted in the early 1960s in Sahara.

In the future, elemental geochemistry analyses will provide additional information on their source provenance. All results will also be published in open-access database and disseminated to the public.

How to cite: Evrard, O., Bryskere, O., Skonieczny, C., Foucher, A., Bizeul, R., Chalaux Clergue, T., Barbier, J.-S., Petit, J.-E., Corcho‑Alvarado, J. A., Röllin, S., Chaboche, P.-A., and Orizaola, G.: Was the 137Cs contained in Saharan dust deposited across Europe in March 2022 emitted by French nuclear tests in Algeria?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1303, https://doi.org/10.5194/egusphere-egu23-1303, 2023.

14:12–14:14
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PICO2.7
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EGU23-15856
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ITS2.5/CL4.14
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Virtual presentation
Olena Tomeniuk and Andriy Bogucki

The Pleistocene periglacial loess-palaeosol series covers about 70% of the territory of Ukraine. The loess-palaeosol mantle of the Volhynian and Podolian uplands, which are the reference region of our many years of research, is even larger, almost continuous in area. Loess is also widespread on the surfaces of the high river terraces in the Forecarpathians.

Dozens of key sections of the Quaternary deposits were studied in Volhyn-Podillia and Forecarpathians using the most modern analytical methods. Among them are sections of Novovolynsk, Boyanychi, Torchyn, Horokhiv, Korshiv, Dubno, Rivne, Basiv Kut, Zdolbuniv (Volhynian upland), Velykyi Hlybochok, Proniatyn, Ihrovytsia, Ternopil, Malyi Khodachkiv, Pidvolochysk, Volochysk, Krasnosilka, Sharovechka, Yarmolyntsi, Letychiv, Vanzhuliv (Podolian upland), Halych, Kolodiiv, Torhanovychi (transition zone to the Forecarpathian upland), etc. P. Tutkovskyi developed an aeolian hypothesis of loess origin (1899) based on the materials of the study of loess deposits in the west of Ukraine, and W. Łoziński introduced the concept of "periglacial" into scientific circulation in 1909.

In the loess-palaeosol series of the west of Ukraine, a number of well-known Palaeolithic sites were discovered and studied, namely the Lower Palaeolithic site of Korolevo, the Middle Palaeolithic sites of Yezupil I, Yezupil II, Mariampil I, Mariampil V, Velykyi Hlybochok I, Proniatyn, Ihrovytsia, Buhliv V, Upper Palaeolithic sites of Vanzhuliv (Zamchysko), Kulychivka, Lypa and many others.

The significance of the study of the periglacial loess-palaeosol sequences for the study of the Palaeolithic of Ukraine is as follows.

  • Solving the problems of stratification of Palaeolithic cultural horizons, substantiation of their age. The results of absolute dating of the Quaternary deposits are important in this context.
  • Solving the issues of preservation of cultural horizons and their redeposition by diluvial-solifluction processes. Palaeocryogenic analysis, widely used in the study of the loess-palaeosol series of the Pleistocene, is very promising here.
  • Correlation of Palaeolithic cultural horizons with stratigraphic ones.
  • The results of the study of loess-palaeosol sequences make it possible to more thoroughly understand the living conditions of ancient people, to study the ways of their migration and adaptations to climate, landscape and ecosystem change.

 

Acknowledgements

This study was supported by the project of the National Research Foundation of Ukraine, grant number 2020.02/0165.

How to cite: Tomeniuk, O. and Bogucki, A.: The significance of the Pleistocene periglacial loess-palaeosol sequences study for the knowledge of the Palaeolithic of Ukraine, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15856, https://doi.org/10.5194/egusphere-egu23-15856, 2023.

14:14–14:16
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PICO2.8
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EGU23-16284
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ITS2.5/CL4.14
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ECS
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On-site presentation
Niels Meijer and Bas van der Meulen

Loess deposits are widespread in the Quaternary, but relatively rare in older geological records. This disparity is commonly linked to the unique climate conditions of the Quaternary, but those cannot fully explain the scarcity of loess in older records. Instead, we propose that the poor preservation of loess due to its windblown nature also plays an essential role. To test this hypothesis, we assess the preservation potential of loess by quantifying its modern-day distribution in active sedimentary basins. This analysis shows that on the global scale only 20% of loess occurs in basins of which the majority is in a foreland setting, possibly because of the proximity to silt-producing mountains and rain shadow aridity. The other 80% is ultimately either eroded or reworked and therefore poorly preserved in the long term. This conclusion implies that loess deposits may have been more common in pre-Quaternary periods, despite being less abundant in the geological record.

How to cite: Meijer, N. and van der Meulen, B.: Loss of loess in the geological record due to poor preservation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16284, https://doi.org/10.5194/egusphere-egu23-16284, 2023.

14:16–14:18
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PICO2.9
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EGU23-14601
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ITS2.5/CL4.14
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ECS
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On-site presentation
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Katja Bohm, Anu Kaakinen, Thomas Stevens, Yann Lahaye, and Hui Tang

Understanding atmospheric circulation in the geologic past under warm climates is crucial for projection of future climate scenarios. One of the few ways to unravel past atmospheric circulation is to study aeolian mineral dust deposits that link the geosphere to the atmosphere. Atmospheric mineral dust both affects and is affected by climate changes, but its role in the Earth system is poorly constrained. The aeolian dust deposits on the Chinese Loess Plateau (CLP) and adjacent regions provide an exceptionally vast amount of material to study Central-East Asian atmosphere and environments since the Eocene. Moreover, provenance research on these deposits is the key to reconstruct past atmospheric circulation and to understand the evolution of regional aridity and dustiness, which are closely linked with global climate.

In this study, we investigate the Paleogene to Neogene dust deposits in and near the CLP at latitude ~40°N. We present multiproxy provenance data from the Paleogene Ulantatal dust sequence in Inner Mongolia, China, approx. 400 km northwest of the central CLP, and from the Neogene Baode Red Clay in the northern CLP. As the first comprehensive study using detrital rutile trace element geochemistry combined with detrital zircon U-Pb ages in the CLP region, our data reveal both longer- and shorter-term pre-Quaternary provenance trends in the area. The Ulantatal dust sequence shows constant dust provenance during c. 34–29 Ma, including through the Eocene-Oligocene global climate transition. Strikingly, this provenance signal, which suggests dominant northerly to northwesterly dust transport, is very similar to that of the Neogene Baode Red Clay, reinforcing suggestions that a pre-Quaternary East Asian winter monsoon (EAWM) regime existed in the region for at least 30+ million years despite changes in paleogeography. However, the late Miocene (c. 8–7 Ma) extension of dust deposition to the eastern CLP was coupled with an increasing dominance of Northern Tibetan Plateau (NTP) provenance signal in Baode, implying an at least 1–2 Myr period of enhanced dust production in the NTP, a dominance of westerly winds over the EAWM, and/or contribution of silt-sized material by a proto-Yellow River. After, in the latest Miocene and in the Pliocene the EAWM again dominated the dust transport to the northern CLP. While the long-term temporal variability of dust provenance is small through Paleo-Neogene in the northern CLP latitudes, spatial variability of Paleogene dust in the CLP region is similar to that of the Neogene Red Clay and Quaternary loess in the area: the Ulantatal dust provenance differs from the Paleogene southwestern CLP dust provenance. This spatial variability confirms previous conclusions that local sources define most of the dust provenance signals in the silt fraction, complicating the interpretation of possible global climate forcing in the Central-East Asian dust cycle, and reinforcing the need for multiproxy provenance analysis of loess dust.

How to cite: Bohm, K., Kaakinen, A., Stevens, T., Lahaye, Y., and Tang, H.: Paleogene to Neogene aeolian dust provenance in the Chinese Loess Plateau region, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14601, https://doi.org/10.5194/egusphere-egu23-14601, 2023.

14:18–14:20
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PICO2.10
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EGU23-11692
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ITS2.5/CL4.14
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On-site presentation
Onn Crouvi, Ohad Shalom, Yehouda Enzel, and Daniel Rosenfeld

Current dust storms, originating from afar, are common in Israel and the eastern Mediterranean, and thus most dust sources are considered to be distal. However, recent studies suggest that the latest Quaternary loess accreted in the Northern Negev can also serve as a proximal source of dust. These sources were mostly neglected in past discussions as contributors of dust. Here, we demonstrate that such proximal dust sources, mostly the Negev loess, currently contribute relatively large amounts of recycled dust to the regional dust cycle. We conducted a sampling campaign of deposited dust during individual dust storms and identified high content of coarse silt grains and quartzo-feldspathic minerals within and adjacent to the Negev loess that gradually decreases toward the north. These grains, characteristics of the Negev loess, indicate a short transport distance. In addition, our data reveal that local wind speed is the limiting factor for emitting proximal dust, regardless of the synoptic system. We determined that proximal sources in Israel emit dust during either local events or as a part of regional dust storms originating from afar. We evaluate the minimal contribution of this proximal dust to the total mass of deposited dust as 58–74%, 54–70%, 52–64%, and 26–34% for the northern Negev, central Negev, central mountainous region, and northern Israel, respectively. These estimates indicate that at the desert fringe, both proximal and distal sources of dust should be considered when inferring dust sources from dust geochemistry that can sometimes be similar due to the long dust history.

How to cite: Crouvi, O., Shalom, O., Enzel, Y., and Rosenfeld, D.: Locally recycled late Pleistocene loess feeds modern dust storms at the desert margins of the eastern Mediterranean, Israel, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11692, https://doi.org/10.5194/egusphere-egu23-11692, 2023.

14:20–14:22
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PICO2.11
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EGU23-17138
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ITS2.5/CL4.14
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On-site presentation
Gordon Bromley, Colin Bunce, Tom Stevens, Marta Cabello, Martin Nauton, and Kathryn Fitzsimmons

The west coast of Ireland is currently one of the wettest environments in Europe, with year-round precipitation, high humidity, and minimal thermal seasonality maintained by a strongly North Atlantic climate. While such conditions are not conducive to dust entrainment, transport, and deposition today, we report geologic evidence from the limestone Burren uplands for a period of sustained aeolian sedimentation during the last glacial termination. Contrasting with Ireland’s till- and glacial-outwash-dominated lowlands, the Burren’s extant sediment cover comprises a homogenous mineral silt preserved in lee-side zones and karst depressions, the outer reaches of caves, and amongst drumlins. Compositionally, our sedimentologic-geochemical data confirm the quartz minerology of these silts, which are consistent in composition and morphology to similar deposits reported from the England and France previously identified as loess. We used U-Pb age profiling of zircons to establish the primary source of the loess, providing a robust test of whether Irish deposits are locally sourced or instead derived from more distal regions (e.g., central Europe-Asia); both scenarios have ramifications for atmospheric circulation patterns during glacial-interglacial transitions and abrupt climate shifts. While OSL dating of the Burren silts is ongoing, the sedimentary stratigraphy is consistent with deposition during or immediately following ice sheet retreat, which our 10Be-dating of glacial surfaces places during early Heinrich Stadial 1 (HS1). In Ireland, HS1 was also characterised by winter sea ice, extreme thermal seasonality, and relatively low sea level. At multiple Burren sites, a bi-fold stratigraphy suggests the in situ (i.e., airfall) loess is overlain by a subsequently reworked unit of silt that was remobilised during the mid-Holocene, potentially reflecting a combination of climatic and anthropogenic drivers. Thus far, the Burren loess is providing a new aeolian vantage on Europe’s Atlantic margin during the close of the last ice age and has considerable potential for exploring environmental conditions during climatic transitions.

How to cite: Bromley, G., Bunce, C., Stevens, T., Cabello, M., Nauton, M., and Fitzsimmons, K.: Quantifying Ireland’s Dust Bowl: An interdisciplinary assessment of loess genesis, deposition, and dynamics in the Burren, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17138, https://doi.org/10.5194/egusphere-egu23-17138, 2023.

14:22–14:24
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PICO2.12
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EGU23-3449
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ITS2.5/CL4.14
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On-site presentation
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Denis-Didier Rousseau, Pierre Antoine, Catherine Chauvel, Ségolène Saulnier-Copard, France Lagroix, Christine Hatté, Peter Hopcroft, and Markus Fuchs

The Last Climate Cycle (LCC, 130-15kyr) has shown cold, dusty (GS) and warmer, non-dusty (GI) intervals, when the atmosphere was 2-20 times more loaded with dust than today. The alternations between GS and GI occurred on millennial time scales, involving climate forcings other than orbital. The transition between GS and GI lasted on average 50 yrs, resulting from a complete climate reorganization that is not presently understood. A data-model project has acquired and investigated European loess sequences to get high-resolution and well-dated paleodust records of the LCC showing Europe experienced millennial paleodust variations through paleosol-loess unit alternations. These alternations correspond to the millennial climate variability as expressed in the Greenland ice cores, with the paleosol developments occurring during GIs, and loess deposition during GSs. Although evidenced for the last climate cycle along a 50°N transect from Brittany to Ukraine, such system prevailed at least also during the penultimate climate cycle with evidence of similar millennial climate variability during the past 192-130 ka interval, equivalent to marine isotope stage 6. Earth System Models contribute i) to characterize the source regions of the paleodust and ii) to reproduce past variations in dust deposition for key paleoclimate scenarios.

A key component of our investigation analyses loess samples dated from the last glacial maximum to detect the origin of the deposited material. A first study on the bulk sediment demonstrates that the paleodust deposited over Europe along a long longitudinal transect (about 2000 km) indicates a short distance transport implying local to regional source. Targeting the <2 microns and 2-20 microns grain size fractions and comparing with the previous results from the bulk samples, preliminary results indicate a local to regional origin for the coarse (2-20 microns and bulk) material and a more distant source for the finer fraction (<2 microns), involving longer transport in relation to general atmospheric circulation, for the finer particles. This is a critical new research question because it implies potentially important order of magnitude regional variations in dust radiative forcing that have never been accounted for in simulations of abrupt events.

How to cite: Rousseau, D.-D., Antoine, P., Chauvel, C., Saulnier-Copard, S., Lagroix, F., Hatté, C., Hopcroft, P., and Fuchs, M.: Paleodust cycle in Europe during the last climate cycle, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3449, https://doi.org/10.5194/egusphere-egu23-3449, 2023.

14:24–14:26
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PICO2.13
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EGU23-17135
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ITS2.5/CL4.14
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On-site presentation
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Slobodan Markovic, Zhentang Guo, Qingzhen Hao, Patrick Ludwig, Milivoj Gavrilov, Ivana Cvijanovic Begg, and Zoran Peric

Loess covers huge parts of the continents, especially in the middle latitudes of the Northern Hemisphere. However, except in the case of formation of the Chinese Loess Plateau, which is linked with the East Asian Monsoon, we do not know the potential relationship between loess formation and responsible air circulation types in any other loess region. Comparison between Serbian and Chinese loess-paleosol sequences provide general similarities of magnetic records. This transcontinental correlation reveals also that there are significant similarities between the magnetic records of northern Serbia and the central Chinese loess plateau. The general multi-millennial variations of magnetic proxies are almost identical in these distant major loess regions. This correspondence appears to be also similar with the globally integrated marine records, potentially suggesting accordance in soil formation processes on Eurasian scale. However, median grain size and other parameters of textural variations indicate significant differences in variations of median grain size between Serbian and Chinese loess-paleosol records. These textural differences point that Serbian loess is formed as a consequence of completely different air circulation than in the case of Chinese loess plateau. Robust evidence of grain size variations recorded in the Serbian loess indicates significant synchronicity with the appearance of Ice Rafted Debris events identified from deep sea cores in the North Atlantic during the last one million years. Higher contribution of coarse grains, the thickness of loess layers and increase of sedimentation rates in Serbian loess-paleosol sequences is associated with a more pronounced decrease of sea surface temperatures in the Western than in Eastern Mediterranean. These differences in the sea surface temperatures between the Western Mediterranean and Eastern Mediterranean illustrate more polar front fluctuations between the Pyrenees and Alps influencing the more frequent cyclone genesis in Genova gulf, as an important regional climatic anomaly. This enhanced cyclonic activity significantly influences the hydro-climatic process in the Danube Basin responsible for loess formation.

How to cite: Markovic, S., Guo, Z., Hao, Q., Ludwig, P., Gavrilov, M., Begg, I. C., and Peric, Z.: Which type of atmospheric circulations promoted formation of loess in the Middle Danube Basin during the last million years?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17135, https://doi.org/10.5194/egusphere-egu23-17135, 2023.

14:26–15:45