ClimeApp is a newly developed web-based processing tool for the state-of-the-art ModE-RA climate reanalysis. It presents temperature, precipitation and pressure reconstructions with global coverage and monthly resolution over the last 600 years. The app allows integration of historical information with climate data through composite, correlation and regression functions. The ModE project itself contains not one, but three experiments - ModE-RA, ModE-Sim and ModE-RAclim – all accessible through the app. These integrate a huge array of source material and allow the separation of the effects of external and internal forcing on the climate system in unprecedented ways. The app is designed to allow quick data processing for climatologists and easy use for non-climatologists. Specifically, it aims to help bring climate into history, where climatological data still has huge potential to advance historical research. This poster demonstrates the functions and applications of ClimeApp and the ModE-RA reanalysis. It also summarises opportunities for creating similar interfaces in other disciplines. 

ClimeApp is available at http://climeapp-modera.unibe.ch:3838/

How to cite: Warren, R., Bartlome, N., and Wellinger, N.: Bridging History and Climate Science - ClimeApp: Data processing tool for the ModE-RA Global Climate Reanalysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1255, https://doi.org/10.5194/egusphere-egu24-1255, 2024.

The project ROPEWALK, funded by the AP Møller Mærsk Fund, is a joint initiative of the Danish National Archive and the Danish Meteorological Institute over the period 2023-2026. The aim of the project is to digitize and transcribe all weather observations in ship journals and logbooks stored in the Danish National Archive.

A huge amount of data (more than 750 shelf metres) is stored in the archive, beginning as early as the 1680s. With the exception of the Napoleonic wars and the Danish state bankruptcy in 1814, the data is complete. In the archive, logbooks from Danish ships over large parts of Northern Hemisphere are found. Of particular interest are observations from two regions, the Øresund and Greenland:

In connection with the Sound duties which every ship passing the sound or belts had to pay between 1426 and 1857, weather observations were made on board of war ships placed at strategic locations near Copenhagen, Helsingør and Nyborg. These ships had to ensure that no one passed without paying the duties. Weather observations on board of these ships were tabulated starting as early as the first half of the 18th century,  and in several cases, observations were conducted every time the ship bell was struck, resulting in as many as 48 observations in the course of one day. For the oldest logbooks, which are in free text rather than in tabular form and go back to the Little Ice Age, we could locate transcriptions which are much easier to read than the original data.

The other group of logbooks which are of particular interest are from voyages to the colonies, in particular to (western) Greenland. The Greenlandic Trade Company had a monopoly for commerce with Greenland for nearly 200 years, and foreign ships would not be allowed to call a port. These "Greenland Voyages" were conducted several times per year.

In many cases, detailed sea ice observations, both from the Øresund region and the Greenland voyages, have been conducted.

The scanning of the original logbooks and journals by the National Archive in highest possible resolution is now almost complete. We have therefore initiated the transcription of the scanned documents by means of machine learning. We will present first results of this analysis.

All transcribed data will be made publicly available and can be used for future research or as input for reanalysis projects. 

How to cite: Stendel, M., Kronegh, A. J., and Skov, E. H.: ROPEWALK (Rescuing Old data with People's Efforts: Weather and climate Archives from LogbooK records) - a digitization project for three centuries of weather observations on board of Danish ships  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2830, https://doi.org/10.5194/egusphere-egu24-2830, 2024.

Recent reanalysis products offer unprecedented insights on past climates, but the paleoclimatic proxies that they assimilate are unevenly distributed in space leading to substantial simulation uncertainties over certain regions. In that context, written climate and weather records -- or docu proxies --  covering the past 2,000 years offer promising insights to complement natural proxies. However, docu proxies are also subject to a range of biases and error sources, for instance related to the cultural, technological background of the author and the prevailing need to convert qualitative observation to quantitative data assimilation input. These challenges require careful consideration when assimilating docu proxy into climate products, many of which employ a Bayesian Hierarchical approach with a forward model intended to translate climate models' initial estimates into a space that is compatible with the (natural or docu) proxy. Currently, docu proxy assimilation uses multivariate linear models for this transition, but the presence of perception biases within docu proxies suggests that linearity assumptions may not be suitable. To address this, we propose a non-linear forward model that better replicates docu proxy characteristics, aiming for more accurate assimilation. Leveraging the DOCUCLIM database and Last Millennium Reanalysis, we assess the efficacy of this non-linear approach.

How to cite: Cho, P., Müller, M., and Bolster, D.: Assimilation of Written Climate and Weather Records into Paleoclimate Reanalysis using a Non-Linear Forward Model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1378, https://doi.org/10.5194/egusphere-egu24-1378, 2024.

The jet stream over the Atlantic-European sector is relevant for weather and climate in Europe. It generates temperature extremes, steers moisture and flood-propelling weather systems to Europe or allows blocks to develop and persist leading to drought. Climate change might alter the jet characteristics affecting weather extremes. However, little is known about its interannual-to-decadal variability in the past. In this contribution we present an analysis of strength, tilt, and latitude of the Atlantic-European jet during the past 600 years in a comprehensive monthly climate reconstruction and compare their variability with drought and flood reconstructions in Europe. Summer drought is enhanced in Central Europe in periods with a poleward-shifted jet. An analysis of decadal flood variability shows that flood-rich periods in the warm season in the Alps coincide with an equatorward-shifted jet. In the cold season, a strong jet increases precipitation in Northern Europe, whereas an equatorward-shifted jet leads to frequent floods in Western Europe. Jet position, tilt, and strength are significantly influenced by El Niño and volcanic eruptions, but overall, the forced component is weak. The jet characteristics provide both a mechanism and a diagnostic to analyse decadal hydroclimate variability in Europe. Our 600-year perspective shows that recent changes in the jet are still within the past variability when considering ensemble members separately.  

How to cite: Bronnimann, S., Franke, J., Valler, V., Hand, R., Samakinwa, E., Lindstad, E., Burgdorf, A.-M., and Lipfert, L.: The Atlantic Jet and European Hydroclimate Extremes During the Past 600 Years, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14618, https://doi.org/10.5194/egusphere-egu24-14618, 2024.

The Pacific Decadal Oscillation (PDO) plays a crucial role in global decadal climate variability. However, large discrepancies persist in the determination of pre-industrial PDO variability derived from terrestrial proxy records. Here we reconstruct the PDO variability for the period 1746–2003 using a network of annually resolved marine proxy records from the extratropical North Pacific. Our PDO reconstruction (PDO_rec) provides evidences for the persistent decadal variability and tropical-extratropical interactions over the North Pacific. Superposed epoch analysis does not detect a significant response of PDO_rec to major volcanic eruptions, underscoring the dominant role of internal variability. Decadal changes in global temperature trends were found to correspond to PDO_rec for the period 1746–2003, indicating that the decadal changes in global temperature trends do not arise solely from external forcing, and may be instead modulated by internal variability.

How to cite: Han, T., Xie, Z., Wang, J., Hu, J., Wang, Z., and Yan, H.: The Pacific Decadal Oscillation modulates global temperature trends since the mid-18th century, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5249, https://doi.org/10.5194/egusphere-egu24-5249, 2024.

Recent droughts in the Mediterranean region are increasing concerns on the current and future water resources availability in this region. For this reason, studying the most severe droughts of the recent past and their associated societal responses is key to better characterise the current drought episode ongoing in Catalonia since 2021, as well as to properly define future adaptation strategies. One of these episodes of great magnitude and significant impact on economic and social activity were the droughts that occurred in Catalonia (North-East of the Iberian Peninsula) during the last third of the 19th century (1860-1890). Here, we analyse these droughts using data obtained from administrative documentary sources and instrumental meteorological records. Administrative sources were obtained from local civil and ecclesiastical authorities of eight different locations, as well as from one large irrigation community (Urgell’s Channel Irrigator’s Guild, since 1862). These historical documentary sources provide qualitative information at a daily resolution about drought impacts on the society. Together with the historical data, we also analyse different instrumental precipitation series using the Standardized Precipitation Index (SPI). This data provides a wider spatio-temporal perspective of drought behaviour for the entire Spanish territory during the study period. This study uses existing instrumental precipitation series for Spanish territory spanning from the mid-late 19th Century, with a total of 18 instrumental precipitation series obtained from INM (Spanish National Meteorology Institute). Additionally, we use 66 precipitation series in Spain obtained from the AEMET (Spanish Agency for Meteorology). This joint use of historical and instrumental data allows us to perform a spatio-temporal clustering of drought events to contextualize the intensity and persistence of the severe droughts occurring from1860 to 1890 in Catalonia. Finally, we complete the analysis of drought episodes examining their social impact, we also explore statistical data (Spanish State Statistical Year Books) from economic activities and other social variables.

How to cite: Barriendos, J., Barriendos, M., Gil-Guirado, S., Gorostiza, S., Montávez Gómez, J. P., and Andreu-Hayles, L.: Characterization and socioeconomic impacts of the late 19th Century drought episodes in Catalonia (NE Iberian Peninsula)  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12462, https://doi.org/10.5194/egusphere-egu24-12462, 2024.

Historically, climate change has played an important role in shaping human societies. Understanding past climate change is essential for human adaptation to future changes. Solar radiation, a key factor in Earth’s energy balance, hydrological cycle, and agricultural productivity, is crucial for understanding these changes. Our study focuses on reconstructing solar radiation from historical documents, shedding light on the historical impacts of climate variation and how past societies were influenced by and adapted to changing climate conditions.

In Japan, many historical documents, including daily weather records from the 17th to 19th centuries, have been key to understanding historical climate variations. Utilizing these descriptions, we developed a method for reconstructing solar radiation. This method enabled us to analyze solar radiation patterns from 1821 to 1850, providing valuable insights into climate variations and their socio-economic impacts during this period.

Our analysis, which focused on the 1830s Tempo Famine, revealed a clear relationship between climate variations and economic fluctuations. We found that the decrease in solar radiation during the summers of 1833, 1836, and 1838 corresponded with rising rice prices in Osaka, underscoring the impact on agricultural productivity and market dynamics.

These findings suggest that the solar radiation pattern in the summer of 1836 dramatically influenced the severe famine, as evidenced by the unusual rise in rice prices. This study refines the understanding of the historical climate impacts on society and highlights the broader effects of climate variation on agriculture and market economies. This emphasizes the need to integrate climate information into economic analyses and could provide valuable insights for developing contemporary climate change policies and adaptation strategies.

How to cite: Ichino, M., Masuda, K., Mikami, T., and Takatsuki, Y.: Abnormal Climate and the Market Economy: the Relationship between Reconstructed Solar Radiation and Rice Price during the Famine of 1830s in Japan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7122, https://doi.org/10.5194/egusphere-egu24-7122, 2024.

Information about past floods and historical precipitation records is fundamental to the management of water resources, but observational records usually cover only 100–150 years. Using several different data sources, such as newly digitized meteorological data from several stations in the south-eastern part of Romania, historical newspapers of that time, and daily reanalysis of large-scale data, here we provide a detailed analysis of the atmospheric circulation conditions associated with one of the most devastating flood events which took place in June 1897. The floods in June 1897 were one of the most devastating natural disasters in Romania's history and they were caused by heavy rainfall that started at the beginning of May and continued for several weeks, resulting in widespread flooding, especially in the eastern part of the country. The most affected areas were the cities of Braila of Galati, located on the main course of the Danube River, where the floods caused extensive damage to infrastructure, including homes, bridges, and roads, and disrupted transportation and communication networks. The heavy rainfall events occurring in June 1897 and the associated flood peak were triggered by intrusions of high Potential Vorticity (PV) anomalies toward the southeastern part of Europe, persistent and pivotal cut-off lows over the analyzed region, and increased water vapor transport over the south-eastern part of Romania. We argue that digitizing and analyzing old meteorological records enables researchers to better understand the Earth's climate system and make more accurate predictions about future climate change. 

How to cite: Nagavciuc, V., Ionita, M., Beudean, M., and Nagavciuc, I.: Shedding light on the devastating floods in June 1897 in Romania: early instrumental observations and synoptic analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6686, https://doi.org/10.5194/egusphere-egu24-6686, 2024.

Considering the importance of hydroclimate conditions in the development of both natural and anthropic environments, a better understanding of past conditions is imperative. Keeping this as a main trajectory, the objective of our study is the reconstruction of the past hydroclimate and environmental conditions in Central Romania over the last two millennia, by a high-resolution analysis of a peat sequence from Arpaşu de Sus (Făgăraș Depression, Southern Transylvania). We used biotic proxies (testate amoebae, pollen and spores) to quantitatively reconstruct the water level depth fluctuations in the peat bog and abiotic (lithology, AMS radiocarbon dating, organic matter content, bulk density, magnetic susceptibility) to reconstruct the vegetation dynamics and the human impact in the studied area.

The peat bog had ombrotrophic characteristics throughout the studied period, with organic matter percentages ranging from 85 to 95%. The pollen analysis results show that the vegetation of this interval was characterized by extensive forests dominated by Fagus sylvatica, accompanied by Carpinus betulus and Alnus sp. The reconstructed water table depth values, based on testate amoeba assemblages, fluctuated between 32.9 and 11.8 cm.

Our findings are in good agreement with other results from Romania and Central-Eastern Europe, bringing valuable insight to a better understanding of the hydroclimate changes that occurred in Europe in the last two millennia.

How to cite: Ruskal, A., Grindean, R., Diaconu, A.-C., and Tanțău, I.: A glimpse into the Hydroclimate and environmental trends of the past two millennia in Southern Transylvania, Romania, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14408, https://doi.org/10.5194/egusphere-egu24-14408, 2024.

Knowledge of the underground temperature distribution is crucial for evaluating geothermal potential and ensuring the long-term safety of heat-producing waste in repositories. Previous research, mainly conducted in Northern Europe and Canada, has shown that the Pleistocene Glaciations have an additive effect, resulting in a cooling of several degrees Celsius at depths of up to two kilometers. Recent studies indicate that the Last Glacial Period and the recent warming of the past 100–150 years have the greatest paleoclimatic impact on the current shallow to medium depth subsurface temperature distribution in Germany. If thermophysical properties of the subsurface are known, the distribution of underground temperatures can also be used to reconstruct the local ground surface temperature history using borehole climatology. Ground surface temperature reconstructions have low temporal resolutions, but they are directly reconstructed from temperature measurements without the use of climate proxies. Observations of the subsurface temperature distribution are limited to boreholes that are undisturbed by drilling or operations like production tests. Furthermore, the coupling of ground surface temperatures and surface air temperatures presents a significant challenge due to complex and transient surface processes associated with soil types, precipitation, vegetation, and the distribution of water bodies and glaciers. A systematic study of the paleoclimatic impact on the subsurface temperature distribution in sedimentary regions in Germany has not yet been conducted. Moreover, borehole climatology studies in Canada and Northern Europe has mainly concentrated on local reconstructions of ground surface temperatures, focusing on single or a limited number of boreholes. The aim of this study is to investigate the paleoclimatic effect of the Holocene on the subsurface temperature distribution in Germany and to quantify regional variations in the ground surface temperature histories. To achieve this, we have identified wells in sedimentary regions across the country that satisfy the prerequisites for borehole climatology. By using geophysical well logs, we derive the thermophysical characterization of the subsurface. We are examining the continuous temperature profiles to determine the magnitude, and regional variability of the Holocene paleoclimatic signal in borehole temperature profiles throughout Germany.

How to cite: Salis Gross, E., Frick, M., Norden, B., Mutz, S. G., and Fuchs, S.: Regional effects of paleoclimate history on the subsurface temperature distribution in Germany, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12754, https://doi.org/10.5194/egusphere-egu24-12754, 2024.

With the background of global warming, the hydrological cycle has accelerated and the occurrence of extreme precipitation events has also increased, bringing significant impact on agriculture, transportation, and human safety. The investigation of the frequency of historical or ancient extreme precipitation events is helpful for a better management of modern hydrological disasters and a reasonable prediction of future precipitation variations. The present study focuses on Lake Dalzong, an alpine lake located in Xiahe County, Gansu Province, northeastern Tibetan Plateau, and provides a lacustrine record of extreme precipitation variations during the last millennium in the study region.

Considering that Lake Dalzong is a varve lake, we monthly and seasonally collected modern surface sediment samples, lake water samples, and precipitation samples from June 2020 to October 2023. By analyzing the hydrogen and oxygen isotopes of water samples, we found that the lake is a hydrology open system and the lake water is mainly supplied by precipitation. From the measurements of the surface sediments and typical laminated samples, annual lamination was successfully identified. It is found that the coarse-grained dark layer was formed under increased precipitation from the summer to the early autumn, as heavy rainfall can bring exogenous detrital materials into the lake. And the fine-grained light layer was deposited during the freezing period of the lake from mid-November to mid-April of the following year when lake water was still and tiny dead organisms deposited slowly. Therefore, the varve layers are ideal archive of extreme precipitation variations in the region.

Furthermore, a continuous sediment core reaching the bedrock, with a total length of 457.5 cm, was obtained from the center of the lake, and a reliable chronological framework for the past thousand years was established by using ¹³⁷Cs and AMS¹⁴C dating, as well as the varve counting. Based on the analysis of grain size, XRF elemental data with high resolution, and the extreme precipitation variations was reconstructed. The coarse-grained dark layer with a thickness of 0.3~1.2 cm was extracted and defined as the varve event layer. It matched well with the peak percentage of coarse grain and the relative content of Ti elements, indicating that there was a corresponding relationship between the varve event layers and the extreme precipitation events. The results show that the frequency and intensity of extreme precipitation events increased during the Little Ice Age but decreased since the Industrial revolution. A further investigation shows that the extreme precipitation variations in the northeastern Tibetan Plateau was controlled by the external-driven factors and the ocean-atmosphere interactions in the Earth system.

How to cite: Wu, D., Kong, W., Liang, Y., Guo, S., Wang, T., Huang, J., and Pan, L.: Extreme precipitation variations in the northeastern Tibetan Plateau during the last millennium, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19162, https://doi.org/10.5194/egusphere-egu24-19162, 2024.

The Millennium Eruption (ME) of Changbaishan Tianchi Volcano is heralded as one of the largest explosive eruptions in the Late Holocene. The geochemistry method estimated that the ME not only produced huge quantities of volcanic debris and lava flows but also emitted up to 45 Tg of sulfur into the atmosphere. The sulfate emissions are higher than the Tambora eruption in 1815 CE, which caused a year without a summer in Europe. Despite such massive emissions, evidence for this eruption's climatic impact in East Asia remains elusive. To explain this contradiction, this study evaluated currently available high-resolution proxy records from the Northern Hemisphere spanning the past two millennia and conducted a volcanic sensitivity experiment using the Community Earth System Model (CESM). Results show that the high-resolution proxy records demonstrate an overall muted negative response during the period of the dating uncertainties, with 945 CE marking the most notable negative anomaly. The sensitivity experiment shows that ME caused significant negative anomalies in both temperatures and precipitation rates in East Asia. Based on the results, we infer that the contradiction between the high Sulfur emissions and a slight glacial sulfate signal may originate from the fact that the ME occurred in 945 CE instead of 946 CE, and the volcanic climatic effects were mitigated by the combined effects of the 945 CE El Niño-like Sea-surface temperatures (SSTs) and the Brewer–Dobson circulation. This study offers a novel perspective on the ME's climatic influence, reconciling previous discrepancies regarding its climatic impact.

How to cite: Yang, Y. and Shi, F.: Climate Impacts of The Millennium Eruption of The Changbaishan Volcano, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14496, https://doi.org/10.5194/egusphere-egu24-14496, 2024.

We explore whether improvements to the Twentieth Century Reanalysis (20CR) in the most recent version (v3) have improved representation of the Southern Annular Mode (SAM).  The negative SAM index bias in the first half of the 20th century compared to instrumental SAM reconstructions in previous 20CR versions (due to a systematic high latitude high pressure bias) is still present. It is reduced in summer and autumn, but not in winter and spring.  Correlations between reanalysis and reconstructed SAM indices through the full series in all seasons do show improvements in v3 compared to previous versions.  

A reduction in SAM index ensemble spread is evident during periods with higher numbers of assimilated observations, in particular in summer and autumn.  Analysis of the spatial distribution of assimilated observations shows clear improvement in years/periods with greater numbers of ships observations in the Southern Ocean and Antarctic observations (e.g. early 20th century Antarctic expeditions).  However it is not until the advent of greater numbers of ships observations in the Southern Ocean and regular data from Antarctic meteorological stations in the late 1940s that there are enough high latitude observations to realistically constrain the reanalysis.  

Enhancements have been enough to improve how the reanalysis follows the observations temporally, highlighting the benefit of data rescue, but due to the bias, we recommend that the 20CR should still not be used for the analysis of long-term SAM trends, and caution should be exerted when using SLP data from the high latitude Southern Hemisphere from all 20CR versions prior to 1957.

How to cite: Jones, J., Lorrey, A., Fogt, R., Slivinski, L., Compo, G., Brohan, P., and Marshall, G.: An evaluation of the Southern Annular Mode in the Twentieth Century Reanalysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11470, https://doi.org/10.5194/egusphere-egu24-11470, 2024.

Some El Niño events are characterized by very warm conditions in the far-eastern Equatorial Pacific (FEP), but cool conditions elsewhere in the central Equatorial Pacific (CEP). The impact of these so called Coastal El Niño (CEN) events is particularly strong, associated with extreme rainfall events over the coastal northern Peru, Ecuador and adjacent Andean slopes. Despite the fact CEN events represent a high cost for social and economic development of these countries, little is known in terms of frequency, mechanisms and predictability and only very recently science and society are paying attention to these episodes. Here we use the tree-ring width (TRW), as well as stable oxygen (δ¹⁸O) and carbon (δ¹³C) isotopes measured in tree rings to reconstruct Sea-Surface Temperature (SST) in the Equatorial Pacific Ocean described by the two first Empirical Orthogonal Function (EOF). While EOF1 corresponds to the CEP region, EOF2 represents the FEP region.

The newly developed TRW and isotopic records span from 1890 to 2007 and were built from Polylepis rodolfovasquezii trees located at 4,360 m a.s.l in an Andean forest in Peru (11.72°S, 75.14°W). Our results show significant (-) correlation between tree-ring δ¹³C and temperature during the previous growing season peak, while non climatic signal was found in TRW and δ¹⁸O records. During the current growing season tree-ring δ¹⁸O is the proxy that exhibits the highest sensitivity to both, precipitation (-) and temperature (+) compared with the two other tree-ring parameters. In addition, the δ¹⁸O record displays more consistent correlation patterns with both EOFs, suggesting that δ¹⁸O may contain stronger climate signals than TRW and tree-ring δ¹³C. Lastly, the use of a sequential leave-20-out calibration-validation technique for reconstructing the variability of EOFs indicated that the δ18O record was effective to reconstruct EOF1. However, incorporating a multi-proxy strategy, which includes TRW, δ18O, and δ13C, enhanced the overall quality of the reconstruction. In contrast, the multi-proxy approach was not enough to reconstruct EOF2. We conclude that expanding the geographical distribution of proxy records into new in-land areas around the FEP, where SST variability has a local impact on hydroclimate, it is a priority in order to reconstruct CEN. Tree-ring stable isotopic records are valuable to complement existing TRW chronology to overcome the inherent difficulties on using tropical Andean species for paleoclimate research.

How to cite: Rodriguez Morata, C., Requena Rojas, E. J., Ticse Otalora, G., Morales, M., Crispín DeLaCruz, D., and Andreu hayles, L.: Reconstructing the Sea-Surface Temperature at the Equatorial Pacific using tree-ring proxies from the Peruvian central Andes. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16569, https://doi.org/10.5194/egusphere-egu24-16569, 2024.

Drylands are highly vulnerable to climate change due to their fragile ecosystems and limited ability to adapt. In contrast to the global drying after tropical volcanic eruptions shown previously, we utilize the last millennium simulations to demonstrate that large tropical volcanic eruptions can induce significant two-year hydroclimatic wetting over drylands. During this wetting period, which extends from the first to the third boreal winter after the eruption, several hydroclimatic indicators, such as self-calibrating Palmer Drought Severity Index based on the Penman-Monteith equation for potential evapotranspiration (scPDSIpm), standard precipitation evapotranspiration index (SPEI), aridity index (AI), top-10cm soil standard precipitation evapotranspiration index (SPEI), aridity index (AI), top-10cm soil drylands. The primary contribution to the wetting response is the potential evapotranspiration (PET) reduction resulting from dryland surface cooling and reduced solar radiation, as well as a weak contribution from increased precipitation. The latter is due to the wind convergence into drylands caused by slower tropical cooling. This dryland wetting response to volcanic eruptions is encouraging news for stratospheric sulfur aerosol injection, which mimics the cooling effect of volcanic eruptions for combating global warming.

How to cite: zhou, S., Liu, F., Dai, A., and Zhao, T.: Dryland hydroclimatic response to large tropical volcanic eruptions during the last millennium, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7024, https://doi.org/10.5194/egusphere-egu24-7024, 2024.

The East Antarctic Plateau contains particular areas with megadunes and wind-glazed surfaces, exhibiting distinct patterns of snow accumulation and its variability over time and space. Despite its significance for sea levels, ocean circulation, and weather patterns, knowledge about snow accumulation in these areas remains limited. Several ice cores, coming from diffrent parts of Plateau, were drilled during the East Antarctic International Traverse (EAIIST).

Using volcanic horizons as time markers, coupled with ground-penetrating radar (GPR) measurements, we intend to reconstruct the surface mass balance (SMB) of the megadune plateau in both time and space for the last ca. 2000 years where accumulation is largely unknown. In a first step, geochemical profiles of the different cores were analyzed. A critical analysis is first conducted to find the best marker of the volcanic eruptions between the electrical conductivity, the total sulfur concentration and the sulfate profile. Based on this critical analysis, a common volcanic-dating scale is proposed for the different drilling sites. However, the megadune areas show a strong disturbed layering accumulation with clearly visible ablated layers, making the volcanic identification a true challenge.  Work is currently underway to use volcanic cryptotephra and electron microprobe analysis to unambiguous determine the volcanic tie-point identification. In a subsequent step, GPR data will be process to spatialize the accumulation information. Matching radar internal layers with well-dated ice core reference layers will allow for dating and deducing the surface mass balance over time for the entire EAIIST transect.

How to cite: Bursztynowicz, J., Savarino, J., Daviet, B., Ginot, P., Le Meur, E., Gautier, E., Witwicky, J., Jong, L., Spolaor, A., and Stenni, B.: Surface Mass Balance of the Antarctic Megadune Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5908, https://doi.org/10.5194/egusphere-egu24-5908, 2024.

In the quest of understanding the past and present climate system, we aim to reconstruct paleo-climate using Bayesian inversion from Antarctic borehole temperature profiles. We aim to develop a refined process for reconstructing the temperature evolution of Antarctica over the last century and millennia. Initially, a forward heat transfer model is implemented that simulates borehole temperature profiles for time-dependent surface temperatures. The forward model provides an approximate notion of the borehole depth at which a signal from the past may be obtained. Using forward simulations, a greedy approach is employed for the optimal placement of temperature sensors in the borehole to record temperature effectively. We invert the forward model to reconstruct past surface temperature evolution from borehole temperature measurements. For this, we apply Bayesian inference to optimally account for the uncertainty in the various influencing quantities. We model known uncertainties as priors and obtain the reconstructed surface temperatures with connected uncertainty information.

How to cite: Shaju, K., Laepple, T., and Zaspel, P.: Ice Borehole Thermometry: Paleo-Climate reconstruction using Bayesian modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10661, https://doi.org/10.5194/egusphere-egu24-10661, 2024.

During the last millennia, prior to the industrialization, long-term climatic variations correlate with low-frequency total solar irradiance (TSI) changes. This long-term correlation does, however, not prove or disapprove a causal relationship. An additional natural forcing is the volcanic activity. The exact magnitudes of these two natural forcings are not known because reconstructions are based on proxy data which include substantial uncertainty. The Maunder Minimum, a period between roughly 1600 and 1700 A.D., is characterized by lower temperatures, low solar activity, and relatively high volcanic activity. There is still a debate on how forcing, i.e., solar vs. volcanic, influenced the climate and to which extend during that time. The amplitude of the TSI decrease is especially uncertain and suggestions range from a few W/m² to a few tens of W/m² lower than today’s value. Here we present simulations with the chemistry-climate model SOCOL where different solar forcings ranging from +10 W/m² to -20 W/m² in TSI terms are applied. On a global scale, changes in temperature are linear with changes in TSI. On a regional scale, however, the temperature response can be non-linear especially at high latitudes. The mechanisms leading to the non-linear behavior are explored.

How to cite: Sedlacek, J., Sukhodolov, T., Egorova, T., and Rozanov, E.: Sensitivity and linearity of surface temperature response to solar irradiation changes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12244, https://doi.org/10.5194/egusphere-egu24-12244, 2024.

The North Atlantic Current and its extensions, including the Norwegian Atlantic Current (NwAC), transport warm and saline upper ocean waters from the North Atlantic north-eastward into the Nordic Seas. The interaction between this saline inflow versus freshwater runoff into the Arctic is important in modulating the response of the Atlantic Meridional Overturning Circulation to climate change. To better understand variability in the strength and character of this inflow and the closely linked North Atlantic Subpolar Gyre, paleoceanographic reconstructions aim to extend the limited temporal scope of existing instrumental records. Here, we present high-resolution reconstructions of temperature and salinity from coupled d¹⁸O – Mg/Ca measurements on two species of planktonic foraminifera, as well as estimates of upper-ocean radiocarbon ages from a rapidly accumulating marine sediment core located under the NwAC (GS06-144-22; 62.5ºN, 4.1ºE, 921m). Using a novel, robust chronology for this core, we determine changes in the surface radiocarbon reservoir effect at the site, which - along with the seasonal temperature and salinity reconstructions - provide new insights into NwAC and Subpolar Gyre dynamics over the last millennium.

How to cite: Starr, A., Muschitiello, F., Simon, M., Tisserand, A., Andersson Dahl, C., Dokken, T., and Osman, M.: Atlantic inflow insights from sediment core reconstructions of the Norwegian Atlantic Current over the past 1000 years, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19884, https://doi.org/10.5194/egusphere-egu24-19884, 2024.

This study aims to contribute data, that will improve understanding on the role of Greenland ice sheet melt in modulating midlatitude climate.

A great hamper to our understanding of the influence from Greenland ice sheet melt on European climate variability comes from the lack of high-resolution observations of dynamic mass loss from the from Greenland Ice Sheet extending beyond the instrumental time scale. Building on a large repository of sediment cores taken from fjords by some of Greenland’s largest marine terminating glaciers, we aim to reconstruct multi-decadal to centennial scale changes in the iceberg production (solid ice mass loss) over the past 2ka. The IRD proxy method has conventionally been used in deep sea cores to elucidate major instability events of glacial ice sheets but has shown potential as a glacier proxy through the correspondence of the 20^th century IRD records with historical and instrumental records of glacier margin positions of Sermeq Kujalleqand Upernavik Glacier in West Greenland, and Helheimand Kangerlussuaq Glaciers in Southeast Greenland.

Here we show reconstructions of dynamic mass loss from from Sermeq Kujalleqand Helheim Glacier over the past 2ka. The data indicate marked melt variability at the multidecadal to centennial time scales from West Greenland during the Roman Warm Period, whereas SE Greenland Glaciers may have been buffered by sea ice at this time.

How to cite: Andresen, C. S., Hesselbjerg Christensen, J., Lauritzen, M., Brinkmann, I., Schøtt Hvidberg, C., van der Laan, L., Nisancioglu, K., Gomez, N., and Grotheer, H.: Observations of Greenland Ice Sheet mass loss over the past 2ka, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21057, https://doi.org/10.5194/egusphere-egu24-21057, 2024.

The transitional zone of the Mexican Pacific is a complex region in terms of its oceanographic conditions. This leads to changes in primary and exported productivity over various time scales. This study employs geochemical tracers—organic carbon (CO), biogenic opal, and calcium carbonate—to assess sedimentary records' primary and exported productivity. Analyzing responses to past warm periods is crucial for understanding marine productivity in future climate change scenarios. The objective of the present study was to quantify organic carbon content and to infer changes in primary and exported productivity in the transitional zone of the Mexican Pacific for the late Holocene and the final part of the middle Holocene. The sediment core, collected at a depth of 680 meters on the southwestern margin of Baja California Sur. It has a length of 137 cm and was sectioned at intervals of 1 cm, representing 137 samples. The estimated age from ¹⁴C was 5466 years. Each one-centimeter interval denotes 33 years. CO analysis used a COSTECH 4010 elemental analyzer with 0.2% analytical accuracy, employing BBOT and Urea certified standards. Biogenic opal determination follows the molybdenum blue spectrophotometric method by Mortlock and Froelich (1989). CO content ranged from 8% and 14%, showing periodic changes at ~300, ~170, and ~100 years. Biogenic opal ranged from 0.2 to 19.3%, with abrupt changes at ~310, ~270, and ~70 years. Organic carbon and biogenic opal exhibited a positive correlation, indicating increased productivity during warm periods like the Roman Warm Period (1800 to 2200 years ago) and the Medieval Warming Period (700 to 1100 years ago). This suggests responsiveness to oceanographic conditions across various time scales.

How to cite: Acevedo, T. and Sánchez, A.: Analysis of Primary Productivity Variability in the Transitional Zone of the Mexican Pacific during the Late and Middle Holocene, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6704, https://doi.org/10.5194/egusphere-egu24-6704, 2024.