This open session invites contributions in the field of ocean and land climates, which do not fit into the specialized sessions. It will welcome presentations of modelling studies as well as (paleo)-observations. Here, papers will be collected from those sessions, which attracted a too small amount of contributions and did not fit into other specialized sessions both on climatology and paleoclimatology. However this is a session by itself and you must feel free to submit directly your paper to the Open session. This guarantees all authors an appropriate representation.
Opportunities of publishing your contribution is proposed in the on-line and open access EGU journal "Climate of the Past" www.climate-of-the-past.net
The controversy between the CO2 driving or lagging models is elucidated in a new climate model, that reunites insights from models from other planets, carbon draw down models during earth history as a whole, spores spike related to catastrophic events from the Phanerozoic, late Palaeozoic climate models and carbon dioxide and temperature fluctuations during the Quaternary as shown by Petit et al., (1999).
This model advocates that for the natural system orbitally induced insolation maxima (eccentricity in particular) momentarily and erratically trigger ocean degassing and drive temperature rise orbitally while it is otherwise driven by carbon drawdown through photosynthesis leading to cooling.
For the natural system high concentrations of particulate organic carbon (fungal spore, pollen, vegetation debris, soot and charcoal) or abiotic dust are forming crystallisation cores that trigger an ephemeral greenhouse effect in the cirrus from the lowermost stratosphere. This happens at the onset of orbital insolation peaks when warming leads to larger crystal sizes. The consecutive warming induces the waxing of the cirrus forming sphere which necessarily has lower concentrations of crystallisation cores and shifts back to the albedo effect.
In this model the decrease in CO2 concentration in the atmosphere through photosynthesis regulates temperature and supports the view that temperature lags CO2 concentration, yet in this natural system, the greenhouse effect is briefly triggered by orbital forcing and support the results of Feulner (2017) indicating that both the carbon drawdown and orbital forcing are driving temperature in the natural system. In this model the CO2 gets ping-ponged from the terrestrial to the marine system until both are depleted in CO2. It indicates that, ultimately, under natural circumstances, spreading rate and tectonic events drive climate. From this model it also follows that the industrial use of organic and inorganic carbon sinks, as they have constantly been replenished during earth history through tectonic activity, will lead to CO2 concentrations as experienced before photosynthesis appeared and concentrations far beyond.
The aberrant CO2 and temperature rise in the Anthropocene reflects the tempering of the response system in the lowermost stratosphere because of increasing concentrations of particulate organic carbon and dust by changing land use, lowering of the ground water table by wood cutting, aridification (pyro-cumulonimbi), transport (contrails) and soot emission.
How to cite:
Waveren, I.: Midas or Gaia revisited, about anthropogenic tempering with the natural response system, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2689, https://doi.org/10.5194/egusphere-egu2020-2689, 2020
Marianne T. Lund, Borgar Aamaas, Camilla W. Stjern, Zbigniew Klimont, Terje K. Berntsen, and Bjørn H. Samset
Achieving the ambition of the Paris Agreement and meeting the Sustainable Development Goals require both near-zero levels of long-lived greenhouse gases and deep cuts in emissions of so-called short-lived climate forcers (SLCFs), including methane and black carbon. Here we present a comprehensive dataset of contributions to future global temperature change from emissions of CO2 and individual SLCFs from 7 economic sectors and 13 source regions, both as they are today and as they are projected to change under the Shared Socioeconomic Pathways (SSPs). Such detailed knowledge about the mix of emissions from individual sources and benefits and trade-offs of reductions is essential for designing efficient mitigation strategies at the national and international levels, as well as for informing policy processes on how to best address linkages between climate, sustainable development and air quality.
Our results demonstrate that the mitigation potential inherent in the present SLCF emissions is highly inhomogeneous across region and sector, and that co-emissions of all species – including CO2 – should be considered in any targeted climate policy. We also reinforce the importance of reducing methane emissions, from agriculture, waste management and energy production, for reducing warming in the near-term. In contrast, in many regions, reducing industry emissions brings air quality benefits but may cause a net additional near-term warming. The spatiotemporal heterogeneity is expected to continue under the SSPs. Most scenarios project a particularly strong increase in aerosol and other SLCF emissions in South Asia and Africa South of the Sahara, suggesting that technology development and air pollution legislation in these regions is a key step in the transition to a low emission future. Moreover, both rapidly increasing and decreasing emissions of SLCFs will play an important role in shaping the regional climate and air quality.
By using an analytical climate model, we build a methodological framework that can be used to estimate the impact of any emission scenarios. Our data set hence provide a toolkit for further studies of implications of mitigation pathways and policy responses, and support assessments of environmental impacts.
How to cite:
Lund, M. T., Aamaas, B., Stjern, C. W., Klimont, Z., Berntsen, T. K., and Samset, B. H.: Global temperature response to regional and sectoral air pollutant and greenhouse gas emissions under the Shared Socioeconomic Pathways, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11039, https://doi.org/10.5194/egusphere-egu2020-11039, 2020
Evaluation of Clouds in the E3SM Atmosphere Model with Satellite Simulators
Yuying Zhang, Shaocheng Xie, Wuyin Lin, Stephen A. Klein, Mark Zelinka, Po-Lun Ma, and Philip J. Rasch
Ulas Im, Kostas Tsigaridis, Cynthia H. Whaley, Gregory S. Faluvegi, Zbigniew Klimont, and Knut von Salzen
The Arctic Monitoring and Assessment Programme (AMAP) is currently assessing the impacts of Short-Lived Climate Forcers (SLCF) on Arctic climate and air quality. In support of the assessment, we used the NASA Goddard Institute of Space Sciences (GISS) Earth System Model (modelE2.1), with prescribed sea surface temperature and sea-ice fraction, to simulate SLCF concentrations globally between 1995 and 2015. Two simulations were conducted, using the One-Moment Aerosol (OMA) and the Multiconfiguration Aerosol TRacker of mIXing state (MATRIX) aerosol modules. OMA is a mass-based scheme in which aerosols are assumed to remain externally mixed and have a prescribed and constant size distribution, while MATRIX is an aerosol microphysics scheme based on the quadrature method of moments, which is able to explicitly simulate the mixing state of aerosols. Anthropogenic emissions from the ECLIPSE v6b emissions database were used, along with emissions from aircrafts and open biomass burning from the Coupled Model Intercomparison Project Phase 6 (CMIP6), while the natural emissions of sea salt, DMS, isoprene and dust are calculated interactively. The simulated monthly surface concentrations of sulfate (SO4), black carbon (BC), organic carbon (OA), and ozone (O3) are compared with observations from a set of Arctic stations, extracted from the EBAS and IMPROVE databases, as well as a few additional locations. Simulated aerosol optical depths (AOD) are also compared with Advanced Very-High Resolution Radiometer (AVHRR). The study will present the evaluation of the modelE2.1 in simulating SLCF levels over the Arctic using different aerosol schemes, along with observed and simulated trends of SLCFs over the Arctic between 1995 and 2015.
How to cite:
Im, U., Tsigaridis, K., Whaley, C. H., Faluvegi, G. S., Klimont, Z., and von Salzen, K.: Short-Lived Climate Forcers over the Arctic between 1995 and 2015 as simulated by the GISS modelE2.1, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6095, https://doi.org/10.5194/egusphere-egu2020-6095, 2020
The Turpan basin is one of the most arid and water insecure regions in China. The mountain snowmelt is the primary source of water. To assess the impact of climate change on stream flow, this study examined the long-term trends and change points of hydro-meteorological variables and explored the possible correlation between them at annual and seasonal scales. A set of non-parametric statistical tests including Mann-Kendall, Kendall’s tau, Sen’s slope estimator, and Pettitt test was applied, and change point of the hydro-meteorological variables. This study provided valuable information in understanding the changing properties of the stream flow in the basin and insights for a better integrated water resources management planning.
How to cite:
Du, L.: Hydrological Variability and its Response to Climate Change in Turpan basin, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12545, https://doi.org/10.5194/egusphere-egu2020-12545, 2020
This present paper reports eight modern ostracode collected from the bottom of the Xingyun Lake,Yunnan Province, including Candonocypris novaezelandiae (Baird, 1843), mateless cyclocypris Cypridopsis Vidua (O.F.M ller, 1776), star (which really wedge dielectric) Eucypris CF. Cuneata (Tsao, 1959), Cleveland star kraeplini (G.W.M mediated Cypris ller, 1903) Belgium, sheshi (similar) glass dielectric Schellencandona CF. Belgica (Klie, 1937), Fabaeformiscandona subacuta (Yang, 1982), unarmed mobs mediated Cetacella inermis (Martin, 1958), the Yunnan flower (compare kinds) Yunnanicyhere cf.reticulate mediated gen.etsp.nov. the true star (dielectric wedge comparison of three) Eucypris CF. Cuneata (Tsao, 1959), unarmed mobs mediated Cetacella inermis (Martin, 1958) and Yunnan (a comparison of dielectric reticulate flowers) Yunnanicyhere cf.reticulate gen.etsp.nov. these species are newly recorded from modern lakes.It has enriched the understanding of freshwater ostracoda of the biological communities in China.
Key word freshwater ostracods; Xingyun Lake; Yunnan Province
How to cite:
Xie, M.: New records of freshwater ostracoda from the xingyun lake, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8357, https://doi.org/10.5194/egusphere-egu2020-8357, 2020
In this study, we focus on the relationship between the water vapor source region and the isotopic composition of the precipitation. The change of isotope characteristics of precipitation depends on the moisture source region. Long-term stable isotope (δ18O, δ2H ) measurements of precipitation were performed in Debrecen, Hungary, between 2001 and 2014. The long-term isotope time series and trajectory modeling are suitable for determining moisture source regions. Backward trajectory analysis was carried out using the Lagrangian Raptor model based on ERA5 atmospheric data. Hourly backward trajectories were calculated for Debrecen for the days with precipitation in the period between 2001-2014.
Based on the study three source regions were identified. Of these, 60% represented the Carpathian Basin, which is where most of the moisture evaporated from near the surface. The remaining 40% of the northwest and southwest were represented by moisture source regions. This means that the isotopic composition of precipitation significantly determines the local and continental effects, i.e. the moisture evaporated from the continental surface contributes significantly to the spatial and temporal variation of the precipitation isotope composition.
How to cite:
László, E., Palcsu, L., and Leelőssy, Á.: Identification of moisture source region based on trajectory model analysis and isotopic composition of the precipitation in Debrecen, Hungary , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18226, https://doi.org/10.5194/egusphere-egu2020-18226, 2020
Anita Puskás-Preszner, Carmen Fekete, Elemér László, László Kompár, Andor Hajnakl, and László Palcsu
This paper describes the relation of noble gas temperature (NGT) and mean annual air (MAAT) and soil (MAST) temperature through studying water samples and meteorological data from six Hungarian regions. Alluvial plains, hilly and mountainous regions were studied to investigate the effects of geomorphological, hydrogeological and micro-climatic conditions. Water samples were collected from springs and wells fed from different aquifers. Comparing NGTs derived from these water samples with the MAAT and MAST values of the given region, we identified differences between the sampled areas. In case of the Geresd Hills, Mezőföld, Danube-Tisza Interfluves and Nyírség, the NGTs (13.0 ± 0.9 °C, 12.1 ± 1.1 °C, 12.1 ± 0.6 °C and 12.7 ± 1.6 °C, respectively) generally reflect MAST, however in karstic Bükk Mts. (6.8 ± 0.6 °C) and Mecsek Mts. (10.7 ± 1.9 °C) they are closer to MAAT. Consequently, it can be concluded that the direct relationship between noble gas temperature and mean annual air temperature is not always as well-defined as it is often assumed. It is shown that MAAT and MAST should be distinguished, especially when using NGT as a paleoclimate proxy.
How to cite:
Puskás-Preszner, A., Fekete, C., László, E., Kompár, L., Hajnakl, A., and Palcsu, L.: Comparison of noble gas temperature with recent mean annual air and soil temperature in different regions of Hungary, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13537, https://doi.org/10.5194/egusphere-egu2020-13537, 2020
Jinheum Park, Jungjae Park, Sangheon Yi, Jin Cheul Kim, Eunmi Lee, Quihong Jin, and Jieun Choi
A relationship between climate change and prehistoric civilizations is a topic of growing interest. Here, we present a 6,000-year-long pollen, X-ray fluorescence (XRF), and grain size data of the core STP18-03 from the southern Korean peninsula, spanning the mid- to late- Holocene. The proxies generally show a synchronous change throughout the core. During dry periods, reduced precipitation indicated by lower sand proportion (river discharge) would have hindered tree growth, which then resulted in increased titanium erosion from nearby hills, and vice versa. The drying trend is remarkable during ca. 4.8, 4.3, 4.0, 3.3, 2.7-2.3 ka BP and corresponds with sudden dropping points of a summed probability distribution (SPD) of archaeological records found in the Korean Peninsula. This implies that ancient civilizations of Korea responded highly sensitively to abrupt climate deterioration. As an underlying mechanism of the change, we suggest a role of the equatorial Pacific Ocean. The temporal pattern of our arboreal pollen proportion closely follows that of sea surface temperature (SST) data from the Western Pacific Warm Pool (WPWP) region. Furthermore, the dry periods indicated by our multiple proxies coincide with strong El Niño–Southern Oscillation (ENSO) activity, when the core region of the warm seawater pool deviated eastward than usual. This supports that the equatorial Pacific Ocean has served as an important factor for modulating mid- to late- Holocene hydroclimate of the Korean Peninsula, where the East Asian Summer Monsoon (EASM) accounts for nearly 70 percent of the total annual precipitation amount.
How to cite:
Park, J., Park, J., Yi, S., Kim, J. C., Lee, E., Jin, Q., and Choi, J.: A synchronous change of mid- to late- Holocene hydroclimate and prehistoric population in coastal East Asia indicated by pollen, XRF and grain size data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9276, https://doi.org/10.5194/egusphere-egu2020-9276, 2020
Temperature cycles with periods > 2000 yr, including peaks of order 6000 yr, has been reported in 14C proxy records in sediments for Fennoscandia (Olsen et al, 2005) and in glacier geochemistry for the Greenland ice-sheet (Mayewski et al, 1997, 2004). Similar spectral peaks are also seen in 14C and 10Be isotopes in Greenland GRIP ice-cores (Xapsos, 2009); these cycles have been attributed to solar sunspot activity (Solanki et al, 2004). Complicating the question of existence of global millennial cycles, a comparison of d18O data in ice cores for Greenland (NGRIP) and Antarctica (EDML) has shown that for events prior to the Last Glacial Maximum (LGM), variations on the scale of 2-6kyr are markedly stronger in northern hemisphere records, associated with ice dynamics and Dansgaard–Oeschger (D-O) and Heinrich events (EPICA, 2006).
This paper discusses ocean sediment cores from three temperate zone and sub-tropical sites which provide sea-surface temperature (SST) histories using the UK37 proxy. The available time spans are 20, 70 and 136 ka. This study restricts the three records to 0-20ka thus avoiding complexities of D-O and Heinrich events, and of the associated phase changes between hemispheres which have been discussed by EPICA (2006). We apply Lomb-Scargle spectral analysis and find that all three sediment SST records (Okinawa Trough, Murray Canyon south of South Australia, and Iberian Margin) show a high-confidence 6000 yr period spectral peak for the time span 0-20ka; we may conclude that this post-LGM peak is unlikely to be related to glacial-epoch ice dynamics. The same 6000 yr spectral peak also shows in 0-20ka EDML d18O data from EPICA (2006).
The three SST records also show spectral peaks in the range 1000 to 3500 yr periods. The high-resolution Okinawa Trough shows a clear 2300 yr (Hallstatt) peak and the Iberian Margin similarly. The peak is visible on southern hemisphere Murray Canyon data but is of doubtful significance. A unique feature of the Iberian Margin data is a strong 3400 yr spectral peak. This peak is also visible but much weaker on the other SST records, and on the 0-20ka EPICA d18O data. We hypothesize the strong peak for the Iberian Margin is a consequence of effects of ocean and ice dynamics in the north Atlantic.
Similar spectral analysis of limited 10Be data from McCracken et al 2013, (available length limited to 0-10ka) supports the hypothesis that millennial cycles in temperature (especially the 6000 yr and 2300 yr periods) are global and associated with cosmic ray/solar magnetic activity. This is in contrast with the longer Milankovich cycles which are well established as being primarily related to forcing associated with variable solar insolation.
How to cite:
Asten, M.: Holocene 6000-yr climate cycles in temperate and sub-tropical SST records – a cosmic ray connection?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7285, https://doi.org/10.5194/egusphere-egu2020-7285, 2020
Julia Gottschalk, Robert F. Anderson, Adam P. Hasenfratz, Bärbel Hönisch, Samuel L. Jaccard, Jerry F. McManus, Luke C. Skinner, Claire Waelbroeck, and Gisela Winckler
Interglacial climate conditions are generally characterized by relatively strong and persistent deep-water formation both in the North Atlantic and in the Southern Ocean, and overall ‘stable’ climate conditions. Recent evidence, however, challenges the notion of persistent deep-water formation in both hemispheres during the last interglacial, and points at rapid reductions in convective mixing that may have lasted few centuries to millennia. The spatial pattern of this phenomenon and its driving mechanisms remain poorly constrained. Here we present multi-proxy data for rapid reductions in bottom water oxygen in the central sub-Antarctic Atlantic (sediment core MD07-3077, 44°9.20’S, 14°13.69’W, 3776 m water depth) during the warmer-than-present period of the last interglacial (i.e., 132-116 kyr before present). The first of these “stagnation events”, as they are often denoted, is synchronous, within dating uncertainties, with a similar drop in bottom water oxygenation at a more southern site, ODP Site 1094, south of the Polar Front. Our findings hint at a widespread and significant change in the formation rate and/or end-member pre-formed oxygen levels of Antarctic bottom water (AABW) in the South Atlantic during the last interglacial. The onset of these events closely coincides with increases in sea surface temperatures in the sub-Antarctic Atlantic above average Holocene levels. Although this needs to be further tested at more proximal sites, we argue that stagnation events were likely driven by excess ocean warming, in particular below ice shelves in the Weddell Sea, that may have perturbed AABW formation and/or air-sea gas exchange in that region during the last interglacial. Our findings highlight important feedback mechanisms linking hydrographic conditions at the sea surface, instabilities of the local cryosphere, and the strength of deep water formation in warmer-than-present climate scenarios – the full understanding of which has relevance for assessing the trajectory of future changes in the Southern Ocean.
How to cite:
Gottschalk, J., Anderson, R. F., Hasenfratz, A. P., Hönisch, B., Jaccard, S. L., McManus, J. F., Skinner, L. C., Waelbroeck, C., and Winckler, G.: Perturbations in Antarctic bottom water formation in the Atlantic sector of the Southern Ocean during the last peak interglacial period, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12830, https://doi.org/10.5194/egusphere-egu2020-12830, 2020
Carmen Argenio, Pierluigi Palladino, José Abel Flores Villarejo, and Filomena Ornella Amore
During the past 25 ky, the Earth system underwent a series of dramatic climate transitions until the most recent glacial period. It peaked about 21 ky ago during the time interval known as “Last Glacial Maximum” (LGM). This study focuses on the reconstruction of global changes occurred from the LGM to the Holocene.
For this aim coccolithophore assemblages have been studied at Integrated Ocean Drilling Program (IODP) Site U1385 (37°34.285’N, 10°7.562’W, 2578 m below sea level) located on the continental slope of the southwestern Iberian Margin in a timeframe between 25 and 0 ky. Moreover, an integration with isotopic and biogeochemical data and a comparison with other proxies were carried out.
This IODP Site nowadays is influenced by the Portugal Current system (Pérez et al., 2001; Relvas et al., 2007), whose seasonality is driven by migrations of the semi-permanent subtropical Azores High pressure system (Coelho et al., 2002). The study area also undergoes intra-seasonal oscillations mainly related to changes, during winter, of westerly wind prevalence, induced by the North Atlantic Oscillation (Trigo et al., 2004).
Coccolithophore data were carried out by sediments from the first four sections of the core A of the IODP Site U1385. Coccolithophores, haptophyte algae living in the photic zone, are sensitive to some environmental parameters as temperature, salinity, availability of nutrients and sunlight. Thanks to their ecological sensitivity, coccolithophores are able to record paleoceanographic changes and for this reason are considered to be an important proxy to study the climate variability.
The age model was calculated using linear interpolation between 64 tie points based on log (Ca/Ti) records of Site U1385 and MD01-2444 (Hodell et al., 2015; Datema et al., 2019) and on δ18O records of Site MD01-2444 and Greenland (Hodell et al., 2013). About 500 samples were sampled and preliminary results are based on the analysis of samples with a time-resolution of about 0,3 ky.
The preservation of the assemblages is from good to moderate (Flores et al., 2003). For quantitative analyses, a minimum of 300 coccoliths was counted per slide in a varying number of visual fields using a light microscope at 1000x magnification. This allows a 95% level of confidence to be reached for all species present in at least 1% abundance (Patterson and Fishbein, 1989). Absolute abundance (coccoliths per gram of sediment) and nannofossil accumulation rate (NAR; coccoliths cm-2 ka-1) were estimated following Flores and Sierro (1997).
The preliminary results highlight a progressive increase of small Gephyrocapsa and a decrease of Emiliania huxleyi, between 4,26 ky and 0,91 ky. Moreover, most abundant species, in this interval, are Gephyrocapsa oceanica, Umbilicosphaera sibogae and Calcidiscus leptoporus. Furthermore, between 18,40 ky and 14,72 ky a significant increase of E. huxleyi > 4 µm and G. mullerae occurs associated with a decrease of small Gephyrocapsa and E. huxleyi.
How to cite:
Argenio, C., Palladino, P., Flores Villarejo, J. A., and Amore, F. O.: The Last Glacial Maximum and Holocene along the western Iberian Margin: paleoceanographic and paleoclimatic analyses preliminary results, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3496, https://doi.org/10.5194/egusphere-egu2020-3496, 2020
Long chain n-alcohols and n-alkanes in core sediments from the northern South China Sea (SCS) were measured to make a comparison during terrestrial vegetation reconstruction from ~42 to ~7 ka. The results showed that terrestrial vegetation record from long chain n-alkanes matched well with previous studies in nearby cores, showing more C4 plants developed during the Last Glacial Maximum (LGM) and C3 plants dominated in the interglacial period. However, these scenarios did not occur during terrestrial vegetation reconstruction using long chain n-alcohols, i.e., showing C3 plant expansion during the LGM. The discrepancy during the interglacial period could be likely attributed to aerobic degradation of functionalized long chain n-alcohols due to the oxygen-rich SCS bottom water, resulting in the weak response of terrestrial vegetation signals. On the other hand, the difference between functionalized n-alcohols and non-functional n-alkanes to record local and distal vegetation signals, respectively might be a potential interpretation for the contradiction during the LGM when the SCS was characterized by low-oxygen deep water. Nevertheless, large variations on n-alkyl lipid compositions in C3/C4 plants could likely play a part in modulating sedimentary long chain n-alcohols and n-alkanes towards different vegetation signals, and caution must be taken in respect to the terrestrial vegetation reconstruction using long chain n-alkanes and long chain n-alcohols.
How to cite:
Mao, S., Zhu, X., Sun, Y., Liu, L., and Wu, N.: Last glacial terrestrial vegetation record of leaf wax n-alcohols in the northern South China Sea: Contrast to scenarios from long chain n-alkanes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12293, https://doi.org/10.5194/egusphere-egu2020-12293, 2020
Calcareous stromatolite crusts overgrowing beach gravels and stabilising piles of rocks were observed on shoreline terraces of Lake Lisan along the eastern coast of the Dead Sea. The stromatolite crusts are thick, massive and hard, with a dark-grey or white-grey finely-laminated structure, indicating that they are mostly calcareous organic build-up of cyanobacterial origin. Samples from these stromatolites have been analyzed using Stable Isotopes (δ13C & δ18O), AAS and XRD analysis. The samples range in altitude between -350 m and -19 m, representing the time interval of Lake Lisan (~ 80-19 ka BP) according to our U/Th dating. Since stromatolites grow in shallow water, they are very sensitive to minor shifts in rainfall and evaporation and therefore an excellent tool to track small changes in hydrology, in climate and in paleoenvironmental conditions of the lake basin.
Oxygen and carbon isotopic compositions of these stromatolites show a linear covariant trend with a strong positive correlation (r = 0.8) and large ranges of 7.85 and 6.78‰, respectively. This trend is most typical of primary carbonates formed in closed lakes. Isotopes analyses show low negative values of stromatolites from the lake highest stands at -76 m to -19 m, reflecting fresh water conditions of the lake basin at the last interglacial-glacial boundary (80-76 ka BP). The lowest values were derived from stromatolites at -103 to -119 m associated with the transgression of the lake to these high stands between 55 and 33 ka BP. The heaviest values were derived from stromatolites at -137 to -160 m indicating a change to dry climatic conditions in the Eastern Mediterranean that caused a subsequent drop of the lake level during MIS 2 (31-19 ka BP).
The Mg/Ca ratio and the XRD analysis of the stromatolites correlate also with transgression-regression phases of the lake. Dominance of calcite in stromatolites at -76 to 0 m and inferred low Mg/Ca ratios of the lake water (i.e. ~2) imply a high fresh water input of the lake during the highest stands period. A high Mg/Ca ratio of the lake water of >7 inferred from low-level stromatolite at -350 m and the existence of aragonite as the sole mineral reflect low fresh water input and high evaporation rates that caused a lake level regression during H6, ~ 60 ka BP.
Inferred low Mg/Ca ratios of stromatolites at -247 to -101 m and the existence of calcite as a main mineral phase indicate wet climatic conditions of the eastern Mediterranean and lake level transgression to higher than -137 during MIS 3. The appearance of more aragonite in stromatolites at -137 to -154 m and the inferred high Mg/Ca ratio of the lake water points to a return to dry climatic conditions that caused a regression of Lake Lisan between 32 to 22 ka BP (MIS 2). However, the change in the mineral composition to pure calcite at -160 m in addition to the inferred low Mg/Ca ratio correlates well with the transgression of the lake to this level by the end of the LGM.
How to cite:
Abu Ghazleh, S. and Kempe, S.: Fluctuations of Lake Lisan (the Dead Sea) during the last glacial: Implications for paleoclimatic changes of the Levant. , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12906, https://doi.org/10.5194/egusphere-egu2020-12906, 2020
Katalin Hubay, Mihály Braun, Sándor Harangi, Mihály Molnár, Krisztina Buczkó, and Enikő Magyari
This study applied bulk sediment geochemistry to reconstruct lateglacial and early Holocene climatic changes in a glacial lakes (Lake Brazi, 1740 m a.s.l. and Lake Lia, 1910 m a.s.l.) in the Retezat Mts. (South Carpathians, Romania). We studied how the changes of chemical element concentration in the sediment can indicate environmental changes, climate variations and human effects. Our aim was to develop analytical methods, which may complement the methodology of routinely applied paleoenvironmental methods and can be used to identify environmental changes in the past and help us reconstruct local and regional processes.
In the Retezat Mts., Southern Carpathians, more than hundred glacial lakes were formed after the last glaciation. These glacial lakes are paleoecologically significant because they are characterized by continuous sedimentation since their origin to the present.
In 2007 and 2008 continuous undisturbed sediment cores were obtained from Lake Brazi and Lake Lia in the Retezat Mts. (Southern Carpathians, Romania) with Livingstone and modified Kullenberg corers. The lowermost part of the sediment cores, covering the period between 9900 and 15 800 cal yr BP, was used for high resolution bulk analysis of major elements (Al2O3, SiO2, TiO2, CaO, MgO, K2O, Na2O, Fe2O3 and MnO). Linear discriminant analysis (LDA) was used to compare a priori classified main chemical groups. Subsamples from the core were priory ordered to “warm” and “cold” groups respectively, according to their age and evidence of cold and warm events in the record, as suggested by proxy correlation with the lateglacial event stratigraphy of North Greenland Ice Core Project (NGRIP). The discriminant function was calculated using concentration of major elements after log ratio transformation. Loss-on-ignition and silicon concentration were not used for the discriminant analysis, but regarded as comparison proxies for checking up the validity of outputs.
The calculated discriminant values are good indicators of changes in sediment caused by climate change, as their values give the cold and warm directions. The “a posteriori” groups can be used to determine the period during which local changes differed from the climate changes in the North Atlantic region. The chemical composition of sediments deposited during the “cold” and “warm” periods shows differences in both sediments. The discriminant scores showed strong correlation with the NGRIP d18O data and with the pollen percentage sum of trees and shrubs.
Discriminant analyses of bulk sediment major oxide chemical data may be a useful tool to identify the impact of climate events upon the nature and composition of materials delivered to a lake basin.
How to cite:
Hubay, K., Braun, M., Harangi, S., Molnár, M., Buczkó, K., and Magyari, E.: Reconstruction of paleoenvironmental changes using geochemical data from South Carpathian Mountains, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13551, https://doi.org/10.5194/egusphere-egu2020-13551, 2020