The session invites contributions presenting an applied as well as a theoretical approach. We welcome papers related to reconstructions (at various time and space scales), fractionation factors, measurement methods, proxy calibration, and verification.
INTIMATE (INTegrating Ice core, Marine and TErrestrial records) is a large, diverse, international scientific network interested in better understanding abrupt and extreme climate changes in the Northern Hemisphere during the Quaternary. INTIMATE’s fundamental approach is the synchronisation and comparison of high resolution palaeoclimate and environmental records based on their independent timescales.
Orals: Wed, 30 Apr | Room F1
This study explores Late Holocene climate variability and environmental transitions in the NW Iberian Peninsula by analyzing organic biomarkers (n-alkanes) and their isotopic signatures (δ¹³C and δD) from two contrasting lake systems: Lake Ocelo, a mountain lake (1517 m a.s.l.) located at a crucial point between the Atlantic and Mediterranean bioclimatic regions, and Lake Doniños, a coastal back-barrier perched lake (2.5 m a.s.l.) within the sub-Atlantic climatic domain. Lakes at varying altitudes provide complementary paleoenvironmental records that capture diverse ecosystem responses to past climate changes across vertical gradients.
In both Lake Ocelo and Lake Doniños, δD values reflect hydrological variability. In Ocelo, long-chain n-alkanes indicate terrestrial vegetation as the main source of organic matter. δD values (~-190‰ to ~-160‰) reflect wetter and cooler conditions during the Older Subatlantic (OSA; ca. 800-200 BCE), the Dark Ages (DA; ca. 300-750 CE) and Little Ice Age (LIA; ca. 1300-1900 CE), contrasted with warmer and drier conditions during the Roman Warm Period (RWP; ca. 200 BCE-300 CE), Medieval Climate Anomaly (MCA; ca. 750-1100 CE) and the Industrial Era (IE; ca. 1850 CE-present). Similary, in Doniños, δD values during the MCA became more positive, suggesting drier conditions. The MCA-LIA transition (ca. 1100–1300 CE) in Ocelo shows a shifts to wetter and cooler conditions, with δD and δ¹³C values declining. In Doniños, between 1200 CE and 1585 CE, δD became more positive, suggesting episodic drying and marine influence, likely linked to increased storminess. Also, δ¹³C rose sharply between 1400 CE and 1550 CE, during the LIA, possibly indicating increased nutrient input associated with climatic fluctuations or marine incursions. After a hiatus spanning 1585-1700 CE, δD stabilized at its most positive levels, marking reduced hydrological variability and arid conditions. Post-1850 CE, δD and δ¹³C trended toward more negative levels, reflecting increased meteoric water input due to wetter climate conditions or anthropogenic watershed. Additionally, the lowering of δ¹³C values during the IE may also reflect the Suess effect from fossil fuel combustion.
In Ocelo, δ¹³C data align with δD trends, reflecting shifts in vegetation composition and water stress, with relative enrichment in δ¹³C during the RWP and MCA suggesting warmer and drier conditions, while more negative δ¹³C during the LIA and DA reflects cooler and wetter conditions.
These findings emphasize the utility of biomarkers in reconstructing regional climate variability and the contrasting responses of mountain and coastal lakes to Late Holocene transitions. Despite their geographical proximity (185 km), both lakes reflect different climatic influences: Lake Ocelo records broader fluctuations linked to its bioclimatic position, while Lake Doniños is influenced by local processes, including marine intrusions and anthropogenic impacts. Similarities include drier conditions during the RWP and MCA in both lakes, while differences emerge during the LIA, where marine influence and storminess played a larger role in Lake Doniños.
This work is supported by Grants PID2019-107424RB-I00 and PID2022-139775OB funded by MCIN/AEI/10.13039/501100011033, with the latter also co-funded by “ERDF A way of making Europe”. Xunta de Galicia also supports this work through projects ED431F 2022/18 and ED431B 2024/03.
How to cite: Fernández-Pérez, U., Bao, R., Schefuß, E., Rodrigues, T., Sáez, A., Raposeiro, P., Prego, R., Carballeira, R., and Hernández, A.: Late Holocene Climate Contrasts in NW Iberian Lakes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11318, https://doi.org/10.5194/egusphere-egu25-11318, 2025.
Recent retrogressive thaw slump activity in the Richardson Mountains (northwestern Canada), induced by climate warming, has exposed a stratigraphic record of landscape evolution and permafrost development since the last glaciation. Horizontal profiles of five relict ice wedges and one rejuvenation-stage (ca. modern) ice wedge were collected from the headwalls of four thaw slumps in the Willow Creek area of the Richardson Mountains to study post-glacial changes in winter climate. The ice wedges contain vertically elongated bubbles, indicating a likely snowmelt origin. δ2H and δ18O measurements, sampled every ~1.5 cm across the profiles (n = 325), fall well within the range of local winter precipitation values, thereby confirming winter precipitation as the probable source water. Detrital plant macrofossils from several pristine ice samples were AMS 14C dated (n = 16) and confirm at least 2 generations of relict wedge ice dating to the Younger Dryas (YD) and Late Holocene; this is only the second study from the Western Arctic to document YD wedge ice. YD wedge ice is ~2.2‰ more negative in δ18O compared to Late Holocene wedge ice, which could be explained by one or a combination of plausible factors: (i) winter temperatures were up to ~5°C colder on average (e.g., assuming a δ18Oprecip-T sensitivity of 0.41‰·°C-1); (ii) a greater proportion of snow fell during the coldest winter months; or (iii) the moisture source region varied in response to changing atmospheric circulation, moderated by the collapse of the last ice sheet. However, no significant difference is observed in dexcess between YD and Late Holocene wedge ice, which may suggest the precipitation seasonality and moisture source region were comparable. Conversely, the rejuvenation-stage wedge ice, which likely formed in the last few decades, is 1.7‰ more positive in δ18O than Late Holocene wedge ice, while dexcess is statistically indifferent. The strong increase in δ18O in modern wedge ice relative to Late Holocene wedge ice reflects the impact of recent Arctic warming, especially in winter, a pattern that has been previously observed in other ice wedge records from the Canadian and Siberian Arctic. In summary, this study provided insights on winter climate variability in the northwestern Canadian Arctic, with a focus on the YD, Late Holocene and recent times, and demonstrates the potential to use ice wedges to further our knowledge of cold-season climate dynamics in the circum-Arctic more broadly.
How to cite: Porter, T., Changulani, A., Opel, T., and Meyer, H.: Younger Dryas and Holocene winter conditions in the Richardson Mountains, Canadian Arctic, reconstructed from precipitation isotopes in relict ice wedges, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13380, https://doi.org/10.5194/egusphere-egu25-13380, 2025.
The Sea of Okhotsk, situated at the northern boundary of the East Asian summer monsoon's domain, represents the southernmost region in the Northern Hemisphere where perennial sea ice develops year-round. It serves as a critical source of ventilation for modern North Pacific Intermediate Water and is highly sensitive to global climate change, making it an ideal natural laboratory for studying environmental changes. Despite its importance, our understanding of the basin-scale environmental evolution of the Sea of Okhotsk remains limited. This study addresses these gaps by compiling paleoenvironmental records from several sediment cores in the Sea of Okhotsk. We recalibrated the age models of these cores to reconstruct the histories of sea surface temperature (SST), sea ice activity, surface productivity, and intermediate water ventilation since 30 ka. Based on the reconstruction, we propose the conceptual modes of environmental evolution: the "glacial type," dominated by sea ice, and the "interglacial type," controlled by both sea ice and ocean currents. During the Last Glacial period (30 - 18 ka), the Sea of Okhotsk experienced low SSTs, extensive sea ice coverage, weak intermediate water ventilation, and reduced surface productivity. In contrast, the Late Holocene (< 6 ka) was characterized by higher SSTs, diminished sea ice, robust intermediate water ventilation, and increased surface productivity, with siliceous ooze being the dominant sediment component. Notably, during the Bølling-Allerød (14.7 - 13 ka) and Preboreal (11 - 9.7 ka) warm periods, the marine environment resembled the "interglacial type" but featured anoxic intermediate waters. During Heinrich Stadial 1 (18 - 14.7 ka) and the Younger Dryas (13 - 11.7 ka), environmental regimes were generally similar to the "glacial type" but with enhanced intermediate water ventilation. Since 30 ka, the evolution of environmental factors in the Sea of Okhotsk has been shaped by external forcings, internal feedbacks, and climate processes at both high and low latitudes, underscoring the complex interplay of factors influencing this dynamic region.
How to cite: Zou, J., Wang, Q., and Shi, X.: Basin-scale environmental changes in the Okhotsk Sea over the last 30,000 years, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5402, https://doi.org/10.5194/egusphere-egu25-5402, 2025.
41Ca (half-life = 99 ka) is a cosmogenic radionuclide that has long been proposed as a promising dating tracer for geological and archaeological samples from Middle and Late Pleistocene [1]. Calcium is abundant and has a residence time of 800 ka in the oceans, much longer than the half-life of 41Ca. This has led to the expectation of a uniform distribution of 41Ca/Ca ratios in oceans around the globe. Ocean deposits acquire the global seawater value of 41Ca/Ca upon the initial formation. Since ocean deposits are shielded from cosmic rays by overlying seawater, no cosmogenic 41Ca is produced as deposits grow older. These conditions are ideal for 41Ca dating of marine deposits.
However, the 41Ca/Ca ratio is typically less than 10⁻15 in the environment, posing significant challenges for their measurements. Recent advances in Atom Trap Trace Analysis (ATTA) [2] have enabled the detection of 41Ca in geological samples [3]. The lowest 41Ca/Ca ratio measured so far is 3 × 10−18, found in a foraminifer sample from the Pacific Ocean.
We measured the 41Ca/Ca ratios in seawater samples from various depths in oceans around the world and mapped the spatial distribution of 41Ca. This work identifies the critical initial 41Ca/Ca value for 41Ca dating of marine deposits. Building on these findings, we performed 41Ca dating on foraminifera and coral samples from the Pacific, South China Sea, and Southern Ocean, and compared the results with those obtained from other dating methods. Meanwhile, we are exploring the feasibility of applying 41Ca dating to other geological and archaeological samples.
References:
[1] Raisbeck, G., Yiou, F. Possible use of 41Ca for radioactive dating. Nature 277, 42–44 (1979).
[2] A Primer on Atom Trap Trace Analysis (ATTA). http://atta.ustc.edu.cn/en-us/events/attaprimer.html
[3] Xia, TY., Sun, WW., Ebser, S. et al. Atom-trap trace analysis of 41Ca/Ca down to the 10–17 level. Nat. Phys. 19, 904–908 (2023)
How to cite: Sun, W.-W., Bender, M., Huang, E.-Q., Huang, H., Jiang, W., Lu, Z.-T., Tian, J., Xia, T., Yan, Y.-Z., Yang, G.-M., and Zhu, H.-M.: 41Ca dating of marine deposits from Middle and Late Pleistocene, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4937, https://doi.org/10.5194/egusphere-egu25-4937, 2025.
The last deglaciation represents a valuable test case for understanding abrupt climate events as it triggers cascading feedback among Earth system components, particularly involving the ice sheets. Constraining the timing, magnitude, and order of these events within the critical North Atlantic realm remains challenging.
Here, we present a new U-Th-dated stalagmite from northwestern Iberia spanning the Last Glacial Maximum (LGM) and the entire last deglaciation (24-12 ka BP). Given its coastal and moisture-replete cave location, stable isotopes (δ18O, δ13C) capture both the influence of the Northern Hemisphere ice sheet’s meltwater inflow on surface ocean chemistry, and regional surface air temperature changes via their effects on local vegetation. Since both stable isotopes are measured on the exact same samples, this allows a direct and high-resolution study of the temporal relationship between Northern Hemisphere meltwater ocean in-flux and temperature change in the North Atlantic realm, advancing speleothem applications in ocean and cryosphere studies.
We have compared our results to meltwater histories derived from the ice sheet model GLAC-1D, and our findings confirm/reveal gradual meltwater inflow during the LGM and early deglaciation (~20.8-18.2 ka BP), followed by a set of abrupt increases in meltwater starting at 18.04±0.16, 16.22±0.24 and 15.44±0.19 ka BP. In our record, abrupt cooling begins at 17.18±0.16 ka BP, indicating that the peak weakening of deep Atlantic convection lagged the first abrupt meltwater pulse by ~850 years. This suggests a non-linear connection between surface ocean freshening and the consequential disruption to the early deglacial Atlantic meridional overturning circulation. In contrast, a brief cooling phase, synchronous with a response in global archives, aligns with the meltwater pulse at 16.22 ka BP, whereas no cooling is associated with the 15.44 ka BP pulse. The transition into the Bølling-Allerød period, featuring two warm phases, is marked by rapid warming starting at 14.78±0.12 ka BP concurrent with a decline in meltwater anomalies, likely related to the re-strengthening of deep Atlantic convection. Remarkably, our record does not show a freshwater signal coincident with the classically cited onset of MWP 1a (~14.6 ka BP), suggesting that this event happened earlier or that the freshwater anomaly was rapidly advected out of the surface North Atlantic by a strong AMOC.
How to cite: Endres, L., Pérez-Mejias, C., Ivanovic, R., Gregoire, L., Hughes, A., Cheng, H., and Stoll, H.: North Atlantic Freshening and Abrupt Cooling During the Last Glacial Maximum and Deglaciation recorded by Iberian Speleothem, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16107, https://doi.org/10.5194/egusphere-egu25-16107, 2025.
Conturines cave opens at 2775 m a.s.l. in the Dolomites (Northern Italy), hundreds of meters above the modern tree line. The cave is about 200 m long and comprises a single ascending paleophreatic conduit. The entrance of the cave is located at the base of the headwall of a former glacial cirque, testifying its pre-Pleistocene origin. Large parts of the cave floor are covered by an extensive (up to 3.5 m thick) flowstone and large stalagmite formations are present in the inner part of the passage, where the flowstone starts. All these large formations are inactive, partly corroded and dissected by fractures. The catchment area is a sharp ridge devoid of vegetation and soil, and the dripping water in the cave is undersaturated with respect to calcite, leading to the slow demise of these large speleothems.
Several drill cores covering the entire stratigraphy of the flowstone were obtained along the course of the gallery, the longest reaching bedrock at 3.5 m depth. Multi-proxy analyses of the two longest cores drilled approximately 5 m apart in the proximal part of the flowstone replicate well. Multiple magnetic reversals are preserved in the flowstone stratigraphy. According to preliminary U-Pb dating, speleothem deposition began ca. 5.5 - 5.0 Ma ago, likely coincident with the end of the Messinian Salinity Crisis in the Mediterranean, and continued intermittently until around 3 Ma. This uplifted ancient speleothem record provides a rare window into the Neogene at high resolution.
How to cite: Spötl, C., Koltai, G., Scholger, R., Wang, J., Knipping, M., and Cheng, H.: Ancient speleothem giant preserved in a high-Alpine cave (Dolomites, N Italy): rare insights into the Neogene, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9061, https://doi.org/10.5194/egusphere-egu25-9061, 2025.
LA-ICP-MS, and XRD were used to investigate representative samples of gypsum collected from four deposits, all of them of Badenian age: Cheia (Transilvanian Basin, Cluj county), Ivancauti (Moldavian Platform, Botosani county), Negresti (Moldavide, Neamt county) and Moinesti (Moldavide, Bacau county) deposits were selected. The main objective of this study consisted of a geochemical, crystallo-chemical and economical potential detailed characterization of these deposits.
Accordingly, the LA-ICP-MS permitted determining the mass fractions of 21 elements including 10 REE (La, Ce, Nd, Sm, Eu, Gd, Er, Yb and Lu), as well as of Mg, P, Ti, Fe, Ni, Sr, Y, Ba, Pb, Th and U. Their content was interpreted considering their presence in the upper continental crust (UCC), sea water and chondrites.
Concerning the investigated elements, excepting for the REE ones, the LA-ICP-MS determinations evidenced in the case of Sr and U contents comparable with the UCC ones. It worth mentioning the presence of Sr of which mass fractions of 930 ± 47 and 545 ± 100 mg/kg in the Ivancauti and Cheia samples exceeded the UCC one of 330 mg/kg by a factor up to three, in good agreement with reported data concerning the lagunar Mediterranean gypsum.
At its turn, the U showed mass fractions varying between 1.76 ± 0.94 mg/kg in the case of Moinesti deposit and 2.93 ± 0.8 mg/kg for the Cheia samples, having the same order of magnitude as the UCC one of 2.7 mg/kg. On contrary, the maximum value of Th mass fraction of 68 ± 31 mg/kg was 155 times smaller than the value reported for UCC one. By comparing the ratio of the mass fractions of Th and U in investigated samples with the same ration of the sea water, the gypsum samples ratio of 0.02 significantly overpasses the sea water ratio of 0.0015, suggesting rather a terrigenous origin.
The great variability of the mass fractions of the investigated 11 elements makes possible the discriminant analysis of their distribution by considered elements as variable and deposits as cases. Indeed, a Root 2 vs. Root 2 bi-plot evidenced the presence of four clusters, the Negresti and Moinesti ones relatively closer and differing by the Ivancauti and Cheia ones with respect of Root 1, while Root 2 discriminates only the Cheia one with respect with the other three, i.e. Ivancauti, Negresti and Moinesti.
Likely, the investigated REE distribution showed for all of them mass fractions lower with one order of magnitude and more than the corresponding UCC values, e.g., varying from 5.59 ± 2.82 mg/kg for Yb in Ivancauti samples to 0.21 ± 0.04 mg/kg in the case of Lu in Moinesti gypsum. A peculiarity which we observed for all samples consisted of positive Ce and Eu anomalies. If the Ce anomaly could be associated to an oxidative depositional medium, the positive Eu anomaly could be associated to an increased content of Sr, but these facts need more investigations to be elucidated, especially as this anomaly was evidenced for all investigated samples, regardless the deposit.
How to cite: Dumitras, D.-G., Duliu, O. G., Luffi, P. I., Marincea, S., Sirbu Radasanu, D. S., Iancu, A. M., and Persa, D.: Comparative analysis of gypsum from four different deposits of Badenian age in Romania, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10131, https://doi.org/10.5194/egusphere-egu25-10131, 2025.
Radiogenic isotopes are widely used for sediment provenance. Sedimentary processes are often neglected but may influence the radiogenic Sr isotope-based provenance [1]. This study explores the radiogenic Pb-Nd isotopic systematics in fine lithic materials from the critical zone of Deccan Basalt (Raigad, Maharashtra). An insignificant Pb and Nd isotope variability of fine lithic materials (<20 mm, <5 mm, and <2 mm) is highlighted in the soil (n=5) and saprolite (n=10) samples. The fine soil and saprolite materials also show statistically insignificant differences in CIA (Chemical Index of Alteration) irrespective of the grain size. However, the soil materials (206Pb/204Pb 17.422±0.513, 207Pb/204Pb 15.354±0.104, 208Pb/204Pb 37.843±0.409, and eNd –14.4±2.4) are isotopically different as compared to the saprolite materials (206Pb/204Pb 16.823±0.063, 207Pb/204Pb 15.219±0.013, 208Pb/204Pb 37.374±0.056, and eNd –15.7±1.0). The less radiogenic Nd isotopes suggest altered basalt as the source rock composition. Further, the mass balance suggests that one topsoil sample has a significant contribution of ~75–80 % dyke materials exposed nearby. Whereas the other soil samples show <10 % and <6 % contributions from the dyke and UCC-type materials, respectively. These data reaffirms the robust use of Pb and Nd isotopes in sediment provenance.
Reference:
[1] Dasch, E.J., 1969. Strontium isotopes in weathering profiles, deep-sea sediments, and sedimentary rocks. Geochimica et Cosmochimica Acta, 33(12): 1521-1552.
How to cite: Sahu, S., Singh, S. P., and Joshi, K. B.: Radiogenic Pb and Nd isotopic variability of fine lithic materials in weathering profiles of Deccan Trap, India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-764, https://doi.org/10.5194/egusphere-egu25-764, 2025.
Despite prolonged research, the formation environments of dolomite remain debated. Previous studies have associated the apparent decrease in dolomite abundance during the Cenozoic with a global transition in marine carbonate depositional environments leading from warm, saline, shallow platforms in which dolomite formation was possibly mediated by microbial activity, to deeper and cooler environments in which dolomite formation was largely inhibited. Others suggested that large volumes of pre-Cenozoic dolomites reflect dolomitization at elevated burial temperatures of these rocks, whereas most Cenozoic carbonate platforms did not reach sufficient thermal maturity. A third, hybrid model suggests that Mg-rich dolomite precursor minerals precipitated in shallow environments and later underwent deep diagenesis to a more ordered and stoichiometric dolomite. The combination of carbonate oxygen (δ18O) and clumped (TΔ47) isotope analysis can be used to constrain and distinguish among these formation environments.
Here, we combine δ18O and TΔ47 measurements in marine carbonate rocks from the Triassic Ramon Gr. in Makhtesh Ramon, southern Israel, to constrain their formation environments. The studied section records a transition from a carbonate platform, dominated by fossil-rich limestone (top Gvanim and Saharonim Fm.), to a shallow saline evaporitic lagoon (Mohila Fm.) dominated by alterations of laminar dolomite and evaporitic gypsum, with much sparser fossils relative to top Gvanim and Saharonim Fm. Calcite samples in the Gvanim and Saharonim Fm. recorded δ18O and TΔ47 values from -8.41 to -2.17 ‰ VPDB, and from 29 to 98 °C, respectively. Two calcite samples recorded TΔ47 values of 152-231 °C, associated with isotopic solid-state reordering in response to local heating near igneous intrusions. Dolomite samples at the top Saharonim and Mohila Fms. recorded δ18O and TΔ47 values from -4.77 to -1.59 ‰ VPDB and from 36 to 74 °C, respectively. These results indicate that carbonate minerals recrystallized in burial-diagenetic environments in an open system with respect to δ18O. The observation that dolomite, associated by stratigraphic context and texture with deposition at (or near) the surface, has been recrystallized at depth, supports a multi-step dolomite formation process, in which carbonates were first enriched in Mg2+ in the lagoon and later recrystallized in high-temperature, deep-diagenetic environment.
How to cite: Cooper-Frumkin, S., Affek, H., Ebert, Y., and Ryb, U.: Clumped isotope constraints on formation environment of Triassic carbonates in Makhtesh Ramon, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13426, https://doi.org/10.5194/egusphere-egu25-13426, 2025.
Palaeoclimatic reconstructions rely heavily on accurate interpretation of isotopic signal, retrieved primarily from fossil biominerals. Evaluating whether these geochemical proxies reflect original environment is often a challenge. In our recent study we have attempted to illustrate fossil vertebrate dental tissue geochemistry and, by inference, its extent of diagenetic alteration, using quantitative, semi-quantitative and optical tools to evaluate bioapatite preservation. Here we present visual comparisons of elemental compositions in fish and plesiosaur dental remains ranging in age from Silurian to Cretaceous, based on a combination of micro-scale optical cathodoluminescence (CL) observations (optical images and scanning electron microscope) with in-situ minor, trace and rare earth element (REE) compositions (EDS, maps and REE profiles), as a tool for assessing diagenetic processes and biomineral preservation during fossilization of vertebrate dental apatite. Tissue-selective REE values have been obtained using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), indicating areas of potential REE enrichment, combined with cathodoluminescence (CL) analysis. Energy dispersive X-ray spectroscopy (EDS) mapping was also used to identify major elemental components and identify areas of contamination or diagenetic replacement. We conclude that the relative abilities of different dental tissues to resist alteration and proximity to the exposure surface largely determine the REE composition and, accordingly, the inferred quality of preserved bioapatite.
How to cite: Žigaitė-Moro, Ž., Cowen, M., de Rafélis, M., Ségalen, L., Kear, B., and Dumont, M.: Visualizing and quantifying biomineral preservation in fossils, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5723, https://doi.org/10.5194/egusphere-egu25-5723, 2025.
Stable water isotopes (δ18O) in precipitation are one of the most abundant paleoclimate proxies and have been used to infer temperature changes at high latitude and hydrological changes in the tropics. In spite of much progress, however, fundamental questions on the paleoclimate interpretation of stable water isotopes still remain open. Combing water isotope observations and an isotope-enabled TRAnsient ClimatE simulation of the last 21,000 years (iTREACE-21), I will discuss some recent progresses towards the understanding of paleoclimatic inferences of δ18O.
I will first discuss the δ18O for the pan-Asian monsoon region. We show that the widespread δ18O variability that is coherent over the Asian monsoon continental region is accompanied by a coherent hydroclimate footprint, with spatially opposite signs in rainfall. This footprint is generated as a dynamically coherent response of the Asian monsoon system to meltwater forcing and insolation forcing, reinforced by atmospheric teleconnections. As such, a widespread δ18O depletion in the Asian monsoon region is accompanied by a northward migration of the westerly jet and enhanced southwesterly monsoon wind, as well as increased rainfall from South Asia to northern China, but decreased rainfall in southern China.
I will then discuss the temperature effect of polar ice core δ18O, quantitatively, in a new framework called the Unified Slope Equations (USE) that illustrates the general relationship between spatial and temporal δ18O-temperature slopes. The application of USE to the Antarctica in model simulations and observations shows that the comparable Antarctica-mean spatial slope with deglacial temporal slope in δ18O-surface temperature is caused accidentally by the compensation responses between the δ18O-inversion layer temperature relation and the inversion layer temperature itself. This finding further leads us to propose a paleothermometer that is more accurate and robust than the spatial slope as the present day seasonal slope of -inversion layer temperature, suggesting the possibility of reconstructing past polar temperature changes using present observations.
I will finally discuss the climate interpretation of tropical alpine ice core δ18O by combining proxy records with climate models, modern satellite measurements and radiative-convective equilibrium theory. I show that the tropical ice core δ18O is an indicator of the temperature of the middle and upper troposphere, with a glacial cooling of ~7oC . Furthermore, it severs as a Goldilocks indicator of global mean surface temperature change, providing the first estimate of glacial stage cooling that is independent of marine proxies as ~6oC .
How to cite: Liu, Z.: Understanding Paleoclimatic Inference of Stable Water Isotopes using iTRACE Simulation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1813, https://doi.org/10.5194/egusphere-egu25-1813, 2025.
Future climate projections are expected to have a substantial impact on boreal lake circulation regimes, with warmer climates and higher organic loads leading to intensified thermo-stratification and brownification. Understanding lake sensitivity to warmer climates is therefore critical for mitigating potential ecological and societal impacts. The Holocene Thermal Maximum (HTM; ca 7-5 ka BP) provides a valuable analogue to investigate lake responses to warmer climates devoid of major anthropogenic influences.
In this presentation we present high-resolution micro-X-ray core scanning profiles (μ-XRF) of the annually laminated (varved) sediments from Lake Nautajärvi (NAU-23) in southern Finland to elucidate changes in lake circulation and sedimentation patterns. Principal component analysis (PCA) identifies two key components in the μ-XRF data associated with the nature of the sediments, i.e. detrital vs organic sedimentation (PC1), and hypolimnetic oxidation (PC2). Using these results, we will show that during the HTM, the lake became more sensitive to changes in oxygenation and mixing intensity. These changes were triggered by a warmer climate, which increased organic matter and redox sensitive metal solute concentrations in the water column, strengthening lake stratification and weakening dimictic circulation patterns. Superimposed on HTM weakened circulation are distinct phases of increased oxidation and iron-rich varve formation that do not happen when the background conditions are cooler (i.e. the early and late Holocene). This is driven by temporary strengthening of the mixing regime in response to climatic variability and storminess cycles across southern Scandinavia. These findings demonstrate that whilst warmer conditions weaken boreal lake circulation regimes, they can also make them increasingly vulnerable to short term oscillations in prevalent climatic conditions and weather patterns, which could have significant impacts on lake water quality and aquatic ecosystems. These findings underscore the non-stationary nature of lake sensitivity to short-term climatic variability and emphasize the potential for similar shifts to occur under future warming scenarios.
How to cite: Lincoln, P., Tjallingii, R., Kosonen, E., Ojala, A., Abrook, A., and Martin-Puertas, C.: Heightened instability in lake circulation triggered by mid-Holocene warmth; insights from the varved sediments of Lake Nautajärvi, southern Finland , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11461, https://doi.org/10.5194/egusphere-egu25-11461, 2025.
Understanding the evolution of Holocene climate is key for predicting what different futures may look like. However, global proxy and model-based climate reconstructions disagree on the general evolution of climate over the past 11.7 thousand years. Proxy-based reconstructions demonstrate a Holocene Climatic Optimum in the mid-Holocene, whilst model-based approaches show a trend of increasing temperatures throughout. This disagreement is largely believed to relate to seasonal biases within the proxy-based reconstructions, although model based-reconstructions are not without their flaws. Here we use a series of annually laminated (varved) lake sediment records from Europe (Diss Mere, United Kingdom; Meerfelder Maar, Germany; Lake Nautajärvi, Finland) to explore whether organic proxies are seasonally biased. To achieve this, we generate high-resolution (multi-decadal) branched glycerol dialkyl glycerol tetraether (brGDGT) lipid reconstructions of mean temperature of months above freezing (MAF; approximating MAAT in temperate locations) across the Holocene including the last 200-years and the mid-Holocene. We contrast our biomarker data with chironomid-inferred July summer temperature estimates from the same sample horizons within each lake to ascertain whether summer signals have an important imprint on the GDGT data. We show that brGDGTs are likely produced in situ within lake waters and that the varved nature of each lake does not impede brGDGT based climate reconstruction. We show that 1) GDGT-based temperatures record dominant climate variability at each site; 2) the mid-Holocene is warmer than present and pre-industrial mean annual temperatures; 3) biomarker and chironomid reconstructions from Diss Mere and Meerfelder Maar are more closely aligned than Nautajärvi suggesting location specific complexities; and 4) that biomarker and chironomid temperatures converge and diverge at various points in each record. Each of these results suggest seasonal biases exist within the GDGT-based climate reconstructions which may be non-stationary. Our data therefore reveals the need to generate multiple proxy-proxy assessments of climate from different archives to ascertain the influence of mean annual versus summer climate parameters.
How to cite: Abrook, A., Langdon, P., Inglis, G., Brauer, A., Lincoln, P., Ojala, A., and Martin-Puertas, C.: Seasonal bias in temperature-sensitive biomarkers: a multi-proxy assessment of branched GDGT suitability for Holocene climate reconstruction, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11502, https://doi.org/10.5194/egusphere-egu25-11502, 2025.
Variations in the atmospheric production rate of cosmogenic 10Be lead to global changes in 10Be depositional fluxes. This may serve as a powerful tool for synchronizing various paleoclimate archives. For a robust synchronization, however, it is essential to understand the pathways of 10Be from its production in the upper atmosphere to its deposition in sediments and ice. While 10Be is deposited in ice within one to two years after production, its deposition in marine sediments is less direct, complicating its use for synchronization. To address this issue, we investigate the response of the authigenic 10Be/9Be ratio in marine sediments to a rapid increase in atmospheric 10Be production. We analyzed the 10Be/9Be ratios of three sediment cores from the Southern Ocean, all under the depositional regime of the Antarctic Circumpolar Current (ACC). We compared these records that encompass the period of the geomagnetic field minimum around the Laschamps excursion (~41 ka BP) to 10Be records from ice cores. All cores show an increase in the 10Be/9Be ratio during the Laschamps excursion. However, the marine records exhibit site-specific differences in amplitude and response time. We discuss the causes of these discrepancies and the roles of local residence time of Be in the water column, bioturbation of sediments, diagenetic Be fluxes, re-mobilization of sediments, and varying terrestrial Be sources. We argue that the attainable precision of a 10Be-based synchronization depends on the prior knowledge of these factors. Especially, the marine residence time of 10Be sets an upper limit on the achievable resolution from marine sediment 10Be/9Be records and leads to a temporal shift of the recorded 10Be/9Be changes relative to the increase in atmospheric 10Be-production. Additionally, terrestrial input of 10Be can lead to non-production influences on the 10Be/9Be ratio in sediments, even in pelagic settings. Nevertheless, under ideal conditions, marine sediments can capture 10Be/9Be signals that closely align with those in ice cores, highlighting the potential of 10Be/9Be ratios as a future chronostratigraphic tool for the synchronization of marine sediment records with other paleoclimate archives, e.g. ice cores.
How to cite: Loftfield, J., Nowaczyk, N., Lembke-Jene, L., Frederichs, T., Lachner, J., Lamy, F., Rugel, G., Stübner, K., and Adolphi, F.: Potentials and limitations of using cosmogenic Beryllium isotopes for the synchronization of marine sediment and ice cores, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11588, https://doi.org/10.5194/egusphere-egu25-11588, 2025.
The South Asian monsoon (SAM) system significantly influences the hydroclimate of the Indian subcontinent, affecting nearly two billion people. However, much of our paleoclimate knowledge is centered on the summer monsoon (SASM), while the winter monsoon (SAWM) remains poorly understood. This study investigates seasonal monsoon variability during the last deglaciation, focusing on abrupt climate transitions that provide natural experiments for understanding past monsoon dynamics. We analyzed sediment core SO130-289KL from the Northeastern Arabian Sea, a region sensitive to both the SASM and the SAWM. Laminated sediments deposited during the Bølling–Allerød Interstadial (~14,690–12,890 years BP) offer a rare high-resolution archive for reconstructing past climate variability at ~decadal timescales.
To overcome the limitations of traditional analytical techniques, we employed mass spectrometry imaging and hyperspectral imaging, achieving micrometer-scale spatial resolution. SST reconstructions rely on two independent biomarkers: the alkenone-based UK’37 index and the GDGT-based Crenarchaeol-Caldarchaeol Tetraether (CCaT) index. Hyperspectral imaging quantified chloropigments-a as a proxy for primary production, while leaf wax hydrogen (δD C31) and carbon (δ¹³C31) isotopes provide insights into atmospheric moisture and terrestrial vegetation dynamics in lower resolution.
Our results reveal distinct seasonal responses of the SAM system to deglacial climate changes. Alkenone-based SSTs, which are more sensitive to change in SAWM winds, show a progressive weakening of the northeastern boreal winter winds during the Allerød, aligning with a progressive cooling trend in the Southern Hemisphere. This weakening likely reflects a boreal winter (austral summer) northward shift of the Intertropical Convergence Zone (ITCZ) towards the equator driven by decreasing Southern Hemisphere austral summer temperatures. In contrast, CCaT-derived SSTs, linked to SASM wind strength, closely correlate with Northern Hemisphere temperature proxies, demonstrating that SASM variability was primarily controlled by boreal summer conditions.
Seasonal precipitation patterns reconstructed from leaf wax isotopes highlight hydroclimatic changes during the Bølling-Allerød. Lower δD C31 values during the Bølling indicate increased summer precipitation, while the early Allerød more positive δD C31 suggest decrease in precipitation. Following concurrent decreases in δ¹³C31 and δD C31 values during the mid to late Allerød suggest reduced seasonality with enhanced precipitation in both summer and winter.
The reconstructed seasonal evolution of SASM and SAWM has significant implications for other paleoclimate archives, such as speleothem δ¹⁸O values, traditionally interpreted as summer monsoon proxies. Our findings suggest that speleothem δ¹⁸O values reflect a combined signal of summer and winter precipitation. During the Bølling-Allerød, depleted δ¹⁸O values may indicate an increased contribution from isotopically lighter winter precipitation associated with subtropical westerly jets, rather than solely stronger summer monsoon rainfall. The observed decrease in δ¹⁸O values during the late Allerød likely reflects enhanced winter precipitation from isotopically depleted far-distance moisture sources.
Our findings underscore the dual hemispheric influence on the SAM. SASM strength was directly linked to Northern Hemisphere forcing, particularly shifts in Atlantic Meridional Overturning Circulation and associated ITCZ migrations, while SAWM variability was modulated by both Northern and Southern Hemisphere climate changes.
How to cite: Obreht, I., Lückge, A., Mohtadi, M., Zahajská, P., Schefuß, E., Scholz, D., Wörmer, L., Adolphi, F., Grosjean, M., and Hinrichs, K.-U.: South Asian summer and winter monsoon evolution during the last deglaciation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16395, https://doi.org/10.5194/egusphere-egu25-16395, 2025.
The Mediterranean region is highly sensitive to climate change and warms faster than the global average. Models forecast a pronounced drying trend, coupled with an increase in the frequency and intensity of extreme rainfall events. Past Interglacials can be used as analogues to better understand and estimate regional hydroclimatic responses to global warming.
The Lake Van (Eastern Anatolia, Turkey) sediment record, ICDP site 5034, serves as a key archive to reconstruct hydrological changes in the Eastern Mediterranean. This terminal lake is the largest soda lake in the world and has experienced significant lake-level changes over Glacial-Interglacial transitions (~105 m above modern lake levels during MIS5e). Sediments covering the transition from MIS6 to MIS5e are finely laminated and, in parts, even annually laminated or varved. Therefore, these sediments enable detailed analyses of hydroclimatic variability during Termination II through XRF, microfacies analysis, stable isotope analysis, and δD on leaf wax biomarkers.
Within MIS5e, first results show a significant increase in the bulk organic δ13C signal over a period of several hundred years during a stage associated with higher lake levels. This shift aligns with a change in alkenone composition and precedes a change in stratification, as suggested by a transition from varved to non-varved lithology. The external and internal drivers of these changes are further investigated by XRF core scanning, element mapping, and comprehensive biomarker analyses to explore this proxy behavior.
Ultimately, the data obtained will be compared to other lacustrine records, such as the ICDP Core 5017 from the Dead Sea, to contribute to a more comprehensive understanding of regional variations in the hydroclimatic response during this warming phase in the Eastern Mediterranean.
How to cite: Urban, A., Blanchet, C., Sachse, D., Schröder, B., Pinkerneil, S., Schwab, M., Kearney, R., Kwiecien, O., Brauer, A., and Tjallingii, R.: Hydroclimatic variability during the onset of the Last Interglacial in Lake Van and Iimplications for the Eastern Mediterranean , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18756, https://doi.org/10.5194/egusphere-egu25-18756, 2025.
Hydroclimatic variations on the Tibetan Plateau since the Last Glacial Maximum (LGM) are still debated. Here, we reconstruct climatic and hydrological variability in the southwestern Tibetan Plateau since the late LGM using climate proxies based on molecular distributions of n-alkanes, hydrogen and carbon isotopic composition of terrestrial n-alkanes and δ18Ocarbonate at Lake Zabuye. Our findings indicate that the δD-nC31 signal in this lake was primarily influenced by temperature from late the LGM to early deglaciation period, shifting to a predominance of precipitation influence from the Heinrich event 1 (H1) to the Holocene period. In contrast, the carbonate δ18O was found to be primarily governed by evaporative processes. Through comprehensive analysis of all proxies, we suggest that Lake Zabuye was dominated by the mid-latitude Westerlies with cold and moist conditions from late LGM to early deglaciation. The H1 and Younger Dryas (YD) periods were characterized by low temperature and reduced precipitation due to the influence of the moderately intensified Westerlies. The Indian Ocean Summer Monsoon (IOSM) intensified during the Bølling/Allerød (B/A) period, and its strength was comparable to that of the Westerlies, resulting in plentiful rainfall and high evaporation. The IOSM was dominant during the Holocene, characterized by abundant rainfall and high evaporation.
How to cite: Ling, Y., Tian, L., and Bendle, J.: Hydroclimatic Evolution of the Southwestern Tibetan Plateau Since the Last Glacial Maximum Inferred from Multi-Proxy Data in Lake Zabuye, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21525, https://doi.org/10.5194/egusphere-egu25-21525, 2025.
Posters on site: Wed, 30 Apr, 14:00–15:45 | Hall X5
Enhanced chemical weathering in glacial regions, driven by climate change, is projected to increase the delivery of dissolved and particulate matter to the ocean, significantly disrupting biogeochemical cycles of critical elements which exert a strong influence on the global carbon cycle. This study investigates the elemental and Mg isotope geochemistry of meltwater, suspended particulate matter (SPM), and bedrock samples from Ny-Âlesund, Svalbard, in order to elucidate the link between glacial weathering processes and Mg isotope variations within this glacial environment. Magnesium isotopic compositions (δ26Mg) in meltwaters and SPMs exhibit significant variability, in which meltwater δ26Mg values are in isotopic equilibrium with corresponding SPM values, yielding two distinct isotope fractionation factors depending on the drainage lithology.
A global comparison of water δ26Mg values in Arctic rivers reveals that variability in waterδ26Mg can be attributed to two primary factors, which are a global isotopic equilibrium state that is consistent with what is observed in Svalbard, and an influence of drainage lithology (silicates versus dolomite). Globally, riverine Mg, on average, exhibits a consistent Mg isotopic signature that closely resembles that of the upper continental crust, regardless of the diverse environmental conditions encountered by these river systems. This observation strongly suggests that dynamic interactions between erosion and weathering processes rapidly drive the system towards isotopic equilibrium, which is well supported by this study.
Overall, this study highlights that the difference in δ26Mg between waters and SPMs can be used as a novel indicator for predicting weathering disequilibrium induced by global warming and other factors influencing the Earth's surface evolution.
How to cite: Ryu, J.-S., Lim, H. S., Song, H., Kim, O.-S., Yang, M., and Vigier, N.: Factors controlling Mg isotopes in meltwater and suspended sediments of Arctic rivers, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1984, https://doi.org/10.5194/egusphere-egu25-1984, 2025.
Marine ferromanganese polymetallic crusts and nodules are an important mineral resource widely distributed on the seafloor. They are regarded as strategic reserve resources and have attracted much attention. During the mineralization process, the iron-manganese oxide/hydroxide colloids generated by the oxidation of Fe2+ and Mn2+ in the ambient seawater adsorb metal ions and oxidize the metal ions to a high valence state or form metal complexes to be enriched in iron-manganese minerals. They grow slowly at a rate of several mm/Myr, recording and preserving important information on paleo-ocean and paleoclimate changes. They are ideal objects and response media for studying global ocean evolution and environmental changes and are also helpful in exploring the source-sink process of marine substances. Therefore, based on the precise chronology of polymetallic crusts and nodules from the South China Sea (SCS), this study used in-situ Pb isotope analysis technology to analyze the variation characteristics of Pb isotope composition of polymetallic crusts and nodules, to reveal the growth and mineralization history and environmental evolution of crusts and nodules in the study area.
The results show that: (1) The growth ages of SCS polymetallic crusts and nodules are about 1.16-3.46 Ma and an average growth rate of 3.19-6.07 mm/Myr using the 10Be/9Be isotope method. (2) The Pb isotope characteristics of SCS polymetallic crusts and nodules are related to their growth area: the Pb source of crusts and nodules growing in the northern SCS is mainly affected by the input of terrigenous materials; the crusts and nodules growing in the central SCS are less affected by terrigenous materials and are gradually affected by the weathering/alteration of seamount substrates and the input of volcanic activities. (3) Through the coupling of the mineralization chronology framework of SCS polymetallic crusts and nodules with the Pb isotope compositions of their profiles, it is found that the rapid formation and large-scale expansion of the northern hemisphere ice sheet around 3.5 Ma caused the deep water of the SCS to become extremely oxidized, thus promoting the mineralization of SCS crusts and nodules. The tectonic activities in the SCS since 2.8 Ma have had a greater impact on the SCS polymetallic crusts and nodules. Events such as the closure of the Lehe Waterway and the successive closure of the Taitung Waterway have led to the strengthening of the closure of the SCS, the lack of ventilation, and the reduction of oxidation of the seawater, which has slowed the growth rate of polymetallic crusts and nodules. In addition, the uplift of Taiwan and the subsidence of the northern SCS have led to an increase in the input of terrigenous materials, which has led to a decrease in the content of metal elements in the mineralization of polymetallic crusts and nodules. Therefore, the mineralization of SCS polymetallic crusts and nodules is subject to joint control of the tectonic evolution of the SCS and changes in the marine environment such as global climate change.
How to cite: Guan, Y., Ren, Y., Feng, A., and Zhou, X.: Metallogenic environment evolution of the polymetallic crusts and nodules from the South China Sea: Insights from in-situ Pb isotopes and elemental geochemistry, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14366, https://doi.org/10.5194/egusphere-egu25-14366, 2025.
Tracing the sources and transport pathways of marine sediments provides criticle insights into regional atmospheric and oceanic circulation patterns. Strontium (Sr) and neodymium (Nd) isotopes proxies, when applied to thick and well-dated marine sediment cores, offer a powerful tool for evaluating regional climate dynamics over glacial-interglacial cycles. In this study, we present 13 paired Sr and Nd isotope records for each of two size fractions of lithogenic sediments spanning the past 143 ka, collected from the Benham Rise in the western Philippine Sea. Our goal is to assess the contributions of Asian dust and Southeast Asian volcanogenic sediments under varying global climate conditions. Preliminary results indicate distinct isotopic signatures between size fractions. Volcanogenic Sr isotopic ratios (⁸⁷Sr/⁸⁶Sr = 0.705 to 0.707) were found in sediment grain size >20 μm, while more radiogenic strontium isotope signatures (⁸⁷Sr/⁸⁶Sr = 0.709 to 0.711) were found in sediments in the 2–20 μm fraction. The differences in Sr isotopic signatures between size fractions may partly result from the size effect. Coupled with εNd values, although with some fluctuations, we found shifts in sediment sources over the past 134 ka, indicating decreased contributions of Asian dust source towards the Las Interglacial Highstand. These findings contribute to a deeper understanding of sedimentary processes and environmental shifts in the western Pacific region, offering new perspectives on regional climate.
Keywords: Strontium and neodymium isotopes; Marine sediments; source and transport pathways, Last glacial-interglacial cycle
How to cite: Wang, W.-C. and Liu, Y.-W.: Tracing sediment sources in the western Philippine Sea since 143 ka with Sr and Nd isotopes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3043, https://doi.org/10.5194/egusphere-egu25-3043, 2025.
Ursus spelaeus, the Late Pleistocene a cave bear is known from numerous accumulations found in the fossil sector of caves situated in the Carpathian and Apuseni Mountains. In this study, we present approximate population variation in time using the temporal distribution and interval frequencies of radiocarbon ages from literature. Most of the dated skeletons were preserved in caves. The data suggest that, during the entire Marine Isotope Stage 3 (MIS 3) interval, caves were serving as a shelter for U. spelaeus, with the oldest dated bone indicating ages over 60,000 and the youngest ones less than 30.000 years cal BP. Histogram plots of over 110 radiocarbon data from different caves of the Carpathian and Apuseni Mountains as Cioclovina Uscată, Peștera (Cave) cu Oase, Peștera Muierii, or Peștera Urșilor, respectively, show a maximum expansion of the cave bear population between 50,000 and 40,000, a decline between 40,000 and 35,000 and a partial recovery from 35,000–30,000 years cal BP. Radiocarbon data of Homo sapiens remains, younger than 35,000 years cal BP, support the fact that H. sapiens accessed the same caves where the cave bear persisted to hibernate. Besides general cool conditions and restricted food sources, the presence of H. sapiens constituted an additional stress factor driving the cave bear to extinction (Bojar et al., 2024).
References
Ana-Voica Bojar, Natalia Piotrowska, Victor Barbu, Hans-Peter Bojar, Fatima Pawełczyk, Andrei Smeu & Ovidiu Guja: Ursus spelaeus (Rosenmüller, 1794) during the MIS 3: new evidence from the Cioclovina Uscată Cave and radiocarbon age overview for the Carpathians, Isotopes in Environmental and Health Studies, DOI: 10.1080/10256016.2024.2376730
How to cite: Bojar, A.-V., Barbu, V., Piotrowska, N., Bojar, H.-P., Smeu, A., Pawełczyk, F., and Guja, O.: Ursus spelaeus (Rosenmüller, 1794) during the MIS 3: temporal population distributions and relationship with climatic fluctuations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8827, https://doi.org/10.5194/egusphere-egu25-8827, 2025.
The primary aim of our study is to monitor carbon dioxide concentrations and carry out advanced analyses of the carbon cycle through mass spectrometry-based research in the biosphere within an urban environment in the southern region of Poland. Sampling sites within urban agglomerations are crucial for examining both the similarities and differences between urban areas, including the levels of CO2 and their sources. Preliminary findings (Sensuła et al., 2023) suggest that continuous monitoring is essential, and incorporating additional research on carbon isotopes in the air may significantly contribute to understanding the carbon cycle in the studied areas.
In 2022, a new laboratory setup was established in Gliwice (Silesia, Poland) to monitor CO2 levels, enabling precise measurement of CO2 concentrations in the atmosphere. This system allows for high-time-resolution measurements of the CO2 molar fraction, as well as the collection and analysis of air samples. Furthermore, the extraction of CO2 from these samples, followed by 14C analysis via the MICADAS system, provides valuable data on the isotopic composition of both atmospheric and biospheric samples.
This study presents initial results in the form of a database documenting the molar fraction of CO2 and 14CO2 in atmospheric air samples from the urban area of Gliwice, Poland, covering the period from August 2023 to April 2025. CO2 concentrations have been measured using a low-cost system (CARBOCAP GMP-343), while 14C concentrations were determined through the MICADAS technique. Our observations in 2024 indicate that the 14C values in the air samples ranged from -55‰ to -24‰, while the monthly CO2 molar fraction varied between 428 and 469 ppm, depending on seasonal changes.
Additionally, since 2019 till 2024 we have investigated pine needles as potential archives of radiocarbon in contemporary environments. This examination focused on the radiocarbon concentration variations in pine needles of different ages, with thirty needle samples collected seasonally in Gliwice. The 14C concentrations in these samples were determined using a liquid scintillation counter, revealing a mean 14C fraction of 99.83 (69) pMC.
In January 2025, we began calibrating a new system based on the CRDS (cavity ring-down spectrometer) technique to analyze the stable isotopic composition of atmospheric gases (CO2 and CH4).
This work was supported by the following contracts and grants: the Initiative of Excellence – Research University programme implemented at the Silesian University of Technology, in the years 2022-2024 as part of a grant for cutting-edge research grant no.: 14/020 / SDU / 10-21- 03; project title: Analysis of CO2 changes in the atmospheric air: construction of a new module to monitor CO2 concentration in the air; EU funds FSD - 10.25 Development of higher education focused on the needs of the green economy European Funds for Silesia 2021-2027 : The modern methods of
the monitoring of the level and isotopic composition of atmospheric CO2 (project no.FESL.10.25-IZ.01-06C9/23-00) implemented at the Silesian University of Technology (2024-2026).
How to cite: Sensuła, B., Ustrzycka, A., and Michczyński, A.: Dynamics change in carbon cycle in contemporary environment in urban area in Gliwice, Poland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3149, https://doi.org/10.5194/egusphere-egu25-3149, 2025.
The carbon cycle perturbations in geological history are preserved in the form of changes in stable carbon isotope ratios (δ13C values) in different carbon-bearing sedimentary archives. The carbon cycle perturbation that occurred across the Paleocene-Eocene boundary (~56 Ma) is known as the Paleocene Eocene thermal Maximum (PETM). After more than three decades of research, the exact magnitude of the negative carbon isotope excursion (CIE) is still fuzzy. The shallow marine sedimentary archive, deposited far above the lysocline, is considered to be the best archive to quantify the carbon cycle perturbation because the deep marine (carbonate) was likely to be affected by carbonate dissolution and terrestrial sedimentary records influenced by different climatic parameters. However, different biotic and abiotic processes could influence the magnitude of the CIE during the perturbed carbon cycle-climate state in a shallow marine environment. For this reason, the present study investigated the early Paleogene marine carbonate rocks deposited in the eastern Tethyan Sea (Ladakh, NW India) to check the possible presence of the PETM CIE and test whether shallow marine carbonate is a good archive for measuring the CIE magnitude. The presence of age-diagnostic larger benthic foraminifera and detailed micro-facies analysis indicates the investigated shallow marine carbonate rocks were deposited during the ~56 to 54 Ma (Shallow Benthic Zone - 4 to 7) and are likely to hold the PETM CIE. The secular variation in the δ13C values of unaltered bulk carbonate, screened through the cathodoluminescence microscopic study, reveals a PETM CIE magnitude of -3.6 ‰. The observed CIE magnitude is similar to the globally accepted CIE magnitude (-4 ± 0.4 ‰) for PETM and suggests that shallow marine carbonate can be used to assess the magnitude of PETM and other carbon cycle perturbations.
How to cite: Dadabhau Raskar, T., Samanta, A., and Kumar Bera, M.: Can shallow marine carbonate faithfully preserve the true signal of carbon cycle perturbation?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6511, https://doi.org/10.5194/egusphere-egu25-6511, 2025.
The "Shuram Excursion (SE)" stands as the largest known negative carbon isotope excursion (CIE) in geological history and is thought to represent the largest carbon cycle perturbation, possibly pivotal in the evolution of complex life forms and, thereafter, the Cambrian biotic explosion. Apart from the Shuram Formation at its type locality in Oman (the maximum depleted stable carbon isotopic ratio [δ13C value] in carbonate [peak δ13CCarbonate] of ~ –12 ‰), comparable negative CIE of similar ages has also been documented from different parts of the globe, among which the well constrained globally recognized SE sections are the Wonoka Formation of Australia (peak δ13CCarbonate of ~ −10 ‰), the Doushantuo Formation of South China (peak δ13CCarbonate of ~ −14 ‰), and the Rainstorm Member in the Johnnie Formation of Death Valley, California (peak δ13CCarbonate of ~ −11‰). Considering the inherent problem with the exact depositional age estimation for sedimentary rocks, although all the global locations show similar CIE patterns, the peak δ13CCarbonate values, and stratigraphic thicknesses vary from section to section. Because of these disparities, two distinct perspectives exist regarding the origin of the SE. While one group argues that a globally synchronous diagenetic event is responsible for the SE CIE, the other suggests it is a record of the temporal variation in the primary δ13C composition of the seawater dissolved inorganic carbon (DIC) and, hence, represents the actual carbon cycle perturbation. Based on the preliminary data obtained by other studies from the late Neoproterozoic Lesser Himalayan Krol Formation, previous workers tentatively suggested that the succession may contain the SE. However, because of the composite nature of the studied sections and the large spread in carbonate δ13C values in lithologically correlative stratigraphic (temporal) intervals, the proposition was not confirmed. So, the current study tries to recognize the possible SE CIE in the Lesser Himalayan Krol Formation, India, by studying continuously measured structurally undisturbed sections by employing vigorous fieldwork, detailed high-resolution carbonate δ13C data, and Pb-Pb dating of the carbonates after careful thin section and cathodoluminescence (CL) based screening for any possible diagenetic alterations. The transmitted light and CL-based petrographic observation, along with bulk and fabric-specific (micro-sampling) carbonate δ13C data, suggests the presence of distinct negative CIE with a peak δ13CCarbonate value of ~ –10.7 ‰ (CIE magnitude of ~10.7 ‰) in the Lesser Himalayan Krol Formation. The depositional age of ~560 ± 12 Ma, estimated by Pb-Pb dating of the carbonate across this CIE, further suggests the possible presence of SE CIE in the investigated section.
How to cite: Pradhan, D., Bera, M. K., Nandi, A., and Vadlamani, R.: Does the Largest Recorded Negative Carbon Isotope Excursion from the Neoproterozoic Krol Formation (India) Represent a Globally Synchronous Diagenetic Event?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4264, https://doi.org/10.5194/egusphere-egu25-4264, 2025.
Paleoclimate research is important for understanding past, current and future climate, providing the data needed to model and predict current and future climate change scenarios. Stable isotope analysis provides an essential tool for gathering past climate information from natural archives such as waters including ice-cores, ground waters, and biological waters; and carbonate materials such as foraminifera and other fossilized carbonates. Due to the often limited and small sample sizes available for stable isotope analysis it is vital that highly precise and accurate analysis can be carried out on the smallest of sample sizes.
Dual inlet technology remains the most precise, accurate and sensitive technique for pure gas, carbonate and water analysis. The Elementar iso DUAL INLET is a valuable tool for paleoclimate applications, enabling the analysis of pure gas samples within an incredibly compact footprint via our powerful lyticOS software suite. The 14-ultra low dead volume valves with bodies machined from a single block of high purity stainless steel and dedicated turbomolecular pump for the changeover valve guarantees zero residual memory effects between reference and sample gas.
The iso DUAL INLET can be optionally enhanced for the automated analysis of carbonate and water samples. With the iso AQUA PREP enhancement, up to 180 water samples can be analysed achieving δ18O precision better than 0.05‰ (1σ, n=10) and δD precision better than 1‰ (1σ, n=10), for any environmental water sample. The iso CARB PREP enhancement enables automated analysis of up to 180 micro-fossil samples for 13C and 18O down to 20μg sample size. For the highest productivity, both carbonate and water analysis can be performed with the iso MULTI PREP enhancement with switching between modes needing simply a change of needle. The IRMS collector configuration can also be upgraded for “clumped isotope analysis” of carbonate materials.
We will highlight the performance of the iso DUAL INLET with carbonate and water functionality across a range of sample types for paleoclimate applications, supporting researchers building a detailed understanding of the past to better inform policy makers for the future.
How to cite: Seed, M., Preece, C., Rosenthal, K., and Barker, S.: High precision stable isotope analysis of carbonate and water samples for paleoclimate applications using the Elementar iso DUAL INLET, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11350, https://doi.org/10.5194/egusphere-egu25-11350, 2025.
The isotope composition of lake sediments, including gypsum, carbonate, and biogenic silicate, provides a powerful means to reconstruct past hydrological and climatic changes. Triple oxygen isotope measurements in such minerals are an emerging tool for quantitative paleoclimate reconstructions in lacustrine environments. However, robust interpretations of these archives require a detailed understanding of the processes driving lake water isotope variability and mineral formation. Long-term changes in climate and hydrological conditions, especially in semiarid and arid regions, often challenge the interpretation of lacustrine records. Here, we synthesize key findings from multiple studies on the processes controlling triple oxygen and hydrogen isotope variability in semiarid lakes. The presented data include results from several Andalusian wetlands and artificial salt pans in Spain. We explore how factors such as groundwater connectivity, transitions between permanent and ephemeral stages, lake water salinity, climate seasonality, and seasonal and interannual variations in mineral formation influence the isotope composition of lake water and discuss their implications for paleoclimate reconstructions. Our findings provide a framework for interpreting lacustrine archives in complex hydrological settings.
Acknowledgements:
This research was supported by the European Commission (Marie Curie postdoctoral fellowship, grant no. 101063961) and the project PID2021-123980OA-I00 (GYPCLIMATE), funded by the Ministerio de Ciencia e Innovación of Spain, the Agencia Estatal de Investigación and the Fondo Europeo de Desarrollo Regional FEDER.
How to cite: Voigt, C., Gázquez, F., Rodríguez-Rodríguez, M., Jurikova, H., Martegani, L., Cañada-Pasadas, J., and Ruíz-Caballero, E.: Modern isotope dynamics in lakes of semiarid regions: A framework for interpreting lacustrine paleoclimate archives , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15151, https://doi.org/10.5194/egusphere-egu25-15151, 2025.
Nitrogen isotopic composition (δ¹⁵N) measured on organic matter within biominerals (fossil-bound) is an emerging proxy for reconstructing marine trophic conditions in deep time. While previously applied to foraminifera, diatoms, corals, shark teeth, and fish otoliths, the application of δ¹⁵N to other shallow-water marine taxa has been relatively limited. To evaluate the potential of sea urchins as a new model for paleoenvironmental and paleoecological reconstructions, we herein investigate fossil-bound δ¹⁵N in modern and fossil sea urchin biominerals and, for extant samples, its relationship to tissue δ¹⁵N.
Our findings indicate a δ¹⁵N difference of up to 3 ‰ between plates and spines within an individual sea urchin, with an observed nitrogen isotope gradient from the aboral surface to oral surface in both test plates and spines. In addition, we directly compare the δ¹⁵N signature of the gonads, gut content and body wall tissue with the biomineral-bound δ¹⁵N of the teeth, hemipyramids, rotulae, compasses, perignathic girdle, plates and spines. We suggest that biomineral-bound δ¹⁵N preserves trophic signals while also capturing internal isotopic gradients.
Extending this method, we analysed δ¹⁵N in various echinoid genera from the Carboniferous (Mississippian and Pennsylvanian) across multiple localities spanning the globe as a means of understanding their, previously poorly-defined, role in Paleozoic ecosystems. This study is a first step towards the application of fossil-bound nitrogen isotopes to this diverse group, providing new insights into trophic conditions and ecological structures in Paleozoic marine benthic ecosystems.
How to cite: Auderset, A., Bieler, A. L., Martínez-García, A., and Thompson, J. R.: Exploring Fossil-Bound Nitrogen Isotopes in Modern and Paleozoic Sea Urchins: A New Window into Benthic Ecosystems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15935, https://doi.org/10.5194/egusphere-egu25-15935, 2025.
The eastern Mediterranean region experienced large hydroclimatic shifts throughout the Holocene (11.6 ka to present). The region is located between the contrasting humid Mediterranean climate and the Saharo-Arabian desert belt. The important palaeoclimatic record of the Dead Sea (Levant) ICDP Dead Sea Deep Drilling Project (DSDDP) core provides detailed reconstructions into the hydroclimatic variability during this time. However, chronological uncertainties have prevented detailed insight into the regional climatic (a)synchronies with other palaeoclimatic records in the region. The use of tephra horizons as time-synchronous markers can provide insight into the spatial and temporal environmental response of this region to past abrupt climatic change. The identification of a widely dispersed volcanic ash from a volcanic eruption is a particularly powerful chronological tool to be used, as seen with the S1 tephra from Mt. Erciyes (Turkey).
Here, we present the identification of a microtephra layer, visible only in thin section analysis, within varved sediments of the Dead Sea DSDDP record. Using major, minor and trace element analysis, this tephra has been identified as the S1 tephra. Though the S1 tephra has been found in the Dead Sea Ein Gedi shallow water core before (Neugebauer et al., 2017), this is the first time a ‘visible’ tephra layer has been found in the deep ICDP sediment lake record. Through thin section micro facies and XRF analysis, we can now confirm the season of the S1 eruption from Mt. Erciyes happened during the winter. The discovery of the S1 tephra in the well-dated part of the DSDDP record and at other sites across the Mediterranean, we have used Bayesian age-modelling to refine the age for this key tephrostratigraphic marker. As a result, this will enable further detailed insights into the timing of the African Humid period across the eastern Mediterranean region during the early Holocene.
How to cite: Schwab, M. J., Kearney, R. J., Pflug, K., Blanchet, C., Neugebauer, I., van Schijndel, V., Appelt, O., Tjallingii, R., and Brauer, A.: Chronological and seasonal constraints for the Holocene S1 tephra in the Eastern Mediterranean, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19988, https://doi.org/10.5194/egusphere-egu25-19988, 2025.
This study presents a reconstruction of Holocene mean July air temperatures based on chironomid assemblages preserved in the sedimentary record of Laguna de la Mosca (LdlMo), an alpine lake in the Sierra Nevada of southern Spain. The LdlMo record reveals that the highest temperatures occurred during the Early and early-Middle Holocene, between 8500 and 7000 cal yr BP, followed by a significant cooling event. During the Middle Holocene, temperatures stabilized, but a second major cooling event occurred at approximately 4200 cal yr BP, possibly associated with the 4.2 kyr event. Throughout the Late Holocene, temperatures generally remained low, punctuated by warming episodes between 2300–1600 cal yr BP during the Iberian Roman Humid Period (IRHP) and around 1000 cal yr BP during the Medieval Climate Anomaly (MCA). The lowest temperatures were recorded at the end of the Little Ice Age (LIA), circa 1800 CE. Since ~1955 CE, a rapid and pronounced warming trend of 2.5°C has been observed, driven by anthropogenic climate change. This study shows the amplification of recent warming at high elevations, highlighting the vulnerability of these fragile and unique alpine environments to the impact of climate change.
This work was funded by grants BIOD22_001 and BIOD22_002, funded by Consejería de Universidad, Investigación e Innovación and Gobierno de España and Unión Europea – NextGenerationEU and PID2021-125619OB-C21 funded by the Ministerio de Ciencia e Innovacion of Spain, the Agencia Estatal de Investigacion and the Fondo Europeo de Desarrollo Regional FEDER MCIN/AEI/10.13039/501100011033/FEDER, UE
How to cite: Jiménez-Moreno, G., Prats, N., Heiri, O., García-Alix, A., Anderson, R. S., Jiménez-Espejo, F. J., and Pérez-Martínez, C.: Chironomid-based Holocene summer temperature dynamics from southern Spain , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3260, https://doi.org/10.5194/egusphere-egu25-3260, 2025.
Posters virtual: Fri, 2 May, 14:00–15:45 | vPoster spot 5
EGU25-12407 | ECS | Posters virtual | VPS7
A Multi-Proxy Approach to Reconstructing Long-Term Climate and Environmental Dynamics in the Canary Islands: Inter-Island ComparisonsFri, 02 May, 14:00–15:45 (CEST) | vP5.7
The Canary Islands, located in the central North Atlantic, provide an exceptional setting for investigating long-term climate dynamics within the Macaronesian region. This study presents sedimentary records from volcanic lacustrine basins across Tenerife, La Gomera and La Palma, analyzed using a multi-proxy approach including magnetic susceptibility, XRF geochemistry, elemental composition (TOC, TN, TS), mineralogy, lipid biomarkers, and updated age models. Preliminary age models suggest that the sequences of La Vega Lagunera (northern Tenerife) extend back up to 400,000 years, and El Malpaís de La Rasca (southern Tenerife), Garajonay (La Gomera), and Playa de Taburiente (La Palma) span the Holocene.
Preliminary results from La Vega Lagunera, a Pleistocene clastic lake, indicate colder conditions during MIS 2 and MIS 4, warmer conditions during the Holocene, MIS 3, and MIS 5, and millennial-scale cycles during MIS 3 and MIS 4. Climate during the Last Glacial Maximum (MIS 2) was notably drier, resembling mid-latitude records.
Holocene records from paleolacustrine deposits of two closed-drainage basins located in two volcanic craters (La Gomera and Malpaís de La Rasca) and the lacustrine-marsh system of Playa de Taburiente showed coherent patterns of Holocene regional climate variability, with increased fluvial and alluvial activity during the Greenlandian (11.7 to 8.2 ka), a decline during the Northgrippian (8.2 to 4.2 ka), and reduced clastic input during the Meghalayan (last ~4.2 ka). These trends suggest increasing aridity throughout the Holocene.
These new sedimentary sequences from Tenerife, La Gomera, and La Palma provide further evidence of rapid climate dynamics during glacial and interglacial intervals. Improved age models (OSL, 14C) are still being developed to characterize the cyclic patterns better, while multi-proxy analyses are enhancing our understanding of past climate dynamics. Further research is needed to clarify the roles of regional climate and local factors.
This work is supported by TED2021-129695A-I00 project funded by MICIU/AEI/10.13039/501100011033 and by the European Union NextGenerationEU/PRTR; PALEOMOL (2915/2022) and IVRIPARC (2779/2021), both funded by the Spanish National Parks Organism, and IMPACT (2022CLISA04, Fundación CajaCanarias and Fundación La Caixa).
How to cite: Ocón-Bermúdez, C., Galofre-Penacho, M., Valero-Garcés, B., Armenteros-Armenteros, I., Herrera-Herrera, A., Égüez, N., Martín-Luis, M. C., Casillas Ruiz, R., Vegas, J., Castellano-Rotger, L., Diez-Herrero, A., Casado-Vara, R., and Jambrina-Enríquez, M.: A Multi-Proxy Approach to Reconstructing Long-Term Climate and Environmental Dynamics in the Canary Islands: Inter-Island Comparisons, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12407, https://doi.org/10.5194/egusphere-egu25-12407, 2025.
