Orals: Fri, 2 May | Room 0.31/32
Antarctic Intermediate Water (AAIW) plays a key role in the global carbon cycle, but its contribution to past CO2 variability in the past is still poorly understood. Using multi-proxy paleoceanographic reconstructions (foraminiferal Mg/Ca, ∆47, δ18O) from the South Pacific sector of the Southern Ocean, we investigate changes in AAIW’s physical properties across the Mid-Brunhes Event (MBE), a major atmospheric CO2 transition. Our results reveal a contrasting evolution within the Subantarctic Pacific: while surface ocean temperatures remained relatively stable over the past 600 ka, the subsurface experienced a marked shift in AAIW properties across the MBE towards warmer and saltier conditions. This change could be related to a reduction in iceberg-derived freshwater input and may have affected the ability of AAIW to sequester atmospheric CO2. Prior to the MBE, colder and fresher conditions, coinciding with a steep vertical thermal gradient, would have enhanced CO2 drawdown and minimized outgassing, enabling AAIW to retain its high CO2 load. The synchronization of the suggested reduction in AAIW’s uptake efficiency with the increase in atmospheric CO2 across the MBE suggests a pivotal role in modulating atmospheric CO2 during this critical climate transition. This finding challenges the traditional view that this shift is mainly attributed to changes in bottom water formation.
How to cite: Tapia, R., Ho, S. L., Nürnberg, D., Meckler, A. N., Lamy, F., and Tiedemann, R.: Intermediate Water Dynamics and CO2 Anomalies during the Mid-Brunhes Event, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7544, https://doi.org/10.5194/egusphere-egu25-7544, 2025.
The Antarctic Circumpolar Current (ACC) connects all major Ocean basins and plays a pivotal role in regulating ocean circulation modulating the deep-sea ventilation by upwelling and downwelling of water masses. The Southeastern Pacific Ocean (SEP) is a key region of Antarctic Intermediate Water (AAIW) formation, which has significant influence on low latitude climate. South Westerly Winds (SWW) – ACC interaction has an important role in promoting the upwelling of Upper Circumpolar Deep Water (UCDW), which is relatively corrosive and enhances the dissolution of aragonitic foraminiferal tests. Hence, the percentage abundance ratio of aragonitic test benthic foraminifera Hoeglundina elegans vs total calcareous foraminifera test can serve as a reliable proxy for ACC current strength variability. The upwelling and downwelling of UCDW are responsible for CO2 release to the atmosphere and oxygen uptake in the AAIW water mass, respectively, affecting the deep sea biota in the SEP. Hence, this study analysed the benthic foraminifera abundance variations in International Ocean Discovery Program (IODP) Site U1542 (~1101 m depth, Chilean margin, under AAIW influence) for the last ~400 ka to evaluate the linkages between ACC, SWW, and AAIW and associated forcing factors. The spectral and continuous wavelet analyses were performed for the AAIW characteristic proxies i.e. oxic species (%), combined suboxic and dysoxic species (%) of benthic foraminifera that show a 44 kyr obliquity cycle. This cycle suggests the influence of Patagonian Ice Sheet (PIS) dynamics and the role of atmospheric CO2 in regulating marine carbon reservoirs through AAIW production during various glacial-interglacial cycles. The ACC strength variability proxy i.e. aragonitic Hoeglundina elegans (%)/Total calcareous foraminifera (%) shows the presence of ~100 kyr cycle, which is also observed in the Asian monsoon record. This study suggests that ACC has influenced the Asian monsoon by modulating AAIW production, which regulates the atmospheric CO2 concentration linked with 100 kyr cycle.
How to cite: Datta, S., Das, S. K., Rath, S., and Singh, R. K.: Assessing the role of Antarctic Circumpolar Current strength variability in Antarctic Intermediate Water formation and low-latitude climate over the last 400 ka, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9914, https://doi.org/10.5194/egusphere-egu25-9914, 2025.
The long 100,000-year glacial-interglacial cycles are key features of climate evolution since the Mid-Pleistocene Transition, and changes in the Southern Ocean are proposed to have played an important role in the generation of these cycles. Data from the Indian and Pacific sectors of the Antarctic Zone over the last 150 ka show that during the glacial intervals, export production decreased, and surface nitrate concentration, as reflected by d15N of organic matter bound in diatom frustules (d15Ndb), decreased. Together these findings suggest that upwelling was weaker in the Antarctic Zone during the ice ages. Here we report ~2-kyr resolution d15Ndb measurements from the Pacific sector of the Antarctic Zone extending to the past 460 ka, with chronology supported by TEX86L-paleotemperature proxy correlation with air temperature reconstructed from Antarctic ice cores. The results show continuously increasing Antarctic Zone d15Ndb during peak glacial periods. This suggests progressive declines in surface nitrate concentration and, thus, in upwelling and/or vertical mixing intensity as land ice sheets grew, even though Antarctic ice core temperature and atmospheric CO2 appear to have stabilized at their minima earlier in each ice age. This correlation points to an interhemispheric mechanism that links southern high-latitude conditions to northern high-latitude ice buildup during peak glacial intervals. We will discuss the implications for the saw-tooth pattern of the 100,000-year glacial-interglacial cycles and for carbon cycle feedbacks within these 100,000-year cycles.
How to cite: Ai, X., Sigman, D., Martínez-García, A., Studer, A., Fripiat, F., Lamy, F., Schmitt, M., Oleynik, S., and Haug, G.: Progressive declines in Pacific Antarctic Zone upwelling intensity during each glaciation of the last 460 ka , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14263, https://doi.org/10.5194/egusphere-egu25-14263, 2025.
The Antarctic Zone has long been suspected to play a crucial role in the glacial-interglacial changes in atmospheric concentration of CO2. However, global climate has many possible influences on Antarctic Zone conditions, with the potential for interactions between ice, winds and circulation that, in turn, influence the biogeochemistry and carbon budget of the Antarctic Zone surface. In a sediment core from the polar Antarctic Zone, we analyzed diatom-bound nitrogen isotopes to reconstruct surface nitrate concentration, which reflects the balance between biological productivity and the flux of subsurface nitrate into the Antarctic surface. The record covers the last 150 kyr, which includes two peak glacial periods and the subsequent deglaciations and interglacials. During each glacial period, the data support prior interpretations of lower surface nitrate concentrations and reduced circulation-driven nitrate supply to the Antarctic surface, although the change appears to be weaker at this polar Antarctic Zone site than in records from further north in the open Antarctic Zone. Early in each deglaciation, there is a further decline in surface nitrate concentration, reflecting a rise in density stratification. This is followed by an increase in nutrient supply in each of the two interglacials, signaling more vigorous surface-subsurface exchange than during the glacials or the early deglaciations. Combining the data with other Antarctic records further from the continent, the deglacial changes echo model simulations of ongoing global warming, in which upwelling increases near the Polar Front, while subsurface influx to the surface closer to the Antarctic continent decreases in response to ice sheet melting. The findings have implications for the cause of the observed rise in atmospheric CO2 concentrations during deglaciations and also warrant consideration with regard to the future of the ocean’s uptake of global warming heat and fossil fuel-derived CO2.
How to cite: Fripiat, F., Sigman, D. M., Ai, X. E., Dumoulin, C., Moretti, S., Studer, A., Diekmann, B., Esper, O., Frederichs, T., Lamy, F., Liu, L., Pattyn, F., Schmitt, M., Tiedemann, R., Haug, G., and Martínez-García, A.: Ice age and deglacial stratification of the polar Antarctic Zone, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8265, https://doi.org/10.5194/egusphere-egu25-8265, 2025.
In the Antarctic Zone (AZ), deep nutrient-rich waters ascend to the surface, feeding the Southern Ocean's overturning circulation cells. However, the rate of upwelling exceeds the capacity of phytoplankton to fully consume the gross nutrient supply to the AZ surface, leading to the release of previously sequestered CO2 into the atmosphere. During ice ages, enhanced nutrient utilization has been proposed as a mechanism that could contribute to lower atmospheric CO2 concentration. Fossil-bound δ15N records in the AZ point to a more complete nitrate consumption in surface waters during ice ages. This increase in nitrate utilization coincides with reduced export production, suggesting a lower gross nitrate supply to the surface and, therefore, a reduction in the exchange of water between the surface and the deep ocean. Preliminary reconstructions indicate more than a 5-fold reduction in the rate of gross nitrate supply to match paleo proxy data and near complete nitrate consumption at the surface. Model simulations are ambiguous, but none show more than a ≥ 2-fold reduction in water exchange in the AZ during ice ages.
One hypothesis for this discrepancy is the progressive depletion (“mining-out”) of nutrients from the AZ upper ocean. Reduced glacial upwelling, combined with repeated summer nitrate consumption and the export of assimilated nitrate as sinking organic matter, followed by deep winter mixing, could gradually deplete the upper water column’s nutrient reservoir. This process would lower the shallow subsurface nutrient concentrations and elevate nitrate δ15N relative to the deep ocean. As a result, the nutrient supply per volume of upwelled water would decline, aligning better with model simulations.
To test this hypothesis, we developed a 1D advection-diffusion-reaction model of the water column, accounting for surface nitrate consumption and isotope fractionation. The model was calibrated using Argo floats data and high-resolution hydrographic nitrate isotopes transect in the AZ (GO-SHIP SO4P 2018), successfully matching depth and seasonal profiles. We also applied the model to the western subarctic Pacific, which exhibits a similar observation pattern for fossil-bound δ15N and export production during ice ages but contrasts in the ratio between advective and diffusive nutrient supply.
Our results highlight the critical role of nutrient mining in driving isotopic changes during ice ages. With reduced upwelling, nutrients are progressively depleted in the upper AZ. However, even under this mechanism, a substantial reduction in upwelling (more than a twofold decrease) is still required to achieve observed glacial δ15N values – though less extreme than previous estimates. Nevertheless, in reduced upwelling scenarios, the glacial surface nitrate concentration is significantly higher than previous estimates. This supports the potential of nutrient mining in matching paleo-data with less drastic changes to the Southern Ocean.
How to cite: Dumoulin, C., Fripiat, F., Hinnenberg, B., Ren, H., Sigman, D., and Martinez-Garcia, A.: Exploring glacial-interglacial nutrient conditions in the Antarctic Zone: Insights from a one-dimensional water column model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8697, https://doi.org/10.5194/egusphere-egu25-8697, 2025.
The increased supply of the micronutrient iron (Fe) promotes primary and export production in the Fe-limited Southern Ocean, which acts as a dynamic sink of atmospheric CO2 that has amplified past natural climate variations. This mechanism critically relies on the partial dissolution of the lithogenic particle input. However, the influence of lithogenic particle composition (and Fe solubility) on Southern Ocean export production in the large Antarctic Zone (AZ) is largely unconstrained for the Pleistocene glacial cycles. Here, we present a comprehensive dataset of glacial-interglacial particle fluxes and geochemical composition in the remote Southeast Pacific AZ covering the last 500,000 years. The observed high fluxes and compositional range of lithogenic material can only be explained by sediment input sourced from West Antarctica. Importantly, higher solubility of the lithogenic input corresponds with enhanced export production, implying that West Antarctic Ice Sheet (WAIS) dynamics controlled the primary production in large parts of the South Pacific AZ. These processes contributed to atmospheric CO2 reductions in particular during the early part of the glacial cycles, suggesting that the WAIS retreat will likely affect predictions of future changes in Southern Ocean biogeochemical cycles.
How to cite: Struve, T., Lamy, F., Gäng, F., Klages, J., Pahnke, K., Kuhn, G., Esper, O., Lembke-Jene, L., and Winckler, G.: West Antarctic Ice Sheet dynamics controlled export production in the Pacific Southern Ocean over the last 500,000 years, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21005, https://doi.org/10.5194/egusphere-egu25-21005, 2025.
The warmer-than-present interglacial periods of the late Pleistocene provide the closest palaeo analogues to inform predictions of Antarctic ice sheet mass loss over the coming decades and centuries. However, the response of Antarctica’s ice sheets to environmental conditions during these interglacial periods remains poorly constrained, resulting in significant uncertainties in ice sheet model predictions of future sea-level rise. Here, sediment provenance analyses (Nd and Sr isotope compositions, detrital zircon U-Pb dates and heavy mineral counts) reveal changes to ice sheet extent in the Ross Sea over the glacial-interglacial cycles of the last ~400 kyr at International Ocean Discovery Program (IODP) Site U1524.
Glacial periods show a broadly mixed East/West Antarctic provenance signature, consistent with an ice sheet grounded across most of the Ross Sea continental shelf that reworked older sediments. In contrast, interglacial intervals - including the Holocene - consist primarily of sediment derived from West Antarctica, suggesting westward transport by ocean currents dominates sediment delivery to the site. Detailed examination of these West Antarctic sourced intervals reveals a consistent pattern of provenance change over the course of each interglacial examined. East Antarctic-derived sediment is only dominant at the site for two short-lived intervals just after two interglacial periods, thought to be Marine Isotope Stage (MIS) 11 and MIS 9 based on the current age model. These intervals may record a transient ice sheet configuration in the earliest part of each glacial period where the Ross Ice Shelf had grown to a larger-than-present size, whilst the grounding zone had not yet advanced far beyond its present-day location. Critically, each of these two East Antarctic dominated intervals displays different provenance characteristics, implying differing ice flow patterns in the Ross Ice Shelf and therefore different ice sheet extents in the preceding interglacials. This suggests Antarctica’s ice sheets are sensitive to the relatively subtle differences in climate seen in recent interglacial periods.
How to cite: Marschalek, J., Pastore, G., van de Flierdt, T., Patterson, M., McKay, R., Holder, L., Grant, G., Mueller, J., Xiao, W., Kim, S., Cortese, G., Bombard, S., Leckie, R. M., van Peer, T., Sugisaki, S., Seki, O., Kulhanek, D., Vermeesch, P., Carter, A., and Gasson, E. and the Additional authors: Evidence for West Antarctic Ice Sheet sensitivity to different recent Pleistocene interglacial climates, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17938, https://doi.org/10.5194/egusphere-egu25-17938, 2025.
Most ice sheet models indicate that the Antarctic Ice Sheet (AIS) will lose considerable amounts of ice over the coming decades and centuries. This mass loss will mainly be caused by warm deep waters increasingly reaching the AIS’ margins and, with many upstream parts of ice-sheet sectors being grounded far below modern sea level, this will lead to accelerating and irreversible retreat. Are we therefore currently witnessing the initiation of runaway retreat of large parts of the ice sheet that will result in rapid sea level rise resulting in severe consequences for global coastal communities? Finding more reliable answers to this question requires robust multi-proxy data evidence from AIS-proximal records spanning times that were warmer and CO2-richer than today. Such sediment records are rare and challenging to obtain, requiring drilling campaigns that are only feasible within large multinational consortiums. Some extensive Antarctic field campaigns, however, were recently realized, are about to be accomplished, or at the planning stage. This presentation will introduce these campaigns and highlight how their results combined with novel coupled modeling techniques will eventually provide significant new insights into the AIS’ long-term evolution. This information will allow for better predictions of its response to conditions anticipated for the foreseeable future.
How to cite: Klages, J. P., Hillenbrand, C.-D., Salzmann, U., Bohaty, S. M., Bickert, T., Gohl, K., Lohmann, G., Bauersachs, T., Larter, R. D., van de Flierdt, T., Kulhanek, D. K., and Läufer, A.: Evolution of the Antarctic Ice Sheet from green- to icehouse conditions: Using unique data for advancing numerical model simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-413, https://doi.org/10.5194/egusphere-egu25-413, 2025.
Constraining the nature and timing of changes to the East Antarctic ice sheet in the Weddell Sea-Dronning Maud Land sector over the last glacial cycle has been challenging, due to limited geological evidence and contrasting models of past ice sheet extents and retreat behaviour. It is important to distinguish between these scenarios, because this region is also a source of Antarctic Bottom Water, and there are regions of the ice sheet which are sensitive to ocean warming.
Here, we present a novel archive of past sea-ice environments from regurgitated stomach oils of snow petrels (Pagodroma nivea) spanning the last ~45,000 years. Snow petrels forage within sea ice, and record changes to their diet and surface ocean properties within their stomach oil biochemistry. The stomach-oil deposits we examine here are preserved at breeding colonies extending from the Theron Mountains (30°W) to the Sør Rondane Mountains (23°W). We use the deposits to constrain the presence of bedrock for breeding, which becomes available as the ice sheet thins or retreats.
We show major variations in snow petrel occupation over time, in part related to availability of breeding habitat as ice sheet extent fluctuated. Reconstructions of snow petrel diet using multi-proxy analysis of fatty acids, stable carbon and nitrogen isotope ratios, and elemental composition (via XRF) shows centennial-scale variations in diet and regional differences in sea ice histories. We propose that open waters (‘polynyas’) were present in the sea ice during Marine Isotope Stages 2 and 3, and that their properties evolved through time as summer sea ice expanded to its maximum extent (~29-22 ka) and retreated across the last deglaciation. We explore how these changes in summer sea-ice environment are linked to changes in ice-sheet extent and ocean/atmospheric circulation over the last ~45 ka.
How to cite: McClymont, E., Damm-Johnsen, T., Wakefield, E., Rix, A., Bentley, M., Cole, Y., Grecian, W. J., Hodgson, D., Honan, E. M., Li, Z., Penny, C., Strong, K., Stevenson, M., Ascough, P., Grocke, D., Hoelzel, A. R., Phillips, R., Sime, L., and Willis, S.: Interactions between Antarctic ice-sheet extent and summer sea-ice variability over the last 45,000 years in the Weddell Sea-Dronning Maud Land as reconstructed from snow petrel stomach-oil deposits, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12282, https://doi.org/10.5194/egusphere-egu25-12282, 2025.
Posters on site: Fri, 2 May, 10:45–12:30 | Hall X5
The Circumpolar Deep Water (CDW) is one of the key components of the global climate system and Antarctic cryosphere. However, the variability of the CDW in the Indian sector of the Southern Ocean over glacial-interglacial climate cycles is still unknown due to a lack of knowledge of deep-water geochemistry. The new records of δ18O and δ13C in benthic foraminifer from Del Caño Rise (DCR-1PC and DCR-2PC) characterized the δ13C composition of CDW in the Indian sector of the Southern Ocean. During the glacial periods, the South Indian has lower δ13C values, representing the influence of a more southern water mass, perhaps a glacial Antarctic Bottom Water (AABW). A comparison with published South Atlantic (ODP 1090) and South Pacific (PS 75/59) deep water records suggests a continuous water mass exchange throughout the past 500 ka. Almost identical glacial-interglacial δ13C variations imply a common deep-water evolution in all basins, suggesting persistent CDW exchange and homogenization. A much lower δ13C signal was observed at the deeper Cape Basin (ODP 1089, RN13-229), which was influenced by strong AABW originating from the Weddell Sea during the glacial periods. The anomalous heavier values (> 0.5‰) were recorded at DCR-1PC during the MIS 5 (~97 ka and ~83 ka), suggesting the strong influence of the North Atlantic Deep Water (NADW).
How to cite: Ikehara, M.: Circumpolar Deep Water variability in the Southern Ocean during the past 500 ka, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3529, https://doi.org/10.5194/egusphere-egu25-3529, 2025.
The atmospheric CO2 content has been discussed as one of the major factors influencing global climate. In the framework of the deep ocean forming the main reservoir of carbon dioxide, the Southern Ocean plays a crucial role in partitioning carbon between the atmosphere and the deep ocean. The processes resulting in the variability of atmospheric CO2 and carbon uptake in the deep ocean have not yet been fully identified. Sedimentary structures imaged with seismic reflection data are interpreted regarding direction and intensity of pathways of deep/bottom water masses to contribute to the knowledge on potential locations of carbon subsidence. Under the assumption that the general circulation scheme has been similar during the Neogene, i.e., driven by gyres, the positions and sizes of palaeo-gyres have been reconstructed, which were then interpreted regarding the intensity of carbon uptake. This has been compared with published reconstruction of warming/cooling trends of the global climate. While the method applied is equivocal it links observed sedimentary structures with the development of gyres thus potential sports of carbon uptake. This way the presented reconstruction provides pieces to the climate variability puzzle, which can be tested using numerical simulation.
How to cite: Uenzelmann-Neben, G.: Neogene circulation in Princess Elizabeth Trough, Southern Ocean, driven by gyres?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1189, https://doi.org/10.5194/egusphere-egu25-1189, 2025.
Understanding Southern Ocean-Antarctic Ice Sheet (AIS) interactions in the geological past is crucial for evaluating the sensitivity of the ice sheet to ocean forcing during future climate warming and predicting its contribution to future sea-level rise. Geological evidence indicates the onset of a modern-like strong Antarctic Circumpolar Current (ACC) in the Late Miocene (~10 million years ago). However, the response of the East Antarctic Ice Sheet to these changes remains poorly constrained. In this study, we present neodymium and strontium isotope compositions of fine-grained (<63 μm) detrital sediments from Ocean Drilling Program (ODP) Site 1165, located on the continental rise off Prydz Bay. These records trace changes in sediment provenance from the Middle Miocene to the present, offering insights into how erosion by Antarctica’s ice sheets in the Prydz Bay sector has evolved over time. Our data reveal that the ice sheet in the Prydz Bay sector crossed a tipping point in the Late Miocene, becoming highly dynamic. Our preliminary findings suggest that this significant shift in the East Antarctic Ice Sheet's evolution may be linked to the emergence of the modern ACC, indicating major ocean-ice interactions in the Late Miocene.
How to cite: Evangelinos, D., van de Flierdt, T., Pena, L. D., Paredes, E., Cacho, I., and Escutia, C.: East Antarctic Ice Sheet–Southern Ocean Interactions in Prydz Bay region from the Middle Miocene to the Present, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12620, https://doi.org/10.5194/egusphere-egu25-12620, 2025.
The Southern Ocean, especially the Subantarctic region, plays a critical role in anthropogenic carbon uptake, heat exchange, and nutrient transfer between high and low latitudes. Pronounced past changes in surface ocean properties, particularly sea surface temperatures (SSTs), reflect this region’s exceptional sensitivity to external and internal forcings over millennial and orbital timescales. This underscores its importance in understanding past and future climate change and its key role as major link between Antarctica and the low latitudes.
Accurate reconstructions of past SSTs are crucial for understanding past climate dynamics and validating models for future projections. To achieve this, various temperature proxies based on physical, chemical, and biological properties preserved in marine sediments have been developed. However, all proxies carry uncertainties due to environmental factors that may bias the signals archived in the sedimentary record. A multiproxy approach helps to mitigate these uncertainties, providing a more robust and comprehensive interpretation of past climate conditions.
This study presents a high-resolution SST reconstruction from IODP Expedition 383 Site U1539 and pre-site survey PS75/054 in the Subantarctic South Pacific, near the modern Subantarctic Front (SAF), using three different temperature proxies: a diatom transfer function and two organic proxies based on coccolithophorid alkenone lipids (UK’37) and archaeal glycerol dialkyl glycerol tetraether (GDGT) lipids (TEX86). This location is characterized by unusually high sedimentation-rates (~10-50 cm/kyr), mainly because the northerly extended opal belt reaches Site U1539 during glacials with high diatom ooze deposition.
Our record spans the last 150 ka with a centennial to millennial resolution. The general temperature pattern follows the overall glacial/interglacial succession. The alkenone SSTs range from minimum values approaching zero around the Last Glacial Maximum to ~10°C in MIS 5e (and 6-7°C during the Holocene equivalent to modern austral summer SST). These exceptionally high glacial/interglacial amplitudes are much less pronounced in the diatom summer SST reconstruction with an amplitude of only~3-4°C. Much higher SSTs are shown by the TEX86 with equally maximum values during MIS 5e (absolute SST higher than the alkenone SST). However, the TEX86 temperature record shows very high amplitudes at millennial time-scales. Within dating uncertainties, these changes follow the Antarctic temperature pattern as recorded in ice-core.
We are discussing the palaeoceanographic implications of our SST records and potential reasons for the partial mismatches of the different SST proxies. These include varying seasonality sensitivity, depth habitat, and SST calibration and transfer function uncertainties.
How to cite: Ruggieri, N., Jaeschke, A., Hefter, J., Rigalleau, V., Lembke-Jene, L., Esper, O., Mollenhauer, G., Winckler, G., and Lamy, F.: Multi-proxy reconstruction of sea surface temperatures in the Pacific Southern Ocean over the last glacial-interglacial cycle, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18659, https://doi.org/10.5194/egusphere-egu25-18659, 2025.
The intensification of Northern Hemisphere Glaciation at ~2.7 Ma ago, known as the significant iNHG event during the late Pliocene, has marked a prominent transition of Earth’s climate from uni-polar to bi-polar ice sheets. Here, we present proxy records from the deep sea sediments of Ocean Drilling Program Site 1123 in the South Pacific (41°47´S，171°30´W，water depth 3290 m), covering a time span of approximately 3.5 to 1.7 million years, aiming to reveal the South Pacific deep circulation and ocean carbon reservoir changes during this period. After careful rinsing of the sediment samples, we selected benthic foraminifer C. Wuellerstorfi and G. Mundulus for B/Ca ratio and fish tooth εNd isotope analysis, with a temporal resolution of approximately 3 to 10 thousand years, totaling 112 sediment samples.
Our results show that the eNd of ODP Site 1123 rapidly shifted towards negative values by approximately 2 units during the iNHG period. Meanwhile, the deep-water △[CO32-] reconstructed using the B/Ca ratio of benthic foraminifera exhibited a positive shift at around 2.9 Ma and then a negative shift at around 2.7 Ma. We interpret that the positive shift in △[CO32-] at ODP Site 1123 at ~2.9 Ma might be caused by the weakening of the Antarctic Circumpolar Current (ACC), which reduced the upwelling in the Southern Ocean and thereby caused a shift of the major source of the water mass bathing this site from the north with more negative carbonate ion concentrations to that in the south with more positive carbonate ion concentrations. The enhanced northward expansion of southern sourced water in the deep Pacific Ocean could result in a decrease in the Pacific carbon reservoir. We further hypothesize that the enhanced input of sub-Antarctic dust during the iNHG period had great potential for increasing the iron fertilization effect, thereby strengthening the biological pump in the sub-Antarctic region. This process had resulted in an increase in the carbon storage and a more negative carbonate ion concentration in the southern sourced water flowing into the Pacific Ocean, ultimately causing the negative shift in △[CO32-] at ODP Site 1123 and enhancing carbon storage in the Pacific Ocean. Our results demonstrate that the Pacific Ocean had played a great role in the decline of the atmospheric pCO2 and finally contributed to the final formation of the iNHG event.
How to cite: Xu, J., Ma, Y., and Tian, J.: Synergic Variations of the South Pacific Deep Circulation and Carbon Reservoir During the Late Pliocene Intensification of the Northern Hemisphere Glaciation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2567, https://doi.org/10.5194/egusphere-egu25-2567, 2025.
The Earth's climate transitioned significantly from the mid-Piacenzian Warm Period (mPWP, 3.3–3.0 Ma) to the intensified Northern Hemisphere Glaciation (iNHG, 3.0–2.7 Ma). The Southern Ocean, a major CO2 sink, played a pivotal role in this shift by regulating CO2 through ocean ventilation. While most research focuses on the Northern Hemisphere, this study investigates planktonic foraminiferal assemblages, stable isotopes, trace metals, and sedimentary records from the Subantarctic Pacific to explore the Southern Hemisphere’s contribution.
Three intervals are identified: mPWP (3.3–3.0 Ma), iNHG (3.0–2.7 Ma), and the Subantarctic-dominant interval (<2.7 Ma). Key planktonic foraminiferal groups include Neogloboquadrina pachyderma (cold-water indicator), Globoconella spp. (thermocline indicators, G. puncticulata and G. inflata), and Globigerina bulloides (nutrient-enrichment indicator). During the mPWP, thermocline species dominated (90%). The faunal assemblage underwent a transition during the iNHG, with a 40% decline in Globoconella spp. and accompanied growth of N. pachyderma. By the Subantarctic-dominant interval, N. pachyderma increased (~90%), reflecting expanded cold-water conditions. G. bulloides rose by 30% at the end of the mPWP and fluctuated with glacial-interglacial (G/IG) cycles, peaking during interglacials (~25% higher). These shifts suggest destratification at the mPWP’s end and higher surface productivity during the Subantarctic-dominant interval, supported by increased planktonic foraminiferal accumulation rates.
Sedimentary analysis reveals a long-term decrease in CaCO3 content (90% reduction) and a slight increase in total organic carbon (TOC) content, showing a 1% growth throughout the research interval. Additionally, ice-rafted debris (IRD) production exhibits a pronounced increase, reaching a maximum of 200 pieces/cm²·kyr during the Subantarctic-dominant interval, and demonstrates a long-term upward trend throughout the research interval. This rise in the IRD aligns with the increased abundance of the cold-water species N. pachyderma, suggesting an expansion of sea ice and ice sheets.
Stable isotope records reveal long-term environmental changes. δ¹³C values decreased during the mPWP and stabilized during the iNHG but became G/IG-dominant in the Subantarctic-dominant interval, with lower values in glacial periods likely due to increased Circumpolar Deep Water (CDW) input. δ18O records suggest a cooling trend (over 1‰) throughout the interval, showing G/IG variability in N. pachyderma and Globoconella spp. during the Subantarctic-dominant period. The δ18Oseawater derived from planktonic foraminifera generally exhibits a long-term increasing trend from -0.5‰ to 2‰, with glacial periods showing approximately 1‰ higher δ18Oseawater compared to interglacial periods.
Mg/Ca-derived temperatures show complex patterns. While N. pachyderma Mg/Ca ratios reveal strong G/IG fluctuations (~6°C) during the Subantarctic-dominant interval, G. puncticulata exhibits a long-term cooling (~6°C) since the iNHG. G. inflata mirrors these trends, and G. bulloides shows a 2°C decline. These data highlight N. pachyderma’s sensitivity to sea-ice expansion and the thermal stability preferences of G. bulloides.
Overall, stable ocean stratification and minimal sea ice characterized the mPWP, underpinned by a well-stratified thermocline. Since the iNHG, frontal system shifts, destratification, and increased CDW upwelling have enhanced nutrient availability and phytoplankton photosynthesis, boosting CO2 sequestration. By 2.55 Ma, the Subantarctic Pacific emerged as a critical CO2 sink, driven by Pleistocene G/IG cycles and contributing significantly to global CO2 storage.
How to cite: Wu, L.-P., Lo, L., Shen, C.-C., Löwemark, L., Wu, P.-T., and Mii, H.-S.: Evidence of significant destratification of the Subantarctic Pacific during the past 3.3-2.4 million years, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3002, https://doi.org/10.5194/egusphere-egu25-3002, 2025.
The Southern Ocean (SO) is a key area for global climate. It connects the deep water with the surface through upwelling. The deep SO, storing a large amount of carbon during the glacial period and releasing CO2 during the deglacial period, is critical for the carbon cycle on orbital-millennial timescales.
In the Southwest Pacific (SWP), there are many reconstructions of deep water, however, these reconstructions primarily rely on carbon and oxygen isotopes, which cannot effectively distinguish the North Pacific Deep Water (NPDW) and the Circumpolar Deep Water (CDW). Neodymium isotopes (εNd) of seawater is dominated by the crustal sources, which is spatial heterogeneous, enabling its wide application as water mass traces. However, the available data in the SWP is not enough to resolve spatial complexity and evolution mechanisms of water masses, especially at the depth of NPDW and UCDW (Upper CDW).
Here, εNd on planktonic foraminifera are used to investigate the evolution of deep-water masses in SWP since 30 ka BP on core MD97-2115 (43° 6' 30" S, 171° 29' 7.8" W, 2160 m water depth), which is located on the east Chatham Rise.
The εNd results show an increase from -4.5 to -3.8 between 30 ka BP and 21 ka BP, followed by a positive shift to -4.7 at 19 ka BP. After 19 ka BP, the values remain relatively stable around -5.
These values agree well with modern NPDW seawater εNd value in Southwest Pacific Basin, ranging from -4 to -5. Comparison with nearby εNd records suggests a persistent influence of NPDW in the eastern Chatham Drift since 30 ka BP. However, the mechanism of the shift around 19 ka BP needs further investigation.
How to cite: Tang, X., Siani, G., and Colin, C.: The evolution of deep water in the Southwest Pacific Ocean since 30 ka BP, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5120, https://doi.org/10.5194/egusphere-egu25-5120, 2025.
During the last glacial period, millennial-scale iceberg discharges in the North Atlantic, known as Heinrich Events (HEs), could have shifted the Southern Hemisphere Westerly Wind Belt (SWW) poleward and potentially led upwelling-driven CO2 outgassing from the Southern Ocean. However, direct evidence of SWW poleward shift in response to HEs remains limited. Based on detrital elements, minerals, and grain-size records in well-dated sediment cores, MR16-09 PC02 (46°04.23′S, 76°32.10′W, 2793 m water depth) and PC03 (46°24.32′, 77°19.45′, 3082 m water depth), from off western Patagonia at ~46°S, we found abrupt onsets in the discharge of coarse silt-sized detritus during the latter half of each HEs (HE 3, 4, 5, 5a, and 6) originating from the Patagonian Batholith located in the coastal area of western Patagonia. Such abrupt discharges are unique events south of ~46°S and probably reflect the extension of glacial erosion into the western fjords related to a pronounced positive anomaly in the glacial accumulation/ablation mass balance of the western-central Patagonian ice sheet. Our climate model (MIROC4m) hosing experiment in the North Atlantic suggests the SWW and precipitation belt began shifting poleward hundreds of years after the onset of HE, which is consistent timing with our proxy data. Thus, increased precipitation south of 46°S following the poleward-SWW shift most likely generated detritus discharges. These findings provide critical evidence of abrupt climate changes propagating from the North Atlantic to the southern midlatitudes via the large-scale reorganization of the atmospheric and ocean circulations.
How to cite: Kasuya, T., Nagashima, K., Hasegawa, H., Okazaki, Y., Kuniyoshi, Y., Abe-Ouchi, A., Iwasaki, S., Arz, H. W., Hagemann, J. R., Harada, N., Murayama, M., Lange, C. B., and Lamy, F.: Poleward shift in Southern Westerlies triggered by iceberg discharge in the North Atlantic, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7778, https://doi.org/10.5194/egusphere-egu25-7778, 2025.
Marine terminating ice sheets and glaciers influence the chemical, biological and physical dynamics of adjacent marine systems. For example, changes in ice extent affect sedimentation rates along glaciated coasts, as well as drive shifts in marine productivity linked to stratification and nutrient delivery. These changes can affect the redox conditions and storage of organic carbon in shelf sediments. Therefore, glacial retreat due to modern climate warming could potentially have major impacts on marine productivity, sedimentation and carbon cycling in the Southern Ocean and other high latitude areas. To study the effects of warming on diagenetic processes and sedimentation dynamics, we analyzed core samples from IODP Expedition 383 Site U1542, collected close to the southern Chilean Margin, a region of rapid sedimentation rates that is linked to the Southern Ocean via the Cape Horn Current and the Drake Passage. This site provides a high-resolution record of changes at the western maximum extent of the Patagonia Ice Sheet (PIS), which was dominant in this setting during the last glacial period. Preliminary results from this Site indicate 7 distinct intervals of short-term warming events (1-5 kyr) between 20 and 60 kyr. We analyzed samples spanning these warming events for total organic carbon, grain size, and Fe minerology, and compared results with records of trace metal (e.g., Mn and Ni) contents from X-ray fluorescence (XRF) analysis. Preliminary results indicate that when the PIS retreated during short-term warming events, the redox conditions in the sediment shifted, becoming more reducing as indicated by trace metal contents and Fe minerology, and the organic carbon content in the sediment increased. In addition, larger grain sizes during warm periods suggest a possible decrease in fine glacial flour input with the retreat of the ice sheet. Overall, this study disentangles signals reflecting diagenetic, benthic redox and sedimentological changes driven by changes in glacial input. This research ultimately aims to improve our understanding of how a marginal marine system responded to climatic warming and ice sheet loss, serving as a potential analog for future loss of modern ice sheets.
How to cite: Herbert, L. C., Brion, E., Wehrmann, L. M., Rigalleau, V., Arz, H. W., Winckler, G., and Lamy, F.: Benthic responses to warming and ice retreat on the Chilean Margin during the Last Glacial Period, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14444, https://doi.org/10.5194/egusphere-egu25-14444, 2025.
Millennial-scale variations in the strength and position of the Antarctic Circumpolar Current exert considerable influence on the global meridional overturning circulation and the ocean carbon cycle. The mechanistic understanding of these variations is still incomplete, partly due to the scarcity of sediment records covering multiple glacial-interglacial cycles with millennial-scale resolution. Here, we present high-resolution current strength and sea surface temperature records covering the past 790,000 years from the Cape Horn Current as part of the subantarctic Antarctic Circumpolar Current system, flowing along the Chilean margin. Both temperature and current velocity data document persistent millennial-scale climate variability throughout the last eight glacial periods with stronger current flow and warmer sea surface temperatures coinciding with Antarctic warm intervals. These Southern Hemisphere changes are linked to North Atlantic millennial-scale climate fluctuations, plausibly involving changes in the Atlantic thermohaline circulation. The variations in the Antarctic Circumpolar Current system are associated with atmospheric CO2 changes, suggesting a mechanistic link through the Southern Ocean carbon cycle.
How to cite: Rigalleau, V., Lamy, F., Ruggieri, N., Sadatzki, H., Arz, H. W., Barker, S., Lembke-Jene, L., Wegwerth, A., Knorr, G., Venancio, I. M., Pinho, T. M. L., Tiedemann, R., and Winckler, G.: 790,000 years of millennial-scale Cape Horn Current variability and interhemispheric linkages, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8794, https://doi.org/10.5194/egusphere-egu25-8794, 2025.
The Southern Ocean plays a critical role in the Earth system, both for the uptake of anthropogenic carbon and for the exchange of heat and nutrients between high and low latitudes. This is particularly valid for the Subantarctic Southern Ocean where atmosphere-ocean-cryosphere interactions and teleconnections between high and low latitudes play an important role in past and future climate change providing the major link between Antarctica and the low latitudes. In general, atmosphere-ocean interactions within the Southern Ocean are believed to control sea ice cover, upper ocean stratification, biological nutrient utilization, and exposure rates of CO2-enriched deep water. Thus, they have been considered to play a key role in explaining the variability in atmospheric CO2 concentrations, which are controlled by biogeochemical and physical processes.
Beyond information from continental margin records, little is known on millennial-scale variability in the pelagic Southern Ocean. High resolution sediment archives reaching back various glacial/interglacial cycles have not been explored so far. This includes the time span beyond the reach of the presently available ice-cores and will likely be critical for evaluating the extended time-interval of the ongoing European Beyond EPICA – oldest ice (BE-OI) ice core drilling initiative. Our project focuses on high resolution paleoceanographic reconstructions (biomarker-based sea surface temperatures, biogenic opal, Antarctic Circumpolar Current strength, ice-rafted detritus) of upper ocean dynamics at Expedition 383 IODP Site 1539 in the subantarctic South Pacific in vicinity of the modern Subantarctic Front (SAF). This location is characterized by unusually high sedimentation-rates (~10-50 cm/kyr), mainly because Site U1539 is reached by the northerly extended opal belt during glacials with high diatom ooze deposition. This unique setting provides a high-resolution pelagic sediment archive in an area with strong oceanographic gradients (close to the SAF with strong dynamics of SST, ACC strength, and the influence of the opal belt).
We expect that high resolution records from IODP Expedition 383 Site U1539 could substantially enhance our understanding of sub-orbital climate variations and potential tipping points in the Southern Ocean and their link to the marine carbon cycle and Antarctic ice-sheet stability.
How to cite: Lamy, F., Rigalleau, V., Ruggieri, N., Lembke-Jene, L., Arz, H. W., Mollenhauser, G., and Winckler, G.: Orbital and millennial-scale upper ocean dynamics in the Pacific Southern Ocean since the Mid-Pleistocene Transition, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18501, https://doi.org/10.5194/egusphere-egu25-18501, 2025.
IODP Site U1537 is located in a contourite deposit in the Dove Basin of the southeastern Scotia Sea, in 3,713 meters of water. It consists of alternating diatom oozes and silty clays, with variable amounts of sand to gravel-sized clasts delivered as IRD. Shipboard track measurements, weight percent ice-rafted detritus (IRD), 40Ar/39Ar hornblende and biotite age (provenance), and split core XRF elemental measurements were collected and examined to study Antarctic ice-sheet dynamics between 1.75 and 3.35 Ma, the Plio-Pleistocene transition.
The highest and most variable amounts of IRD (from 0 to >0.4 g/cm2/ky) are in the earliest part of the study before 3.24 Ma. Between 3.24 and 2.4 Ma, with the exception of one sample, IRD comprises < 0.2 g/cm2/ky of the sediment. Between 2.4 and 2.1 Ma, IRD form < 0.05 g/cm2/ky, and from 2.1 Ma to the end of the study, they return to values of < 0.1, g/cm2/ky. With the exception of the lowest IRD interval (2.4 and 2.1 Ma), 40Ar/39Ar ages of biotite and hornblende grains are sourced from both East and West Antarctica, with the majority being between about 400 and 600 Ma old, broadly corresponding to the Pan-African event, and the assemblage of Gondwana.
The 300,000-year, diatom-rich, low IRD interval between 2.4 and 2.1 Ma is unique in that all of the grains, except one, came from West Antarctica. Other Antarctic sites such as IODP Site U1361 (Wilkes Land), and ODP Site 1011 (northwest tip of the Antarctic Peninsula), also have their lowest IRD values during this time interval. We propose that this was a warmer time interval and that icebergs from East Antarctica either melted before reaching the Dove Basin or there were no ice-terminating glaciers.
How to cite: OConnell, S., Fenton-Samuels, K., Hemming, S., Reilly, B., Wang, C., and Anee, S.: Evidence from IODP Site U1537 in the Dove Basin, Scotia Sea for a warmer Antarctica during the early Pleistocene (2.4-2.1 Ma) , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14057, https://doi.org/10.5194/egusphere-egu25-14057, 2025.
Radiolarians are siliceous marine zooplankton found in all of the world’s oceans, inhabiting the entire water column. Their fossilised skeletons, preserved in marine sediments, provide valuable paleoceanographic information due to their distinct depth preferences. In the Southern Ocean, radiolarians preserved in ice-edge marine sediment cores offer a snapshot into past oceanographic conditions and climatic changes linked to ocean-ice interactions.
Detailed counts of radiolarian taxa have been generated using a sediment core from the Sabrina Coast, East Antarctica. The Sabrina Coast serves as the marine exit point of the Totten Glacier, which is currently thinning due to surface and basal processes. The radiolarian record reveals instances of water mass change on the continental slope during the four most recent interglacial periods (Marine Isotope Stages 1, 5, 7, and 9).
Radiolarian assemblages in this region exhibit greater species richness and diversity than other microfossil groups, such as diatoms and silicoflagellates. Factor analysis highlights that radiolarian assemblages are more dynamic and variable than diatom assemblages during interglacial periods. Fluctuations in the abundance of key radiolarian taxa indicate the presence of intermediate water at times in each interglacial. When paired with subsurface temperature reconstructions, these findings may reveal past periods of basal melting of the Totten Glacier.
How to cite: Lawler, K.-A., Lowe, V., Cortese, G., Leventer, A., Noble, T., O'Brien, P., Opdyke, B., Post, A., and Armand, L.: Radiolarians reveal past water mass changes at the Sabrina Coast, East Antarctica, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14857, https://doi.org/10.5194/egusphere-egu25-14857, 2025.
During the Late Quaternary global climate variations and interactions with the southern westerly wind belt and the adjacent surface ocean circulation caused glacier advances and retreats in New Zealand’s Southern Alps. Most studies in this region, however, focus on the last glacial period and evidence of older glacier activity is more fragmentary. The use of marine sediment cores as continuous archives for glacier fluctuations over glacial-interglacial cycles is a common method to circumvent such terrestrial archive limitations. Our study investigates the glaciation history of New Zealand’s South Island over the past 200,000 years and its interaction with paleoceanographic changes of the adjacent Southeast Tasman Sea. Solander Trough south of New Zealand represents a major conduit of terrestrial sediments from the Southern Alps. Core SO290-17-1 from Solander Trough is therefore ideally suited for a multi-proxy approach. The stratigraphy of the core is based on oxygen isotopes from benthic foraminifera and X-ray fluorescence core scanning, paleo- and rockmagnetic measurements. In addition, stable oxygen and carbon isotopes from planktic and benthic foraminifera are combined with the former methods for the paleoenvironmental reconstructions. The XRF Fe/Ca ratio indicates enhanced terrestrial inputs during MIS 2, MIS 4 and MIS 6. To investigate changes in sediment source and hence glacier dynamics on land, we use radiogenic neodymium isotopes (expressed in ɛNd) as a proxy for source-specific terrestrial input. Significant ɛNd changes in SO290-17-1 are expected in response to glacier fluctuations because of the complex geology (in nature and age) of the Fiordland and East Southland regions, on which glaciers fluctuated during the last glacial periods. Our data for MIS 4-6 will be compared to results obtained on core TAN1106-28 from the Solander Trough for MIS 1-4 (Toucanne et al., submitted).
How to cite: Krüger, H., Arz, H., Toucanne, S., Kaiser, J., Lamy, F., Lembke-Jene, L., Nowaczyk, N., and Pahnke, K.: Land-ocean interaction in southern New Zealand during the past 200 ka, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17190, https://doi.org/10.5194/egusphere-egu25-17190, 2025.
Persistent deep-water formation in the North Atlantic and Southern Ocean is believed to drive the ventilation of the global deep ocean throughout late Pleistocene interglacial periods. The persistency of interglacial deep-ocean ventilation was, however, challenged based on reconstructed deep ocean deoxygenation events at Ocean Drilling Program (ODP) Site 1094 from the Antarctic Atlantic Ocean attributed to a perturbation in Antarctic Bottom water (AABW) formation during Marine Isotope Stage (MIS) 5e and 11. While a connection to instabilities of the West Antarctic Ice Sheet related to warming of Circumpolar Deep Water was postulated, the drivers and spatial extent of these ‘AABW stagnation events’ remain incompletely known. Here, we present new bottom water oxygen (BWO) reconstructions based on authigenic U enrichments in benthic foraminiferal coatings of Uvigerina spp. from Subantarctic Atlantic sediment core MD07-3077 (44.15°S, 14.23°E; 3770 m) for MIS 11 (424-374 ka before present). A combination of these BWO estimates with Uvigerina spp. Mg/Ca-derived bottom water temperature (BWT)- and δ18O-derived bottom water salinity (BWS) reconstructions at the same study site provides insights into the impact and mechanisms driving AABW stagnation events in the Atlantic Southern Ocean. Our results reveal predominantly well-oxygenated deep-water conditions in the Subantarctic Atlantic during MIS 11, with only one transient low-BWO event at 395 ka before present. This suggests that AABW stagnation events during MIS 11 were largely confined to the Antarctic Atlantic Ocean, indicating a limited northward expansion of poorly oxygenated water. Although this hints at a driver from the south, the variability in our reconstructed BWT and BWS records during the postulated MIS11 AABW stagnation events suggest various hydrographic settings that pinpoint mechanistic differences in the drivers among the bottom water deoxygenation events. Our new data provides crucial constraints on the (in)stability of climatic conditions in the Atlantic Southern Ocean, and by inference near the Antarctic ice sheet margin, during the warmer-than-present climate interval MIS 11.
How to cite: Oelkers, L. S., Vazquez Riveiros, N., Frick, D. A., Waelbroeck, C., and Gottschalk, J.: Changes in deep water circulation dynamics in the South Atlantic Ocean during Marine Isotope Stage 11, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18269, https://doi.org/10.5194/egusphere-egu25-18269, 2025.
