Global climate change is particularly pronounced in the Arctic regions, widely recognized as a "climatic hotspot" by the scientific community. This phenomenon, known as Arctic amplification refers to the accelerated increase in Arctic surface temperature compared to the global average. This process drives the ongoing loss of Arctic sea-ice volume and intensifies the ice-albedo feedback mechanism. Key physical drivers include the increased intrusion of warm Atlantic Water into the Arctic Ocean, which profoundly impacts biogeochemical cycles. Over the past decades, the CNR-ISP has developed marine and atmospheric observatories in the Svalbard region. These include three moorings (MDI, KIM, MAP) measuring biogeochemical parameters along the water column in the Kongsfjorden-Krossfjorden fjord system, and the land-based platform, the Amundsen-Nobile Climate Change Tower (CCT), measuring atmospheric parameters. As part of the ITINERIS PNRR project, the moorings were equipped with advanced biogeochemical sensors capable of monitoring Essential Ocean Variables, enablingthe study of seasonal and annual dynamics of suspended marine particles and nutrients. Between 2022 and 2024, contrasting environmental conditions shaped the dynamics of particulate matter and nutrients. One striking difference between the two years was the intrusion of Atlantic water observed at the end of summer in 2023 which extended to the inner Kongfjorden. Additionally, the timing of the spring phytoplankton bloom between 2023 and 2024 shifted, and also the terrestrial input from summer glacier melting exhibited significant variability. The spring phytoplankton bloom begins when PAR increases after the polar night nutrient concentrations are high due to autumn replenishment and winter water convection, and the influence of Atlantic Water on nitrate replenishment rates is evident. The timing of the spring bloom results from a complex interplay of atmospheric and marine factors. In the inner part of the Kongsfjorden, suspended matter concentrations are primary driven by glacial meltwater inputs, which contributes to low-salinity surface waters within the fjord. These findings underscore the intricate relationships between environmental changes, particle dynamics, and nutrient cycling in Svalbard.

How to cite: Paladini de Mendoza, F., Miserocchi, S., Giordano, P., Giglio, F., Mazzola, M., and Langone, L.: Seasonal particle dynamics in Kongsfjorden during two years of contrasting environmental conditions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19282, https://doi.org/10.5194/egusphere-egu25-19282, 2025.

The Arctic total sea ice extent has rapidly declined since the beginning of satellite observations. This decline materialized into record sea ice lows in the summers of 2007 and 2012. Those sea ice lows exhibit an important spatial heterogeneity and are likely caused by different dynamic and thermodynamic drivers of atmospheric and oceanic origins. Using the global ocean–sea ice model NEMO4.2-SI³ in the same setup but at three different horizontal resolutions (namely, 1/12°, 1/4° and 1°), we thoroughly examine the most extreme sea ice states simulated in summer by the model from a mass balance perspective. This method allows to disentangle the dominating mechanisms leading to the sea ice lows, such as dynamic redistribution and compression of sea ice in 2007, or preconditioning and excess basal melt in 2012. It also highlights the importance of processes at the ice-ocean interface to drive the evolution of sea ice at all considered temporal scales. We then compare how increased spatial resolution, allowing for the simulation of finer-scale physical processes such as ocean eddies, impacts the modelled sea ice thickness and concentration distribution, as well as the different ice mass fluxes. A particular attention is being paid to the influence of ocean heat content anomalies, as increased horizontal resolution provides a more realistic simulation of heat inflow in the Beaufort Gyre through subsurface eddies of Pacific origin. This study highlights the benefits of increased spatial resolution for realistically simulating the Arctic sea ice cover and weighs them with the associated computational cost. The decomposition of the ice mass budget into its different thermodynamic and dynamic terms puts forward the often downplayed role of the ocean in determining the interannual variability of Arctic sea ice and provides a stepping stone for further studies.

How to cite: Richaud, B., Massonnet, F., Fichefet, T., Topal, D., Barthélemy, A., and Docquier, D.: Does increased spatial resolution improve the simulation of Arctic sea ice lows in NEMO4.2-SI3?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6518, https://doi.org/10.5194/egusphere-egu25-6518, 2025.

The polar oceans, the high-latitude Earth systems, and the Earth climate system as a whole are strongly affected by the Antarctic and Greenland ice sheets. The recent developments of global climate models have allowed to accounting for the effects of the ice sheets either indirectly via parameterizations of freshwater fluxes, or via infrequent coupling between stand-alone ice sheet models and other climate models' components. The latter approach typically does not conserve mass across the model comonents.  In order to address these issues, we have developed a global ocean-cryosphere model iOM that includes synchronously coupled Antarctic and Greenland ice sheets in addition to sea ice and icebergs. The results of global simulations forced by the EAR-Interim reanalysis show strong seasonal and subseasonal variability in the ice-sheet/ocean interactons, demonstrating the importance of a tight synchronous coupling between the ice sheet and the ocean model components. iOM will allow us to explore interactions and feedbacks between the polar oceans and cryosphere on the subseasonal to decadal timescales.

How to cite: Sergienko, O., Huth, A., Harrison, M., and Schlegel, N.: Impacts of synchronously coupled dynamic ice sheets in the GFDL Global Ocean Cryosphere Model iOM, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3788, https://doi.org/10.5194/egusphere-egu25-3788, 2025.

Numerical model simulations are an essential tool for assessing effects of global warming on the climate system in future greenhouse gas concentration scenarios. Commonly, these simulations cover only the next few centuries or use low-complexity models for longer periods. However, to assess the dynamics of Earth system components with long response times like the ocean or ice sheets, multi-millennial simulations with comprehensive Earth system models are essential.
Here, we present multi-millennial simulations with the complex Earth System Model AWIESM, covering an integration time beyond the typical CMIP time scale. The model runs on a multi-resolution grid with a horizontal resolution of up to 20 km in high latitudes. The model includes an interactive ice sheet for the Greenland domain. The simulations are forced with transient greenhouse gas concentrations obtained from model simulations with the Earth System Model of intermediate complexity CLIMBER-X with an interactive carbon cycle, covering overshoot scenarios that enable assessment of long-term ice sheet and ocean dynamics.
Our results reveal a scenario-dependent weakening of the Atlantic Meridional Overturning Circulation (AMOC), followed by partial recovery over the next millennium. All scenarios show sea ice-free or nearly sea ice-free summer conditions in the northern and southern hemispheres. Winter sea ice shows an asymmetric response under future warming. While Arctic winter sea ice changes are small in low- to medium-emission scenarios, Southern Ocean winter sea ice shows a large reduction even in low-emission scenarios. The Greenland ice sheet shows a continuing ice mass loss during the next millennium, even with decreasing greenhouse gas concentrations in medium-emission scenarios. The main area of ice loss is West Greenland.
These findings underscore the importance of long-term simulations with comprehensive Earth system models to understand the complex, delayed responses of key climate system components and their broader implications for the Earth system.

How to cite: Ackermann, L., Knorr, G., Willeit, M., and Lohmann, G.: Multi-millennial future warming scenarios with the comprehensive Earth system model AWIESM, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15910, https://doi.org/10.5194/egusphere-egu25-15910, 2025.

Atlantification is a major phenomenon associated with rapid changes in the Arctic Ocean, including anomalous sea-ice loss, warming and salinification of the near-surface, enhanced mixing and changes in the ecosystem structure. Despite anomalous transport of Atlantic water in the Barents Sea/Fram Strait region is among the recognized causes of Atlantification, this phenomenon remains poorly characterized in the context of the historical (1850-present) period, hence far from being fully understood.

In this contribution, we illustrate recent progress of the Italian funded project “ATTRACTION: Atlantification dRiven by polAr-subpolar ConnecTIONs in a changing climate” that aims at providing a historical perspective on Atlantification by integrating observational evidence over the last decades, paleo-reconstructions and numerical climate simulations. We show results from a multi-model ensemble of historical climate simulations contributing to CMIP6 and depict robust traits of the simulated Atlantification across models and realizations toward fingerprinting the phenomenon at the gateway of the Arctic Ocean and toward a robust definition of an index for its quantitative characterization.

How to cite: Zanchettin, D., De Rovere, F., and Rubino, A.: Atlantification in a multi-model ensemble of historical climate simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3623, https://doi.org/10.5194/egusphere-egu25-3623, 2025.

Reconstructing climate patterns from the Common Era is necessary for placing modern human-driven climate changes within the context of natural climatic variations. This is particularly relevant for the Arctic, which is warming faster than any other. This global trend is tied to rapid sea ice loss and the increasing influx of Atlantic waters into the Arctic basin, a phenomenon called "Atlantification". In this context, we reconstruct the last centuries paleoenvironmental changes in the Arctic region from sediment cores strategically located along the Barents Sea (HH1141, 74.015°N 21.071°E, -285 m; HH1181, 74.081°N 21.362°E, -298 m water depth; HH969, 76.765°N 35.831°E, -174 m water depth), and on the northern margin of the Svalbard Archipelago (KH21-234-04 (80.3531ºN 16.308ºE, -394 m water depth), based on geochronological and geochemical analyses, benthic foraminiferal data and organic biomarkers. The Age-depth are based on excess ²¹⁰Pb, and are extrapolated down-core, assuming stable sediment accumulation rates (SAR) before the 20th century. The results allow us to identify two main oceanographic intervals. Pre-1900 ys CE, the dominance of Elphidium clavatum, Cassidulina reniforme, Islandiella helenae, Islandiella norcrossi, Stainforthia feylingi, Stainforthia loeblechi, together with a high concentration of biomarker (spring sea ice biomarker IP₂₅, and alkenones), indicate cold conditions. The second interval, corresponding to the 20th century, is characterized by the presence of Adercotryma glomeratum, Trifarina angulosa, Nonionellina labradorica, Globobulimina auriculata, Melonis barleanus, Buccella frigida, documenting warm water mass inflow related to the expand incursion of Atlantic waters. Moreover, biomarker analyses provide further details of the paleoceanographic conditions showing less seasonal sea ice influence in the region and the intrusion of Atlantic waters within the Arctic domain. This work sets another milestone in our understanding of the “Atlantification” process that is crucial to forecasting the environmental changes in this region that are susceptible to heat transport through the Atlantic gateways, which affects climate and ecosystems.

How to cite: Boretto, G. M., Tesi, T., Panieri, G., Simon, M. H., Sabino, M., Nogarotto, A., De Schepper, S., Weiner, A., Hefter, J., Giuliani, S., Langone, L., Mollenhauer, G., Belt, S., and Capotondi, L.: Atlantification at the Arctic Gateway: Past and Present Dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9378, https://doi.org/10.5194/egusphere-egu25-9378, 2025.

The aragonite skeletons of cold-water corals (CWCs) offer critical insights into the physico-chemical changes and dynamics of intermediate-depth water masses at high temporal resolution (e.g. sub-decadal). Previous studies have shown that variations in seawater temperature, water ventilation age, and water mass provenance can be reconstructed from measurements of skeletal Li/Mg ratios, paired U/Th and ¹⁴C, and neodymium isotopes, respectively. Notably, the solitary azooxanthellate scleractinian coral species Desmophyllum dianthus is particularly valuable due to its broad distribution, century-long lifespan, and layered skeletal growth, which facilitates the use of geochemical tracers at sub-decadal intervals.

In this study, we analysed several Desmophyllum dianthus samples collected in 2012 from the Northern Iceland Basin at depths of 570-700 m during the ICE-CTD R/V Thalassa expedition, using the Remotely Operated Vehicle Victor 6000 operated by IFREMER. Sub-samples of the coral skeletons collected along the growth axis were analysed for Li/Mg, stable isotopes (δ¹¹B, δ¹⁸O, δ¹³C), U/Th, ¹⁴C and Nd isotopes, with the aim to reconstruct the physico-chemical changes of the North Atlantic intermediate water masses, specifically the Iceland-Scotland Overflow Water, Sub-Arctic Intermediate Water and Western North Atlantic Central Water, and assess how their contributions have shifted over recent decades. The Li/Mg ratios provided sub-decadal temperature records, showing variations between ~2 to ~6 °C, closely linked to changes in Nd isotopic compositions. These findings can be explained by decadal fluctuations in the North Atlantic Oscillation and East Atlantic atmospheric patterns, which influence the strength of the Atlantic Subpolar Gyre, leading to changes in the amount of warmer Subtropical Gyre-sourced water or colder Subpolar Gyre-sourced water. Additionally, our results suggest a significant reduction, by about half over the past ~70 years, of the ISOW, pointing to an increased northward transport of warm subtropical waters in recent decades. This shift may have contributed to the recent warming in the Arctic region and a notable multi-decadal weaking of the Nordic Sea overflow currents.

How to cite: Montagna, P., Brocker, K., Border, E., Rigo, M., Ragnarsson, S. Á., Valdimarsson, H., Ólafsdóttir, S. H., Therre, S., Fohlmeister, J., Trotter, J., McCulloch, M., Lausecker, M., Blaser, P., Reverdin, G., Colin, C., and Frank, N.: Seawater temperature and water mass provenance changes over the last century in the North Atlantic Ocean reconstructed from cold-water coral geochemistry , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8884, https://doi.org/10.5194/egusphere-egu25-8884, 2025.

Observation-based reconstructions of Arctic sea surface temperatures in response to changing climate boundary conditions are critical to constrain climate sensitivity and evaluate the uncertainties of model simulations. On long and pre-instrumental timescales, this is only possible by employing climate proxies. Yet, most proxies of essential climate variables, such as sea surface temperatures (SST), suffer from limitations when applied to cold temperatures that characterize Arctic environments. These limitations prevent us from constraining uncertainties for some of the most sensitive climate tipping points that can trigger rapid and dramatic global climate change such as Polar Amplification, the disruption of AMOC, sea ice loss, and permafrost melting that are intrinsic to the polar regions. Here, we present a new approach to reconstructing sea surface temperatures (SST) using paired Mg/Ca - δ¹⁸O_c recorded in shells of the Arctic planktonic foraminifera Neogloboquadrina pachyderma. We show that in this proxy system, the Mg/Ca – palaeothermometry is affected by variations in seawater carbonate chemistry, which can be successfully quantified and removed from paleotemperature reconstructions allowing a reassessment of the absolute temperature and the magnitude of marine polar amplification to climate forcing on glacial-interglacial timescales. By applying this novel approach to existing records, we show that the magnitude of high latitude SST cooling during glacial periods has been underestimated and that the new estimate of SST change between the Late Holocene and the LGM exceeds model-based estimates of marine polar amplification by up to 3.0 ±1.0˚ C. Our findings open up opportunities to better constrain the oceanic carbonate system enabling a quantification of high-latitude ocean-atmosphere carbon exchange as well as to benchmark the performance of CMIP6 and future generations of climate models.

How to cite: Morley, A., de la Vega, E., Raitzsch, M., Bijma, J., Ninnemann, U., Foster, G., Chalk, T., Meilland, J., Cave, R., Büscher, J., and Kucera, M.: Reassessment and applications of the Mg/Ca - δ18Oc proxy system recorded in shells of the Arctic planktonic foraminifera Neogloboquadrina pachyderma, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19167, https://doi.org/10.5194/egusphere-egu25-19167, 2025.

How to cite: Mäkelä, M., Ribeiro, S., Pearce, C., Detlef, H., Salonen, J. S., Seidenkrantz, M.-S., and Heikkilä, M.: Marine ecosystem changes linked to climate and terrestrial freshwater inputs in a Northeast Greenland fjord over the Holocene, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17764, https://doi.org/10.5194/egusphere-egu25-17764, 2025.

We present planktic foraminiferal and planktic stable isotope records from central and eastern Arctic Ocean sediment cores with a particular attention on the development of the structure of upper water masses during two past interglacials (here termed IG3 and IG2), in comparison to the present Holocene (IG1). The age of interglacials IG2 and IG3 is currently under discussion. While the "classic" age model based on Jakobsson et al. (2000, Geology) would relate them to marine isotope (sub)stages (MIS) 5e and 5a, latest work (e.g., Song et al., 2023, Earth Sci. Rev.; Razmjooei et al., 2023, Quat. Sci. Rev.) would assign ages of MIS 11, 9, 7 or 5.

Stable oxygen and carbon isotopes from polar planktic foraminifers Neogloboquadrina pachyderma give clues on their habitat within the upper water column which today is characterized by an ice-covered low-saline cold surface layer, underlain by high-saline warm Atlantic Water. Sediments from IG2 and IG3 containing also subpolar planktic foraminifers Turborotalita quinqueloba show oxygen isotope values of close to modern ones, indicating a similar water mass structure as today, with a transition level between freshwater-rich and Atlantic Water. Carbon isotope values are lower and may point at a higher bioproductivity due to less sea ice and a decomposition of carbon in the upper waters. Interestingly, in the sediments underneath, which are barren in T. quinqueloba but contain abundant N. pachyderma, both oxygen and carbon isotopes are significantly higher. These data can be interpreted as evidence of a strongly stratified water column, a deeper habitat of the foraminifers, a strong subsurface advection of Atlantic Water and more sea ice during the early phases of IG2 and IG3. In cases, due to a lack of carbonate microfossils this interval is not represented in all analyzed cores. We assume that near-surface salinities were below the tolerance limit of planktic foraminifers in the very early parts of IG2 and IG3, probably due to a strong influence of meltwater from disintegrating ice sheets on northern Eurasia in the preceding glacial stages. Our results reveal a two-step development of conditions in the central Arctic during previous warm intervals. In the first part, the uppermost water column (including the habitat depth of T. quinqueloba) always had very low salinties due to freshwater discharge from ice sheets on the continents. Only in the second part Atlantic Water was shoaling and allowed the occupation by shallow-dwelling T. quinqueloba. Data from the Kara Sea continental margin suggest that upper water conditions in the eastern Arctic remained under strong freshwater influence, at least throughout IG2.

How to cite: Spielhagen, R. F., Bauch, H. A., and Mackensen, A.: Atlantic Water distribution in the central and eastern Arctic Ocean during past interglacials, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6159, https://doi.org/10.5194/egusphere-egu25-6159, 2025.

A rapidly warming climate with substantial polar amplification will lead the Arctic becoming ice free during summer. An Arctic that „turns blue“, i.e. that changes from a current Arctic Ocean covered by high-albedo sea ice to a future low-albedo ice free water surface, may occur as early as the 2050s even under low emissions scenarios (Kim et al., 2023). Absence of summer sea ice will further exacerbate Arctic warming and will have ramnifications from regional to global scale (Bruhwiler et al., 2021).

The study of past warm climate states with significantly reduced prevalence of Arctic sea ice enables an integrated proxy-data and climate modelling approach. This provides a valuable out-of-sample test for climate models from which future projections are derived and may help us to better understand processes and climate patterns related to a blue Arctic.

Based on the Last Interglacial (~127,000 years ago), a time when orbital parameters caused much increased boreal high-latitude insolation forcing in particular from boreal spring to boreal autumn, the fourth iteration of the Paleoclimate Modelling Intercomparison Project (PMIP4) identified in their simulation lig127k substantial model-spread of simulated minimum annual Arctic sea ice conditions (Kageyama et al., 2020; Sime et al., 2023). To enable a better understanding of the origin of model-model discord the paleoclimate science community has proposed simulation abrupt-127k (Sime et al., in prep.) as part of the FastTrack portfolio of the seventh interation of the Climate Modelling Intercomparison Project (CMIP7). While simulation abrupt-127k inherits orbital and greenhouse gas parameters of PMIP4 simulation lig127k, its layout follows the approach of CMIP simulation abrupt-4xCO2, where the initial scientific focus is on a comparably short period (~100 model years) after model initialisation rather than on the quasi-equilibrated climate as in PMIP4 simulation lig127.

With this presentation we will outline rationale and utility of CMIP7 FastTrack simulation abrupt-127k to a) increase the model ensemble from the classical PMIP to the wider CMIP framework; b) focus on processes and feedbacks that translate modified climate forcing into Arctic climate towards refining our understanding of the apparent model-model discord found in lig127k; c) enhance analysis of simulated sea ice conditions and dynamics based on the standardized protocol for sea-ice related climate model outputs by the Sea-Ice Model Intercomparison Project (SIMIP; Notz et al., 2016).

How to cite: Stepanek, C., Sime, L. C., Diamond, R., Brierley, C., Schroeder, D., Kageyama, M., and Malmierca-Vallet, I.: The CMIP7-PMIP FastTrack abrupt-127k simulation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15665, https://doi.org/10.5194/egusphere-egu25-15665, 2025.

The setting of a consensual climate history of the Arctic Ocean spanning the last major climatic cycles is still unachieved despite recent converging views about the chronostratigraphy of marine archives from this ocean. Under both permanent and seasonally-opened sea-ice covers, sedimentary recordings present anomalies, ranging from hiatuses under thick ice-shelf covers, during glacials, to winnowed or mixed sequences generated by deep-density currents, under seasonally freezing sea-ice conditions during interglacials or interstadials. In opposition, short, early, or late-glacial events (e.g., continental ice surging and glacial lake drainage events) may have led to the deposition of relatively thick layers occasionally with reworked material. Accordingly, time interpolation between dated layers and within these layers is misleading, and lateral sediment advection leads mixed microfossils and biomarkers records, thus to biased paleoceanography/paleoclimate inferences. Interglacial as well as glacial sequences are subsequently poorly recorded. Along ridges, erosion of fine particles by sinking brines and deep density-driven current, with redeposition in sheltered/deeper sites, further results in the mixing of fossil populations. This process and its impact on paleoecological reconstructions are well-documented by ¹⁴C records spanning the Holocene-Marine Isotope Stage 3 interval. In several cores raised from central Arctic ridges, for example, a few centimeters of mixed Holocene and Marine Isotope Stage 3 assemblages illustrate this interval. Nonetheless, the positions of the last two interglacials in deep sedimentary cores may be set with some confidence based on the relative decay of sedimentary excesses in U-series isotopes (²³¹Pa vs ²³⁰Th) and detrital feldspar grain OSL-ages. With the complementary support of paleomagnetic records, a tentative outline of the major late Quaternary glacial/interglacial events may be proposed, as illustrated here by records from the Chukchi Sea margin. In this area, high interglacial/interstadial sea-level intervals allowed Pacific Water influx through the shallow Bering Strait, as recorded by radiogenic Nd-isotope excursions and enhanced Si-fluxes (thus high primary productivity). High sea levels also resulted in the flooding of shelves, leading to high manganese fluxes in the deep basins. These provided a cyclostratigraphic tool for the correlation of records throughout the Arctic Ocean, as documented in several studies of the last decades. 

How to cite: Hillaire-Marcel, C., de Vernal, A., and Song, T.: Inserting the Arctic Ocean into the global late Pleistocene climate/ocean system: The Graal Quest?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7420, https://doi.org/10.5194/egusphere-egu25-7420, 2025.

The Arctic is currently undergoing rapid warming, which in the near future is expected to result in summers with an ice-free Arctic Ocean interior, and winters having thinner, and more mobile ice. Changes in sea-ice cover will have profound impacts on Arctic oceanography, its marine ecosystem, and ultimately on our climate from regional to global scales. To better understand what will happen in a changing future, we must look into the past. Arctic marine sediments provide a range of proxies that provide valuable palaeoceanographic, and palaeoclimatic information, documenting changes to the cryosphere. Yet, a confident interpretation of palaeoceanographic, and palaeoclimatic changes across glacial cycles of the Pleistocene is still hampered by our inability to accurately date Arctic marine sediments.

Studies conducted by Jakobsson et al. in the early 2000s transformed age-model interpretations in the Arctic following the identification of the coccolithophore Gephyrocapsa huxleyi (formerly known as Emiliania huxleyi) in a sediment core from the Lomonosov Ridge. Although G. huxleyi evolved globally ca 290 ka during MIS 8 (300-243 ka), it is generally believed that this species first appeared in the Arctic Ocean during the last interglacial period (MIS 5, 71-130 ka). The biostratigraphic datum provided by the first appearance of this species has therefore been central to much palaeoceanographic research conducted in the Arctic. However, identifying nannofossils in Arctic Ocean sediments is non-trivial, as their mineral remains are often poorly preserved or entirely absent due to unfavorable taphonomic conditions. This has led to ambiguous age estimates, as revealed by a recent study by Razmjooei et al. (2023) revising the calcareous nannofossil biostratigraphy in the Arctic, indicating that previously inferred sub-stages of MIS 5 may actually represent full interglacial periods rather than interstadials.

Recent advances using sedimentary ancient DNA (sedaDNA) now permit genome-based approaches to identify calcareous photosynthetic algae in marine sediments. We hypothesize that the sedaDNA approach may provide a “palaeogenomic biostratigraphic” age control when the conventional fossil-based approach is not usable due to poorly preserved or absent fossil remains. Given its importance in Arctic biostratigraphy, and since this is the only coccolithophore with an existing reference genome, we focus on G. huxleyi. An initial pilot study analyzing 5 samples from one sediment core from the central Arctic Ocean has previously showed positive reads for G. huxleyi in sediment layers argued to be from the last interglacial (MIS 5). Expanding on this pilot-study, we conducted a high-resolution sampling, totaling 93 sedaDNA samples, of two additional cores from the central Arctic Ocean. By integrating metagenomics with fossil, and climate proxy data, we aim to more confidently place the first appearance of G. huxleyi in the biostratigraphic framework of Quaternary Arctic marine sediments.

How to cite: Ståhl, E., Linderholm, A., and O'Regan, M.: Exploring the use of sedaDNA to provide a palaeogenomic-based biostratigraphy in central Arctic Ocean sediments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17627, https://doi.org/10.5194/egusphere-egu25-17627, 2025.