As global temperatures continue to rise, model projections suggest that the Arctic Ocean could become seasonally ice-free by mid-century, raising critical questions for the Arctic research community: What could the Arctic Ocean look like in the future? How will the present changes in the Arctic affect and be affected by the lower latitudes? Which oceanic processes drive this sea-ice loss and how will they change in a sea ice-free Arctic? What aspects of the changing Arctic should observational, remote sensing and modeling programs prioritize?
In this session, we invite contributions from a variety of studies on the recent past, present and future Arctic. We welcome submissions that explore interactions between the ocean, atmosphere, and sea ice; Arctic processes and feedbacks; small-scale processes, internal waves, and mixing; sources of freshwater change and their impacts; and the interactions between the Arctic and global oceans. We especially welcome submissions that take a cross-disciplinary approach, focusing on new oceanic, cryospheric, and biogeochemical processes as well as their connections to land.
We want to spark discussions on future plans for Arctic Ocean measurement, remote sensing, and modeling strategies, including the upcoming CMIP7 cycle and ways to validate and improve models using observations. We encourage submissions on CMIP modeling approaches and recent observational programs like MOSAiC, the Nansen Legacy Project and the Synoptic Arctic Survey. We also welcome anyone involved in planning the upcoming International Polar Year 2032-33 to participate in our session and contribute to the discussions.
Orals: Mon, 4 May, 08:30–12:30 | Room L3
Lake ice cover is a key component of the Earth’s cryosphere system. The absence of lake ice can have important implications for local energy budgets and influence the occurrence of extreme weather events, such as lake-effect snow systems. Additionally, ice formation is critical in the establishment of ice road transportation networks in areas such as Northern Canada, which allow for the transportation of goods and people during winter months. Within the WMO’s Global Climate Observing System (GCOS) Lakes Essential Climate Variable (ECV), lake ice has been identified as a key indicator for monitoring climate change. While long-term ground-based records of lake ice exist, the quantity of these measurements has declined, and over the last two decades, remote sensing has become increasingly relied on to provide information about global lake ice conditions. This is reflected in the multitude of operational lake ice products now available, including: the Multisensor Snow and Ice Mapping System (IMS), the MODIS Snow and Ice Cover, ESA Lakes CCI+ Lake Ice, and the Copernicus Land Service Lake Ice Extent products. These products exhibit different advantages and disadvantages related to the quality of retrievals, number of lakes/spatial resolution, and temporal coverage, which can limit their application for real-time monitoring or understanding of changes in lake ice conditions for smaller lakes.
This presentation will showcase a new operational product, specifically focused on providing daily lake ice coverage for lakes in Canada larger than 2.25 km2. The product is adapted from the processing chain utilized for the generation of the ESA CCI+ Lake Ice Cover Product but includes data for more than 36,000 lakes (500 m grid). The product is derived from over 1.5 PB of MODIS optical data and captures variation in the ice coverage during the two most recent decades (2000 – 2023). This presentation will describe and discuss the general trends and spatial patterns in lake ice cover across Canada, with connections to recent temperature trends. Additionally, an application of the product for monitoring ice roads will be highlighted by showcasing how the resolution of the product can be used to evaluate the timing of ice cover for lakes along key identified ice routes, such as the Tibbit to Contwoyto, Wekweèti, and Gamèti winter roads.
How to cite: Murfitt, J. and Duguay, C.: Canadian Lake Ice Cover in the Early 21st-Century, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2593, https://doi.org/10.5194/egusphere-egu26-2593, 2026.
The Arctic region is undergoing a rapid and intense transformation driven by global climate change. Paradoxically, this coincides with a generalized decline in the density of hydrometric stations, resulting in fragmented spatiotemporal river discharge time series data that are insufficient to capture the complexity of ongoing dynamics. Under these challenging context, Arctic basins play a crucial role in regulating the freshwater budget, influencing ocean circulation and sea ice formation, and acting as a "litmus test" for the hydrological cycle's response to warming.
To address the scarcity of in-situ data, our work aims to provide continuous river discharge and runoff estimates at a daily scale and 0.25° spatial resolution for the entire continental Pan-Arctic region over the period 2003–2022. We employ STREAM model (SaTellite based Runoff Evaluation And Mapping; Camici et al., 2022), a semi-distributed conceptual hydrological model forced exclusively by temperature data and satellite observations, including precipitation, soil moisture, snow cover fraction, and Terrestrial Water Storage (TWS) anomalies from GRACE (Gravity Recovery and Climate Experiment) and its Follow-On mission (GRACE-FO). The integration of gravimetry data represents a key innovation—particularly relevant in the context of the future NGGM-MAGIC (Next-Generation Gravity Mission / Mass-change And Geophysics International Constellation) mission—as it enhances the characterization of hydrological processes in cold regions where TWS changes significantly drive river discharge and runoff variability. The model was first calibrated on 15 "donor" Arctic basins, achieving a median Kling-Gupta Efficiency index (KGE) of 0.80. To cover ungauged areas, we developed a regionalization framework based on aridity-index clustering, extending estimates to the entire Pan-Arctic domain. The resulting dataset was independently validated against 26 gauging stations and benchmarked against existing reanalysis products.
Results demonstrate that the regionalized model faithfully reproduces discharge seasonality and interannual variability over 70% of the Pan-Arctic area. Furthermore, trend analysis reveals statistically significant runoff trends in 18% of the domain, highlighting that the Pan-Arctic does not exhibit a uniform response to climate change, but rather diverse, localized reactions.
This work provides a consistent hydrological baseline based solely on satellite data, filling the gaps left by fragmented in-situ river discharge monitoring networks and offering a robust tool to investigate the interactions between climate change and hydrological extremes in the Pan-Arctic region, a critical climate hotspot.
How to cite: Leopardi, F., Saltalippi, C., Dari, J., Brocca, L., Saemian, P., Sneeuw, N., Tourian, M., and Camici, S.: Quantifying Pan-Arctic Freshwater Fluxes: A 20-Year Satellite-Based Daily River Discharge and Runoff Dataset, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6981, https://doi.org/10.5194/egusphere-egu26-6981, 2026.
The climate system is approaching dangerous tipping points, with the potential collapse within decades of critical components such as the Greenland Ice Sheet and the North Atlantic Subpolar Gyre posing severe risks to European weather and global climate stability. Changes in Arctic freshwater, driven by changes in ice-sheet and sea-ice melt and atmosphere-ocean-ice interactions, play a central role in these risks by influencing ocean stratification, deep water formation and air-sea fluxes. Despite the urgent need for early warnings, major gaps remain between existing observations and the data required to constrain predictive models, limiting confidence in future projections.
Earth-orbiting satellites and in situ observations provide essential information on large-scale ocean, cryosphere, and atmosphere change, but they struggle to capture fast processes at kilometre and sub-kilometre scales in complex regions such as marginal ice zones. A different type of observations is needed to quantify the role of these processes in exchanges of freshwater, heat, and momentum that the Arctic and the Greenland Ice Sheet to the North Atlantic Subpolar Gyre.
This paper will introduce AEROSTATS (Aerial Experimental Remote sensing of Ocean Salinity, heaT, Advection, and Thermohaline Shifts), a UK-led international project designed to demonstrate a new approach to long-term, low-cost, low-carbon monitoring of Arctic freshwater processes in Greenland’s dynamic ocean–ice margins. AEROSTATS focuses on innovative airborne platforms capable of remote, high-resolution imaging of total surface current vectors, near-surface winds, sea surface salinity, ocean colour, and sea surface temperature at 1-10km and sub-daily scales.
Funded as a high-risk, forward-looking project, AEROSTATS seeks to collect and integrate data from new airborne instruments, in situ surface and subsurface platforms, spaceborne sensors, and high-resolution reanalyses and models. A core element is a 2028 year-round field campaign in the Greenland/Subpolar Gyre region deploying airborne systems to observe freshwater-driven processes across seasons. By combining multi-platform observations with models and reanalyses using digital tools such as machine learning and digital twins, AEROSTATS aims to establish new long-term monitoring capability to substantially improve early warning for freshwater-related tipping points.
How to cite: Gommenginger, C., Martin, A. C. H., McCann, D., Marquez Martinez, J., Lavender, S., Lichtman, D., Buckingham, C., Marzocchi, A., Prime, T., Clément, L., Josey, S., and Grist, J.: Towards an Early Warning System for Arctic Freshwater-Driven Tipping Points in the Greenland Ice Sheet and North Atlantic Subpolar Gyre with AEROSTATS, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5839, https://doi.org/10.5194/egusphere-egu26-5839, 2026.
The Arctic Ocean is changing rapidly, and Atlantic Water circulation plays a key role in the warming, sea-ice decline, and ecosystem changes observed in the Arctic. Still, we have limited understanding of the pathways and circulation times of Atlantic-derived water both at surface and mid-depth layers in the Arctic Ocean, and their evolution over time.
Here, we present the water mass composition and circulation in the central Arctic Ocean in 2021 and assess temporal changes thereof between 2011 and 2021 by using the long-lived anthropogenic radionuclides I-129 and U-236 in the Transit Time Distribution model. Key findings for 2021 include a decline in surface radionuclide concentrations between the Amundsen and Makarov Basins, pointing to substantial fractions of Pacific Water reaching the Lomonosov Ridge from the Amerasian side. Similar radionuclide concentrations in halocline waters on both sides of the Lomonosov Ridge suggest a common formation region of these waters with a clear Atlantic Water signal. North of Greenland, a mixture of waters from the Canada and Amundsen Basins is observed at both surface and mid-depth. Between 2011 and 2021, we observe a shift of the Atlantic-Pacific Water front from the Makarov Basin towards the Lomonosov Ridge and an increase in circulation times in the mid-depth Atlantic layer. Overall, our findings provide a baseline of the circulation of Atlantic-derived waters in 2021 and provide evidence of circulation changes both in the surface and intermediate waters between 2011 and 2021.
How to cite: Wefing, A.-M., Payne, A., Scheiwiller, M., Vockenhuber, C., Christl, M., Tanhua, T., and Casacuberta, N.: Changes in water mass composition and circulation in the central Arctic Ocean between 2011 and 2021 inferred from tracer observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19573, https://doi.org/10.5194/egusphere-egu26-19573, 2026.
Earth system modelling is an important instrument to investigate climate change in an integrated way, taking into account the interactions between the different compartments of the Earth system. It is also an important tool to perform climate projections for different climate scenarios in order to take appropriate mitigation and adaptation measures. Such climate simulations are coordinated internationally as part of the World Climate Research Programme’s (WCRP) Coupled Model Intercomparison Project Phase 7 (CMIP7).
The Alfred Wegener Institute (AWI) will participate in the CMIP7 project with the Earth system model AWI-ESM3. This is being done as part of the German contribution to the Coupled Model Intercomparison Project (CAP7).
One focus of our work is the impact of anthropogenic aerosol forcing during the historical CMIP7 period. Earlier versions of the AWI climate model setup used a fixed aerosol climatology and thus clearly overestimated the temperature increase for the historical period due to the lack of changing direct and indirect aerosol effects. The implementation of transient aerosols brings the simulated historical period closer to observed trends.
In this presentation we will show first results of the CMIP7 historical experiment performed by the AWI-ESM3 high resolution model including the impact of transient aerosol forcing. We will discuss the results with respect to the Arctic regions and the comparison to observations and climate performance indices.
How to cite: Wieters, N., Streffing, J., Hajdu, L. H., Goessling, H. F., and Jung, T.: AWI-ESM3 high resolution model contribution to CMIP7: First results of the model response in the Arctic regions during the historical period, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17934, https://doi.org/10.5194/egusphere-egu26-17934, 2026.
The Atlantic Meridional Overturning Circulation (AMOC) plays a central role in the climate system by transporting and redistributing heat to depth, thereby regulating the effective heat capacity of the ocean under global warming. Observations and projections indicate a potential decline of the AMOC in response to climate change, with far-reaching climate consequences. The Nordic Seas are a key region for the overturning circulation, as dense water formation north of the Greenland–Scotland Ridge feeds the lower limb of the AMOC.
Within this context, the ARCTIC-FLOW project aims to improve our understanding of water mass transformation and overturning processes in the Nordic Seas. The project focuses on identifying the main regions of surface water transformation, quantifying water mass transformation rates, characterizing the temporal and spatial scales of dense water formation, and assessing the impact of extreme freshening events across different subregions of the Nordic Seas.
To support these objectives, we have developed a novel 11-year satellite-based time series of freshwater and density fluxes for the Arctic and sub-Arctic regions. This dataset is derived from the combination of satellite sea surface salinity, sea surface temperature, and surface velocity fields, together with information on mixed layer depth. The satellite products are evaluated and complemented using an extensive set of in situ observations and results from numerical model experiments.
In this contribution, we will present preliminary results on the variability of the newly developed satellite-derived density flux product, highlighting its relevance for studying variability of water-mass transformation processes in the Nordic Seas.
How to cite: Gonzalez Gambau, V., Arias, M., Bergas-Ques, J., Beszczynska-Möller, A., Gabarro, C., García-Espriu, A., Goszczko, I., Karcher, M., Karlsson, N. B., Kauker, F., Olmedo, E., Piracha, A., Ruiz-Sebastián, A., Sabia, R., Sagués, A., Turiel, A., Umbert, M., Vrettou, A., and Wearing, M.: Exploring density flux variability in the Nordic Seas through new satellite products: Insights from ESA’s Polar Science Cluster ARCTIC-FLOW project, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18611, https://doi.org/10.5194/egusphere-egu26-18611, 2026.
Arctic areas like the Beaufort Sea are commonly characterized by the formation of sub-surface acoustic ducts. Conversely, the eastern Arctic is known for its upward refracting propagation environment, which creates surface ducts. Using moored passive acoustic recorders in the Fram Strait in the eastern Arctic Ocean, we measured the average distribution of sound energy in the water column. The moorings were deployed by the CMRE Environmental Knowledge and Operational Effectiveness program and instrumented with several oceanographic sensors and acoustic recorders. Even though some acoustic recorders failed to record for the entire experiment, we characterized the vertical distribution of the ambient noise field. We measured the formation of temporary sound energy duct-type areas in the thermocline. Using Copernicus Marine service data, we investigated the effects of the sea ice concentrations, sea ice drift and distance to the sea ice edge on the vertical distribution of ambient noise. The distance from the ice edge had a negative correlation with sounds levels, while ice drift and concentration were not correlated to the overall sound levels. Simultaneous sound speed measurements revealed the presence of potential sound channels. We investigated the possible origin of the sound energy, and the formation of potential sub-surface ducts, applying range-dependent sound propagation modelling coupled with high-resolution output of the double nested CMRE’s Pan-Arctic ocean-sea ice model.
How to cite: Giorli, G., Falchetti, S., Russo, A., and Real, G.: Observations of ducting of acoustic energy in the Fram Strait., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22753, https://doi.org/10.5194/egusphere-egu26-22753, 2026.
Recent and rapid environmental changes in the Arctic Ocean lead scientists to re-evaluate the way they operate in this area. NATO STO Centre for Maritime Research and Experimentation (CMRE) leads the Nordic Recognised Environmental Picture (NREP) trial series in order to understand how a better characterization of the Arctic environment is possible and how it can help to build more accurate underwater acoustic modelling capabilities. NREP25 was conducted in the Greenland Sea from July 16th to July 27th 2025. On-board NATO Research Vessel (NRV) Alliance, underwater acoustic propagation experiments were performed in various Arctic environments (packed ice, marginal ice, open waters, brash ice), deploying in-house built receivers alongside other innovative solutions. NRV Alliance acted as the acoustic source, transmitting pre-defined sequences of known waveforms that will be used for probing the Arctic environment, in particular the interactions of sound waves with the space and time-dependent ice cover. The latter was estimated using a combination of remote sensing capabilities. First, a new prototype of ship-borne X-band RADAR provided a continuous estimation of the positions of the ice floes. Second, remote sensing imagery from diverse satellites (Sentinel, COSMO-SkyMed, SWOT and RADARSAT) provided high-resolution images of the sea ice cover, obtained from SAR processing, several times a day. NRV Alliance also served as a “floating ground control” for drone activities. Namely, high resolution photogrammetry and point-cloud LiDAR data were obtained from aerial drone surveys.
Oceanographic characterization was carried out through extensive CTD casts, as well as glider missions (with acoustic payloads as well). This characterization was used to design experimental configurations that were more likely to generate interactions of acoustic paths with the sea ice at the surface.
In addition, CMRE conducted specific characterization of the water ice interface by ROV inspection (with video, acoustic camera and altimetry data), and also ice coring (to be analysed at the centre).
An overall description of the experiment is presented, as well as an analysis of the data collected focusing on the contribution of remote sensing to the understanding of the underwater acoustic observations.
How to cite: Real, G., Pennucci, G., Akins, F. H., and Fabbri, T.: Multi-domain environmental sensing for underwater acoustics in the Arctic marginal ice zone., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22763, https://doi.org/10.5194/egusphere-egu26-22763, 2026.
Mercury (Hg) concentrations in Arctic biota are elevated relative to lower latitudes, posing an increased risk of adverse health effects for Arctic populations that rely on them as an important food source. Hg readily cycles through different environmental compartments such as air–soil–river before reaching sea waters where it becomes available for methylation to methylmercury and is readily taken up and magnified in the marine food web.
Warming climate is expected to further enhance air-soil-river exchange, increase river discharge, mobilize additional Hg loads from thawing permafrost, erosion melting glaciers and sea ice. A recent Arctic Ocean (AO) Hg mass budget indicates that Hg inputs exceed outputs, indicating either a missing sink or an imbalance due to ongoing changes.
We determined Hg stable isotope endmember signatures of Hg sources, including western Siberian organic-rich permafrost and mineral soils, and compile those with available literature data on endmembers. Central AO surface seawater samples were collected under trace metal clean conditions in Summer 2025 aboard RV ODEN and zooplankton samples in Summer 2015 aboard RV Polarstern. Solid samples were pre-concentrated using a double tube furnace set-up, while 40 L of sea water were pre-concentrated using a two-step purge and trap method. Hg stable isotopic composition was measured via online cold-vapor generation multicollector ICP-MS analysis.
We use the new Hg stable isotopes measurements together with available literature data to better constrain the Arctic Hg cycle by disentangling the relative importance of different Hg sources to AO surface waters, the entry point of Hg into the marine food web.
How to cite: Kleindienst, A., Barale, I., Lattaud, J., Kohler, S. G., Heimbürger-Boavida, L.-E., Pokrovsky, O. S., Sonke, J., and Jonsson, S.: Constraining Mercury Sources to the Arctic Ocean Using Mercury Stable Isotopes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21848, https://doi.org/10.5194/egusphere-egu26-21848, 2026.
The Arctic Ocean (AO) is a critical sink for anthropogenic carbon (Cant), sequestering emissions via intermediate and deep water formation, storing it for long periods of time. Understanding the timescales of these ventilation processes is essential for calculating the current inventory of Cant as well as predicting the AO’s capacity to store CO2 in a warming climate. However, observational constraints remain limited; while standard transient tracers (SF6, CFC-12) and other radionuclides successfully resolve surface and intermediate layers, they often fail to capture the older waters of the deep basins. Atom Trap Trace Analysis (ATTA) has opened a new way to measure deep ocean water residence times by using the radioactive noble gas 39Ar. Here we show the first fully resolved vertical profiles of Arctic ventilation and Cant using Transit Time Distributions (TTDs) derived from a novel combination of short-lived tracers and long-lived radioisotopes (39Ar, 14C). Their vertical distribution brings key information on ocean ventilation and hence the storage of anthropogenic carbon. We apply a Bayesian Inference framework to fit the TTD parameters from the different tracer data constraints.
We find that the mixing regime across the Nansen, Amundsen, and Makarov Basins is more advection-dominated than previously assumed in the deep basins. The profiles reveal that the Arctic stores up to 33% of its total Cant inventory below 1,500 m—vastly exceeding the global ocean average of ∼7%. While the deep Makarov Basin holds roughly half the carbon content of the Eurasian Basin, both reservoirs play a disproportionate role in deep sequestration. Conversely, we demonstrate that for the Atlantic Water Layer, which contains the bulk of the carbon, adding long-lived radioisotopes offers negligible improvement over standard tracers. These findings refine the Arctic carbon budget and highlight the necessity of adding long-lived radionuclides for constraining the deep ocean sink.
How to cite: Arnedo, I., Scott, S., Negele, S., Arck, Y., Meienburg, F., Mandarić, N., Junkermann, A., Wachs, D., Casacuberta Arola, N., Tanhua, T., Oberthaler, M., and Aeschbach, W.: A Multi-Tracer Study of Ventilation and Anthropogenic Carbon Storage in the Arctic Ocean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12700, https://doi.org/10.5194/egusphere-egu26-12700, 2026.
The launch of the altimetric satellite SWOT (Surface Water and Ocean Topography) was a revolution in oceanography and hydrology. With its120 km swath width, a spatial resolution of 500m² (in Low Resolution acquisition mode) and an instrumental random error significantly lower than the one from nadir altimetry, the Ka-Band Radar Interferometer (KaRIn) onboard SWOT mission also present a huge potential to develop applications in the polar regions. Indeed, the SWOT product enables the observation of leads, icebergs and polynyas (Dibarboure and al 2024) through the measures of surface topography and backscatter coefficient.
The surface discrimination between leads and floes is the first step toward polar ocean monitoring, ice thickness and snow depth estimations. However because of the complexity of the surface (different surface roughness properties in the leads, presence of melt pounds) added to residual sensing errors (residual KaRIn random error, residual systematic errors, …) this first required achieved is not straightforward. Therefore several classification approaches were developed : one based on a statistical method (Markov Random Field), one based on an unsupervised machine learning method (Kmeans) and another one based on a supervised machine learning method (XGBoost). The objective of this paper is thus to present the results of these methods (their robustness, strengths and weaknesses) through local comparisons with respect to optical, SAR images and global comparison with existing state of the art products (OSISAF ice concentration products).
How to cite: Treboutte, A., Jestin, G., Boy, F., Raynal, M., Fleury, S., and Dibarboure, G.: Sea Ice classification in SWOT L3 products , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9359, https://doi.org/10.5194/egusphere-egu26-9359, 2026.
The NASA–ISRO SAR (NISAR) mission will provide the first spaceborne dual-frequency (L- and S-band) radar observations of polar regions, which is capable of acquiring fully-polarimetric acquisitions. While L-band polarimetric capabilities are relatively well understood from previous missions and airborne campaigns, the S-band component represents a novel observational opportunity whose potential for sea ice characterization remains largely unexplored. Because of the fast changing sea ice regime in the Arctic, there is a growing need to understand what observational capabilities emerging synthetic aperture radar (SAR) system can offer for sea ice monitoring.
This study leverages very high resolution airborne UAVSAR imagery at fully-polarimetric mode from winter and summer seasons in the Beaufort Sea to investigate how dual-frequency SAR can provide separability of thinner sea ice classes over the annual thermodynamic cycle. We examine SAR backscatter and a range of parameters derivable from fully-polarimetric data to assess their utility in ice type discrimination.
Given S-band's intermediate wavelength between L-band and C-band, we anticipate distinct scattering behavior arising from its sensitivity to ice properties at scales different from those of established frequencies. This study aims to characterize how L- and S-band respond to varying ice conditions across seasons and to explore whether the two frequencies offer complementary information for ice classification. Also, we would like to develop a ranking for most efficient parameters from separability matrices. These findings will inform the development of sea ice monitoring frameworks for the imminent NISAR era.
How to cite: Mahboob, M. and Mahmud, M.: Fully polarimetric dual-frequency radar monitoring of Arctic sea ice, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-458, https://doi.org/10.5194/egusphere-egu26-458, 2026.
The Beaufort Gyre is a prominent feature of Arctic Ocean circulation and a focal point for studies of Ekman dynamics. Midlatitude gyres are primarily forced by atmospheric winds, and Ekman pumping can be directly estimated from the atmosphere–ocean stress. However, in polar regions, the presence of sea ice modifies and mediates momentum transfer from the atmosphere to the ocean. In this context, the surface stress can be expressed as a weighted sum of atmosphere–ocean stress and ice–ocean stress, with the weighting determined by sea ice concentration. In regions of open water, the surface stress is dominated by direct atmospheric forcing, whereas in areas of high ice concentration it is largely controlled by the ice–ocean stress. Under these conditions, internal rheological stresses within the ice pack also play a role in redistributing the stress applied by the atmosphere before it is transmitted to the ocean. The combined action of surface and internal stresses determines the effective forcing felt by the ocean and has direct implications for Ekman pumping and the resulting circulation. To investigate the roles and influence of these stresses, we use output from the MIT general circulation model (MITgcm).
We begin with the free drift regime, in which internal rheological stresses are neglected, and assess the ability for this regime to produce sea ice drift. Observational data in the Arctic are limited, so we attempt to recover sea ice drift using readily available measurements, such as wind speed and altimeter derived sea surface height. Sea ice drift is first inferred from the balance between atmospheric and oceanic stresses, which captures the large scale features of motion reasonably well. Next, an iterative solver is applied to include the effects of Coriolis and sea surface tilt. Finally, comparison with the full rheology case shows that internal ice stress is necessary to reproduce the small scale features of ice motion. In regions of high ice concentration and during winter, rheological stresses become essential, and the free drift approximation no longer captures the observed motion.
Motivated by the limitations of the free drift approximation, the second part of this project examines how the presence of sea ice modifies the atmospheric stress transmitted to the ocean. In open water, wind stress acts directly on the ocean surface, whereas in ice covered regions the stress is applied to the ice and redistributed internally through rheological processes before reaching the ocean. Consequently, the stress experienced by the ocean differs from that applied at the surface. We analyze how internal ice stresses transform and redistribute atmospheric work across the ice pack, altering the effective surface stress and modulating Ekman pumping and ocean circulation within the Beaufort Gyre.
How to cite: Webb, E., Straub, D., and Tremblay, B.: Role of Ice Rheology in Modulating Surface Stress and Sea-Ice Drift in the Beaufort Gyre, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16244, https://doi.org/10.5194/egusphere-egu26-16244, 2026.
Observational evidence indicates enhanced ocean convection near the sea ice edge in the Nordic Sea. However, whether sea ice retreat in a warming climate would further strengthen convection remains uncertain. Using a high-resolution climate model and comparing it with a low-resolution version, we find a more pronounced future increase in convection in the Arctic Ocean. A key reason for this difference is that at higher resolution, resolved boundary currents transport high-density Atlantic water more efficiently toward high latitudes along the ocean boundary. As sea ice retreats and low-density freshwater input diminishes, the high-density water can no longer subduct. Meanwhile, surface currents strengthen more than deeper currents, and the resulting shear weakens stratification before heat loss occurs. Our study suggests that future ocean convection and ventilation in the Arctic Ocean may be stronger than present projections from low-resolution models indicate.
How to cite: Gou, R., Guo, H., Liu, Y., Lohmann, G., and Wu, L.: Resolved boundary currents at high resolution contribute to stronger future ocean convection in the Arctic, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4435, https://doi.org/10.5194/egusphere-egu26-4435, 2026.
The Arctic Ocean has changed rapidly over recent decades as sea ice has declined, freshwater inputs have increased, and atmosphere–ocean coupling has evolved. Yet the resulting basin-scale variability in ocean mass remains poorly constrained because in situ observations are sparse and satellite altimetry is limited at high latitudes. Here we use satellite gravimetry from GRACE and GRACE-FO to quantify Arctic Ocean bottom pressure (OBP) variability from 2002 to 2024, providing a direct measure of mass redistribution that is independent of steric effects. To isolate dynamic ocean signals, we remove land leakage and eustatic contributions using a forward-modeling framework that accounts for self-attraction and loading. Empirical Orthogonal Functions (EOF) analysis of the residual OBP field reveals a leading-mode dipole pattern, with increasing ocean mass in the Beaufort Gyre region within the Canadian Basin and decreasing mass in the Kara Sea and Barents Sea. The corresponding principal component shows a robust strengthening over the two-decade record. While the underlying physical mechanisms warrant further investigation, the overall dipole structure is consistent with recent modeling studies suggesting intensified surface circulation under continued sea-ice loss. Overall, GRACE-derived ocean mass captures coherent, multi-decadal Arctic circulation change in a warming climate.
How to cite: Chae, Y., Seo, K.-W., and Nam, S.: A strengthening dipole pattern in Arctic Ocean dynamics observed by GRACE/GRACE-FO, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6365, https://doi.org/10.5194/egusphere-egu26-6365, 2026.
Rapid Arctic change is altering not only local climate conditions but also the teleconnections linking the Arctic to the midlatitudes. In the emerging “New Arctic,” characterized by strong summer sea-ice loss, expanded first-year ice, and deeper tropospheric warming, traditional Arctic–midlatitude linkages are being reshaped in both structure and strength. This study examines how these teleconnections are evolving using a combination of satellite observations, reanalysis data, and climate-model simulations. A key background change is the expansion of newly formed winter sea ice since the mid-1990s, increasing at about 0.6 million km² per decade. This growth is driven by enhanced autumn refreezing following intensified summer melt and is spatially concentrated over the central and eastern Arctic Ocean north of Siberia. Seasonally, the increase is dominated by November ice formation, highlighting the growing importance of late-autumn processes in the New Arctic.
Under this new background, several Arctic–midlatitude teleconnections show distinct changes. First, since the late 1990s, the relationship between December Bering Sea ice extent and January Siberian cold extremes has strengthened, supported by model experiments showing enhanced ridge–trough wave propagation into Eurasia. Second, targeted simulations demonstrate that November Arctic sea ice plays a critical role in modulating troposphere–stratosphere coupling, with a markedly weaker atmospheric response under late-autumn ice-free conditions. Third, large-ensemble simulations reveal that under strong CO₂ forcing, the historically robust “warmer Arctic–colder Eurasia” linkage weakens and becomes less coherent.
These results show that teleconnections in the New Arctic are increasingly season-dependent and state-dependent, with important implications for midlatitude climate variability and predictability.
How to cite: He, S., Fan, K., Zhao, J., Xu, X., and Jiang, J.: Teleconnections in the ‘new Arctic’, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17581, https://doi.org/10.5194/egusphere-egu26-17581, 2026.
Thermohaline staircase layers have been consistently observed in the Arctic Ocean for over 50 years. Previous studies demonstrate that these structures exhibit large-scale spatial coherence. However, on time scales beyond a few years, both the coherence and evolution of the layers are unknown. Using Ice-Tethered Profiler data from 2005--2022 in the Beaufort Gyre Region, we track staircase layers across time and space with an unsupervised clustering method. Individual layers are found to be coherent across the entire 17-year time period, with properties that appear to evolve on 40--50 year timescales or longer. This establishes, for the first time, the decadal-scale coherence of thermohaline staircases in the Arctic Ocean. Moreover, we find that the observed changes are not consistent with the staircase being in a state of equilibrium, but rather support the hypothesis that it is decaying slowly from an initial or on-going perturbation.
How to cite: Rosenblum, E., Schee, M., Lilly, J., and Grisouard, N.: Decadal coherence of Arctic thermohaline staircases, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22061, https://doi.org/10.5194/egusphere-egu26-22061, 2026.
Since the previous Japanese Arctic projects (ArCS and ArCS II projects), we have accumulated and evaluated scientific data, providing knowledge to the Joint Program for Scientific Research and Monitoring (JPSRM) established under the Central Arctic Ocean Fisheries Agreement (CAOFA). This knowledge could form the basis for conserving and utilizing marine resources. Here, contributions of the Japanese Arctic studies to the CAOFA JPSRM Implementation Plan are presented. During the 2020 R/V Mirai cruise in collaboration with the Synoptic Arctic Survey (SAS), unusually low oxygen and acidified water was found on the Chukchi Borderland (CBL), a high-seas fishable area of the Pacific Arctic. The integrated SAS data suggested that Beaufort Gyre shrinkage and Atlantification triggered a frontal northward flow along the CBL that transported the low oxygen and acidified water from the shelf-slope north of the East Siberian Sea. Therefore, the CBL area should be monitored as a bellwether of ecosystem degradation caused by ocean acidification and deoxygenation in the Central Arctic Ocean. This finding was cited in the CAOFA JPSRM Implementation Plan, and is proposing a most urgent monitoring site, which is at risk of ocean acidification and deoxygenation, in the Agreement Area. Future contributions to the CAOFA JPSRM are expected through the scientific surveys that will be conducted by the Japanese new icebreaker, Arctic Research Vessel (ARV) Mirai II.
How to cite: Nishino, S.: Japanese Arctic projects’ contributions to the Central Arctic Ocean Fisheries Agreement, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2619, https://doi.org/10.5194/egusphere-egu26-2619, 2026.
The Arctic Ocean experienced severe acidification in the subsurface layer owing to the increased invasion of Pacific Winter Water. However, the recent development and its control mechanisms remain unclear. Here we show that the subsurface acidifying waters (aragnite undersaturation) have further expanded northward, while it has been significantly thinned and shallowed in the western Canada Basin since 2015, in contrast to the thickening and deepening of the acidifying waters during 1994-2015. In the Northern Canada Basin, the more acidic waters in subsurface were also expanded substantially, which is mainly enhanced by the local enhancement of primary production in surface layer due to rapid sea ice loss.
How to cite: Li, C.: The impact of climate change on Arctic acidification, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2981, https://doi.org/10.5194/egusphere-egu26-2981, 2026.
The presence of sea ice at the coast prevents coastal erosion of permafrost in the Arctic most of the year. Decreasing sea ice due to climate change will extend the erosion season. We examine coastal ice presence in a single model large ensemble future projection under the SSP3.70 scenario. We compare sea ice presence against locations with favourable geological conditions for erosion. The Arctic Ocean circulation pattern determines whether nutrients from erosion will be retained in the Arctic or end up the North Atlantic. Both sea ice and circulation conditions depend on the large scale atmospheric pattern, therefore we examine the correlation between high erosion conditions and enhanced outflow conditions. The contributions of Rynders and Aksenov were supported by the National Capability Multicentre Round 2 funding from the Natural Environment Research Council (BIOPOLE grant no. NE/W004933/1 and CANARI grant no. NE/W004984/1).
How to cite: Rynders, S. and Aksenov, Y.: Potential for future erosion in the Arctic in the CANARI HadGEM3 large ensemble, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3566, https://doi.org/10.5194/egusphere-egu26-3566, 2026.
With much focus on the local and regional changes in the ocean and marine biogeochemistry, high-resolution ocean-sea ice models became a widely desired tool for ocean research.
We present analysis of the analysis of the kilometric scale resolution regional ocean model for the Arctic and North Atlantic developed at the National Oceanography Centre and aimed at resolving mesoscale circulation. The model ARC36 features NEMO ocean model coupled to the SI3 sea ice model [1].
To assess model performance and demonstrate its applicability to the regional assessments, the two case studies has been chosen: (1) the Western Fram Strait and the East Greenland Shelf and (2) the Svalbard. For these areas eddy dynamics has been analysed and compared to the mooring data and satellite imagery. We have also assessed exchanges between the fjords, the shelf and the open ocean. The simulations are evident of fine structure in ocean currents and eddies, more detailed than in coarser resolution models. The model also simulates sea ice break-up at spatial scales from a few kilometres to several hundreds of kilometres, suggesting the usability of continuum sea ice models at high-resolution.
This work is funded by the Natural Environment Research Council (NERC) LTS-M Programmes CANARI (NE/W004984/1) and BIOPOLE (NE/W004933/1), by UKRI/NERC HighLight Topic Projects “Interacting ice Sheet and Ocean Tipping – Indicators, Processes, Impacts and Challenges (ISOTIPIC)”, by the grant NE/Y503320/1, and by the Met Office Advancing Arctic meteorological and oceanographic capabilities & services project, which is supported by the Department for Science, Innovation & Technology (DSIT), and uses the ARCHER2 UK National Supercomputing Service (https://www.archer2.ac.uk).
References
[1] Rynders, S., Aksenov, Y., Coward, A., and Harle, J.: First look at Arctic eddies in a kilometric NEMO5 simulation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7121, https://doi.org/10.5194/egusphere-egu25-7121, 2025.
How to cite: Aksenov, Y., Rynders, S., de Steur, L., James, H., Barton, B., Coward, A., Polton, J., and Blockley, E.: Ultra-high-resolution ocean-sea ice model: a new capability to simulate shelf-ocean processes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7957, https://doi.org/10.5194/egusphere-egu26-7957, 2026.
Mesoscale eddies are widespread in the Arctic Ocean affecting circulation, stratification, the transport of heat and salt, and consequently sea ice melt. We detect and track coherent eddies in a 1-km resolution Arctic Ocean simulation using the unstructured-mesh Finite volumE Sea ice-Ocean Model (FESOM2). Their spatial and seasonal distributions are analyzed, and quasi-3D eddy composites are used to quantify their influence on the water column, surface heat fluxes, and sea ice.
Eddy formation is highest along topographic features and the boundary current, with eddy sizes roughly corresponding to the local Rossby radius. Anticyclonic eddies are larger and more energetic than cyclonic eddies and can lift warm, saline Atlantic Water toward the surface, which increases the vertical heat flux and can cause localized basal sea ice melt. Cyclonic eddies, by contrast, mainly transport cold surface water downward and have little impact on the surface heat budget or sea ice. Edd-induced anomalies are strongest in Fram Strait, weaken downstream, and are larger beneath pack ice than in the marginal ice zone. These results are consistent with an eddy-ice pumping mechanism, where ocean-sea ice stress enhances vertical transport and contributes to eddy decay. Overall, the analysis shows that mesoscale eddies play an important role in the vertical exchange of heat in the Eurasian Arctic making them an important factor in the ongoing Atlantification of the Arctic Ocean. Since the role of eddies is expected to become even more important in the future, adequately representing them in model simulations will be necessary, despite the high resolution and computational cost required to resolve them.
How to cite: Müller, V., Danilov, S., Jung, T., Koldunov, N., and Wang, Q.: Properties and Effects of Mesoscale Eddies in the Eurasian Basin of the Arctic from a Model Simulation at 1-km Resolution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7485, https://doi.org/10.5194/egusphere-egu26-7485, 2026.
The generation of internal wave generation might increase in the warming Arctic, especially at the sea surface, where wind power input into the upper ocean is substantially stronger as sea ice disappears. More internal wave energy implies stronger mixing that might lead to larger upward heat fluxes from the warm Atlantic Water, contributing to the ongoing sea-ice melt. To comprehensively test this hypothesis, a physics-based mixing parameterization building on an internal wave model that accounts for internal wave generation, propagation, and breaking, is required. To develop such a model, however, knowledge of the internal wave spectral characteristics and their spatio-temporal variability is indispensable. This study therefore investigates the vertical wavenumber spectra of internal wave energy and how their shape varies across the Arctic Ocean based on finescale hydrographic profiles collected by a variety of instrument platforms. It focuses on internal wave energy levels, vertical wavenumber spectral slope and bandwidth, and wave-driven mixing to elucidate their geographic and temporal variation and shed light on the environmental factors determining their variability.
How to cite: Pollmann, F.: Internal wave spectra and mixing in the warming Arctic, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9495, https://doi.org/10.5194/egusphere-egu26-9495, 2026.
The Arctic system is transitioning into a new regime whose properties are yet to be determined, as several feedback processes are undergoing unprecedented changes. Accelerated loss of sea ice and glaciers, enhanced discharge from major pan‑Arctic rivers, widespread permafrost degradation, and a strengthening of the global hydrological cycle are collectively reshaping the upper ocean, making it warmer and increasingly fresh. Sea Surface Salinity (SSS), recognized as an Essential Ocean Variable, provides an integrated measure of atmosphere-ice-ocean coupling. This work investigates the spatial and temporal patterns of SSS and their short-term evolution across nine pan-Arctic regions of the over the satellite period 2011–2022, with a particular focus on how these changes relate to key drivers of surface freshening. To achieve this, we use three Arctic-dedicated satellite products –two from ESA’s Soil Moisture and Ocean Salinity (SMOS) mission, developed by the Barcelona Expert Centre (BEC) and the Laboratory of Ocean and Climatology Expertise Center (LOCEAN), along with the Climate Change Initiative Salinity (CCI) dataset– and GLORYS12v1 model reanalysis. The consistent agreement between satellite observations and model outputs in September –when Arctic coverage is at its annual maximum (r > 0.54) –highlights recent advances in salinity retrievals and their ability to capture key oceanographic processes. Throughout this month, the spatial SSS trend revealed a statistically significant freshening in the northern Barents Sea, with particularly low anomalies in 2019 and 2022. On the other hand, a basin‑wide freshening is evident in all regions except the Kara Sea, with the largest declines (~0.2 yr⁻¹) found near major Arctic river mouths, where a concurrent SST increase further highlights the influence of continental freshwater inputs. The seasonal analysis over the year‑round ice‑free regions (Nordic and Barents Seas) revealed pronounced winter discrepancies among all products –including against in situ data– and most notably in the Norwegian Sea, showing that the drivers of these differences are not yet fully understood. A significant summer freshening emerged along southeastern Greenland, largely shaped by the pronounced anomalies of 2017 and 2021. These shifts reflect the combined influence of variability in sea‑ice export, the timing of melt onset, and atmospheric circulation patterns that govern the delivery and redistribution of freshwater. Meanwhile, the highest summer SSS anomaly in the Barents Sea occurred near the ice edge in 2015, following a winter with exceptionally large sea‑ice volume anomalies. The northward winter transport of sea ice (> 0.18 km³ month⁻¹), enhanced by a positive Arctic Oscillation phase, displaced the ice edge northward, leaving the meltwater signature above 77.5º N. These results highlight the crucial role of remotely sensed SSS in providing insights into the Arctic Ocean's changing conditions and their global implications.
How to cite: Sánchez-Urrea, M., Umbert, M., Galí, M., McPherson, R., De Andrés, E., and Gabarró, C.: A Decade of Arctic SSS Variability from Satellite and Reanalysis Data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17370, https://doi.org/10.5194/egusphere-egu26-17370, 2026.
Internal waves are a key driver of diapycnal mixing in the global ocean and play an essential role in setting the large-scale overturning circulation. In the Arctic Ocean, however, internal-wave-driven mixing is assumed to be weak due to strong stratification and the presence of sea ice, which limits wind forcing and surface wave activity. The scenario of ongoing sea-ice decline raises the possibility of enhanced internal wave activity and associated mixing, potentially increasing upward oceanic heat fluxes and further accelerating ice loss.
In this study, we investigate the role of tidal forcing as a source of internal waves in the Arctic Ocean using the ocean model FESOM. We perform simulations with tidal forcing at unprecedented horizontal resolution (around 1 km). The simulations are conducted for different seasons and sea-ice conditions to examine how variations in sea-ice modulate tidal currents and internal wave generation. By comparing simulations with and without tidal forcing, we assess the impact of tides on sea-ice dynamics, providing initial insight into coupling between tides, internal waves, and sea ice in the Arctic Ocean. The diagnosed internal tide generation will serve to force the internal wave model IDEMIX, which we will couple to FESOM to provide a consistent mixing parameterization for the simulation of the warming Arctic.
How to cite: Bagaeva, E., Pollmann, F., Wang, Q., Scholz, P., and Danilov, S.: Tidal Forcing and Internal Wave Generation in the Arctic Ocean: High-Resolution FESOM Simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17796, https://doi.org/10.5194/egusphere-egu26-17796, 2026.
The Arctic, spanning over eight sovereign countries and the Arctic Ocean, is warming three tofour times faster than the global average, driving profound transformations of the cryosphereand ocean systems. It harbours four critical climate tipping points: the accelerated melt of theGreenland Ice Sheet, the thawing of boreal permafrost, the collapse of winter Arctic sea ice,and the weakening of the Labrador–Irminger Seas convection. These processes are tightlyinterconnected and play a key role in regulating the global climate, yet their combined impactsremain insufficiently constrained by observations.Within this context, the CASCADES Expedition is an international and interdisciplinary polarprogramme designed to investigate the coupled interactions between glaciers, sea ice, and theocean around Baffin Bay and Northwest Greenland. CASCADES is coordinated by the InstitutNordique du Québec, the Swiss Polar Institute, and the French Polar Institute, in collaborationwith Greenlandic institutions. It brings together more than 50 Canadian, French, Greenlandic,and Swiss researchers around 16 scientific projects from 13 research institutions.CASCADES will be conducted aboard the Canadian research icebreaker CCGS Amundsen andis structured into two complementary legs in 2026, aligned with critical seasonal phases of theArctic system. A first leg during the summer targets peak glacier melt and freshwater input,while a second leg during autumn focuses on the transition toward sea-ice freeze-up. This dual-season strategy enables the investigation of how physical, chemical, and biological processesevolve from melt to freeze-up, and how these transitions affect carbon cycling, productivity,and ecosystem structure.By providing coordinated, multidisciplinary observations across key Arctic seasons,CASCADES aims to improve understanding of cryosphere–ocean–ecosystem coupling and itsimplications for the North Atlantic and the global climate system. Beyond its core scientificobjectives, the expedition serves as a platform for international collaboration, sciencediplomacy, education, and engagement with Arctic communities, contributing to sharedobservation efforts and to the anticipation of climate-driven changes in polar oceans and beyond.
How to cite: Ruols, B., Tremblay, J.-É., Jaccard, S., and Dumont, D.: The CASCADES Expedition: multidisciplinary observations of a rapidly changing Arctic, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22970, https://doi.org/10.5194/egusphere-egu26-22970, 2026.
