Norwegian Polar Institute

Warming on Svalbard is occurring up to seven times faster than the global average and is driving widespread glacier retreat. In addition to rising air temperatures, light absorbing particles (LAP; including black carbon and mineral dust) can enhance snow and ice melt by reducing surface albedo. While black carbon has been studied extensively on Svalbard, mineral dust remains relatively understudied despite growing evidence that high latitude dust emissions may increase due to decreases in snow cover and glaciers retreat.To address this knowledge gap, we analyzed mineral dust and black carbon in seasonal snow and firn cores collected from twelve spatially distributed Svalbard glaciers between 2022 and 2026. Dust concentrations and deposition rates were quantified using gravimetric filtration and ICP-MS, while dust mineral composition was characterized using X-ray diffraction and scanning electron microscopy with energy-dispersive spectroscopy. Black carbon was measured on select firn samples using a Single Particle Soot Photometer.Results show pronounced seasonal variability, with low winter dust concentrations and enhanced summer–fall deposition, as well as substantial spatial variability in dust concentration, mineralogy, and spectral reflectance. Winter dust concentrations ranged from 0.3 to 17.6 µg g⁻¹ (median 0.9 µg g⁻¹), with deposition rates between 0.1 and 1.5 g m⁻² (median 0.4 g m⁻²). Mineralogical analyses reveal abundant sheet silicates and common rock-forming minerals across all sites, with carbonates largely restricted to central Svalbard glaciers, indicating variability in dust sources and depositional processes. Radiative transfer modeling demonstrates that mineral dust dominates LAP driven albedo reductions, exceeding contributions from black carbon. These findings highlight the growing importance of mineral dust for Svalbard snow and ice melt in the warming Arctic.

MOSAiC expedition in 2019/2020 collected an unprecedented volume of sea ice and snow data. For example, over 50 autonomous drifters, more than 160 km of sea ice thickness transect lines, nearly 250 snow pits, hundreds of satellite images, and thousands of ship radar images. Studies based on these data have yielded, among others, new data-based estimates of snow thermal conductivity, discovered new freezing mechanisms in the ridges and pinned the limits of sea ice deformation scale invariance. MOSAiC data analyses show that the snow depth and ice thickness was largely ice-age independent and that most of the winter’s snow was trapped in the deformed ice and that the loss of snow to leads was small.Numerous sea ice deformation events formed the rough topography that trapped the snow throughout the winter. In order to better understand these processes and interactions, drifter, satellite remote sensing, and ship radar data can be used to analyse the deformation processes themselves, including reactivation of the leads and pressure ridges. These dynamics can not be represented in continuum models due to the spatial scale discrepancy. Here we will present how the sea ice deformation data from remote sensing can be used to create ice topography to constrain the snow distribution processes and, with it, the ice growth. We will use the recently developed methodology of data-model fusion by Itkin and Liston (2025, The Cryophere) to quantify the local snow-ice processes on spatial extents relevant also to the continuum models.

While most of the below 700ka section of the Beyond EPICA ice core has been measured for water isotopic composition in 2.5 cm samples, a sub-section (depth 2473-2475 meters) has been cut into 1.25 cm. These ultra-high-resolution samples have been measured side-by-side with the 2.5 cm samples from the same depth, allowing a direct comparison with minimal calibration or instrument drift-induced uncertainty. With great care for optimal measurement quality, we present here a comparison of the samples, with average precisions (+/- 1 STD) of 0.03 o/oo and 0.07 o/oo for ẟ18O and ẟ2H, respectively, and average accuracies of 0.03 o/oo and 0.4 o/oo for ẟ18O and ẟ2H, respectively.Variations between the 1.25 cm and 2.5 cm samples that cannot be attributed to measurement uncertainty are observed. Our ultra-high-resolution measurements provide critical insights into intra-core variability, and we argue that ice cores, when possible, should be measured at the highest resolution to obtain optimal information about past climate variability.

Sea-ice ridges (or more precisely, deformed ice) constitute a large fraction of the Arctic ice pack, however, estimates range broadly from 30 to 70%. Yet, we know disproportionally little about their role in the Arctic sea-ice system, a system that is in rapid change. In situ studies of ridges are logistically challenging, and as a result, most research has focused on level sea ice, despite the significant proportion of sea ice residing in ridges.Ridges evolve over time and provide an environment for ice growth very different than the typical level ice. Observations during the year-long MOSAiC drift expedition revealed several processes that could contribute to ice growth, even in summer, when most of the ice pack is melting. Indirectly ridges also affect, for example, melt pond formation, and also under-ice spreading of meltwater (under-ice ponds), that in turn affect the melt rates of level ice. However, these indirect effects of ridges have virtually never been quantified.Rare observations from the MOSAiC expedition explored the unique habitats within sea-ice ridges, including surfaces of ice blocks in association with water-filled voids, showed distinct differences in biological properties compared to level ice bottom and pelagic biota. These ridge-specific habitats had unique protist and bacterial assemblages contributing to the high diversity and richness found in Arctic sea ice. In summer, ridges can be hotspots of protist biomass and can contain the majority (up to 80%) of sea ice algal biomass - an element not yet considered in Arctic assessments of sea-ice biomass.We argue that sea-ice ridges should be included in assessments of Arctic Ocean biodiversity and biogeochemistry to fully understand the Arctic sea-ice ecosystem and its response to ongoing changes. Future efforts should not only investigate the complex physical and biological processes within sea-ice ridges but also integrate these processes into models. Only then can we predict how the changes in the Arctic icescape will affect atmosphere-ice-ocean-ecosystem interactions and how the ongoing changes of the ice pack will affect ridging in the future.

ABSTRACT Climate change associated transformations of Arctic marine ecosystems are having detrimental impacts on Arctic endemic marine mammals. However, warming conditions are providing new habitats for temperate marine mammals, some of which are expanding into Arctic regions, posing a threat of novel pathogen introduction and disease transmission. We analyzed swab samples for Influenza A, morbilli‐ (Phocine distemper virus, PDV), and herpesvirus nucleic acid and performed microbiological screenings and serological analyses for antibodies for the same viral pathogens, the bacterial agents Brucella spp. and Leptospira spp. and the protozoan parasite Toxoplasma ( T .) gondii from ringed ( Pusa hispida ), bearded ( Erignathus barbatus ), and the newly established harbor seals ( Phoca vitulina ) in Kongsfjorden, Svalbard. Antibodies against Phocine Herpesvirus‐1 or antigenetically related phocine herpesviruses (PhHV) were detected in all species. Antibodies against Influenza A were only found in one ringed seal and antibodies against PDV were found in two harbor seals. Twelve harbor seals and two ringed seals tested positive for Herpesvirus DNA by PCR. Brucella spp. and Leptospira spp. antibodies were detected in multiple harbor seals and a single bearded seal. Three harbor, two ringed, and one bearded seal had antibodies against T. gondii . Our results indicate an overlap and possible transmission of pathogens between all investigated seal species. The introduction of new pathogens to the Arctic through temperate species' range expansions could have fatal consequences for immunologically naive Arctic seal populations and should be further investigated.

Abstract. The increasing release of Antarctic meltwater represents one of the most profound, yet uncertain, consequences of global climate change. The absence of interactive ice sheets in state-of-the-art climate models prevents the direct calculation of ice–ocean feedbacks, leaving significant uncertainty in the global and regional consequences of meltwater discharge. This study leverages results from the Southern Ocean Freshwater Input from Antarctica (SOFIA) initiative to assess the ocean response to a 0.1 Sv meltwater perturbation and infer the feedback on ice shelf basal melting across 10 CMIP6 models. We analyze meltwater-induced temperature anomalies across distinct continental shelf regimes and compare them with SSP5-8.5 warming-induced anomalies. We then translate these anomalies into basal melt rates using a parameterization calibrated with a new observational climatology, which reveals strongly regional melt sensitivities that cannot be captured with an Antarctic-wide coefficient. Although the meltwater feedback is generally thought to amplify basal melting, our results demonstrate large regional differences, with implied enhanced ice shelf mass loss in some sectors but suppressed basal melting in others. The model ensemble indicates a warming feedback on the continental shelf in most East Antarctic regions, whereas in West Antarctica, most models simulate either cooling or reduced warming, suggesting a negative feedback. This regional contrast implies that East Antarctica may play an increasingly dominant role in future ice shelf mass loss. Simulations support existing hypotheses linking these asymmetric temperature responses to strong regional connectivity and shelf-break dynamics, including a strengthened Antarctic Slope Front, an accelerated Antarctic Slope Current, and reduced dense shelf water formation.

Polar bears are only found in Arctic areas with sufficient access to sea ice and seals on which they prey. Studies have highlighted negative effects on condition and demographics in areas where sea ice cover is declining due to warmer climate, but condition of the Barents Sea polar bear population have not been examined yet. Loss of sea ice rate has been considerably higher here than in other areas with polar bears. We investigated variation in body condition index (BCI) among 770 adult bears, 1188 captures, in March-May 1995-2019, in Svalbard, Norway (western part of the Barents Sea). We assessed how intrinsic (female reproductive state, age) and both males and females, BCI declined until 2000, but increased afterwards, during a period with rapid loss of sea ice. In models including sea ice metrics and climate (Arctic Oscillation), there was no support for the predicted negative effect of warmer weather and habitat loss. This indicates a complex relationship between habitat, ecosystem structure, energy intake, and energy expenditure. Increases in some prey species, including harbour seals, reindeer, and walrus, may partly offset reduced access to seals. Our findings underline the importance not to extrapolate findings across populations.

Abstract. The thickness and consolidation state of pressure ridges are variables relevant for sea ice mass balance, melt processes and ecosystem habitat. We show how both variables can be detected by the multi-frequency electromagnetic induction (EMI) sounding, based on data collected during Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) in the central Arctic Ocean between November 2019 and July 2020. We validate the EMI results by collocating them to sea ice topography from the airborne laser scanner, underwater topography from multi-beam sonar, and sea ice thickness and structure from drill holes. Selected channels of low frequency give good estimates of total thickness, while selected channels of high frequency give good estimates of consolidated layer thickness. The MOSAiC EMI dataset was collected over a large number of ridge systems formed between freeze-up and break-up. Nine individual ridge transects can be used to track the seasonal development. The footprint size and sensitivity of the method make the EMI sounding appropriate for the detection of ridges with up to 10 m total thickness. Where available, the ridge structure data from other methods are consistent with our results. The superior temporal and spatial coverage of the MOSAiC EMI data permits further analysis that indicates a slow reduction of the total thickness towards the consolidated layer thickness. Interestingly, the consolidated layer thickness exceeds the level ice thickness by a factor of 1.6 to 2 and also shows, at least for individual ridges, a seasonal decrease. This may be a feature of the thin snow cover at MOSAiC. Multi-frequency EMI is a promising method for non-intrusive pressure ridge surveying with a large potential for pressure ridge dataset extension.

Sea-ice algae account for a substantial part of annual primary production in ice-covered waters and are an important component of the Arctic marine food web. With climate-induced changes to snow and sea-ice cover and their impact on the surface ocean, such as earlier melt, thinner ice, and increased upper-ocean stratification, a shift toward earlier and more extensive nutrient limitation on ice algal growth can be expected. Therefore, increasing our understanding of the processes governing nutrient supply and uptake by sea-ice algae is essential. Here, we compiled a pan-Arctic dataset of concentrations of sea-ice and sub-ice nutrients and sea-ice chlorophyll a (chl a) to assess their regional and seasonal variability, as well as the relationship of sea-ice algae and nutrient dynamics in the Arctic Ocean. This dataset indicates that bottom sea-ice nutrient and chl a concentrations were highest in the central Canadian Arctic Archipelago (Resolute Passage) due to tidal-driven mixing at the ocean-ice interface, and lowest in the Arctic Ocean basins. At the regional scale, Pacific and Atlantic Water influence variability in sea-ice and sub-ice nutrient concentrations. Significant positive relationships of bottom sea-ice nutrient versus chl a concentrations were ubiquitous across the Arctic during the ice algal bloom, suggesting intracellular nutrient storage as an important mechanism to support ice algal growth. This relationship in turn alters nutrient ratios within the sea ice relative to sub-ice waters, decreasing NOx:PO4 ratios, while increasing NOx:Si(OH)4 ratios. In contrast, bottom sea-ice nutrient-chl a relationships were less common and sometimes negative when nutrient concentrations were low, likely reflecting nutrient limitation. In conclusion, we have demonstrated a pan-Arctic, yet regionally specific, influence of the ice algal community on bottom sea-ice nutrient concentrations.