29 March 2026 | 10:00 - 11:45 CEST / UTC+2
Open Session - HYBRID
Room: Jeppe Vontilius Auditorium
Session Description:
This session examines physical, chemical and biological change in Arctic marine and coastal systems. It focuses on circulation, freshwater and biogeochemical fluxes, ecosystem dynamics and links to sea ice and glaciers, including implications for climate feedbacks and living resources.
Keynote: Prof. Søren Rysgaard
Oral presentations:
Name: Atreya Basu (University of Manitoba)
Title of presentation: Evidence of shifting freshwater regime in Hudson Bay
Abstract text: Hudson Bay, located at the southern margin of the Arctic Ocean, receives 0.98 m of river runoff annually, over three times the Arctic Ocean average, and stores a comparable sea-ice volume. Freshwater thus governs HB’s physical and biogeochemical regimes and, after export through the Hudson Strait, influences Labrador Current and North Atlantic circulation. Yet, limited ship-based observations obscure how river water (RW) and sea-ice melt (SIM) contributions have shifted over space and time. This study integrates satellite observations with ship-based measurements to distinguish and map RW and SIM contributions across HB. Because both are fresh, salinity alone cannot separate them. RW is enriched in chromophoric dissolved organic matter (CDOM), whereas SIM contains almost none, allowing their differentiation in surface waters using satellite-derived CDOM and salinity. In deeper layers, oxygen-isotope ratios combined with salinity from discrete samples were used to trace freshwater sources. Results show that RW, driven by river discharge, dominates early-summer freshwater composition in Hudson Bay. By late summer, SIM becomes the primary contributor of salinity-driven density stratification that was previously RW-controlled. In fall, RW intensifies again along the coast as cyclonic winds subduct RW into deeper layers, despite declining river discharge, while offshore regions experience wind-driven upwelling that generates a shallow, salty halocline. In contrast, during early summer, anticyclonic winds promote offshore RW convergence, deepening the halocline. This wind-driven freshwater redistribution in Hudson Bay is analogous to the Beaufort High/Low systems observed in the western Arctic Ocean. Over 2011–2019, RW fractions increased (0.0048 yr⁻¹) and SIM declined (–0.003 yr⁻¹), reflecting enhanced runoff and reduced ice melt, providing evidence of a shifting freshwater regime in Hudson Bay within a changing Arctic system.
Name: Sara De Clerck (Faroe Marine Research Institute)
Title of presentation: Ecological divergence in habitat use of long-finned pilot whales (Globicephala melas) across the North Atlantic
Abstract text: Long-finned pilot whales (Globicephala melas) are widely distributed across the North Atlantic, occurring in subpolar and temperate waters and generally found in deep oceanic areas. Their distribution, however, varies seasonally and interannually, with occasional ventures onto the continental shelf. The variability in movements has been linked to changes in prey distribution and abundance. Despite their ecological importance, knowledge of population structure and connectivity—critical information since pilot whales are hunted in both Greenland and the Faroe Islands—remains limited. Between 2023 and 2025, we deployed satellite-transmitters on pilot whales in the Faroe Islands (n = 11), East Greenland (n = 6) and Iceland (n = 2) to assess population connectivity and regional differences across the North Atlantic. Movement metrics and habitat characteristics were compared among the three locations, with comparative tests between the Faroe Islands and East Greenland. Pilot whales tagged in the Faroe Islands occupied a broad range of habitats and exhibited large-scale movements both northwards and southwards, with a maximum displacement of up to 1724 km from the tagging location. They predominantly used deep offshore waters (>1000 m) more than 150 km from the coast. In contrast, whales tagged in East Greenland and Iceland remained largely in shallower continental shelf waters (<500 m), at median distances of 72 km and 65 km from the coast, respectively. Significant regional differences were found for maximum displacement, bathymetry, and distance to coast, indicating consistent divergence in horizontal habitat use between whales tagged in the Faroe Islands and those in East Greenland. Our findings suggest the existence of regionally specialised groups of potentially distinct ecotypes within a genetically connected North Atlantic population. This study provides novel insights into the population structure and connectivity, with implications for the management and conservation of North Atlantic pilot whales.
Name: Coraline Leseurre (Flanders Marine Institute)
Title of presentation: Svalbard seawaters as a significant source of CH4 to the atmosphere during summer 2024
Abstract text: Methane (CH4) is the second most important anthropogenic greenhouse gas after carbon dioxide (CO2), with a global warming potential ~30 times higher. While open-ocean CH4 is usually close to atmospheric equilibrium (~2% of the global CH4 budget), emerging evidence suggests that shallow coastal regions may have a significant impact on the marine contribution, particularly in the Arctic shelf areas where the effects of climate change are amplified (e.g. Arctic amplification). To better constrain the processes controlling CH4 air-sea exchange in these regions, we investigated the sea surface CH4 concentrations around Svalbard Archipelago (a moderately shallow shelf affected by glacial runoff and complex geology) during a summer cruise conducted on board the RV Skagerak (University of Gothenburg, Sweden) in August 2024. We observed systematically elevated CH4 concentrations (mean 11 nmol L-1) with clear spatial patterns linked to bathymetry and known hydrocarbon seep locations. The highest values (up to 105 nmol L-1) occurred near marine-terminating glaciers in the Storfjorden and were not associated with strong salinity anomalies. This indicates that subglacial inputs from the glacier bedrock may dominate over the simple freshwater dilution from the glacial meltwater plume.Using these observations, we demonstrate that Svalbard’s surface waters acted as a pronounced source of CH4 to the atmosphere during summer 2024. We will discuss the relative roles of geological seepage and subglacial pathways (especially in the context of the transition from marine to land-terminating glaciers) and their implications for present and future Arctic shelf CH4 emissions.
Name: Luisa Düsedau (Aarhus University)
Title of presentation: Fingerprinting and quantifying seaweed DNA in Arctic sediments
Abstract text: Arctic seaweeds create valuable marine habitats which exhibit a considerable primary productivity and thereby CO2 binding capacity. In particular, marine forests created by canopy-forming brown macroalgae dominate along the polar rocky coasts. Our research goal is to improve our understanding of how much of the seaweed carbon is exported from the coast and potentially sequestered as “Blue Carbon”. Export pathways include carbon sinks in fjord sediments and beyond the fjords in continental shelf sediments or the deep sea. The advent of molecular techniques provides novel and powerful tools to perform, for the first time, absolute quantification of seaweed DNA in environmental samples. Through targeted identification using droplet digital PCR (ddPCR), we successfully traced and identified the DNA of six biomass-dominant seaweed species in sediment cores collected from Greenland and the Faroe Islands. Three layers of sediment cores from Arctic fjords and continental shelves were examined from the surface to a depth of 10 cm using ddPCR in combination with analyses of carbon and its stable isotopes. Overall, our results indicate higher quantities of total seaweed DNA in fjord sediments compared to continental shelf sediments. Laminaria hyperborea DNA dominated the total seaweed DNA of Faroe Islands sediments, while in Greenland sediments it was Agarum clathratum and Saccharina latissima DNA. We share first insights on seaweed DNA signatures in combination with carbon analyses of these Arctic sediments and discuss potentials and limitations for quantifying these seaweed fingerprints. Our findings provide valuable field evidence underpinning overall assessments of the importance of seaweeds for carbon retention in Arctic sediments.
Name: Andreas Kjær Dideriksen (Arctic Research Centre, Department of Biology, Aarhus University)
Title of presentation: Plumes, Calving and Chaos - When a glacier throws a temper tantrum
Abstract text: With the increasing atmospheric warming in the Arctic region, the melting of the Greenland Ice Sheet is accelerating. This impacts both local and global processes from fjord circulation and calving dynamics to sea level rise and freshening of the ocean. The complex interactions between marine-terminating glaciers and fjord systems are therefore a crucial link for interpreting how climate change influences both fjord environments and regional oceanography. Yet, direct observations focusing on processes such as glacier calvings and subglacial discharge plumes and their associated impacts on the hydrographic conditions in fjord systems remain limited due to remoteness, unpredictability, and hazardous environmental conditions. In this study we combine remote sensing, in situ data, and numerical simulations of a large calving event along with observations of a subglacial discharge plume at the marine-terminating Hisinger Glacier in Dickson Fjord, NE-Greenland. This study provides a rare set of oceanographic observations pre-, syn-, and post-calving, which presents a unique opportunity to observe how episodic glacier events influence fjord dynamics. As the Hisinger Glacier is located in a shallow and cold part of Dickson Fjord, its location provides a natural setting to study the isolated effects of atmospheric warming on glacier–fjord interactions, since the glacier front interacts only with surface water and polar water. Our results show that glacier calving primarily drove mixing in the inner fjord near the glacier terminus. The subglacial discharge plume entrained cold polar water toward the surface, highlighting the contrasting impacts of these events in fjord systems. Further comparison with numerical simulations shows that calving-generated vortices propagate into the fjord, where deeper bathymetry near the glacier allows entrainment of underlying modified Atlantic Water into the upper fjord.