Session chairs:
Mats Granskog (Norwegian Polar Institute, Norway), Igor Polyakov (University of Alaska, Fairbanks, USA), Christine Gawinski (UiT The Arctic University of Norway, Norway)
Session content:
The central Arctic Ocean is experiencing rapid changes, primarily exemplified by the reduction in sea ice, which is caused by atmospheric and oceanic changes and accelerated by feedback processes. A prominent example of change is the borealization of the Arctic, affecting water column stability which is a key aspect of the functioning of the whole Arctic marine system. The ongoing changes have largely unknown consequences on polar marine biogeochemistry and ecosystem functioning in the deep Arctic basins. The lack of observations in this difficult-to-access region in part hampers a comprehensive assessment of the changes that have already occurred in the system, but also limits future predictability.
This session presents work focusing on the physical, biogeochemical, and ecological changes that have occurred in the central Arctic in recent decades.
Session chairs:
Paul Renaud (Akvaplan-niva, Norway), Zou Zou Kuzyk (University of Manitoba, Canada), Jakob Dörr (University of Bergen, Norway)
Session content:
Whereas many of the climate drivers of ecosystem change are shared across the Arctic, their ecosystem impacts are modulated by regional and local characteristics. Interior and outflow shelves differ from the Nansen Legacy study area, the northern Barents Sea, in their geomorphology, water mass characteristics, links with terrestrial and fresh-water systems, biotic communities, and how they are utilized by Arctic peoples. We aim to identify commonalities and differences in ecosystem response to climate change and other human impacts from the atmospheric, oceanic, geochemical, and ecological fields as well as the effect of climate changes on humans in Arctic coastal communities. Paleoceanographic studies and model projections will expand the temporal aspects of our studies, and insights gained can improve observational strategies in these regions of the Arctic. This session also contributes to exploring the linkages across domains such that we can better integrate our regional understanding within a context of pan-Arctic change.
Session chairs:
Randi B. Ingvaldsen (Institute of Marine Research, Norway), Jackie Grebmeier (University of Maryland, USA), Snorre Flo (UNIS, Norway)
Session content:
The central Arctic Ocean is tightly connected to the northern Pacific and Atlantic Oceans through advection processes that link the subarctic regions with the Arctic. In addition to heat and salt, this advection transports nutrients, organic carbon, organisms, pollutants, and metals. All of these objects can be transformed on the continental shelves as they transit into the high Arctic. The Barents and Bering/Chukchi Seas constitute the major inflow shelves. These regions are experiencing large changes such as seawater warming, northward receding Marginal Ice Zones, increased ocean acidification and borealization of the ecosystems, as well as increased human impact from fisheries, petroleum industry, tourism, and vessel traffic. The talks in session D present the latest understanding of the complex Arctic inflow systems.
Bluhm B*¹, Ramirez-Llodra E², Saeedi H³, Meyer H⁴, Brix S⁵, and the Challenger-150 Arctic Working Group
¹UiT The Arctic University of Norway, Tromsø, Norway, ²REV Ocean, Oslo, Norway, ³Senckenberg Research Institute, Frankfurt, Germany, ⁴Institute for Marine Research, Bergen, Norway, ⁵Senckenberg am Meer, German Center for Marine Biodiversity Research, Hamburg, Germany
The global ocean is by far dominated by deep-sea areas; the ocean basin seafloor receives increasing attention due to it sequestering carbon, housing minerals, and its high - yet underexplored - biodiversity. As sea ice declines and access to the previously permanently ice-covered Central Arctic Ocean (CAO) opens, an update on its underappreciated habitat and taxonomic diversity becomes urgent - before the human footprint increases further. Under the framework of the Challenger 150 initiative and other efforts, an updated synthesis of CAO habitat and taxonomic diversity was attempted. The taxon inventory of metazoan fauna in the Central Arctic Ocean and Greenland-Norwegian and Iceland Seas, based on >170,000 taxon distribution records, yielded >1800 morphologically identified species for which >500 have COI barcodes available. As in most oceans, arthropods, annelids, and mollusks were the most (documented) taxon rich eukaryote groups. Part of the increase in taxa relative to earlier syntheses is related to sampling efforts of diverse, previously neglected habitats including vents, seamounts, oceanic ridges, and continental slopes – rather than to changing climate. Although large spatial and taxonomic gaps in deep-sea benthic biodiversity remain, and insights into functioning of these deep-sea systems are sparse, we present the state of art knowledge, summarizing a decadal increase of knowledge since 2011 as baseline for the UN Ocean Decade 2021 - 2030.
Daase M*¹², Geoffroy M¹³, De La Torre P⁴, Berge J¹, Anderson P⁵, Vogedes D¹, Schartmüller B¹, Zolich A⁴, Johnsen G⁴, Cottier F⁵, Kopec T¹, Chawarski J³
¹UiT The Arctic University of Norway, Tromsø, Norway, ²The University Centre in Svalbard, Longyearbyen, Norway, ³Centre for Fisheries Ecosystems Research, Fisheries and Marine Institute of Memorial University of Newfoundland, St. John's, Canada, ⁴Norwegian University of Science and Technology (NTNU), Trondheim, Norway, ⁵Scottish Association for Marine Science, Oban, United Kingdom
The Arctic Ocean remains one of the most poorly studied ecosystems while experiencing the most dramatic changes due to global warming. Advances in our understanding of Arctic marine ecosystem function are hampered by insufficient temporal and spatial sampling resolution. For example, the distribution and occurrences of acoustic sound scattering layers (SSL), indicating aggregations of macrozooplankton and small pelagic fish, are still poorly documented in the central Arctic Ocean. Autonomous, ice-tethered drifting platforms equipped with environmental sensors can remain in the Arctic for extended periods and help to fill important gaps in our understanding of the processes at work in the epipelagic layers of the Arctic. Here we present data collected with Ice-tethered observatories (ITOs) deployed between 2019 and 2022 in the Arctic polar basin and in land-fast ice in the Canadian Arctic. The ITOs consists of an automatic weather station, a specially designed Optical Chain And Logger (OptiCAL) for mapping the under-water light climate, a Sea Ice Mass Balance buoy documenting sea ice growth, and an Acoustic Zooplankton Fish Profiler recording temporal and spatial variability in acoustic SSLs. The drifting ITOs all followed similar trajectories through the polar basin and documented the presence of epipelagic SSLs throughout the deployment, with diel and seasonal changes strongly correlating with variabilities in the underwater light regime.
Fransson A*¹², Melissa C³, Dmitry D¹, Bonnie R¹⁴
¹Norwegian Polar Institute, Tromsø, Norway, ²University Centre in Svalbard, Longyearbyen, Norway, ³Institute of Marine Research, Tromsø, Norway, ⁴Multiconsult, Tromsø, Norway
The Arctic Ocean is changing, with less sea ice, increased meltwater, and increased ocean CO2 uptake. Data from the Central Arctic Ocean in 2021 (Nansen Legacy) and the 2022 (SUDARCO) cruises show contrasting chemistry in sea ice and seawater between the deep basins, focusing on the Amundsen and Nansen Basins. The chemical characteristics is affected by different water in the two basins; the Transpolar Drift current carries freshwater and carbon from the Siberian shelves to the Amundsen Basin and the Atlantic water on the other hand carries heat, salt, and nutrients to the Nansen Basin. Exchange of inorganic carbon and nutrients in sea ice and surface water is presented and discussed in relation to decreasing sea ice and increasing meltwater. The results are put into a pan-Arctic perspective, comparison with results from the Synoptic Arctic Survey.
Droste E*¹, Nomura D², Tozawa M², Roden N³, Bakker DCE⁴, Hoppema M¹, Chamberlain EJ⁵, Fong AA¹, Hoppe CJM¹, Webb AL⁶, Schulz K⁷, Ulfsbo A⁸, Torres-Valdés S¹, Chierici M⁹, Fransson A¹⁰, Karam S⁸, Koenig Z¹⁰ ¹¹
¹Alfred Wegener Institute, Bremerhaven, Germany, ²Hokkaido University, Hakodate, Japan, ³Norwegian Institute for Water Research, Oslo, Norway, ⁴University of East Anglia, Norwich, United Kingdom, ⁵Scripps Institution of Oceanography, San Diego, USA, ⁶University of York, York, United Kingdom, ⁷University of Texas, Austin, USA, ⁸University of Gothenburg, Gothenburg, Sweden, ⁹Institute of Marine Research, Tromsø, Norway, ¹⁰Norwegian Polar Institute, Tromsø, Norway, ¹¹University of Bergen, Bergen, Norway
The frequency of storms in the Arctic Ocean are predicted to increase with climate change. Storms play an important role in the variability of the ocean surface layer’s physical and biogeochemical properties, as they cause turbulence and vertical mixing of subsurface water. Consequently, they alter the distribution and content of dissolved inorganic carbon (DIC), total alkalinity (TA), and partial pressure of CO2 (pCO2), affecting the sea-air CO2 exchange. However, due to the strong seasonal variability of processes affecting the marine carbonate system, the contribution of storms may differ throughout the year. We investigate the impact of two storms on the marine carbonate system that passed through the Central Arctic Ocean during the onset of annual freeze-up in September 2020, using water column and under-ice data acquired during the MOSAiC expedition (Multi-disciplinary drifting Observatory for the Study of Arctic Climate). The first storm caused little change in the surface layer, while the second storm caused entrainment of subsurface water, increasing the DIC (~20 umol kg^-1), TA (>20 umol kg^-1), and p CO2 (~10 uatm) underneath the sea ice. Elevated values persisted at least until the completion of the expedition one week later, indicating a pre-conditioning of the surface layer while transitioning into winter. Storms during freeze-up can therefore have long-lasting impacts on the biogeochemistry and are expected to be paired to changes in the marine ecosystem.
Salganik E*¹, Müller O², Olsen LM², Gardner J³, Lange BA¹⁴, Gradinger R³, Assmy P¹, Leu E⁵, Bratbak G², Larsen A⁶, Aberle-Malzahn N⁷, Granskog, MA¹
¹Norwegian Polar Institute, Tromsø, Norway, ²University of Bergen, Bergen, Norway, ³UiT The Arctic University of Norway, Tromsø, Norway, ⁴Norwegian Geotechnical Institute, Oslo, Norway, ⁵Akvaplan-niva, Tromsø, Norway, ⁶NORCE, Bergen, Norway, ⁷NTNU, Trondheim, Norway
Ridges compose a large fraction of the Arctic sea-ice volume but are still the least studied part of the ice pack, in part due associated methodological challenges. Our focused ridge studies during MOSAiC expedition allowed mapping of ridge physical properties, characterization of microbial communities associated with different ridge structures and biological rate measurements to assess the role of ridges for ecosystems. New insights include the significant contribution of either snow-slush or snow meltwater to rapid consolidation of ridge keels. The three-dimensional structure that provided microbial hotspots within ridges was drastically reduced through this summer consolidation. The overall more rapid melt of ridge keels compared to adjacent level ice is a significant but often overlooked contribution to the summer meltwater balance. Ridge keels affected the lateral extent of meltwater layers below the ice, and thus also exert indirect control of biologically important exchange between the ice and ocean. High ridge associated pelagic biological activity in winter could have originated from release of organic material during ridge formation, fueling winter activity. Unique vertical flux patterns and biodiversity and activity hotspots further demonstrate the unique biological signature of pressure ridges. Our focused studies provide new insights into the important role of ridges for the Arctic sea-ice system, ice mass balance and functioning of the ice-associated ecosystem.
Koenig Z*¹, Campbell K¹, Else B², Muilwijk M³
¹UiT The Arctic University of Norway, Tromsø, Norway, ²University of Calgary, Calgary, Canada, ³Norwegian Polar Institute, Tromsø, Norway
Sea ice algae are at the base of the food web in the Arctic. With ongoing climate change and a shrinking sea ice cover, their habitat is compromised, and the sea ice algae communities are changing. With a more mobile ice pack, the physics at the sea ice – ocean interface is modified, influencing the turbulence in the ice-ocean boundary layer, the supply of oxygen and nitrate to the sea ice algae and fluxes of gases at the ice interface. Under-ice turbulence appears to be a key factor in controlling ice algal growth and should be parameterized in models to better represent the sea ice algae biogeochemistry. The under-ice turbulence was documented in 2020 in the Canadian Archipelago (Cambridge Bay in spring) and in the deep Arctic (Nansen and Amundsen Basin in summer). We used an eddy covariance system associated with fast Dissolved Oxygen (DO) sensors and nitrate sensors. We found that turbulent heat fluxes at the ice-ocean interface are about -2 W/m2, and DO fluxes vary from 0 to 150 mmol/m2/d. Variations will be linked to the sea ice algae productivity and current velocities, to try to understand the processes at the origin of these vertical fluxes.
Schulz K¹, Koenig Z², Muilwijk M*³, Bacuh D⁴, Zurita AQ⁵, Karam S⁶, Tippenhauer S⁵, Baumann T⁷, Hoppmann M⁵, Vredenborg M⁵, Granskog M³
¹Oden Institute for Computational Engineering and Sciences, The University of Texas, Austin, USA, ²UiT The Arctic University of Norway, Tromsø, Norway, ³Norwegian Polar Institute, Tromsø, Norway, ⁴Leibniz-Laboratory, University of Kiel, Kiel, Germany, ⁵Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany, ⁶University of Gothenburg, Gothenburg, Sweden, ⁷University of Bergen, Bergen, Norway
In recent decades, the Arctic Ocean has garnered growing scientific attention, but it has also undergone significant changes attributed to climate change. From October 2019 to October 2020, the Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) investigated the Eurasian part of the Arctic Ocean. This study presents the drift from a physical oceanography standpoint, examining water masses, currents, stratification, and the properties of the mixed layer. While the seasonal development of the upper water column is evident in our observations, the dominant changes we observed throughout the drift were spatial, rather than temporal. The mixed layer was found to be shallow in the Amundsen Basin, deep in the Nansen Basin, and its salinity was strongly correlated with the fraction of river water. Halocline heat fluxes were increased over the Gakkel Ridge and the Yermak Plateau. Additionally, thermocline heat fluxes were found to be higher in the Nansen Basin than in the Amundsen Basin, and higher over the Gakkel Ridge than over the Yermak Plateau. We compared the MOSAiC dataset with all available climatologies of the Arctic Ocean and found a good overall match. However, the MOSAiC observations showed a warmer and more saline Atlantic layer, as well as a shallower halocline and Atlantic Water core compared to climatologies. This comprehensive, one-year database of ocean properties is expected to serve as a reference for the Eurasian Arctic Ocean in 2020.
Gerke L*¹, Tanhua T¹², Arck Y²
¹GEOMAR Helmholtz Centre for Ocean Research, Kiel, Germany, ²Institute of Environmental Physics, Heidelberg University, Heidelberg, Germany
We evaluate changes in ventilation and circulation inside the Eurasian Arctic Ocean over three decades from 1991 to 2021, with the help of transient tracers (CFC-12 & SF6) measurements that constrain the transit time distribution (TTD), and by looking at changes in the Apparent Oxygen Utilization (AOU). The results show a decrease in ventilation (i.e., increasing mean age and increasing AOU) in the intermediate water between 250 and 1000 m in all areas of the Eurasian Arctic Ocean from 2005 to 2021. The vertical distribution of water showing this decrease in ventilation is increasing from south to north, being modest in the Shelf region (between 400 m and 1000 m) and most pronounced close to the Lomonosov Ridge (between 250m and 1000m). As this intermediate water is mainly fed by Atlantic Water entering from the Nordic Seas, our data indicate changes in the ventilation of this water mass. Analysis of the Arctic Ocean Boundary Current (AOBC) shows an increase in mean age and AOU over the years until 2021, suggesting a decrease in strength of the AOBC. The data from 1991 show comparable mean ages and AOU to the ones from 2021 in the intermediate water (except at the presence of the AOBC), being higher compared to 2005 and 2015. This indicates a slower ventilation being present in 1991 suggesting a decadal variability in ventilation in the intermediate water of the Eurasian Arctic Ocean.
Randelhoff A*¹, Koenig Z², Muilwijk M², Dodd P², Renner AHH³, Fransson A², Chierici M³
¹Akvaplan-niva AS, Tromsø, Norway, ²Norwegian Polar Institute, Tromsø, Norway, ³Institute of Marine Research, Tromsø, Norway
Turbulent mixing in the Arctic Ocean is undergoing drastic changes. Some evidence is starting to appear for both increases in internal wave energy and basin-scale erosion of double-diffusive staircases, but the consequences for turbulent and diffusive mixing on a larger scale remain difficult to quantify. Here, we present ongoing work on measurements from the 2021 and 2022 R/V Kronprins Haakon missions to the central Arctic Ocean's Amundsen and Nansen basins, where we sampled hydrography, turbulent microstructure, and inorganic nutrient concentrations. Dissipation of turbulent kinetic energy was reliably sampled only in the upper approx. 50 m of the water column, whereas deeper in the water column, background dissipation levels were usually below the instrument noise floor (O(10⁻⁹ W kg⁻¹)). Accordingly, we found double-diffusive staircases occurring both in the Amundsen and Nansen basins, whose presence we used to constrain background turbulent dissipation to at most O(10⁻¹⁰ W kg⁻¹). Upward double-diffusive heat fluxes are hence at least as important as turbulent ones at around O(0.1-1 W m⁻²), and slightly larger in the Nansen than the Amundsen Basin. Upward turbulent nitrate fluxes both across the surface layer base are in line with previous estimates made during winter, suggesting that wind-driven mixing does not regularly penetrate the surface stratification enough to affect mixed layer nutrient inventories. Double-diffusive nitrate fluxes likely did not play a role, based on a tentative calculation using salt fluxes across double-diffusive steps. The modest fluxes presented here do so far not show an enhanced turbulence regime during our observations and may suggest a continued tight control of large-scale stratification on upward heat and nutrient fluxes.
Haapala J*¹, Itkin P²
¹Finnish Meteorological Institute, Helsinki, Finland, ²UiT The Arctic University of Norway, Tromsø, Norway
Mass balance of the Arctic Sea ice depends on thermodynamical and dynamical factors. Thermodynamical and mechanical sea ice state variables are strongly coupled, but the strength of coupling varies in daily, seasonal, and climate time scales. When ice pack is thick, solid, and compact, this coupling is strong and large areas of pack ice are mechanically connected. In these circumstances, internal stress of pack ice is accumulating and reducing differences in ice motion. In these conditions drift speed of Arctic Sea ice decreases, age of ice increases and total mass of ice pack increases. On a contrary, thinner ice pack which includes cracks, leads or larger open water areas is in turn mechanically weakly connected, exhibits larger variations in motions in shorter time and length scales, drifts with higher speed and exhibits shorter residence time in the Arctic. In this talk, importance of ice dynamics on sea ice mass balance is reviewed and new findings based the MOSAiC campaign are discussed.
Carlig E¹, Ferrando S²³, Christiansen JS⁴, Lynghammar A⁴, Karamushko OV⁵, Rask Møller P⁴⁶, Ghigliotti L*¹
¹National Research Council of Italy, Institute for the Study of the Anthropic impacts and the Sustainability of the marine environment (IAS), Genoa, Italy, ²DISTAV - University of Genova, Genoa, Italy, ³National Biodiversity Future Center, Palermo, Italy, ⁴UiT The Arctic University of Norway, Tromsø, Norway, ⁵Murmansk Marine Biological Institute, Murmansk, Russia, ⁶Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark
Changes in habitat, prey availability, and distribution of species are considered major threats to biodiversity and ecosystem functioning. In the Arctic, warmer seas, changing hydrography, and loss of sea ice have implications for all components of marine life, including fishes that are indispensable for transferring energy from lower to higher trophic levels and, ultimately, support the structure and functioning of ecosystems. Ecomorphology, i.e., the integration of form, function, and ecology of species, discloses the functional role of specific forms as well as performance implications. When applied on a given fish species it may provide insights on its actual feeding mode as well as how it may meet environmental changes. We studied Arctic fish communities from the Northeast Greenland fjords and shelf. Selected morpho-functional traits were analyzed to investigate the ability of fish species to cope with distinct environmental scenarios and changes in prey availability. Comparative ecomorphological analyses of two pelagic fish species endemic to the Arctic, Arctogadus glacialis and Boreogadus saida, exemplify actual trophic behavior and niche partitioning. Mallotus villosus, a sub-Arctic pelagic counterpart, whose distribution is expanding northward in response to the ongoing warming, is also considered and the potential implications for feeding competition explored.
Armitage P*¹, Zhulay I², Fredriksen R³, Cautain I⁴, Bluhm BA⁵, Bonsdorff E¹, Christiansen JS⁵, Nordström M¹⁶
¹Åbo Akademi University, Åbo, Finland, ²University of Bergen, Bergen, Norway, ³Akvaplan-niva, Tromsø, Norway, ⁴Scottish Association for Marine Science, Oban, Scotland, ⁵UiT The Arctic University of Norway, Tromsø, Norway, ⁶University of Helsinki, Helsinki, Finland
Arctic ecosystems are increasingly affected by climate change and anthropogenic exploitation. To better understand the consequences of these changes on ecosystem functioning, knowledge about trophic structure and feeding relationships is as central as thorough descriptions of the biota. As part of our efforts to describe and document the under-explored zoobenthic communities of Northeast Greenland, we provide a comprehensive assessment of community structure, including trait-based diversity, along an inshore-to-offshore gradient, from coastal fjords, shelf, to shelf-break and upper-slope habitats. Using carbon and nitrogen stable isotopes as well as lipid biomarkers (highly branched isoprenoids, HBIs), we also explore the trophic characteristics of the communities. The taxonomic composition varied among fjord, shelf, shelf break and continental slope communities. The spatial structuring was also evident in traits composition, but with less distinction among habitats. Community stable isotopic niches, on the other hand, showed significant overlap among habitats. Ice-algal carbon contributed substantially to the benthic food web as evidenced through HBI analysis. The relative importance of sea-ice algae and phytoplankton in diets of zoobenthos provides information about realized food web structure along environmental gradients and reveals insight into the capacity of consumers to adapt to changes at the base of the food web.
Cautain IJ*¹, Last KS¹, Bluhm BA², Renaud PE³⁴, Ziegler AF²⁵, McKee D²⁶, Narayanaswamy BE¹
¹Scottish Association for Marine Science, Oban, Scotland, ²UiT The Arctic University of Norway, Tromsø, Norway, ³Akvaplan-niva, Tromsø, Norway, ⁴University Centre in Svalbard, Longyearbyen, Norway, ⁵Institute of Marine Research, Tromsø, Norway, ⁶University of Strathclyde, Glasgow, Scotland
Organic carbon supply is an important factor determining benthic community structure. In the Arctic, sympagic (ice-associated) primary producers can be an important food source for the benthos, but it is unclear how rapidly changing sea ice conditions may alter their role in benthic food-webs. Here, we use highly branched isoprenoids (HBIs) to estimate the proportion of sympagic and pelagic carbon in benthic food-webs on two Arctic shelves at similar latitudes: the highly productive, warm-water influenced Barents Sea, and the less productive, cold-water influenced East Greenland shelf. Sympagic carbon was less important for Barents Sea benthos than for East Greenland benthos (23±28% and 91±7% sympagic carbon in diets, respectively). This is likely due to the shorter period of ice cover in the Barents Sea resulting in a lower sympagic contribution to total primary production. The contribution of sympagic carbon to Barents Sea benthos was greater at higher latitudes (62±23% at >78.5 °N), where annual ice cover was longer. The overall lower variability in East Greenland fauna suggests less patchy input of sympagic or pelagic carbon. These results indicate that sympagic carbon can contribute substantially to carbon assimilated by the benthos in regions with extended periods of ice-cover. Changing ice conditions will lead to shifts in primary production regimes, with implications for benthic diets and, potentially, community structure and function.
Darnis G*¹², Geoffroy M²³, Daase M³⁴, Aubry C¹, Coguiec E³, Søreide J⁵, Berge J³, Babin M⁶⁷
¹Université Laval, Quebec City, Canada, ²Centre for Fisheries Ecosystems Research, Fisheries and Marine Institute of Memorial University of Newfoundland, St. John's, Canada, ³UiT The Arctic University of Norway, Tromsø, Norway, ⁴Akvaplan-niva, Tromsø, Norway, ⁵The University Centre in Svalbard, Longyearbyen, Norway, ⁶Takuvik International Research Laboratory, Universite´ Laval, Quebec City, Canada, ⁷Centre National de la Recherche Scientifique, Villefranche-sur-Mer, France
Copepods of the genus Calanus make the bulk of the mesozooplankton biomass in the arctic and subarctic seas and play a prominent role in the trophic transfer of energy and in the biogeochemical cycling of elements in the Arctic marine ecosystems. The Arctic Calanus complex of species is dominated by the two endemic Calanus glacialis and C. hyperboreus, and the smaller boreal-Atlantic expatriate C. finmarchicus transported by northward-flowing currents from the Atlantic Ocean over the Barents Sea and along the west Greenland coast. Due to the ongoing borealization of the Arctic through the main Atlantic and Pacific gateways, shifts in the composition of the Calanus complex have been observed with cascading effects on higher trophic levels. To address ecosystem disruptions with climate warming, the biogeographic patterns of these key pelagic species and ecological connectivity among the Arctic inflow, interior, and outflow shelves need to be better documented. Here we exploit a dataset of >500 zooplankton stations sampled from 1998 to 2021 to describe the spatial distribution of the dominant Calanus species over a vast expanse of the Arctic realm, from the Svalbard shelf and fjords inflow area to the western Labrador Sea outflow area. Interannual variability in the Calanus composition, populations’ development, and abundances is explored at sites in the Canadian Arctic Archipelago and northern Baffin Bay to further identify the drivers of the current Calanus distribution.
Weber C*¹², Juma GA¹², Meunier CL¹, Boersma M¹²
¹Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, Helgoland, Germany, ²University of Bremen, Bremen, Germany
Higher temperatures in the Arctic are expected to increase permafrost soil thawing, leading to a larger discharge of muddy, carbon-rich water into coastal areas. Higher turbidity and increased levels of dissolved organic carbon (DOC) in nearshore ecosystems are likely to affect the biomass and community structure of phytoplankton and bacteria that form the base of the marine food web. Higher turbidity will reduce light intensity, thereby directly impacting phytoplankton growth. With DOC being an important carbon source for bacteria, increasing DOC levels might promote bacterial growth. Changes in bacteria and phytoplankton communities can have significant consequences for the marine food web and ultimately affect the functioning of coastal Arctic ecosystems. We conducted a mesocosm experiment to determine the relative importance of light reduction and DOC levels in altering phytoplankton to bacterial biomass ratios and phytoplankton community structure. Natural plankton communities from Herschel Island (Beaufort Sea, Canada) were exposed to four different treatments: 1) a control treatment, 2) a treatment with addition of a clear carbon solution (no light attenuation), 3) a treatment with addition of light-reducing pigment (no carbon addition), 4) a treatment with addition of natural thaw slump material (light attenuation and carbon addition). Preliminary results indicate DOC impacting growth of planktonic communities more than light reduction.
Polukhin A*¹, Pronina J¹, Gusak G², Shchuka A¹, Pankratova N³, Flint M¹
¹Shirshov Institute оf Oceanology, Russian Academy of Sciences, Moscow, Russian Federation, ²University of Hamburg, Hamburg, Germany, ³Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, Moscow, Russian Federation
The water area of the Arctic Ocean is most of all in the World Ocean affected by global climate change, one of the important consequences of which is the change in the balance of carbon dioxide in the Arctic seas of Russia and the impact of its variability on the carbonate system of its waters. The Kara Sea and the Laptev Sea have the largest shelves areas. In addition, most of the continental runoff enters their water area, which determines the structure and, in part, the dynamics of waters on the shelf. The processes of transformation of organic matter occurring on the shelf and the variability of the balance of the carbonate system through the mechanism of cross-shelf and then cross-slope transport also have an impact on the waters of the Central Arctic Basin. The Shirshov Institute of Oceanology has been conducting research on the processes occurring on the shelf and slope under the program "Ecosystems of the Seas of the Siberian Arctic" since 2007. The results on the current state of the carbonate system of waters have been obtained, the intensity and spatial heterogeneity of the carbon dioxide flow at the water-atmosphere boundary have been studied, and long-term trends in the process of water acidification have been obtained. These results will provide a better understanding of the variability of the ecosystems of the Arctic seas against the backdrop of a changing climate in the Arctic and provide a forecast for their future development.
Henson H*¹, Sejr M¹, Sørensen LL², Holding J¹
¹Aarhus University, Aarhus, Denmark, ²Aarhus University, Roskilde, Denmark
High latitude marine waters are a large sink for anthropogenic CO2. Global surface warming is accelerating the retreat of the Greenland ice sheet and increasing meltwater discharge into fjord waters. This freshening of fjord ecosystems causes biogeochemical changes affecting the carbonate system as well as changes to fjord circulation that may affect future productivity and rates of CO2 uptake. Within Greenlandic fjords, the impact of freshwater discharge depends on local conditions, namely the position of the glacial terminus. Marine-terminating glaciers deliver freshwater partly through subglacial discharge. This incorporation of meltwater at depth leads to upwelling of nutrient rich, yet corrosive bottom water to the photic zone. Meanwhile, land-terminating glaciers deliver freshwater via rivers enhancing surface stratification and turbidity, leading to light and nutrient limitation. Glacial freshwater discharge is also extremely low in alkalinity. Freshwater incorporation from rivers or from subglacial discharge can therefore cause alkalinity dilution reducing the buffer capacity of water masses in fjords. Glacial meltwater therefore has the potential to drive CO2 fluxes by modulating both carbonate chemistry and biological activity. Data from field campaigns between 2016-2023 evaluate the magnitude of CO2 fluxes and elucidate the mechanisms by which freshening drives CO2 dynamics in Greenland coastal waters.
Ruiz-Castillo E*¹, Verdugo J¹, Rysgaard S¹
¹Arctic Research Centre, Aarhus University, Aarhus, Denmark
The onset of ice melt, while the ice cover remains, is a key period for physical and biological processes in the water column in the Arctic region. To assess the effects of local meltwater input we combined current and hydrographic data from moorings and CTD casts deployed in Young Sound Fjord, Greenland, during the transition from ice cover to ice free conditions. Our observations indicate that at the entrance of Young Sound melted, i.e., fresher water, generated a baroclinic instability and drove anticyclonic circulation. Fresher water was advected from the mouth into the fjord and seemed to recirculate back off the fjord. Furthermore, meltwater input onset stratification near the surface and triggered an under-ice phytoplankton bloom. This study suggests that most of the blooms occur prior to full ice break up.
Kuzyk ZZ*¹, Ehn J¹, Bruneau J¹, Gosselin M², Fink-Mercier C², Leblanc M⁴, O'Connor M³, Bélanger S², Noisette F², Giroux J-F⁴, Idrobo J³, del Giorgio, P⁴
¹University of Manitoba, Winnipeg, Canada, ²L'Université du Québec à Rimouski, Rimouski, Canada, ³University of British Columbia, Vancouver, Canada, ⁴Université du Québec à Montréal, Montréal, Canada
Results from two recent interconnected studies are presented: (i) a comprehensive coastal habitat research program in Eeyou Istchee (eastern James Bay) that examined the coastal oceanography, health of eelgrass (Zostera marina), and Canada Goose (Branta canadensis) use of the coastal habitat, and (ii) a characterization of marine heat wave events in the region between 1982 and 2022 using sea surface temperature (SST) data from satellite remote sensing. James Bay is the most southerly extension of the large (~1.25 x106 km2) Hudson Bay Inland Sea (HBIS) system, which lies along the outflow pathway of seawater from the Arctic Ocean. It experiences an annual sea ice freeze-melt cycle, that drives a feedback, in which the timing of ice breakup influences the amount of heat stored in surface waters during the summer months and a delay in fall freeze-up. Large and increasing additions of freshwater from both ice melt and river water maintain vertical stratification year-round in offshore waters and influence properties of surface and subsurface waters. Given the rapid loss of sea ice, the ice cover - SST interactions make the HBIS, and particularly James Bay at its southern margin, at risk of increasing frequency and severity of marine heat wave events. Of particular interest are the characteristics of a major marine heat wave event that occurred in spring 1998. Eastern James Bay experienced an unprecedented marine heat wave caused by early ice breakup. It is suspected to have played a role in transforming a gradual, probably localized decline of eelgrass ecosystems caused by hydroelectric development into a severe, large-scale decline, ultimately the largest scale eelgrass decline recorded in eastern Canada since the 1930s. It was one among many other large scale and local environmental changes discovered in the research program that likely jointly contributed to the eelgrass and goose declines.
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Poste AE*¹²
¹Norwegian Institute for Nature Research, Tromsø, Norway, ²UiT The Arctic University of Norway, Tromsø, Norway
Climate change is resulting in permafrost thaw, melting glaciers, and altered precipitation and runoff patterns; leading to altered inputs of freshwater and terrigenous material (sediments, nutrients, organic matter, and contaminants) from land to sea. However, there remain critical knowledge gaps related to how inputs from land shape Arctic coastal ecosystem structure and function, making it difficult to assess how future changes in these inputs could impact productive and important coastal ecosystems. Here we present results from recent interdisciplinary research in a river- and glacier-influenced high Arctic fjord system (Isfjorden, Svalbard) where a large team of collaborators has carried out extensive field-based research since 2017, focusing on riverine inputs of sediments, nutrients, organic matter and contaminants from land to sea and studying impacts of these inputs on physical and chemical conditions in coastal waters and sediments, and coastal ecosystem structure and function. These results reveal a broad range of physical, biogeochemical, and ecological responses to inputs from land. These responses are often shaped by the interaction between strong seasonality in magnitude and geochemistry of inputs from land and the strong seasonality inherent to Arctic marine ecosystem processes. In addition to summarizing key findings from recent research at Svalbard’s land-ocean interface, we also identify key research needs moving forward, including opportunities for improved pan-Arctic collaboration to understand how predicted increases in land-ocean inputs to the Arctic Ocean are likely to impact coastal ecosystem structure and function.
Grebmeier J*¹, Cooper L¹, Frey K², Goethel C¹³, Moore S⁴
¹Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, Solomons, United States, ²Clark University, Worcester, Massachusetts, United States, ³St. Mary's College of Maryland, St. Mary's City, Maryland, United States, ⁴Department of Biology University of Washington, Seattle Washington, United States
The Arctic ecosystem is undergoing change due to warming seawater temperatures and declining sea ice cover on regional to pan-Arctic scales. Changes observed in the biological system range from increasing primary productivity seasonally, but varying by region, changes in organic carbon cycling, trophic boreal species range expansion as well as Arctic species contractions, and impacts to upper trophic seabird and marine mammal populations and migration patterns. The Distributed Biological Observatory (DBO) is a successful example of a change detection array where international cooperation on a scientist-to-scientist basis is tracking the status and trends of the marine ecosystems of the Bering Strait region. Expansion of the DBO into a pan-arctic network is occurring with the developing Atlantic, Davis Strait/Baffin Bay and Siberian DBOs that will strengthen our ability to synergistically observe, track and model ecosystem impacts of a warming climate and ocean. Stressors in the Pacific Arctic associated with climate warming, such as increasing harmful algal blooms and ocean acidification, have a direct impact on food security for coastal communities as well as potentially commercial fisheries. This presentation will discuss key processes occurring over the inflow shelves of the northern Bering/Chukchi seas in the Pacific Arctic and the connections to processes in the high Arctic and beyond.
Ashjian C*¹, Okkonen S², Campbell R³, Robert P¹
¹Woods Hole Oceanographic Institution, Woods Hole, USA, ²University of Alaska Fairbanks, Fairbanks, USA, ³University of Rhode Island, Narragansett, USA
Water, and intrinsic plankton, in the Chukchi Sea originate in the Bering Sea and flow through the Chukchi Sea to exit the shelf to the basin. Thus, plankton populations in the Chukchi Sea likely are replaced annually and are not maintained as permanent residents. Here two case studies demonstrating the importance of the flow-through system to Chukchi Sea zooplankton populations will be presented. The annual replacement was observed from two bio-physical surveys, in early-winter 2011 and in late-spring 2014, that described the distributions of the dominant copepod Calanus glacialis relative to seasonal hydrography. Interannual variability in atmospheric forcing can have a substantial impact on spring evolution of the Chukchi Sea, including the timing of sea ice retreat, of northward expansion of springtime introduced Bering Sea water, and of the replacement of overwintering plankton populations with newly introduced animals. This interannual variability was observed in a late-summer 13-year study near Pt. Barrow, Alaska. The annual replacement has implications for whether plankton populations in the Chukchi Sea could ever increase in abundance and biomass substantially, since even if recruitment is high, the recruits are ejected into the Arctic basin where environmental conditions may be less favorable for persistence. The Chukchi Sea may remain benthically dominated, since the zooplankton populations never increase in biomass sufficiently to have a substantial grazing impact.
Primicerio R*¹², Pecuchet L¹, Souster T¹
¹UiT The Arctic University of Norway, Tromsø, Norway, ²Institute of Marine Research, Tromsø, Norway
Arctic marine ecosystems are undergoing rapid climate-driven reorganization fueled by species redistributions. The impact of climate warming on biodiversity and ecosystem organization affects exposure and vulnerability to multiple stressors, ultimately determining cumulative risk. The changes in biodiversity and food web structure observed during the last twenty years in the Barents Sea and along the North Norwegian coast help illustrate the pace and magnitude of the ongoing ecosystem reorganization in the High North. The rapid borealization of these Arctic marine communities, driven by poleward distributional shifts, has changed the functional character of species and the configuration of feeding relationships. The ecological changes are concomitant with the northward expansion of human activities such as fisheries, aquaculture and oil and gas extraction. The redistribution of species and human activities changes the character of exposure to multiple stressors in these ecosystems. In turn, the ecological reorganization affects the ecosystem internal stability, or robustness to perturbations, and its invasibility by new incoming species. The documented changes in ecosystem organization and exposure to multiple stressors provide the context for considerations of the ensuing cumulative risk and of its adaptive management.
Sivel E*¹, Planque B², Lindstrom U²³, Yoccoz NG³
¹School of Marine and Atmospheric Science, Stony Brook University, Stony Brook, USA, ²Institute of Marine Research, Tromsø, Norway, ³UiT The Arctic University of Norway, Tromsø, Norway
Species biomass in the Barents Sea display large fluctuations which can originate from internal processes, stochasticity, external drivers, or all three combined. Examining variability resulting from internal processes and stochasticity can help in better understanding the complementary role of external drivers, (e.g., climate change and fisheries) and thereby contribute to inform management policies. In this study, we use the dynamic stochastic model of the Barents Sea food-web named NDND (for Non-Deterministic Network Dynamics) to explore variability resulting from internal processes and stochasticity. We simulate the dynamics of the Barents Sea food-web under multiple scenarios of temperature and fishing mortality and measure how the stability of the food-web is altered under these combined scenarios. We measure the cumulated impacts of temperature and fishing on stability and assess if these are additive, synergistic, or antagonistic. Colder scenarios display synergism between temperature and fisheries while warmer scenarios show antagonistic effects. The conclusion of this study advocates for the importance of using approaches accounting for possible combined effects of multiple external drivers to define future management policies. This study is the only one explicitly looking at the response of food-web variability to impacts of human activities in the Barents Sea. It could open to the study of extreme events and become a useful tool for risk-based management.
Ziegler A*¹², Jørgensen LL², Bluhm B¹
¹UiT The Arctic University of Norway, Tromsø, Norway, ²Institute of Marine Research, Tromsø, Norway
Reduced Arctic sea-ice cover has been shown to alter phytoplankton community composition and reduce the magnitude of vertical flux, thereby reducing the strength of pelagic-benthic coupling. It is predicted that Arctic shelf ecosystems, like the Barents Sea, will transition into sub-polar-like ecosystems under future climatic conditions. However, few studies have provided a benthic perspective to the question of how ice-free conditions in the Arctic will affect food web structure. In this study, we aim to test whether ice-free summer conditions in the Barents Sea and adjacent Nansen Basin alter benthic food web structure and the strength of pelagic benthic coupling. To do so, we used bulk stable isotopes of carbon and nitrogen measured in food sources and benthic consumers, demersal fish, and zooplankton collected during summers with contrasting sea-ice conditions: August 2018 – low sea-ice extent and August 2019 – high sea-ice extent. We compared benthic food web structure across three oceanographically distinct regions from the sea-ice free central Barents Sea shelf and the seasonally ice-free northern Barents Sea shelf to the slope extending into the Nansen Basin. The results of this work will not only improve our understanding of the impact that Arctic sea-ice loss has on benthic communities but also provide additional insight to the resiliency of Arctic benthic food webs.
Bodur YV*¹, Renaud PE², Wiedmann I¹, Assmy P³, Reigstad M¹
¹UiT The Arctic University of Norway, Tromsø, Norway, ²Akvaplan-niva, Tromsø, Norway, ³Norwegian Polar Institute, Tromsø, Norway
The Arctic Ocean is an important sink for atmospheric CO₂. The biological carbon pump is a substantial part of this mechanism, and vertical flux of organic matter is especially efficient on Arctic shelves. However, the Arctic is undergoing rapid change due to sea ice loss and increased inflow of Atlantic and Pacific Water. These changes will have consequences for the entire marine ecosystem, including processes that affect the biological carbon pump. We compare downward carbon flux in the Barents Sea from studies carried out during the last 25 years with other Arctic shelf regions in order to identify the differences and similarities of drivers of the biological carbon pump in the Arctic. Since export of organic matter is most efficient when high primary production is present, we expect highest downward flux of carbon on the productive inflow shelves. However, since investigations have been mostly carried out during summer, and less studies are present from interior and outflow shelves, overarching conclusions are challenging. It is important to evaluate vertical flux on a pan-Arctic level in order to assess how the biological carbon pump responds to drastic changes in this region.
Basedow SL*¹, Granaas T¹, Dunn M²³, Daase M¹, Sundfjord A⁴, Leu E², Renaud P²
¹UiT The Arctic University of Norway, Tromsø, Norway, ²Akvaplan-niva, Tromsø, Norway, ³Memorial University, St Johns, Canada, ⁴Norwegian Polar Institute, Tromsø, Norway
The polar front ecosystem in the Barents Sea is markedly affected by Atlantification. Recent observations indicate that during the peak production period in spring there might be a spatio-temporal mismatch between primary production and pelagic secondary production. Calanus spp. copepods are important secondary producers in Atlantic and Arctic food webs and are advected in large quantities into the Barents Sea, however, the timing of peak advective input may not match local peaks in primary production. Here, we investigate spatio-temporal patterns of advection and secondary production in May/June (2011, 2022) based on a suite of optical and acoustic sensors (laser optical plankton counter, underwater video profiler, Sailbuoy equipped with active acoustics, ADCP) and experiments (egg production). Preliminary results indicate that Calanus spp. egg production accounts for between 5 and 15% of the total secondary production during the spring bloom and that the advective inflow of Calanus arrived too late (end of June) to fully utilize the peak in the phytoplankton bloom. Future scenarios are discussed.
Leu E*¹, Campbell K², Lenss M², Miettinnen A², Gradinger R², Bedington M¹, Basedow S², Daase M²³, Renaud P¹³
¹Akvaplan-niva, Tromsø, Norway, ²UiT The Arctic University of Norway, Tromsø, Norway, ³The University Centre in Svalbard, Longyearbyen, Norway
Oceanic fronts are considered hotspots of production due to different water masses meeting, which both may lead to upwelling of nutrient-rich waters and concentration of biota advected. In the Barents Sea, Atlantic water inflow is increasing with cascading effects throughout the entire ecosystem. Understanding how this Atlantification impacts primary production in the Polar Front area is key to assess climate change impacts on future ecosystem functioning. At high latitudes, pelagic primary production peaks during a few weeks in spring when the bulk of the annual new production takes place. As this happens in partly ice-covered waters, and most monitoring efforts are being carried out during the ice-free summer season, there is a lack of high-resolution data on primary productivity during this critical period. We report here unprecedently high phytoplankton biomass values from two cruises to the Barents Sea Polar Front in May (2021/2022), seemingly invisible by remote sensing, and combined with high production rates. Physiological measurements further indicate that nutrient availability was the main factor limiting production at this stage, while grazer abundances were surprisingly low. Absence of top-down control by grazing has likely contributed to the high biomass production we observed, but its underlying cause remains unclear. Increased Atlantification of this area may therefore lead to higher primary production – while additional data collected within the ongoing PolarFront project suggest that this high biomass is less available for pelagic zooplankton, with negative consequences for pelagic secondary production.
Renner AHH*¹, Bailey A², Reigstad M³, Sundfjord A², Chierici M¹, Jones E¹
¹Institute of Marine Research, Tromsø, Norway, ²Norwegian Polar Institute, Tromsø, Norway, ³UiT The Arctic University of Norway, Tromsø, Norway
Changing Atlantic Water (AW) inflow promotes sea ice decline and borealisation of marine ecosystems and affects primary production in the Eurasian Arctic Ocean. North of Svalbard, the AW inflow dominates oceanographic conditions along the shelf break, bringing in heat, salt, and nutrients. However, interaction with sea ice and Polar Surface Water determines nutrient supply to the euphotic layer. We investigate the role of sea ice for hydrography, nutrients and seasonal dynamics of chl a, based on a combination of satellite data and in-situ measurements from a transect across the AW inflow at 31 °E, 81.5 °N, visited regularly since 2012. Large interannual variability in hydrography, nutrients and chl a indicates varying levels of nutrient drawdown by primary producers over summer. Sea ice conditions impact surface stratification, light availability, and wind-driven mixing, with a strong potential for steering chl a concentration over the productive season. In early winter, nutrient re-supply through vertical mixing varied in efficiency, again related to sea ice conditions. The re-supply elevated nutrient levels sufficiently for primary production but likely happened too late in the season when high-latitude light levels limited potential autumn blooms. Such multidisciplinary observations are key to gain insight into the interplay between physical, chemical, and biological drivers and to understand ongoing and future changes, especially at this entrance to the central Arctic Ocean.
Jones E*¹, Chierici M¹², Fransson A²³, Assmann K¹, Renner A¹
¹Institute of Marine Research, Tromsø, Norway, ²UNIS - The University Centre in Svalbard, Longyearbyen, Norway, ³Norwegian Polar Institute, Tromsø, Norway
Atlantification with warming, loss of sea ice and increased influence of Atlantic Water, will impact biogeochemical cycling and ocean acidification in the Barents Sea. Variability and drivers of the carbonate system (inorganic carbon, alkalinity) were determined in summer (July, August) of three years (2018, 2019, 2021) of contrasting sea-ice conditions in the northern Barents Sea. In summer 2018, the region was largely ice free and the water column was generally warmer and more saline, representing Atlantic-like conditions. Greater Atlantic Water influence supplied the surface layer with nutrients and alkalinity, the natural buffer capacity of seawater. Primary production, biological carbon uptake and increased alkalinity enhanced calcium carbonate saturation states in the upper ocean in the ice-free, Atlantic-like regime. In summer 2019, greater sea-ice cover remained in the northern Barents Sea and created more Arctic-like conditions. Sea-ice meltwater was an important driver of biological carbon uptake, which was delayed in the ice-covered waters in 2019 relative to 2018. Summer 2021 represented an intermediate situation with retreating sea ice and meltwater input driving change in the carbonate system in surface waters. These findings indicate that future Atlantification may increase biological CO2 drawdown, reduce dilution effects, and may partly counteract acidification in the Barents Sea.
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