Session chairs:
Katrine Husum (Norwegian Polar Institute, Norway), Christian März (University of Bonn, Germany), Christine Tømmervik Kollsgård (UiT The Arctic University of Norway, Norway)
Session content:
On a geological time scale, the Arctic Ocean has changed dramatically from greenhouse to icehouse conditions. The marine environment of the Arctic Ocean, and its adjoining margin and shelf seas, gradually evolved into their present form since the termination of the Last Glacial Maximum. Over these ~20,000 years, climate, ecosystems, and the depositional setting developed into their modern expressions. Landforms at the seafloor and the sediment below are archives of environmental fluctuations caused by natural drivers. These morphological and sedimentary archives serve as records of natural baseline values increasing our understanding of the current rapid changes in the Arctic Ocean region. Certain time intervals may also serve as analogues for warmer-than-present conditions and elucidate effects on climate and ecosystems. Talking many of these aspects into account, session C will provide some environmental lessons from the past.
Session chairs:
Bodil Bluhm (UiT The Arctic University of Norway, Norway), Sławomir Kwaśniewski (The Institute of Oceanology of the Polish Academy of Sciences, Poland), Julia Giebichenstein (University of Oslo, Norway)
Session content:
Ecosystems are structured and function in an inextricable relationship between their biota and environment. Environmental conditions drive spatial patterns of biological communities and their function. In the Arctic Ocean, environmental transitions can be gradual or abrupt. They include shifts in water depths from coasts to basins, light regimes from summer to winter, open water to complete sea ice cover, fully marine to estuarine habitats, varying water masses and seafloor properties across fronts and bathymetric features. Resident biota are adapted to the original Arctic environments, and these adaptations act in harmony with multitude of biotic interactions, yet may shift in response to human impact. These corroborating processes influence community structure and function, creating additional complexity which should be understood in order to monitor or manage Arctic ecosystems. Currently, Arctic environments are changing at a rapid pace. The ongoing climate change shows that some of the established links that make up a stable system can alter or even collapse. Thus, the living ocean is a highly complex system, but session B will provide some new aspects contributing to a better understanding.
Session chairs:
Frank Nilsen (UNIS, Norway), Mary-Louise Timmermans (Yale University, USA), Laura Castro de la Guardia (Norwegian Polar Institute, Norway)
Session content:
Some of the excess heat absorbed by the world oceans is transported poleward. At the intersection between the Arctic and sub-Arctic domain, the Polar front forms a fundamental regional feature, and the advected heat causes warming, freshening and changes in the circulation dynamics in the Arctic Ocean itself. This, in turn, affects the Arctic climate and has implications for sea ice, atmosphere, and terrestrial environment. The influence of large-scale patterns (wind forcing, buoyancy loss and large-scale advection) on regional features in the northern Barents Sea and Nansen Basin have been investigated in the Nansen Legacy project. In this session, we aim to integrate these findings into pan-Arctic perspectives and improve our understanding of the ocean-ice-atmosphere system and its drivers in the entire Arctic Ocean.
Eilertsen VT*¹, Rydningen TA¹, Forwick M¹, Laberg JS¹
¹Department of Geosciences, UiT The Arctic University of Norway, Tromsø, Norway
During the Late Weichselian glaciation, the Svalbard-Barents Sea Ice Sheet covered the central and northern Barents Sea and extended to the shelf break. Action of grounded ice resulted in formation of glacial landforms such as streamlined ridges/grooves, grounding-zone wedges, and recessional moraines. The action of grounded ice also resulted in deposition of muddy glacigenic diamicts. A cover of proximal glaciomarine deposits capped by Holocene marine muds overlies these diamicts. Analysing the landforms, as well as investigating the sediments can give information of past ice flow directions and the dynamics of the glacial retreat. This study aims to reconstruct the glacial dynamics and time the retreat of the northern part of the Svalbard-Barents Sea Ice Sheet, in addition to reconstruct the sedimentary environment on the northern part of the Barents Sea shelf from the last glacial to the present. A total of five gravity cores (1.15 to 5.05 m long) were retrieved from water depths of ca. 250-550 m in the Kong Karl’s Trough, Erik Eriksen Strait and Kvitøya Trough during the Nansen Legacy Paleo-cruise in 2018. High-resolution sub-bottom profiles and multi-beam swath bathymetry were also acquired during the cruise. Results from multi-proxy analyses of the sediment cores including physical properties, grain size distribution, lithostratigraphy and XRF will be presented, combined with new multi-beam swath-bathymetry and high-resolution Topas seismic data.
Tømmervik Kollsgård C*¹, Laberg JS¹, Rydningen TA¹, Husum K², Lasabuda APE¹, Forwick M¹
¹UiT The Arctic University of Norway, Tromsø, Norway, ²Norwegian Polar Institute, Tromsø, Norway
The northern Barents Sea continental slope is a key area for understanding the history of the northern Svalbard-Barents Sea Ice Sheet and the along-slope flowing ocean current in the area. The Kvitøya Trough Mouth Fan formed offshore of the Kvitøya Trough due to paleo ice streams that eroded and transported sediment during reoccurring glaciations of the trough, including the last glacial period. The ocean current is an extension of the West Spitsbergen Current and transports modified Atlantic Water to the Eurasian part of the Arctic Ocean northeastward along the upper continental slope. We reconstruct the past ice sheet dynamics and current regime by interpreting the sedimentary processes of the Kvitøya Trough Mouth Fan and the adjacent slope from six sediment cores (ranges from 0.43 to 5.45 m long). Based on grain sizes, sediment structures, color, and physical properties (wet bulk density, shear strength, and water content), we have identified three main lithofacies. These reflect different sedimentary processes including suspension settling, iceberg and sea ice rafting, down-slope sediment transport by gravity flows and sediment sorting from ocean currents. The timing of these events will be discussed based on radiocarbon dates of microfossils (planktic foraminifera) and correlations of magnetic susceptibility and paleomagnetism across the cores.
Rydningen TA*¹, Trælvik Eilertsen V¹, Tømmervik Kollsgård C¹, Husum K², Forwick M¹, Laberg JS¹, Lasabuda A¹, Ninnemann US³
¹Department of Geosciences, UiT The Arctic University of Norway, Tromsø, Norway, ²Norwegian Polar Institute, Longyearbyen, Norway, ³Department of Earth Science, University of Bergen, Bergen, Norway
We have studied the ~300 km long Erik Eriksen and Kong Karls straits and the ~200 km long Kvitøya Trough and assoicated trough-mouth fan in order to reconstruct the last glacial history of the northern Barents Sea. Our findings include a major grounding zone wedge in the Kong Karls Strait, glacial lineations within the Kvitøya Trough, and several sets of cross-cutting moraines ridges. The trough-mouth fan formed from mass-wasting processes during repeated advances of the Svalbard-Barents Sea Ice Sheet to the shelf break, while contourites west and east of the fan deposited from eastward-flowing ocean currents. Our findings reveal that there were two different ice domes during the last glacial, one on Spitsbergen (draining eastwards) and one between Nordaustlandet and Kvitøya (draining northwards). We show several grounding events during a dynamic ice retreat, controlled by inflow of warm water masses, sea-level changes, and the seabed topography. This new reconstruction improves our knowledge of deglaciation and ice sheet evolution in northern Barents Sea during warmer-than-present conditions in the past. Yet, with vast areas still unexplored, including the continental slope, more research expeditions acquiring geophysical and geological data are required to fully constrain the regional ice-sheet dynamics, ocean current variability during the last glacial and Holocene, and the longer climate evolution of the Arctic Ocean.
Gray R*¹, Tessin A¹, März C², Husum K³
¹Kent State University, Kent, United States, ²University of Bonn, Bonn, Germany, ³Norwegian Polar Institute, Tromsø, Norway
Fe can act as a limiting nutrient for primary productivity and reactive Fe minerals play a key role in carbon, nutrient, and trace metal cycling. Delivery and reactivity of Fe can both be affected by glacial conditions, and glacial variations on Svalbard during the Holocene may have driven changes in Fe delivery and speciation. We analyzed sediment cores from the Barents Sea shelf and slope to determine the concentration and reactivity of Fe deposited during the Holocene. Gravity cores were collected from the Barents Sea during the Nansen Legacy Paleo Cruise in 2018. We used sequential extractions to determine the contents of Fe in four mineral phases: poorly crystalline Fe (oxyhydr)oxides, Fe associated with carbonate, crystalline Fe (oxyhydr)oxides, and Fe in magnetite. The most reactive phase, Fe in poorly crystalline oxides, showed the greatest variation across the shelf sites. Enrichments in reactive Fe in the upper 100 cm of the shelf sites suggest changes in Fe delivery during the Late Holocene. Based on preliminary age models, these results suggest that reactive Fe delivery to the continental shelf is enhanced during glacial readvance on Svalbard in the Holocene. However, the timing of increased reactive Fe intervals in the Holocene appears to differ between the shelf and slope sites. Further analysis of the slope site may offer insight into the pre-Holocene history of Fe delivery.
Anglada-Ortiz G*¹, Rasmussen TL¹, Chierici M², Fransson A³, Zamelczyk K¹, Ziveri P⁴, Meilland J⁵, Garcie-Orellana J⁴
¹UiT The Arctic University of Norway, Tromsø, Norway, ²Institute of Marine Research, Tromsø, Norway, ³Norwegian Polar Institute, Tromsø, Norway, ⁴ICTA-Institute of Environmental Sciences and Technology, Autonomous University of Barcelona, Barcelona, Spain, ⁵MARUM-Center for Marine Environmental Sciences, Bremen, Germany
Anthropogenic CO2 emissions are causing global environmental changes, such as ocean warming and acidification. Effects of ocean acidification have been observed in planktic foraminifera which contribute significantly to the ocean carbon cycle. When they die, they sink to the seabed and usually get preserved in the sediment recording the characteristics of the water column from when they were alive. Hence, their fossil calcareous shells can be used as proxies in paleoenvironmental reconstructions. The species composition and abundance of the faunas through time have been used to reconstruct past oceanography, climate and productivity, and the chemical composition of their shells, to reconstruct water mass properties. In this study, we have analyzed their abundance, size, and species distribution patterns together with 𝛿13C, 𝛿18O and total organic carbon (TOC), total carbon (TC) and calcium carbonate (CaCO3) content in two sediment cores from the northern and southern Barents Sea. In the north, we observed low concentration of foraminifera (2.1 ind g-1) dominated by Neogloboquadrina pachyderma (91%). This contrasts with higher abundances (20 ind g-1) and biodiversity in the south, where N. pachyderma only constituted 22% of the fauna that was dominated by the subpolar species. The almost absence of foraminifera in the upper half of the northern site as well as the permanently low content of CaCO3 were attributed to CaCO3 dissolution in the sediment, possibly driven by the decomposition of organic matter, the presence of solely agglutinated specimens and the observed seasonal variability of living foraminifera in the area.
Tessin A*¹, März C, Faust J, Böning P, Forwick M, Gray R, Matthiessen J, Neumann A, O’Regan M, Schnetger B
¹Kent State University, Kent, United States
Climate warming in high latitude terrestrial regions has the potential to significantly influence ocean biogeochemical cycling through increased delivery of freshwater, nutrients, and organic material. Changes in iron (Fe) input from terrestrial regions is especially important because Fe is a bio-essential micronutrient, can control the sedimentary cycling of macronutrients (phosphorus), and can increase sedimentary preservation of organic carbon. Sedimentary records of past biogeochemical cycling are, therefore, important to evaluate and predict the effects that changes in the input of Fe-rich terrigenous material to the Arctic Ocean will have on nutrient cycling and organic carbon burial. Further, the mobilization, transport, and deposition of Fe minerals can provide key context for how ice sheets are changing.During a 2015 Polarstern expedition, sediment cores were retrieved north of Svalbard, on the Yermak Plateau. Based on age constraints, the PS92/39-2 core includes sediments the past two glacial cycles, including intervals of retreat and advance of the Svalbard Barents Sea ice sheet. Here we present XRF analyses to quantify and evaluate changes in biogeochemical cycling in this region during the past two glacial cycles. A series of high Fe delivery events are recorded with Fe contents of up to 9.8 wt.% and easily reducible Fe contents of up to 1.3%. Pulsed delivery of Fe is likely associated with increased delivery of material from northern Svalbard, which is dominated by Fe-rich Devonian red beds. Tight coupling between Fe and P concentrations throughout the record suggests that changes in Fe cycling impacted other nutrient cycles in the region.
Irvali N*¹, Ninnemann U¹, Liltved A¹, Lefèvere S¹, Husum K², Jansen E¹
¹Department of Earth Science and Bjerknes Centre for Climate Research, University of Bergen, Bergen, Norway, ²Norwegian Polar Institute, Tromsø, Norway
The recent decline in Arctic sea ice extent has been linked to increased ocean heat transport with the Atlantic Water (AW), i.e., the Atlantification of the Arctic Ocean. Here we evaluate how current changes compare in pattern and magnitude to the longer-term natural variability in AW properties and their relationship to sea ice through the Holocene. We use a sediment core from the northern Barents Sea (KH18-10-14-GC1; 80.68 °N, 28.95 °E; 552 m). Stable isotopes (δ18O and δ13C) of planktonic (N. pachyderma) and benthic foraminifera (N. labradorica, C. lobatulus and C. neoteretis) are used to reconstruct the physical and chemical properties of the AW over the last ~12 000 years. Our N. pachyderma δ18O values generally covary with the epibenthic C. lobatulus δ18O values through the Holocene suggesting there was always a presence of AW at the site and not a strong halocline dominance. Our planktonic and benthic stable isotope records indicate a sudden warming/freshening (δ18O decrease by ~1‰) in AW properties at ~9 ka BP, in phase with an increase in sea ice concentrations (SpSIC %) in the northern Barents Sea (>80 °N). This indicates that natural variability in the region involved a close coupling between AW properties and sea ice extent. However, this past sea ice-AW coupling contrasts sharply to the recent changes suggesting modern changes are quite distinct from natural variability in the region and have a potentially different (anthropogenic) origin.
Ninnemann U*¹, Irvali U¹, Lefevere SP¹, Liltved A¹, Nesbø J¹, Husum K², Kleiven K¹, Jansen E¹
¹Department of Earth Science and Bjerknes Centre for Climate Research, University of Bergen, Bergen, Norway, ²Norwegian Polar Institute, Tromsø, Norway
The buoyancy (heat) loss by Atlantic Water (AW) along its horizontal circulation path is important for water mass transformation, contributing substantially to the Atlantic Meridional Overturning Circulation (AMOC). The Arctic, specifically sea ice and the Arctic halocline, represents the northern terminus of this water mass transformation. While AMOC is likely to weaken with future warming and freshening, declining sea ice may increase heat loss, complicating projections. To better constrain how sea ice, freshwater, and Arctic-Atlantic exchanges are linked to abrupt changes in AMOC and climate we reconstruct changes in AW inflow to the arctic across the last deglaciation. Using Barents Sea sediment cores, we show that changes in the properties of AW are tightly coupled to abrupt changes in North Atlantic climate and AMOC. Like previous work, we find that AW may have warmed abruptly during periods of weaker AMOC. Yet, our kinetic proxy suggests no associated increase in AW (in)flow as was previously suggested to explain this warming. New results from a site in the subpolar North Atlantic suggest that changes in AW inflow properties are out of phase with both surface outflow properties and North Atlantic climate. We show how Arctic-Atlantic exchanges were linked to abrupt climate and AMOC changes over the deglaciation and suggest that as the overall climate and cryosphere evolved so too did the relationship between AMOC, Arctic-Atlantic exchanges, and climate.
Gradinger R*¹, Amargant Arumi M¹, Assmy P², Bluhm B¹, Bodur YV¹, Bratbak G³, Castro de la Guardia L², Duarte P², Eriksen E⁴, Górska B⁵, Hop H², Ingvaldsen RB⁴, Müller O³, Pedersen T¹, Reigstad M¹, Svensen C¹, Wlodarska-Kowalczuk M⁵, Wold A² and other contributors
¹UiT The Arctic University of Norway, Tromsø, Norway, ²Norwegian Polar Institute, Tromsø, Norway, ³University of Bergen, Bergen, Norway, ⁴Institute of Marine Research, Bergen, Norway, ⁵The Institute of Oceanology of the Polish Academy of Sciences (IO PAN), Sopot, Poland
The Barents Sea is a highly complex system, influenced by strong environmental gradients between a relatively warm southerly Atlantic-influenced domain and the cold and seasonally ice-covered Arctic domain in the north. Within the system, organisms occur in distinct communities in three domains (sea ice, water column, sea floor), each with their own temporal and spatial dynamics. These systems are also linked through vertical flux, particularly during the spring production and subsequent ice melt, and during mixing events during autumn storms. The Nansen Legacy project resolved important patterns and drivers of biological processes in seasonal field expeditions at defined stations, augmented by remote sensing data, and regional monitoring and ecosystem modelling. The results of the individual cruises revealed substantial differences in biomass and productivity, tightly linked to the annual cycle of ice, light and primary production. Annual primary production estimates based on combined in-situ data, remote sensing and ecosystem model efforts revealed a strong latitudinal gradient from >100 g C m⁻² y⁻¹ in the south to <50 g C m⁻² y⁻¹ in the north. This contribution will extent such estimates to annually integrated values for the marine biological production on trophic levels from microbes to fish and for the sea ice, pelagic and benthic realms based on a combination of field data and modelling output.
Kwaśniewski S*¹, Altenburger A², Assmy P³, Bluhm B², Dabrowska A¹, Edvardsen B⁴, Goraguer L²³, Gradinger R², Grzelak K¹, Jordà Molina E⁵, Kovacs KM³, Lydersen C³, Majaneva S⁶⁷, Marquardt M², Ormanczyk M¹, Reiss H⁵, Renaud PE⁸, Saubrekka K⁹, Tatarek A¹, Thiele S¹⁰, Vader A¹¹, Wernström J², Wlodarska-Kowalczuk M¹, Wold A³, Øvreås L¹⁰ and other collaborators
¹Institute of Oceanology Polish Academy of Sciences, Sopot, Poland, ²UiT The Arctic University of Norway, Tromsø, Norway, ³Norwegian Polar Institute, Tromsø, Norway, ⁴University of Oslo, Oslo, Norway, ⁵Nord University, Bodø, Norway, ⁶Norwegian University of Science and Technology (NTNU), Trondheim, Norway, ⁷Akvaplan-niva, Trondheim, Norway, ⁸Akvaplan-niva, Tromsø, Norway, ⁹University of Oslo, Oslo, Norway, ¹⁰University of Bergen, Bergen, Norway, ¹¹University Centre in Svalbard, Longyearbyen, Norway
Biodiversity patterns shape and drive ecosystem processes and functions in the global ocean. Given the changing climate and recent agreements to protect ocean regions, current estimates of biodiversity must be assembled. Here, we present new estimates and spatial patters of taxon richness from microbes to mammals from a shelf-to-basin transect in the northern Barents Sea and southern Nansen Basin from seasonal sampling in 2018-2022 by the Nansen Legacy project. We find that estimates of taxon richness are higher on the shelf than in the basin for pelagic protists, zooplankton, and benthic macrobenthos, nematodes, and prokaryotes, but not for sympagic protists. Taxon richness varied seasonally for pelagic prokaryotes, protists, and zooplankton, but little for sympagic meiofauna, benthic prokaryotes and macrobenthos. Unsurprisingly, taxon richness was generally highest for single-celled taxa. Taxon-rich groups included: sympagic diatoms; pelagic prokaryotes (e.g., Alphaproteobacteria), diatoms, dinoflagellates, copepods; and benthic prokaryotes (with abundant taxa, e.g., Candidatus nitrosopumilus and Woesia), nematodes, and polychaetes. Unexpectedly absent - though known from earlier studies - were, for example, nematodes in sea ice. Ironically, at top (and perhaps other) trophic levels species richness is likely to be enhanced regionally for some time, while losses of Arctic (endemic) species will impact global biodiversity, and potentially Arctic ecosystem functioning.
Souster T*¹², Barnes D², Primicerio R¹, Jørgensen L³
¹UIT The Arctic University of Norway, Tromsø, Norway, ²The British Antarctic Survey, Cambridge, United Kingdom, ³Institute of Marine Research, Tromsø, Norway
Sustained intense warming has led to massive polar seasonal sea ice losses. This can cause new and longer phytoplankton algal blooms, and responsive growth increases of benthos, driving increases in zoobenthic blue carbon (carbon held within marine animals). This is important because it is a potential negative feedback on climate change (warming decreases marine ice, which increases algal bloom duration, benthic growth, and seabed carbon storage with sequestration potential). Does habitat type in the Barents Sea influence the quantity of zoobenthic carbon stored and the benthic functional groups present. This information could then feed into designation prioritization and management plans for protection of areas with high blue carbon values, as part of a suite of nature-based solutions to aid climate change mitigation. Secondly does the quantity of stored benthic blue carbon and functional biodiversity change with respect to trawling impact. Calibrated camera deployments perpendicular to seabed were made to get accurate replicate seabed images across 17 sites to calculate densities of epi-benthic functional groups. Three replicate Agassiz trawls were towed to collect specimens of zoobenthos which were also identified before measuring morphometrics, drying, weighing and ashing, and reweighing. Size spectra and carbon content of functional zoobenthic groups were calculated and analysed against physio-chemical factors measured at the time of collection. Scaling up from previous monohabitat benthic blue carbon assessments in the Norwegian Arctic would have massively underestimated quantity and ecosystem value. The Barents Sea is a highly productive and short-term predictable system that we would expect blue carbon storage to typically increase with changing Arctic conditions.
Górska B*¹, Molina EJ², Reiss H², Renaud PR³⁴, Sen A²⁴, Bluhm BA⁵, Włodarska-Kowalczuk M¹
¹Institute of Oceanology Polish Academy of Sciences, Sopot, Poland, ²Nord University, Bodø, Norway, ³Akvaplan-niva, Tromsø, Norway, ⁴University Centre in Svalbard, Longyearbyen, Norway, ⁵UiT The Arctic University of Norway, Tromsø, Norway
Climate warming is fastest and most intense in the Arctic regions, especially in the Barents Sea, which is influenced by both Arctic and Atlantic water masses. Large-scale simulations of global climate predict continuous increases in air and water temperature, leading to further reduction in ice-cover in the Arctic and results in cascading effects on the marine Arctic ecosystem. The initiation of ice melting is important for the timing, quality, and quantity of primary production and thus on the properties of organic matter reaching the seafloor. Changes in seasonality of organic matter pulses may led to changes in energy pathways and destabilization of the dynamics of food webs throughout the entire marine ecosystem, from pelagic to benthic compartments. The aim of our study is to identify seasonal and spatial variability of macrobenthic biomass size spectra, carbon demand, and respiration. Sampling and experiments were conducted in four seasons at seven stations in the Barents Sea and adjacent basin at depths ranging from 325 m to 3605 m and across gradients in ice extent and food supply to the seafloor and oceanographic regimes. The patterns of macrobenthic functioning and biomass partitioning among size classes are compared and assessed with respect to data on potential biotic and abiotic drivers. The basic metrics of functioning of macrobenthos in the ice-covered Arctic waters (north Barents Sea) were compared to those in ice-free regions at similar latitude/depth gradient (Greenland Sea) to explore the possible effects of environmental changes.
Jungblut S*¹, Brand M², Dorschner S³, Hagen W³
¹Marine Botany, University of Bremen, Bremen, Germany, ²Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Helgoland, Germany, ³Marine Zoology, University of Bremen, Bremen, Germany
The ongoing changes in the marine physical environment of the Arctic as well as the overall shift from sea- to land-terminating glaciers immensely impact shallow-water benthic communities, especially in fjords. The underwater light climate changes due to increasing sediment loads and a lower rate of scouring through icebergs causes less disturbances in shallow areas. In Kongsfjorden, Svalbard, the majority of kelp species (brown algae) is now found at shallow depths around 2.5 and 5 m, whereas the deeper areas around 10 and 15 m are dominated by red algae. We sampled the dominant grazers, the sea urchins Strongylocentrotus pallidus and S. droebachiensis, from the respective depth zones as well as the dominant macroalgae in summer 2021. Lipid and fatty acid analyses of gonad tissue revealed similarly high total lipid contents of 20-27% dry mass as well as similar fatty acid profiles for both species from different depths. Thus, the energy-storing capacities and feeding preferences of sea urchins do not vary with depth and hence different macroalgal assemblages. As very mobile opportunistic grazers, sea urchins of the genus Strongylocentrotus apparently migrate routinely up and down rocky bottom slopes while foraging, which leads to similar dietary compositions, even if the grazers were sampled in different macroalgae assemblages. Furthermore, this illustrates that Arctic sea urchins are relatively independent from the ongoing changes in the depth distributions of macroalgae.
Bernardo CP*¹, Pecuchet L¹, Primicerio R¹, Dolgov AV²³⁴, Fossheim M⁵, Husson B⁶, Santos J¹
¹UiT The Arctic University of Norway, Tromsø, Norway, ²PINRO Polar Branch of Russian Research Institute of Fisheries and Oceanography Murmansk, Murmansk, Russia, ³MSTU Murmansk State Technical University, Murmansk, Russia, ⁴TGU Tomsk State University, Tomsk, Russia, ⁵Institute of Marine Research, Tromsø, Norway, ⁶Institute of Marine Research, Bergen, Norway
In the Arctic, rapid warming causes large shifts in fish distributions. Which and how species are redistributing is related to their life-history traits. Previous studies have analyzed fish species range-shift according to few life-history traits, often considered separately. However, a more promising approach addresses multiple traits jointly to identify and characterize systematic changes. Following the equilibrium-periodic-opportunistic (EPO) life-history strategy framework, we aim to (i) describe how the Barents Sea fish species are positioned along the EPO continuum and whether their position can be related to other attributes (biogeography, feeding ecology, environmental preferences), and (ii) analyze the climate-driven spatiotemporal variation in fish community composition in terms of their life-history strategies (2004-2017). We used Archetype analysis to categorize the species within the three strategies based on their life-history traits. In contrast with other species pools, which are distributed between the opportunistic and periodic strategies, many fish species are distributed along the opportunistic-equilibrium axis in the Barents Sea. The equilibrium strategists were mostly generalist species at higher trophic levels, found in the western deep regions. The periodic strategists were boreal species with a generalist diet found in southern warmer areas. The opportunistic strategists were mostly Arctic or Arctic-boreal species with a specialist diet and low trophic level, found in the northern cold and ice-covered waters. In the central Barents Sea, where ice coverage has been declining and sea temperature has increased, the proportion of periodic species increased. In the Northeast, the proportion of opportunistic species remained stable, suggesting the presence of a cold Arctic water refuge. Equilibrium species increased eastward towards shallower waters. The fast warming of the Arctic has benefited periodic fish strategists, which are targeted by fisheries, over opportunistic species. The documented zoogeographic changes in life-history composition invite careful consideration in climate adaptation of management plans.
Dijkstra J*¹², Schott L¹³, Thomsen N⁴, Lutier M⁵, Søreide J²
¹The University of Amsterdam, Amsterdam, The Netherlands, ²UNIS - The University Centre in Svalbard, Longyearbyen, Svalbard, Norway, ³Freie Universitet Berlin, Berlin, Germany, ⁴Scottish Association for Marine Science, Oban UK, ⁵University of Oslo, Oslo, Norway
Calanus glacialis is the dominating copepod species in the Arctic food web, accounting for up to 80% of the zooplankton biomass. Before the winter period C. glacialis builds up lipid reserves, allowing them to spend the winter near the ocean floor in a state of diapause, only resurfacing again in spring to feed and reproduce. The effects of ocean warming and acidification on C. glacialis during their overwintering period are unknown. In the present study C. glacialis individuals were exposed to four different acidification and warming scenarios for a period of 53 days. In this period the developmental stage, mortality, lipid content and respiration were monitored. Higher temperatures led to earlier higher oxygen consumption, earlier maturation of the individuals and higher mortality. These changes can lead to mismatch scenario and will likely negatively impact this key species reproductive success with possible cascading effects on the entire Arctic marine ecosystem.
Castro de la Guardia L*¹, Hernández Fariñas T², Marchese C³⁴, Amargant-Arumí M⁵, Myers PG⁶, Bélanger S⁷, Assmy P¹, Gradinger RR⁵, Duarte P¹
¹Norwegian Polar Institute, Tromsø, Norway, ²Ifremer, Port-en-Bessin, France, ³University of British Columbia, Vancouver, Canada, ⁴University of Victoria, Victoria Island, Canada, ⁵UiT The Arctic University of Norway, Tromsø, Norway, ⁶University of Alberta, Edmonton, Canada, ⁷Université Québec á Rimouski, Rimouski, Canada
The Barents Sea is a highly productive marginal shelf sea of the Arctic Ocean, where sea ice, Atlantic Water and Arctic Water create a heterogenous marine environment. We combined in situ measurements, remote sensing, and model simulations to estimate the primary production of phytoplankton in the Barents Sea (1980-2021). A biogeographical analysis based on phytoplankton chlorophyll-a identified three distinct oceanic regions: Arctic, Subarctic, and Atlantic. Long-term time-series of NPP and environmental characteristics highlighted the start of a warm regime in the NW Barents Sea around 2004, triggered by a pulse of Atlantic Water. This shifted the dynamics of phytoplankton growth limitation in the Atlantic and Subarctic subregions, decreasing temperature limitation and increasing the relative importance of light and nutrient limitation, which in the Atlantic subregion resulted in a step-like increase in net primary production. We identified photosynthetically available radiation and mixing layer depth as important physical predictors of net primary production in spring and autumn, respectively. Finally, the regional and seasonal multi-source estimates within the NW Barents Sea suggest that total net primary production in the study region ranged from 15 Tg C y^-1 in the Arctic to 48 Tg C y^-1 in the Atlantic subregion. We estimated that roughly 90 Tg C y^-1 of primary production are required to sustain three of the most commonly harvested fish species north of 62 °N, highlighting the importance of allochthonous primary production in the NW Barents Sea for the sustainability of commercial fisheries.
Saubrekka K*¹, Vader L², Supraha L¹, Andersen T¹, Edvardsen B¹
¹University of Oslo, Oslo, Norway, ²The University Centre in Svalbard (UNIS), Svalbard, Norway
Protists have various crucial roles in the marine ecosystems and in a rapid changing Arctic it is important to address who´s there, when and where, for future management and research of the northern Barents Sea. The main objective in this study is to describe and compare the composition of the protist community in sea ice and pelagic habitats of samples collected along a S-N transect in the northern Barents Sea during in August 2018 with low sea-ice extent and 2019 with sea-ice extent high. By using metabarcoding targeting the 18S rRNA gene we revealed 3682 unique Amplicon sequence variants (ASV), a proxy for a species. The data shows a clear separation of ASV composition in the ice- and pelagic habitats. The pelagic community showed interannual differences along the sampling transect. In the year 2018 the community was dominated by dinoflagellates and nano- and pico-plankton such as Micromonas polaris. In the year 2019 a community with more centric diatoms was observed at station in the ice edge. Members of the class Chrysophyceae dominated in the melt ponds, whereas the community composition within the ice (dominated by dinoflagellates and pennate diatoms) changed from homogeneous to heterogeneous with increased ice cores thickness. Right below the ice other dinoflagellates ASVs were dominating, together with Phaeocystis. These results indicates that protist communities are distinct and specialized on habitat. With further ocean warming the pelagic community could shift towards smaller flagellates and thinning of the sea ice may result in loss of habitat niches diversity.
Marquardt M*¹, Goraguer L¹², Assmy P², Bluhm BA¹, Patrohay E¹, Aaboe S³, Down EJ³, Edvardsen B⁴, Smola Z⁵, Tatarek A⁵, Wiktor JM⁵, Gradinger R¹
¹UiT The Arctic University of Norway, Tromsø, Norway, ²Norwegian Polar Institute, Tromsø, Norway, ³Norwegian Meteorological Institute, Tromsø, Norway, ⁴University of Oslo, Oslo, Norway, ⁵Institute of Oceanology, Polish Academy of Sciences, Sopot, Poland
The rapid decline of Arctic sea-ice including that in the Barents Sea makes understanding sympagic biology an urgent task. Seasonal ice sampling (2019-2022) as part of the Nansen Legacy project focused on ice biota composition and abundance in the bottom 30cm of Barents Sea ice in relation to ice properties. In December and May we sampled growing first-year ice, while in July and August melting, older sea ice dominated, overall agreeing with ice trajectories. Abiotic ice conditions and Chla varied strongly seasonally, while POC values were unexpectedly homogenous. Low ice biota abundances in March could be related to late ice formation resulting in a short time for biota to build up biomass. Pennate diatoms dominated the bottom ice algal communities in all seasons, with highest biomass in May. Outside May, small-sized flagellates were co-dominant. Overall, ice meiofauna was comprised of harpacticoid copepods, copepod nauplii and rotifers, foraminiferans and highly abundant ciliates. While melting ice had released ice algal biomass in July, abundance of secondary producers remained high, indicating different life history traits. Unexpectedly abundant communities occurred in December, further strengthened the notion of an active biota in the dark Arctic winter. The data demonstrated a strong and partly unexpected seasonality in the ice biota, indicating that changing timing of ice formation and melt will significantly impact composition and phenology of sympagic communities.
Isaksen K*¹, Nordli ع, Køltzow MA¹, Aaboe S², Gjelten HM¹, Mezghani A¹, Eastwood S¹, Førland E¹, Benestad RE¹, Hanssen-Bauer I¹
¹Norwegian Meteorological Institute, Oslo, Norway, ²Norwegian Meteorological Institute, Tromsø, Norway
The first automatic weather stations were established in the early 1990s in eastern and northern Svalbard. At the time, real time data were used in weather forecasting and for rescue missions. However, the initial recorded data were not stored in any databases and have not previously been available for scientific analysis. This new dataset documents the surface air temperature (SAT) development in the north and east that remained unexplored until now. Here, we present updated surface air temperature data to the year 2023 to study the recent warming and its spatial and temporal variability in Svalbard, and evaluate how well the most recent European Climate Medium Weather Forecast reanalysis data set (ERA5) and the recently released high-resolution Copernicus Arctic Regional ReAnalysis (CARRA) describe SAT-climatology and trends. We find an unprecedented warming rate of more than 2.5 °C per decade in northeastern Svalbard, with a high increase in autumn and winter, compared to other seasons. The observed temperature increase is in good agreement with the reanalyses. However, compared to ERA5, CARRA shows larger regional SAT trends and more spatial details. The warming is faster than hitherto known in this region and its spatial structure is primarily consistent with reductions in sea ice cover. The recent warming was punctuated by an increasing intensity of abrupt warming events, with far reaching regional effects related to e.g., extremes in heavy rainfall during winter.
Aaboe S*¹, Isaksen K², Lind S³
¹Norwegian Meteorological Institute, Tromsø, Norway, ²Norwegian Meteorological Institute, Oslo, Norway, ³Norwegian Polar Institute, Tromsø, Norway
Arctic climate change shows severe warming and declining sea ice. The Barents Sea stands out as a significant hotspot for the most dramatic sea-ice loss, with an annual warming rate being twice the Arctic's average. The Barents Sea warming pattern is highly consistent with the reduction in the sea ice. In the western Barents Sea (which more or less has become ice-free), the temperature trends no longer increase, while the warming trends continue to intensify in the east where the sea ice is still dense but melting at a high pace. The reduced ice cover has a crucial role in destabilising the ocean’s upper layer stratification. With a weakened stratification, increased heat flux from the Atlantic Water towards the surface may prevent or postpone the sea ice from forming in autumn. More open water in autumn and winter allows the warmer sea surface to interact with the cold air above, raising the air temperatures. This demonstrates how the coupling between the atmosphere, ice, and ocean has contributed to the amplifying of recent warming in this region. This contribution presents recent findings of the exceptional changes in sea ice and warming in the Barents Sea over the past four decades, combining remotely-sensed data on sea ice and sea surface temperature, and observations of surface air temperature and oceanographic in-situ temperature and salinity.
Eldevik T¹, Steel M², Smedsrud LH*¹, Årthun M¹, Onarheim I³, Dodd P⁴, Muilwijk M⁴
¹University of Bergen, Bergen, Norway, ²University of Washington, Seattle, USA, ³Equinor, Bergen, Norway, ⁴Norwegian Polar Institute, Tromsø, Norway
What sets the position of the ice edge downstream from Fram Strait? The answer involves a competition between warm Atlantic Water entering the Arctic Ocean and cold sea ice flowing out in the opposite direction, both of which are under the influence of atmospheric surface heat fluxes. In this study, we build on earlier work on this subject by using new in situ and satellite observations as well as long oceanographic time series maintained well south of Fram Strait. We also introduce a simple analytical model that includes the ocean salt balance to constrain the problem, using observed salinity profiles. We find that a high percent of interannual variability in the ice edge position can be simply explained by the upstream temperature of the Norwegian Atlantic Current one year in advance.
Curtis PE*¹, Timmermans M-L¹, Yang A¹
¹Department of Earth and Planetary Sciences, Yale University, New Haven, United States
Future regional and global climate change is tightly coupled to the fate of sea ice in the Arctic’s Canada Basin. Rates of sea ice growth and melt are highly sensitive to relatively small upward fluxes of this stored ocean heat towards the base of sea ice. Crucially, stored ocean heat in the warm Pacific-origin waters of the Canada Basin halocline has more than doubled over the last three decades. Recent studies have further evidenced several critical trends in the Canada Basin’s upper ocean halocline: a deepening of the mixed layer, a transition towards weaker stratification at the base of the mixed layer, and a changing mechanical energy input to the upper ocean. An essential motivation thus remains to better understand the mechanisms leading to the vertical transport of stored ocean heat within the seasonally complex Canada Basin halocline, and how these mechanisms will influence sea ice cover over the coming years to decades. In this study, we use Canada Basin water-column observations from the Ice-Tethered program to better quantify heat transports from two principal mechanisms: i) slow vertical diffusion and ii) wind-driven mixing. We combine the observational results with a numerical simulation approach which we use to diagnose the types of stratified shear-driven instabilities at the base of the mixed layer. Then, we compare the magnitude of vertical heat transport through wind-driven instabilities to estimates of the slow vertical diffusion of heat.
Mehling O*¹, Bellomo K¹², von Hardenberg J¹²
¹Politecnico di Torino, Turin, Italy, ²Institute of Atmospheric Sciences and Climate (CNR-ISAC), Turin, Italy
Freshwater export through the Arctic Ocean gateways can have a strong influence on variations of the Atlantic Meridional Overturning Circulation (AMOC) on decadal timescales, as evidenced by the Great Salinity Anomalies of the 20th century. In turn, the AMOC can also influence Arctic Ocean freshwater content, for example by driving increased ocean heat transport into the high latitudes which leads to increased Arctic sea ice melt. From both mechanisms combined, a coupled Arctic Ocean–North Atlantic mode of variability can emerge on multi-decadal to centennial timescales, as first proposed by Jungclaus et al. in 2005 and recently identified as the driver of strong centennial-scale AMOC variability in two CMIP6 models. However, to our knowledge no systematic multi-model assessment of AMOC or Arctic Ocean variability on (multi-)centennial timescales has been conducted so far. Here, we investigate the co-variability of AMOC strength and Arctic Ocean freshwater content on centennial timescales in the CMIP6 ensemble of long pre-industrial control simulations. Our results show that Arctic Ocean freshwater content likely acts as a driver of significant centennial-scale AMOC variability in several CMIP6 models which all use the NEMO ocean component, and that the freshwater anomalies can persist within the central Arctic Ocean for several decades. We discuss the implications for modeled Arctic Ocean variability in past, present and future climates.
Rose SK*¹, Andersen OB¹
¹DTU Space - National Space Institute, Kgs. Lyngby, Denmark
This study focuses on the sea level changes from radar satellite altimetry. Recent advancements in satellite altimetry have significantly improved our ability to observe and analyze climate-related phenomena in greater detail. Here, we present a comprehensive and uninterrupted 30-year time series of Arctic Ocean sea-level measurements, spanning from 1991 with the ERS-1 satellite to 2021 with the CryoSat-2 satellite. Our analysis primarily concentrates on the remarkably dynamic Arctic environment, with a particular emphasis on the pronounced changes observed during the most recent decade in comparison to the preceding 30 years of altimetric measurements. To achieve this, we employ a case study approach, examining the Beaufort Gyre region, the Russian Shelf area, and investigating the general circulation patterns of the Arctic Ocean. The sea-level dataset utilized in this research is part of the European Space Agency (ESA) Climate Change Initiative (CCI) Sea level initiative and has been updated with enhanced CryoSat processing, utilizing the ESA G-POD SARvatore Data Repository. Overall, this study sheds light on the substantial alterations occurring in the Arctic region due to climate change. By leveraging a comprehensive sea-level dataset and employing advanced satellite altimetry techniques, our research elucidates the key drivers of these changes, offering valuable insights into the complex dynamics of the Arctic Ocean system.
Müller F*¹, Pisareva M¹, Hart-Davis M¹, Dettmering D¹, Schwatke C¹, Passaro M¹, Seitz F¹
¹Deutsches Geodätisches Forschungsinstitut, Technical University of Munich, Munich, Germany
The Arctic Ocean is very sensitive to climate change. Its effects are seen in reduced sea ice cover, rising sea level and changes in ocean circulation. Satellite altimetry has allowed these changes to be accurately observed for about 30 years by steadily improving the determination of sea surface height (SSH) in the ice-covered ocean. This contribution presents 3 examples of how satellite altimetry can help provide an improved understanding of physical processes in the Arctic Ocean. The presence of sea ice requires special classification and retracking algorithms that make it possible to distinguish between radar observations from water or ice as well as to provide reliable ranges between the satellite and the sea surface. Here, it is shown how satellite altimetry data can be used to detect open water based on an automatic radar echo classification. Besides the computation of accurate SSH, the monitoring of ocean tides by altimeter satellites is of great interest to generate improved tidal corrections for sea level determination, but also to better assess the effects of tides on circulation. Therefore, recent results of the expansion of the ocean tide model EOT20 to the Arctic Ocean are shown. Finally, a combination strategy is presented to combine altimetry-derived SSH with simulated water heights to obtain spatiotemporally consistent representation of the circulation, even in sea ice covered areas. Results of this approach are shown for the Chukchi and northern Nordic Seas.
Boutin G¹, Ólason E¹*, Rampal P², Regan H¹, Lique C³, Talandier C³, Brodeau L², Ricker R⁴
¹Nansen Environmental and Remote Sensing Center, Bergen, Norway, ²CNRS, Univ. Grenoble, Institut de Géophysique de l'Environnement, Grenoble, France, ³Univ. Brest, CNRS, IRD, Ifremer, Laboratoire d’Océanographie Physique et Spatiale (LOPS), Brest, France, ⁴NORCE, Tromsø, Norway
Email corresponding author: einar.olason@nersc.no
Sea ice is a critical component of the Earth’s climate system as it modulates the energy exchanges and associated feedback processes at the air-sea interface in polar regions. These exchanges strongly depend on openings in the sea-ice cover, which are caused by fine-scale sea-ice deformations. Still, the importance of these processes remains poorly understood as most numerical models struggle to represent these deformations without using costly horizontal resolutions (~1 km). Here, we present results from a 12 km resolution ocean-sea-ice coupled model involving the ocean component of NEMO and the sea-ice model neXtSIM. This is the first coupled model that uses brittle rheology to represent the mechanical behaviour of sea ice. Using this rheology enables the reproduction of the observed characteristics and complexity of fine-scale sea ice deformations with little dependency on the mesh resolution. We investigate the sea ice mass balance of the model for the period 2000-2018. After carefully evaluating the modelled sea ice against available observations (extent, drift, volume, deformations, etc.), we assess the relative contribution of dynamical vs thermodynamic processes to the sea-ice mass balance in the Arctic Basin. We find a good agreement with ice volume changes estimated from the ESA CCI sea-ice thickness dataset in the winter, demonstrating the ability of brittle rheologies to produce a reasonable sea ice mass balance over long periods. Using the unique capability of the model to reproduce sea-ice deformations, we estimate the contribution of leads and polynyas to winter ice production. This contribution adds up from 25% to 35% of the total ice growth in pack ice in winter, showing a significant increase over the 18 years covered by the model simulation. This coupled framework opens new opportunities to understand and quantify the interplay between small-scale sea-ice dynamics and ocean properties that cannot be inferred from satellite observations.
Crews L*¹, Lee C¹, Rainville L¹, Brenner S²
¹University of Washington Applied Physics Laboratory, Seattle, United States, ²Brown University, Providence, United States
Fluctuating wind stresses excite energetic currents in the mixed layer that oscillate at frequencies near the local inertial frequency. In polar regions, sea ice is fundamental to momentum transfer between the atmosphere and the ocean, and internal ice stresses can interrupt this momentum transfer. Despite the historical paradigm of inertial oscillation damping by a strong and consolidated ice pack, the impact of sea ice dynamics and characteristics on ocean near-inertial energy remains equivocal. Here we use observations collected by a Beaufort Sea mooring array during a February 2019 storm to show how a fractured ice pack with a recent history of lead formation permits inertial oscillation development whereas an intact ice pack selectively filters out high frequency motions. Prior to the storm, winds pushed the ice pack against the coast and opened a network of leads that traversed some of the study area. Following lead formation, a low pressure system excited ice and ocean near-inertial velocities that varied in accord with the history of lead activity, with stronger inertial oscillations at the fractured sites. Leads, which can extend hundreds of kilometers from coastal promontories into the ice pack, therefore link ocean dynamics to distant coastal boundaries. Consequently, efforts to predict future wintertime inertial motions in the Arctic may benefit from ongoing efforts to accurately model lead formation and floe size distribution.
Zapponini M*¹, Gößling HF¹
¹Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), Bremerhaven, Germany
Surface air temperatures are rising faster in the Arctic than in any other region of the planet. However, the upper troposphere is not warming at the same speed, resulting in a weakening of the atmospheric stratification. Using reanalysis and CMIP6 model data, we show that an increased efficiency of tropospheric vertical transfer of horizontal momentum causes a winter strengthening of near-surface winds over the Arctic Ocean. For the winter season of the period 1950 - 2020, ERA5 and CMIP6 climate models show an approximately linear relationship between the decreasing atmospheric stability, measured through the 10 m – 850 hPa temperature gradient, and the increasing downward momentum transfer efficiency, measured through the 10 m/850 hPa wind speed ratio. In contrast, Arctic summers tend to change in the opposite direction. Here, as long as some sea-ice remains, the surface is constrained to the freezing temperature whereas the upper troposphere warms due to warmer air being advected from lower latitudes. The summer weakening of the downward momentum transfer efficiency is weaker than the winter decrease, and more pronounced in ERA5 than in CMIP6 data. However, the models show that the rate at which the winter momentum transfer efficiency shifts towards summer-like conditions is accelerating and projected to continue, resulting in almost no seasonality of the Arctic atmospheric stability and momentum transfer efficiency remaining by the end of the 21st century.
All Nansen Legacy researchers still actively involved in the project should purchase their travel as they have done previously (follow guidelines at their own institution) and apply for travel reimbursements by their respective partner institutions. The institutions will then send a compiled claim to the project office.
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