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Sea trials to test size selectivity equipment in trawls are often limited in time because they are costly, and the results can be influenced by multiple factors that are often overlooked. In the Barents Sea gadoid trawl fishery, the use of a size sorting grid in front of the codend is compulsory. The flexigrid, a netting section containing two flexible grids, is the most widely used grid section in this fishery. However, earlier selectivity studies with this device have shown inconclusive results. It has been speculated that the differences observed resulted from the difference in age and usage of the grid sections in the studies compared. To reveal whether potential changes in the device construction over time can lead to differences in size selection properties, we performed comparative fishing trials where we compared a brand new flexigrid section and a well-used flexigrid section used continuously by a commercial trawler for approximately four years. The results showed that the new flexigrid released significantly more cod below ~60 cm than the used flexigrid. However, when the grids were fished with a subsequent diamond mesh codend, there was no difference in the overall selectivity of the two gears, meaning that the size selectivity in the codend compensates for the potential reduction in selectivity performance of the grids. This study shows the importance of considering the age and earlier use of size selection devices like sorting grids before they are compared with other devices, as their size selection properties can change significantly over time and with use. [ABSTRACT FROM AUTHOR]

Based on a long-term dataset of species composition and infestation levels of associated organisms on the invasive Barents Sea red king crab, a multivariate analysis was conducted to determine the contributions of biotic and abiotic factors to the fouling community structure. Results indicate that host size and exoskeleton age were the most significant factors for diversity indices and infestation intensity. Abiotic factors played a lesser role in the formation of fouling communities. Temperature conditions during the mass molting periods were found to have significant effects, apparently acting as a trigger for the primary settlement of crab shells by benthic organisms. Our data not only provide new insights into the formation of fouling communities of decapod crustaceans, but also provide valuable information for further studies on the adaptation process of the red crab to the conditions of the Barents Sea. [ABSTRACT FROM AUTHOR]

Sea ice edges play an essential role in the Earth's climate and weather systems through active atmosphere‐ice‐ocean interactions. However, our understanding of the observed positions of sea ice edges remains limited. The present study investigated, on seasonal and longer timescales from 1979 to 2023, the variability in sea ice edge positions in the Barents and Greenland Seas. We objectively derived the positions of sea ice edges based on satellite‐derived sea ice concentration gridded on a 25‐km resolution. In the Barents Sea, warm, narrow currents flow eastward along the northern and southern rims of the Central Bank. Until the mid‐2000s, sea ice edges fluctuated between these currents interannually during December–June, depending on the surface wind direction. However, after the mid‐2000s, the sea ice edges were mostly positioned near the northern current or farther to the north. Furthermore, sea ice edges during October–March were identified frequently near the warm current flowing along the continental slope in the northern Barents Sea after the mid‐2000s. In the Greenland Sea, sea ice edges were typically positioned near the East Greenland Current (EGC) throughout the year until 2006. However, sea ice edges in summer were located far to the west of the EGC after 2006. These observations suggest that the geographical relationship between sea ice edges and ocean currents has changed due to global warming. Plain Language Summary: Sea ice edges in the Arctic play an important role in the Earth's climate system. They can strengthen atmospheric cyclones and vertical motion in the atmosphere and the ocean in the Arctic by inducing intense heat and moisture releases from the ocean to the atmosphere. Furthermore, they could exert distinct impacts on global‐scale atmosphere and ocean circulations. Therefore, a deeper understanding of the geographical positions of sea ice edges is essential for elucidating the climate system. This study investigated the sea ice edge positions in the Barents and Greenland Seas using satellite observations from 1979 to 2023. Sea ice edges rapidly advance southward during winter. Until the mid‐2000s, sea ice edges were frequently identified along warm ocean currents in the Barents and Greenland Seas because warm currents obstruct further sea ice edge advances. However, sea ice edges have shifted far to the north of warm ocean currents after the mid‐2000s in association with the recent shrinking in sea ice extent due to global warming. The change in sea ice edge positions might have affected the atmosphere and ocean circulations globally, which should be addressed in future studies. Key Points: In the central Barents Sea, sea ice edge positions fluctuated in winter until the mid‐2000s but have lately fixed along a warm currentSince the mid‐2000s, sea ice edges have been frequently identified along the continental slope in the northern Barents Sea in winterUntil 2006, sea ice edges in the Greenland Sea were located at the East Greenland Current, but they shifted far west after 2006 in summer [ABSTRACT FROM AUTHOR]

The formation of dense Brine‐enriched Shelf Water (BSW) in Storfjorden is analyzed during Winter 2016–2017 from mooring observations, a polynya model nudged to satellite observations, and an original BSW production model. The ice season was two months shorter than average, yet 44.2 km3 ${\text{km}}^{3}$ of sea ice were formed, in line with estimates for the period preceding the atlantification of the Barents Sea in the mid‐2000s: A thinner, more fragile ice may favor polynya openings and frazil ice production. A saline specimen of BSW was produced in large volumes, corresponding to an annual mean transport of 0.042 Sv, larger than previous estimates. The important production is due to the preconditioning of the polynya with a more saline source water, exceeding the pre‐2005 values by 0.37. The BSW overflow was observed on the West Spitsbergen shelf slope from hydrographic sections down to 750 m, thus entering the Norwegian Sea Deep Water layer. Its core temperature was about 1° $1{}^{\circ}$C warmer than the pre‐2005 values owing to the entrainment of a warmer water in Storfjordrenna, suggesting that a part of the excess surface heat of the Barents Sea could be exported into the deep ocean. Overall our results suggest that dense water formation in the Storfjorden polynya may not, at least for now, be hampered by the atlantification of the Barents Sea, and perhaps even temporarily favored by the more saline source water. Anomalous atmospheric warming during the Winter‐Spring may however disrupt the production, as was observed 1 year before. Plain Language Summary: Sea‐ice extent has strongly declined in the Barents Sea since the mid‐2000s. The sea has also become warmer and saltier, a phenomenon referred to as atlantification. This raises concerns regarding the future of dense water production in coastal polynyas, an essential cog in the climate machine. Polynyas work as ice factories, releasing large quantities of salt in the ocean, which can lead surface waters to cascade into the deep ocean when dense enough. We analyze dense water production in Winter 2016–2017 in the Storfjorden polynya (Svalbard) from a time series of hydrographic observations and an ice production model. Despite a shorter freezing season, the ice production and salt release remained average, while preconditioning with a more saline source water permitted the production of a particularly saline dense water in large volumes. The dense bottom plume was observed to sink into the deep ocean. It was warmer than in the past, suggesting that part of the excess surface heat could be stored at depth. Overall our results suggest that dense water production may not, at least for now, be hampered by the atlantification of the Barents Sea, unless strongly anomalous winter atmospheric warming disrupts ice production, as observed 1 year before. Key Points: A simple model to estimate the production of dense water from hydrographic time series and salt forcing is developedPreconditioning of the polynya with saltier source water promoted the production of dense Brine‐enriched Shelf Water (BSW) in 2017 despite an average ice productionThe BSW overflow was observed to sink down to the Deep Water layer: It was warmer than in observations prior to the atlantification [ABSTRACT FROM AUTHOR]

Marine invertebrate habitats are experiencing warming, and oceanic carbon dioxide levels are on the rise. These changes result in shifts in species distributions. Monitoring and understanding these shifts provides vital information because each species plays a unique ecological role, and the human utilization of marine species is intrinsically linked to their geographic locations. Here, we examine distribution shifts of marine invertebrates in the Barents Sea since pre-1900. Using data from the Global Biodiversity Information Facility, we analyzed species occurrences across warm, cold and mixed temperature zones, distinguishing between benthic and pelagic taxa. Our findings indicate community shifts in each of five separated time periods, with the most pronounced shifts occurring after 1980 in the cold and mixed zones, and earlier in the warm zone. The significant biogeographical changes at the community scale occurred both in benthic and pelagic realms, yet with differing trajectories in the period past 2000, and largely coincided with increased Atlantic Water inflow and reduced ice cover. Several invertebrate taxa exhibited a northward movement, falling into two categories: species migrating into the Barents Sea from the Norwegian mainland shelf, and those relocating from the southern Barents Sea to areas with mixed and colder temperatures. Some of these species may serve as indicator species for monitoring ecosystem and community change. The study highlights the importance of long-term datasets in quantifying community distribution shifts and understanding their ecological impacts. [ABSTRACT FROM AUTHOR]

The modern Arctic is characterized by a decreased ice cover and significant interannual variability. However, the reaction of the High Arctic ecosystem to such changes is still being determined. This study tested the hypothesis that the key drivers of changes in phytoplankton are the position and intensity of Atlantic water (AW) flow. The research was conducted in August 2017 in the northern part of the Barents Sea and in August 2020 in the Nansen Basin. In 2017, the Nansen Basin was ice covered; in 2020, the Nansen Basin had open water up to 83° N. A comparative analysis of phytoplankton composition, dominant species, abundance, and biomass at the boundary of the ice and open water in the marginal ice zone (MIZ) as well as in the open water was carried out. The total biomass of the phytoplankton in the photic layer of MIZ is one and a half orders of magnitude greater than in open water. In 2017, the maximum abundance and biomass of phytoplankton in the MIZ were formed by cold-water diatoms Thalassiosira spp. (T. gravida, T. rotula, T. hyalina, T. nordenskioeldii), associated with first-year ice. They were confined to the northern shelf of the Barents Sea. The large diatom Porosira glacialis grew intensively in the MIZ of the Nansen Basin under the influence of Atlantic waters. A seasonal thermocline, above which the concentrations of silicon and nitrogen were close to zero, and deep maxima of phytoplankton abundance and biomass were recorded in the open water. Atlantic species—haptophyte Phaeocystis pouchettii and large diatom Eucampia groenlandica—formed these maxima. P. pouchettii were observed in the Nansen Basin in the Atlantic water (AW) flow (2020); E. groenlandica demonstrated a high biomass (4848 mg m−3, 179.5 mg C m−3) in the Franz Victoria trench (2017). Such high biomass of this species in the northern Barents Sea shelf has not been observed before. The variability of the phytoplankton composition and biomass in the Franz Victoria trench and in the Nansen Basin is related to the intensity of the AW, which comes from the Frame Strait as the Atlantic Water Boundary Current. [ABSTRACT FROM AUTHOR]

Sea trials to test size selectivity equipment in trawls are often limited in time because they are costly, and the results can be influenced by multiple factors that are often overlooked. In the Barents Sea gadoid trawl fishery, the use of a size sorting grid in front of the codend is compulsory. The flexigrid, a netting section containing two flexible grids, is the most widely used grid section in this fishery. However, earlier selectivity studies with this device have shown inconclusive results. It has been speculated that the differences observed resulted from the difference in age and usage of the grid sections in the studies compared. To reveal whether potential changes in the device construction over time can lead to differences in size selection properties, we performed comparative fishing trials where we compared a brand new flexigrid section and a well-used flexigrid section used continuously by a commercial trawler for approximately four years. The results showed that the new flexigrid released significantly more cod below ∼60 cm than the used flexigrid. However, when the grids were fished with a subsequent diamond mesh codend, there was no difference in the overall selectivity of the two gears, meaning that the size selectivity in the codend compensates for the potential reduction in selectivity performance of the grids. This study shows the importance of considering the age and earlier use of size selection devices like sorting grids before they are compared with other devices, as their size selection properties can change significantly over time and with use.

Sea urchin roe is a high-quality product in terms of its nutritional value, valuable biochemical composition, and acquired taste. Urchin stocks, however, have been overfished worldwide and new candidates for commercial harvesting and aquaculture are required to satisfy the demand from the expanding market. The green sea urchin Strongylocentrotus droebachiensis from Russian waters of the Barents Sea may be considered a new source for potential consumers. We summarized available information regarding distribution patterns, feeding, reproduction, and growth as well as studies focused on farming of this species to assess the fishery and aquaculture potential of the area. This species is abundant in the coastal zone where it is commonly associated with laminarian kelp. The brown algae Saccharina latissima is the primary diet for S. droebachiensis but it also consumes animal foods. Red king crabs are the main predators for sea urchins but they do not significantly affect the S. droebachiensis population. A spawning peak of S.droebachiensis is registered in March–April. Green sea urchins reach a commercial size of 50 mm diameter at age 6 and the estimated stock of commercial urchins is 50,000–81,000 t. The most promising sites for harvesting are Varanger-fjord and Bolshoy Oleniy Island plus Porchnikha Bay. The best harvesting seasons are February–March and September–October. Sea-based rearing systems appear to be the most suitable approach for sea urchin aquaculture based on grow-out of adult animals fed on algal or mixed diets. [ABSTRACT FROM AUTHOR]

The article presents a comparative analysis of the fecundity of the Barents Sea red king crab, its size composition, and size at 50% maturity during the period of its expansion and acclimatization and at present during intense fishing. In addition, based on the published literature data, differences are estimated between the above parameters of Barents Sea individuals and individuals from the crab's natural habitat. In 2019–2022, the Barents Sea red king crab showed a trend of decreasing its fecundity compared to the period of active acclimatization (1995–2003) before commercial exploitation started. In recent years, changes in the reproductive parameters of the Barents Sea red king crab population have increased the similarity of these characteristics to those for native populations from the Pacific region that began to be actively exploited in the early 20th century. [ABSTRACT FROM AUTHOR]

The article presents analyses of the dynamics of injuries of the snow crab opilio in catches taken during surveys in 2008–2022, as well as data collected by observers in the fishery for this species in the Russian part of the Barents Sea in 2014–2022. The average proportion of injured crabs in catches taken during research surveys increased from 5–11% in 2008–2010 to 45% in 2022. The increase in the number of injured individuals in catches is higher for large males. The modeling results showed that the increased proportion of injured individuals in the period preceding commercial exploitation is associated with an increase in intrapopulation interactions, while during active commercial exploitation, it is associated with fishing pressure on the population, when some individuals, including crabs injured during capture, are returned to the sea after processing. [ABSTRACT FROM AUTHOR]

The Barents Sea is one of the main pathways for warm and saline Atlantic Water (AW) entering the Arctic Ocean. It is an important region where water mass transformation and dense‐water production contribute to the Atlantic meridional overturning circulation. Here, we present data from three cruises and nine glider missions conducted between 2019 and 2022 in the northwestern Barents Sea, and compare them with historical data collected between 1950 and 2009. We present circulation pathways, hydrography and volume transports of Atlantic‐ and Arctic‐origin waters. Our observations show that 0.9 ± 0.1 Sv (1 Sv = 106 m3 s−1) of Atlantic‐origin water reaches the Polar Front (PF) region before splitting into several branches and eventually subducting beneath Polar Water (PW). The amount of Atlantic‐origin water stored in the Olga Basin north of the PF is controlled by the density difference between AW and PW, and reached a maximum in the 90s when PW was particularly fresh. In the recent period from 2019 to 2022, the inflow of AW into the Barents Sea freshened by up to 0.1 g kg−1 compared to previous decades. This led to a reduction in the production of dense water, an increased temperature gradient across the PF, and a reduced poleward transport of warm water. Plain Language Summary: Warm and salty water from the Atlantic Ocean flows through the Barents Sea on its path toward the Arctic Ocean. It undergoes cooling and freshening due to interactions with the surrounding water and the atmosphere, and eventually encounters much colder and fresher Polar Water, creating a distinct boundary known as the Polar Front. We conducted several research missions in the northwestern Barents Sea between 2019 and 2022 and compared the data to historical records collected between 1950 and 2009. The cooled Atlantic Water sinks beneath the Polar Water before continuing toward the Arctic Ocean. In recent decades, the temperature of the Atlantic Water inflow has increased. The warm Atlantic Water can be traced below the Polar Front, leading to an increase in the temperature of the deeper waters north of the front. However, the amount of Atlantic Water north of the front is regulated by the density difference between the Atlantic Water and Polar Water. In the recent period of 2019–2022, the Atlantic Water reaching the front has become less salty. As a result, there is a reduced flow of warm water moving northward beneath the Polar Water and a larger temperature difference across the Polar Front. Key Points: Circulation pathways and volume transport of Atlantic‐ and Arctic‐origin waters in the northwestern Barents Sea are detailedAt the Polar Front density differences between these waters create a geostrophic current that governs warm water flow into the Arctic domainOver recent decades Atlantic Water warmed and freshened, reducing its density difference with the Polar Water and inflow across the front [ABSTRACT FROM AUTHOR]

Source‐to‐sink dynamics are subjected to complex interactions between erosion, sediment transfer and deposition, particularly in an evolving tectonic and climatic setting. Here we use stratigraphic forward modelling (SFM) to predict the basin‐fill architecture of a multi‐source‐to‐sink system based on a state‐of‐the‐art numerical approach. The modelling processes consider key source‐to‐sink parameters such as water discharge, sediment load and grain size to simulate various sedimentary processes and transport mechanisms reflecting the dynamic interplay between erosion in the catchment area, subsidence, deposition and filling of the basin. The Cenozoic succession along the SW Barents Shelf margin provides a key area to examine controls on source‐to‐sink systems along a transform margin that developed during the opening of the North Atlantic when Greenland and Eurasian plates were separated (ca. 55 Ma onwards). Moreover, the gradual cooling which culminated in major glaciations in the northern hemisphere during the Quaternary (ca. 2.7 Ma), has affected the spatio‐temporal evolution of the sediment routing along the western Barents Shelf margin. This study aims to characterize the relative importance of different source areas within the source‐to‐sink framework through SFM. In the early Eocene, the SW Barents Shelf experienced a relatively equal sediment delivery from three principal source areas: (i) Greenland to the north, (ii) the Stappen High to the east, representing a local source terrain, and (iii) a major southern source (Fennoscandia). In the middle Eocene, our best‐fit modelling scenario suggests that the northern and the local eastern sources dominated over the southern source, collectively supplying large amounts of sand into the basin as evidenced by the submarine fans in Sørvestsnaget Basin. In the Oligocene (ca. 33 Ma) and Miocene (ca. 23 Ma), significant amounts of sediments were sourced from the east due to shelf‐wide uplift. Finally, this study highlights the dynamic nature and controls of sediment transfer in multi‐source‐to‐sink systems and demonstrates the potential of SFM to unravel tectonic and climatic signals in the stratigraphic record. [ABSTRACT FROM AUTHOR]

Arctic phytoplankton are highly sensitive to seawater physical and chemical conditions, especially in the context of rapid climate change and sea ice loss. We studied the spatial and seasonal distributions of diatoms, dinoflagellates and coccolithophores, and clarified their associations with light, temperature and nutrients in the western Barents Sea in late summer 2017, and winter, spring and early summer 2018. Diatoms, composed mainly of Chaetoceros, Fragilariopsis and Thalassiosira, bloomed in spring at the southern border of the marginal ice zone with mean abundance of 1.1 × 106 cells L−1 and biomass of 119.5 µg C L−1, and were observed to follow the retreat of sea ice in the Arctic water to the north at the shelf break near Nansen Basin, contributing to the progression of the summer situation. Dinoflagellates flourished in surface waters south of Svalbard in summer, with maxima of 2.2 × 105 cells L−1 and 78.2 µg C L−1. High abundances and calcite mass of coccolithophores were detected in the southern Barents Sea and southwest of Svalbard in summer, with maxima of 3.3 × 105 cells L−1 and 4.7 µg C L−1. Two distinct phytoplankton assemblages, closely linked with Atlantic water and Arctic water, were geographically separated by the Polar Front in two summers, with a percent similarity below 11.9%, suggesting great influence of the two water masses on large-scale distributions of phytoplankton. Redundancy analysis revealed that temperature was one of the most important factors in shaping the seasonal distributions of diatoms, while irradiance showed positive correlation with dominant dinoflagellates of each season. From the perspectives of phytoplankton composition and carbon biomass, our findings highlight the governing effect of physical seawater conditions on driving seasonal patterns of phytoplankton biogeography, as well as the pivotal role of nutrients in supporting the phytoplankton growing seasons in the western Barents Sea. [ABSTRACT FROM AUTHOR]

Microorganisms capable of degrading hydrocarbons are regular components of natural microbial communities and play an important role in self-purification of marine environments from oil contamination. High-throughput sequencing of the 16S rRNA gene V4 variable region was used to analyze microbial communities of the Barents and Pechora seas and of the microcosms with a spectrum of hydrocarbon substrates: oil, n-nonane, n-undecane, and phenanthrene. The Barents Sea communities of hydrocarbon-oxidizing microorganisms were characterized by the predominance of the genera Pseudoalteromonas, Pseudomonas, Porticoccus, and Oleispira, while those of the Pechora Sea contained members of the genera Rhodococcus, Dietzia, Sphingorhabdus, and Hyphomonas. Pure cultures of these microorganisms were shown to utilize the major oil hydrocarbons: n-alkanes, cycloalkanes, and aromatic compounds. [ABSTRACT FROM AUTHOR]

Arctic amplification caused by the rapid loss of Arctic sea ice has emerged as a crucial factor in affecting global weather and climate in recent decades. However, it remains unknown whether this rapid loss has exerted a specific impact on tropical cyclone (TC) activity over the eastern North Pacific (ENP). Here, we examine the influence of springtime (March–May) sea ice concentration (SIC) in the Barents Sea (SIC-BS), a key region for Arctic SIC changes, on TC genesis frequency over the ENP during the TC season (June–October) during 1970–2021. Results show that the reduced SIC-BS was favorable for more TC geneses over the ENP in terms of interannual variability. Further analyses based on dynamical diagnosis demonstrate that the rapid loss of SIC-BS leads to an upward transport of turbulent heat fluxes, facilitating the propagation of the Rossby wave train from the Barents Sea to the ENP via the western United States. This process subsequently leads to increase in upper-level divergence, mid-level upward motion, and lower-level vorticity, thereby accounting for the formation of more TCs over the ENP. This mechanism is further substantiated by the Coupled Model Intercomparison Project phase 6 (CMIP6). These results not only establish a possible connection between Arctic sea ice and tropical climate, but also hold important implications for understanding future changes in TC activity over the ENP. [ABSTRACT FROM AUTHOR]

A striking recurrent feature of winter climate variability is the "warm Arctic-cold Eurasia" (WACE) pattern of opposite sign anomalies of surface air temperature (SAT) in the Barents Sea region and midlatitude Eurasia. Its origins and mechanisms are hotly debated, and its predictability remains unknown. This study investigates statistical relationships of the winter WACE dipole with concurrent anomalies of atmospheric circulation and oceanic precursors during the era of satellite observations. The results reveal a high potential for seasonal predictability of not only the WACE dipole but also several related indicators of winter climate variability, including the Arctic and Eurasian SAT anomalies. During subperiods of extreme covariability between the Arctic and Eurasian SATs around the early 1980s and late 2000s, most of the WACE variability is explained by ocean temperature and surface turbulent heat flux anomalies in the Barents Sea region during the preceding months. Anomalies in summer Atlantic water temperature (AWT) and autumnal sea surface temperature (SST) in this region explain about 70–80% of the variance of the following winter WACE variability during all events of strong Arctic-Eurasian SAT covariability. Analysis of SST variability in the Arctic-North Atlantic region suggests that the winter WACE link to the summer AWT anomalies reflects an atmospheric response to a large-scale surface reemergence of ocean temperature anomalies. However, this linkage had been robust only until the early 2000s. Since then, the winter WACE variability has been strongly related to autumnal SST anomalies in the Barents Sea region and the North Pacific. [ABSTRACT FROM AUTHOR]

Integrated marine studies were carried out by researchers at the Murmansk Marine Biological Institute, Russian Academy of Sciences, during an August 2023 cruise on the R/V Dalnie Zelentsy within the national project "Science and Universities." The studies included CTD sampling; hydrological, hydrochemical, hydrobiological, ichthyological, and radioecologic studies; and observations of marine birds and mammals. The outcome of the cruise was new data on the reference state of the eastern Barents Sea ecosystem. [ABSTRACT FROM AUTHOR]

Pink salmon is currently the main species for the anadromous fish fishery in the north of the European part of Russia. Upward trends were observed in this species returns and catches in odd years of the 2013–2021 in the regions of North-West Russia (Murmansk Region, Republic of Karelia, Arkhangelsk Region, and Nenets Autonomous Region) that allowed to increase the annual catch limit to 1,619 t in 2023. However, despite this optimistic forecast, the factual total landing of pink salmon in this part of Russia in 2023 was 203.26 t by all fishing gears (12.55 % of the quo- ta). Oceanographic conditions (SST) along the migration routes of pink salmon were rather favorable both in the White Sea and North Atlantic, so reasons of weak returns are vague. Unpredictability of pink salmon returns is well known for the main habitat of the species — the North-West Pacific, so this phenomenon has occurred in the European waters, too, in 2023.

We discovered seafloor features such as bacterial mats and carbonate crusts typical for active methane seeps on the continental slope southwest of Svalbard. These features are associated with two main northwest-southeast trending morphological structures that are oriented parallel to the regional continental slope. Both structures occur at c. 800 m water depth, at the boundary between the Storfjorden trough mouth fan to the south and the Hornsund trough mouth fan to the north, which suggests a loading related fluid seepage. The main structure displays depressions and ridges forming a crater in its center. Other occurring features include small sediment mounds, domes often covered by bacterial mats, and hummocky seafloor colonized by siboglinid tubeworms. Free gas bubbles were spotted close to the centre and plumes along the rims of the structure. Thick carbonate crusts indicate a long seepage history in the center of the structure and on top of the ridges. The sources of the seeps are likely to be Miocene old organic-rich deposits, or Paleocene hydrocarbon reservoirs. [ABSTRACT FROM AUTHOR]

Although the summers of 2021 and 2022 are both in the two successive La Niña decaying stages and under the same climate background of negative Pacific Decadal Oscillation (PDO) phase and global warming trend, they exhibit significantly different and even opposite precipitation patterns in the Yangtze River Valley (YRV) as well as in the Indian monsoon region (IMR). In contrast to the abundant precipitation and lower temperature in the YRV in summer 2021, in summer 2022 the YRV experiences severe drought and extremely high temperatures, which is also accompanied by Mega‐floods in the IMR. This study identifies the joint influence of sea surface temperature anomalies (SSTAs) in Niño4 and Barents Sea (BS) regions as the underlying cause for the contrast YRV precipitation anomalies in the summers of 2021 and 2022. Specifically, the cold SSTAs in both Niño4 and BS regions in summer 2021 favor stronger and southward shifted western North Pacific subtropical high (WNPSH), leading to more precipitation in the YRV, which is however generally reversed but more intense in summer 2022 because of the synergistic effect of cold Niño4 and warm BS SSTAs. Moreover, the induced extreme precipitation in the IMR in summer 2022, which is absent in summer 2021 due to the offsetting effect of cold SSTAs in both Niño4 and BS regions, in turn further strengthens the anomalous atmospheric circulations via its released large diabatic heating and serves as a relay pathway for the dramatic drought and heat wave in the YRV. Plain Language Summary: The El Niño‐Southern Oscillation (ENSO) is known to be the most significant interannual signal and one of the major factors for summer precipitation anomaly in East Asia. Nevertheless, the two summers of 2021 and 2022 are characterized by almost opposite precipitation patterns in the Yangtze River Valley (YRV) even though they are both in the two successive La Niña decaying stages. Our study demonstrates that except for the cold sea surface temperature anomalies (SSTAs) with obvious differences in both intensity and position in Niño4 region, the opposite SSTAs in Barents Sea region may play a dominant role in determining the strong contrast precipitation patterns in the YRV as well as in the Indian monsoon region (IMR). As the result of the synergistic effect of cold Niño4 and warm BS, the extreme IMR precipitation also serves as a relay pathway for the dramatic drought and heat wave in the YRV in summer 2022. It suggests that to clearly understand and accurately predict the climate anomalies in East Asia should consider the mid‐high latitude signals besides the tropical ENSO signal, especially in the context of global warming when the signals and influences from the mid‐high latitudes are becoming more and more prominent. Key Points: The two La Niña decaying summers in 2021 and 2022 see nearly opposite precipitation patterns in Yangtze River valleySynergistic effect of cold Niño4 region and warm Barents Sea is the essential cause for the extreme summer drought in Yangtze River valleyIndian monsoon precipitation plays a relaying role in linking the SST forcing and the Yangtze River valley precipitation via teleconnection [ABSTRACT FROM AUTHOR]

Zooplankton in the Barents Sea has been monitored by the Institute of Marine Research in Norway on autumn cruises since 1986, using a standardized procedure with determination of dry weight biomass in three size fractions following splitting of the sample in two halves. Along with summer data for the early 1980s, we can now describe changes of zooplankton biomass over four decades. The biomass of the central Barents Sea has fluctuated inversely with collapses and recoveries of the Barents Sea capelin stock, which is a major planktivore. Zooplankton biomass in the central Barents Sea was low in 1983 and 1984, driven by low abundance of Calanus finmarchicus , followed by a pronounced peak in 1987 associated with a "first" collapse of the capelin stock. Biomass showed another pronounced peak in 1994, driven by the small size fraction and interpreted to reflect an advective signal from the adjacent Norwegian Sea. In the two most recent decades, there have been divergent trends, with a relatively high biomass in the inflowing Atlantic water, reflecting a second summer generation of C. finmarchicus , and decreased biomass in the central area, reflecting a lower abundance of Calanus glacialis driven by a combined effect of capelin predation and climate. [ABSTRACT FROM AUTHOR]

Variations in the surface chlorophyll a concentration (Chl-a) measured during 25 cruises conducted from 1984 to 2020 were investigated in the Barents Sea and adjacent Svalbard waters. Seasonal maps of the mean annual Chl-a estimations were created for the Barents Sea. Significant seasonal and temporal variations of Chl-a were found in different water masses. The surface Chl-a content reached a maximum in the spring (46% of the annual estimation). In the summer, it tended to decrease accounting for 28% of the total annual value, while in the autumn and winter, Chl-a was found to be 21 and 5% of the total annual stock, respectively. Atlantic Water and Arctic Water had the highest contribution to the total annual Chl-a biomass. In Arctic Water, peaks of the Chl-a concentrations were registered in spring and these decreased in summer and autumn. The summer season was the most productive period in Atlantic Water. The Chl-a dynamics and distribution in relation to climatic factors were investigated. Application of generalized linear and non-linear models to predict Chl-a variations showed the great significance of the indices associated with the global atmospheric circulation, mean annual temperature, and salinity anomalies, as well as the extent of ice in the Barents Sea. [ABSTRACT FROM AUTHOR]

This study presents the results of a 2D numerical basin and petroleum systems model of the Olga Basin in the NW Barents Sea offshore northern Norway, a frontier exploration area in which there are abundant seafloor oil and gas seepages. The effects of Pleistocene ice sheet advances on rock properties and subsurface fluid migration in this area, and on seafloor hydrocarbon seepage, are not well understood. The 2D numerical model takes account of recurrent ice advances and retreats, together with related erosional and temperature effects, and investigates the influence of these parameters on fluid migration. Model results show that Pleistocene glaciations reduced the temperature in the sedimentary succession in the Olga Basin by up to 20 °C, for example in the uppermost Cretaceous and Jurassic sediments which underlie the seafloor down to a depth of 0.5 to 1 km. The decrease in temperature was in general predominantly related to the intensity of glacial erosion, which was set in this study to a depth of 600 m based on previous studies. Hydrocarbon fluids expelled from potential thermogenic source rocks of Carboniferous to Triassic ages on the SW margin of the Olga Basin migrated to the seafloor through permeable carrier beds. However, fluid migration to the surface in the NE of the study area took place along fault conduits. In a closed fault model scenario, only 0.3 Mt of hydrocarbons are modelled to have migrated along the 0.5 km wide model section; in a second scenario with partially open faults, about 22 Mt of hydrocarbons, representing about 11% of the total hydrocarbons generated by potential thermogenic source rocks in the study area, were lost to the surface during the Pleistocene. The potential for microbial methane generation in the Olga Basin was limited both during the Pleistocene and at the present day due to the significant reduction in temperature during glacial episodes, and due to the intense glacial‐related erosion of the Mesozoic to Cenozoic stratigraphy. During glacial stages, the gas hydrate stability zone beneath the ice sheet is modelled to have extended to a depth of up to 900 m for a pure methane composition, and to a depth of up to 1100 m for a possible thermogenic‐sourced mixed gas composition of 90% methane, 7% propane and 3% ethane. Gas hydrates with this mixed composition are modelled to have been stable in the Olga Basin during the last three glacial advances and into the present. These modelling results provide an insight into the key factors controlling the migration and surface leakage of hydrocarbon fluids in the Olga Basin region, and into the effects of glaciations on rock properties in a glaciated basin. [ABSTRACT FROM AUTHOR]

The hydrocarbon seepage chronology during deglaciation across the formerly glaciated Barents Sea was established using uranium-thorium (U-Th) dating of seep carbonates. Seep carbonates were sampled with remotely operated vehicles (ROV) from the seafloor at three active hydrocarbon seeps (water depth 156-383 m), located in the north-west (Storfjordrenna), north-central (Storbanken High), and south-west (Loppa High) Barents Sea. Overall, the U-Th dates range from 13.5 to 1.2 thousand years (ka) before present, indicating episodic seep carbonate formation since the late Pleistocene throughout the Holocene. The new U-Th dates indicate protracted post-glacial gas seepage, congruent with previously published seep carbonate ages from the south-west Barents Sea. Gas hydrate dissociation and associated seep carbonate formation occurred at Storfjordrenna between ≈6 and 1.2 ka, and around 13.5 and 6 ka at Storbanken. Early and late Holocene seep carbonate ages from Loppa High support post-glacial seismic activity as potential seepage trigger mechanism. [ABSTRACT FROM AUTHOR]

The recent, rapid spreading of non‐native pink salmon Oncorhynchus gorbuscha in the North Atlantic area has raised concerns about their possible negative impacts on native salmonid species. Potential interactions include competition for food resources during the short freshwater phase of juvenile O. gorbuscha, but little is known about their feeding behavior in the newly occupied North Atlantic rivers. Using stable isotope and stomach content analyses, patterns of freshwater feeding of non‐native O. gorbuscha fry were studied in a large Fennoscandian river, the Teno, that discharges to the Barents Sea. Changes in stable isotope values (δ13C, δ15N, δ34S) and stomach contents from the period of emergence (April to mid‐May) to estuarine entry (late May/June) were examined and provided both temporally integrated and short‐term indicators of freshwater feeding dependency. In addition, the occurrence of juvenile O. gorbuscha and changes in their length and weight during their emergence/migration period were investigated. Juvenile O. gorbuscha were at the spawning grounds from April through to mid‐May with abundance peaking in mid‐May. Fish moved to the estuary by late May and their abundance decreased toward June, and their body size increased concurrently. Stomach analyses indicated no feeding activity in April–early May in the spawning areas, but the stomach fullness indices increased markedly in fish sampled in the estuary in May and June. The most important prey items in stomachs were Chironomidae and Ephemeroptera larvae. Significant changes in all analysed stable isotopes were detected among sample periods, with a peak in mid‐May and June showing significantly lower values than other sample periods. A change from the higher values reflective of parental marine feeding to the lower values reflective of freshwater feeding indicated active in‐river feeding by juveniles during the study period. The documented active freshwater feeding of non‐native juvenile O. gorbuscha suggests potential resource competition with native fluvial fishes, particularly salmonids. [ABSTRACT FROM AUTHOR]

The Upper Jurassic-Lower Cretaceous sedimentary rocks in the Eastern Barents Sea Basin are up to 2 km thick and represent one of the least studied Arctic intervals. Here, for the first time, we present a detailed analysis of 43,000 km of 2D seismic profiles, as well as well-log and core data from 24 offshore wells with the aim to create a comprehensive sequence stratigraphic framework that can be integrated with the rest of the basin. Results show that (1) seven third-order sequences and five types of clinoforms can be identified based on integrated seismic and well data. The age of each sequence was established based on published biostratigraphic investigations along with new dinocyst interpretations included in this study; (2) the deep marine basin was gradually filled with sediments coming from north, east and south as a response to HALIP, Canada Basin opening and Cimmerian uplift of Novaya Zemlya, and was preserved only in the southwestern part of the Barents Sea Basin at the end of Early Cretaceous and (3) both Eastern Barents Sea and West Siberia Basin share similarities in sedimentary environments and tectonic setting, though the spatial distribution of clastic reservoirs in Upper Jurassic and Lower Cretaceous mega-sequence heavily depends on the source areas that require more provenance focused research. The results presented here can be used in further regional exploration in the area and to better understand the geodynamic evolution of the Greater Barents Sea Basin. [ABSTRACT FROM AUTHOR]

The study analyzes polycyclic aromatic hydrocarbons (PAHs) isolated from bottom sediments of the Barents and Norwegian seas (2019–2021 cruises of the R/V Akademik Mstislav Keldysh). Elevated PAH concentrations (up to 16 900 ng/g) are recorded in the coastal region of the Svalbard archipelago, and low ones, in the Greenland Basin and the eponymous ridge (up to 80 ng/g), as well as on the continental slope of the Barents Sea (up to 240 ng/g on average). Among cata-condensed PAHs, 2–3 ring polyarenes are the most common: naphthalene, 1- and 2-methylnaphthalenes, and phenanthrene, while among peri-condensed PAHs, 4–6 ring polyarenes are the most typical: fluoranthene, pyrene, and benz(a)anthracene. Anthropogenic sources in the bottom sediments of the study area are of subordinate importance compared to their natural input from the sedimentary stratum with fluid fluxes and erosion. [ABSTRACT FROM AUTHOR]

In situ temperature measurements along the Kola Transect for 1993–2019 are compared to climate indices for the North Atlantic, developed by the authors in earlier works. Five climate indices are considered: PC1, PC2, NAT, NAT1, and NAT2. It is shown that the temperature time series along the Kola Transect correlate well with climate indices PC2, as well as NAT1 and NAT2, which are responsible for warming processes in the cold North European Basin and cooling processes in the warm region south of Iceland. The correlation coefficients reach 0.80. At the same time, there is a low correlation between the temperature along the Kola Transect and the PC1 and NAT indices, which represent the volume flux of water entering the North European Basin from the Atlantic. This implies that the thermal state of the Atlantic waters entering the Barents Sea and the water temperature along the Kola Meridian are determined by the thermal state of the waters rather than the volume flux of Atlantic waters. A high consistency is found between the in situ measurements along the Kola Transect and the corresponding data from the GLORYS12V1 global ocean reanalysis. It is shown that the northern boundary of the Coastal Branch of the Murmansk Current can reach 71.5°–72° N. [ABSTRACT FROM AUTHOR]

The Arctic experiences remarkable changes in environmental parameters that affect fluctuations in the surface energy budget, including radiation and sensible and latent heat fluxes. Cold air masses and cloud transformations during marine cold air outbreaks (MCAOs) substantially influence the radiative fluxes, thereby shaping the link between large-scale dynamics, sea ice conditions, and the surface energy budget. In this study, we investigate various cloud characteristics during intense MCAOs over the Barents Sea from 2000 to 2018 using satellite data. We identify 72 intense MCAO events that propagated southward using reanalysis data of the surface temperature and potential temperature at the 800 hPa level. We investigate the macro- and microphysical parameters and radiative properties of clouds within selected MCAOs, their dependence on sea ice concentration, and their initial air mass properties using satellite data. A significant increase in low-level clouds near the ice edge (up to +25% anomalies) and a smooth transition to upper-level clouds is revealed. The total cloud top height during intense MCAOs is generally 500–700 m lower than under neutral conditions. MCAOs induce a positive net cloud radiative effect, which peaks at +20 W m−2 (100 km from the ice edge) and gradually decreases towards the continent (−2.3 W m−2 per 100 km). Our study provides evidence for the importance of changes in the cloud radiative effect within MCAOs, which should be accurately simulated in regional and global climate models. [ABSTRACT FROM AUTHOR]

Patterns of the distribution of rare earth elements (REEs) in natural objects are important geochemical indicators of the state of the environment. Data on the REE contents in fucus algae from different horizons of the littoral of the Barents Sea are presented for the first time. The behavior of REEs in natural processes is controlled by the solubility of their compounds, their capability of complex formation, and the tetrad-effect of fractionation. Natural factors determining REE migration in the sediment–water–macrophytes system are discussed. [ABSTRACT FROM AUTHOR]

Changes in the masses of icebergs due to deterioration processes affect the drift of icebergs and should be taken into account when assessing iceberg risks in the areas of offshore development. In 2022 and 2023, eight laboratory experiments were carried out in the wave tank of the University Centre in Svalbard to study the melting of icebergs in sea water under calm and rough conditions. In the experiments, the water temperatures varied from 0   ℃ to 2.2   ℃ . Cylindrical iceberg models were made from columnar ice cores with a diameter of 24 cm. In one experiment, the iceberg model was protected on the sides with plastic fencing to investigate the iceberg's protection from melting when towed to deliver fresh water. The iceberg masses, water temperatures, and ice temperatures were measured in the experiments. The water velocity near the iceberg models was measured with an acoustic Doppler velocimeter. During the experiments, time-lapse cameras were used to describe the shapes and measure the vertical dimensions of the icebergs. Using experimental data, we calculated the horizontal dimensions of icebergs, latent heat fluxes, conductive heat fluxes inside the iceberg models, and turbulent heat fluxes in water as a function of time. We discovered the influence of surface waves and water mixing on the melt rates and found a significant reduction in the melt rates due to the lateral protection of the iceberg model using a plastic barrier. Based on the experimental data obtained, the ratio of the rates of lateral and bottom melting of the icebergs and lateral melting of the icebergs under wave conditions was parametrized depending on the wave frequency. [ABSTRACT FROM AUTHOR]

Marine invertebrate habitats are experiencing warming, and oceanic carbon dioxide levels are on the rise. These changes result in shifts in species distributions. Monitoring and understanding these shifts provides vital information because each species plays a unique ecological role, and the human utilization of marine species is intrinsically linked to their geographic locations. Here, we examine distribution shifts of marine invertebrates in the Barents Sea since pre-1900. Using data from the Global Biodiversity Information Facility, we analyzed species occurrences across warm, cold and mixed temperature zones, distinguishing between benthic and pelagic taxa. Our findings indicate community shifts in each of five separated time periods, with the most pronounced shifts occurring after 1980 in the cold and mixed zones, and earlier in the warm zone. The significant biogeographical changes at the community scale occurred both in benthic and pelagic realms, yet with differing trajectories in the period past 2000, and largely coincided with increased Atlantic Water inflow and reduced ice cover. Several invertebrate taxa exhibited a northward movement, falling into two categories: species migrating into the Barents Sea from the Norwegian mainland shelf, and those relocating from the southern Barents Sea to areas with mixed and colder temperatures. Some of these species may serve as indicator species for monitoring ecosystem and community change. The study highlights the importance of long-term datasets in quantifying community distribution shifts and understanding their ecological impacts.

Variability of the Pechora Sea ice cover and the Barents Sea surface temperature during the season from October to June in 2002–2022 (except the season of 2011/2012) was studied on the basis of satellite observations and reanalysis ERA5. Influence of the sea surface temperature on the ice cover was also analyzed but without considering the other hydrometeorological parameters. Areas of the sea ice cover characteristics were calculated using data on the sea ice closeness obtained from the Advanced Microwave Scanning Radiometer 2 measurements. To analyze the variability of sea surface temperature, we used the average daily data of the European Centre for Medium-Range Weather Forecasts ERA5 reanalysis obtained by averaging hourly data. To study the spatial and temporal variability of sea ice cover and sea surface temperature, fields of daily averaged parameters were mapped. These maps and values of areas of the sea ice cover were analyzed. This made possible to reveal regularities of development of the sea ice processes in the Pechora Sea, to calculate the general trend of the sea ice area change over the considered period of time, and to divide the Barents Sea into four sectors with significantly different average values of the sea surface temperature: southwestern, northwestern, southeastern, northeastern ones. The seasonal and interannual variabilities of the Pechora Sea ice cover and the Barents Sea surface temperature were analyzed. To study the effect of sea surface temperature in different sectors of the Barents Sea on the sea ice area, the method of statistical analysis (Pearson’s linear correlation) was used for the monthly average data and the data, averaged over the sea ice season (from October to June) with different time lags. Significant correlation coefficients were obtained only for a two-month lag. With such a lag, high values of the inverse correlation coefficients were revealed between the sea surface temperature in the southwestern (up to –0.8) and northwestern (up to –0.6) sectors of the Barents Sea and sea ice area of the Pechora Sea, while in other sectors the correlation was significantly smaller or even below the significance level.

The development and operation of new oil fields on the Arctic shelf increases the risks of oil spills, which require the use of oil spill response tools and materials that are efficient in harsh climatic conditions. The question of actual efficiency of sorbents for reducing the level of oil pollution in the conditions of the Arctic and subarctic waters is relevant. The work is aimed at a comparative study of the efficiency of sorbents of mineral and organic origin used by coastal enterprises in the Kola Bay as well as a sorbent based on chitin in model systems simulating real conditions in sea waters. The characteristics of sorption agents were determined applying ASTM F716-18 procedure. Sorption capacity was evaluated in respect of ARCO grade oil, diesel fuel and marine oil. The efficiency of sorbents was estimated in model systems “sea water – oil” at water temperature corresponding to the average annual surface temperature in the Barents Sea. Actual data on sorption capacity of commercial sorbents “Lessorb”, “Novosorb”, a sorbent based on vermiculite and chitin sorbent in relation to potential pollutants of waters were obtained. The dynamics of sea water saturation with oil products at –0.5 (±1) and 10 (±1) °С was determined. It is shown that at higher temperature the concentration of oil products in sea water column (in the presence of an oil film on the surface) is on average four times higher than at low temperature. Kinetic dependences were obtained that describe the content of oil products in water column and near-surface layer of sea water in the presence of the studied sorbents at 5 (±1) °C, corresponding to the average annual temperature in the Kola Bay of the Barents Sea. A method is proposed for evaluating the efficiency of sorbents from the values of regression coefficients characterizing the dependence of oil products content in sea water on the character of sorbent and duration of its action.

The newly obtained results of the frequency-resonance (FR) technologies application for the study of the sources and processes of seeps and pockmarks formation in the Arctic Region (Norwegian, Barents Sea) and the North Sea are considered. The experimental study of the seepage processes' source formation was carried out using modified methods of the FR-processing, and decoding of satellite images and photographs with the vertical scanning of the cross-sections. The study results of the methane seeps and pockmarks fields show that the intensity and dynamics of their formation partly depend on the inflow of gas fluids from deep sources because of active degassing processes. The use of FR-sounding technologies allows us to remotely determine the spatial regularities of zones of intense gas emission formation and the geological sources of migration probable depth. The study of seep and pockmark field results confirms the significant, but insufficiently taken into account, the influence of crust-mantle gas fluids on the nature and degassing processes features in the structures of the continental margins. New results confirm the crust-mantle gas fluids influence on the nature and degassing processes features in the scan points of Polar marginal structures. These data are important arguments in favor of the "volcanic model" of various structural elements formation in this Region. The FR- technologies data also showed a possibility of seeps and pockmarks use as shallow and deep hydrocarbon field indicators in gas emission areas. These independent data can be used in modeling the deep lithosphere structure and possible mechanisms of abiogenic hydrocarbon formation in Arctic margin structures. We suppose that hydrocarbons through deep channels migrate (from 57 km deep) to the upper crustal horizons where can form hydrocarbon fields. During this migration, gas seeps and pockmarks are formed on the sea bottom and part of the gas can migrate into the atmosphere. Modern degassing centers' studies have confirmed the presence of zones of active migration of gases into the atmosphere, which is an important influencing factor in the dynamics of global climate change processes on Earth. The experience of FR- technologies used in the fields of methane seeps and pockmarks study found in the structures of the Arctic Polar seas showed versatility and the possibility of their use in the study of large gas emissions in structures of different regions.

The modern Arctic is characterized by a decreased ice cover and significant interannual variability. However, the reaction of the High Arctic ecosystem to such changes is still being determined. This study tested the hypothesis that the key drivers of changes in phytoplankton are the position and intensity of Atlantic water (AW) flow. The research was conducted in August 2017 in the northern part of the Barents Sea and in August 2020 in the Nansen Basin. In 2017, the Nansen Basin was ice covered; in 2020, the Nansen Basin had open water up to 83° N. A comparative analysis of phytoplankton composition, dominant species, abundance, and biomass at the boundary of the ice and open water in the marginal ice zone (MIZ) as well as in the open water was carried out. The total biomass of the phytoplankton in the photic layer of MIZ is one and a half orders of magnitude greater than in open water. In 2017, the maximum abundance and biomass of phytoplankton in the MIZ were formed by cold-water diatoms Thalassiosira spp. (T. gravida, T. rotula, T. hyalina, T. nordenskioeldii), associated with first-year ice. They were confined to the northern shelf of the Barents Sea. The large diatom Porosira glacialis grew intensively in the MIZ of the Nansen Basin under the influence of Atlantic waters. A seasonal thermocline, above which the concentrations of silicon and nitrogen were close to zero, and deep maxima of phytoplankton abundance and biomass were recorded in the open water. Atlantic species—haptophyte Phaeocystis pouchettii and large diatom Eucampia groenlandica—formed these maxima. P. pouchettii were observed in the Nansen Basin in the Atlantic water (AW) flow (2020); E. groenlandica demonstrated a high biomass (4848 mg m−3, 179.5 mg C m−3) in the Franz Victoria trench (2017). Such high biomass of this species in the northern Barents Sea shelf has not been observed before. The variability of the phytoplankton composition and biomass in the Franz Victoria trench and in the Nansen Basin is related to the intensity of the AW, which comes from the Frame Strait as the Atlantic Water Boundary Current.

Based on remote sensing data obtained by Sentinel-1A and Sentinel-1B satellites in 2016–2022 and the results of analysis of hydrocarbons (aliphatic—AHCs, and polycyclic aromatic—PAHs) in bottom sediments collected in 2019–2022, the nature of oil slicks in various areas of the Barents Sea has been established. It has been shown that the distribution of oil slicks in coastal areas is greatly influenced by anthropogenic hydrocarbon inflows (mainly from shipping), which is confirmed by elevated AHC concentrations in coastal sediments (up to 73 μg/g) and in the composition of Corg (up to 3.6%). In the central and northern regions of the sea (in particular, at coordinates 75.2°–75.3° N and 31.5°–31.8° E, station 7105), the grouping of oil slicks is due to natural oil and gas manifestations. This is confirmed by the anomalous concentration of PAHs in the lower horizons of the sediment column, as well as their composition (dominance of 2-methylnaphthalene, a marker of their oil genesis). At the same time, the proportion of light homologues in the composition of alkanes increased, which may indicate their formation in the sedimentary sequence. [ABSTRACT FROM AUTHOR]

This study analyzes seismicity within the shelf of the Barents Sea and the Knipovich and Gakkel ridges that surround it, and compares the spatial distribution of seismicity with the fault network as identified by seismic prospecting data. Kinematic characteristics have been obtained for the spatial migration of seismic activity. It is shown that the seismic events recorded by NORSAR, the Norwegian regional network, as occurring within the Russian part of the Barents Sea shelf make linear clusters along strike slip faults. The fault network displaces Mesozoic seismic sequences and emerges at the bottom surface by displacing Quaternary deposits. This clearly indicates a present-day age of the faults along which the linear clusters of low magnitude seismicity aligned. The computation of the total seismic moment in the space-time domain showed the presence of a seismic activity migration along short fault segments in the shelf at rates of 10.5 to 25.7 km/year. A burst of general activity in the shelf area beginning in 2012 could be noted. Comparison of the time-dependent evolution of seismic activity in the shelf to fragments of the Atlantic–Arctic Rift System suggests that the evolution is due to tectonic deformation waves that are initiated along the geodynamically active plate boundary and are propagating to the shelf at a rate of 20‒22 km/year. Another alternative, namely, that the rate of migration can reach 77 km/year, is less likely. The increase in the rate of seismic activity in the shelf after 2012 might be, not emission due to the excitation of a slow deformation wave, but rather resulted from direct triggering impact on the shelf by the Knipovich and Gakkel ridges. [ABSTRACT FROM AUTHOR]

Provenance study plays an important role in paleogeographic and tectonic reconstructions. Detrital zircons are commonly used to identify sediment provenance; however, a wide range of detrital zircon ages in clastic rock often represent a fingerprint of reworked older terrigenous successions rather than ages of magmatism and metamorphism in the provenance area. This study focuses on the provenance of detrital rutile grains in the Triassic–Jurassic sandstones from Franz Josef Land and shows the importance of multiproxy approaches for provenance studies. Trace element data demonstrate that most rutile grains were sourced from metapelitic rocks, with a subordinate population having a metamafic origin. The Zr-in-rutile thermometer and U-Pb geochronology suggest that detrital rutile grains were predominantly derived from rocks that underwent amphibolite facies metamorphism during the Paleozoic era, with a predominance of the Carboniferous–Permian ages. Therefore, we suggest that the provenance area for the studied sandstones on Franz Josef Land has a similar geological history to the Taimyr region and Severnaya Zemlya archipelago. We propose that this crustal domain extends across the Kara Sea and forms the basement to the north and east of FJL, representing a proximal provenance for the studied Mesozoic terrigenous rocks. This domain experienced both Middle–Late Ordovician and Carboniferous–Permian metamorphism. The comparison of U-Pb dating and the geochemistry of rutile, U-Th/He, and U-Pb dating of zircons showed that detrital rutiles are the powerful toll in provenance restoration and can give additional constrains when a provenance area locates within collisional-convergent settings. [ABSTRACT FROM AUTHOR]

The only large synanthropic colony of the common kittiwake Rissa tridactyla (Linnaeus, 1758), located within the city of Murmansk, has been described for the first time on the Russian coast of the Barents Sea. The data have been provided on the geographic location of the settlement, the number and spatial distribution of birds, and productivity. Some aspects of environmental conditions during the nesting period (food availability, predation, and anthropogenic disturbance) and their possible impact on reproduction are discussed. [ABSTRACT FROM AUTHOR]

Simple Summary: Seafood by-products contain a variety of valuable components, including bioactive peptides and essential fatty acids. The red king crab is a large, commercially important crustacean supporting profitable fisheries in the Barents Sea. In Norway, female red king crabs are included in the fishery. Large adult females carry egg masses, but red king crab eggs have not yet been studied for fatty acid content. In this paper, we provide information regarding the fatty acid profiles of red king crab eggs. We found a higher proportion of polyunsaturated fatty acids in comparison to saturated and monounsaturated fatty acids. Total pools of fatty acid did not differ significantly in terms of the stage of embryo development, female size, limb injury status, and habitat conditions. Individual comparisons, however, indicated significant differences for some fatty acids, providing evidence that they may play a role in physiological processes. Red king crab eggs may be considered a product with high nutritional value and are recommended for wide use in the food, pharmaceutical, and biomedical industries. The red king crab, Paralithodes camtschaticus, was introduced into the Barents Sea where, after a period of 30 years of adaptation, it has established a new population. This population has been commercially exploited over the past two decades, supporting profitable fisheries in both Russia and Norway. Biochemical studies aimed at assessing fatty acid profiles have been conducted, focusing primarily on the edible parts of red king crabs. Only recently have by-products been included in this research. Capture of female red king crabs is prohibited in Russia but is allowed in Norway. The fatty acids of the egg masses carried by these females have not yet been studied. To fill this knowledge gap, we assayed the fatty acid composition of eggs using gas–liquid chromatography. Our results showed a predominance of polyunsaturated fatty acids, while the concentrations of saturated and monounsaturated fatty acids were similar. Multivariate comparisons showed no significant differences in fatty acid profiles in terms of egg developmental stage (nauplius vs. metanauplius), habitat conditions (soft vs. hard bottoms), female size class, or number of autotomized limbs. However, individual comparisons showed some differences in fatty acids, the most important being the lower content of docosahexaenoic acid in eggs at the metanauplius stage compared to eggs at the nauplius stage, which is likely due to its essential role in the development of red king crab embryos. The total fatty acid content (53.94 mg g−1) was 2–87 times higher in eggs than in other red king crab tissues, confirming the critical role that fatty acids play in maintaining physiological processes during vitellogenesis. The high content of essential fatty acids and an optimal omega-3-to-omega-6 ratio (4.9) suggest that red king crab eggs are a good product for a healthy diet and a valuable source for extracting essential fatty acids. [ABSTRACT FROM AUTHOR]

Simple Summary: The adductor muscles of scallops are highly prized for their exceptional taste and nutritional value. Additionally, by-products of scallops show potential for the production of functional foods, animal feed, and nutraceuticals. To address the paucity of information regarding the amino acid composition of Iceland scallops from the coastal Barents Sea, we conducted biochemical analyses of various tissues from this species. Our findings revealed the highest contents of glycine and arginine, two amino acids widely implicated in the physiological processes of scallops worldwide. The consistency of amino acid composition across the muscle, gonad, and mantle tissues, as well as their lack of differentiation between male and female scallops, was noteworthy. A negative correlation was observed between the gonad index and amino acid contents in the muscle, while a positive relationship was found between muscle amino acid content and depth. Furthermore, amino acid contents in the mantle demonstrated a positive correlation with water temperature. Scallop by-products hold significant promise for the food and pharmaceutical industries. The Iceland scallop from the Barents Sea is a commercially important species with promising aquaculture potential, but information on the biochemical properties of its tissues is limited. Our analysis of the adductor muscle, gonad, and mantle of this bivalve mollusk from coastal waters provided insight into its amino acid composition. Biochemical analysis revealed predominant levels of glycine (11.8, 11.5, and 9.6 mg g−1, respectively) and arginine (11.2, 8.3, and 5.8 mg g−1, respectively). While multivariate comparisons did not reveal significant differences in amino acid composition between the tissues, single comparisons showed significantly higher levels of arginine and leucine in the adductor muscle compared to those of the mantle. The abundant presence of glycine and arginine underscores their importance in maintaining basic physiological processes, consistent with other scallop species. Redundancy analysis identified water depth and scallop gonad index as influential factors shaping the amino acid profile in the adductor muscle. In the case of the mantle, water temperature emerged as the main driver of amino acid content. Our results confirm the richness of essential amino acids in scallop by-products and highlight their potential for human consumption, production of feed ingredients for farmed animals, and nutraceuticals. [ABSTRACT FROM AUTHOR]

Simple Summary: Information on epibionts and symbionts of the introduced Barents Sea red king crab during the winter period is currently lacking. To address this gap, we examined the species composition and infestation indices of epibionts on this host in the northern part of Kola Bay in November. Our findings indicate a higher infestation rate of barnacles and amphipods during the winter season compared to the summer. In contrast, infestation rates of other species remained low during winter, reflecting seasonal fluctuations in both the size distribution of red king crabs and prevailing temperature conditions. Our research provides novel data on the growth patterns of commonly associated organisms, which could prove invaluable in determining the age of red king crabs in the Barents Sea. The species composition of epibiotic communities on red king crab was investigated in Sayda Bay, Russia, during November of 2015 and 2016. The community consisted of 12 species in total. Among epibionts, the barnacle Balanus crenatus was most prevalent (67.0%), while the amphipod Ischyrocerus commensalis was the most frequent symbiont (77.3%). Infestation levels in May–June 2005 and September 2004 were higher, as a larger proportion of small crabs without fouling species were present during those seasons. The lower infestation intensities recorded for other common associated organisms during winter can be attributed to their increased mortality due to unfavorable temperature conditions. The localization of epibionts and symbionts were related to larval settlement patterns of attached species and feeding behavior of mobile species. Monthly growth increments for I. commensalis and B. crenatus were estimated at 2 mm in body length and 1.35 mm in basal diameter, respectively. Size-at-age data for epibionts can aid in the age determination of large male crabs that may skip an annual molt. [ABSTRACT FROM AUTHOR]

Features of the dynamics of numbers of the common guillemot (Uria aalge) and Brünnich's guillemot (U. lomvia) have been analyzed based on long-term monitoring data obtained from colonies from the southern Barents Sea coast. Since the 2000s, the numbers of guillemots in colonies have been shown to decrease gradually. In 2019–2021, most of the guillemot colonies of the southern Barents Sea coast disappeared. Two factors have been found to affect the dynamics of guillemot colonies in the last few decades within their winter–spring range indirectly, through changes in the availability of the main food resources: the fishing industry and change in oceanographic conditions. The former affects only the birds from southwestern Barents Sea colonies, but the latter is relevant within the whole winter–spring area from the Barents Sea to the western areas of the North Atlantic and affects the guillemots' living conditions in the most critical periods of their life. In the future this may cause significant changes in the location of guillemot colonies in the southern Barents Sea. [ABSTRACT FROM AUTHOR]

The study analyzes polycyclic aromatic hydrocarbons (PAHs) isolated from bottom sediments of the Barents and Norwegian seas (2019–2021 cruises of the R/V Akademik Mstislav Keldysh). Elevated PAH concentrations (up to 16 900 ng/g) are recorded in the coastal region of the Svalbard archipelago, and low ones, in the Greenland Basin and the eponymous ridge (up to 80 ng/g), as well as on the continental slope of the Barents Sea (up to 240 ng/g on average). Among cata-condensed PAHs, 2–3 ring polyarenes are the most common: naphthalene, 1- and 2-methylnaphthalenes, and phenanthrene, while among peri-condensed PAHs, 4–6 ring polyarenes are the most typical: fluoranthene, pyrene, and benz(a)anthracene. Anthropogenic sources in the bottom sediments of the study area are of subordinate importance compared to their natural input from the sedimentary stratum with fluid fluxes and erosion. [ABSTRACT FROM AUTHOR]

In situ temperature measurements along the Kola Transect for 1993–2019 are compared to climate indices for the North Atlantic, developed by the authors in earlier works. Five climate indices are considered: PC1, PC2, NAT, NAT1, and NAT2. It is shown that the temperature time series along the Kola Transect correlate well with climate indices PC2, as well as NAT1 and NAT2, which are responsible for warming processes in the cold North European Basin and cooling processes in the warm region south of Iceland. The correlation coefficients reach 0.80. At the same time, there is a low correlation between the temperature along the Kola Transect and the PC1 and NAT indices, which represent the volume flux of water entering the North European Basin from the Atlantic. This implies that the thermal state of the Atlantic waters entering the Barents Sea and the water temperature along the Kola Meridian are determined by the thermal state of the waters rather than the volume flux of Atlantic waters. A high consistency is found between the in situ measurements along the Kola Transect and the corresponding data from the GLORYS12V1 global ocean reanalysis. It is shown that the northern boundary of the Coastal Branch of the Murmansk Current can reach 71.5°–72° N. [ABSTRACT FROM AUTHOR]

High-performance sequencing of the 16S rRNA gene (V4 region) was used to reveal the most widespread groups of microorganisms in the bottom sediments of the Barents and Kara seas. In the Barents Sea, these were uncultured bacteria of the families Hyphomicrobiaceae, Anaerolineaceae, Desulfobulbaceae, and Desulfosarcinaceae (Sva0081 sediment group), actinobacteria of the genus Rhodococcus, and proteobacteria of the genus Woeseia. In the Kara Sea the most represented groups were uncultured bacteria of the order Sedimentisphaerales (the SG8-4 cluster, class Phycisphaerae, phylum Planсtomycetota), bacteria of the family Anaerolineaceae, the family Desulfosarcinaceae (the SEEP-SRB1 cluster), the deep phylogenetic cluster NB1-j, organotrophic proteobacteria of the genera Woeseia and Pseudomonas, and sulfate reducers of the genus Desulfatiglans. The patterns of microbial distribution were analyzed depending on the depth from the bottom surface and the presence of fluid discharge zones. It was found that according to analysis of the core microbiome, uncultured bacteria of the SG8-4 cluster and uncultured bacteria of the family Anaerolineaceae predominated in the methane discharge zones in the Barents and Kara seas. [ABSTRACT FROM AUTHOR]

Dramatic changes in the sea ice characteristics in the Barents Sea have potential consequences for the weather and climate systems of mid-latitude continents, Arctic ecosystems, and fisheries, as well as Arctic maritime navigation. Simulations and projections of winter sea ice in the Barents Sea based on the latest 41 climate models from the Coupled Model Intercomparison Project Phase 6 (CMIP6) are investigated in this study. Results show that most CMIP6 models overestimate winter sea ice in the Barents Sea and underestimate its decreasing trend. The discrepancy is mainly attributed to the simulation bias towards an overly weak ocean heat transport through the Barents Sea Opening and the underestimation of its increasing trend. The methods of observation-based model selection and emergent constraint were used to project future winter sea ice changes in the Barents Sea. Projections indicate that sea ice in the Barents Sea will continue to decline in a warming climate and that a winter ice-free Barents Sea will occur for the first time during 2042–2089 under the Shared Socioeconomic Pathway 585 (SSP5-8.5). Even in the observation-based selected models, the sensitivity of winter sea ice in the Barents Sea to global warming is weaker than observed, indicating that a winter ice-free Barents Sea might occur earlier than projected by the CMIP6 simulations. [ABSTRACT FROM AUTHOR]

The global wave model WAVEWATCH III®; works well in open water. To simulate the propagation and attenuation of waves through ice-covered water, existing simulations have considered the influence of sea ice by adding the sea ice concentration in the wind wave module; however, they simply suppose that the wind cannot penetrate the ice layer and ignore the possibility of wind forcing waves below the ice cover. To improve the simulation performance of wind wave modules in the marginal ice zone (MIZ), this study proposes a parameterization scheme by directly including the sea ice thickness. Instead of scaling the wind input with the fraction of open water, this new scheme allows partial wind input in ice-covered areas based on the ice thickness. Compared with observations in the Barents Sea in 2016, the new scheme appears to improve the modeled waves in the high-frequency band. Sensitivity experiments with and without wind wave modules show that wind waves can play an important role in areas with low sea ice concentration in the MIZ. [ABSTRACT FROM AUTHOR]