The Barents Sea has become substantial colder since 2015–2016. However, its air and water temperatures in 2020 were generally higher than long-term average, being typical of warm year. In autumn, the areas covered by Atlantic (>3°С) and Arctic (<0°С) waters changed insignificantly compared to 2019; while the area covered by cold bottom waters (<0°С) increased and turned out to be the largest since 2011. Ice coverage of the Barents Sea has increased since 2016 due to lower temperatures and lower inflow of Atlantic Water, but the ice coverage in 2020 was still below average. There was almost no ice in the sea from August to November. In November, the ice coverage reached a record-low value of 3% since 1951.
In 2020, the winter (December–March) NAO index was 1.78 that was much higher than in 2019 (0.74) and reached the fourth maximum since 1900 (after 1989 – 2.43, 1990 – 1.91 and 2015 – 1.83). Over the Barents Sea, the number of days with winds more than 15 m/s was higher than or close to the long-term mean (1981–2010) all over the year, with the largest anomaly in March. The storm activity was a record high (since 1981) in the western part of the sea in January, April and November, in the eastern part in March and April, and in the central part in March. For the whole year 2020, it was also a record high in the western Barents Sea (181 days) and reached the second highest value in the central (157 days) and eastern (165 days) parts of the sea.
From January to April 2020, the Barents Sea ice extent (expressed as a percentage of the total sea area) was slightly (by 3–7%) less than the long-term means (1981–2010) (Fig. 3.1.3). However, in May, intensive ice melting started, and by August, the sea was completely free of ice.
The Fugløya–Bear Island and Vardø-North Sections covers the inflow of Atlantic and Coastal water masses from the Norwegian Sea to the Barents Sea, while the Kola Section covers the same waters in the southern Barents Sea. Note a difference in the calculation of the temperatures in these sections; in the Fugløya–Bear Island and Vardø-North Sections the temperature is averaged over the 50–200 m depth layer while in the Kola Section the temperature is averaged from 0 to 200 m depth.
Sea surface temperature (SST) (http://iridl.ldeo.columbia.edu) averaged over the southwestern (71–74°N, 20–40°E) and southeastern (69–73°N, 42–55°E) Barents Sea exceeded the long-term mean (1982–2010) throughout 2020 (Fig. 3.1.7). Small positive anomalies (0.1–0.3°С) were found in the southwestern part of the sea in the first half of the year and large ones (1.1–3.2°С) were observed in the southeastern part in the second half of the year.
Focusing on different depths, the area covered by warm water (above 4, 3 and 1°С at 50, 100 m and near the bottom, respectively) in August–October 2020 was close to that in 2019 (Fig. 3.1.14). The area covered by cold water (below 0°С) was 3 and 6% larger than in 2019 at 50 m and near the bottom, respectively, but 3% smaller – at 100 m.
The volume flux into the Barents Sea varies with periods of several years. The annual volume flux was relatively high during 2003–2006 (Fig. 3.1.4a). From 2006 to 2014, the inflow was relatively stable before it increased substantially in 2015 to about 1 Sv above the long-term average. The year of 2016 had relatively low inflow. Since 2017 the annual volume inflow to the Barents Sea has decreased (Fig. 3.1.4a). There is no statistically significant trend in the annual volume fluxes
The Fugløya–Bear Island Section covers the inflow of Atlantic and Coastal water masses from the Norwegian Sea to the Barents Sea, while the Kola Section covers the same waters in the southern Barents Sea. Note a difference in the calculation of the temperatures in these sections; in the Fugløya–Bear Island Section the temperature is averaged over the 50–200 m depth layer while in the Kola Section the temperature is averaged from 0 to 200 m depth.
The summer abundance of minke whales in the Barents Sea has recently increased from a stable level of about 40,000 animals to around 70,000 animals. Also, humpback whales have increased their summer abundance in the Barents Sea from a low level prior to year 2000 to about 7,000 animals in recent years. The other cetacean populations have remained stable in numbers.
Mesozooplankton biomass in autumn 2020 averaged about 7 g dry-weight m-2 for the parts of the Barents Sea that were covered. The spatial distribution of biomass across the Barents Sea displayed a typical pattern with high levels in southwestern and northern regions, and relatively low levels in central areas. Compared to the preceding 5 year averages, mesozooplankton biomass in 2020 was lower in the western, central, and eastern Barents Sea and slightly higher south and east of Svalbard. In the western subareas of the Barents Sea, including the region influenced by the inflowing North Atlantic Current, and where information on size-fractions is available, the decreased biomass in 2020 was mainly ascribed to the intermediate fraction (1000-2000 µm). This fraction mainly includes relatively large copepods such as older developmental stages of Calanus finmarchicus. Krill indices for biomass and abundances in the Barents Sea have shown increasing trends over recent decades.
The area covered in 2020 are given in Fig. 220.127.116.11, and 18.104.22.168. In contrast to previous years, the station grid in 2020 covered the entire Barents Sea shelf, including the upper bathyal slope north to FJL. Russian and Norwegian experts were involved in the megabenthos by-catch processing and distributed on the BESS vessels (RV “G.O. Sars”, RV “Kronprints Håkon”, SRV “AtlantNIRO”, and SRV “Vilnus”). On the Norwegian vessel “Johan Hjort” megabenthos was only processed to large animal groups due to a lack of skilled benthic experts onboard.
Zero-group fish are important consumers of plankton and are prey for other predators, and, therefore, are important for transfer of energy between trophic levels in the ecosystem. Estimated total biomass of 0-group fish species (cod, haddock, herring, capelin, polar cod, and redfish) varied from a low of 165 thousand tonnes in 2001 to a peak of 3.4 million tonnes in 2004 with a long-term average of 1.7 million tonnes (1993-2020) (Fig. 3.6.1).
Sea ice biota are organisms that live in, on or associated with sea ice (Horner et al. 1992, Bluhm et al. 2017a). More than 2000 species from several phyla, including viruses, bacteria, archaea, microalgae, fungi, protozoa (e.g. ciliates, choanoflagellates, amoeba, foraminifera) and invertebrates (e.g. rotifers, nematodes, copepods, amphipods) are associated with sea ice in most of their life cycle (Bluhm et al. 20I7a and b, Hassett and Gradinger 2016, Ehrlich et al. 2020, Gradinger 2020). The properties of the ice (e.g. age, thickness, light conditions, drift, etc.) determine the type of ice-associated community and its development (Syvertsen 1991, Gradinger et al. 2010, Fernandez-Mendez et al. 2018, Hop et al. 2020).
Most Barents Sea fish species are demersal (Dolgov et al., 2011); this fish community consists of about 70–90 regularly occurring species, which have been classified into zoogeographic groups. Approximately 25% are either Arctic or mainly Arctic species. The commercial species are boreal or mainly boreal species (Andriashev and Chernova, 1995), except for Greenland halibut (Reinhardtius hippoglossoides) that is classified as either Arcto-boreal (Mecklenburg et al., 2013) or mainly Arctic (Andriashev and Chernova, 1995).
This years chapter could not be updated. Satellite-based annual net primary production in the Barents Sea has shown an increasing trend with a doubling over the last twenty years, due to increased temperatures leading to reduced ice-coverage and prolonged open water period.
The commercial fisheries in the Barents Sea Ecoregion target few stocks. The largest pelagic fishery targets capelin using midwater trawl and purse seine. The largest demersal fisheries target cod, haddock, and other gadoids; predominantly using trawls, gillnets, longlines, and handlines.
Norwegian and Russian vessels harvest northern shrimp over the stock’s entire area of distribution in the Barents Sea. Vessels from other nations are restricted to trawling shrimp only in the Svalbard zone and the Loophole (international waters of the central Barents Sea). No overall TAC has been set for northern shrimp, and the fishery is regulated through effort control, licensing, and a partial TAC in the Russian zone only.
Management of the minke whale is based on the Revised Management Procedure (RMP) developed by the Scientific Committee of the International Whaling Commission. Inputs to this procedure are catch statistics and absolute abundance estimates.
Fishing activity in the Barents Sea is tracked by the Vessel Monitoring System (VMS). Figures 22.214.171.124 and 126.96.36.199 show fishing activity in 2017-2020 based on Russian and Norwegian data. VMS data offer valuable information about temporal and spatial changes in fishing activity.
The 2020 ecosystem survey collected 95 species from 29 families. It is 4 species and 1 family more than in 2019. Distribution of the groups have not changed since the previous year, but the larger geographical coverage of the survey allowed to uncover a large part of the Arctic and mainly Arctic species habitat (Fig. 3.8.1).
Fourteen years (2006–2019) of capelin diet were examined from the Barents Sea where capelin is a key species both as a prey and predator. The PINRO/IMR mesozooplankton distribution usually shows low plankton biomass in the central Barents Sea, most likely due to predation pressure from capelin and other pelagic fish.
Cod is the major predator on capelin; although other fish species, seabirds and marine mammals are also important predators. The cod stock abundance in the Barents Sea peaked around 2013 and have declined since, although it is still above the long-term average. The cod spawning stock and thus the abundance of old, large fish is still high.
The Barents Sea capelin has undergone dramatic changes in stock size over the last four decades. Three major stock collapses (when abundance was low for several years and fishing moratoriums imposed) occurred during 1985–1989, 1993–1997, and 2003–2006. During the recent period 2014-2020 the stock estimates have fluctuated considerably.
The Barents Sea polar cod stock was above 800 kt in the period 1998-2011 (except from the year 2003 when the stock was probably grossly underestimated) but dropped to below half of that in 2012-15 (Figure 4.4.1). In 2016, the strong 2015-year class brought the stock up to nearly 1 million tonnes but dropped to low levels in 2017-2019.
The summer overlap between cod and capelin increased from 2008 to 2016, mainly due to an increasing cod stock and increased size of suitable habitat for cod. In later years the cod stock has declined and is now distributed farther south in summer. The effect of this change on overlap with capelin is unclear.
Comparative analyses of cetacean main species and fish distribution in the Barents Sea were conducted based on data from the joint Russian-Norwegian ecosystem surveys (BESS) during August-October 2005-2014.
Most of the commercial fish stocks found in the Barents Sea stocks are at or above the long-term mean level. The exception is Sebastes norvegicus. In addition, the abundance of blue whiting in the Barents Sea is at present very low, but for this stock only a minor part of the younger age groups and negligible parts of the mature stock are found in the Barents Sea.
Oceanic systems have a “longer memory” than atmospheric ones. Thus, a priori, it seems feasible to predict oceanic temperatures realistically and much further ahead than weather predictions. However, the predicting is complicated due to variations being governed by processes originating both externally and locally, which operate at different time scales.