The Barents Sea is a shelf sea of the Arctic Ocean. Being a transition area between the North Atlantic and the Arctic Basin, it plays a key role in water exchange between them. Atlantic waters enter the Arctic Basin through the Barents Sea and the Fram Strait (Figure 3.1.1). Variations in volume flux, temperature and salinity of Atlantic waters affect hydrographic conditions in both the Barents Sea and the Arctic Ocean and are related to large-scale atmospheric pressure systems.
Air pressure, wind and air temperature
In 2017, the winter (December–March) NAO index was 0.89 that was slightly less than in 2016 (1.00). Over the Barents Sea, westerly winds prevailed in January–March 2017 and easterly winds – during the rest of the year. The number of days with winds more than 15 m/s was larger than usual most of the year. It was close to normal only in April, July and October in the western part of the sea, in March, July and October in the central part and in July in the eastern part. In 2017, overall, the storm activity in the central and eastern Barents Sea was a record high since 1981.
Air temperature (http://nomad2.ncep.noaa.gov) averaged over the western (70–76°N, 15–35°E) and eastern (69–77°N, 35–55°E) Barents Sea showed that positive air temperature anomalies prevailed over the sea during most of 2017 (Figure 3.1.2). Higher positive anomalies (>5.0°C) were found in the eastern part in January, February, March and December. Significant negative anomalies (–1.7°C in the west and –1.2°C in the east) were only observed in May (see Figure 3.1.2).
Ice conditions in the Barents Sea in 2017 developed as in low-ice years. In January–March, the ice coverage (expressed as a percentage of the sea area) was 20–23% lower than normal (Figure 3.1.3). However, it was higher than in 2016 from February to the end of the year. The seasonal maximum of ice coverage was, as usual, in April, and it was 17% lower than normal. Ice melting started intensively only in June. In summer, the ice coverage was 6–15% lower than normal but 4–17% higher than in the previous year. In September, ice was only observed between islands of the Franz Josef Land Archipelago and east of the Spitsbergen Archipelago; the ice coverage was 1% that was 6% lower than normal. Freezing started in the northern Barents Sea in October (more intensively in the third decade); the monthly mean ice coverage was 6% that was 9% lower than normal but 4% higher than in the previous year. In November and December, the ice coverage was 18–23% lower than normal. Overall, the 2017 annual mean ice coverage of the Barents Sea was 15% lower than normal but 7% higher than in 2016.
Currents and transports
The volume flux into the Barents Sea varies with periods of several years, and was significantly lower during 1997–2002 than during 2003–2006. In 2006, the volume flux was at a maximum during winter and very low during fall. After 2006, the inflow has been relatively low. Throughout 2016, other than during the winter months, the inflow of Atlantic Water was somewhat lower than the long-term average (Figure 3.1.4), whereas in early 2017 the inflow was close to or slightly above the long-term average. The data series presently stops in March 2017, thus no information about the summer, fall and early winter 2017 is yet available.
Complementing the observed volume flux, numerical modeling suggests that the volume flux into the Barents Sea through the BSO was below average throughout 2017, except for the months January and March (Figure 3.1.5). Indeed, during February and May-September the inflow through the BSO was about 1 Sv or more, translating to one standard deviation, or more, below the seasonal average. Similarly, the eastward flow through the BSX, i.e., into the norther Kara Sea, was below average during the same period, although to a lesser extent in the summer months (Jul-Aug). In June, however, the volume flux was 2 standard deviations below average in both BSO and BSX. In the SBSO, which feeds into the Kara Gate, volume flux was generally close to average, except for the months February, April, and September. The NBSO, i.e., the openings between Svalbard and Franz Josef Land providing a direct link between the Barents Sea and the Polar Basin, showed opposite behavior to the other three openings, with a generally neutral to positive (i.e., northward) anomaly in volume flux throughout 2017. However, June stands out with the positive anomaly exceeding 2 standard deviations.
Note that the model has been found to be accurate for annual mean and standard deviation of the volume transports, while modelled monthly averages are usually weakly, yet statistically significantly correlated with observations (Lien et al., 2013, 2016).
Temperature and salinity in standard sections and northern boundary regions
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 Fugløya–Bear Island Section temperature is averaged over the 50–200 m depth layer while in the Kola Section temperature is averaged from 0 to 200 m depth.
In 2017, the temperature of Atlantic Water flowing into the Barents Sea through Fugløya–Bear Island Section (50–200 m) was 0.7°C above the long-term average in March and October and 0.4°C above the long-term mean in summer and early autumn (Figure 3.1.6). On average, the 2017 temperature was slightly lower than that in 2016 (see Figure 3.1.6).
Compared to the first half of 2016, when record high positive temperature anomalies (1.2–1.5°C) were observed in the Kola Section, in the second half of 2017 they decreased significantly (Figure 3.1.7). During most of the 2017 observation period, Atlantic waters in the 0–200 m layer were 0.8–0.9°C warmer than average. Temperature anomalies in coastal waters were decreasing from June (0.8°C) to October (0.2°C). Thus, by October, the temperature of the coastal water was close to average. In November–December, seasonal cooling rates of waters in the Kola Section were much lower than average (by 0.6°C per month). As a result, by December, positive temperature anomalies in the 0–200 m layer exceeded 1.0°C in all parts of the section this was typical of anomalously warm years (see Figure 3.1.7).
Figure 3.1.7. Monthly mean temperature (left) and salinity (right) anomalies in the 0–200 m layer in the Kola Section in 2016 and 2017. St. 1–3 – Coastal waters, St. 3–7 – Murmansk Current, St. 8–10 – Central branch of the North Cape Current.
In 2017, the salinity of te coastal and Atlantic waters (the Murman Current) in the Kola Section was 0.05–0.13 lower than normal (see Figure 3.1.7). The salinity of Atlantic waters in outer part of the section (the Central branch of the North Cape Current) was close to average.
In the northern Barents Sea (NW) there was temperature decrease in 2017 compared with the two years preceding, with the temperature anomaly decreasing from 0.95°C in 2015 and 0.78°C in 2016 to 0.19°C in 2017. In the northeastern Barents Sea, the temperature increased, with a temperature anomaly of 1.08°C in 2017 compared with 0.70°C in 2015.
Spatial variation in temperature and salinity (surface, 100 m and bottom)
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 showed positive anomalies prevailing in both areas during 2017 (Figure 3.1.8). In January–March, they exceeded 1.0°C and were the largest since 1981. In spring and early summer, anomalies decreased to 0.5°C in the southwest and to 0.3°C in the southeast. In July, they increased abruptly. In July and August, the anomalies in 2017 were observed in the southwestern part of the sea were the highest since 1981; the largest anomalies in 2017 were observed in the southeastern part. In autumn, positive anomalies were relatively high (0.7–1.5°C).
During August–October 2017, the joint Norwegian-Russian ecosystem survey was carried out in the Barents Sea. Surface temperature was on average 1.1°C higher than the long-term mean (1931–2010) in most of the Barents Sea (five sixths of the surveyed area) (Figure 3.1.9). The largest positive anomalies (>2.0°C) were observed west of Bear Island, west and south of Spitsbergen Archipelago and in the southeastern part of the sea. Negative anomalies were observed in the southwestern and northernmost Barents Sea as well as north of Spitsbergen Archipelago. Compared to 2016, surface temperature was lower (by 1.0°C on average) in most of the Barents Sea (five sixths of the surveyed area), especially in the northern and eastern parts. Surface waters were on average 0.4°C warmer than in 2016 only in the western Barents Sea, especially in the areas where the largest positive anomalies were observed in 2017.
Figure 3.1.9. Surface temperatures (°C) in August–October 2016 (upper left) and 2017 (upper right), their differences between 2017 and 2016 (lower left, °C) and anomalies in August–October 2017 (lower right, °C).
As usual, Arctic waters were mainly found in the 50–100 m layer north of 77°N and dominated at 50 m depth. The temperatures at depths of 50 and 100 m were higher than the long-term mean (on average, by 1.0 and 0.8°C respectively) in most of the Barents Sea (Figure 3.1.10). Negative anomalies were mainly observed in the northern part of the sea and north of the Spitsbergen Archipelago. Compared to 2016, the 50m temperature was lower (on average, by 1.1°C) in most of the sea (six sevenths of the surveyed area) and the 100m temperature was lower (on average, by 0.7°C) almost all over the Barents Sea. Positive differences in 50 m temperature between 2017 and 2016 took place only in some small areas located in the central and western Barents Sea.
Figure 3.1.10. 100 m depth temperatures (°C) in August–October 2016 (upper left) and 2017 (upper right), their differences between 2017 and 2016 (lower left, °C) and anomalies in August–October 2017 (lower right, °C).
Bottom temperature was in general 1.1°C above average in most of the Barents Sea (Figure 3.1.11). Negative anomalies (–1.0°C on average) were only observed in the northern sea and north of Spitsbergen Archipelago. Compared to 2016, bottom temperature was on average 0.8°C lower in most of the Barents Sea. Bottom waters were slightly warmer (on average, by 0.2°C) than in 2016 only in the Eastern Basin and in a small area east of Great Bank. In August–October 2017, the area occupied by water with temperatures below zero was larger than in the previous year and it was mainly located east of Spitsbergen Archipelago. Lowest bottom temperatures (below –1°C) were observed between Great Bank and Spitsbergen Archipelago.
Figure 3.1.11. Bottom temperatures (°C) in August–October 2016 (upper left) and 2017 (upper right), their differences between 2017 and 2016 (lower left, °C) and anomalies in August–October 2017 (lower right, °C).
Surface salinity was on average 0.3 higher than the long-term mean (1931–2010) in most of the Barents Sea (two thirds of the surveyed area) with the largest positive anomalies (>0.8) west of Spitsbergen Archipelago as well as in the southeastern and northeastern sea (Figure 3.1.12). Negative anomalies (–0.3 on average) were mainly observed in southern and northern parts of the sea with largest values north of Kanin Peninsula and north of Spitsbergen Archipelago. In August–October 2017, surface waters were on average 0.3 fresher than in 2016 in 75% of the surveyed area with largest negative differences in the northern (north of 77°N) and south-eastern (along Southern Island of the Novaya Zemlya Archipelago and north of Kanin Peninsula) parts of the Barents Sea. Small positive differences in salinity between 2017 and 2016 (0.1 on average) were observed in central and western parts of the sea as well as north of Kolguev Island.
Salinity at 100 m was close to average in general (Figure 3.1.13). Small negative anomalies (on average –0.1) were mainly observed in the southern Barents Sea and north of Spitsbergen Archipelago. Small positive anomalies (on average 0.1) were found in the northwestern Barents Sea, especially east of Spitsbergen Archipelago. Compared to 2016, salinity at 100 m was lowest in most of the Barents Sea in 2017. The positive differences in salinity between 2017 and 2016 were mainly found in northwestern and southeastern parts of the sea, as well as in coastal waters in south-westernmost part of the surveyed area.
Bottom salinity was close to both the average and that observed in 2016 in most of the Barents Sea (Figure 3.1.14). Significant anomalies were mainly found in shallow waters: negative – in south-easternmost Barents Sea and east of Spitsbergen Archipelago, positive – over Spitsbergen Bank and north of Kolguev Island.
Area of water masses
In August–October 2017, at 50, 100 m and near the bottom, the area covered by warm water (above 4, 3 and 1°С respectively) was smaller (by 7, 11 and 10% respectively) than in 2016, when it was the record largest recorded (Figure 3.1.15). In contrast, the area covered by cold water (below 0°С) was larger (by 9, 10, and 4% respectively) in 2017 compared to 2016, when it was smallest on record (see Figure 3.1.15). Since 2000, the area covered by cold bottom water was largest in 2003 and relatively small in 2007, 2008, 2012, 2016, and 2017. In 2016, the area covered by cold bottom water was the lowest since 1965 – the year when the joint autumn surveys started.
In recent decades, the area of Atlantic and mixed waters has increased, whereas that of Arctic waters has decreased (Figure 3.1.16). In August–October 2017, the area covered by Atlantic waters remained large, but decreased relative to 2016, when it was the largest since 1965. The area covered by Arctic waters was remained small in 2017, but increased relative to 2016, when it was the smallest since 1965.
Figure 3.1.15. Areas covered by water with different temperatures at 50m (upper panel), 100 m (middle panel) and near the bottom (lower panel) in the Barents Sea (71–79°N, 25–55°E) in August–September 2000–2017.