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.
Figure 3.1.1. The main paths of Atlantic waters in the Barents Sea as well as Fugløya–Bear Island Section (1), Kola Section (2) and boxes in the northwestern (3) and northeastern (4) Barents Sea.Air pressure, wind and air temperature
In 2016, winter (December–March) NAO index dropped to 1.01 after the third highest (since 1899) positive value of 1.87 observed in 2015. Over the Barents Sea, easterly winds prevailed in the first half of the year and southwesterly winds – in the second half. In 2016, the number of days with winds more than 15 m/s was larger than usual most of the year. It was less than or close to normal only in January (western and central parts of the sea) and April (eastern part). In summer 2016, the storm activity in the Barents Sea was the highest 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 2016 (Figure 3.1.2). Higher positive anomalies (up to 7.5°C in February) were found in the east. The positive anomalies in the western part of the sea in May and in the eastern part in February, July and September were the highest since 1948. As a result, the 2016 annual mean air temperature anomalies in the western and eastern Barents Sea were also the highest since 1948.
Figure 3.1.2. Air temperature anomalies in the western (upper) and eastern (lower) Barents Sea in 1985–2016. The red line shows monthly values, the black one – 11-month running means.Ice conditions
At the end of 2015 and beginning of 2016, meteorological conditions over the Barents Sea resulted in decreasing the sea ice coverage. Ice formation was going very slowly at the beginning of 2016; the ice coverage (expressed as a percentage of the sea area) was 17–25% lower than normal (Figure 3.1.3). In March–April, the seasonal maximum of ice coverage, there was almost no increase in the ice coverage compared to that early in the year: in January and February, the ice coverage was 32 and 30% respectively, whereas, in March and April, it was 32 and 31% which was 26–30% lower than normal (Figure 3.1.4). From March to July, the ice coverage of the Barents Sea was the lowest since 1951. From July to September, there was no ice in the Barents Sea. In July, it happened for the first time since 1951 (see Figure 3.1.4). In autumn, freezing started in the northern Barents Sea in October (see Figure 3.1.4), when ice appeared near the Franz Josef Land Archipelago; the ice coverage was 2% which was 13% less than normal. In November and December, the ice coverage was 25–26% less than average and it was the lowest since 1951. Overall, the 2016 annual mean ice coverage of the Barents Sea was the lowest since 1951 being 22% lower than normal and 7% lower than in 2015.
Figure 3.1.3. Ice coverage anomalies in the Barents Sea in 1985–2016. The green line shows monthly values, the black one – 11-month running means.
Figure 3.1.4. Ice concentrations in April, July and October 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 2015 and in winter 2016, the inflow was around 1 Sv larger than the long-term average (Figure 3.1.5). The exception was March 2016, when the volume flux was temporarily smaller than average. The dataseries currently stops in May 2016, thus no information about summer, fall and early winter 2017 is yet available.
Complementing the observed volume flux, numerical modelling suggests that the volume flux into the Barents Sea through the BSO was above average during February and March followed by a drop below average in April, as opposed to the temporary low observed in March (Figure 3.1.6). In the months June through August, the modelled eastward volume transport was generally below average, with the lowest value in June when the flux was 2 standard deviations below the monthly average. Modelled transports are not yet available for the period September through December. Similarly to the inflow to the western Barents Sea, the modelled outflow through the northeastern Barents Sea (BSX) was above normal during February and March, and close to or lower than normal during the period April through August. In the SBSO, between the Kola Section and Novaya Zemlya, the eastward volume transport was generally close to or below average throughout the year, except for a strong uptick of 0.2 Sv, corresponding to 1 standard deviation, in August. In the NBSO, between Svalbard and Franz Josef Land, the volume transport (positive southward) was more variable, but with a strongly negative anomaly in April. Note, however, that the model has been found to be accurate for annual mean and standard deviation of the volume transports, while the modelled monthly averages are usually weakly, yet statistically significantly correlated with observations (Lien et al., 2013, 2016).
Figure 3.1.5. Volume flux anomalies through the Fugløya–Bear Island Section.
Figure 3.1.6. Modelled volume flux anomalies relative to 1961–1990 average.
Temperature and salinity in standard sections and northern boundary regions
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 southeastern 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. In 2016, the temperature of the Atlantic Water flowing into the Barents Sea through the Fugløya–Bear Island Section (50–200 m) was 1°C above the long-term average early in the year and around 0.7°C above the long-term mean in summer and autumn (Figure 3.1.7). On average, the 2016 temperature was comparable to the temperature in 2015 (Figure 3.1.7).
Figure 3.1.7. Temperature anomalies in the 50–200 m layer in the Fugløya–Bear Island Section.
According to the available observations along the Kola Section, from January to May 2016, coastal and Atlantic waters in the 0–200 m layer had large positive temperature anomalies exceeding 1°C (Figure 3.1.8). The temperature anomalies in the coastal waters (March–May, November), the Murmansk Current (January, March, April) and the Central branch of the North Cape Current (January) were the highest since 1951. As a result, January–May averaged temperature was the highest in the coastal waters and as large as a record-high value of 2012 in the Atlantic waters of the central part of the section. Compared to 2015, the coastal and Atlantic waters were warmer (by up to 0.8°C) during all the observation period in 2016.
In 2016, the salinity of the coastal and Atlantic waters (the Murmansk Current) in the Kola Section was lower than normal and compared to 2015 (Figure 3.1.8). The coastal waters were much fresher than normal with negative salinity anomalies reaching –0.3 in the first half of the year. The salinity of the Atlantic waters in the outer part of the section (the Central branch of the North Cape Current) was close to both the average and that in the previous year.
Figure 3.1.8. Monthly mean temperature (left) and salinity (right) anomalies in the 0–200 m layer in the Kola Section in 2015 and 2016. St. 1–3 – Coastal waters, St. 3–7 – Murmansk Current, St. 8–10 – Central branch of the North Cape Current.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 that positive SST anomalies prevailed in both areas during 2016 (Figure 3.1.9). The positive anomalies in the east were much higher than in the west (by up to 3.7– 4.0°C in July–August). The SST anomalies in the southwestern part of the sea in October–December, as well as in the southeastern part in February–May and July–December were the highest since 1982. As a result, the 2016 annual mean SST anomalies in the southwestern and southeastern parts of the Barents Sea were also the highest since 1982.
Figure 3.1.9. Sea surface temperature anomalies in the western (upper) and eastern (lower) Barents Sea in 1985–2016. The blue line shows monthly values, the black one – 11-month running means.In August–September 2016, the joint Norwegian-Russian ecosystem survey was carried out in the Barents Sea. The surface temperature was on average 1.8°C higher than the long-term means (1931–2010) all over the Barents Sea (Figure 3.1.10). The largest temperature anomalies (>2.5°C) were mainly observed in the eastern and southeastern parts of the sea and resulted from anomalously warm air masses over those areas. The smallest positive anomalies (<0.5°C) were found in the southwestern Barents Sea. Compared to 2015, the surface temperature was higher (by 1.1°C on average) in most of the sea (two thirds of the surveyed area), especially in the northwestern and southeastern parts. The surface waters were on average 0.4°C colder than in 2015 mostly in the southwestern and central Barents Sea.
Arctic waters were mainly found, as usual, in the 50–100 m layer north of 77°N. The temperature at 100m depth was higher than the long-term means (on average, by 1.5°C) all over the Barents Sea (Figure 3.1.11). Compared to 2015, the 100 m depth temperature was higher (on average, by 0.5°C) in most of the sea (five sixths of the surveyed area). Negative differences in temperature between 2016 and 2015 (–0.3°C on average) were found only in some local areas.
The bottom temperature was in general 1.6°C above average throughout the Barents Sea (Figure 3.1.12). The largest temperature anomalies (>2.5°C) were mainly observed over the Spitsbergen Bank and in the Pechora Sea. Compared to 2015, the bottom temperature was on average 0.8°C higher almost all over the Barents Sea. Small negative differences in temperature between 2016 and 2015 were on average –0.2°C and were found only in about 6% of the surveyed area (mainly in the southwestern part of the sea).
Figure 3.1.10. Surface temperatures (°C) in August–September 2015 (upper left) and 2016 (upper right), their differences between 2016 and 2015 (lower left, °C) and anomalies in August–September 2016 (lower right, °C).
Figure 3.1.11. 100 m depth temperatures (°C) in August–September 2015 (upper left) and 2016 (upper right), their differences between 2016 and 2015 (lower left, °C) and anomalies in August–September 2016 (lower right, °C).
Figure 3.1.12. Bottom temperatures (°C) in August–September 2015 (upper left) and 2016 (upper right), their differences between 2016 and 2015 (lower left, °C) and anomalies in August–September 2016 (lower right, °C).The surface salinity was on average 0.5 higher than the long-term mean (1931–2010) almost all over the Barents Sea with the largest positive anomalies (>0.5) mainly north of 75°30'N (especially in the area of the Great Bank) and east of 48°E (especially west and south of Southern Island of the Novaya Zemlya Archipelago) (Figure 3.1.13). The large negative anomalies were only observed north of Kolguev Island. In August–September 2016, the surface waters were saltier than in 2015 in about 60% of the surveyed area with the largest positive differences in the Pechora Sea, along the Novaya Zemlya Archipelago and south of the Spitsbergen Archipelago. Negative differences in salinity between 2016 and 2015 were mainly found in the central and northeastern Barents Sea as well as north of Kolguev Island.
The 100 m salinity was higher than the long-term means (on average, by 0.1) in about 80% of the surveyed area (Figure 3.1.14). Small negative anomalies were only observed in some areas, especially in the southwestern and southeastern Barents Sea. Compared to 2015, negative differences in salinity between 2016 and 2015 prevailed in the Barents Sea and occupied almost two thirds of the surveyed area. The positive differences were mainly found in the southwestern part of the sea.
The bottom salinity was slightly higher than the long-term means (by up to 0.1) in about four fifths of the surveyed area and it was close to that in 2015 (Figure 3.1.15). Negative anomalies were mainly found in the southeastern Barents Sea, especially in the Pechora Sea. The largest differences in salinity between 2016 and 2015 were observed in shallow waters between Bear and Hopen Islands (positive values) and in the southeastern Barents Sea (negative values).
Figure 3.1.13. Surface salinities in August–September 2015 (upper left) and 2016 (upper right), their differences between 2016 and 2015 (lower left) and anomalies in August–September 2016 (lower right).
Figure 3.1.14. 100 m salinities in August–September 2015 (upper left) and 2016 (upper right), their differences between 2016 and 2015 (lower left) and anomalies in August–September 2016 (lower right).
Figure 3.1.15. Bottom salinities in August–September 2015 (upper left) and 2016 (upper right), their differences between 2016 and 2015 (lower left) and anomalies in August–September 2016 (lower right).Area of water masses
In the past decades, the area of Atlantic and mixed waters has increased, whereas that of Arctic waters has decreased (Figure 3.1.16). In August–September 2016, the area covered by Atlantic waters was the largest, whereas the area covered by Arctic waters was the smallest since 1965.
In August–September 2016, at 50, 100 m and near the bottom, the area covered by warm water (above 3°С) was the largest whereas the area covered by cold water (below 0°С) was the smallest since 2000 (Figure 3.1.17). Since 2000, the area covered by cold bottom water was the largest in 2003 and rather small in 2007, 2008, 2012 and 2016; in 2016, it reached a record low value since 1965 – the year when the joint autumn surveys started.
Figure 3.1.16. Area of water masses in the Barents Sea (70–79°N, 20–60°E) in August–September 1965–2016 (based on 50–200 m averaged temperature).
Figure 3.1.17. 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 (70–79°N, 20–60°E) in August–September 2000–2016.