Throughout 2013, positive surface water temperature anomalies prevailed in the Barents Sea. The largest anomalies (up to 4.0°C) were found in the eastern sea. Compared to 2012, the surface temperatures were much higher (by 1.3–2.7°C) in most of the Barents Sea, especially in its central and southern parts. In August–September 2013, during the joint Norwegian-Russian ecosystem survey, the surface temperatures were the highest since 1951 in about 50% of the surveyed area (ICES AFWG, 2014).
Sea surface temperature (SST) data from the IRI/LDEO Climate Data Library (http://iridl.ldeo.columbia.edu) were averaged over the southwestern (71–74°N, 20–40°E) and southeastern (69–73°N, 42–55°E) parts of the Barents Sea. During 2012, increasing SST anomalies took place in the Barents Sea. This increase was particularly rapid in the southeastern part, where positive anomalies increased from 0.7°C in January to 2.4°C in July (Figure 4.2.5). In the southwestern Barents Sea, positive anomalies of 0.1–1.1°C were observed throughout 2012.
Measurements of coastal waters at the Ingøy fixed station indicate that during 2013, the temperatures throughout the water column were generally higher than the 1968-1993 average, and especially during the latter half of the year (not shown).
Figure 4.2.5. Sea surface temperature anomalies in the western (upper) and eastern (lower) Barents Sea in 1985–2012 (Anon., 2013).During August–October 2013, the Joint Norwegian-Russian Ecosystem Survey of the Barents Sea was carried out. Survey measurements of surface water temperature in most areas were 1–3°C warmer than the long-term average (Figure 4.2.6). The largest positive anomalies (greater than 2.0°C) were mainly observed east of 30°E. The surface waters were generally warmer in summer 2013 as compared with summer 2012, and especially so in the southeastern areas. Northeastern areas were 0-1°C colder than in 2012.
Figure 4.2.6. Surface temperature anomalies in the Barents Sea in August–October 2013 (left) and differences in temperature between 2013 and 2012 (right) (Anon., 2014).During August–October 2013 throughout the Barents Sea, temperatures at depths below 100m were generally above the long-term average (by 0.5-1.2oC); except for Spitsbergen bank, where bottom temperatures were more than 2°C warmer than normal. Bottom temperatures were generally colder than in 2012 (Figure 4.2.7). These warm temperatures were likely due to inflow of high-temperature water masses from the Norwegian Sea, and due to stronger-than-usual seasonal warming of the surface waters during summer (ICES AFWG, 2014).
The area occupied by cold water (temperatures below zero) was larger than in 2012, and cold temperatures were observed more frequently than in 2012.
Figure 4.2.7. 100 m (upper) and near-bottom (lower) temperature anomalies in the Barents Sea in August–October 2013 (left) and differences in temperature between 2013 and 2012 (right) (Anon., 2014).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. During fall 2011 and winter 2012 the inflow was particularly low, but thereafter the inflow increased during spring 2013. The data time series stops in late spring 2013, thus information about the fall and early winter 2013 is not available.
In past decades, the area of Atlantic Water and mixed water has increased, whereas that of Arctic water has decreased (Figure 4.2.8). In 2013 the general temperature decrease compared to the year before lead to a slight increase in areas occupied with Arctic Water and slight decrease in areas occupied by Atlantic Water and mixed waters.
Figure 4.2.8. Area of water masses in the Barents Sea from 1970-2014 (based on average temperature 50-200 m depth).During 2013, stratification in the northern part the Barents Sea was slightly stronger than in 2012 due to slightly more ice coverage during winter. This indicates less production in these waters due to less input of nutrients from the deeper waters. In the southeastern areas, stratification during 2013 was significantly higher than in 2012, indicating less local production likely caused by the lower salinity in the coastal waters. In the southwestern areas the stratification was slightly higher in 2013 than in 2012 (Figure 4.2.9).
Figure 4.2.9. Mean density difference between 0 and 50 m depth during August–October. The three boxes show the geographical areas for which stratified indices have been calculated.