Time series of area covered by Arctic Water masses in 50–200 m depth show a strong shift occurring around 2006 (Fig. 3.1.14), with substantially larger extent of Arctic Water before than after. The extent of the Atlantic Water masses show a more gradual increase over the period from 1970 to 2019, and vary to a large extent in synchrony with the temperature of the inflowing Atlantic Water in the western Barents Sea (Fig. 3.1.14).
Largest extent of Atlantic Water, and least extent of Arctic Water, were observed in 2016. After that the extent of Atlantic Water has decreased and the extent of Arctic Water decreased. The areas of the two water masses were in 2019 at about the same level as in 2004–2005.
Figure 3.1.14. Area of Atlantic Water (T>3°C) and Arctic Water (T<0°C) masses in the Barents Sea (71–79°N, 25–55°E) in August–September 1970–2019 (based on 50–200 m averaged temperature). Black lines show annual August–September values, while thick coloured lines show three years running means. Horizontal lines show average over the period 1981–2010.
Focusing in on the different depth levels, the area covered by warm water (above 4, 3 and 1°С at 50, 100 m and near the bottom respectively) in August–September 2019 was 7, 4 and 23% smaller than in 2018 at 50, 100 m and near the bottom respectively (Fig. 3.1.15). The area covered by cold water (below 0°С) was 6% larger than in 2018 at 50 and 100 m and 21% larger near the bottom. Since 2000, the area covered by cold bottom water was the largest in 2003 and rather small in 2007, 2008, 2012, 2016–2018; in 2016, it reached a record low value since 1965 and then it has been increasing for the past three years; in 2019, it almost tripled compared to the previous year.
Figure 3.1.15. Areas covered by water with different temperatures at 50 m (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 2000–2019.