Abstract
Abstract. The polar front separates the warm and saline Atlantic Water entering the southern Barents Sea from the cold and fresh Arctic Water located in the north. These water masses can mix together (mainly in the center of the Barents Sea), be cooled by the atmosphere and receive salt because of brine release; these processes generate dense water in winter, which then cascades into the Arctic Ocean to form the Arctic Intermediate Water. To study the interannual variability and evolution of the frontal zones and the corresponding variations of the water masses, we have merged data from the International Council for the Exploration of the Sea and the Arctic and Antarctic Research Institute and have built a new database, which covers the 1980–2011 period. The summer data were interpolated on a regular grid. A probability density function is used to show that the polar front splits into two branches east of 32° E where the topographic constraint weakens. Two fronts can then be identified: the Northern Front is associated with strong salinity gradients and the Southern Front with temperature gradients. Both fronts enclose the denser Barents Sea Water. The interannual variability of the water masses is apparent in the observed data and is linked to that of the ice cover. The frontal zones variability is found by using data from a general circulation model. The link with the atmospheric variability, represented here by the Arctic Oscillation, is not clear. However, model results suggest that such a link could be validated if winter data were taken into account. A strong trend appears: the Atlantic Water (Arctic Water) occupies a larger (smaller) volume of the Barents Sea. This trend amplifies during the last decade and the model study suggests that this could be accompanied by a northwards displacement of the Southern Front in the eastern part of the Barents Sea. The results are less clear for the Northern Front. The observations show that the volume of the Barents Sea Water remains nearly unchanged, which suggests a northwards shift of the Northern Front to compensate for the northward shift of the Southern Front. Lastly, we noticed that the seasonal variability of the position of the front is small.
Highlights
1.1 The Barents Sea: a key region for water mass transformationsThe Barents Sea (BS) extends over the northernmost Arctic shelf; it has a mean depth of about 230 m and covers about 1.4 million km2 (Fig. 1a)
This circulation is forced by the Atlantic Water (AW) and the Norwegian Coastal Current Water, which flow into the BS through the Barents Sea Opening (BSO), an opening onto the shelf, which is 470 m deep at the deepest point
Johannessen et al (2012) and Dalpadado et al (2012) showed that the area covered by the Atlantic Water and the mixed water had slightly increased since 1970
Summary
The Barents Sea (BS) extends over the northernmost Arctic shelf; it has a mean depth of about 230 m and covers about 1.4 million km (Fig. 1a). The cooling and mixing of the Atlantic Water, Arctic Water and Norwegian Coastal Current Water, reinforced by brine rejections due to ice formation (especially around Svalbard, Franz Josef Land and Novaya Zemlya) and favorable conditions for shelf convection (Martin and Cavalieri, 1989), produce the dense Barents Sea Water (BSW). The role of the Atlantic Water in multi-decadal ocean variability has been analyzed in depth by Yashayaev and Seidov (2015) from the World Ocean Database They found that the temperature records revealed a warming trend and a series of relatively warm and cold periods, which lag the periods of relatively low or high NAO events with a delay of about 4–5 years (the inverse for the AMO). This may still intensify the production of less dense Barents Sea Water
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