Circulation and Hydrography in the Northwestern Barents Sea: Insights From Recent Observations and Historical Data (1950-2022)

The Barents Sea is one of the main pathways for warm and saline Atlantic Water (AW) entering the Arctic Ocean. It is an important region where water mass transformation and dense-water production contribute to the Atlantic meridional overturning circulation. Here, we present data from three cruises and nine glider missions conducted between 2019 and 2022 in the northwestern Barents Sea, and compare them with historical data collected between 1950 and 2009. We present circulation pathways, hydrography and volume transports of Atlantic- and Arctic-origin waters. Our observations show that 0.9 +/- 0.1 Sv (1 Sv = 106 m3 s-1) of Atlantic-origin water reaches the Polar Front (PF) region before splitting into several branches and eventually subducting beneath Polar Water (PW). The amount of Atlantic-origin water stored in the Olga Basin north of the PF is controlled by the density difference between AW and PW, and reached a maximum in the 90s when PW was particularly fresh. In the recent period from 2019 to 2022, the inflow of AW into the Barents Sea freshened by up to 0.1 g kg-1 compared to previous decades. This led to a reduction in the production of dense water, an increased temperature gradient across the PF, and a reduced poleward transport of warm water. Warm and salty water from the Atlantic Ocean flows through the Barents Sea on its path toward the Arctic Ocean. It undergoes cooling and freshening due to interactions with the surrounding water and the atmosphere, and eventually encounters much colder and fresher Polar Water, creating a distinct boundary known as the Polar Front. We conducted several research missions in the northwestern Barents Sea between 2019 and 2022 and compared the data to historical records collected between 1950 and 2009. The cooled Atlantic Water sinks beneath the Polar Water before continuing toward the Arctic Ocean. In recent decades, the temperature of the Atlantic Water inflow has increased. The warm Atlantic Water can be traced below the Polar Front, leading to an increase in the temperature of the deeper waters north of the front. However, the amount of Atlantic Water north of the front is regulated by the density difference between the Atlantic Water and Polar Water. In the recent period of 2019-2022, the Atlantic Water reaching the front has become less salty. As a result, there is a reduced flow of warm water moving northward beneath the Polar Water and a larger temperature difference across the Polar Front. Circulation pathways and volume transport of Atlantic- and Arctic-origin waters in the northwestern Barents Sea are detailed At the Polar Front density differences between these waters create a geostrophic current that governs warm water flow into the Arctic domain Over recent decades Atlantic Water warmed and freshened, reducing its density difference with the Polar Water and inflow across the front