Interannual Variability of the Polar Front Surface Thermohaline Properties in the Barents Sea

Abstract

The Barents Sea (BS) is a hotspot of Atlantification of the Arctic Ocean, exhibiting a large sea ice decline and ocean warming over the past decades. In the northern BS, these changes may have strongly impacted the Polar Front (PF), the natural frontier between the hydrological, biogeochemical, ecological, and sea ice conditions of the Atlantic and Arctic Ocean. In summer, the sea surface salinity (SSS) gradient provides a better identification of the PF rather than the sea surface temperature gradient, but the interannual mechanisms driving the PF change remain unclear. In this study, taking advantage of the recent development of the CCI + SSS L-band satellite product, we can monitor, for the first time, the interannual variability of SSS signature of the PF during late summer over the period 2010–2022. Satellite measurements reveal that the interannual variability of the PF intensity in September is driven by a strong SSS variability ($>$1 pss) north of the front. The interannual SSS anomalies are mainly explained by the surface freshwater flux associated with the local melt of the imported sea ice. Moreover, the intensity of the PF has likely decreased over the past several decades as a result of the reduction of sea ice import into the northern BS. Since mid-2,000's, more intermittent surface melting may have been the main source of freshwater north of the PF during summer. This may help to preserve the lower SSS Arctic conditions of the northern BS in the context of the Atlantification.