Synoptic variability of the Pechora plume in the Barents Sea

Previous studies have described the general spreading patterns of the Pechora plume in the southeastern Barents Sea, but its synoptic variability during the ice-free season remains largely unknown. In this study, we analyze Pechora plume dynamics on synoptic time scales during the ice-free season from 2015 to 2024 using satellite-derived sea surface salinity, sea surface temperature, and in situ observations. We reveal that the maximal plume area, reaching up to 55,000 km2, is not confined to the spring freshet period and may occur throughout the entire ice-free season under favorable wind forcing conditions. Wind primarily controls plume spreading through Ekman transport, while the timing and magnitude of peak river discharge determine freshwater volume and stratification. A time lag between the peak river discharge and freshwater inflow from Pechora Bay, i.e., the estuary of the Pechora River, to the open sea modifies the plume response to external forcing. Also, based on satellite data and in situ measurements, we reveal and describe two spreading patterns of the Pechora plume that received limited attention before. First, we identify large-scale northwestward advection of the outer part of the Pechora plume and its subsequent separation from the main part of the plume. The separated part of the plume (hereafter referred to as low-salinity lens) could drift more than 300 km towards Novaya Zemlya under northeasterly wind forcing. Second, we identify more than 30 wind-driven inflow events of the Pechora plume through the Kara Strait into the Kara Sea, which intensify inter-basin freshwater exchange between the Barents and Kara seas. These results significantly expand the current understanding on the Pechora plume dynamics and variability. It provides new insights for assessment the influence of the Pechora plume on the hydrological structure of the entire southeastern part of the Barents Sea.