The Keldysh Current in the Kara Sea

Using the set of 25 shipboard hydrographic transects across the northeastern part of the Barents Sea and the northern part of the Kara Sea obtained between 1995 and 2024, we have defined the existence of a surface current transporting Atlantic-origin water from the northern shore of Novaya Zemlya to the Kara Sea continental slope. It has been named the Keldysh Current after R/V “Akademik Mstislav Keldysh”, which performed numerous oceanographic surveys in the Arctic Ocean. The Keldysh Current is a part of the local complex system of Atlantic-origin surface, intermediate and bottom currents. It has a specific formation process and surface-advected pathway, which was not described before in dozens of papers focused on the circulation of water masses in this area. The Keldysh Current originates from the Barents Sea branch water (BSBW), which cools and sinks down in the northeastern part of the Barents Sea. Previously it was believed that the whole volume of BSBW loses contact with atmosphere in this area. In this paper, we demonstrate that the northern periphery of BSBW, which is freshened due to mixing with the Arctic surface water, remains at sea surface layer despite this cooling. This part of BSBW forms the surface-advected Keldysh Current with significantly higher temperatures and salinities, as compared to the adjacent surface waters. The Keldysh Current becomes isolated from the bottom-advected main flow of BSBW by cold dense water formed as a result of sea ice formation and salt ejection to the water column near Franz Joseph Land. However, due to dynamic entrainment, the Keldysh Current follows the flow of the BSBW, namely, northeastward along the northern shore of Novaya Zemlya, then northward along the eastern flank of the St. Anna Trough to the continental slope, then eastward along the continental slope towards the Laptev Sea. The Keldysh Current is order 50–100 km wide, 50–100 m deep, more than 1000 km long and transports ~0.4 Sv.