Characteristics and Seasonal Variability of the Arctic Circumpolar Boundary Current in the Eurasian Basin

The Arctic Circumpolar Boundary Current (ACBC) transports Atlantic Water (AW) into the Arctic Ocean, shaping the regional water and heat budgets and tightly coupling with sea-ice melt-freeze cycles and freshwater export. Using long-term mooring observations from four sections spanning the Eurasian Basin-from Fram Strait to the Laptev Sea and applying empirical orthogonal function (EOF) analysis, we examine the evolution and spatiotemporal variability of the ACBC. Results show that along its cyclonic pathway the Fram Strait branch exhibits a gradual weakening and a deepening of the velocity core. Injection from the Barents Sea branch generates a shelf-edge jet at the Svalbard section, with peak speeds up to 35 cm/s. Volume transport decreases along the path, from (3.45±0.26) Sv at Fram Strait to (2.79±0.23) Sv at the Laptev Sea, and the heat flux likewise diminishes across successive sections. The current displays pronounced seasonality—stronger in winter than in summer-closely linked to the strength of AW inflow. These findings clarify the characteristics and variability of the ACBC within the Eurasian Basin, provide an assessment of its structure, and contribute to a deeper understanding of the Arctic Ocean’s overall state and governing mechanisms.