Recirculation of Canada Basin Deep Water in the Amundsen Basin, Arctic

It is evident from hydrographic profiles in the Arctic Ocean that relatively warm and salty Canada Basin Deep Water (CBDW) flows over the Lomonosov Ridge into the Amundsen Basin, in the Eurasian Arctic. However, oceanographic data in the deep Arctic Ocean are scarce, making it difficult to analyse the spatial extent or the dynamics of this inflow. Here we present new hydrographic data from two recent expeditions as well as historical data from previous expeditions in the central Arctic. We use an end-member analysis to quantify the presence of CBDW in the Amundsen and Nansen Basin and infer new circulation pathways. We find that the inflow of CBDW is intermittent, and that it recirculates in the Amundsen Basin along Gakkel Ridge. Although the forcing mechanisms for the inflow of CBDW into the Amundsen Basin remain unclear owing to the lack of continuous observations, we demonstrate that density-driven overflows, even intermittent, and the pressure gradient across the Lomonosov Ridge are unlikely drivers. We also find multiple deep eddies with a CBDW content of up to 600 g kg-1 and a vertical extent of up to 1200 metres in the Amundsen Basin. The high CBDW content of these eddies suggests that they can efficiently trap CBDW and transport its heat and salt over long distances.