Two Sources For The Lower Halocline In The Arctic Ocean

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The lower halocline in the Amundsen and Makarov Basins of the Arctic Ocean is derived from the inflow from the Norwegian Sea through Fram Strait which interacts with sea ice to become fresher and colder, creating a deep winter mixed layer in the Nansen Basin that eventually supplies the lower halocline. The near surface inflow from the Norwegian Sea through the Barents Sea incorporates the run-off from the large Siberian rivers. It contributes to the Polar Mixed Layer, capping the denser mixed layer formed from the Fram Strait inflow. The main inflow from the Norwegian Sea over the Barents Sea enters the Arctic Ocean at the St. Anna Trough and its upper part provides a second source for the lower halocline. In the Nansen Basin this Barents Sea branch contribution to the halocline is as cold as the Fram Strait contribution but more saline. Further to the east it remains more saline, but becomes warmer than the Fram Strait derived lower halocline. This is a result of stronger vertical mixing and entrainment over the continental slope. The Barents Sea branch component, initially confined to the Siberian continental slope, eventually becomes the main source of the lower halocline in the Canada Basin beyond the Chukchi Cap.