| Summary: | The processes driving the seasonal variability of the mixed layer salinity in the Arctic Ocean are investigated using a simulation performed with regional ocean – sea ice model at high resolution. While the seasonal variations of the mixed layer depth remain small, in particular under the perennial sea ice (O(30m)), the mean salinity of the mixed layer varies largely, with a seasonal cycle as high as 3 pss. On the shelves, where the sea ice is seasonal, the mixed layer is much fresher but exhibits a seasonal cycle with a similar amplitude. Overall, the seasonal variability of the mixed layer salinity results largely from a 1D vertical balance between the freshwater flux at the surface arising from the sea ice melt and freezing processes, and vertical mixing and entrainment occurring at the base of the mixed layer. The largest variations are found in summer, when the mixed layer is the thinnest. Over the shelves, this simple 1D balance is complexified due to the role of advection and river runoff that can locally affect the mixed layer depth and salinity. Interestingly, the largest variations are found less than 100km on each side of the sea ice edge, where all the processes affecting the mixed layer are amplified. This suggests the need to better observed and understand the ocean-sea ice-atmosphere exchanges in these regions.
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