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Abstract:
The Atlantic Water, entering the Arctic through the Barents Sea and Fram Strait, is the main source of nutrients in the Arctic Ocean. The Barents Sea is divided by the polar front into an Atlantic-dominated domain in the south, and an Arctic-dominated domain in the north. The polar front is a thermohaline structure, which is topographically-steered at sub-surface, and influenced by the seasonal sea ice edge near the surface. Exchanges of nutrients between the inflowing Atlantic Water and the surrounding waters are key for the primary production in the Barents Sea. In October 2020, we measured nutrients, dissolved inorganic carbon (DIC), ocean stratification, currents and turbulence in the vicinity of the polar front in the Barents Sea within the framework of the Nansen Legacy project, allowing estimates of horizontal and vertical advective fluxes and turbulent fluxes of nitrate and DIC. We found a substantial transfer of nitrate and DIC across the polar front from the Atlantic domain to the Arctic domain. Up to one quarter of the replenishment of the nitrate in the mixed layer during winter could be attributed to vertical mixing, shared approximately equal between advective and turbulent fluxes, of sources from the subsurface Atlantic Water to the surface during wind events. We also identified an export of nitrate and DIC occurring along the eastern shelf of Svalbard, feeding part of the deep convection occurring in Storfjorden. Our observations of nutrient fluxes are representative of the autumn conditions in the Barents Sea when the primary production is the lowest.
