Freshwater fluxes and variability in the Arctic Ocean and subarctic North Atlantic

As salt is largely conserved in the oceans globally, the only way to change the ocean salinity, which is key to many ocean processes by setting density stratification, is by adding or removing fresh water. Significant freshwater changes have recently been observed both in the Arctic Ocean and the subpolar North Atlantic. From observations between 1990 and 2013, we found a distinct anti-correlation of the freshwater anomalies in the upper Arctic Ocean and the subarctic North Atlantic (SANA) with anomalies of almost the same magnitude.
\nAnalyses of freshwater fluxes from the global Finite Element Sea ice Ocean Model (FESOM) and the Common Ocean-ice Reference Experiment version 2 (CORE-II) atmospheric forcing data set suggests that the freshwater variations in the two regions largely result from changing advective freshwater transports. Variations in the Arctic freshwater export to the North Atlantic are found to be most important for the total freshwater content variability of the upper Arctic Ocean and for the liquid freshwater content variability of the western SANA. The eastern SANA freshwater content seems to be mainly influenced by the exchange with the subtropical North Atlantic.
\nFurthermore these changes are correlated with large-scale atmospheric pressure and circulation patterns. Based on regression analysis we isolate two distinct patterns of sea level pressure with one being associated with the southward volume transport through the Canadian Arctic Archipelago and the other with the southward volume transport through Fram Strait. We propose, that the recently observed rapid changes of freshwater content in the SANA and upper Arctic Ocean resulted from an interplay of these two driving patterns causing parallel changes in the freshwater export on both sides of Greenland.
\nAccording to our freshwater content time series and the present sea level pressure pattern, the fresh water that accumulated in the Arctic Ocean during the previous decades has started to be released into the SANA in the most recent years. If continued in the following years, the freshwater export will have impact on the stability of the upper water column both in the Arctic Ocean and the SANA with possible implications for the Atlantic Meridional Overturning Circulation and the oceanic heat release to the Arctic atmosphere and sea ice.

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