"Transport and Variability of the Irminger Current between 2014 and 2015"

Abstract

The Irminger Current, a branch of the North Atlantic Current, carries warm and saline waters poleward in the subpolar gyre and as such contributes to the upper limb of the Atlantic Meridional Overturning Circulation (AMOC). Previous estimates about its volume transport and variability have been mostly based on summer hydrographic sections in combination with satellite data. Presented here are the first year-round results from a full-depth mooring array located on the west side of the Reykjanes Ridge between 2014 and 2015. These results are mainly compared with hydrographic and velocity data from summers 2014 and 2015 and shipboard measurements from the early 1990s and 2000s, where the shift in atmospheric forcing resembles that of winter 2014-2015. Differences in the shape and strength of the Irminger Current are large during this one-year period. The IC is highly variable on scales varying from 7 to 35 days. Changes in the velocity field during the winter state are distinct and occur concurrently with record deep convection in the Irminger Gyre. The spatial resolution of the moorings is found to be likely too coarse to capture the full transport of the Irminger Current. Additional data from oceanic moorings from a French campaign will help to resolve this in the future. These first year-round results show that the Irminger Current is much more variable than earlier thought, particularly during winter.