Transport variability of the Irminger Current: First year-round results from a mooring array on the Reykjanes Ridge.

The Irminger Current on the Reykjanes Ridge transports warm and saline Atlantic Water northward in the subpolar gyre and hence forms an important component of the upper warm limb of the AMOC. Volume and heat transports have - up to now - principally been based on analysis of summer hydrographic data combined with satellite surface velocities. Here we present the first year-round volume and heat transport estimates based on the full-depth mooring array on the western flank of the Reykjanes Ridge between 2014 and 2015. These estimates are compared with results based on shipboard data from the early 1990s and the early 2000s when two contrasting modes of transport variability were seen through the appearance of a second deep core of the Irminger Current. The results of the newly obtained continuous measurements initially show two clear bottom intensified cores in the flow field. However, during the deployment period the Irminger Current showed increased variability in shape and strength during the winter 2014-2015. This change happened in concert with a return from a highly stratified Irminger basin in 2014 to a basin that was filled with cold and fresh LSW-like water in 2015. All in all the situation in 2015 was very reminiscent of the conditions that were seen in the early 1990s in the Irminger basin. These results are further explored in light of atmospheric circulation, a strong positive NAO and the strong winter of 2014-2015 causing record deep convection in the central Irminger Gyre.