The circulation near the Reykjanes Ridge in summers 2015, 2016 and 2017

Abstract

<p>Located south of Iceland, the Reykjanes Ridge is a major topographic structure of the North Atlantic Ocean that strongly influences the spatial distribution and circulation of the North Atlantic Subpolar Gyre water masses. Around the ridge, the circulation is composed of two main along-ridge currents, the southwestward East Reykjanes Ridge Current (ERRC) in the Iceland Basin and the northeastward Irminger Current (IC) in the Irminger Sea. To study the along Reykjanes Ridge flow variability and the inter-basin connection through the ridge and connections with the interior of each basin, volume and water mass transports over the Reykjanes Ridge during summer 2015, 2016 and 2017 are analyzed. Data used are velocity and hydrographic measurements carried out along and perpendicular to the crest of the Reykjanes Ridge during the RREX (Reykjanes Ridge Experiment Project) cruises in June–July 2015 and June–July 2017 and BOCATS cruise in July 2016. The new circulation scheme in the area described in 2015  by Petit et al. (J. Geophys. Res., 2018) with flows connecting the ERRC and IC branches at specific locations set by the bathymetry of the ridge is again observed  in 2016 and  2017, with variations concerning the connections with the interiors of the basins. The data set reveals remarkable changes in the hydrological properties and transports of the ERRC, IC and cross ridge flows. The westward transport across the ridge, which represents the subpolar gyre intensity, was estimated at -19.6±3.4 Sv in 2015 and -35.2±3 Sv in 2017. A freshening and a decline in density mainly affecting the Subpolar Mode Water was observed in 2017. It was associated with a lower mode water  transport partly compensated by a higher transport of intermediate and Arctic waters. We further document each water mass contribution to the westward flow of the gyre and the structure of the ERRC and IC.</p>