Observations of mesoscale variability in the Rockall Trough

The Rockall Trough west of Ireland displays a high level of mesoscale activity for an eastern ocean boundary region. Eddies off the continental slope at 50–56°N have been studied using a combination of in situ observations of current velocity and hydrography from two deep-sea moorings at the southern entrance to the Trough, and data from satellite altimetry and Argo floats. South of Rockall–Hatton Plateau, where a branch of the NAC enters the region from the west, more cyclonic eddies are found, while anticyclonic eddies dominate along the path of the Slope Current in the east. Temperature–salinity profiles from the perimeters of a cyclone and an anticyclone, respectively, show large differences on isopycnals both at the level of the subsurface salinity maximum and at intermediate depths. Anticyclonic eddies likely formed by instabilities of the Slope Current can include a parcel of salty Mediterranean Water (MW) at the intermediate level, contributing to the patchy distribution of MW in the region.