Water mass exchanges between the Norwegian and Iceland seas over the Jan Mayen Ridge using in-situ current measurements

The Jan Mayen Ridge, with bottom depths of 1000 m and less, runs southwards from Jan Mayen and separates the warmer and saltier Atlantic Water in the Norwegian Sea from the colder and fresher Arctic water in the Iceland Sea. During the International Polar Year (IPY, 2007-2008), three current meter moorings were deployed with the purpose to investigate water mass exchanges between the Norwegian and Iceland seas over the Ridge and their forcing mechanisms. These are the first in-situ current measurements for this region. The results showed relatively weak currents on the Ridge that frequently shifted direction except near-bottom and at the western slope of the Ridge. All current measurements showed low eddy activity and tidal velocities (less than 0.05 ms− 1). Wind-forced near-inertial motion generated from transient atmospheric low pressure systems were observed in the mixed layer being strongest during autumn and winter when ocean velocities reached 0.7 ms− 1. Near surface currents on the Ridge are influenced by local winds on a time scale of 6 days and longer, but during the two-year deployment no pronounced seasonal variation was observed, mainly due to a lack of seasonality in the local winds. In a 2000 m deep channel that cuts the Ridge, there was pronounced seasonal variation in the currents at all depths below 40 m with stronger flow toward the Iceland Sea during winter compared to summer. The variability of the deep current was found to be influenced by the large-scale wind stress curl. There was a weak net flow with averaged velocities of ~ 0.01 ms− 1 over the Ridge that was directed westward in the upper layer, signifying a small net transport of modified Atlantic Water into the Iceland Sea.