Lofoten eddies observed by Seagliders

Abstract

When the Norwegian Atlantic Current passes the Lofoten Basin, it loses a large amount of mass and heat to mesoscale eddies as a result of instabilities of the mean current along the Norwegian Slope. The eddies subsequently propagate into the interior of the Lofoten Basin, where they are trapped by the topography, making the basin the most energetic with the largest pool of Atlantic Water in the Nordic Seas. Observational studies have been limited, mainly to surface signature inferred from remote sensing data. This study investigates mesoscale eddies in the Lofoten Basin using Seaglider observations taken from 2012 to 2017 and an altimetryderived dataset that characterizes eddies based on the surface signature. Nine anticyclones and two cyclones have been characterized using Seaglider data. Eddies in the basin have a mean radius and velocity maximum of 19 km and 0.4 m s^−1. The Anticyclones have a mean anomalous heat content, available potential energy and eddy kinetic energy of 14.0 × 10^18 J, 15 × 10^13 J and 9 × 10^13 J. Cyclones of −8 × 10^18 J, 10 × 10^13 J and 14 × 10^13 J. The slope branch of the Norwegian Atlantic Current have been identified as the source region, and a freshening of anticyclones in the observation period was observed. The altimetry-derived dataset showed a pattern of eddies being generated along the continental slope on the eastern border of the basin and moving in a cyclonic pattern around the basin. The number of eddies required to balance wintertime heat loss from the basin was found to be 28 to 37.