A study on mesoscale eddies in the Irminger Sea and Iceland Basin using high resolution mooring data and satellite altimetry

Abstract

The Irminger Sea and Iceland Basin are the main regions of deep water formation which feed the lower limb of the Atlantic Meridional Overturning Circulation (AMOC). This deep water formation occurs due to deep convection in winter and restratification in summer. Changes in stratification have far-reaching effects on the deep water formation, ultimately impacting the climate of western Europe and the North Atlantic region. Ocean eddies transport different water masses through the entire ocean outside of large scale circulations. They have the potential to transport buoyant water to the convection region, therefore impacting restratification. In this study we use six years of high resolution mooring observations in the Irminger Sea to determine the vertical and horizontal structures, temperature and salinity of anticyclonic eddies. Additionally, we employ a global dataset of eddies tracked through satellite altimetry to analyze the horizontal structures and propagation of eddies across the eastern subpolar North Atlantic. Twelve eddies have been detected through mooring observations. We find that eddies at the mooring reach depths of up to 850 m with salinity between 35.02 g/kg and 35.15 g/kg and temperatures between 5.0° and 6.6°C. The radii of mooring detected eddies lie between 16.5 km and 33.1 km. Based on our analysis of globally tracked eddies using satellite altimetry, we observe no discernible distinction in the characteristics of anticyclonic eddies between the Irminger Sea and Iceland Basin in a mean over a 30-year period. The tracked eddies have a mean radius of 34 km and a mean lifetime of 60 days. They mainly travel westward over the span of their lifetime. Eddy propagation is influenced by strong currents and shallow topography, but independent of the background flow in the basin interior. The findings in this study enhance our understanding of the characteristics and dynamics of anticyclonic eddies in the Irminger Sea and Iceland Basin. The insights gained from this research need yet to be linked to stratification and convection.