Eddy-induced Temperature Exchange between the Subpolar and the Subtropical Gyre of the North Atlantic
Vasco Müller1, Dagmar Kieke2, Paul Glen Myers3, Christian Mertens2 and Clark William Pennelly4, (1)University of Bremen, MARUM - Center for Marine Environmental Sciences, Bremen, Germany, (2)University of Bremen, Bremen, Germany, (3)University of Alberta, Edmonton, AB, Canada, (4)University of Alberta, Earth and Atmospheric Sciences, Edmonton, AB, Canada
Abstract:
The focus of our work is on interactions between the subpolar and subtropical gyre of the North Atlantic. We examine the role of eddies on temperature fluxes exchanged across the front between the two gyres. We ask where and how horizontal mixing takes place, if there are localized hotspots of mixing, and what are the main pathways of eddies exchanged between the gyres.A geometry based algorithm for the detection and tracking of eddies is applied to geostrophic velocities derived from satellite altimetry between January 1993 and April 2014. The velocity fields are resolved daily on a 1/4° horizontal grid. To estimate the respective temperature flux of individual eddies, the inferred surface areas and translation speeds of the eddies are combined with anomalies of sea surface temperature (SST).For the analysis of the temperature flux, we focus on the latitude 47°N as it represents a good approximation for the boundary between the two gyres. Additionally, we use top-to-bottom velocity observations from 10 cruises carried out approximately along this latitude between 2003 and 2014. These allow us to relate the eddy temperature fluxes to the major circulation branches in this region.Time series of eddy temperature fluxes reveal single eddies with large SST signatures that are responsible for a large part (~20%) of the total eddy temperature flux across 47°N. A comparison to ship-based velocity measurements shows that the region of highest eddy activity is located in the region of high shear between the Western Boundary Current, the North Atlantic Current, and the recirculation cell in the Newfoundland Basin.
