No abstract

Surface geostrophic velocity fields derived from satellite altimetry between January 1993 and April 2014 are used to detect and investigate eddies in the North Atlantic between 40°N–55°N and 60°W–10°W. Focus is on a zonal section along 47°N, roughly at the boundary between the subpolar and the subtropical gyres. Sea surface temperature data are used to quantify the temperature anomalies associated with eddies and the respective surface temperature fluxes related to these eddies. Identified eddy pathways across 47°N are related to the mean background velocity from full‐depth ship observations carried out on 11 cruises between 2003 and 2014. The analysis is repeated in two model simulations with 1/4° and 1/12° horizontal resolution, respectively, for the period 2002–2013. The analysis reveals almost 37,000 altimeter‐derived eddies with a lifetime longer than 1 week in the area. The highest number of eddies is found along the pathway of the North Atlantic Current, roughly following the 4000 m isobath, and on the Grand Banks of Newfoundland. Time series of temperature fluxes by eddies crossing 47°N reveal that single isolated eddies with large SST signatures contribute ∼25% to the surface temperature flux. Relating the observed eddies to the observed top‐to‐bottom velocity distribution at 47°N points to the existence of eddy pathways across 47°. The highest‐temperature fluxes are linked to the fastest and most pronounced current branches in the western Newfoundland Basin. While there are fewer eddies in both model simulations, the key findings are consistent between the observations and the two model simulations.

A new data set of temperature and salinity fields reconstructed from satellite altimetry data between January 1993 and April 2014 is combined with satellite observations of mesoscale eddies in the subpolar North Atlantic between 40°N–55°N and 43°W–20.5°W. The data set is used to calculate the meridional heat and freshwater transports related to the propagation of eddies crossing 47°N, a latitude close to the boundary between the subpolar and the subtropical gyres. The largest heat and freshwater transports by eddies are observed in the western part of the Newfoundland Basin. Around 35–45% of the heat and freshwater transports by eddies across 47°N stem from individual isolated eddies with large thermohaline signatures. Northward moving cold and fresh cyclonic eddies carrying subpolar water from the Western Boundary Current make a considerable contribution to the overall heat and freshwater transport by eddies crossing 47°N. While the transport by individual eddies is negligible compared to the transport by the mean flow in this region, it can have a notable influence on the temporal variability. The analysis is repeated for a model simulation with 1/12° horizontal resolution for the period 2002–2013. The observed results are well reproduced in the model simulation; in particular, the modeled number of eddies crossing 47°N, the spatial distribution, and the associated heat and freshwater transports across this latitude are consistent with the observations.