Trends and Transport Variability of the Circulation in the Subpolar Eastern North Atlantic

Abstract

AbstractThe North Atlantic Current is the major pathway for warm and saline water from the subtropics into the subpolar North Atlantic. Its main branch crosses 47°/48°N in the western North Atlantic basin and further north the Mid‐Atlantic Ridge (MAR) before entering the eastern subpolar basin where it partly feeds the subpolar gyre. To quantify the meridional exchange of water between the subtropical and subpolar regime in the interior eastern North Atlantic, long‐term (1993–2017) transport time series were calculated by combining data from inverted echo sounders taken in 2016–2017 with the dynamic topography from satellite altimetry. The data reveal an additional more direct pathway from the south across 47°/48°N with a mean northward transport of 9.1 Sv ± 0.8 Sv contributing about 22% to the total inflow of 41.4 Sv into the eastern subpolar basin. The transport time series of this pathway is significantly anticorrelated to the zonal transport across the MAR (R = −0.7), damping the interannual variability of the total transport into the subpolar eastern North Atlantic. Moreover, for the meridional transport in the interior eastern basin, a positive trend of 2.0 Sv ± 1.5 Sv per decade is found, partly balancing the negative decadal trend of −6.0 Sv ± 5.7 Sv observed in the interior western basin.