Quantifying Atlantic Water transport to the Nordic Seas by remote sensing

In this study the variability of Atlantic Water (AW) entering the Nordic Seas from the North Atlantic through the passage between Iceland, the Faroe Islands and Scotland has been investigated. The poleward transport of this warm AW is a key component in maintaining a relatively mild climate in the northwestern Europe. Satellite remote sensing datasets from altimetry and the Gravity field and steady state Ocean Circulation Explorer (GOCE) mission, in combination with surface drifters, fixed current meter, and hydrographic data are used. The high-resolution mean dynamic topography (MDT) is shown to resolve the time-invariant surface currents in the inflow region. In addition to the improved MDT, we take benefit of the new reprocessed sea level anomaly data in the estimation of absolute dynamic topography. Analysis of the monthly surface velocities from 1993 to 2016 demonstrates significant influence of the large scale atmospheric forcing associated with the North Atlantic Oscillation (NAO). Furthermore, a significant increase in surface velocities along the slope current, front current and the Norwegian Coastal Current are found during winter. Finally, combining altimetry with hydrographic data, we demonstrate that the variability in surface velocities of the inflow region is also reflected in the deeper layers, and that altimetry therefore can be used to monitor the variability of the poleward transport of AW in this region. •The GOCE MDT reproduced all main features of circulation in the inflow region.•Significant increase in the surface velocities of the inflow region during winter•Significant impact of NAO on the surface velocities of the slope current•Surface variability of the slope current is also reflected in its deeper layers.•Increased volume transport along the slope current during positive NAO events