Meridional Connectivity of a 25-year Observational AMOC Record at 47°N

Abstract

The Atlantic Meridional Overturning Circulation (AMOC) plays a key role for the climate system of Europe and the Arctic by redistributing heat and freshwater in the Atlantic. Since climate model studies project a likely decline of the AMOC under climate change in the 21st century, monitoring AMOC changes remains an important task. Several moored arrays in the Atlantic deliver estimates of the AMOC volume transport. The longest of these observational AMOC records is the RAPID array in the subtropical North Atlantic. The depiction of the AMOC as a global ocean conveyor assumes that the AMOC variability is consistent across latitudes. This concept has been questioned by model studies. However, model studies and estimates based on altimetry and Argo data disagree on the regions and timescales of meridional connectivity. From measurements of the North Atlantic Changes (NOAC) array in the subpolar North Atlantic at 47°N we calculate the AMOC volume transport timeseries. Our approach combines data from moored instruments with hydrography (from Argo floats and shipboard measurements) and satellite altimetry. Here, we present this 25-year (1993-2018) purely observational AMOC record in monthly resolution and analyze its meridional connectivity with the subtropical RAPID AMOC.