Paleotemperature of the Canadian Atlantic Shelf intermediate water as a proxy for the Atlantic Meriodional Overturning Circulation

Abstract

The Atlantic meridional overturning circulation (AMOC) is a key component of the global climate system as it transports warm waters to the high latitudes which allow the formation of intermediate and deep Atlantic water masses. Models have predicted a slowdown, or even a collapse of the AMOC under current global warming and increased freshwater flux. Until recently the AMOC intensity beyond the last century mostly unknown. Only a few studies managed to develop reliable paleo reconstruction of the AMOC but all highlighted the uniqueness of the present weakening over the last 1,000 to 1,500 years. Here, we present the results from the western North Atlantic, where we tested the link between the 18O of benthic foraminifers from a sediment cores collected in the Laurentian Channel and the AMOC strength. Using a sediment core covering the last century, a warming of 1.7°C during the twentieth-century was observed in the St. Lawrence bottom water and was attributed to a decrease of the proportion of cool Labrador Subarctic Slope Water entering the Laurentian Channel linked to the decrease of the AMOC intensity. This high-resolution reconstruction of the AMOC aligns very well with the modelled AMOC index developed in 2015 by Rahmstorf et al.