Meridional overturning and oceanic heat transport circulation observations in the North Atlantic Ocean [in “State of the Climate in 2016”]

This section describes the AMOC and the Atlantic meridional heat transport (AMHT), determined by the large-scale ocean circulation wherein northward moving upper layer waters are transformed into deep waters that return southward, redistributing heat, fresh water, carbon, and nutrients. Large variations in meridional heat transport are associated with strong MOC anomalies (e.g., correlations of 0.94, Johns et al. 2011) and northwesterly wind anomalies while monthly variability is more closely linked to the spatial structure associated with the North Atlantic oscillation (NAO; e.g., Moat et al. 2016). Observed cold North Atlantic sea surface temperatures were consistent with the decadal decrease in MOC transport at 26°N (e.g., Baringer et al. 2016). These large-scale ocean anomalies can subsequently impact European weather (e.g., Duchez et al. 2016). Many climate, weather, and ecosystem changes covary with changes in the AMOC (e.g., Srokosz and Bryden 2015; Carton et al. 2014; Srokosz et al. 2012).