Generation and Propagation of Eastern Subpolar North Atlantic Salinity Anomalies

Abstract

The Eastern Subpolar North Atlantic (E‐SPNA) upper ocean experiences pronounced interannual salinity variations that influence the global overturning circulation, yet a quantitative understanding of their life cycle remains lacking. Based on an ocean circulation state estimate, we combine budget analysis with particle tracking to quantify the generation and propagation of E‐SPNA salinity anomalies. Analyzing salinity for each day between 1992 and 2017 reveals that changes in circulation, forcing, and stratification contribute similarly to interannual salinity variability. Most anomalies originate within 2 years prior to entering the E‐SPNA, near the Grand Banks and along the North Atlantic Current (NAC). Two salinity extremes are also examined. The 2016 E‐SPNA fresh event primarily resulted from circulation changes near the Grand Banks, with a smaller contribution from vertical diffusion at its onset, whereas the 2007 E‐SPNA salty event arose from a combination of dry atmospheric conditions and Subtropical Gyre expansion along the NAC.