Impacts of the hydrological cycle on the subpolar North Atlantic upper ocean salinity variability

The subpolar North Atlantic (SPNA) is a critically important region of the global ocean as it is one of just a few locations where surface waters can sink to deep depths. This sinking helps drive the Atlantic Meridional Overturning Circulation (AMOC) – the engine of the global ocean thermohaline circulation (THC). Upper ocean salinity in this region plays a major role in seawater density which helps drive the AMOC and eventually the global THC. Our previous work brought to light a connection between the subtropical North Atlantic poleward water vapor transport in the atmosphere and its impact on the SPNA hydrological cycle and near-surface salinity variability. This study advances on that previous work by examining what kind of impact the SPNA hydrological cycle (namely evaporation minus precipitation [E-P]) has on salinity in multiple locations across the SPNA, and how its impact compares to advection on decadal (1985-1994, 1995-2004, and 2005-2017) to multi-decadal time scales (1985-2017). The study is based on the recently released World Ocean Atlas 2018 (salinity), the Simple Ocean Data Assimilation (SODA) version 3.3.1 (advection), the Objectively Analyzed air-sea Fluxes (OAFlux) project (evaporation), and the Global Precipitation Climatology Project (GPCP) (precipitation). We find that E-P and advection's relative influence on upper ocean salinity changes on decadal time scales and by geographic location within the SPNA (e.g., Labrador Sea vs Irminger Sea). Major results and their potential implications for understanding long-term upper ocean salinity changes will be discussed.