Wintertime <em>f</em>CO₂ variability in the Subpolar North Atlantic since 2004

International audienceWinter data of surface ocean temperature (SST), salinity (SSS) and CO$_2$ fugacity (fCO$_2$) collected on the VOS M/V Nuka Arctica in the subpolar North Atlantic between 2004 and 2017 are used to establish trends, drivers, and interannual variability. Over the period, waters cooled and freshened, and the fCO$_2$ increased at a rate similar to the atmospheric CO$_2$ growth rate. When accounting for the freshening, the inferred increase in dissolved inorganic carbon (DIC) was found to be approximately twice that expected from atmospheric CO$_2$ alone. This is attributed to the cooling. In the Irminger Sea, fCO$_2$ exhibited additional interannual variations driven by atmospheric forcing through winter mixing. As winter fCO$_2$ in the region is close to the atmospheric, the subpolar North Atlantic has varied between being slightly supersaturated and slightly undersaturated over the investigated period