The Interannual Variability of Oxygen in the Labrador Sea

The Labrador Sea (LS) is one of the few regions in the global oceans where open-ocean deep convection occurs producing the Labrador Sea Water (LSW) that spreads across the subpolar North Atlantic. Thus the LS is a key region where the deep ocean takes up heat, oxygen and carbon dioxide from the atmosphere. Convective events in the LS have shown significant inter-annual to decadal variability over the past 60 years, as revealed by the historic measurements. However, state-of-the-art Earth System Models (ESMs) cannot correctly reproduce the spatio-temporal variability of the LS convection and its statistical properties. The objective of this study is to better understand the physical and biogeochemical processes that regulate the variability of LS convection and its dissolved gas tracers using a mesoscale permitting simulation. The regional integration of the LS circulation is obtained using ROMS configured at a 5km horizontal resolution for the period 1950-2010. The model output is compared to recent ARGO floats at intraseasonal to interannual timescales and to the historic observations on decadal timescales. It reproduces the observed T/S variability remarkably well and provides an excellent platform to investigate the controls of the regional biogeochemical cycling. A suite of sensitivity experiments illustrates the regulation of air-sea gas fluxes during strong and weak convective winters quantifying the relative importance between diffusive and bubble mediated air-sea gas transfers.