Interannual Variability in the Oxygen Budget of the Subpolar North Atlantic Ocean

In the face of ocean warming and increasing demand for oxygen by marine animals, it is imperative to understand the climate-induced variability of the ventilation of the ocean interior. Estimates of contemporary air-sea fluxes indicate that the subpolar North Atlantic Ocean is one of the most intense regions of gas exchange in the global ocean. Deep convection in the subpolar gyre is driven by strong winds in combination with wintertime cooling and transports ocean surface signals to depth. The formation and circulation of Labrador Sea Water, characterized by high concentrations of dissolved gases, is thought to play a large role in ventilating the intermediate and deep waters of the North Atlantic. However, despite recent efforts to more quantitatively observe the oxygen content of intermediate waters, little is known about its variability over the past decades and how this relates to changes in ocean water mass properties and circulation. We utilize a novel coupled model, ASTE-BLING, to evaluate the response of the North Atlantic oxygen budget to recent climate variability. Derived from the MITgcm-based ECCO ocean reanalysis, ASTE is a regional 1/3º state estimate that assimilates in situ and satellite observations to reconstruct the ocean and sea ice time-mean and evolving state. The BLING model is coupled to ASTE to simulate the oxygen and carbon cycles using a low complexity biogeochemical cycle. Using ASTE-BLING, we resolve air-sea exchange in the subpolar North Atlantic to establish a process-based understanding of the mechanisms that determine oxygen uptake and its temporal and spatial variability. We also consider variations in the North Atlantic Oscillation as an indicator of interannual variability in the regional oxygen budget.