By the end of this century, the Oceans will markedly change in response to anthropogenic stressors and increasing greenhouse gas emissions. Their circulation and the horizontal and vertical transport of heat, salt, carbon, oxygen and nutrients will be impacted. In response to rising temperatures, stratification will increase in the upper water column, affecting ventilation of the deep ocean and nutrient transport from the deep and nutrient-rich waters to the euphotic layer. Seawater will become more acidic as well, as atmospheric carbon dioxide is taken up by the ocean and redistributed by its circulation, and will lose oxygen. The global oceans are replenished by newly ventilated water to depths far greater than the euphotic layer only in few, high latitude areas where open ocean deep convection and deep-water formation occur. In the North Atlantic (NA), the Labrador Sea (LS) is one of such regions, and the best observed. Predicting the evolution of the ocean circulation and marine ecosystem changes in the North Atlantic is therefore central to understand the future climate trajectory. This thesis presents an analysis of state-of-the-art Earth Systems Models (ESMs) included in the Coupled Model Intercomparison Project Phase 5 (CMIP5) and investigates their skill in representing the physics and biogeochemistry of the subtropical and subpolar NA regions and their evolution at centennial timescales. Attention is paid to oxygen and nutrient inventories, and to the mechanisms that regulate the changes of oxygen and nutrients. Additionally, simulations by a state-of-the-art high-resolution regional ocean model are performed and analyze to quantify how and how much ocean turbulence impacts deep convection and oxygen and carbon drawdown in the LS.