Impact of Synoptic-Scale Atmospheric Forcing Conditions on Deep Convection in the Labrador Sea

Abstract

During the winter season, stratification in the central Labrador Sea is eroded by surface heat fluxes causing convective overturning exceeding depths of 2 km. This is one of the few locations globally in which deep convection occurs, making it an important feature of the climate system and ocean ventilation. Large-scale atmospheric circulation patterns modulate the air-sea interaction that drives the loss of ocean buoyancy. Here, we investigate the process by which weather patterns driven by the North Atlantic Oscillation (NAO), and its northern center of action, the Icelandic Low, modulate convective depths. A one-dimensional ocean model is used to quantify the mixed layer depth's response to various atmospheric forcing conditions. We find that while net heat flux is the strongest modulating factor of mixed layer depth's seasonal maximum, it is also strongly affected by the NAO. The Icelandic Low, despite its proximity to the Labrador Sea, does not affect mixed layer deepening as strongly. From geospatial correlation fields with heat flux, NAO, and Icelandic Low time series, it is evident that the NAO more efficiently regulates strong, cold, westerly winds from over the North American continent, which are more effective at cooling the ocean surface boundary layer. Understanding these dynamics is crucial for predicting future changes in ocean ventilation and its impact on global climate patterns.