Processes Governing the Location and Depth of Convection in the Labrador Sea – Lessons Learned from an Idealized Model Study

Abstract:

The Labrador Sea is one of the few locations in the world’s oceans where deep convection occurs. The convectively-formed Labrador Sea Water (LSW) contributes to the lower limb of the Atlantic Meridional Overturning Circulation (AMOC). In light of its link to the AMOC, it is important to understand the annual cycle of Labrador Sea convection and restratification, and the role that both atmospheric and oceanic conditions play for the formation of LSW.

Convection in the Labrador Sea is highly variable in time, and observations indicate that also the location of deepest convection varies. It is obvious that the atmospheric heat loss is an important factor in governing these characteristics of wintertime convection. However, the story is probably more complicated than that. Over the year, the Labrador Sea loses heat to the atmosphere, and this loss is compensated by lateral eddy buoyancy fluxes originating from the boundary current. This implies that variations in the pattern and magnitude of these eddy fluxes may play a role as well for setting the preferred convection sites.

In this study, a highly idealized model is applied to investigate the competing impacts of surface heat loss and lateral buoyancy fluxes in setting the characteristics of Labrador Sea convection, and to assess how sensitive the convection is to variations in these two processes. In particular, the impacts of Irminger Rings shed near Greenland’s west coast are highlighted.