Sub-Mesoscale Modelling of the Labrador Sea

Clark William Pennelly, University of Alberta, Earth and Atmospheric Sciences, Edmonton, AB, Canada and Paul G. Myers, University of Alberta, Department of Earth and Atmospheric Sciences, Edmonton, AB, Canada
The Labrador Sea is a very dynamic region, with physical processes occurring at a variety of scales, from large-scale gyre circulation to small-scale convection. These small scale features are often difficult to resolve due to the expensive computing costs associated with high resolution modelling. We use an ocean model, NEMO, with the Adaptive Grid Refinement in FORTRAN (AGRIF) nesting software to implement two nests, achieving 1/60° (1 km) horizontal resolution in the Labrador Sea. We force our simulation with a high spatial (30km) and temporal (hourly) atmospheric forcing product, the Global Deterministic Prediction System produced by the Canadian Meteorological Centre, with forcing onwards from 2002. This computationally-efficient setup allows a lengthy high-resolution simulation that is capable of resolving the important sub-mesoscale processes in the Labrador Sea.

We will showcase over a decade of results that illustrate the need for high resolution in this region, particularly as it impacts the spatial and vertical extent of deep convection. Irminger Rings, eddies shed from the west coast of Greenland, are tracked and investigated. These eddies evolve as they travel into the interior of the Labrador Sea, carrying a significant amount of buoyancy that coarser resolution simulations often misrepresent. These eddies, as well as other mesoscale features, influence the production of Labrador Sea Water, an important component of the Atlantic Meridional Overturning Circulation. Four passive tracers have been included and will be discussed: Greenland runoff, Canadian Arctic outflow, Labrador Sea Water produced during convection, and Irminger Water which flows west past Cape Farewell.