An advanced coupled modelling system to study interactions among the circulation, sea ice, and biogeochemistry in the Northwest Atlantic Ocean

The Northwest Atlantic (NWA) plays a critical role in the global ocean circulation and regulates the global climate system through meridional transport in western boundary currents as well as through deep convection. Global climate change is projected to significantly impact ocean circulation, vertical mixing, and sea ice dynamics in the NWA, with important implications for the area’s biological productivity and carbon export. These physical and biological features and their variabilities are challenging to numerical ocean models and often poorly represented in global climate models. This creates a difficulty in projecting future changes in nutrient dynamics, production, and carbon export. To address these challenges we have developed an advanced coupled circulation-sea ice-biogeochemistry modelling system for the NWA. This modelling system is based on the Regional Ocean Modeling System (ROMS), the Community Sea Ice Model (CICE), and a biogeochemical model including oxygen dynamics and carbon chemistry. The model domain spans the area from Cape Hatteras to Baffin Bay and from the east coast of North America to the central North Atlantic, with the horizontal grid resolution ranging from ~8 km in the south to ~2 km in the north. The circulation and sea ice models are forced by atmospheric and oceanic reanalysis data at the surface and lateral boundaries, respectively. The circulation model is additionally forced by tides, river discharge, and continental runoff. Preliminary model results are presented and compared to various types of observations, with a focus over coastal waters and the deep convection region of the Labrador Sea.