Atmospheric and Oceanic Sciences Departmental Seminar Series
Improving ice-ocean simulations of the Gulf of St. Lawrence for operational applications
a talk by
Canadian Centre for Meteorological and Environmental Prediction (CCMEP), Environment and Climate Change Canada (ECCC), Montréal, Canada
A hierarchy of operational prediction systems are being run at the Canadian Centre for Meteorological and Environmental Prediction (CCMEP) to produce daily analyses and forecasts of the physical properties of the ocean and sea ice (e.g. sea surface height, ocean currents and temperature, ice formation and motion). These systems combine the NEMO-CICE modeling framework with real time data assimilation. They are forced by or coupled to the atmospheric model GEM supporting operational weather analysis and forecast at CCMEP. A relatively seamless approach is applied to downscale our daily global ice-ocean analysis and forecast (1/4⁰ resolution) to a regional system (1/12⁰) in turn feeding high-resolution coastal simulations covering the Gulf St. Lawrence (GSL, 2 km – 500 m) and Estuary (100 m).
In the GSL, water masses evolve under a complex estuarine circulation. Continental freshwaters travel downstream at the ocean surface and mix with some of the cold Atlantic waters entering the GSL through Belle-Isle Strait (Labrador Current), and with some of the warmer and saltier Atlantic waters entering through Cabot Strait at depth in the Laurentian channel that crosses the continental shelf outside the GSL and connects to the Gulf Stream area. The density driven circulation is modulated by strong tidal flows interacting with a complex topography to mix water masses, and by the effect of an important seasonal cycle. A strong heat loss in fall and winter lead to the formation of a sea ice cover and a thickening of the cold intermediate layer (CIL, ~30-150m).
After a brief overview of our hierarchy of prediction systems, results from coastal simulations in the GSL are presented, focusing on the circulation and evolution of water masses. The importance of atmospheric forcing resolution (from 33 km to 2.5 km) is first examined, as wind channeling (intensity) in the Upper and Lower Estuary affects stratification and the CIL formation and penetration. At larger scale, as shown, parameters controlling bottom friction and turbulent kinetic energy at the ocean surface (wave breaking) also play an important role in predicting water masses and sea surface temperature, respectively.
(All collaborators on this project: François Roy1, Gregory C. Smith1, Audrey-Anne Gauthier2, Jean-Philippe Paquin1, Frederic Dupont1, Simon St-Onge Drouin3, Simon Senneville4, Jérôme Chanut5, Jean-François Lemieux1, Bruno Tremblay2/
1- Canadian Centre for Meteorological and Environmental Prediction (CCMEP), Environment and Climate Change Canada (ECCC), Montréal, Canada/ 2- McGill University, Montreal, Canada/ 3- Institut Maurice-Lamontagne, Fisheries and Oceans Canada, Mont-Joli, Canada/ 4- Institut des Sciences de la Mer (ISMER), Rimouski, Canada/ 5- Mercator-Océan International, Toulouse, France)