Ocean climate variability off Newfoundland and Labrador over 1979-2010: A modelling approach

A coupled ice-ocean model with a horizontal resolution of 7 km is developed for the Newfoundland and Labrador Shelves to examine climate trend and variability of ocean and ice conditions over 1979-2010. Daily surface atmospheric forcing is applied and monthly open boundary conditions are prescribed. The model has reasonable skill in simulating interannual and decadal variability and long-term (1979-2010) trend for temperature, salinity, transport and ice over the Newfoundland and Labrador Shelves. At a long-term monitoring station both the model and observation show substantial interannual variability in the surface temperature and salinity, a warming trend in the surface temperature, and no trend in the surface salinity. The model sea ice extent south of 55 degrees N shows significant interannual and decadal variability and a declining trend consistent with observations. Both model and altimetric observation show a declining trend in the transport of the shelf-edge Labrador Current from 1993 to 2010. The total Labrador Current volume transport is correlated with the North Atlantic Oscillation with time lags of 0-3 years, with the inshore branch having a positive trend while the shelf-edge branch having no trend. The inshore Labrador Current shows an increase of the freshwater transport associated with an increase of the volume transport due to large-scale baroclinic forcing, with the interannual and decadal variability of the freshwater transport dominated by the volume transport; while the shelf-edge transport shows a decrease of the freshwater transport associated with an increase of salinity, with the interannual and decadal variability of the freshwater transport dominated by salinity.