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

Abstract

Abstract 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°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.