Variability of Current Streams in Atlantic Canadian Waters: A Model Study

Monthly output from a high-resolution numerical ocean model simulation of the North Atlantic Ocean for the 1990–2011 period is analyzed to investigate the properties and relationships between the various current streams in Atlantic Canadian shelf waters at seasonal and annual time scales. Particular focus is placed on the sections of the Atlantic Zone Monitoring Program, which are subdivided into nearshore and shelf-break components. At seasonal time scales, model results indicate that all nearshore series exhibit seasonal cycles with minima during mid-year, but shelf-break series do not. The seasonal cycles are consistent with the barotropic component of the Arctic melt cycle. At annual time scales, shelf-break series show generally decreasing correlations with increasing downstream distance. Correlation coefficients of approximately 0.5 exist for sections on the Newfoundland and Scotian shelves separated by over 2000 km. Remarkably, no correlation is found for the inshore Labrador Current and the flow through the Strait of Belle Isle or other downstream sections. The transport through these sections is found to correlate with across- and along-shelf sea level gradients. On the Scotian Shelf, nearshore series exhibit decreasing sequential correlation. Behaviour of flows into the Gulf of Maine is consistent with a conservation of volume relation whereby an increase in the Nova Scotia Current is compensated for by less inflow and more outflow through the Northeast Channel (and vice versa).