Satellite-derived sea surface temperature fronts on the continental shelf off the northeast US coast

The distribution and variability of sea surface temperature (SST) fronts, over the shelf and slope along the east coast of North America from Cape Hatteras to Nova Scotia, are studied using a 12 year time series (1985-1996) of advanced very high resolution radiometer (AVHRR) images. After the masking of cloud-contaminated pixels, an edge-detection algorithm identifies surface temperature fronts in each image. Maps of the seasonal probability of detecting a front indicate substantial spatial and temporal variability in the occurrence of SST fronts. Over the continental shelf south of New England during spring through autumn, surface fronts are rare and observed only in scattered locations. North of Nantucket Shoals, both tidal mixing fronts and fronts associated with the Eastern Maine Coastal Current occur during the summer. A major finding of this study is the observation of fronts in winter over the inner and middle shelf from Cape Hatteras to the Bay of Fundy. These fronts, peaking during January-March, are characterized by cold SST on their inshore (shallow) side and appear to result from the influence of surface cooling on shallow nearshore waters. The shelfbreak front is found to vary strongly with season, being detected most frequently during spring and autumn. South of Hudson Canyon, it essentially disappears during the summer, while from Hudson Canyon to Northeast Channel, it weakens during summer but nevertheless remains detectable in SST.