Seasonal variability of sea surface temperature fronts on Georges Bank

Tim Mavor

Sea surface temperature (SST) fronts, extracted from archived (1985-1995) Advanced Very High Resolution Radiometer (AVHRR) data, are determined in the Georges Bank region. Resulting frontal locations clearly show the tidal mixing front near the 50-meter isobath on Georges Bank, as well as the presence of a persistent front near the shelfbreak. The probability of detecting an SST front at an individual pixel on Georges Bank is presented as a monthly climatology. Variations in the position and probability of SST fronts in the Georges Bank region show the summer development of the tidal mixing front. Using the 132 monthly probability images from this time period, spatial and temporal information from empirical orthogonal function (EOF) analysis indicate that the seasonal development of the tidal mixing front is likely contained in the most energetic (first) mode. Spatial patterns associated with the first mode also reveal the winter occurrence of fronts on the Northeast Peak area of Georges Bank, which is most likely associated with Scotian Shelf Water flow across the Northeast Channel. The second mode also indicates the development of the hot spot often observed over Georges Bank during the late summer and early fall. Comparison of detected SST fronts to historical hydrographic data on Georges Bank points to the fronts being located in increasingly stratified water from April through August. Further evidence indicates that the mean position of detected SST fronts on Georges Bank changes approximately 10 kilometers on-bank from mid-spring to late summer, with more seasonal variability on southern Georges Bank. More intense seasonal stratification on southern Georges Bank is the likely cause for this difference.