Bisagni, J.J.
School for Marine Science & Technology and Physics Department,
University of Massachusetts Dartmouth
The shelf-slope front (SSF) is an oceanographic front separating
colder and less-saline continental shelf waters located off the
northeastern United States and Canada from warmer and more-saline
slope waters located over the continental slope. The SSF is visible
year-round using sea surface temperature (SST) data obtained by
NOAA's polar-orbiting satellites. Availability of 20 years
(1973-1992) of SSF positions, digitized from weekly SST charts
between 75 degrees - 50 degrees West, allows an analysis of seasonal variability
of the SSF position. Time series of mean monthly SSF positions were
produced along each longitude over the 20-year period. Using a
published long-term (1973-1992) mean SSF position climatology,
monthly SSF position anomalies are computed at each longitude by
subtracting the climatology from long-term mean monthly SSF frontal
positions. Results show seasonal variability of the SSF position
agreeing with earlier work showing a maximum seaward (shoreward)
anomaly during winter (summer), with largest variability (+/-50 km)
east of 58°W. However, an apparent westward propagation of the
seaward-most SSF position is evident from 50 to 58 degrees West from
November to April, with eastern-most and western-most SSF anomalies
being 180° out of phase. An Empirical Orthogonal Function analysis
of observed seasonal SSF anomalies is presented along with an
analysis of estimated seasonal SSF anomalies produced using gridded
wind-stress and simplified Ekman dynamics.
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