1999 SI Meeting Poster

Lagrangian residence times over Georges Bank during 1995-1999

R. Limeburner, R. C. Beardsley, and K. Brink

Satellite-tracked drifters with holey sock drogues centered at 10-m depth were deployed over Georges Bank between January and June during 1995-99 in support of the U.S. GLOBEC/Georges Bank Program. In general, drifter behavior over Georges Bank was characterized by three regimes: winter non-dispersive circulation interrupted by strong wind-driven events, summer recirculation near the 60-m isobath, and the collapse of the recirculation field in late fall.

The duration of time each drifter remained over Georges Bank (i.e., its residence time) is of special interest to understanding the distribution, transport, and survival of larval cod and haddock on the Bank. We provide here estimates of the residence time of the GLOBEC drifters within a region enclosed by the 100-m isobath around the Bank and 69° 24’ W, which bisects the Great South Channel to the west of the Bank. The mean residence time of this region was 63 days with a standard deviation of 48 days. The maximum individual residence time was 200 days. In general, monthly mean residence time increased from winter (January/February) to summer (August/September). Monthly mean residence times during January-April,1995 were much greater than during 1996-99. The mean residence time of drifters passing through the eastern flank of the Bank, defined by the U.S./Canada border and the 100-m isobath, was 32 days. Shown below is the 1999 residence time for the Bank. Mean residence time (days) for each deployment set are shown as red dots. Red pluses show the mean monthly residence time when no drifters were deployed. Thick blue lines are recirculating drifters.