Sheremet, V.1, Y.K. Cho2, R. Beardsley1
1
1Department of Physical Oceanography, Woods Hole Oceanographic
Institution, Woods Hole, MA 02543
2TBD
Georges Bank is separated from the Scotian Shelf by the Northeast
Channel. This channel is over 200m deep, about 50km wide, and
connects the upper continental slope to the deep Gulf of Maine.
Scotian Shelf Water (SSW) generally flows into the Gulf of Maine,
however, episodic "crossovers" can occur (mostly in spring),
with SSW being carried directly from the Scotian Shelf across
Northeast Channel to Georges Bank. Little is known about the primary
physical mechanisms which trigger and sustain the SSW crossovers.
In a numerical study of crossover events we found that, for realistic parameters, it is possible to reproduce SSW crossovers by varying the density difference between the shelf and slope waters or the strength of the shelf-break front jet. The change of the flow pattern is very abrupt: a slight increase of slope water temperatures by only 1.5C may significantly increase the frequency of crossover events and potentially allow continuous flow of SSW onto the Georges Bank.
We also conducted a series of laboratory experiments on a rotating platform modeling the flow in the Northeast Channel using an idealized configuration. The barotropic laboratory experiments revealed that, as the flow started to leap across the channel, the onset of separation occurred at a point located farther toward the Gulf of Maine rather than near Browns Bank, which bears a striking resemblance to many satellite images. Introducing the baroclinicity causes the displacement of the separation point toward Browns Bank to be in agreement with numerical results.
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