Sack Lunch Seminar (SLS)

The effect of stratification on wind-driven, cross-shelf circulation
on the inner shelf

Abstract:
Transport across continental shelves allows the exchange of heat,
nutrients, larvae, sediment, and pollutants between coastal ecosystems
and the open ocean. Along-shelf winds typically drive cross-shelf
transport on the midshelf, but are ineffective on the inner shelf,
where surface and bottom boundary layers overlap. Recently, the
cross-shelf wind stress had been shown to be a significant mechanism
for cross-shelf transport on the inner shelf, but the response to
stratified conditions is not well understood.

We use observations from the inner shelf south of Martha's Vineyard,
MA to describe the effect of stratification on wind-driven,
cross-shelf circulation and transport. Stratification increases the
transport driven by cross-shelf wind stresses, and this effect is
larger in the response to offshore winds than onshore winds. However,
a 1D view of the dynamics is not sufficient to explain the
relationship between circulation and stratification.

An idealized, cross-shelf transect in a numerical model (ROMS) allows
us to isolate the effects of various environmental factors on the
inner shelf response to the cross-shelf component of the wind stress.
Informed by the modeling results, we interpret the observed difference
in the circulation driven by onshore and offshore wind stresses to be
a result of the cross-shelf wind stress acting on a density field set
by both wind components, which, in the field, are not evenly
distributed around the compass.