Finestructure measurement of vertical mixing in the vicinity
of fronts on Georges Bank
D. Ullman, D. Hebert, and J. Barth
The difficulty of measuring cross-frontal fluxes
in the vicinity of a moving front is compounded
by the fact that the relevant mixing processes
may be intermittent in time and patchy in space.
A sampling scheme of repeated rapid transects
across the front can be used to resolve such processes.
During June, 1999 on the southern flank of Georges
Bank, we conducted intensive SeaSoar hydrographic
surveys in the vicinity of both the tidal mixing
front and the shelfbreak front. Two types of surveys,
larger scale radiator patterns (~35 km lines traversed
in ~3 hours) and smaller scale butterfly patterns
(20 km by 10 km completed in ~6 hours), were carried
out. A quasi-Cox number computed from conductivity
sampled at 24 Hz is a qualitative indicator of vertical
mixing. We present the space-time distribution of
this parameter relative to the fronts over the
tidal cycle in order to identify the important
locations and times of small scale mixing.