Ma. Spall, DYNAMICS OF THE GULF-STREAM DEEP WESTERN BOUNDARY CURRENT CROSSOVER .1. ENTRAINMENT AND RECIRCULATION, Journal of physical oceanography, 26(10), 1996, pp. 2152-2168
A regional primitive equation model is applied to the study of the int
eraction between the Gulf Stream and the deep western boundary current
(DWBC) where they cross at Cape Hatteras. It is found that fur a wide
range of forcing parameters the upper core of the DWBC is split into
two mean paths at the crossover, one flowing toward the south dong the
western boundary and the other flowing toward the east under the Gulf
Stream. The eastward branch is entrained into the southern recirculat
ion gyre acid. after bring diverted into the interior for up to 1500 k
m, eventually returns to the western boundary current and continues to
flow southward. This recirculation and mixing is shown to have a sign
ificant impact on the separation point and mean path of the Gulf Strea
m, the basin-scale stratification, and the properties of the DWBC sout
h of the crossover. Fur most configurations, the lower DWBC remains la
rgely on the western boundary and interacts only weakly with the inter
ior. The entrainment of the upper core is shown to be driven by a baro
clinic, time-dependent process of DWBC water eddy formations into the
recirculation pq res under the Gulf Stream. Potential vorticity consid
erations are key to understanding the entrainment mechanism and its se
nsitivity to variations in the model forcing and configuration. A scal
ing estimate of the amount of entrained DWBC water as a function of th
e eddy field is derived. The mean paths of the upper and loa er DWBCs
and strength of the eddy fluxes compare well with various observationa
l estimates. The importance of such entrainment and mixing processes o
n large-scale ocean modeling and climate studies is discussed.