Contrasting the influence of the Gulf Stream on shelf-deep ocean exchange events at the Middle Atlantic Bight and the South Atlantic Bight near Cape Hatteras

Near Cape Hatteras, the Gulf Stream transitions from a western boundary current jet that is attached to the upper continental slope to a free jet as it crosses isobaths and flows into the deeper water regions of the ocean interior. Due to the downstream difference in control exerted by the topography, different processes dominate the variability observed in the Gulf Stream up- and down-stream of Cape Hatteras. Onshore of the separating Gulf Stream, the Hatteras Front, which migrates back and forth along the boundary past Cape Hatteras, marks the convergence of currents on the continental shelves and upper slopes. Though there must be a net export from the shelves/slopes into the ocean interior, there is likely two-way exchange in this dynamic region. Here we consider the Gulf Stream’s influence on exchange events near Cape Hatteras using in situ observations collected along and across the Gulf Stream by five current and pressure sensing inverted echo sounders (CPIESs). These were deployed for 18 months as part of the PEACH Program (Processes driving Exchange At Cape Hatteras). We also consider observations from a tall mooring deployed downstream of the separation point for the final 9 months of the experiment period. The CPIESs and tall-mooring measurements are used to characterize the temporal and spatial variability in the Gulf Stream as it separates near Cape Hatteras. Complementary observations from remote sensing (SST, altimetry) and in situ measurements (Spray gliders, other PEACH assets) are used to provide context to help interpret the CPIESs and tall-mooring observations.