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Abstract The surface-intensified, poleward-flowing Gulf Stream (GS) encounters the equatorward-flowing Deep Western Boundary Current (DWBC) at 36° N off Cape Hatteras. In this study, daily output from a data-assimilative, high-resolution (800 m), regional ocean reanalysis was examined to quantify variability in the velocity structure of the GS and DWBC during 2017–2018. The validity of this reanalysis was confirmed with independent observations of ocean velocity and density that demonstrate a high level of realism in the model’s representation of the regional circulation. The model’s daily velocity time series across a transect off Cape Hatteras was examined using rotated Empirical Orthogonal Function analysis, and analysis suggests three leading modes that characterize the variability of the western boundary currents throughout the water column. The first mode, related to meandering of the GS current, accounts for 55.3% of the variance, followed by a “wind-forced mode”, which accounts for 12.5% of the variance. The third mode, influenced by the DWBC and upper-ocean eddies, accounts for 7.1% of the variance. 

Abstract Shelf water is influenced by atmospheric forcing, river outflows, and the open ocean. Studying its variability is crucial for understanding anthropogenic impacts on coastal oceans and their transport to the open ocean. In the Middle Atlantic Bight (MAB), the interaction of the Gulf Stream with shelf/slope circulation leads to some of the complex exchanges between the shelf and open ocean along the U.S. East Coast. This study employs a Lagrangian particle tracking approach, grounded in a high‐resolution, data‐assimilative ocean reanalysis, to examine the export pathways of surface shelf water in the MAB. We analyzed over 700 daily images of simulated particle distributions using image clustering techniques. This revealed three distinct export patterns: abrupt entrainment to the Gulf Stream, gradual entrainment, and southern transport. Each pattern was observed roughly equally during the study period from January 2017 to December 2018. The observed export patterns are closely linked to the coastal circulation dynamics near Cape Hatteras. Understanding the timing and duration of these patterns is vital for assessing water quality and predicting the settlement of species that spawn in the region. Our study further underscores the influence of tropical cyclones, including Hurricanes Jose, Maria, and Chris, on these export patterns. These extreme weather events lead to significant shifts in coastal circulation near Cape Hatteras.