Lagrangian characterization of continental shelf circulation provides estimates of the retention and transport of particulate and dissolved substances. In this paper, we quantify the retentive characteristics of the Southeast U.S. Continental Shelf by comparing observed and numerical (modeled) drifters released throughout 2000 and 2001. Agreement between the observed and computed drifter trajectories shows that retention on this shelf can be up to two months at any point during the year. These results have important implications for ecological and fisheries applications and indicate that the populations of marine organisms in this region might be relatively closed (i.e., with weak exchange) during some periods of the year
