Publication Date:
2022-05-26
Description:
Author Posting. © Elsevier B.V., 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 53 (2006): 2501-2519, doi:10.1016/j.dsr2.2006.08.004.
Description:
Data from 16 clustered-drifter deployments are used to examine horizontal dispersion on the southern flank of Georges Bank. The spreading rates of all clusters have an average of 1.6 km d-1 with a standard deviation of 1.8 km d-1. Both "effective" and "apparent" diffusivities are calculated for each cluster. Their ranges (i.e., -54 to 757 m2 s-1 for effective diffusivity) are related to differences in cluster size and proximity to the tidal mixing front. Cross-bank convergence is documented for nearly 40% of the clusters. This occurs especially for clusters with centroids within 10 km of the tidal mixing front location, as deduced from conductivity, temperature, and depth transects (CTD) conducted concurrently with the cluster deployments. Estimates of turbulent dispersion (distinct from shear effects) are derived by the method of Okubo and Ebbysmeyer (Okubo, A. and Ebbesmeyer, C.C., 1976. Determination of vorticity, divergence, and deformation rates from analysis of drogue observations. Deep-Sea Res., 23, 349-352). The results reveal that the effects of horizontal shear are important in spreading of larger drifter clusters. Often the impact of shear is evidenced by the track of a lone drifter that separates from a cluster as it is entrained into the current of the shelf-edge front or the tidal mixing front. Cluster dispersion is time dependent as evidenced by a significant modulation of cluster size at the M2 tidal frequency. This modulation is due to the spatial variation of tidal currents over the southern flank of Georges Bank and is closely reproduced by immersing drifter clusters into the flow field of a Georges Bank tidal model.
Description:
The work carried out at WHOI was supported by the U.S. National Science Foundation under grants OCE-98-06498, OCE-96-32357, OCE98-06397 and OCE02-27679. The effort at the Woods Hole NMFS was funded through a grant from the NOAA Coastal Ocean Program.
Keywords:
Dispersion
;
Drifters
;
Tidal front
;
Georges Bank
;
Gulf of Maine
;
Fish larvae
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
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