Radium isotopes as tracers of coastal circulation pathways in the Mid-Atlantic Bight


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dc.contributor.author Rasmussen, Linda L.
dc.coverage.spatial Mid-Atlantic Bight
dc.date.accessioned 2008-10-01T14:26:17Z
dc.date.available 2008-10-01T14:26:17Z
dc.date.issued 2003-06
dc.identifier.uri http://hdl.handle.net/1912/2444
dc.description Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2003 en
dc.description.abstract Pathways of exchange between the shelf and slope in the Mid-Atlantic Bight were investigated using a combination of radiochemical tracer and hydrographic measurements. The motivation was to provide evidence of transport routes for shelfwater that could be important to the balance of shelf-slope exchange, as well as to the biogeochemical fluxes across this crucial ocean boundary. The four radium isotopes, with half-lives of 4 days to 1600 years, a coastal source, and conservative properties in seawater, were used as coastal water mass tracers. The final study was comprised of data from 5 cruises, with a total of 8 cross-shelfbreak transects. Two areas were studied, a northern Mid-Atlantic Bight transect south of Nantucket Shoals, and a southern Mid-Atlantic Bight series of transects off the coast of Delaware. In addition, data were collected from the shelfbreak at Cape Hatteras crossing the western wall of the Gulf Stream to help determine sources of anomalous 224Ra enrichment which was observed on several of the shelfbreak transects. Combined with the hydrographic data, radium measurements suggested a pathway for exchange in the Mid- Atlantic Bight that was not a direct advection of shelf water toward the slope. Rather, the evidence suggested limited direct exchange of surface shelf water across the shelfbreak front. This provides observational evidence that is consistent with models (e.g., Gawarkiewicz and Chapman, 1991) which predict the shelfbreak front will impede exchange. Furthermore, 224Ra activity on the upper slope points to a rapid transport pathway for bottom water from the Cape Hatteras shelf via the Gulf Stream onto the Mid-Atlantic Bight slope. The radiochemical and hydrographic evidence suggests that recirculation around the slope sea gyre may be a more important pathway than direct cross-shelf transport. en
dc.description.sponsorship This work was supported by funding from the Woods Hole Oceanographic Institution Academic Programs office, the Woods Hole Oceanographic Institution Ocean Ventues Fund, National Science Foundation grant OCE-0097232, and Civilian Research and Development Foundation grant UGI-2432-SE-02. en
dc.format.mimetype application/pdf
dc.language.iso en_US en
dc.publisher Massachusetts Institute of Technology and Woods Hole Oceanographic Institution en
dc.relation.ispartofseries WHOI Theses en
dc.subject Mid-Atlantic Bight en_US
dc.subject Ocean circulation en_US
dc.subject Radium en_US
dc.subject Isotopes en_US
dc.subject Radioactive tracers in oceanography en_US
dc.title Radium isotopes as tracers of coastal circulation pathways in the Mid-Atlantic Bight en
dc.type Thesis en
dc.identifier.doi 10.1575/1912/2444

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