HR: 0800h
AN: OS41B-0604    [Abstracts]
TI: Gap Leaping Western Boundary Current in a Circular Tank Model
AU: * Sheremet, V A
EM: vsheremet@gso.uri.edu
AF: Graduate School of Oceanography/ University of Rhode Island, 215 South Ferry Rd, Narragansett, RI 02882 United States
AU: Kuehl, J
EM: jkuehl@gso.uri.edu
AF: Graduate School of Oceanography/ University of Rhode Island, 215 South Ferry Rd, Narragansett, RI 02882 United States
AB: The interaction of a boundary current with bathymetric features such as a gap in the ridge or a strait between two islands is an important and interesting oceanographic problem. Multiple flow patterns (penetrating or leaping the gap) and hysteresis (dependence on prior evolution) may exist in such systems. Examples include: the Gulf Stream leaping from Yucatan to Florida, the Kuroshio leaping from Luzon to Taiwan. Using numerical analysis, Sheremet (2001) found that the multiple steady states can be explained by variation in the balance between the inertia (which promotes leaping state) and the beta-effect (which promotes penetrating state). In the present work we offer a verification of the multiple states and hysteresis in a laboratory model. To set up a gap leaping current we use a circular tank with a sloping bottom (simulating the beta-effect) and drive flow using a new method of pumping fluid through sponges (thus generating a Sverdrup flow in the interior). A semicircular ridge with a gap is inserted into the western part of the tank. Using a dye release flow visualization method we dramatically show the existence of multiple flow patterns over varying boundary current transport values differing by the factor of nearly two. An associated numerical model in bipolar curvilinear coordinates allowing to match all the boundaries reproduces the laboratory results very well. This idealized problem offers very useful geophysical test case for numerical models involving flow separation and reattachment.
DE: 4203 Analytical modeling and laboratory experiments
DE: 4243 Marginal and semi-enclosed seas
DE: 4562 Topographic/bathymetric interactions
DE: 4576 Western boundary currents
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005