Date of Award

Spring 1995

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ocean & Earth Sciences

Committee Director

A. D. Kirwan, Jr.

Committee Member

John Adam

Committee Member

Stanford B. Hooker

Committee Member

John Klinck

Abstract

Beginning with the observations made by the Warm-Core Rings program in the early 1980's, several Gulf Stream warm-core rings (WCR's) in the Middle Atlantic Bight (MAB) have been observed with one or more cyclones around their periphery. These ring systems are observed in the slope water between the Gulf Stream's western boundary and the shelf break. Observations of ring systems have motivated a reanalysis of existing satellite surface temperature imagery, which revealed that multipole structure is common for both warm and cold core rings. This suggests that rings are better characterized as one part of multipole systems rather than as isolated vortices.

Dynamical studies of ring systems have been primarily limited to numerical modeling of isolated nonlinear vortices and interactions of vortices with sloping topography. Here, a baroclinic rotating modon model is used to simulate the dynamics of a WCR paired with a peripheral cyclone, over a flat bottom. Observations of WCR 82B and a peripheral cyclone are used to constrain the model parameters.

A diagnostic calculation compares model ring and cyclone velocity profiles with observations and provides estimates of ring and dipole energies, as well as an estimate of volume transport across a 150 km section representing the NAB shelf-slope front. In addition, four different methods for estimating the location of the ring and cyclone perimeters are compared.

Results are also presented for two evolutionary calculations. The first calculation uses three groups of fluid parcels, allowed to evolve for 14 days, to simulate three flow features apparent in satellite imagery of the WCR 82B system. The second calculation simulates entrainment of shelf water and Gulf Stream water by allowing two long, thin patches of fluid parcels to evolve for 7.4 days. The final parcel distribution is again compared with satellite imagery for the WCR 82B system.

These results show that the rotating baroclinic modon model provides a useful dynamical simulation of a dipolar ring system. The model produces a velocity field that is consistent with observations, and it allows ring and dipole energies, volume transport, and ring and cyclone perimeter position to be estimated.

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DOI

10.25777/0byc-t184

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