Observations and modelling of deep equatorial currents in the central Pacific
Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1988.
Bibliographic Details
| Main Author: |
Ponte, Rui Vasques de Melo |
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| Other Authors: |
James Luyten.Time-lagged coherence calculations revealed evidence for vertical shifting of the jets on interannual time scales. Interpretation of results in terms of single frequency linear wave processes led to inconsistencies, but finite bandwidth (in frequency and wavenumber) Kelvin wave processes of periods on the order of three to five years could account for the observations. Thus, the records do not preclude equatorial waves as a reasonable kinematic description of the jets. At all wavenumber bands in general, power levels decayed away from the equator over scales broader than the Kelvin wave scale, suggesting the presence of Rossby wave energy. Cross-spectral analysis showed Rossby and Kelvin wave motions to be dominant at the equator over the 933 sm and the 140-400 sm vertical wavelength bands, respectively. The latter agrees with the findings of Eriksen (1981) in the western Pacific, and thus seems to be a climatological feature of the deep equatorial Pacific fields. In an attempt to model the observed zonal velocity signals, alternative forcing mechanisms for the deep ocean (other than direct surface winds) were tried. The probable presence of deep energy sources at the ocean side walls (e.g., Kawase, 1987) was explored by considering the linear response of an equatorial ocean to a time varying zonal jet placed at the lateral boundaries. In another simple model, we examined the character of stationary Kelvin wave solutions obtained in the presence of vertically sheared mean westward flows. In this case, the waves are forced below the thermocline by a vertical velocity representing large scale convergence or divergence patterns associated with the upper ocean circulation. Results suggest that both ideas remain potentially important to the existence of deep baroclinic currents in the equatorial ocean. |
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| Format: | Thesis
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| Language: | eng |
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| Published: |
Massachusetts Institute of Technology
2010
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| Online Access: | http://hdl.handle.net/1721.1/58499
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