Three dimensional structure and variability of low-frequency currents on the Texas-Louisiana shelf based on moored current meter data /
Three dimensional structure and variability of low-frequency currents on the Texas-Louisiana shelf are described based on current meter measurements at 31 moorings (75 meters) from April 1992 to November 1994 as part of the Texas-Louisana Shelf Circulation and Transport Processes Study. Two objecti...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1996.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=739363391&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Three dimensional structure and variability of low-frequency currents on the Texas-Louisiana shelf are described based on current meter measurements at 31 moorings (75 meters) from April 1992 to November 1994 as part of the Texas-Louisana Shelf Circulation and Transport Processes Study. Two objective methods generate velocity streamfunctions consistent with observations. For the transport streamfunction, only one method produces a reasonable field. Comparison of velocity streamfunctions and geopotential anomaly fields reveals consistency in nearshore region during nosummer. During summer, the two maps are quite different because of the ageostrophic nearshore flow. The 32-month velocity streamfunction patterns generally support the Cochrane and Kelly scheme. The flow was downcoast in the nearshore region during nonsummer. During summer, the flow reversed and was directed upcoast over the entire shelf. The first empirical orthogonal function (EOF) of velocity streamfunction shows a simple shelf-wide pattern of alongshore flow. The amplitude of the first EOF is clearly related to the seasonal variation of wind, verifying that wind is the primary forcing for seasonal variation of low-frequency circulation on the shelf. The shelf-wide transport streamfunction has a very similar structure to the velocity streamfunction, with transport directed downcoast during nonsummer and upcoast during summer. Transport amounts to about 0.1 to 0.3 Sv (1 Sv = 10e6 m3se-1̄) from nearshore to mid-shelf. The first three EOFs account for about 93% of the variance. The mean current and its variability along the 20-m isobath are strongly polarized in the alongshelf direction at both top and bottom of the water column. Cyclic shearing exists between top and bottom meters in both mean and first EOFs. Along the 50-m isobath, the mean current and its fluctuation have a large cross-shelf component, especially in the central portion of the shelf. The mean current along the 200-m isobath has a small cross-shelf component. The alongshelf alignment of current fluctuation are moderate along the 200-m isobath. |
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| Item Description: | Vita. "Major Subject: Oceanography". |
| Physical Description: | xv,121 leaves : illustrations, maps ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 103-106. |