Equatorial currents and transports in the upper central Indian Ocean: Annual cycle and interannual variability.

Reppin, Jörg, Schott, Friedrich, Fischer, Jürgen and Quadfasel, D. (1999) Equatorial currents and transports in the upper central Indian Ocean: Annual cycle and interannual variability. Open Access Journal of Geophysical Research: Oceans, 104 (C7). 15,495-15,514. DOI 10.1029/1999JC900093.

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Abstract

The zonal circulation south of Sri Lanka is an important link for the exchange of water between the Bay of Bengal and the Arabian Sea. Results from a first array of three moorings along 80 degrees 30'E north of 4 degrees 10'N from January .1991 to March 1992 were used to investigate the Monsoon Current regime [Schott et al., 1994]. Measurements from a second array of six current meter moorings are presented here. This array was deployed along 80 degrees 30'E between 45'S and 5 degrees N from July 1993 to September 1994 to investigate the annual cycle and interannual variability of the equatorial currents at this longitude. Both sets of moorings contribute to the Indian Ocean current meter array ICM8 of the World Ocean Circulation Experiment. The semiannual equatorial jet (EJ) was showing a large seasonal asymmetry, reaching a monthly mean eastward transport of 35 Sv (1 Sv = 1 x 10(6) m(3) s(-1)) in November 1993, but just 5 Sv in May 1994. The Equatorial Undercurrent (EUC) had a maximum transport of 17 Sv in March to April 1994. Unexpectedly, compared to previous observations and model studies, the EUC was reappearing again in August 1994 at more than 10 Sv transport and was still flowing when the moorings were recovered. In addition, monthly mean ship drifts near the equator are evaluated to support the interpretation of the moored observations. Interannual variability of the EJ in our measurements and ship drift data appears to be related to the variability of the zonal winds and Southern Oscillation Index. The output of a global numerical model (Parallel Ocean Climate Model) driven by the winds for 1993/1994 is used to connect our observations to the larger scale. The model reproduces the EJ asymmetry and shows the existence of the EUC and its reappearance during summer 1994.

Document Type: Article
Keywords: Physical Oceanography; SEA-SURFACE TEMPERATURE; SOMALI CURRENT; SOUTHWEST MONSOON; SUMMER MONSOON; AUGUST 1993; MODEL; CIRCULATION; NORTHERN; 26-DAY; GYRE
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1029/1999JC900093
ISSN: 2169-9275
Projects: WOCE
Date Deposited: 03 Mar 2008 11:15
Last Modified: 17 Apr 2018 08:25
URI: http://oceanrep.geomar.de/id/eprint/4276

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