Skip to main content
padlock icon - secure page this page is secure

Free Content Observations of the East Madagascar Current system: Dynamics and volume transports

Download Article:
 Download
(PDF 12,706.8 kb)
 
The South Equatorial Current (SEC) in the Indian Ocean bifurcates when it reaches Madagascar leading, respectively, to the North East Madagascar Current (NEMC), which contours the island flowing northwestward, and to the South East Madagascar Current (SEMC), which flows southwestward. Both branches eventually contribute to the greater Agulhas Current system and thus play a part in the global ocean circulation. In addition, these currents have important effects on the local conditions for marine life. In this study, the NEMC and the SEMC are investigated based on a comprehensive, multidisciplinary survey of the east coast of Madagascar in 2008. Results from conductivity-temperaturedepth stations, underway measurements with thermosalinograph and fluorometer, and ship-mounted acoustic Doppler current profiler are discussed along with concomitant remotely sensed data. Maximum core velocities of >150 cm s–1 were observed in both the NEMC and the SEMC. The SEMC appeared as a nearshore southward jet, which extended at its widest nearly 200 km offshore. Near the southern tip of Madagascar, the SEMC was flanked by reverse velocities: a northeastward current about 30 km wide along the coast and a northeastward offshore current greater than 140 km wide suggesting the presence of the South Indian Ocean Countercurrent. The NEMC had the structure of a narrow nearshore jet, with weak currents beyond 100 km offshore. Volume transport for the upper 1,100 m was estimated to be 22 Sverdrup (Sv) for the SEMC and 48 Sv for the NEMC. The high NEMC transport compared with earlier estimates might be because of anomalously high influx of the SEC during the measurement period. Off the south coast, an undercurrent below 900 m carried an equatorward transport of 3.1 Sv. No undercurrent was observed in the north, but a geostrophic velocity minimum and a similar vertical velocity shear between surface and subsurface currents were found at the level where such a countercurrent has been previously observed from direct measurements.

35 References.

1 item.

No Article Media
No Metrics

Keywords: EAST MADAGASCAR; IN SITU OBSERVATIONS; INDIAN OCEAN; REMOTE SENSING; VOLUME TRANSPORT; WESTERN BOUNDARY CURRENT

Document Type: Research Article

Publication date: July 1, 2017

More about this publication?
  • We regret to announce that the Journal of Marine Research—one of the oldest peer-reviewed journals in American marine science—will cease publication with Volume 79 as of December 31, 2021. Therefore, the Journal of Marine Research is no longer accepting manuscript submissions, new subscriptions, or subscription renewals for 2022. All current paid subscriptions will be honored and accessible through March 2022. Back issues of all volumes since inception are available here and from the publisher's website.

    The Journal of Marine Research has published papers on physical, biological, and chemical oceanography vital to the academic oceanographic community for almost 80 years in the long and rich tradition of the Sears Foundation for Marine Research at Yale University. We thank our readers, authors, and reviewers for their interest and support.

  • Editorial Board
  • Information for Authors
  • Subscribe to this Title
  • Purchase The Sea
  • Ingenta Connect is not responsible for the content or availability of external websites
  • Access Key
  • Free content
  • Partial Free content
  • New content
  • Open access content
  • Partial Open access content
  • Subscribed content
  • Partial Subscribed content
  • Free trial content
Cookie Policy
X
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more