Biweekly current oscillations on the continental slope of the Gulf of Guinea

Type Article
Date 2005-11
Language English
Author(s) Vangriesheim Annick1, Treguier Anne-Marie2, 4, Andre Gael3
Affiliation(s) 1 : IFREMER, Lab Environm Profond, Brest, France.
2 : IFREMER, CNRS, Lab Phys Oceans, Brest, France.
3 : IFREMER, Lab Phys Hydrodynam & Sedimentaire, Brest, France.
Source Deep Sea Research Part I: Oceanographic Research Papers (0967-0637) (Elsevier), 2005-11 , Vol. 52 , N. 11 , P. 2168-2183
DOI 10.1016/j.dsr.2005.05.010
WOS© Times Cited 16
Keyword(s) Linear wave model, Current meter measurement, Current oscillation, Continental slope
Abstract Current meter measurements have been carried out for 3 years on the continental slope of the Gulf of Guinea, near 7.5 degrees S off the Angola coast. Currents in a water depth of 1300 m over the continental slope show a remarkable biweekly oscillation, bottom intensified, and with currents oriented nearly parallel to the isobaths. With a peak-to-peak amplitude reaching 20-30 cm s(-1) at 30 in above the bottom, this signal is the most energetic at sub-inertial frequencies. Simultaneous measurements deeper on the continental rise (in a water depth of 4000 m) show a more complex signal dominated by lower frequencies, and with less clear polarization. Simple linear topographic wave theories are compared to the observations. A combination of coastal trapped waves with cross-slope mode 3-5 could be consistent with the observed currents. A three-dimensional 1/6 degrees model suggests the existence of modes trapped to the slope, although with lower amplitude than observed.
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