Influence of Coupled Rossby Waves on Primary Productivity and Tuna Abundance in the Indian Ocean |
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Authors: | Warren B White Kathryn A Gloersen Francis Marsac Yves M Tourre |
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Institution: | (1) Scripps Institution of Oceanography, UCSD, La Jolla, CA, 92037, U.S.A.;(2) University of California San Diego, La Jolla, CA, 92037, U.S.A;(3) UR, 109 Thetis, IRD, La Reunion, France;(4) LDEO of Columbia University, Palisades, NY, 10964, U.S.A |
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Abstract: | Interannual coupled Rossby waves in the extratropical Indian Ocean propagate westward in covarying pycnocline depth, sea surface
temperature, and meridional surface wind anomalies from the west coast of Australia between 15°S and 35°S, taking 3–4 years
to transit the interior ocean to Madagascar. In the interior subtropical gyre, where the tuna longline catch (TLC) mainly
concerns two species (albacore and bigeye), these waves have been observed to affect year-to-year changes in catch, with wave
crests (troughs) in the main pycnocline associated with high (low) TLC anomalies. This suggested that tuna longline catch
is associated with the entrainment of nutrient-rich pycnocline water into the photic zone and a subsequent increase in primary
productivity there. Here, this hypothesis is examined within the context of SeaWiFS chlorophyll concentration (CC). We find
the situation the opposite of that expected, with wave crests (troughs) in the main pycnocline associated with low (high)
CC anomalies averaged over the photic zone. These results are shown to be consistent with a model relating the anomalous CC
tendency to upper-layer divergence in the wave, not unlike that relating surface slicks to upper-layer divergence in internal
gravity waves. Thus, the connection between interannual coupled Rossby waves and TLC in the interior subtropical gyre does
not appear to derive from wave-induced modulation of the pelagic food web.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | Coupled Rossby waves primary productivity tuna abundance Indian Ocean interannual variability |
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