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| Titel |
Indian Ocean Dipole and El Niño/Southern Oscillation impacts on regional chlorophyll anomalies in the Indian Ocean |
| VerfasserIn |
J. C. Currie, M. Lengaigne, J. Vialard, D. M. Kaplan, O. Aumont, S. W. A. Naqvi, O. Maury |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 10 ; Nr. 10, no. 10 (2013-10-24), S.6677-6698 |
| Datensatznummer |
250085375
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| Publikation (Nr.) |
 copernicus.org/bg-10-6677-2013.pdf |
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| Zusammenfassung |
| The Indian Ocean Dipole (IOD) and the El Niño/Southern Oscillation (ENSO)
are independent climate modes, which frequently co-occur, driving significant
interannual changes within the Indian Ocean. We use a four-decade hindcast
from a coupled biophysical ocean general circulation model, to disentangle
patterns of chlorophyll anomalies driven by these two climate modes.
Comparisons with remotely sensed records show that the simulation competently
reproduces the chlorophyll seasonal cycle, as well as open-ocean anomalies
during the 1997/1998 ENSO and IOD event. Results suggest that anomalous
surface and euphotic-layer chlorophyll blooms in the eastern equatorial
Indian Ocean in fall, and southern Bay of Bengal in winter, are primarily
related to IOD forcing. A negative influence of IOD on chlorophyll
concentrations is shown in a region around the southern tip of India in fall.
IOD also depresses depth-integrated chlorophyll in the 5–10° S
thermocline ridge region, yet the signal is negligible in surface
chlorophyll. The only investigated region where ENSO has a greater influence
on chlorophyll than does IOD, is in the Somalia upwelling region, where it
causes a decrease in fall and winter chlorophyll by reducing local upwelling
winds. Yet unlike most other regions examined, the combined explanatory power
of IOD and ENSO in predicting depth-integrated chlorophyll anomalies is
relatively low in this region, suggestive that other drivers are important
there. We show that the chlorophyll impact of climate indices is frequently
asymmetric, with a general tendency for larger positive than negative
chlorophyll anomalies. Our results suggest that ENSO and IOD cause
significant and predictable regional re-organisation of chlorophyll via their
influence on near-surface oceanography. Resolving the details of these
effects should improve our understanding, and eventually gain predictability,
of interannual changes in Indian Ocean productivity, fisheries, ecosystems
and carbon budgets. |
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