Indian Ocean Dipole and El Niño/Southern Oscillation impacts on regional chlorophyll anomalies in the Indian Ocean

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dc.contributor.authorCurrie, J C
dc.contributor.authorLengaigne, M
dc.contributor.authorVialard, J
dc.contributor.authorKaplan, D M
dc.contributor.authorAumont, O
dc.contributor.authorNaqvi, S W A
dc.contributor.authorMaury, O
dc.date.accessioned2021-10-08T06:20:15Z
dc.date.available2021-10-08T06:20:15Z
dc.date.issued2013
dc.description.abstractThe 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
dc.identifier.apacitationCurrie, J. C., Lengaigne, M., Vialard, J., Kaplan, D. M., Aumont, O., Naqvi, S. W. A., & Maury, O. (2013). Indian Ocean Dipole and El Niño/Southern Oscillation impacts on regional chlorophyll anomalies in the Indian Ocean. <i>Biogeosciences</i>, 10(3), 5841 - 5888. http://hdl.handle.net/11427/34232en_ZA
dc.identifier.chicagocitationCurrie, J C, M Lengaigne, J Vialard, D M Kaplan, O Aumont, S W A Naqvi, and O Maury "Indian Ocean Dipole and El Niño/Southern Oscillation impacts on regional chlorophyll anomalies in the Indian Ocean." <i>Biogeosciences</i> 10, 3. (2013): 5841 - 5888. http://hdl.handle.net/11427/34232en_ZA
dc.identifier.citationCurrie, J.C., Lengaigne, M., Vialard, J., Kaplan, D.M., Aumont, O., Naqvi, S.W.A. & Maury, O. 2013. Indian Ocean Dipole and El Niño/Southern Oscillation impacts on regional chlorophyll anomalies in the Indian Ocean. <i>Biogeosciences.</i> 10(3):5841 - 5888. http://hdl.handle.net/11427/34232en_ZA
dc.identifier.issn1726-4170
dc.identifier.issn1726-4189
dc.identifier.ris TY - Journal Article AU - Currie, J C AU - Lengaigne, M AU - Vialard, J AU - Kaplan, D M AU - Aumont, O AU - Naqvi, S W A AU - Maury, O AB - 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 DA - 2013 DB - OpenUCT DP - University of Cape Town IS - 3 J1 - Biogeosciences LK - https://open.uct.ac.za PY - 2013 SM - 1726-4170 SM - 1726-4189 T1 - Indian Ocean Dipole and El Niño/Southern Oscillation impacts on regional chlorophyll anomalies in the Indian Ocean TI - Indian Ocean Dipole and El Niño/Southern Oscillation impacts on regional chlorophyll anomalies in the Indian Ocean UR - http://hdl.handle.net/11427/34232 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/34232
dc.identifier.vancouvercitationCurrie JC, Lengaigne M, Vialard J, Kaplan DM, Aumont O, Naqvi SWA, et al. Indian Ocean Dipole and El Niño/Southern Oscillation impacts on regional chlorophyll anomalies in the Indian Ocean. Biogeosciences. 2013;10(3):5841 - 5888. http://hdl.handle.net/11427/34232.en_ZA
dc.language.isoeng
dc.publisher.departmentDepartment of Biological Sciences
dc.publisher.facultyFaculty of Science
dc.sourceBiogeosciences
dc.source.journalissue3
dc.source.journalvolume10
dc.source.pagination5841 - 5888
dc.source.urihttps://dx.doi.org/10.5194/bg-10-6677-2013
dc.subject.otherIndian Ocean Dipole
dc.subject.otherEl Niño
dc.subject.otherRemote sensing
dc.subject.otherSouthern Oscillation
dc.subject.otherproductivity
dc.subject.otherchlorophyll
dc.subject.otherJournal Article
dc.titleIndian Ocean Dipole and El Niño/Southern Oscillation impacts on regional chlorophyll anomalies in the Indian Ocean
dc.typeJournal Article
uct.type.publicationResearch
uct.type.resourceJournal Article
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