Physical control of interannual variations of the winter chlorophyll bloom in the northern Arabian Sea
| Type | Article | ||||||||
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| Date | 2017-08 | ||||||||
| Language | English | ||||||||
| Author(s) | Keerthi Madhavan Girijakumari1, Lengaigne Matthieu2, 3, Levy Marina2, Vialard Jerome2, Parvathi Vallivattathillam1, de Boyer Montegut Clement 4, Ethe Christian2, Aumont Olivier2, Suresh Iyyappan1, Akhil Valiya Parambil1, Muraleedharan Pillathu Moolayil1 |
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| Affiliation(s) | 1 : NIO, CSIR, Phys Oceanog Div, Panaji, Goa, India. 2 : Univ Paris 06, Sorbonne Univ, UPMC, CNRS,IRD,MNHN,LOCEAN Lab,IPSL, Paris, France. 3 : NIO, Indo French Cell Water Sci, IISc NIO IITM IRD Joint Int Lab, Panaji, Goa, India. 4 : Univ Brest, IFREMER, CNRS, IRD,Lab Oceanog Phys & Spatiale,IUEM, F-29280 Brest, France. |
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| Source | Biogeosciences (1726-4170) (Copernicus Gesellschaft Mbh), 2017-08 , Vol. 14 , N. 15 , P. 3615-3632 | ||||||||
| DOI | 10.5194/bg-14-3615-2017 | ||||||||
| WOS© Times Cited | 23 | ||||||||
| Abstract | The northern Arabian Sea hosts a winter chlorophyll bloom, triggered by convective overturning in response to cold and dry northeasterly monsoon winds. Previous studies of interannual variations of this bloom only relied on a couple of years of data and reached no consensus on the associated processes. The current study aims at identifying these processes using both similar to 10 years of observations (including remotely sensed chlorophyll data and physical parameters derived from Argo data) and a 20-year-long coupled biophysical ocean model simulation. Despite discrepancies in the estimated bloom amplitude, the six different remotely sensed chlorophyll products analysed in this study display a good phase agreement at seasonal and interannual timescales. The model and observations both indicate that the interannual winter bloom fluctuations are strongly tied to interannual mixed layer depth anomalies (similar to 0.6 to 0.7 correlation), which are themselves controlled by the net heat flux at the air-sea interface. Our modelling results suggest that the mixed layer depth control of the bloom amplitude ensues from the modulation of nutrient entrainment into the euphotic layer. In contrast, the model and observations both display insignificant correlations between the bloom amplitude and thermocline depth, which precludes a control of the bloom amplitude by daily dilution down to the thermocline depth, as suggested in a previous study. | ||||||||
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