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Physical processes regulating the seasonal and interannual variability in chlorophyll across the equatorial and North Indian Oceans
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  • Yi Xu,
  • Ying Wu,
  • Huiwu Wang,
  • Jing Zhang
Yi Xu
State Key Laboratory of Estuarine and Coastal Research, East China Normal University

Corresponding Author:xuyi@sklec.ecnu.edu.cn

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Ying Wu
State Key Laboratory of Estuarine and Coastal Research, East China Normal University, China
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Huiwu Wang
First Institute of Oceanography
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Jing Zhang
East China Normal University
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Abstract

Based on 16-year MODIS-Aqua (MODISA) satellite products, a new method is used to derive vertical Chl distributions in the equatorial and North Indian Oceans. The Chl seasonal and interannual variabilities are examined. The Bay of Bengal (BoB) experiences summer surface Chl (SChl) increases in the areas south and east of Sri Lanka, and SChl increases in the southwestern bay during the winter monsoon. The SChl high in the Sri Lanka Dome (SLD) exists as an annual feature along the time series. SeasonalSChl variance is characterized by a distinct vertical evolution of the mixed layer depth (MLD), with the SChl increase appearing with a shallow MLD in the SLD, while SChl increase with MLD deepens in the southwestern bay in winter. The less productive southern equatorial region explains most of the interannual anomalies with diploe structures present in both the physical fields and Chl. We observed a close correlation between the Indian Ocean dipole (IOD) and the physical field anomalies, such that the wind stress curl is positively correlated with IOD in the easternequatorial India Oceanand negatively correlated in the south, with the opposite pattern observed in sea surface height (SSH) with IOD. Both surface and subsurface Chl anomalies are closely related to IOD, suggesting the bottom-up transition of thermocline feedback to biology under the remote and local influence of IOD. The advent of depth-resolved satellite Chl improves the understanding of the Chl response to changes in the environment under potential climatic feedbacks in the North Indian Ocean.