Physical processes regulating the seasonal and interannual variability
in chlorophyll across the equatorial and North Indian Oceans
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.