Observed interannual variability of upwelling systems in the western Arabian Sea during boreal summer
Student name: Ms Sadhvi Kwatra
Guide: Dr Neeti
Year of completion: 2017
Host Organisation: CSIR – National Institute of Oceanography, Goa
Supervisor (Host Organisation): Mr I. Suresh
Abstract: The Somalia and Oman coasts experience intense upwelling during the boreal
summer. These upwelling systems are known to have important societal
implications as they modulate the Indian monsoon rainfall by influencing the sea
surface temperature(SST) and fisheries through their influence on biological
production. Previous studies focused mainly on describing and understanding
the seasonal variability of the Chlorophyll (Chl). The aim of this thesis is to
study the observed interannual Chl variability of the western AS during summer
and to understand its physical control. This study exploits five Chl data products,
including the recently released Chl product from the European Space Agency
(ESA). Consistent with the previous studies, the summer Chl variability shows
strong relationship with that of the SST and Sea level(SL), indicating a strong
control of the wind-driven upwelling on the biological productivity through the
supply of nutrient-rich, cold subsurface waters to the euphotic zone. All the data
products indicate that regions with large interannual summer Chl variations
coincide with those having climatologically high Chl during summer. The Chl
datasets display large differences due to paucity of observations during summer.
However, the merged ESA product(OC-CCI) displays a better performance
compared to the other datasets. The results suggest that the interannual summer
Chl variability is strongly related to that of the SST and SL in both the upwelling
regions, indicating a strong control of the physics on biological productivity at
interannual timescale, as demonstrated by the previous studies at seasonal
timescale.
Keywords: Arabian Sea, upwelling, primary productivity, sea level, sea surface
temperature, interannual variability
