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Evolution to decay of upwelling and associated biogeochemistry over the southeastern Arabian sea shelf

DRS at CSIR-National Institute of Oceanography

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Title Evolution to decay of upwelling and associated biogeochemistry over the southeastern Arabian sea shelf
 
Creator Gupta, G.V.M.
Sudheesh, V.
Sudharma, K.V.
Saravanane, N.
Dhanya, V.
Dhanya, K.R.
Lakshmi, G.
Sudhakar, M.
Naqvi, S.W.A.
 
Subject Chemistry and biogeochemistry
Chemistry and biogeochemistry
Chemistry and biogeochemistry
Chemistry and biogeochemistry
 
Description Observations along 10 shelf transects in 2012 near 10°N in the southeastern Arabian Sea revealed the usual warm oligotrophic conditions during the winter monsoon and upwelling of oxygen-deficient, nutrient-rich cool water during the summer monsoon (SM). By changing an oligotrophic to a nutrient-replete condition, the upwelling is the major process that regulates the biogeochemistry of this shelf. Its onset is perceptible at 100m depth between January and March. The upwelling reaches the surface layer in May and intensifies during June–July but withdraws completely and abruptly by October. Despite the nutrient injection, the primary production during SM, integrated for euphotic zone, is comparable to that during the preceding spring intermonsoon (SIM). Again, as usual, the high oxygen demand coupled with low concentration in the upwelled subsurface waters causes severe oxygen depletion below the shallow pycnocline. The oxygen concentrations/saturations of 2012 on the midshelf are similar from those of mid-1958 to early 1960, except for marginally higher values during the peak upwelling period due to relatively weak upwelling in 2012. This implies little anthropogenic influence on coastal hypoxia unlike many other coastal regions. In 2012, the inner shelf system shifted from net autotrophy in SIM to net heterotrophy in SM but on an annual basis it was net autotrophic (gross primary production to community respiration ratio, GPP/R:1.11±0.84) as organic production exceeded consumption
 
Date 2017-02-14T11:48:59Z
2017-02-14T11:48:59Z
2016
 
Type Journal Article
 
Identifier Journal of Geophysical Research (G: Biogeosciences), vol.121(1); 2016; 159-175
http://drs.nio.org/drs/handle/2264/5064
 
Language en
 
Rights © 2015. The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
 
Publisher AGU Publications