Methane in coastal and offshore waters of the Arabian Sea

Show simple item record Jayakumar, D.A. Naqvi, S.W.A. Narvekar, P.V. George, M.D. 2009-01-07T10:21:25Z 2009-01-07T10:21:25Z 2001
dc.identifier.citation Marine Chemistry, Vol.74; 1-13p.
dc.description.abstract Measurements of methane (CH sub(4)) made during two surveys in the eastern and central Arabian Sea in April-May, 1996, and August-September, 1997, corresponding to late Spring Intermonsoon (SI) and Southwest Monsoon (SWM) seasons, respectively, revealed high spatial and temporal variability in surface saturation (110-2521%). The highest values were observed during the SWM in the inner shelf where coastal upwelling combined with freshwater runoff to produce very strong near-surface stratification. These values might result to a large extent from (CH sub(4)) inputs from coastal wetlands through seasonal runoff as abnormally high saturations (up to approx 13,000%) were recorded in the estuarine surface water. In situ production of (CH sub(4)), favoured by very high biological production in conjunction with the prevalence of suboxic conditions in the upwelled water, could be the other major (CH sub(4)) source. In comparison, sedimentary inputs of (CH sub(4)) seemed to be of lesser importance in spite of previously-reported occurrence of gas-charged sediments in this region. Methane profiles in the open central Arabian Sea showed two maxima. The more pronounced deeper maximum, occurring at 150-200 m depth, was similar to the feature seen elsewhere in the oceans, but was probably intensified here due to an acute oxygen deficiency. It showed some correlation with the subsurface particle maximum characteristics of the denitrifying layer. The dominant mechanism of its formation might be in situ production within particles rather than advection from the continental shelf as concluded by previous workers. The less pronounced and previously unreported shallower maximum, occurring in the well-oxygenated upper 50 m of the water column, was more dynamic probably as a result of variability of the balance between (CH sub(4)) production due to biological activity and its losses through microbial oxidation and air-sea exchange.
dc.language.iso en
dc.publisher Elsevier
dc.rights Copyright [2001]. All efforts have been made to respect the copyright to the best of our knowledge. Inadvertent omissions, if brought to our notice, stand for correction and withdrawal of document from this repository.
dc.subject methane
dc.subject coastal waters
dc.subject offshore
dc.subject carbon cycle
dc.subject coastal upwelling
dc.title Methane in coastal and offshore waters of the Arabian Sea
dc.type Journal Article

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