Air-sea exchange of CO2 in the Gulf of Kutch,northern Arabian Sea based on bomb-carbon in corals and tree rings |
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Authors: | S Chakraborty R Ramesh S Krishnaswami |
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Institution: | (1) Physical Research Laboratory, 380009 Ahmedabad |
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Abstract: | Radiocarbon analyses were carried out in the annual bands of a 40 year old coral collected from the Gulf of Kutch (22.6°N,
70°E) in the northern Arabian Sea and in the annual rings of a teak tree from Thane (19°14′N, 73°24′E) near Bombay. These
measurements were made in order to obtain the rates of air-sea exchange of CO2 and the advective mixing of water in the Gulf of Kutch. The Δ14C peak in the Thane tree occurs in the year 1964, with a value of ∼630‰, significantly lower than that of the mean atmospheric
Δ14C of the northern hemisphere (∼ 1000‰). The radiocarbon time series of the coral was modelled considering the supply of carbon
and radiocarbon to the gulf through air-sea exchange and advective water transport from the open Arabian Sea. A reasonable
fit for the coral data was obtained with an air-sea CO2 exchange rate of 11–12 mol m−2 yr−1, and an advective velocity of 28 m yr−1 between the Arabian Sea and the Gulf of Kutch; this was based on a model generated time series for radiocarbon in the Arabian
Sea. The deduced velocity (∼ 28 m yr−1) of the advective transport of water between the gulf and the Arabian Sea is much lower than the surface tidal current velocity
in this region, but can be understood in terms of net fluxes of carbon and radiocarbon to the gulf to match the observed coral
Δ14C time series. |
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Keywords: | Air-sea interaction CO2 exchange Gulf of Kutch coral tree rings bomb radiocarbon |
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