ABSTRACT. We have measured radiocarbon in prebomb known-age shells and coral from the Indian Ocean and southeast Asia to determine marine reservoir age corrections. Western Indian Ocean results show a strong 14 C depletion due to upwelling in the Arabian Sea, and indicate that this signal is advected over a wide area to the east and south. In contrast, the surface waters of the South China Sea contain relatively high levels of 14 C, due in part to the input of well-equilibrated water masses from the western Pacific. The easternmost regions of the Indian Ocean are also strongly influenced by the flowthrough of Pacific waters north of Australia.
We measured apparent marine radiocarbon ages for the Mediterranean Sea, Black Sea, and Red Sea by accelerator mass spectrometry radiocarbon analyses of 26 modern, pre-bomb mollusk shells collected living between AD 1837 and 1950. The marine reservoir (R(t)) ages were estimated at some 390 ± 85 yr BP, 415 ± 90 yr BP and 440 ± 40 yr BP, respectively. R(t) ages in the Mediterranean Sea and Black Sea are comparable to those for the North Atlantic Ocean (<65°N), in accordance with the modern oceanic circulation pattern. The ΔR values of about 35 ± 70 yr and 75 ± 60 yr in the Mediterranean area show that the global box-diffusion carbon model, used to calculate R(t) ages, reproduces the measured marine 14C R(t) ages in these oceanic areas. Nevertheless, high values of standard deviations, larger than measurement uncertainties are obtained and express decadal R(t) changes. Such large standard deviations are indeed related to a decrease of the apparent marine ages of some 220 yr from 1900 AD to 1930 AD in both the Mediterranean Sea and the western North Atlantic Ocean.
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