Mekong River discharge and the East Asian monsoon recorded by a coral geochemical record from Con Dao Island, Vietnam

抄録

The offshore flow of the Mekong River is strongly governed by the East Asian monsoon (EAM). Monthly-resolved skeletal carbonate Sr/Ca, Ba/Ca and oxygen isotope (δ¹⁸O_c) data from 1980 to 2005 of a Porites coral from Con Dao Island, ~90 km from the Mekong River mouth, were analyzed for capturing the past flood events and the signal of East Asian winter monsoon. Ba/Ca time series is characterized with intra-annual double peaks, the first large one in March during the dry season and relative small one in August during the wet season. The low values of seawater δ¹⁸O (δ¹⁸O_sw), deduced from both the Sr/Ca ratio and δ¹⁸O_c, in the wet season resulted from precipitation and/or freshwater input from the Mekong River. The difference in the seasonal characteristics of Ba/Ca and δ¹⁸O_sw between flood and no-flood years could be attributed to the seasonal reversal of the regional ocean current derived from the EAM.