Dissolved aluminum in the Yellow Sea and East China Sea – Al as a tracer of Changjiang (Yangtze River) discharge and Kuroshio incursion

Abstract

The distributions of dissolved aluminum in the Yellow Sea and East China Sea were investigated in May 2001 and September 2002, and in the Changjiang (Yangtze River) Estuary in July 2001. The sampling positions were essentially located on a southeast transect from the Changjiang Estuary to the Ryukyu Islands (i.e. PN section) in the East China Sea, with a few stations in the Yellow Sea. The distribution of aluminum in the Yellow Sea showed the effect of land-source input from the adjacent rivers and the Changjiang, with obvious seasonal variations. The impact of Changjiang terrestrial materials over the continental shelf was shown at the PN section. The mean concentrations of 47 and 89 nM of Al were observed off the Changjiang in the spring and autumn, respectively, and concentrations of 16 nM could be seen in the Kuroshio Subsurface Water. Using three distinct aluminum-salinity end-members, it was determined that the contribution of the Changjiang in the autumn was the highest (56.6%) at the station nearest the Changjiang Estuary, and decreased seaward along the PN section. At a distance of 250 km from the Changjiang mouth, the freshwater input was hardly seen and the incursion of Kuroshio waters became dominant. Combining the different inputs from the Changjiang, atmospheric deposition, Kuroshio waters and Taiwan Current Warm Waters with the total amount of Al, a simple budget was established for the East China Sea Shelf. The results revealed an average residence time of 339 ± 118 days for dissolved Al.