Unusually large210Po deficiencies relative to210Pb in the Kuroshio Current of the East China and Philippine seas

Three vertical water profiles of {sup 210}Pb and {sup 210}Po have been measured in the East China and Philippine seas. All the profiles show a large {sup 210}Po deficiency of {approximately} 8 dpm/cm{sup 2} relative to {sup 210}Pb in the top {approximately} 1,000 m of the water column. Based on the {sup 210}Po deficiency, the steady state flux for {sup 210}Po removal from the surface water is estimated to be 14 dpm cm{sup {minus}2}/yr. The {sup 210}Po/{sup 210}Pb ratio of sinking particles will be too high unless an additional source of {sup 210}Pb into the surface is accounted for. Thus the large {sup 210}Po deficit is probably caused by the increased atmospheric input of {sup 210}Pb without any significant {sup 210}Po, which is focused in the Kuroshio region by isopycnal transport, and the preferential scavenging of {sup 210}Po relative to {sup 210}Pb by settling particles. The transient model calculations indicate that the model can account for the observed high excess {sup 210}Pb inventory and large {sup 210}Po deficiency in the water column if focusing of atmospherically derived {sup 210}Pb in the Kuroshio water is a factor of 2-3 more than the local input. Such lateral redistribution by the western Northmore » Pacific gyre circulation is not inconsistent with the deeper penetration and the high water column inventories of anthropogenic substances observed in this region.« less