Abstract:

During the Second Chinese National Arctic Expedition (CHINARE) from July to September 2003, depth profiles of dissolved and particulate ²³⁴Th in upperwater columns were collected at two stations of BR03 and BR24 in the Bering Sea. ²³⁴Th was sampled by using a traditional Fe(OH)₃ co-precipitation technique, which is a reliable approach to ²³⁴Th measurement. We observed ²³⁴Th excess at station BR03 below the euphotic zone, which was possibly due to the intensive remineralization of particulatematter. Particulate organic carbon ( POC ) export fluxes were estmiated from a one-dmiensional irreversible steady state model of ²³⁴Th fluxes together with measurements o f the POC/²³⁴Th ratio on the suspended particles. The POC export fluxes from the euphotic zone were 11. 66 and 11. 69 mmol C m^-2 d^-1 at BR03 and BR24 stations, respectively. The ratios of POC fluxes to prmiary production at the two stations were about 0. 5 and 0. 59, respectively, probably due to the presence of large phytoplankton ( in particular diatoms) .

Key words: ²³⁴Th /238U disequilibria, euphotic zone, particulate organic carbon, Bering Sea