234Th-derived particulate organic carbon export flux in the western Arctic Ocean

To evaluate the particle dynamics and estimate the POC (particulate organic carbon) export flux from the euphotic zone in the western Arctic Ocean, Th-234-U-238 disequilibrium was applied during the second Chinese National Arctic Research Expedition (July 15 September 26, 2003) The POC export fluxes are estimated from the measured profiles of the Th-234/U-238 activity ratios and the POC/PTh ratios The average residence times of the particulate and dissolved Th-234 in the euphotic zone are 33 d and 121 d, and their average export fluxes are 480 dpm/m(2)d and 760 dpm/m(2)d respectively The scavenging and removal processes of particle reactive elements are active in the upper layer of the Chukchi Sea The average residence time of Th-234 increases from shelf to basin, while the export fluxes of Th-234 decrease The estimated POC export fluxes from the euphotic zone vary from 2 1 to 20 3 mmol/m(2)d, indicating that the western Arctic Ocean is an important carbon sink in summer due to efficient biological pump