Importance of lateral transport processes to 210Pb budget in the eastern Chukchi Sea during summer 2003

Activity concentrations of dissolved and particulate Pb-210 and Ra-226 in the water column were measured in the eastern Chukchi Sea during summer 2003. Th-234/U-238 disequilibria were used to estimate the scavenging fluxes of Pb-210 from the water column to the underlying sediments. Our results showed that concentrations of Pb-210 and its distributions were mainly influenced by mixing processes of water masses and sediment resuspension. The residence times of Pb-210 in the eastern Chukchi Sea ranged from 5 to 103 d. Short residence times were mostly observed at the shelf stations, indicating a more effective particle scavenging in the shelf region. A mass balance model was constructed to evaluate the contribution of lateral transport to Pb-210 budget in the water column. The lateral transport fluxes of Pb-210 ranged from 17 to 177 Bq/m(2)/a, comprising up to 63-94% of the total supply of Pb-210 in the eastern Chukchi Sea. We hypothesize that the accumulative removal of Pb-210 in the Pacific inflow waters during their transport across the Chukchi Sea and the import of Pb-210 from sea ice rafted sediments are the two major lateral transport pathways for the import of Pb-210 to the eastern Chukchi Sea. Our results highlight the importance of lateral transport processes to the geographical distribution of particle-reactive elements and their biogeochemical cycles in the Arctic Ocean. (C) 2012 Elsevier Ltd. All rights reserved.