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

Activity concentrations of dissolved and particulate 210Pb and 226Ra in the water column were measured in the eastern Chukchi Sea during summer 2003. 234Th/238U disequilibria were used to estimate the scavenging fluxes of 210Pb from the water column to the underlying sediments. Our results showed that concentrations of 210Pb and its distributions were mainly influenced by mixing processes of water masses and sediment resuspension. The residence times of 210Pb 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 210Pb budget in the water column. The lateral transport fluxes of 210Pb ranged from 17 to 177 Bq/m2/a, comprising up to 63–94% of the total supply of 210Pb in the eastern Chukchi Sea. We hypothesize that the accumulative removal of 210Pb in the Pacific inflow waters during their transport across the Chukchi Sea and the import of 210Pb from sea ice rafted sediments are the two major lateral transport pathways for the import of 210Pb 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.