234Th-derived particulate organic carbon export in the Prydz Bay, Antarctica

Abstract

234Th activities in sea water were measured using Fe(OH)3 co-precipitation and beta counting at six stations in Prydz Bay in March 2008 during the 24th Chinese National Antarctic Research Expedition. Total 234Th activities ranged from 0.96 to 2.44 dpm L−1 with an average of 1.61 dpm L−1, showing an apparent deficit with respect to 238U due to scavenging and export with particles. With a one-dimensional steady state model, 234Th export fluxes were converted to particulate organic carbon (POC) export using bottle ratios of POC concentrations to particulate 234Th activities on suspended particles. POC fluxes at the depth of 100 m varied between 33 and 297 mmol m−2 day−1, comparable to prior work in the same region and higher than those of some other sea areas in the Southern Ocean, and indicated efficient running of biological pump in Prydz Bay. The results could be helpful to expand the knowledge of carbon cycle in seasonally ice-covered coastal regions around Antarctica.