Program     Evolution of Deep Sea Processes in the South China Sea       Poster Cycling of DIC and DOC in the deep South China Sea as revealed from their radiocarbon ages P-SPS6-05 Xuchen Wang* , Ocean University of China Ling Ding, Ocean University of China Presenter Email: xuchenwang@ouc.edu.cn Radiocarbon measurements of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) in the ocean provide useful information not only on their sources but cycling timescales of each different carbon pools. Here we report our concentration and D14C results measured for both DIC and DOC collected from six deep stations in the South China Sea (SCS). The concentrations of DIC ranged in 1776-2328 μmol/kg and generally increased with depth; while concentrations of DOC ranged in 38-95 μM and decreased rapidly with depth, especially in the upper 200m. Below than 1000 m depth, both DIC and DOC concentrations remained relatively constant. The values of 14C-DIC ranged in 54‰ to -227‰ with high values in the surface and decreased rapidly with depth. The D14C-DOC values were much lower (by -300‰) than D14C-DIC, ranging from -258‰ to -557‰ also decreased rapidly with depth. The calculated 14C ages indicate that DOC were 2000-2500 years (before present) older than DIC. The ages of DOC in the deep water were about 6200 years that is similar to the DOC ages in the deep waters of the Central North Pacific and Southern Pacific. Our 14C-DIC results suggest that the South China Sea is largely influence by the Kuroshio Current and the intermediate water mass has been well mixed to the upper 500 m depth. In contrast, the deep layer (> 1500 m) in the South China Sea has been relatively stable or the water resident time is longer than that in the upper 500m depth. The hydrodynamic mixing and circulation pattern have major influence on the distribution and cycling of DIC and DOC in the SCS especially in the deep waters.