The Southern Ocean is an important sink of atmospheric CO2 and the magnitude of the CO2 sink is uncertain because its ability to absorb CO2 changes significantly in the decades.An empirical relationship was deduced based on the in-situ pCO2 in the surface seawater and its main controls including Chl-a and SST obtained during the 26th CHINARE cruise.An extrapolation model was set up combining the empirical relationship with remote sensing data to compute the air-sea carbon fluxes and carbon uptake in the Southern Ocean (south of 50°S).Results of the extrapolation model show that it was a weak source of atmospheric CO2 in the area from 90°E to 90°W (clockwise) and 50°S to 75°S in November 2009.In December 2009,the study area was a weak sink.When the empirical relationship was extended spatially to the whole area from 50°S to 75°S,the results show that in November 2009 the Southern Ocean was a source of 2.8 TgC and in December 2009 it was a sink of-3.5 TgC.The peak flux estimation in 2009 from our results shows that the ability of carbon uptake in the Southern Ocean decreased by 47%compared to the climatological year 2000 of Takahashi et al.(2009).We also estimated the carbon absorption in three ocean sectors namely the south Pacific ocean,the south Indian ocean and the south Atlantic ocean.For the austral summer,the south Atlantic ocean remained a strong carbon sink while the south Indian ocean declined by 40%between 1999 and 2009.