Water column particulate organic carbon modeled fluxes in the ice-frequented Southern Ocean

Abstract

Nine sediment traps deployed in part of the ice-frequented Southern Ocean (Weddell Sea, Ross Sea, and Bransfield Strait) provide the necessary data to compare vertical annual particulate organic carbon (POC) fluxes with ambient ice regimes (annual mean ice concentration) as can be observed by satellite microwave radiometers. Sedimentation in these seasonally ice-covered regions is primarily dependent upon the mean annual ice concentration. We used a similar approach as the Greenland Sea Is Odden–Nordbukta model to develop a semi-empirical model for the Southern Ocean, and found that the vertical POC fluxes are a factor of two smaller than in the Greenland Sea. Applying the model for each individual trap for the years 1979 to 1999 shows that within the biological marginal ice zone (BMIZ), most of the sedimentation takes place within a mean annual ice concentration range of 9–<67%. This range accounts for 77% of the entire sedimentation as compared to 23% for the other sub-areas of the BMIZ, which account for 16% for the range 67–<85%, 2% for the range 85–100%, and 5% for the range 0–<9%. The inter-annual variations in flux are small (2%) ranging from 1.74 to 1.94 g m −2 year −1 at a depth of 500 m, with the fluxes of the western Weddell Sea being similar in magnitude as the Ross Sea (northwest and northeast). The mean annual amount of sedimentation for the years 1979 to 1999 is 32.45±1.06 Mt.