Seasonal and interannual variability of particulate organic carbon within the Southern Ocean from satellite ocean color observations

We use field data of particulate organic carbon (POC) concentration and spectral remote-sensing reflectance, R-rs(lambda), to develop an empirical algorithm for estimating POC from ocean color in the Southern Ocean. The algorithm based on the band ratio R-rs(443)/R-rs(555) is used in conjunction with Sea-viewing Wide Field-of-View Sensor satellite data to demonstrate seasonal and interannual variability in POC from 1997 to 2007. The surface POC concentrations generally range from 30 to 120 mg m(-3). On a whole basin scale (south of 35 degrees S), the monthly means are mostly 70-80 mg m(-3). The seasonal signal is weakest at lower latitudes within the Sub-Antarctic Zone and most pronounced at higher latitudes (>55 degrees S). The area-integrated stock of water column POC in the upper 100 m shows small interannual variations and no clear evidence for long-term trend during the examined 10 year period. The seasonal maximum of the POC stock occurs in December and reaches a value of about 0.6 Pg of carbon for the entire basin south of 35 degrees S. The seasonal range of area-normalized POC is between about 5.5 and 6.6 g m(-2). The region south of 55 S provides a dominant contribution to the accumulation of POC within the Southern Ocean during the productive period of the season. During the austral spring, the area-normalized POC accumulates in these high-latitude waters at rates from about 0.2 to 0.7 g m(-2) month(-1). The comparison of these rates with large-scale satellite-based estimates of net primary production indicates that only a small fraction (<10%) of production accumulates as POC.