GLOBAL BIOGEOCHEMICAL CYCLES, DOI:10.1029/2008GB003349 AUXILIARY MATERIAL Oceanic sources, sinks, and transport of atmospheric CO2

In steady-state, that part of the input of inorganic and organic carbon into the ocean by rivers that escapes burial is released back into the atmosphere as a flux of CO2 across the air-sea interface [Sarmiento and Sundquist, 1992]. While the burial rate of carbon on the seafloor of the deeper ocean is reasonably well established (∼0.1 Pg C yr−1 as organic carbon and∼0.1 Pg C yr−1 as CaCO3), the burial in shallow sediments as well as the net input of carbon by rivers beyond the river mouth is poorly established. One reason is that most transport estimates of riverine carbon pertain to a location far upstream of the river mouth, and therefore do not include the myriad of transformation processes that occur in the estuaries and in the very nearshore environments. The most commonly adopted estimate for the river input of carbon is 0.4 Pg C yr−1 in the form of organic carbon, and 0.4 Pg C yr−1 as inorganic carbon [Sarmiento and Sundquist, 1992]. Assuming a burial flux of 0.2 Pg C yr−1