THE CAPACITY OF THE DEEP OCEANS TO ABSORB CARBON-DIOXIDE

A research program has been conducted to investigate the ability of the deep ocean to absorb CO2, with two main goals 1) to determine the capacity of the ocean basins to absorb CO2 and 2) to examine the influence of calcium carbonate dissolution and future CO2 emissions patterns on this capacity. To fulfill the first goal, inventories were made of calcium carbonate present in surficial sediments as well as carbonate ion concentrations in deep ocean water. From this information, estimates of the total capacity of the ocean basins to absorb CO2, without significantly altering the chemical balance of the oceans, were developed. To evaluate the influence of calcium carbonate dissolution and future CO2 emission patterns on the ocean's capacity to absorb CO2, a ID model of the carbon cycle was developed. A vertical diffusion model of the oceans with carbon chemistry has been adapted to simulate the discharge of fossil fuel CO2 below the thermocline. This is a four box model representing the atmosphere, the surface ocean, the deep ocean, and surficial sediments. The model atmosphere and surface ocean are internally well mixed whereas the deep ocean and sedimentary boxes are divided into diffusively mixed levels. Disposed CO2 evasion rates obtained with this model are very similar to those obtained with a 3D ocean carbon cycle model and indicate that calcium carbonate dissolution can significantly influence the long term effectiveness of CO2 disposal in the deep ocean.