The oceans as a CO2 reservoir

Abstract

The most recent data for the carbon dioxide concentration, alkalinity and partial pressure of carbon dioxide in ocean water are reviewed. The total carbon dioxide content in the oceans is estimated to be 1.39×1020 grams CO2, about 53 times the total atmospheric carbon dioxide content. The oceans contain a greater quantity of CO2 than the amount expected if the oceans were a single homogeneous body of water. This indicates that their capacity is governed by the dynamic processes in the ocean such as the circulation and mixing of ocean water, vertical transpot of carbon by biological processes, and air‐sea CO2 gas exchange. Thus, dynamic models for the carbon cycle in the atmosphere‐ocean system are needed to evaluate the response of the oceanic and atmospheric carbon dioxide reservoirs to the industrial carbon dioxide input and climatic changes. A vertical one‐dimensional and box‐diffusion model, which has been developed by Oeschger et al22, has been used widely and successfully to describe the global carbon cycle. A modified version of their model, in which the size of the land biomass is assumed constant, is presented and used to evaluate the effects of climatic changes on the atmospheric and oceanic reservoirs. It appears that the predicted climatic warming resulting from the industrial carbon dioxide release would cause an increase in the airborne fraction of the industrial carbon dioxide and further accelerate a build‐up of industrial carbon dioxide in the atmosphere. Development of more sophisticated models, which include the ocean circulations, regional differences in the oceans, and climate feedback, is strongly urged for quantitative assessment of the industrial carbon dioxide effects on the climate and the oceanic carbon dioxide reservoir.