Stable Condition of CO_2 Storage at the Ocean Floor

Abstract

The depth where CO_2 can be stably stored is an important factor to select the storage site and has been thought 3000 m. However this depth was found to be not enough because the seawater above stored CO_2 is eventually saturated with CO_2 hydrate or CO_2 gas. Using newly obtained density data, the required depths where the density of CO_2 is equivalent to that of seawater saturated with CO_2 hydrate and CO_2 gas are evaluated as 3400 m and 3800 m, respectively. In order to prevent the so-called overflow phenomenon discovered by Brewer et al. of Monterey Bay Aquarium Research Institute, the latter depth is required for the stable CO_2 storage. The authors confirmed this conclusion through an in situ experiment conducted at 3941 m depth off California in October 2003.