Topographic effects on CO2, diffusion and dissolution from the seafloor

Abstract

At 3000 meters depth liquid CO2 is denser than seawater and hence will be stored as a “lake” on the deep ocean floor, which is expected to gradually be dissolved in seawater. Ocean currents and turbulence will influence the net rate of dissolution by several orders of magnitude compared to molecular diffusion. On the other hand, density stratification induced by dissolved CO2 will tend to dampen the local turbulence and reduce the vertical mixing. It is well known that local topography will alter the currents and turbulence intensity, and hence, change the dissolution rates. Earlier the dissolution of a CO2 lake has been studied through idealized 3D simulations with a flat bottom using MITgcm coupled with GOTM. This new study includes how topographic depressions affect the dissolution rate and gives also a comparison of how the different coordinate systems affect the results. The lake scenario is modeled in a two dimensional domain using the terrain following coordinate model, Bergen Ocean Model, (http://math.uib.no/BOM/) and the zz-coordinate MIT general circulation model (http://mitgcm.org).