A BOTTOM GRAVITY CURRENT MODEL FOR CO2-ENRICHED SEAWATER

A bottom gravity current model, including chemistry, has been used to study the behaviour of heavy, CO2-enriched seawater released on a sloping seabed. The model has been fitted to the emission of CO2 from a 2 GW gas power plant, and the CO2-enriched seawater is released at a depth of 300 m. A plume is modelled for three different areas; the Norwegian Sea, the north Atlantic and the north Pacific. Temperature and salinity profiles have been used to simulate the vertical density gradient for each of the areas. The numerical values of the different model parameters are discussed, and special attention is paid to the bottom friction parameter. It is argued that natural bottom gravity currents need a bottom friction parameter between 0.01 and 0.1, which is one to two orders of magnitude higher than the drag coefficient commonly used in tidal modelling. It is shown that a friction parameter near 0.01 leads to quick dilution of the plume, but that the plume may reach the deep ocean if the friction parameter is near 0.1. Furthermore, it is shown that the density profiles in the Atlantic and Pacific tend to reduce the excess plume density, whereas a plume released at 300 m depth in the Norwegian Sea may transport CO2 to great depths.