Open AccessTurbulent diffusion and transport from a CO 2 lake in the deep ocean
Author(s) -
Haugan Peter M.,
Alendal Guttorm
Publication year - 2005
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2004jc002583
Subject(s) - seawater , advection , stratification (seeds) , water column , turbulence , benthic zone , diffusion , turbulent diffusion , geology , gravity current , oceanography , mixed layer , boundary layer , circumpolar deep water , molecular diffusion , environmental science , atmospheric sciences , mechanics , physics , internal wave , deep water , north atlantic deep water , thermodynamics , seed dormancy , metric (unit) , germination , botany , operations management , dormancy , biology , economics
If liquid CO 2 is stored as a dense “lake” on the deep ocean floor, it is expected to dissolve in seawater. Ocean currents and turbulence can increase the net rate of CO 2 release by several orders of magnitude compared to molecular diffusion. However, density stratification in the seawater created by dissolved CO 2 will tend to reduce vertical mixing. A two‐dimensional numerical study with a high‐resolution advection‐diffusion model, coupled with a general turbulence model, reveals significant modifications of the boundary layer structure above a generic CO 2 lake taken to be 500 m in length and placed in a 10 km domain that is subject to specified far‐field currents in the range of 0.05–0.20 m s −1 . Dissolution rates of order 0.07 μmol cm −2 s −1 , reaching approximately 0.5 μmol cm −2 s −1 during a benthic storm, are predicted. The friction velocity is reduced above the CO 2 lake, and CO 2 concentrations corresponding to excess water densities of up to 0.5 kg m −3 occur in the lower 10 m of the water column. The persistency of this low‐pH, CO 2 ‐enriched water layer in weakly stratified and neutral background conditions in the model suggests that gravity current dynamics are important over considerable distances and should be considered in future larger‐scale models and impact studies.