NARROWING THE UNCERTAINTY FOR DEEP-OCEAN INJECTION EFFICIENCY

摘要

Only ocean models can predict how efficient the ocean is in sequestering CO_2 by direct injection. Data is not available to directly evaluate model results in this regard, due to the century time scales required for the deep ocean waters to mix and be brought back to the surface. Ten ocean general circulation models (OGCM) have been compared within the framework of an international project to obtain site-specific efficiencies and corresponding uncertainties. Here we show that across the range of models there is a correlation between global injection efficiency and global metrics for CFC-11, natural Δ~(14)C, and bomb Δ~(14)C. These correlations provide support for using these global tracer metrics to help narrow the uncertainty range for the 3000-m injection efficiency. After rejecting the models that do not meet these global tracer criteria, the range in efficiencies becomes four times narrower, dropping from 71 ±22% to 70±6% in year 2500.