If you are using
Navigator 4.x
or
Internet Explorer 4.x
or
Omni Web 4.x
, this site will not render
correctly!
gfdl on-line bibliography > 2001 citations
Comparison of two approaches to quantify anthropogenic CO2 in the ocean: Results from the northern Indian Ocean
| Coatanoan, C., C. Goyet, N. Gruber, C. L. Sabine, and M. Warner, 2001: Comparison of two approaches to quantify anthropogenic CO2 in the ocean: Results from the northern Indian Ocean. Global Biogeochemical Cycles, 15(1), 11-25. |
Abstract: This study compares two recent estimates of anthropogenic
CO2 in the northern Indian Ocean along
the World Ocean Circulation Experiment cruise I1 [Goyet et al., 1999; Sabine
et al., 1999]. These two studies employed two different approaches to separate
the anthropogenic CO2 signal from the
large natural background variability. Sabine et al. [1999] used the  C*
approach first described by Gruber et al. [1996], whereas Goyet et al [1999]
used an optimum multiparameter mixing analysis referred to as the MIX approach.
Both approaches make use of similar assumptions in order to remove variations
due to remineralization of organic matter and the dissolution of calcium
carbonates (biological pumps). However, the two approaches use very different
hypotheses in order to account for variations due to physical processes
including mixing and the CO2 solubility
pump. Consequently, substantial differences exist in the upper thermocline
approximately between 200 and 600 m. Anthropogenic CO2
concentrations estimated using the C*
approach average 12 ± 4 µmol kg -1
higher in this depth range than concentrations estimated using the MIX approach.
Below ~800 m, the MIX approach estimates slightly higher anthropogenic CO2
concentrations and a deeper vertical penetration. Despite this compensatory
effect, water column inventories estimated in the 0-3000 m depth range by
the C*
approach are generally ~20% higher than those estimated by the MIX approach,
with this difference being statistically significant beyond the 0.001 level.
We examine possible causes for these differences and identify a number of
critical additional measurements that will make it possible to discriminate
better between the two approaches. |