Matthew A. Dzieciuch
Scripps Inst. of Oceanogr., IGPP-0225, UCSD, La Jolla, CA 92093
An ongoing experiment, Acoustic thermometry of ocean climate (ATOC), measures the integrated heat content of path through an ocean basin by recording the travel time perturbations of low-frequency sound waves. Anthropogenic CO[sub 2] in the atmosphere is expected to heat the oceans. Many physical processes affect the travel time signal in addition to the greenhouse signal. A partial list includes: internal waves, tides, mesoscale eddies, seasonal and interannual variability. A relevant question is: What is the signal-to-noise ratio of the CO[sub 2] warming signal versus the ambient signal? A synthetic experiment was therefore run to estimate the acoustic signature of the warming signal. Two coupled ocean-atmosphere general circulation models were run with no CO[sub 2] increase and with CO[sub 2] doubling. The GCM output was then used as an input to an acoustic propagation model. The acoustic time series can then be analyzed for climatic trends. The control run is used to estimate the ambient noise processes on long term scales. Shorter time scale processes can also be quantified and signal-to-noise ratios can then be constructed. The spatial properties of the CO[sub 2] signal are nonuniform and therefore maps of the signal strength are also constructed.