Principal Investigator: Rik Wanninkhof
Collaborating scientist(s):
In collaboration with:
Dr. Jim Butler, CMDL
Dr. Chris Fairall, ETL
Dr. Richard Feely, PMEL
Dr. Pieter Tans, CMDL
Objective: Directly measure the air-sea flux of CO2 and relate it to environmental forcing.
Description: Current large uncertainties in the air-sea flux of CO2 prevent us from verifying the partitioning of fossil fuel CO2 between the ocean and the terrestrial biosphere. This limits our ability to realistically model future atmospheric CO2 levels. By measuring the flux using direct flux measurements such as the relaxed eddy accumulation, eddy correlation and gradient methods we can establish robust relationships between environmental forcing and gas exchange on short time scales.
Method: Most flux calculations rely on empirical relationships of gas transfer with wind speed which have a significant uncertainty associated with them (Figure 1) Techniques are now in hand to improve our estimates of air-sea fluxes. We propose to measure air-sea fluxes directly on 1/2 hour time scale in the air boundary layer by three independent direct air side measurements; to parameterize this flux (and gas transfer velocity) with environmental forcing functions; and to compare the results with measurement of gas transfer velocities from gas mass balances in the ocean. The latter verification is essential to validate the relaxed eddy accumulation method for measurement of CO2 fluxes over the ocean.
Accomplishment: A proposal to perform this work in the North Atlantic in June 1996 has been funded. A dozen different research groups will participate in the cruise (GAS EX-98)
Key reference:
MacIntyre, S., R. Wanninkhof, and J.P. Chanton, Chapter 3, Trace gas exchange across the air-water interface in freshwater and coastal marine environments, in Methods in Ecology- Biogenic Trace Gases: Measuring Emissions from Soil and Water, edited by P.A. Matson, and R.C. Harriss, pp. 52-97, Blackwell Science, Cambridge, Mass, 1995.

Wanninkhof, R., Relationship between gas exchange and wind speed over the ocean., J. Geophys. Res., 97, pp. 7373-7381, 1992.

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