HR: 09:15h
AN: B41C-05    [Abstracts]
TI: Boat-Based Eddy Covariance Measurements of CO2 and H2O Exchange Over Amazon and Tapajos Rivers and Lakes
AU: * Miller, S
EM: sdmiller@uci.edu
AF: UC Irvine, Earth System Science, Irvine, CA 92697-3100 United States
AU: Freitas, H
EM: helbercf@model.iag.usp.br
AF: University of Sao Paulo, Dept. of Atmospheric Sciences, Sao Paulo, SP 05508-900 Brazil
AU: Read, E
EM: eread@uci.edu
AF: UC Irvine, Earth System Science, Irvine, CA 92697-3100 United States
AU: Goulden, M
EM: mgoulden@uci.edu
AF: UC Irvine, Earth System Science, Irvine, CA 92697-3100 United States
AU: Rocha, H
EM: humberto@model.iag.usp.br
AF: University of Sao Paulo, Dept. of Atmospheric Sciences, Sao Paulo, SP 05508-900 Brazil
AU: Doughty, C
EM: cdoughty@uci.edu
AF: UC Irvine, Earth System Science, Irvine, CA 92697-3100 United States
AB: Recent reports suggest that gas evasion of carbon dioxide from the Amazon river and its tributaries to the atmosphere may play an important role in the regional carbon budget. These gas transfer rates were estimated using air-water concentration gradients and gas transfer coefficients (piston velocities) derived from floating chamber measurements. Chamber techniques have inherent uncertainties due to their effect on the near-surface air turbulence. The micrometeorological technique of eddy covariance is attractive since it is a direct measurement of gas exchange and samples over a much larger area. In August 2004, we mounted equipment on a small riverboat to measure CO2 and H2O fluxes from the rivers and lakes near Santarem, Para. The motion of the boat was recorded using an inertial measurement package combined with a GPS receiver, and subtracted from the measured winds. We experimented with both thin-wall Teflon tubing and headspace equilibrators to measure the concentration of CO2 in the water continuously. Our sampling strategy included both "under-way" measurements and stationary (moored) 24-hour measurements on the Amazon and Tapajos rivers, and lakes connected to these rivers. CO2 concentration in the Amazon river and a connected lake was 3000-5000 ppm, much higher than the Tapajos river and a connected lake (range 400-1200 ppm). The "signal-to-noise" ratio was therefore greater for fluxes measured above the Amazon. Preliminary calculations indicate fluxes of order 1-2 micromoles/m2/s over the Amazon and 0.6-1 micromoles/m2/s over the Tapajos, and the calculated gas transfer velocity agrees with existing ocean-based parameterizations.
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting