Boat-Based Eddy Covariance Measurements of CO2 Exchange Over Amazon and Tapajos Rivers and Lakes
Miller, State University of New York at Albany, firstname.lastname@example.org
Goulden, University of California at Irvine, email@example.com
Rocha, Universidade de Sao Paulo, firstname.lastname@example.org
Read, University of California at Irvine, email@example.com
Freitas, Universidade de Sao Paulo, firstname.lastname@example.org
Recent reports based on floating chamber measurements 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 (Richey et al., 2002). 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 and measured CO2 and H2O fluxes from rivers and lakes near Santarem, Para, over a 10-day period. Our sampling strategy included both “under-way” measurements and stationary (moored) 24-hour measurements, and floating chambers were deployed in situ with the eddy flux measurements. The CO2 concentration in the Amazon river and a connected lake were high (3000-5000 ppm) compared to the Tapajos River and a connected lake (400-1200 ppm). The calculated piston velocity for the Amazon data agrees with over-ocean parameterizations for air-water gas exchange. The piston velocity calculated from the Tapajos data were several times as large as those on the Amazon, possibly due to a shallow upwind fetch while the boat was moored on the Tapajos.