HR: 1340h
AN: B53A-0937    [Abstracts]
TI: Using Riverboat-Mounted Eddy Covariance for Direct Measurements of Air-water Gas Exchange in Amazonia
AU: * Miller, S D
EM: smiller@albany.edu
AF: suny albany, 251 fuller rd l317, albany, nY 12203, United States
AU: Freitas, H
EM: helber@model.iag.usp.br
AF: university of sao paulo, rua matao, sao paulo, sp 05508, Brazil
AU: Read, E
EM: eread@uci.edu
AF: university of california at irvine, croul hall, irvine, ca 92697, United States
AU: Goulden, M L
EM: mgoulden@uci.edu
AF: university of california at irvine, croul hall, irvine, ca 92697, United States
AU: Rocha, H
EM: humberto@model.iag.usp.br
AF: university of sao paulo, rua matao, sao paulo, sp 05508, Brazil
AB: Gas evasion from Amazonian rivers and lakes to the atmosphere has been estimated to play an important role in the regional budget of carbon dioxide (Richey et al., 2002) and the global budget of methane (Melack et al., 2004). These flux estimates were calculated by combining remote sensing estimates of inundation area with water-side concentration gradients and gas transfer rates (piston velocities) estimated primarily from floating chamber measurements (footprint ~1 m²). The uncertainty in these fluxes was large, attributed primarily to uncertainty in the gas exchange parameterization. Direct measurements of the gas exchange coefficient are needed to improve the parameterizations in these environments, and therefore reduce the uncertainty in fluxes. The micrometeorological technique of eddy covariance is attractive since it is a direct measurement of gas exchange that samples over a much larger area than floating chambers, and is amenable to use from a moving platform. We present eddy covariance carbon dioxide exchange measurements made using a small riverboat in rivers and lakes in the central Amazon near Santarem, Para, Brazil. Water-side carbon dioxide concentration was measured in situ, and the gas exchange coefficient was calculated. We found the piston velocity at a site on the Amazon River to be similar to existing ocean-based parameterizations, whereas the piston velocity at a site on the Tapajos River was roughly a factor 5 higher. We hypothesize that the enhanced gas exchange at the Tapajos site was due to a shallow upwind fetch. Our results demonstrate the feasibility of boat-based eddy covariance on these rivers, and also the utility of a mobile platform to investigate spatial variability of gas exchange.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0452 Instruments and techniques
SC: Biogeosciences [B]
MN: 2007 Fall Meeting