HR: 08:40h
AN: B41F-03    [Abstracts]
TI: Carbon Cycling in Lake Superior: Impact on Upper Midwest Regional Carbon Balance
AU: * Desai, A R
EM: desai@aos.wisc.edu
AF: Dept of Atmospheric and Oceanic Sciences, University of Wisconsin-Madison, 1225 W Dayton St, Madison, WI 53706, United States
AU: McKinley, G A
EM: gamckinley@wisc.edu
AF: Dept of Atmospheric and Oceanic Sciences, University of Wisconsin-Madison, 1225 W Dayton St, Madison, WI 53706, United States
AU: Urban, N R
EM: nurban@mtu.edu
AF: Dept. of Civil and Environmental Engineering, Michigan Technological University, 1400 Townsend Dr., Hougton, MI 49931, United States
AU: Wu, C H
EM: chinwu@engr.wisc.edu
AF: Dept. of Civil and Environmental Engineering, University of Wisconsin-Madison, 1415 Engineering Dr., Madison, WI 53706, United States
AB: Understanding the regional surface-atmosphere exchange of carbon dioxide of inland water bodies is important for accurately quantifying and scaling regional continental carbon budgets. It is widely recognized that many lakes are net sources of CO₂ to the atmosphere. However, our ability to predict CO₂ fluxes from any particular lake remain rather limited. In a landscape rich in lakes and wetlands such as the upper Midwest Great Lakes region, assumptions that CO₂ fluxes from lakes are negligible seem disingenuous and bear potential for adding error to estimates of regional carbon flux. The Laurentian Great Lakes cover 25 percent of the land area of the 8 Great Lakes states, and CO₂ emission and seasonal cycling from them may be comparable to local terrestrial ecosystems. CO₂ fluxes from Lake Superior are of particular interest because they may directly impact CO₂ observations at nearby AmeriFlux towers. DOC inputs to lakes are considered a major controlling factor on lake CO₂ concentrations. Recent findings estimated the turnover time of dissolved organic carbon (DOC) in Lake Superior to be about 8 years. We have collected lake water samples, analyzed above lake CO₂ concentrations, and started coupling an ecosystem-carbon module to an existing high resolution hydrodynamic model of Lake Superior in an attempt to estimate these fluxes and their spatial and temporal variability. Here we present initial results from this effort and place these reseults in context with regional terrestrial CO₂ fluxes. Municipal water intakes were analyzed for water properties. The measured values for alkalinity and pH in the Lake Superior samples were within the range previously reported for the lake. Additionally, CO₂ concentrations measured above Lake Superior were shown to be elevated above what would be expected on land, with a gradient of increasing concentrations with increasing wind travel distance from shore. Both of these initial measurements suggest that Lake Superior can be a significant source of CO₂. Modeling results reveal the complex flows and patterns that will need to be considered to estimate whole-lake annual CO₂ emissions.
UR: http://atlantic.aos.wisc.edu/~superior/wiki/
DE: 0466 Modeling
DE: 0746 Lakes (9345)
DE: 4255 Numerical modeling (0545, 0560)
DE: 4805 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4912)
DE: 4806 Carbon cycling (0428)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting