HR: 1340h
AN: A53B-0873    [Abstracts]
TI: The Warming of Lake Tahoe
AU: * Coats, R N
EM: coats@hydroikos.com
AF: Hydroikos Associates, 2175 E. Francisco Blvd., San Rafael, CA 94901 United States
AU: Perez-Losada, J
EM: jplosada@ucdavis.edu
AF: Department of Civil and Environmental Engineering, University of California, Davis, CA 95616 United States
AU: Schladow, G
EM: gschladow@ucdavis.edu
AF: Department of Civil and Environmental Engineering, University of California, Davis, CA 95616 United States
AU: Richards, R
EM: brichards@ucdavis.edu
AF: Department of Environmental Science & Policy, University of California, Davis, CA 95616 United States
AU: Goldman, C
EM: crgoldman@ucdavis.edu
AF: Department of Environmental Science & Policy, University of California, Davis, CA 95616 United States
AB: We investigated the effects of climate variability on the thermal structure of Lake Tahoe, California-Nevada, 1970-2002, and with principal components analysis and step-wise multiple regression, related the volume-weighted average lake temperature to trends in climate. We then used a 1-dimensional hydrodynamic model to show that the observed trends in the climatic forcing variables can reasonably explain the observed changes in the lake. Trends in the climatic drivers include 1) upward trends in maximum and minimum daily air temperature at Tahoe City; and 2) a slight upward trend in downward long-wave radiation. Changes in the thermal structure of the lake include 1) a long-term warming trend, with the highest rates near the surface and at 400 m, and discernible in the average lake temperature and total heat content of the lake; 2) an increase in the resistance of the lake to mixing and stratification, as measured by the Schmidt Stability and Birge Work; 3) a trend toward decreasing depth of the October thermocline. We found that the upward trend in average lake temperature (0.016 $^{o}$C yr$^{-1}$) is caused by increasing daily air temperature and downward long-wave radiation. At daily to yearly time scales, lake temperature is also correlated with the indices of El Ni\~{n}o-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). The net average heat flux to the lake between 1970 and 2002 was 0.71 W m$^{-2}$, 10.4 times the reported geothermal flux. The long-term changes in the thermal structure of Lake Tahoe may interact with and exacerbate the well-documented trends in the lake's clarity and primary productivity.
DE: 4215 Climate and interannual variability (3309)
DE: 4239 Limnology
DE: 3309 Climatology (1620)
DE: 1803 Anthropogenic effects
DE: 1845 Limnology
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting