| Reconstruction of the 1972 surface thermal regime at Sherman Crater and the Dorr Fumarole Field of Mount Baker, based on seven aerial infrared surveys (l970-73) and on thermistor measurements relayed through a Landsat data collection platform, permits an assessment of Mount Baker's heat exchange with the atmosphere before thermal emission increased in 1975. Calibrated infrared images obtained in November 1972, contoured for apparent radiometric temperature and corrected for atmospheric attenuation and surface emissivity, indicate a differential radiant-flux value of 1.0 +/- 0.6 megawatt for Sherman Crater. Total heat discharge from the crater was estimated at 11 +/- 6 megawatts, which includes less than 8 megawatts from fumarolic emission and advective loss. Several methods were used in combination to produce this estimate, including a modified two-point differential geothermal-flux model based on the heat balance of the ground surface and on surface and air temperatures (the model was adapted for use with infrared-scanner output). Similar calculations applied to infrared images and field data for 1975 yield a differential radiant flux of 3 +/- 1.7 megawatts and a total heat discharge of 80 +/- 44 megawatts, including advective losses of about 28 megawatts from ice melt and melt-water drainage and direct losses of 38 +/- 38 megawatts from fumaroles and vapor plumes. Heat loss by radiation represented 9 percent of the total discharge in 1972 and 4 percent in 1975. The Bowen ratio, R, linking heat loss by conduction and turbulence to that by evaporation was 0.3. The estimated net energy yield in 1975 exceeded that in 1972 by 2.1 x 1015 joules per year. -- Friedman and Frank, 1980 |
