Heat and Moisture Exchange in a Permafrost Active Layer, Churchill, Manitoba

Abstract

<p>This thesis examines heat and moisture exchanges in the active layer of wet tundra soils during freeze-back and thaw. Measurements of rainfall, snow depth, air and soil temperature, soil moisture, and frost heave were recorded daily. Net radiation, soil heat exchange from soil solids and soil moisture, and soil latent heat exchange were calculated. It was determined that soil moisture is the most significant factor influencing soil heat exchange. A prolonged zero curtain effect of 4 to 6 weeks was related to high soil moisture levels. Soil heat exchange as a percentage of net radiation was 10% during snowmelt, decreasing to 3.5% by mid-summer. The latent heat released upon freezing or thawing of soil moisture can increase heat exchange as a percentage of net radiation to 258% during freeze-back. The calculated frost heave of 3 cm indicates that soil moisture was transferred to the freezing front to produce the measured 4.35 cm of heave. These results apply to wet tundra soils with a constant soil moisture.</p>