Influence of frozen ground on spatial soil moisture patterns in the Subarctic Canadian Shield


X.J. (May) Guan, C. Spence and C. Westbrook, University of Saskatchewan, CANADA

ABSTRACT

Seasonally or perennially frozen ground acts as a near-impermeable layer that affects the movement of soil water over much of the world, but the influence of frozen ground on surface soil moisture patterns needs to be better understood in order to discern its impact on catchment runoff.  To determine how active layer depth influences the dynamics of spatial and temporal surface soil moisture patterns, three soil-filled sites were studied in a typical subarctic Canadian Shield basin underlain with discontinuous permafrost.  To provide explanations for the measured soil moisture change, the water budget at each of the three sites was also examined.  Results show correlation between frost table and surface soil moisture pattern changes at two of the three sites.  The wettest surface soils were often coincident with locations of deepest thaw depth due to the transfer of latent heat accompanying runoff.  This is in direct contrast to landscapes without frozen ground, where surface soil moisture content can be lowest at thick soil locations.  The findings indicate that the presence of frozen ground creates a diverse and dynamic soil moisture pattern on the landscape.  Greater certainty in patterns of water detention and retention in soil-filled areas with frozen ground will help improve understanding of catchment runoff response in cold regions.  The results from this project add a cold region perspective to the understanding of the dynamics of surface soil moisture patterns in relation to hydrological connectivity at the catchment scale.