Frost boils and soil ice content: field observations

Our aim is to measure and explain the seasonal changes in soil ice content in the frost boils of Galbraith Lake, Alaska. Instruments were installed in a frost boil to monitor the ground surface position and soil state over a period of 4 years. By comparing the subsidence and thaw rates, we calculate the soil ice content as a function of depth. Measured soil temperatures, liquid water contents and bulk apparent thermal conductivities are used to estimate latent heat production and release in the soil. The frost boil heaves during freezing and settles during thaw while the surrounding tundra heaves negligibly, but subsides measurably. Despite large changes in freezing rates from year to year, total heave and its distribution across the frost boil are similar between years. Winter air temperature and snow depth influence the freezing rate and ice distribution as a function of depth, but not the overall heave. This suggests that heave is controlled by water availability rather than the rate of heat removal from the soil. Areal ground subsidence rates between 2 and 5 cm/yr are due to the disappearance of ice at the base of the active layer, raising the possibility of ongoing thermokarst expansion around Galbraith Lake.

[1]  A. L. Washburn.  CLASSIFICATION OF PATTERNED GROUND AND REVIEW OF SUGGESTED ORIGINS , 1956 .

[2]  J. Boike,et al.  Quantifying the thermal dynamics of a permafrost site near Ny‐Ålesund, Svalbard , 2001 .

[3]  J. R. Mackay.  The origin of hummocks, western Arctic coast, Canada , 1980 .

[4]  S. Zoltai,et al.  Some Nonsorted Patterned Ground Types in Northern Canada , 1981 .

[5]  Gaylon S. Campbell,et al.  A thermodielectric analyzer to measure the freezing and moisture characteristic of porous media , 2001 .

[6]  W. Gould,et al.  Frost‐boil ecosystems: complex interactions between landforms, soils, vegetation and climate , 2004 .

[7]  L. Hinzman,et al.  A distributed thermal model for calculating soil temperature profiles and depth of thaw in permafrost regions , 1998 .

[8]  J. R. Mackay,et al.  Cryostatic pressures in nonsorted circles (mud hummocks), Inuvik, Northwest Territories , 1976 .

[9]  G. Liston,et al.  Snow-Ground Interface Temperatures in the Kuparuk River Basin, Arctic Alaska: Measurements and Model , 2002 .

[10]  G. S. Campbell,et al.  An Analysis of Sensible and Latent Heat Flow in a Partially Frozen Unsaturated Soil , 1978 .

[11]  Comparing electronic probes for volumetric water content of low-density feathermoss , 2005 .

[12]  C. Burn.  The active layer: two contrasting definitions , 1998 .

[13]  Douglas L. Kane,et al.  Measuring thermal conductivity in freezing and thawing soil using the soil temperature response to heating , 2006 .

[14]  Kevin O'Neill,et al.  Exploration of a Rigid Ice Model of Frost Heave , 1985 .

[15]  Willem Bouten,et al.  Assessing temporal variations in soil water composition with time domain reflectometry , 1995 .

[16]  Vladimir E. Romanovsky,et al.  Thawing of the Active Layer on the Coastal Plain of the Alaskan Arctic , 1997 .

[17]  Vladimir E. Romanovsky,et al.  The role of snow cover in the warming of arctic permafrost , 2003 .

[18]  R. Schulin,et al.  Calibration of time domain reflectometry for water content measurement using a composite dielectric approach , 1990 .

[19]  B. Vliet-Lanoë.  Differential Frost Heave, Load Casting and Convection: Converging Mechanisms; a Discussion of the Origin of Cryoturbations , 1991 .