The Basal Zone of Ice Caps and Ice Sheets

Abstract

As indicated by Hooke (1977), the steady-state temperature distribution in a polar ice sheet is determined by the following parameters: the rate of influx of geothermal heat at the base, the temperature near the surface (usually the temperature at a depth of 10 m to avoid seasonal variations) and the vertical and horizontal components of the velocity at every point in the glacier. The term steady state is used here to describe a distribution of temperature in space that does not change with time. For a stagnant ice mass everywhere below the pressure melting point, the temperature gradient is determined by the geothermal heat flux. If, for example, the ice mass is 1000 m thick and the temperature gradient is 0.02 °C/m, a surface temperature of -21 °C will induce a basal temperature of -1 °C. If now the surface temperature is -10 °C, the mean temperature gradient through the ice mass must be adjusted such that the basal temperature does not exceed the pressure melting point (i.e. 0.01 °C/m in the ice sheet cited above). Thus, part of the geothermal heat cannot be conducted upward through the glacier and is consumed by melting ice at the sole. If half of the geothermal heat is used in melting ice at the glacier base, then about 1.8 mm of ice would melt per year. Water produced at one place at the base of the ice sheet is then able to move to another place where the temperature regime may be different and where the water might refreeze.In Order to refreeze this water, the temperature gradient at the new location must be greater than some threshold value (0.02 °C/m in the example above).KeywordsCamp CenturyBasal ZoneGeothermal HeatRock GlacierUnfrozen Water ContentThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.