Premelting increases the rate of regelation by an order of magnitude

Alan W Rempel,Colin R Meyer

doi:10.1017/jog.2019.33

Abstract

ABSTRACTGlacier sliding over small obstacles relies on melting on their upstream sides and refreezing downstream. Previous treatments have appealed to ‘pressure melting’ as the cause of the spatial variations in melting temperature that drive thisregelationprocess. However, we show that typical liquid pressure variations across small obstacles are negligible and therefore variations in ice pressure closely approximate variations in effective stress. For a given change in effective stress, the equilibrium melting temperature changes by an order of magnitude more than when the pressure of ice and liquid both change by an equal amount. In consequence, the temperature gradients that drive heat flow across small obstacles are larger than previously recognized and the rate of regelation is faster. Under typical conditions, the transition wavelength at which ice deformation and regelation contribute equally is of m-scale, several times longer than previous predictions, which have been reported to underestimate field inferences.

Highlights

AND SCALING ARGUMENTSTextbook treatments of glacier sliding based on pioneering work by Weertman (1957); Nye (1969); Kamb (1970) describe how glacier motion is facilitated through a combination of ice deformation over larger bed obstacles, and the process of melting and refreezing across smaller obstacles that is referred to as regelation (Cuffey and Paterson, 2010)
The rate of regelation is limited by the conduction of latent heat across the obstacle in response to changes in melting temperature that accompany variations in ice pressure
When the pressure in a liquid differs from that imposed on its adjacent solid, the theory of premelting describes how equilibrium is achieved at a temperature that differs from the bulk melting temperature that holds when the pressures in the two phases are the same (Dash and others, 2006)

Summary

Introduction

AND SCALING ARGUMENTSTextbook treatments of glacier sliding based on pioneering work by Weertman (1957); Nye (1969); Kamb (1970) describe how glacier motion is facilitated through a combination of ice deformation over larger bed obstacles, and the process of melting and refreezing across smaller obstacles that is referred to as regelation (Cuffey and Paterson, 2010). The rate of regelation is limited by the conduction of latent heat across the obstacle in response to changes in melting temperature that accompany variations in ice pressure.

Results

Conclusion