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The glacier sedimentary system
Published in Richard J. Chorley, Stanley A. Schumm, David E. Sugden, Geomorphology, 2019
Richard J. Chorley, Stanley A. Schumm, David E. Sugden
Regelation slip occurs when ice at the pressure melting point moves across a series of bumps. Ice melts under the influence of high pressures on the upstream side of the obstacle. The meltwater produced then flows round the bump to the downstream side where the pressure is lower and it refreezes to form regelation ice. The process is most effective when the latent heat released by freezing can be transferred from the downstream side of the obstacle through the rock and assists in further melting on the upstream side. Such a transfer occurs most efficiently on small obstacles generally less than 10 cm across. The rate of regelation slip (Vpm) can be calculated for an idealized glacier bed from the following equation: Vpm=CK〈τ〉R2Lρiℓ
Glacial geology
Published in Barry G. Clarke, Engineering of Glacial Deposits, 2017
As ice slides across the interface, it encounters obstacles at various scales giving rise to regelation sliding and enhanced creep. Regelation occurs when the ice encounters an obstacle; the interface pressure increases, melting the ice, which allows the ice to slide over the obstacle. As it passes the obstacle, the pressure drops refreezing the ice. The strain rate of ice depends on the shear stress, and as the shear stress increases when the ice encounters an obstacle, the strain rate increases. This is known as enhanced creep. Regelation dominates for smaller obstacles; enhanced creep for larger particles. Water is necessary for a glacier bed to slide to lubricate the interface.
The philosopher in the kitchen: the role of mathematical modelling in explaining drumlin formation
Published in GFF, 2018
The recent programme of research on the bedforms exposed under Múlajökull, Iceland (McCracken et al. 2016) represents a major achievement in glaciological research, comparable to the investigations on Variegated Glacier, Alaska in the 1970s and 1980s. Múlajökull is a surging glacier in Iceland, whose advances and subsequent retreats have revealed the formation of drumlins. Just as in the Variegated work, meticulous observations have led to the construction of a theoretical model designed to coincide with the observations (Iverson et al. 2017). The principal feature in which this model differs from others lies in the idea that sediment transport occurs by regelation infiltration, i.e., the sediment is frozen on to the base of the glacier and then released by enhanced melting as the ice surges forward.