The structural, geometric and volumetric changes of a polythermal Arctic glacier during a surge cycle: Comfortlessbreen, Svalbard

Various parameters of the most recent surge of the polythermal glacier Comfortlessbreen in northwest Svalbard, have been assessed through a combination of remote sensing and ground observations. Analysis of a digital elevation model time-series shows a marked change in the geometry of the glacier from quiescence (1990 and earlier) into the late surge phase (2009). The transfer of 0.74km ³ of ice caused up to 80m of surface drawdown in the reservoir area, above the equilibrium line, whilst ice built up in a spatially concentrated manner in the receiving zone, below the equilibrium line. A ramp of ice, c. 100m above quiescent level, developed in the lower reaches of the glacier late in the surge. Also in the lower reaches of the glacier, structures attributable to the passage of a kinematic wave are identified and the migration of a surge front on the glacier is thus inferred. In a conceptual model, we consider that a bend in the valley, in which the glacier resides, and convergence with tributary glaciers, to be significant factors in the style of surge evolution. Their flow-restrictive interference results in slow initial mass-transfer and the growth of a surge front within 3-4km of the terminus.