Glacier Ablation Zones Research Articles

The surface energy balance of an active ice-covered volcano: Villarrica Volcano, southern Chile

AbstractThe energy balance of bare snow and tephra-covered ice near the glacier equilibrium line elevation on Villarrica Volcano, southern Chile, was investigated during 2004 and 2005, combining meteorological, surface temperature and ablation measurements with energy balance modelling. A tephra thermal conductivity of 0.35 Wm–1 K–1, and a critical tephra thickness of <5mm at which ablation is reduced compared to bare snow, were obtained from field data. These low values are attributable to the highly porous lapilli particles which make up most of the surface material. Modelled melt totals in the January to March period were 4.95 m and 3.96 m water equivalent (w.e.) in 2004 and 2005, respectively, compared with ∽0.5mw.e. melt for ice buried by >0.1m tephra. Windblown tephra impurities lowered snow albedo, but increased snowmelt by only an estimated 0.28mw.e. over the same period. The net mass balance impact of supraglacial tephra at Villarrica Volcano is therefore positive, as thick ash and lapilli mantle most of the glacier ablation zones, probably reducing annual ablation by several metres w.e. In the accumulation seasons, frequent melting events were recorded with modelled daily snowmelt rates of up to 50 mmw.e.

A Surge of Bualtar Glacier, Karakoram Range, Pakistan: A Possible Landslide Trigger

AbstractBualtar Glacier, Karakoram Range, northern Pakistan, surged during the spring and early summer of 1987. This followed a major episode of three landslides which impacted part of the glacier ablation zone on 30–31 July 1986. In May 1987, surface velocities of 7 m d−1 were measured at one profile down-glacier from the landslide deposits, where in 1986 velocities were an order of magnitude less. Surface and hydrological characteristics of the glacier in and down-glacier from the landslide deposit were also indicative of surge-like behavior in 1987, and a return to pre-surge conditions by 1988.

A Surge of Bualtar Glacier, Karakoram Range, Pakistan: A Possible Landslide Trigger

AbstractBualtar Glacier, Karakoram Range, northern Pakistan, surged during the spring and early summer of 1987. This followed a major episode of three landslides which impacted part of the glacier ablation zone on 30–31 July 1986. In May 1987, surface velocities of 7 m d−1were measured at one profile down-glacier from the landslide deposits, where in 1986 velocities were an order of magnitude less. Surface and hydrological characteristics of the glacier in and down-glacier from the landslide deposit were also indicative of surge-like behavior in 1987, and a return to pre-surge conditions by 1988.