IngentaConnect The origin of channels on lower Taylor Glacier, McMurdo Dry Valle...

Authors: Johnston, Robin R.; Fountain, Andrew G.; Nylen, Thomas H.

Source: Annals of Glaciology, Volume 40, Number 1, January 2005 , pp. 1-7(7)

Publisher: International Glaciological Society

Abstract:

Well-developed surface channels on Taylor Glacier, McMurdo Dry Valleys, Antarctica, begin as medial moraines incised as shallow, narrow surface depressions, and retain this geometry for tens of km. Over a distance of 1100 m, the channel geometry dramatically changes, reaching depths >20 m and widths >100 m. After rapidly enlarging, the channels appear to evolve toward a new equilibrium geometry. Compared to the glacier surface, the air temperature in the channels is warmer by ∼1.7°C, wind speed is reduced by ∼2.4 m s⁻¹ and net shortwave radiation is greater by ∼14 W m⁻². The microclimate in the channel shifts the energy balance towards enhanced melt. Field evidence and energy-balance modeling indicate ablation in the deep channels is ∼4.5 times greater than the local horizontal glacier surface and that melt accounts for 99% of the summer ablation, compared to 75% on the adjacent horizontal glacier surface. Melt in these channels supplies 65% of the unaccounted water discharge into the neighboring lake. In large part, the channels generate the water they carry, rather than merely route water generated elsewhere.

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The origin of channels on lower Taylor Glacier, McMurdo Dry Valleys, Antarctica, and their implication for water runoff