Short-term estimates of surface energy transfers and ablation on the lower Franz Josef Glacier, South Westland, New Zealand

Abstract

Estimates of the surface energy balance and ablation at a site on the lower Franz Josef Glacier were made from microclimatological measurements during five periods in 1981. The results indicate that surface melt occurs during all seasons, with the lowest mean melt .rates in winter and the highest in summer. However, short-term meteorological events can cause rapid melt at any time of the year. The melt rate observed during a warm, intense midwinter rainstorm was more than double the mean summer rate observed during a previous study. The contributions of net radiation ,;md the sensible and latent heat fluxes to ice melt are strongly controlled by the prevailing synoptic situation. During heavy rain, the mechanical and thermal action of running water can produce ablation in addition to that caused by surface melt. The long-term importance of this fluvial ablation to the glacier mass balance is unknown.