Abstract
Ablation on the Greenland ice Sheet can be calculated either from the degree-day factor or by an energy balance model. Both approaches involve problems. i.e. the degree-day factor varies with time and space while the energy balance model requires data which are often not available. The solution is to understand, and possibly predict variations in degree-day factor. This can be attempted by (1) sensitivity experiments with the energy balance model, and (2) field samples of ablation under widely varying climatic conditions.
Highlights
Abl
Longwave radiation balance Sensible heat flux Latent heat flux ablation mainly refers to ice and the error is reasonably small
There is an important interaction between temperature and wind speed (Braithwaite & Olesen, 199Gb) which is overlooked if variations in wind speed are Within limits it should be possibie to explain variations in the degree-day factor in terms of energy balance (Ambach, 1988; BraithW5lite & Olesen, 199Gb) so that likely variations can be estimated, and possibly associated with some scheme of dimatic classification. In both the present cases (Fig. 4), radiation is on average the largest source of ablation energy, but the turbulent fluxes are more variable
Summary
The ratio of the Iwo quanLities is the degree-day factor wbich is assllmed Io be constant so that melting in any period ean be caIculated from the degrce Jay sum in tlle same period. The mean degree-day factors for different months at each site (Table 1) are not significantly different (5 percent level) from each other according to the paired t-test and one-way analysis of variance The means of the full samples for each site (14 and 21 months) are, significantly different (5 per cent level) according to the 2-sample t-test There is little correlation between degree-day factors at the two sites so their variations can be regarded as more or less random
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