Even now, the measurement of energy balance on a glacier is far from a routine exercise and is only done for selected ‘experiments’ on a few glaciers (Oerlemans and Vugts, 1993 Reference Konzelmann and BraithwaiteOhmura and others, 1994), although most people acknowledge that the energy balance is fundamental to understanding links between glaciers and climate. The study of glacier energy balance has made much progress since the 1930s (Ångstrom, 1933), but the use of simple climate data to calculate the energy balance, first identified by Sverdrup (1935), is still not entirely solved because of the theoretical and instrumental difficulties. Important sinks include heat conduction into the glacier and, most importantly for present purposes, the latent heat needed for melting. Important sources of energy include solar and terrestrial radiation and turbulent heat exchange with the overlying atmosphere. This involves measuring or estimating the different energy sources and sinks. One way of studying glacier variations with climate is to evaluate the energy balance at the glacier surface during the melt season.
The present study is based on manually observed ablation and climate data, but the approach could be updated to use data from automatic recording stations using modern sensors. Heat-transfer coefficients are also estimated on a monthly basis for the two long records, and substantial variations are found, suggesting that the method should not be used for <20–30 days of data. Average transfer coefficients for four out of the six sites are close to 0.003, which is in reasonable agreement with values reported elsewhere, while larger values of 0.0047 and 0.0057 are found at the other two sites. Data are available for short periods from two sites in Arctic Canada and two sites in North Greenland, and for hundreds of days of record at Nordbogletscher and Qamanârssûp sermia in South and West Greenland, respectively. Values of the heat-transfer coefficient are evaluated for six sites by correlating measured melt energy with a wind–temperature variable (product of daily mean wind speed, temperature and mean atmospheric pressure for the altitude in question). Sensible-heat flux can be estimated from wind-speed and temperature data using a dimensionless heat-transfer coefficient. Sensible-heat flux is obviously important for glacier ablation but is difficult to measure routinely.
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