Untersuchungen zum Energieumsats in der Akkumulationszone des grönländischen Inlandeises.

Resumé

1. Flux of sensible and latent heat
Estimations of the convective heat fluxes and results of measurements in the snow cover of Carrefour station (1850 m a.s.l.) situated in the accumulation area of the Greenland Ice Cap are described for the period between the middle of May and end of July 1967.
Wind velocities measured up to a height of 250 cm on average satisfy very well the logarithmic wind profile. The following mean values were obtained: friction velocity 27 ,6 cm/sec and roughness parameter 0,012 cm. The gradients of air temperature and vapor pressure are taken from records of air temperature and water vapor pressure with allowance for systematic errors. Because of considerable difficulties of measuring the sensible and latent heat fluxes above a non-melting snow surface, these heat fluxes were estimated by three different techniques (gradient measurements, heat balance equation, saturation vapor pressure of the surface). The results within the error limit show satisfactory agreement. Owing to the prevailing influence of evaporation in the latent heat
flux, latent heat flux and sensible heat flux almost compensate (sum: + 5,5 cal/cm ² d; sensible heat flux: + 31,2 cal/cm ² d; latent heat flux: - 25,7 cal/cm ² d).

2. Measurements in the snow cover
Measurements of temperature fluctuations in the snow cover showed the daily amount of energy required for raising the snow temperature tobe small: 10 cal/cm ² d. Surface melting takes place over a period of only a few days, with the free water content of the layer beneath the surface increasing up to 7% by volume. Running-off melt water may be definitely excluded. The water equivalents of the annual net accumulation between 1967 and 1948 were determined from two cores by analyzing the δ( ¹⁸O) values, the tritium content, and the gross beta activity. The mean of the annual net accumulation in this period varies between 40 and 90 g/cm ² (mean value: 57 g/cm ²a). Despite the high values of incoming shortwave radiation of more than 800 cal/cm ² d, radiation fluxes and convective processes change the energy state (temperature and free water content) of the snow cover over a summer period only very little.