Jökull - 01.12.1961, Blaðsíða 4

Mynd 1. Kortið sýnir, hvar borað var í jökulinn í júní 1960, ennfremur sýnir það snælínu
haustsins 1960, kargann og staðsetningu snjómastra.
Map showing the boreholes Jnne 1960 and in autumn 1960: Firnline (snælína),
hillocky area (karginn) and the position of the snowstakes (snjómastur).
absoiute certainly as no accumulation stakes
were standing. A faint dust layer was found in
450—460 cm depth, probably autumn layer
1959. Approx. winter accumulation 455 cm,
average spec. gravily 0,54 and zuater content
2460 mm.
PERCOLATION OF MELT WATER. Six
days earlier, potassium permanganate dye had
been despersecl over a square of 25 by 25
meters, arouncl the place where the pit was sub-
sequently dug. The snow was xvet at the time
when the dye was dispersed. In the walls of
the pit the percolation channels were clearly
visible.
This test shows that when meltwater is per-
colating into the frozen snoxc the assumption
of a constant temperature at the same depth
level is not valid.
ABLATION 1960. In the Oct. 1960 expedi-
lion, the 1960 summer ablation at the snow
stake NE of Grimsvötn xuas found to be 625 mm
water equivalent. This indicates that the order
of magnitude of the meltwater collecting in the
Grimsvötn basin during the summer 1960 was
ab. 190 gigalitres (190x10e cubic metres), cor-
responding to a rise in water level of ab. 12 m.
This compares with the rise of 9 m ± 2 m in
the period June 14 to October 9, actually deter-
mined. More snoxu stakes are neecled in the
2