Jökull - 01.12.1972, Blaðsíða 60

on the infiltration and percolation of water in-
to glaciers and the movement of water inside
a glacier in the unsaturated and saturated zones.
Besides, it is essential to develop techniques
to obtain accurate measúrements of input of
meltwater and rain to the glacier and of the
changes of the liquid water storage underneath
the summer surface.
CONCLUSION
As concluded by Have?is, Miiller and Wil-
mot (1965) the use of logarithmic profiles for
wind speed, temperature and vapor pressure is
preferable to earlier methods used in computa-
tion of the turbulent heat fluxes which suffered
from the doubtful assumption that observed
ablation could be used for calculating the co-
efficients of diffusivity. On Bægisárjökull still
better results were obtained by using loga-
rithmic-plus-linear profiles rather than using
logarithmic. It appeared necessary to make al-
lowance for the suppressing of the turbulence
under the stable conditions present. The un-
defined experimental conditions on the mete-
orological site however devaluated the general
validity of this result.
Uncertainties in daily values for computed
energy balance components as well as measured
ablation restrict the value of the energy budget
computation to give only general trends and
relative importance of the processes for longer
periods. The same is valid in general, for the
computed meltwater.
The results from Bægisárjökull reveal a sea-
sonal trend to increased importance of the tur-
bulent energy fluxes throughout the summer.
The great importance of the general air circula-
tion was also illustrated. During the summer
of 1967 which had frequent cold northerly
winds, the turbulent processes were reduced
and tlie net radiation was responsible for the
greatest part of the relatively small ablation,
in spite of relatively high albedo comparecl
with the summer of 1968.
Bægisárjökull has a mere existence, protectecl
by the surrounding mountains (Björnsson 1971).
The proximity of the northern coast of Iceland
is also important for its life. Northerly winds
from the sea bring accumulation during the
58 JÖKULL 22. ÁR
winter and reduce ablation during the summer.
Further the glacier faces to north and obtains
during the summer only about 84 percent of
the insolation on a horizontal surface. Souther-
ly winds bring also a good deal winter ac-
cumulation but the highest rates of ablation
are accompanied with winds from these direct-
tions, mainly because the turbulent processes
are accentuated.
ACKNOWLEDGEMENTS
Instruments were ?nade available by the I?i-
stitute of Geophysics and Institute of Geo-
graphy both at Oslo University, Norwegia?i
Meteorological Institute, Oslo, Norwegia?i Polar
Institute, Oslo, a?id in Iceland by the National
Energy Autliority and Vedurstofan (Meteoro-
logical Service).
Financial support was given fro?n the Science
Foundation, Iceland.
Personal thanks are due to Olav Liestf>l, Sig-
urjón Rist, Sigurdur Thorarinsson and last but
not least to my companion on the glacier Jó-
hann Sigurjónsson.
REFEREN CES
Ahlrnann, H. W. and Thorarinsson, S. 1943:
Vatnajökull. Scientific results of the Swed-
ish-Icelandic Investigations 1936—37—38.
Reprints from Geografiska Annaler 1937—
1940, 1943. Stockholm.
Björnsson, Helgi. 1971: Bægisárjökull, North-
Iceland. Results of glaciological investiga-
tions 1967—1968. Part I. Mass balance and
general meteorology. Jökull 21: 1—23.
Calder, K. L. 1966: Concerning the similaritv
theory of Monin/Obukhov. Quart. J. Roy.
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Cramer, H. E. 1967: Turbulent Transfer Pro-
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Dyer, A. J. 1963: The adjustment of profiles
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