Rit (Vísindafélag Íslendinga) - 01.07.1931, Side 4

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hoarfrost in winter and the mean temperature during the
period of ablation in summer.
Much accumulation in winter therefore demands high
summer temperature at the firnlimit, while a low temperature
means scanty accumulation. The equilibrium, thus established,
will be disturbed by any excess of one or both elements,
which again will result in variations in the height of the
firnlimit.
The Height of the Firnlimit. It will generally be
attended with considerable difficulties to determine the real
position of the firnlimit or the snowline, as many factors,
especially the configuration of the mountains, lhe exposure to
the prevailing direction of wind, and the insolation exert a
great influence on the accumulation and melting of the snow.
In the following, I shall by the height of the firnlimit denote
the position of the boundaries between the névéregion and
the glacier-ice in the second half of the ablation period,
preferably about the middle of August, as measuremenfs at
a later date, will as a rule meet with difficulties.
In order to get a comprehensive representation of our
present knowledge of the height above sealevel of the firn-
limit in Iceland I have ventured to prepare the following
map. It shows the height of the firnlimit in different parfs
of the country based partly on data given by Th. Thoroddsen,
controlled by means of the existing topographical maps of
the South- and Westland, and partly determined as concerns
the north-eastern districts by the topmethod of Briickner. As
no satisfactory topographical maps as yet exist for that part
of the country, this method is of course difficult to apply
with any great degree of accuracy. I owe thanks to mag.
scient. Pálmi Hannesson for many good hints, concerning
the centralregion, and to cand. polyt. Helgi H. Eiríksson,
who has measured the height of the firnline at the south-
eastern margin of the Vatnajökull.
In Table I. I have have compiled the data, that the map
is based upon. The first two columns give the approximate
coordinates of the mountains and glacial regions, the third