Rit (Vísindafélag Íslendinga) - 01.07.1931, Page 11

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Fig. 4. Temperature at the firnlimit in the period June—Sept.
perature means an excess of winter accumulation, a negative
one means little accumulation.
The height of the + 2° isotherm during the melting period
is by Ahlmann introduced in glaciology as the »normal
firnlimit«, that is to say, the hight of »the firnlimit at a place
where there prevails neither a great excess nor a great
deficiency of snow*.1)
In order <o get an idea of the distribution of the mean
temperature during the melting period at the firnlimit in lce-
land I have from maps I. and III. calculated that tempera-
ture and put down the result on map IV. in the form of
isotherms. The seperate values are partly to be found in
table I., seventh column. As to the length of the melting
period, a closer analysis of the temperature at the firnline
has mostly shown so great positive values in September,
that I have found myself justified in extending the melting
period to include that month also. In the second half of
1) H. W. Ahlmann: Glaciers in Jötunheim and their Physiography.
Geografiske Annaler 1922 H. 1. pag. 15.—16.
Jc