Rit (Vísindafélag Íslendinga) - 01.06.1976, Page 13

SUMMARY
This work deals with investigations of the deuterium content of water, on
which the author has been working since 1962. It contains most of the results of
measurements which have been made up to the present day of deuterium in
precipitation, surface water, hot and cold groundwater, and Icelandic glacier ice.
Most of the measurements which have been made of the amount of the oxygen
isotope 018 in Icelandic water are also given.
The history of deuterium investigations in water, both in Iceland and in other
countries, is briefly reviewed. The method of measurement and the accuracy of
the measurements are described.
Although there are considerable variations with time in the deuterium content
of precipitation, such variations are negligible in springs and rivers, except glacial
rivers. Measurements of the deuterium content of single samples taken from a
cold or hot spring or a river, therefore give an excellent indication of the mean
deuterium content of the water system in question. Mean deuterium content of
local cold springs, rivers and streams is the same as the mean deuterium content
of precipitation at the corresponding place. The simplest method of obtaining
information on the mean deuterium content of precipitation at any particular
place is, therefore, to measure the water from the local source.
The deuterium content of the winter layer, collected on glaciers in the spring,
reflects in every way the deuterium content of the winter precipitation. In addi-
tion, the mean value of the winter layer is virtually identical to the mean value
of the annual precipitation at the corresponding place.
When rain and summer thaw on the surface of the glacier percolates through
the winter layer, there is a very close ice-water interaction which results in con-
siderable changes in the deuterium value of the winter layer. The variations which
are found in the winter layer are to a considerable extent eliminated. Moreover,
the firn which remains in the autumn has become much richer in deuterium than
the original winter layer.
By comparing the original deuterium content of the winter layer and the deu-
terium content of the layer which remains in the autumn, it is possible to deter-
mine how large a part of the annual precipitation is accumulated in the glacier
as ice, and how large a part runs away as meltwater the first summer. By
measuring the water-equivalent of the fim layer in the autumn, it is then possible
to calculate the total annual precipitation at the place in question.
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