Jökull - 01.12.1969, Síða 154

Fig. 6. Map showing locations of the recoráed
sightings and captures of polar bears in Ice-
land.
SEA ICE AND CLIMATE
Tliough the species of flora and fauna have
gradually increased in number since the last
Ice Age, various climate changes in Iceland as-
sociated with the fluctuations in the weather
of the Arctic regions have had their effect on
the distribution of the species. Once Iceland
was covered by widespread forest, but the
vegetation had become less by the 9th century,
when the country was first settled. The effects
of these fluctuations could probably be seen
in the annual rings of old trees or of fallen
trees that have been preserved in bogs, as well
as from the growth of lichens, which is very
slow. In the same way, changes in the distri-
bution of tundra areas are evidence of climatic
variations. In fact, all changes in vegetation
shecl some light on climatic fluctuations. Tliere
are various indications that the climate became
colder in the period between 1600 and 1890.
The decrease in annual temperature naturally
had an effect not only on the vegetation and
agriculture, but also on the wliole national
economy as can be seen from written records.
During this time there was a big increase in
the erosion of soil and destruction of the
vegtation cover, caused, most likely, by parti-
cularly cold, drv north or northeast winds ac-
companying a more frequent appearance of
sea ice. When the ice sheet approaches North
Iceland, or when ice drifts west or east along
the coast or even completely encircles the
150 JÖKULL 19. ÁR
country, one of the results must inevitably be
a decrease in the relatively milcl temperature
normally enjoyed by Iceland as a result of the
comparatively warm sea of the Gulfstream.
Should the ice become lancl-fast and com-
pletely cover the surface of the surrounding
sea, the country has then really become part
of the polar regions. In such cases it is reason-
able also to expect a prevailing north or
northeast wind, which will bring polar air to
Iceland that warms up very little on its way
entirely over ice. Such a weather situation,
which is associated with sea ice and usually
characteristic of late winter or spring, brings
a flow of cold and fairly dry polar air across
the country. This type of weather is thus in
more ways than one unfavourable for the
growth and maintenance of vegetation, and in
fact it actually helps to destroy vegetation. It
was the more frequent occurrence of such
weather conditions that was responsible for the
destruction by erosion of a large part of the
original vegetation in the latter part of the
Middle Ages. But climatic changes and the
arrival of sea ice also cause damage to vegeta-
tion before general clestruction sets in.
SEA ICE AND GRASS GROWTH
Grass is one of the most important factors
in Icelandic agriculture, and in anv discussion
of the effects of sea ice on this occupation it
is natural to investigate the influence ice has
on the growth of grass. Various written sources
on the subject are available, and it is of im-
portance in such a study to use the older ann-
als in comparing “ice years” with “grass years”.
These sources cover the whole period since
the original settlement of Iceland upto the
present day, though with certain gaps. We can,
in particular, first take the period upto 1780,
then continue with a study of the sea ice graph
by Thoroddsen (1916), comparing it with the
estimates of grass growth that extend fairly
regularly over the years 1780 to 1900. After
that we can refer to the Agricultural Statistics
and the sea ice details recordecl in recent years.
In addition, it is useful to compare tempera-
ture readings with the growth of grass in Ice-
land as reflected in the hay yield.
A perusal of the old records soon reveals