Jökull - 01.12.1969, Page 13

'46 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 '68
Fig. 2. Season temperature in Stykkishólmur West-Iceland 1846—1968. Winter (Dec.—March).
Spring (April—May.). Summer (June—Sept.). Autumn (Oct.—Nov.). The stippled line indicates
the temperature of the coldest inonth of each winter.
In the first seven years of the series (1846—
1852) there are three warm or very warm
winters, but in the winter of 1853 there is a
sudden change, and cold or very cold winters
clominate the next 40 years up to 1892. From
1892 to 1920 the winters are still cold, but in
this period there are only three very cold wint-
ers 1902, 1907 and 1918.
It may be of interest to look at the number
of months in which ice has been reported in
the coastal waters of Iceland in the 4 periods
of different winter temperature. This number
of months with ice is however not a very exact
estimate for the extension of sea ice, but it is
the only estimate available for the whole
period. During the first seven years with mean
winter temperature — 0.7° C, alrnost no ice is
observed. In the. hardest period, 1853 to 1892,
with mean temperature —2.3° C the average
number of icemonths is approx. 2.5 in a year,
in the somewhat milder periocl 1893—1920 with
mean temperature — 1.7° C the average ice
period was near 1 montli. From 1921 — 1964 the
ice period was usually less than 1 month, ancl
in 12 winters no ice was reported. In 1965
and 1968 ice was observed in 5—6 months.
In these 123 years the number of icemonths
has been 3 or more in 25 years. It is evident
that sorne relation between the number of ice-
months ancl the winter temperature exists. Al-
most 4/5 of all great iceyears (Here used for
years with 3 or more icemonths) are found
JÖKULL 19. ÁR 9