Jökull - 01.12.1991, Page 18

Fig. 17 : 5-year overlapping means of annual temperature 1901-1990 at Reykjavík, Akureyri and Teigarhom.
Mynd 17: 5 ára raðmeðaltöl árshita 1901-1990 í Reykjavík, áAkureyri og Teigarhorni.
Fig.18 : 15-year overlapping means of annual temperature 1901-1990 at Reykjavík, Akureyri and Teigarhom.
Mynd 18: 15 ára raðmeðaltöl árshita 1901-1990 í Reykjavík, áAkureyri og Teigarhorni.
temperatures and consequently influencing the air
temperature. This indicates that the cause of an exten-
sive sea ice cover near Iceland is not exclusively an
unusually cold period in Iceland and surrounding
regions. Other important factors must be involved
such as mling wind directions. It is seen that the 5-
year curves are rising in the eighties. The reason for
this is that the unusually cold years 1979, 1981 and
1983 are respectively moving out of the 5-year means
and the rather warm year 1987 is at last included.
In Fig. 18 only the main picture of the present cen-
tury's temperature variations remains. The conclu-
sion drawn from the 15-year overlapping means is
that the annual temperature in Iceland has gradually,
but with some irregularities, been decreasing ever
since the end of the unusually warm period
1926-1946. At present the temperature conditions are
rather cool and unfavourable.
Fig.19 shows for Reykjavík and Akureyri the 10-
year overlapping means of temperature for the four
seasons as defined before (see Fig.3). It should be
bom in mind that the spring includes only 2 months
(April-May) but the autumn on the other hand 4
months (September-December). This may to some
degree influence average values, i.e how changeable
they are from year to year. Anyway it is obvious
from the curves that the amplitudes of the tempera-
ture variations are smallest in summer.
The sudden increase of temperature just after 1920
is similar for all seasons with the exception that it
starts a little later in spring and summer than autumn
and winter. During the first two decades the winters
must be said to have been extremely cold at
Akureyri, i.e. in northern Iceland, but less at Reykja-
vík where the winter temperature after 1974 app-
roaches to be equally low.
16 JÖKULL, No. 41, 1991