Fróðskaparrit - 01.01.2002, Page 109

ARKTISKA FJALLAVEÐRIÐ í 2000 Á SORNFELLI
107
The lower limit of the ET climate type is
located where the mean air temperature of
the warmest month is 10°C, corresponding
to the tree limit. Using the Sornfelli mean
August air temperature of 6.5 °C and the lo-
cal August lapse rate of -0.0068°C/m, the
limit between the polar and temperate cli-
mate is located at 216 m asl. in the Sornfel-
li region in the year 2000. Thus the data
from the Sornfelli meteorological station
emphasize that about 68% (Fig. 1) of the
land area of the islands had a polar climate
in 2000. The lower limit of the periglacial
zone, based on the distribution of peri-
glacial landforms in the Faroe Islands, have
previously been located at 250-450 m asl.
(Humlum and Christiansen, 1998a;b) (see
Fig. 1), which corresponds very well with
the suggested 200 m asl. lower limit of the
low arctic. Biogeographically, Tuhkanen
(1987) located the Faroe Islands in the
hemiboreal zone at sea level, but with a
hemioroarctic zone in areas above 700 m.
He stressed that even lower oroarctic zones
may well be found at levels below 700 m
asl. His vertical zonation is based on mete-
orological data from the 1931-1960 period,
which was slightly warmer than the 1961-
1990 period, and on a too low standard
Fennoscandinavian lapse rate of only
-0.0053°C/m, as he did not have access to
any local lapse rates. Therefore his arctic
zone probably would also be significantly
lowered using the Sornfelli meteorological
data. The potential tree line has been locat-
ed at 150 m asl. (Ødum, 1991) and later at
300 m asl. (Feivsson, 1993) for sheltered
locations. These values also largely agree
with the lower boundary of the low arctic
zone located around 200 m asl.
Traditionally the polar climate of the
northern Hemisphere is also known as the
arctic climate. In the southern parts a low
arctic climate exist, in which the mean air
temperature of the warmest month is below
10°C, but above 5°C. At the highest moun-
Figure II. Cumulative
indices offreezing
(FDD), thawing (TDD)
anci growing (CDD)
degree daysfor the year
2000 at Sornfelli,
calculatedfrom the
corrected air
temperature data.
L