Fróðskaparrit - 01.01.1998, Blaðsíða 179

SEINHOLOSENA VEÐURLAGIÐ ELVDITIL JARÐFORMANDIVIRKSEMII FØROYUM [ g5
(West, 1985). Also the following winter
AD 1717-18 was very cold, and many of
the cattle died that winter. Lamb (1982)
concludes that the ocean surface tempera-
ture between Iceland and the Faroe Island
AD 1690-1699 was probably 5°C lower
than today (see also Ogilvie, 1992), and in
AD 1695 cod were sparse even as far south
as the Shetland Islands, suggesting a signif-
icant extension of polar water below 2°C
(Grove, 1988). In this period, the perigla-
cial environment in the Faroe Islands pro-
bably extended almost to sea level, and cer-
tain exposed localities may shortly have ap-
proached the climatic conditions for initia-
tion of either glaciation or permafrost
(Figs. 6 and 7).
Grass is the main crop grown in the
Faroe Islands. The yield of grass depends
very much on the air temperature during
both the growing season and the previous
winter (Grove, 1988). Cool summers re-
strict grass growth, but cold winters are
even more effective in restricting growth
(Bergthórsson, 1985). Hard frost in late
winter usually kills the grass, as does pro-
longed snow cover; especially if there is re-
peated melting and freezing. During the
late 20th century, cold winters are almost
invariably associated a high frequency of
strong, northerly winds with associated,
numerous snow showers. From this empir-
ical basis it may be suggested that also cold
intervals of the LIA such as AD 1872-1920
were characterised by a high frequency of
northerly winter winds, leading to signifi-
cant snow drifting from slopes with
northerly aspect, thereby exposing vegeta-
tion (grass) in these areas to the full effect
of low air temperatures. Most likely, exten-
sive areas with dominant grass vegetation
were killed at such events, especially on
slopes with northerly exposure, which sub-
sequently became exposed to soil erosion
by winds, drifting snow, rain, needle ice ac-
tion and solifluction (Humlum and Chris-
tiansen, in press). This scenario is support-
ed by the widespread occurrence of late
Holocene eolian deposits on slopes with
southerly exposure (Christiansen, 1998),
and the likewise universal evidence of de-
flation effects caused by northerly winds
(Humlum and Christiansen, in press). Also
historical reports on recurrent LIA snow
avalanches on slopes with southerly aspect
(Madsen, 1990) suggest a LIA winter wind
regime characterised by frequent northerly
winds. We have found no geomorphic evi-
dence suggesting that the grazing of sheep
is the prime cause for past and present soil
erosion in the Faroe Islands; this is basical-
ly a normal geomorphic phenomenon con-
trolled by the prevailing climate.
The Faroese landscape
and climatic change
The present very sensitive position of the
Faroese landscape within a climatological
context is highlighted by diagrams such as
Figs. 6 and 7. Due to their limited size, the
islands are not liable to produce any signif-
icant climatic feed-back effects, such as
caused by variations in mean snow cover.
They are located in the middle of the North
Atlantic drift, and therefore represent a
highly suitable location for registering re-
gional North Atlantic climatic variations.
Based on an inventory of spatial, temporal