Fróðskaparrit - 01.01.1998, Blaðsíða 301

UMHVØRVISBROYTING í TÍ ÍSFRÍA GRØNLANDI: EITT YVIRLIT
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southwest Greenland had been deglaciated,
whereas in North and East Greenland larg-
er ice-free areas were present. A pioneer
vegetation with bryophytes and herbs, but
without woody plants, began to cover the
land (Bennike et al., in press). Some hardy
species may already have immigrated to
Greenland towards the end of the last
glacial stage, although no floras or faunas
have so far been conclusively assigned to
this time interval. The first millennia of the
Holocene saw rapid deglaciation due to
warm climates; and rapid emergence due to
crustal rebound. By 10 cal. ka BP the
deglaciated fringe of land in S W Greenland
had grown, and the first dwarf shrubs, such
as Empetrum nigrum had immigrated to
Greenland. In the littoral zone in the West
Greenland waters Mytilus edulis was ex-
tending its range. At around 8 cal. ka BP
Betula nana arrived in East Greenland
where it expanded rapidly (Funder, 1978).
Some plants and animals extended their ge-
ographical ranges further north than at pre-
sent. The young, »raw« lakes were rich in
ions and nutrients and housed a rich flora of
macrolimnophytes ((Fredskild, 1992). A
similar situation is seen in basins that be-
came isolated from the sea following emer-
gence of the land (Bennike, 1995).
By about 7 cal ka BP the ice sheet mar-
gin was situated near its present position.
The dwarf shrubs Salix arctica and Cas-
siope tetragona colonised East Greenland
from the north (Funder, 1978). The Inland
Ice reached it's minimum size at 5.5 cal. ka
BP, and in some areas the ice margin may
have been situated as much as 50 km be-
hind its present location (Weidick et al,
lce Climate Vegetation
Little lce Age Deterioration
Holocene Onset of Neoglaciation Minimum Dedining summer temperatures Optimal heaths
Rapid recession Highest Holocene temperatures Pioneer veqetation
Maximum Temperature minimum
Pleistocene Minimum Warm summers Scrubs and heaths in East Greenland
Local gladers? Very warm summers Forest-tundra in North Greenland
Fig. 2. Diagram showing a brief summary of environ-
mental changes in the ice-free parts of Greenland.
Mynd 2. Strikumynd, sum vísir eitt stutt yvirlit yvir
umhvørvisbroytingar í tí ísfría partinum av Grønlandi.
1990). Most local ice caps and ice shelves
had probably completely disappeared in the
Mid Holocene.
After 5.5 cal. ka BP declining pollen de-
position rates are registered in East Green-
land, and Mytilus edulis disappeared (Fun-
der, 1978), but around 4 ka BP some beetle
species still occurred further north than to-
day in West Greenland (Bocher and Fred-
skild, 1993). Oligotrophication of lakes led
to local extinctions of water plants. Alnus
crispa and Betula pubescens arrived in
West Greenland by 4.2 cal. ka BP (Fred-
skild, 1985).