Jökull - 01.12.1999, Side 17

described as a shrub and dwarf-shrub tundra. The
abrupt vegetational change recorded in Lake Torfa-
dalsvatn at 8000 BP was suggested by Rundgren
(1998) to have been climatically forced, possibly by
an increase in winter precipitation.
DISCUSSION
It was suggested by Rundgren (1995) that local
glaciers may have exerted a cooling influence on the
climate on northernmost Skagi during the earliest
recorded episode (11,300-10,900 BP). However, the
terrestrial pollen spectra and the limnic data for this
period may altematively reflect cold conditions asso-
ciated with the Gerzensee/Killarney Oscillation, a re-
gional cooling event at that time earlier reported from
areas adjacent to the North Atlantic (Siegenthaler et
al, 1984; Levesque et al, 1993; NASP Members: Ex-
ecutive Group, 1994). A correlative event is also rec-
ognized in the Greenland ice cores (e.g. Johnsen et al.,
1992) and in cores from the Norwegian Sea (Lehman
and Keigwin, 1992; K05 Karpuz and Jansen, 1992;
Haflidason et al., 1995). If this altemative interpreta-
tion is correct, it is possible that core penetration in
Lake Torfadalsvatn, which is the basin with the oldest
recorded sediments, was limited by the presence of
coarse sediments deposited in connection with basin
isolation and not by till or bedrock. This implies that
lake sediments older than 11,300 BP could be present
on northemmost Skagi, and that this area may have
been deglaciated well before 11,300 BP.
As shown by Ingólfsson et al. (1997), the climatic
development reconstmcted from Skagi lake sediments
fíts well with palaeoclimatic data from other parts of
Iceland. Although Late Weichselian and early
Holocene palaeoclimatic information from Iceland is
limited, there is a good correspondence between the
reconstruction presented for northernmost Skagi and
the available proxy data from subfossil mollusc and
foraminifera faunas and ice-marginal positions
(Bárðarson, 1923; Andrésdóttir, 1987; Ingólfsson,
1987, 1988, 1991; Hjartarson and Ingólfsson, 1988;
Eiríksson et al., 1991; Norðdahl, 1990, 1991; Svein-
björnsdóttir and Johnsen, 1991; Norðdahl and
Hafliðason, 1992; Norðdahl and Hjort, 1993; Ingólfs-
son and Norddahl, 1994; Sæmundsson, 1995; Ás-
björnsdóttir and Norðdahl, 1995; Norðdahl and Ás-
bjömsdóttir, 1995). Moreover, the Skagi palaeoclimatic
reconstruction is in accordance with terrestrial (NASP
Members: Executive group, 1994), marine (Ruddiman
and Mclntyre, 1981; K05 Karpuz and Jansen, 1992;
Lehman and Keigwin, 1992; K05 etal., 1993; Haflida-
son et al., 1995) and ice-core records (Dansgaard et
al., 1989, 1993; Alley et al., 1993; Johnsen et al.,
1995) from the North Atlantic region, indicating a
close connection between deglacial ocean circulation
changes, i.e. the migrations of the marine polar front,
and climatic conditions on Iceland (Ingólfsson et al.,
1997).
Besides confirming the prevalent conception of
Late Weichselian and early Holocene climate change
in the North Atlantic region, the palaeoclimatic recon-
stmction from northemmost Skagi provides some new
details on this development: (1) The Gerzensee/Killar-
ney Oscillation may be registered on northernmost
Skagi, which implies that the marine polar front was
located south of Iceland in the period 11,300-10,900
BP, (2) the polar front migrated to a position north of
Iceland at 10,900 BP, where it remained until c. 10,600
BP, when a rapid southward displacement of the polar
front placed Iceland within polar waters and initiated
the Younger Dryas cold event in Iceland, (3) the Pre-
boreal oscillation (c. 9800-9700 BP) was most likely
associated with a southward migration of the marine
polar front, but its position was probably still north of,
but very close to, Iceland during that event.
Rundgren et al. (1997) showed that the raised
beach ridge (A) marking the marine limit on northern-
most Skagi at c. 65 m a.s.l. (Fig 2) is older than
11,300 BP (Fig. 6), and they proposed that it dates
from a >12,000 BP event of high relative sea levels
known from other parts of Iceland (Ashwell, 1967;
Ingólfsson, 1988; Ingólfsson and Norddahl, 1994).
Moreover, they showed that regression below present
sea level occurred at 9000 BP on northernmost Skagi
(Fig. 6), which is in line with observations in other
parts of Iceland (Thorarinsson, 1956; Kjartansson et
al, 1964; Thors and Helgadóttir, 1991; Ingólfsson et
al„ 1995). The recording of marine transgressions on
northernmost Skagi during the Younger Dryas cold
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