Jökull - 01.12.1999, Blaðsíða 4

the North Atlantic Ocean and the Nordic Seas (Kog
Karpuz and Jansen, 1992; Lehman and Keigwin,
1992; Haflidason et ai, 1995; Rasmussen et al.,
1996), which shows that the dramatic changes in
North Atlantic ocean circulation during the last
deglaciation was coupled with corresponding atmo-
spheric changes. A similar pattem of climatic oscilla-
tions is also recorded in land areas adjacent to the
North Atlantic (NASP Members: Executive Group,
1994), which suggests that variations in surface ocean
temperatures have been a major factor governing ter-
restrial climates in this region. A regional warming is
recorded around 13,000 BP, and relatively warm con-
ditions prevailed up to c. 11,000 BP. This so-called
Late-glacial Interstadial or Bplling/Allerpd warm pe-
riod was, however, punctuated by a series of short-
lived cooling events, e.g. the Aegelsee Oscillation at
or shortly béfore 12,000 BP (Lotter et ai, 1992) and
the Gerzensee/Killarney Oscillation close to 11,000
BP (Siegenthaler et al., 1984; Levesque et al., 1993).
The rapid transition to the Younger Dryas cold event
at c. 11,000 BP was associated with a fall in July tem-
peratures of the order of 4-8°C in northwestern Eu-
rope (Berglund et al., 1994; Birks et al., 1994; Walker
et al., 1994), and there are indications of even colder
and drier climatic conditions towards the end of the
Younger Dryas cold event in some European areas
(De Beaulieu et al., 1994; Walker et al., 1994). The
transition to the Holocene at c. 10,000 BP is recorded
as an abrupt and significant warming throughout the
North Atlantic region. A 6-8°C increase in July tem-
peratures is, for example, recorded in parts of north-
westem Europe (Atkinson et al., 1987; Birks et al,
1994; Walker et ai, 1994). Several records from areas
adjacent to the North Atlantic indicate climatic insta-
bility during the Preboreal Chronozone (Amman et
al., 1994; Anderson and Macpherson, 1994; Birks et
al., 1994; Ingólfsson and Norddahl, 1994; Walker et
al., 1994), and recently Björck et al. (1996) identified
a short-lived cooling event in terrestrial records
around the North Atlantic, including the ice-core
record, within the interval 9900-9500 BP and named
it the Preboreal oscillation (PBO). A correlative event
has been identified in cores from the Norwegian Sea
(Kog Karpuz and Jansen, 1992; Lehman and Keig-
win, 1992 ; Haflidason et al., 1995).
Owing to Iceland’s position in the middle of the
North Atlantic Ocean, lying within the track of marine
polar front migrations during the last deglaciation, Ice-
landic terrestrial archives covering this period could
be expected to reveal clear climatic signals. Recon-
structions of the environmental development in Ice-
land during the Late Weichselian and Early Holocene
has, however, hitherto been hampered by the scarcity
Fig. 1. Deglacial migrations of the North Atlantic polar front according to (A) Ruddiman and Mclntyre (1981) and (B) K05 et
al. (1993). Ages in IJC years BP. - Fœrsla skila á milli kaldra og heitari yfirborðssjávarstrauma í Norður Atlantshafi á
síðjökultíma samkvœmt úttekt (A) Ruddiman og Mclntyre (1981) og (B) Koq o. fl. (1993). Aldur er sýndur í14C árum BP.
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JÖKULL, No. 47, 1999