Jökull - 01.12.1990, Blaðsíða 92

Figure 3. a) Radiocarbon dated <5lxO profile along a 4 m long sediment core from Lake Gerzensee in
Switzerland. b) <5180 profile along 150 m of the deep ice core from Dye 3 S-Greenland. c) The concentration
of continental dust changed in anti-phase with é!X0 in Pleistocene ice. d) Detailed <5180 record through the
Younger Dryas-Preboreal transition, during which the South Greenland temperature increased by 7°C in about
50 yr. e) Deuterium excess and f) dust concentration shifted to lower levels in less than 20 yr (from Dansgaard
et al., 1989). —a) C-14 aldursgreint <5lsO snið úr 4 m löngum setkjarna frá Gerzensee vatni í Sviss. b) álsO
snið úr hluta Dye 3 kjarnans á Suður Grœnlandi. c) Rykmagn breytist í öfugu hlutfalli við ó180 í Pleistocene
ís. d) Nákvœmt <5180 snið afYngra Dryas-Preboreal tímamótunum, en við þau jókst hitastig á Suður Grœnlandi
um7°C á u.þ.b. 50 árum. e) Tvívetnisauki ogf) rykmagn en styrkur hvoru tveggja minnkaði á um 20 árum.
<5180 profile taken from Lake Gerzensee, Switzerland
(Eicher, 1980; Eicher and Siegenthaler, 1976) and the
part of the Dye-3 profile, which represents the Glacial-
Holocene transition period (13.000-10.000 BP). The
first major warming as reflected in the sharp increase
in <5i80 is observed at about 13.000 BP in both pro-
files, corresponding to the warm periods of Bölling
and Alleröd (pollen zones Ib-II), then both profiles
show a sudden decrease in <5180 at about 11.000 BP,
reflecting the cold Younger Dryas period (pollen zone
III). The similarities of the two profiles are striking
88 JÖKULL, No. 40, 1990
and strongly suggest the same evolution of climatic
events in Greenland and Central Europe during the
Late Glacial period.
The reason for this similarity is believed to be
due to major shifts of the North Atlantic polar front
associated with similar changes in the North Atlantic
current (Ruddiman and Mclntyre, 1981). According
to Broecker and Denton (1989) the explanation for
the rapidity, near synchroneity and global extent of
climatic events must involve massive reorganizations
of the ocean-atmosphere system.