383
/ItI1"Ho~""",~ -34
BOO
....,. 700
>
~ 600
~ 500
:x:
c..l 400
300
-32
-34
t -36 BYRD STATION Ice Core
~-36
'ill -40
-42
40
35
30
25
20
15
10
Age (kyrBP)
5
o
-36
-3Bt
-40~
'ill
-42
-44
a 01
E
.,
-g,
50 ii 01
DZ
100~
Figure 2: Climatic change over the last 40'000 years as obtained from the measurement of 8 18 0 on water (from Johnsen et al. (1992), Dansgaard et al. (1993)
and Hammer et al. (1994)) and CH4 on air of bubbles trapped in the ice core
(from Chappella.z et al. (1993) and Blunier et al. (1995). Four different features
of climate variability are evident in the different time series: (i) slow, astronomically forced transition from the glacial to the interglacial W 8 0 records and CH4)i
(ii) self-sustained oscillations during the glacial (foraminifera assemblages in a sea
sediment core (from Bond et al. (1993)) and ice cores before 20 kyr BP)i (iii)
non-deterministic (chaotic) variability during the Holocene (8 18 0 records) i and (iv)
abrupt reorganisations during the B{lJlling/ Aller{lJd/Younger Dryas Period (all but
Byrd Station core) [Figure compiled by T. BlunierJ
required to describe the system (Saltzman 1983; James and James 1992;
Mysak et al. 1993; Roebber 1995). Methane, on the other hand, exhibits