Abrupt Climate Change Revisited - Abrupt Climate Change: Mechanisms, Patterns, and Impacts - page 8

signal of old radiocarbon in the atmosphere during the de-
glaciation. This source is inferred to be a combination of
liquid and hydrate CO 2 in subduction zones and volcanic
centers other than on mid-ocean ridges. During glacial times,
CO 2 hydrates in the cold intermediate ocean are stable and
able to trap liquid CO 2 bubbling up from below the sea

quires vigorous testing through experiments, observations,
and modeling.
In a related study that takes into account the relationship
between the rise in atmospheric CO 2 and temperature in low
to high latitudes, Russell et al. [2009] reconstruct precipita-
tion and temperature histories from southeast African Lake
Tanganyika based on compound-speci

oor.
During deglaciation, a swath of these hydrates becomes
unstable and releases radiocarbon-dead CO 2 to the ocean-
atmosphere system, thus increasing atmospheric CO 2 and
decreasing

c hydrogen isotopes
and paleotemperature biomarker index TEX 86 in terrestrial
leaf waxes. It has been shown that Lake Tanganyika paleo-
temperature followed the temperature rise in Antarctica at
20 ka [Monnin et al., 2001] as well as the Northern Hemi-
sphere summer insolation at 30°N [Tierney et al., 2008].
Furthermore, temperatures in Lake Tanganyika began to
increase ~3000 years before the rise of atmospheric CO 2
concentrations during the last ice age termination (Figure 3).
This is a signi

14 C atm . This hypothesis is likely to stimulate
wide interest in the scientific community; however, it re-

Δ

cant discovery that needs to be replicated from
similar climate settings in other regions of the world. An
extensive statistical testing is also needed to con rm whether

the temperature record from Lake Tanganyika can be applied
more generally throughout the tropics or whether it represents
only a regional warming. If the reconstructed temperature
history from Lake Tanganyika survives the scrutiny of proxy
validation, it would strongly suggest that the primary driver
for glacial-interglacial termination, at least for the last ice age,
lies in the tropics rather than in high latitudes.

3.3. Holocene Climate

The conventional view based primarily on Greenland ice
core δ

18 O records suggests that climate in the Holocene
(current interglacial) was rather uniform and remarkably
stable in comparison to the preceding glacial and interstadial

Figure 3. Paleoclimatic proxy records of the last deglaciation.
(a) Biogenic opal flux in the Southern Ocean, interpreted as a proxy

for changes in upwelling south of the Antarctic Polar Front [Anderson
et al., 2009]. (b) Atmospheric CO 2 from Antarctic Dome C [Monnin
et al., 2001] placed on the Greenland Ice Sheet Project 2 (GISP2)
timescale. (c) Baja California intermediate water

14 C[Marchitto
et al., 2007]. (d) The 231 Th/ 230 Th ratios from the Bermuda Rise
(increasing values re

Δ

ect reduced Atlantic overturning circulation)
[McManus et al., 2004]. (e) The fish tooth/debris record

suggesting variations of water mass at Baja California [Basak et al.,
2010]. (f ) Ti/Ca ratios in bulk sediment from western equatorial
Atlantic, interpreted as a proxy for high Amazon River runoff
[Jaeschke et al., 2007]. (g) TEX 86 -derived surface temperature of
Lake Tanganyika [Tierney et al., 2008]. (h) The

e Nd of fossil

18 O in Shanbao
speleothems [Wang et al., 2008]. (i and j) GISP2 methane and
oxygen isotope ratios (

δ

18 O) [Stuiver and Grootes, 2000; Blunier
and Brook, 2001], respectively. All records are plotted according to
their independent age models.

δ