PIK Biennial Report 2000-2001 - Potsdam Institute for Climate ...

TOPIK 1 - Nonlinear Dynamics of the Ecosphere
The ecosphere is a complex dynamic system which
encompasses the abiotic geosphere (mainly atmosphere,
oceans, ice masses, the Earth interior) and the living
world as composed of the terrestrial and marine biosphere;
humankind is considered here as an external
driver. This TOPIK explores the nonlinear behaviour of
the ecosphere as well as its resilience to large-scale natural
and anthropogenic perturbations. Examples of the
QUEST
Quaternary Earth System Stability
Project speaker: Martin Claussen
PIK project members: Eva Bauer, Victor Brovkin,
Reinhard Calov, Siegfried Franck, Andrey Ganopolski,
Alexa Griesel, Matthias Hofmann, Anja Hünerbein,
Claudia Kubatzki, Till Kuhlbrodt, Miguel Maqueda,
Marisa Montoya, Vladimir Petoukhov,
Stefan Rahmstorf, Yuri Szirezhev.
External project collaborators: Danish Centre for Earth
System Science (Denmark), Dept. of Quaternary Geol./
Palaeoecology, Vrije Univ. Amsterdam (The
Netherlands), Inst. d’Astronomie et de Géophy. Georges
Lemaître: Univ. Catholique Louvain (Belgium), Inst. u.
Museum f. Geol. u. Palöoontologie, Univ. Tübingen
(Germany), Laboratoire des Sciences du Climat et
d’ Environnement (France), Royal Netherlands
Meteorological Institute (The Netherlands), KIHZ
(Klima in histor. Zeiten) project partner (Germany).
Research Questions
Human interventions play a significant role in the Earth
system. We are altering the character of the Earth at an
increasing rate, and the present dynamic stability of the
Earth system itself may be endangered. Therefore the
QUEST project is designed to improve our understanding
of the dynamics of the natural Earth system in its
present geological epoch, the late Quaternary (the last
several hundred thousand years). QUEST addresses the
following questions:
(a) Can we identify the processes and feedbacks that
have kept the natural Earth system within stable bounds
during the last 400,000 years?
(b) Can we explain the abrupt climate changes found in
records of the last glacial?
latter are the continuing release of fossil fuel combustion
products into the atmosphere, sub-continental changes
in land cover, and variations in solar luminosity. Investigations
include exploration of so-called switches and
choke points in the ecosphere, i.e. regions in which slight
external forcings/disturbances can trigger massive
changes of climate and other vital Earth system elements.
(c) How resilient is the natural Earth system in its
present state to large-scale natural and anthropogenic
perturbations?
excited state
(interstadial)
basic state
(stadial)
Fig. 1: Schematic of the two glacial climate states described in
Ganopolski and Rahmstorf (Nature, 2001). Bottom: the stable
“cold” or “stadial” mode. Top: the unstable “warm” or “interstadial”
mode. Contours show the surface air temperature difference
relative to the stable state. Ocean circulation is shown schematically,
surface currents in red and deep currents in light blue. Continental
ice sheets are based on the reconstruction of Peltier,
prescribed in the simulations.
First Results
DANSGAARD OESCHGER CYCLES
Abrupt changes in climate, termed Dansgaard-Oeschger
(D/O) and Heinrich (H) events, have punctuated the last
glacial period (~100,000 - 10,000 years ago) but not the
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