Abrupt climate changes and the astronomical theory: are they related?
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Published:2022-02-11
Issue:2
Volume:18
Page:249-271
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ISSN:1814-9332
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Container-title:Climate of the Past
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language:en
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Short-container-title:Clim. Past
Author:
Rousseau Denis-Didier, Bagniewski Witold, Ghil MichaelORCID
Abstract
Abstract. Abrupt climate changes are defined as sudden climate changes that took place over tens to hundreds of years or recurred at millennial timescales; they are
thought to involve processes that are internal to the climate system. By
contrast, astronomically forced climate changes involve processes that are
external to the climate system and whose multi-millennial quasi-periodic
variations are well known from astronomical theory. In this paper, we
re-examine the main climate variations determined from the U1308 North
Atlantic marine record, which yields a detailed calving history of the
Northern Hemisphere ice sheets over the past 3.2 Myr. The magnitude and
periodicity of the ice-rafted debris (IRD) events observed in the U1308
record allow one to determine the timing of several abrupt climate changes,
the larger ones corresponding to the massive iceberg discharges labeled
Heinrich events (HEs). In parallel, abrupt warmings, called
Dansgaard–Oeschger (DO) events, have been identified in the Greenland
records of the last glaciation cycle. Combining the HE and DO observations,
we study a complex mechanism giving rise to the observed millennial-scale
variability that subsumes the abrupt climate changes of last 0.9 Myr. This
process is characterized by the presence of Bond cycles, which group DO
events and the associated Greenland stadials into a trend of increased
cooling, with IRD events embedded into every stadial, the latest of these
being an HE. These Bond cycles may have occurred during the last 0.9 Ma when Northern Hemisphere ice sheets reached their maximum extent and volume, thus
becoming a major player in this time interval's climate dynamics. Since the
waxing and waning of ice sheets during the Quaternary period are orbitally
paced, we conclude that the abrupt climate changes observed during the Middle Pleistocene
and Upper Pleistocene are therewith indirectly linked to the astronomical
theory of climate.
Funder
Horizon 2020 Framework Programme
Publisher
Copernicus GmbH
Subject
Paleontology,Stratigraphy,Global and Planetary Change
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