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Precise interpolar phasing of abrupt climate change during the last ice age

Nature

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https://doi.org/10.1038/nature14401

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Abstract

The last glacial period exhibited abrupt Dansgaard–Oeschger climatic oscillations, evidence of which is preserved in a variety of Northern Hemisphere palaeoclimate archives1. Ice cores show that Antarctica cooled during the warm phases of the Greenland Dansgaard–Oeschger cycle and vice versa23, suggesting an interhemispheric redistribution of heat through a mechanism called the bipolar seesaw456. Variations in the Atlantic meridional overturning circulation (AMOC) strength are thought to have been important, but much uncertainty remains regarding the dynamics and trigger of these abrupt events789. Key information is contained in the relative phasing of hemispheric climate variations, yet the large, poorly constrained difference between gas age and ice age and the relatively low resolution of methane records from Antarctic ice cores have so far precluded methane-based synchronization at the required sub-centennial precision23,10. Here we use a recently drilled high-accumulation Antarctic ice core to show that, on average, abrupt Greenland warming leads the corresponding Antarctic cooling onset by 218 ± 92 years (2σ) for Dansgaard–Oeschger events, including the Bølling event; Greenland cooling leads the corresponding onset of Antarctic warming by 208 ± 96 years. Our results demonstrate a north-to-south directionality of the abrupt climatic signal, which is propagated to the Southern Hemisphere high latitudes by oceanic rather than atmospheric processes. The similar interpolar phasing of warming and cooling transitions suggests that the transfer time of the climatic signal is independent of the AMOC background state. Our findings confirm a central role for ocean circulation in the bipolar seesaw and provide clear criteria for assessing hypotheses and model simulations of Dansgaard–Oeschger dynamics.

Additional publication details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Precise interpolar phasing of abrupt climate change during the last ice age
Series title:
Nature
DOI:
10.1038/nature14401
Volume:
520
Year Published:
2015
Language:
English
Publisher:
Nature Publishing Group
Contributing office(s):
Geosciences and Environmental Change Science Center
Description:
5 p.
First page:
661
Last page:
665
Online Only (Y/N):
N
Additional Online Files (Y/N):
N