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- Title
Variability, correlation and forcing of Dansgaard-Oeschger cycles constrain underlying mechanism.
- Authors
Lohmann, Johannes; Ditlevsen, Peter
- Abstract
The strongest mode of centennial to millennial climate variability in the paleoclimatic recordare the Dansgaard-Oeschger events. Despite decades of research their dynamics and physicalmechanism remain poorly understood. Valuable insights can be obtained by studying high-resolution Greenland ice core proxies,such as the NGRIP δ18O record. However, conventional statistical analysis is complicated bythe high noise level, the cause of which is partly due to glaciological effects unrelated toclimate, and which is furthermore changing over time. We remove the high-frequency noiseand extract the most robust features of the DO cycles, such as rapid warming and interstadialcooling rates, by fitting a consistent piecewise-linear model to three Greenland ice corerecords. With statistical hypothesis tests we aim to obtain a mechanistic understandingof what controls the evolution of amplitudes and durations of the DO cycles. Tothis end, we investigate distributions, causalities in between different features, aswell as modulations of them in time by external climate factors, such as CO2 andinsolation. Our analysis suggests different mechanisms underlying warming and cooling transitionsdue to contrasting distributions and external influences of the stadial and interstadialdurations, as well as the fact that the interstadial durations can be predicted to some degree bythe linear interstadial cooling rates. From these empirical findings we propose a dynamicalmechanism for DO cycles.
- Subjects
GREENLAND; FORCE &; energy; GREENLAND ice; STATISTICAL hypothesis testing; ICE cores
- Publication
Geophysical Research Abstracts, 2019, Vol 21, p1
- ISSN
1029-7006
- Publication type
Article