24 Feb 2023
 | 24 Feb 2023
Status: a revised version of this preprint is currently under review for the journal CP.

Disparate energy sources for slow and fast Dansgaard-Oeschger cycles

Diederik Liebrand, Anouk T. M. de Bakker, Heather J. H. Johnstone, and Charlotte S. Miller

Abstract. During the Late Pleistocene, Dansgaard-Oeschger (DO) cycles triggered warming events that were as abrupt as the present-day human-induced warming. However, in absence of a periodic forcing operating on millennial time scales, the main energy sources of DO cycles remain debated. Here, we identify the energy sources of DO cycles by applying a bispectral analysis to the North Greenland ice core project (NGRIP) oxygen isotope (δ18Oice) record—a 123-thousand-years (kyr) long proxy-record of air-temperatures (Tair) over Greenland. For both modes of DO cyclicity—slow and fast—we detect disparate energy sources. Slow-DO cycles are marked by multi-millennial periodicities in the 12.5 to 2.5 kyr bandwidth and receive energy from astronomical periodicities. Fast-DO cycles have millennial periodicities in the 1.5 ± 0.5 kyr range and receive energy from centennial periodicities. We propose cryospheric and oceanic mechanisms that facilitate the transfer of energy from known sources to slow- and fast-DO cycles, respectively. Our findings stress the importance of understanding energy-transfer mechanisms across a broad range of time scales to explain the origins of climate cycles without primary periodic energy-sources.

Diederik Liebrand et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2023-6', David De Vleeschouwer, 12 Mar 2023
    • AC1: 'Reply on RC1', Diederik Liebrand, 02 May 2023
  • RC2: 'Comment on cp-2023-6', Anonymous Referee #2, 11 Apr 2023
    • AC2: 'Reply on RC2', Diederik Liebrand, 02 May 2023

Diederik Liebrand et al.

Diederik Liebrand et al.


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Short summary
Climate cycles with millennial periodicities are hard to explain, because no Earth-external climate forcing exist that operates on millennial time scales. We show using a statistical analysis of a famous Greenlandic air-temperature record that two disparate energy sources (one astronomical and one centennial) fuel millennial climate variability. We speculate that two distinct climatic/cryospheric (i.e., ice sheet) processes are responsible for the transfer of energy to millennial climate cycles.