Preprints
https://doi.org/10.31223/X54S90
https://doi.org/10.31223/X54S90
27 Jun 2023
 | 27 Jun 2023

Statistical precursor signals for Dansgaard-Oeschger cooling transitions

Takahito Mitsui and Niklas Boers

Abstract. Given the likely bistability of the Atlantic Meridional Overturning Circulation (AMOC) and its recently inferred weakening, it is important to investigate the capability of identifying robust precursor signals for a possible future AMOC collapse as well as its collapses in the past. Dansgaard-Oeschger (DO) events, manifested most clearly as abrupt Northern-Atlantic temperature jumps during glacial conditions, likely reflect past switches between strong and weak AMOC modes. In general, the variance and the autocorrelation with a small lag increase in a system approaching a co-dimension one bifurcation point. Some previous studies find such statistical precursor signals for the DO warming transitions associated with a strengthening AMOC. On the other hand, statistical precursor signals for the abrupt DO cooling transitions, presumably associated with AMOC transitions from the strong to the weak mode, have not been identified. Here we identify robust and statistically significant precursor signals for several DO cooling transitions in Greenland ice core records. The important source of the statistical precursor signals stems from so-called rebound event, humps in the temperature observed at the end of interstadial, some decades to centuries prior to the transition. We propose several dynamical mechanisms that give rise to such rebound events and statistical precursor signals.

Takahito Mitsui and Niklas Boers

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1267', Anonymous Referee #1, 21 Aug 2023
    • AC1: 'Reply on RC1', Takahito Mitsui, 06 Sep 2023
  • RC2: 'Comment on egusphere-2023-1267', Anonymous Referee #2, 28 Sep 2023
    • AC2: 'Reply on RC2', Takahito Mitsui, 25 Oct 2023

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1267', Anonymous Referee #1, 21 Aug 2023
    • AC1: 'Reply on RC1', Takahito Mitsui, 06 Sep 2023
  • RC2: 'Comment on egusphere-2023-1267', Anonymous Referee #2, 28 Sep 2023
    • AC2: 'Reply on RC2', Takahito Mitsui, 25 Oct 2023
Takahito Mitsui and Niklas Boers
Takahito Mitsui and Niklas Boers

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Short summary
In general, the variance and the autocorrelation with small lag increase in a system approaching a bifurcation point. Using these indicators, we identify statistical precursor signals for the Dansgaard-Oeschger cooling events recorded in two climatic proxies of three Greenland ice core records. We then provide a dynamical systems theory that bridges the gap between observing statistical precursor signals and the physical precursor signs empirically known in paleoclimate research.