Modelling Greenland’s abrupt ancient warming

Abrupt warming episodes punctuate Greenland ice core records throughout the last glacial period. These events were first identified in two Greenland stable water isotope records (Dansgaard et al., 1993), and are generally referred to as Dansgaard-Oeschger (DO) events.

During an event, Greenland transitions from cold stadial (GS) to warmer Greenland Interstadial (GI) conditions within a decade (Kindler et al., 2014; Huber et al., 2006). Surface air temperatures (SATs) over Greenland increase by 10-15°C and local snow accumulation almost doubles (Andersen et al., 2006; Kindler et al., 2014; Huber et al., 2006).

These events occur at the onset of an oscillation that is of millennial timescale and are rather pronounced during Marine Isotope Stage3 (MIS3; between approximately 25 – 60 thousand of years BP, hereafter ka) (Fig. 1; Johnsen et al. (2001), Voelker et al.(2002)).

There are currently few examples of spontaneous DO-type oscillations occurring in coupled climate models, under any climate conditions, glacial-state or otherwise. For example the Max-Planck Institute Earth System Model (MPI-ESM) model is able to reproduce spontaneous millennial-scale AMOC oscillations when implementing PI ice sheet distribution in combination with a CO2 concentration range of 195-217 ppm (Klockmann et al., 2018, 2020) (See Figure 1).

Under full glacial conditions, Peltier and Vettoretti (2014) found regular cycles of DO-type oscillations with the University of Toronto version of CCSM4 (UofT CCSM4) (See Figure 1). Authors term this behaviour as a “kicked” salt oscillator. Under late glacial conditions, at 30 ka, a quasi-oscillating AMOC is produced by the HadCM3 model (Armstrong et al., 2021) and results from a North Atlantic salt oscillator mechanism similar to that in UofT CCSM4 (Peltier and Vettoretti, 2014; Vettoretti and Peltier, 2016; Peltier et al., 2020) (See Figure 1).

SDOO is an ongoing model intercomparison project to study spontaneous, DO-type oscillations in climate models. SDOO is currently gathering model output for any spontaneously oscillating simulations (published or unpublished). The main goal of SDOO is to cross compare existing simulations using a common set of diagnostics so we can analyse the mechanisms and the characteristics of the oscillations.

The only condition to participate is a simulation that shows spontaneous, long time scale, oscillations. The table below shows the simulations and models currently involved in this initiative.

SIMULATIONS

Data already uploaded to JASMIN (https://help.jasmin.ac.uk/) and available for analysis.

SDOO is organized by:

• Irene Malmierca-Vallet, irealm37@bas.ac.uk
• Louise C. Sime, lsim@bas.ac.uk
• Paul J. Valdes, P.J.Valdes@bristol.ac.uk

and has contributions from Marlene Klockmann (MPI-ESM), Qiong Zhang (EC-Earth3-Veg-LR), Olivier Arzel (UVIC 2.8), Dick Peltier and Guido Vettoretti (UofT CCSM4), Georg Feulner (CLIMBER-3α), John Slaterry and Yvan Rome (HadCM3).

This project is TiPES contribution #123: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 820970.