Preprints
https://doi.org/10.5194/tc-2021-6
https://doi.org/10.5194/tc-2021-6

  19 Feb 2021

19 Feb 2021

Review status: this preprint is currently under review for the journal TC.

The contribution of melt ponds to enhanced Arctic sea-ice melt during the Last Interglacial

Rachel Diamond1,2, Louise C. Sime1, David Schroeder3, and Maria-Vittoria Guarino1,4 Rachel Diamond et al.
  • 1British Antarctic Survey, Cambridge, UK
  • 2Imperial College London, London, UK
  • 3Department of Meteorology, University of Reading, Reading, UK
  • 4Faculty of Engineering and Physical Sciences, University of Leeds, Leeds, UK

Abstract. HadGEM3 is the first coupled climate model to simulate an ice-free Arctic during the Last Interglacial (LIG), 127 000 years ago. This simulation appears to yield accurate Arctic surface temperatures during the summer season. Here, we investigate the causes and impacts of this extreme simulated ice loss. We find that the summer ice melt is predominantly driven by thermodynamic processes: atmospheric and ocean circulation changes do not significantly contribute to the ice loss. We demonstrate these thermodynamic processes are significantly impacted by melt ponds, which form on average 8 days earlier during the LIG than during the pre-industrial control (PI) simulation. This relatively small difference significantly changes the LIG surface energy balance, and strengthens the albedo feedback. Compared to the PI simulation: in mid-June, of the absorbed flux at the surface over ice-covered cells (ice concentration > 0.15), ponds account for 45–50 %, open water 45 %, and bare ice and snow 5–10 %. We show that the simulated ice loss leads to large Arctic sea surface salinity and temperature changes. The sea surface temperature and salinity signals we identify here provide a means to verify, in marine observations, if and when an ice-free Arctic occurred during the LIG. Strong LIG correlations between spring melt pond and summer ice area indicate that, as Arctic ice continues to thin in future, the spring melt pond area will likely become an increasingly reliable predictor of the September sea-ice area. Finally, we note that models with explicitly modelled melt ponds seem to simulate particularly low LIG sea ice extent. These results show that models with explicit (as opposed to parameterised) melt ponds can simulate very different sea-ice behaviour under forcings other than the present-day. This is of concern for future projections of sea-ice loss.

Rachel Diamond et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Review_Diamondetal.2021', Anonymous Referee #1, 19 Mar 2021
  • RC2: 'Comment on tc-2021-6', Anonymous Referee #2, 11 Apr 2021

Rachel Diamond et al.

Rachel Diamond et al.

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Short summary
HadGEM3 is the first coupled climate model to simulate an ice-free summer Arctic during the Last Interglacial (LIG), 127 000 years ago, and yields accurate Arctic surface temperatures. We investigate the causes and impacts of this extreme simulated ice loss, and in particular, the role of melt ponds.