04 Nov 2022
04 Nov 2022
Status: this preprint is open for discussion and under review for Climate of the Past (CP).

Deglacial climate changes as forced by ice sheet reconstructions

Nathaelle Bouttes1, Fanny Lhardy1,2, Aurelien Quiquet1,3, Didier Paillard1, Hugues Goosse4, and Didier M. Roche5 Nathaelle Bouttes et al.
  • 1Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA‐CNRS‐UVSQ, Université Paris‐Saclay, Gif‐sur‐Yvette, France
  • 2Max Planck Institute for Meteorology, Hamburg, Germany
  • 3Univ. Grenoble Alpes, CNRS, IRD, Grenoble INP, IGE, 38000 Grenoble, France
  • 4Earth and Life Institute, Université catholique de Louvain, Louvain-la-Neuve, Belgium
  • 5Earth and Climate Cluster, Faculty of Science, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands

Abstract. During the Last Deglaciation, the climate evolves from a cold state at the Last Glacial Maximum at 21 ka with large ice sheets, to the warm Holocene at ~9 ka with reduced ice sheets. The deglacial ice sheet melt can impact the climate through multiple ways: changes of topography and albedo, bathymetry and coastlines, as well as fresh water fluxes. In the PMIP4 protocol for deglacial simulations, these changes can be accounted or not depending on the modelling group choices. In addition, two ice sheet reconstructions are available (ICE-6G_C and GLAC-1D). In this study, we evaluate all these effects related to ice sheet changes on the climate using the iLOVECLIM model of intermediate complexity. We show that the two reconstructions yield the same warming to a first order, but with a different amplitude (3.9 °C with ICE-6G_C and 3.8 °C with GLAC-1D) and evolution. We obtain a stalling of temperature rise during the Antarctic Cold Reversal (from ~14 ka to ~12 ka) similar to proxy data only with the GLAC-1D ice sheet reconstruction. Accounting for changes in bathymetry in the simulations results in a cooling due to a larger sea ice extent and higher surface albedo. Finally, fresh water fluxes result in AMOC drawdown, but the timing in the simulations disagrees with proxy data of ocean circulation changes. This questions the links between reconstructed fresh water fluxes from ice sheet melt and recorded AMOC weakening and their representation in models.

Nathaelle Bouttes et al.

Status: open (until 30 Dec 2022)

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  • RC1: 'Comment on egusphere-2022-993', Anonymous Referee #1, 06 Dec 2022 reply

Nathaelle Bouttes et al.

Nathaelle Bouttes et al.


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Short summary
The Last Deglaciation is a period of large warming from 21,000 to 9,000 years ago, concomitant with ice sheet melting. Here we evaluate the impact of different ice sheet reconstructions and different processes linked to their changes. Changes of bathymetry and coastlines, although not often accounted for, cannot be neglected. Ice sheet melt results in fresh water into the ocean with large effects on ocean circulation, but the timing cannot explain the observed abrupt climate changes.