16 Jun 2023
 | 16 Jun 2023
Status: this preprint is currently under review for the journal CP.

Climate and ice sheet dynamics in Patagonia during the Last Glacial Maximum

Andrés Castillo-Llarena, Franco Retamal-Ramírez, Jorge Bernales, Martín Jacques-Coper, and Irina Rogozhina

Abstract. During the Last Glacial Maximum (LGM, ~ 23,000 to 19,000 years ago), the Patagonian Ice Sheet (PIS) covered the central chain of the Andes between ~ 38° S to 55° S. Existing paleoclimatic evidence – mostly derived from glacial landforms – suggests that maximum ice sheet expansions in the Southern and Northern Hemispheres were not synchronized. However, large uncertainties still exist in the timing of the onset of regional deglaciation as well as its major drivers. Here we present an ensemble of numerical simulations of the PIS during the LGM. Our aim is to assess the ability of paleoclimate model products to reproduce the range of atmospheric conditions needed to enable the ice sheet growth in concordance with geomorphological and geochronological evidence. The resulting ensemble is then used as a guideline for the evaluation of the PMIP3 and PMIP4 model performance across different sectors of the former PIS. Our analysis suggests a strong dependence of the PIS geometry on near-surface air temperature forcing. All the ensemble members driven by PMIP products are not able to reproduce the reconstructed ice cover in the northern part of Patagonia. In contrast, the modelled PIS tends to expand beyond its constrained boundaries in south-eastern Patagonia. We largely attribute these discrepancies between the model-based ice geometries and geological evidence to the low resolution of paleoclimate models. We conclude that among all tested climate forcings, the PMIP4 climate models INM-CM4-8 and MPI-ESM1-2-LR produce the necessary conditions for ice sheet growth across Patagonia. It should be kept in mind that this analysis is based only on the evaluation of the modelled ice sheet extent because geological constraints on the former ice thickness are still lacking. Nevertheless, our analysis suggests that a realistic PIS geometry at the LGM can be reproduced only if the complex topographic features of the Andes are properly resolved by climate models.

Andrés Castillo-Llarena 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-2023-47', Anonymous Referee #1, 18 Jul 2023
  • RC2: 'Comment on cp-2023-47', Ilaria Tabone, 04 Oct 2023

Andrés Castillo-Llarena et al.

Andrés Castillo-Llarena et al.


Total article views: 468 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
349 111 8 468 5 5
  • HTML: 349
  • PDF: 111
  • XML: 8
  • Total: 468
  • BibTeX: 5
  • EndNote: 5
Views and downloads (calculated since 16 Jun 2023)
Cumulative views and downloads (calculated since 16 Jun 2023)

Viewed (geographical distribution)

Total article views: 466 (including HTML, PDF, and XML) Thereof 466 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
Latest update: 04 Oct 2023
Short summary
During the culmination of the cold glacial period, the Patagonian Ice Sheet grew along the southern Andes. In doing so, it left marks on the landscape showing its former extents and timing. Here we use paleoclimate and ice sheet models to replicate the growth of the ice sheet to its reconstructed margins. We find that errors in the model-based ice sheet geometries are likely induced by imprecise reconstructions of air temperature due to poorly resolved Andean topography in global climate models.