Last Glacial Maximum Climate and Atmospheric Circulation over the Australian Region from Climate Models
Abstract. The Last Glacial Maximum (LGM, ~21,000 years ago) was the most recent time that the Earth experienced global maximum ice volume and minimum eustatic sea level. The regional climate changes over Australia at the LGM remain uncertain. Four Coupled Model Intercomparison Project Phase 6 (CMIP6) models and eight Coupled Model Intercomparison Project Phase 5 (CMIP5) models that were included in the Paleoclimate Modelling Intercomparison Project (PMIP) Phases 3 and 4 were used in this research to investigate the temperature, precipitation, and wind changes over Australia at the LGM relative to pre-industrial (PI) and compare the results with existing proxy records and other model studies. The annual multi-model mean (MMM) Australian land surface temperature is estimated to cool by 2.6 °C at the LGM. All models show consistent cooling over the Australian region (0–45° S, 110° E–160° E). The MMM annual precipitation decreased by 0.16 mm/day at the LGM relative to PI over modern Australian mainland areas (10° S–45° S, 110° E–160° E). Precipitation minus evaporation patterns over Australia are also examined to assess the changes in moisture balance at the LGM. Despite reduced LGM precipitation, the greater decrease in LGM evaporation leads to a slightly positive moisture balance in many regions. This is in disagreement with some proxy-based hydroclimate reconstructions of reduced LGM moisture over Australia, which might be due to the interpretations of vegetation-based proxy records or the uncertainties in model representation of moisture fluxes. We find a small equatorward multi-model average displacement of the boundary line between Southern Hemisphere (SH) westerly and easterly winds at the LGM but large model disagreement on a shift in SH mid-latitude westerly winds at the LGM, similar to previous studies.
Yanxuan Du et al.
Status: final response (author comments only)
- RC1: 'Comment on cp-2023-19', Anonymous Referee #1, 15 May 2023
- RC2: 'Comment on cp-2023-19', Anonymous Referee #2, 18 May 2023
- RC3: 'Comment on cp-2023-19', Anonymous Referee #3, 18 May 2023
Yanxuan Du et al.
Yanxuan Du et al.
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The knowledge of the characteristics and mechanism for the climate change over Australian regions in LGM is still not enough. This study investigated the climate changes at the LGM over the Australian region, in terms of temperature, precipitation, moisture balance and wind, based on the output from PMIP3 and PMIP4 simulations. The work might contribute to our understanding of the hydrological change of Australia in ice ages. The following are my comments and reviews for the authors’ consideration.
For the reconstruction, the background information of proxy used here and their uncertainty could be listed in a table. The information of the LGM climate getting wetter or drier and in which parts of Australia based on proxies is still not clear, even though the authors cited others’ work in line 459-463. It would be easier to read and make comparison if were there reconstructed data mapped on the plots of model results.
Line by line comments
Line 42. “Many regions”, could be pointed in details.
Line 92-100. The reconstructed evidence of moisture or hydrocliamte could be compared with model simulations in the section of discussions.
Line 155-157. There were three different ice sheet reconstructions. Thus it’s necessary to clarify the information of ice sheet configuration of the four models from PMIP4.
Table 2. In term of vegetation of PMIP4, were there any model using the dynamic vegetation? Please check and make it clear.
Line 180-182. Usually models use the last 100 years, instead of the first 100 years, to do analysis. Were there any big differences between those two choices?
Line 213-214. The difference between the analyses in the paper with Kageyama et al. may lies in the choice of ts, instead of SAT. Please check.