Last Glacial Maximum climate inferences from integrated reconstruction of glacier equilibrium-line altitude for the head of the Urumqi River,Tianshan Mountains

摘要

The relationship between climate and glacial equilibrium-line altitude (ELA) during the Last Glacial Maximum (LGM) has recently received considerable interest. However, in the headwaters of Urumqi River in northwest China, a systematic reconstruction for the paleo-ELAs had not been completed to permit regional and large-scale paleoclimate inferences. Recent improvements in dating and understanding of glacial extents provide the possibility to use glacial reconstruction to infer the paleoclimate. To improve the ability to obtain paleoclimate information, the ELAs during the local LGM (MIS2-3) and modern time (1998-2004) were constructed by using an integrated method. The regional tectonic uplift is considered when calculating the LGM ELAs in order to improve their precision and thus obtain a better estimate of the paleoclimate. The estimated ELA values were input into a robust equation to derive the forcing paleoclimatic conditions. During the local LGM in the study area, the ELA was between 3420 and 3560 m a.s.l., 493-633 m lower than modern ELA. Considering energy and mass balance in the equation to account for the ELA decrease, during the LGM, the temperature decreased by 5.42-6.30 ℃ and the precipitation was ～30% compared to the present.