Glacier sensitivity and regional climate: Past and present.

摘要

This study develops a surface energy- and mass-balance model with which to understand the interactions between glaciers and climate on regional-scales. This model is applied to Central Asia because of the diverse climate regimes and glacier history. The model is used to understand the sensitivity of equilibrium line altitudes (ELAs) to modern interannual climate variability, and to reconcile patterns of ELA changes with climate changes during the early Holocene and Last Glacial Maximum (LGM) in Central Asia. Patterns in the present day climate give rise to patterns in the dominant ablation mechanisms at the ELA. In turn the patterns in ablation give rise to patterns in glacier sensitivity to climate changes. In particular, ELAs in melt-dominated regions are most sensitive to interannual variability in temperature. ELAs in sublimation-dominated regions are most sensitive to interannual variability in precipitation. The patterns of glacier advance and retreat during the early Holocene and LGM, in the melt-dominated regions, are both due to the patterns in temperature change. Glaciers in sublimation-dominated regions are highlighted as being acutely sensitive to even small changes in numerous atmospheric variables. For present day, Holocene, and LGM, changes in clouds are important in all regions through their influence on the shortwave and longwave radiative fluxes, which dominate the surface energy balance at the ELA. This work highlights the importance of a systematic analysis of the sensitivity of glaciers to changes in climate.