Tropical snowline changes at the last glacial maximum: A global assessment

Snowline reconstructions from the tropics and subtropics (33°S-33°N) at the last glacial maximum (LGM) have been extracted from a new database which provides information on glacier equilibrium-line altitudes (ELAs) for over 350 glacier-valley localities during the Late Quaternary. About 60% of the intra-regional variability observed change in ELA (ΔELA) between the LGM and today is related to headwall altitude, reflecting the influence of basin morphometry (e.g. catchment size, glacier slope) on the response to climate change. Glacier-valley aspect, which influences the local patterns of radiation and precipitation, also causes intra-regional variability in ΔELA although this influence varies greatly between regions. Overall, reconstructed ΔELAs are smallest in the Himalayas, relatively small in the southern central Andes and East Africa, and largest in the northern Andes, Mexico and Papua New Guinea. Estimates of the temperature change implied by the range of ΔELA within any one region, calculated using the CRU 10′ modern climate database, are consistent with high-altitude temperature changes projected from reconstructions of temperature changes at lower altitude sites based in vegetation and geochemical data in the 21 ka TROPICS data set [Farrera et al., 1999. Climate Dynamics 15, 823-856].