An evaluation of snowline data across New Guinea during the last major glaciation, and area-based glacier snowlines in the Mt. Jaya region of Papua, Indonesia, during the Last Glacial Maximum

Abstract

Geomorphological mapping and lake-core data from Mt. Jaya, western New Guinea, show that Last Glacial Maximum (LGM) glaciation was less extensive than previously thought. Average equilibrium line altitudes (ELAs), calculated using the area–altitude-balance ratio method, for minimum and maximum ice configurations were 4050±49 and 4000±56 m a.s.l., respectively. This is about 600 m below the ELA of the Mt. Jaya glaciers in 1971–73 and ca 400 m higher than values previously quoted for LGM ELAs in this area. A reappraisal of the evidence used to reconstruct the ELA of glaciers across New Guinea suggests that published chronologies are not sufficient to demonstrate that reported ELAs fall within the LGM window of 21,000±2 yr BP. Furthermore, the published information only constrains the altitude of the ELAs between 3400 and 3800 m a.s.l., not including uncertainty in topography. A simple mass and energy-balance model indicates that an ELA depression of 500 m (i.e., the observed change at Mt. Jaya after adjustment for sea-level change) could be accomplished with 2.5–3 °C of cooling provided precipitation was reduced by 35% and lapse rate changed. This cooling is less than the 6–8 °C cooling inferred from LGM pollen.