Time-variable ice loss in Asian high mountains from satellite gravimetry

Abstract

Substantial amount of glacial ice is considered to be melting in the Asian high mountains. Gravimetry by GRACE satellite during 2003–2009 suggests the average ice loss rate in this region of 47 ± 12 Gigaton (Gt) yr − 1 , equivalent to ∼ 0.13 ± 0.04 mm yr − 1 sea level rise. This is twice as fast as the average rate over ∼ 40 years before the studied period, and agrees with the global tendency of accelerating glacial loss. Such ice loss rate varies both in time and space; mass loss in Himalaya is slightly decelerating while those in northwestern glaciers show clear acceleration. Uncertainty still remains in the groundwater decline in northern India, and proportion of almost isostatic (e.g. tectonic uplift) and non-isostatic (e.g. glacial isostatic adjustment) portions in the current uplift rate of the Tibetan Plateau. If gravity increase associated with ongoing glacial isostatic adjustment partially canceled the negative gravity trend, the corrected ice loss rate could reach 61 Gt yr − 1 .