Satellite-observed monthly glacier and snow mass changes in southeast Tibet: implication for substantial meltwater contribution to the Brahmaputra

• Published in: The Cryosphere
• Main Authors: S. Yi, C. Song, K. Heki, S. Kang, Q. Wang, L. Chang
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2020
• Subjects: Environmental sciences; GE1-350; Geology; QE1-996.5; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-14-2267-2020; https://doaj.org/article/dc0addc18b134a67a9e692af3a414c1c

High-Asia glaciers have been observed to be retreating the fastest in the southeastern Tibet Plateau (SETP), where vast numbers of glaciers and amounts of snow feed the streamflow of the Brahmaputra, a transboundary river linking the world's two most populous countries, China and India. However, the low temporal resolutions in previous observations of glacier and snow (GS) mass balance obscured the seasonal accumulation–ablation variations, and their modelling estimates were divergent. Here we use monthly satellite gravimetry observations from August 2002 to June 2017 to estimate GS mass variation in the SETP. We find that the “spring-accumulation-type” glaciers and snow in the SETP reach their maximum in May. This is in stark contrast to seasonal variations in terrestrial water storage, which is controlled by summer precipitation and reaches the maximum in August. These two seasonal variations are mutually orthogonal and can be easily separated in time-variable gravity observations. Our GS mass balance results show a long-term trend of <math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">6.5</mn><mo>±</mo><mn mathvariant="normal">0.8</mn></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="52pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="239eae0452c1cc81f54fa09663bc589c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tc-14-2267-2020-ie00001.svg" width="52pt" height="10pt" src="tc-14-2267-2020-ie00001.png"/></svg:svg> Gt yr −1 (or 0.67±0.08 m w.e. yr −1 ) and annual mass decreases ranging from −49.3 to −78.3 Gt with an average of <math xmlns="http://www.w3.org/1998/Math/MathML" id="M7" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">64.5</mn><mo>±</mo><mn ...