Preprints
https://doi.org/10.5194/tc-2021-90
https://doi.org/10.5194/tc-2021-90

  07 Apr 2021

07 Apr 2021

Review status: this preprint is currently under review for the journal TC.

Proglacial Lakes Elevate Glacier Surface Velocities in the Himalayan Region

Jan Bouke Pronk1, Tobias Bolch1, Owen King1, Bert Wouters2, and Douglas I. Benn1 Jan Bouke Pronk et al.
  • 1School of Geography and Sustainable Development, University of St Andrews, St Andrews, UK
  • 2Institute for Marine and Atmospheric Research Utrecht, Utrecht University, the Netherlands

Abstract. Meltwater from Himalayan glaciers sustains the flow of rivers such as the Ganges and Brahmaputra on which over half a billion people depend for day-to-day needs. Upstream areas are likely to be affected substantially by climate change, and changes in the magnitude and timing of meltwater supply are likely to occur in coming decades. About 10 % of the Himalayan glacier population terminates into pro-glacial lakes and such lake-terminating glaciers are known to exhibit higher than average total mass losses. However, relatively little is known about the mechanisms driving exacerbated ice loss from lake-terminating glaciers in the Himalaya. Here we examine a composite (2017–2019) glacier surface velocity dataset, derived from Sentinel 2 imagery, covering Central and Eastern Himalayan glaciers larger than 3 km2. We find that centre flow line velocities of lake-terminating glaciers are more than double those of land-terminating glaciers (18.8 vs 8.24 m yr−1) and show substantially more heterogeneity around glacier termini. We attribute this large heterogeneity to the varying influence of lakes on glacier dynamics, resulting in differential rates of dynamic thinning, which effects about half of the clean-ice lake-terminating glacier population. Numerical ice-flow model experiments show that changes at the frontal boundary condition are likely to play a key role in accelerating the glacier flow at the front, with variations in basal friction only being of modest importance. The expansion of current glacial lakes, and the formation of new meltwater bodies will influence the dynamics of an increasing number of Himalayan glaciers in the future; a scenario not currently considered in regional ice loss projections.

Jan Bouke Pronk et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2021-90', Anonymous Referee #1, 17 May 2021
    • AC1: 'Reply on RC1', Jan Bouke Pronk, 06 Jul 2021
  • RC2: 'Comment on tc-2021-90', Anonymous Referee #2, 28 May 2021
    • AC2: 'Reply on RC2', Jan Bouke Pronk, 06 Jul 2021

Jan Bouke Pronk et al.

Jan Bouke Pronk et al.

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Short summary
About 10 % of the Himalayan glaciers flow directly into lakes. This study finds, using satellite imagery, that such glaciers show higher flow velocities than glaciers without ice-lake contact. In particular near the glacier tongue the impact of a lake on the glacier flow can be dramatic. The development of current and new meltwater bodies will influence the flow of an increasing number of Himalayan glaciers in the future; a scenario not currently considered in regional ice loss projections.