18 Nov 2022
18 Nov 2022
Status: this preprint is open for discussion.

Climatic control on seasonal variations of glacier surface velocity

Ugo Nanni1,a, Dirk Scherler2,3, Francois Ayoub4, Romain Millan5, Frederic Herman6, and Jean-Philippe Avouac1 Ugo Nanni et al.
  • 1Division of Geological and Planetary Science, California Institute of Technology, Pasadena, CA, USA
  • 2Earth Surface Geochemistry, GFZ German Research Centre for Geosciences, Potsdam, Germany
  • 3Institute of Geographical Sciences, Freie Universität Berlin, Berlin, Germany
  • 4Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
  • 5University of Grenoble Alpes, CNRS, IRD, IGE, Grenoble, France
  • 6Institute of Earth Surface Dynamics, University of Lausanne, 1015 Lausanne, Switzerland
  • anow at: University of Oslo, Department of Geosciences, Norway

Abstract. Accurate measurements of ice flow are essential to predict future changes in glaciers and ice caps. Glacier displacement can in principle be measured at the large-scale by cross-correlation of satellite images. At weekly to monthly scales, the expected displacement is often of the same order noise for the commonly used satellite images, which limits the retrieval of accurate glacier velocity. Assessments of velocity changes on short time scales and over complex areas such as mountain ranges are therefore still lacking, but are essential to better understand how glacier dynamics are driven by internal and external factors. In this study, we take advantage of the wide availability and redundancy of satellite imagery over the Western Pamir to retrieve 10-day glacier velocity changes over 7 years for a wide range of glacier geometry and dynamics. Our results reveal strong seasonal trends. In spring/summer, we observe velocity increases of up to 300 % compared to a slow winter period. These accelerations clearly migrate upglacier throughout the melt-season, which we link to changes in subglacial hydrology efficiency. In autumn, we observe glacier accelerations that have rarely been observed before. These episodes are primarily confined to the upper ablation zone with a clear downglacier migration. We suggest that they result from glacier instabilities caused by sudden subglacial pressurization in response to (1) supraglacial pond drainage and/or (2) gradual closure of the hydrological system. Our 10-day resolved measurements allow us to characterize the short-term response of glacier to changing meteorological and climatic conditions.

Ugo Nanni et al.

Status: open (until 13 Jan 2023)

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Ugo Nanni et al.

Data sets

Data and codes used to processe the data Ugo Nanni

Video supplement

Seasonal changes in glacier surface velocity over the Western Pamir Ugo Nanni

Ugo Nanni et al.


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Short summary
Glacier movement can be measured with satellite images. Over weeks to months, this movement is often too little compared to noise. We analyze thousands of images and retrieve, for 7 years, 10-day velocity changes over 48 glaciers in the Pamir. We capture their responses to rapid meteorological changes. In spring, strong glacier accelerations propagate upglacier. In autumn, accelerations propagate downglacier. Both result from changes in meltwater input to the glacier bed.