Preprints
https://doi.org/10.5194/tc-2021-370
https://doi.org/10.5194/tc-2021-370

  21 Dec 2021

21 Dec 2021

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

Three different glacier surges at a spot: What satellites observe and what not

Frank Paul1, Livia Piermattei2, Désirée Treichler2, Lin Gilbert3, Luc Girod2, Andreas Kääb2, Ludivine Libert4, Thomas Nagler4, Tazio Strozzi5, and Jan Wuite4 Frank Paul et al.
  • 1Department of Geography, University of Zurich, 8057 Zurich, Switzerland
  • 2Department of Geosciences, University of Oslo, P.O. Box 1047, 0316 Oslo, Norway
  • 3UCL-MSSL, Department of Space and Climate Physics, Mullard Space Science Laboratory, Holmbury St Mary, Surrey RH5 6NT, UK
  • 4ENVEO IT GmbH, Fürstenweg 176, 6020 Innsbruck, Austria
  • 5Gamma Remote Sensing, 3073 Gümligen, Switzerland

Abstract. In the Karakoram, dozens of glacier surges occurred in the past two decades, making the region one of its global hot spots. Detailed analyses of dense time series from optical and radar satellite images revealed a wide range of surge behaviour in this region: from slow advances longer than a decade at low flow velocities to short, pulse-like advances over one or two years with high velocities. In this study, we present an analysis of three currently surging glaciers in the central Karakoram: North and South Chongtar Glaciers and an unnamed glacier referred to as NN9. All three glaciers flow towards the same region but differ strongly in surge behaviour. A full suite of satellite sensors and digital elevation models (DEMs) from different sources are used to (a) obtain comprehensive information about the evolution of the surges from 2000 to 2021 and (b) to compare and evaluate capabilities and limitations of the different satellite sensors for monitoring relatively small glaciers in steep terrain. A strongly contrasting evolution of advance rates and flow velocities is found, though the elevation change pattern is more similar. For example, South Chongtar Glacier had short-lived advance rates above 10 km y−1, velocities up to 30 m d−1 and surface elevations increased by 200 m. In contrast, the neighbouring and three times smaller North Chongtar Glacier had a slow and near linear increase of advance rates (up to 500 m y−1), flow velocities below 1 m d−1 and elevation increases up to 100 m. The even smaller glacier NN9 changed from a slow advance to a full surge within a year, reaching advance rates higher than 1 km y−1. It seems that, despite a similar climatic setting, different surge mechanisms are at play and a transition from one mechanism to another can occur during a single surge. The sensor inter-comparison revealed a high agreement across sensors for deriving flow velocities, but limitations are found on small and narrow glaciers in steep terrain, in particular for Sentinel-1. All investigated DEMs have the required accuracy to clearly show the volume changes during the surges and elevations from ICESat-2 ATL06 data fit neatly. We conclude that the available satellite data allow for a comprehensive observation of glacier surges from space when combining different sensors to determine the temporal evolution of length, elevation and velocity changes.

Frank Paul et al.

Status: open (until 15 Feb 2022)

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Frank Paul et al.

Frank Paul et al.

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Short summary
Glacier surges are widespread in the Karakoram and have been intensely studied using satellite data and DEMs. In this study, we use time series of such datasets to study three glacier surges in the same region of the Karakoram. We found strongly contrasting advance rates/flow velocities, maximum velocities of 30 m/d and a change of the surge mechanism during a surge. A sensor comparison revealed good agreement, but steep terrain and the two smaller glaciers caused limitations for some of them.