In:
The Cryosphere, Copernicus GmbH, Vol. 16, No. 6 ( 2022-06-24), p. 2505-2526
Abstract:
Abstract. In the Karakoram, dozens of glacier surges occurred in the past 2 decades,
making the region a global hotspot. 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 1 or 2 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 small region but differ strongly in surge behaviour. A full suite
of satellites (e.g. Landsat, Sentinel-1 and 2, Planet, TerraSAR-X, ICESat-2)
and digital elevation models (DEMs) from different sources (e.g. Shuttle Radar Topography
Mission, SRTM; Satellite Pour l’Observation de la Terre, SPOT; High Mountain Asia DEM, HMA DEM) 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 surges of 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 yr−1, velocities up to
30 m d−1, and surface elevations increasing by 170 m. In contrast, the
neighbouring and 3-times-smaller North Chongtar Glacier had a slow and
near-linear increase in advance rates (up to 500 m yr−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 yr−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 ATL03 data fit neatly to the other
DEMs. 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.
Type of Medium:
Online Resource
ISSN:
1994-0424
DOI:
10.5194/tc-16-2505-2022
DOI:
10.5194/tc-16-2505-2022-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2022
detail.hit.zdb_id:
2393169-3
Permalink
