Glaciers are important indicators of climate change. Although they may look frozen in place, they are always moving slowly under the weight of the ice. Tracking this movement helps scientists understand how glaciers are changing, how they may contribute to sea-level rise, how they affect freshwater resources, and whether they could trigger hazards such as ice avalanches or glacial lake outburst floods.
A review published in Geodesy and Geodynamics by a duo of researchers from Peking University examined the role of synthetic aperture radar (SAR) imaging geodesy in glacier velocity monitoring. In particular, the review covered the basic principles of SAR imaging geodesy, summarizes its applications in glaciology, and discusses future directions for the field.
“Glacier velocity is one of the key parameters used to describe glacier dynamics,” explains corresponding author Teng Wang. “It helps us assess how glaciers respond to climate change and provides important information for studying glacier mass balance.”
The du noted that, however, measuring glacier movement on the ground is difficult. “Many glaciers are located in remote, high-altitude, or polar regions, where fieldwork is challenging and long-term instruments are hard to install and maintain,” says Wang.
To that end, SAR remote sensing offers an effective alternative. “SAR satellites actively transmit electromagnetic waves and record the signals reflected from Earth’s surface,” says Wang. “This allows them to observe glaciers during day or night and in nearly all weather conditions.”
Compared with field-based approaches, SAR imaging geodesy provides non-contact, high-resolution measurements over large and difficult-to-access regions.
The review also compared several SAR-based methods for measuring glacier movement. “Among them, pixel offset tracking is especially useful for glacier studies,” shares co-author Meiling Wen. “Some radar methods can detect very small surface changes, sometimes at the centimeter or even millimeter scale, but they work best when the glacier surface remains relatively stable between two satellite images.”
Notably, when a glacier moves quickly, the surface pattern may change too much, making those methods less reliable. “Pixel offset tracking is better suited to large movements because it compares recognizable surface features in two images,” says Wen. “It can show how far a glacier has moved in different directions, making it well suited for mapping large glacier movements.”
The authors divided the development of SAR-based glacier velocity monitoring into three stages: preliminary application from 1993 to 2010, gradual improvement from 2011 to 2014, and wide application from 2015 to the present. “Since the first application of SAR imaging geodesy to glacier monitoring in 1993, these methods have been applied to almost all large glaciers on Earth,” says Wen. “In reviewed studies, glacier flow rates have reached 800 m/year and even 1200 m/year, and one Greenland study involved more than 900 SAR images.”
Looking ahead, the researchers highlight the need to improve the computational efficiency of pixel offset tracking, combine multiple SAR methods to strengthen accuracy and reliability, and integrate SAR with optical image tracking to better measure glacier deformation in three dimensions.
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Contact the author:
Teng Wang（School of Earth and Space Sciences, Peking University, Beijing 100091, China）
The publisher KeAi was established by Elsevier and China Science Publishing & Media Ltd to unfold quality research globally. In 2013, our focus shifted to open access publishing. We now proudly publish more than 200 world-class, open access, English language journals, spanning all scientific disciplines. Many of these are titles we publish in partnership with prestigious societies and academic institutions, such as the National Natural Science Foundation of China (NSFC).
Geodesy and Geodynamics
Systematic review
Not applicable
Review of SAR imaging geodesy for glacier velocity monitoring
The author declares no conflicts of interest.