Earth Imaging Journal: Remote Sensing, Satellite Images, Satellite Imagery
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This Envisat image shows the Pine Island Glacier in west Antarctica and reveals a crack in the glacier’s tongue about 25 kilometers long. The image was acquired by Envisat’s radar on April 6, 2012, just two days before contact with the satellite was lost. Satellite radar instruments are particularly useful over polar regions because they can see through clouds and darkness.

Twenty years of radar coverage from European Space Agency (ESA) satellites have been used to measure the rapid thinning of Antarctica’s Pine Island Glacier, and it’s losing more ice than previously thought.

Pine Island is the largest glacier in the West Antarctic Ice Sheet and one of the fastest ice streams on the continent. About one-tenth of the ice sheet drains out to the sea by way of this glacier. At the margins of ice sheets, ice lifts off of the land and floats out over the water as an ice shelf. Measuring these ice shelves and following their evolution is important for pinpointing the mass of an ice sheet and its contribution to changing sea levels.

But measuring them is difficult. Drilling and submarine surveys can be performed locally, but such techniques don’t provide the continuous and global measurements needed for accurate monitoring. Satellites can gather information frequently and over large areas, providing an effective way to quantify the melting of ice shelves. Radar instruments on satellites can “see” through clouds and in the dark, making them particularly suited for measurements over polar regions prone to bad weather and long periods of darkness.

During the course of 20 years, the orbits of ESA’s ERS satellites occasionally were modified to make more frequent measurements over the polar regions. Although the ERS-1 and -2 missions ended in 2000 and 2011, respectively, their archived data still are being mined to make discoveries.

In a recently published study, the accelerated thinning and the retreat of the boundary between the ice and the ocean—the grounding line—in Antarctica’s Pine Island Glacier were documented using ERS radar images. The results show that, between 1992 and 2011, the glacier’s grounding line retreated by 20 kilometers on average, reaching a maximum of 40 kilometers in the central section. The retreat remained constant while the ice thinned by more than 200 meters during the 20 years.

Image courtesy of ESA.

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