Earth from space
Earth from space

NASA instruments flying on the Terra satellite have observed the calving of an iceberg and the breakup of an ice shelf in Antarctica, roughly 2,100 kilometers (1,300 miles) from one another.

Last month, a large crack developed in the Thwaites Tongue, a large sheet of glacial ice that extends from the West Antarctica mainland into the southern Amundsen Sea. A piece broke away, or calved, forming an iceberg designated B-22 by the National Ice Center. In February, a section of the Larsen B ice shelf, located on the familiar finger-like Antarctic Peninsula, collapsed and broke away from the peninsula.

The progression of both breakups were initially observed by NASA's Moderate Resolution Imaging Spectroradiometer. Images of the subsequent calving and ice shelf breakup were captured by NASA's Multi-angle Imaging SpectroRadiometer.

The B-22 iceberg measures approximately 82 kilometers (about 51 miles) long by 62 kilometers (about 38 miles) wide. Comparison of the images shows the iceberg, located below and to the left of center, has drifted away from the ice shelf. The breakup of ice near the shelf edge, in the area surrounding B-22, is also visible in the later image.

These natural-color images were acquired on March 10 and 24, 2002, respectively. Antarctic researchers have reported an increase in the frequency of iceberg calving in recent years. It has not yet been established if this is a result of regional climate variation or the global warming trend.

The two views of the ice shelf breakup, acquired on March 7, 2002, provide helpful chemical and topographical perspectives. In the left-hand image, near-infrared, red and blue data from the Multi-angle Imaging SpectroRadiometer's nadir (vertical-viewing) camera causes water ice within the ice shelf to appear vibrant blue. Water has an intrinsic blue color due to the selective absorption of longer wavelengths such as red and infrared, and the translucent properties of ice within the collapsing shelf enables this absorption to be observed.

Data from three different cameras on the instrument and one color channel were combined to create the multi-angle composite on the right. Because vertical protrusions or depressions within textured surfaces appear brighter on their illuminated faces, the orange color in the multi-angle composite suggests a rough ice surface.

The Multi-angle Imaging SpectroRadiometer, built and managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., is one of several Earth-observing experiments aboard Terra, launched in December 1999. The instrument acquires images of Earth at nine angles simultaneously, using nine separate cameras pointed forward, downward, and backward along its flight path. The Terra mission supports NASA's Earth Science Enterprise, a long-term research effort designed to help better understand and protect our home planet.

JPL is a division of the California Institute of Technology in Pasadena.

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