Disintegration of the Ninnis Glacier Tongue
By Laurie J. Schmidt
Many processes that shape the Earth's landscape happen too slowly to be witnessed in a human lifetime. But recent analysis of satellite imagery shows that a large glacier tongue on the coast of East Antarctica has disintegrated, changing the shape of the coastline almost overnight.

An Antarctic penguin toboggans across the ice. (Image courtesy of NOAA).

NASA tracks iceberg B-10A, originally part of the Thwaites Ice Tongue.
An ice sheet is a dome-shaped mass of glacier ice with an area greater than 50,000 square kilometers (19,300 square miles). Under the influence of gravity, ice flows downhill from high points on the ice sheet towards the coast in the form of glaciers. At or near the coast, some of these glaciers flow directly into the ocean and develop floating extensions, called "glacier tongues." Blocks of ice periodically break off, or calve, from the glacier tongues and float free as icebergs.

A large portion of the Larsen B ice shelf breaks off the West Antarctic Peninsula, February 13, 1995.

Continued retreat along the northern two-thirds of the shelf front, January 6, 2000. (Images courtesy of the National Snow and Ice Data Center).
The George V Land coast was first explored and mapped by members of the "eastern coastal party" of the Australasian Antarctic Expedition of 1911 to 1914, under the leadership of Sir Douglas Mawson. A 1996 study of the George V Land coast, which employed data acquired by the Japanese SAR satellite JERS-1, indicated that the Ninnis Glacier Tongue lost approximately two-thirds of its size between 1912 and 1993. But a more recent study (1998) of the Oates and George V Land coasts casts doubt on the expedition's mapping accuracy, suggesting that the most significant retreat of the Ninnis Glacier Tongue took place after 1980, with a significant calving event also occurring in the early 1950s.

January 22, 2000. This image captures the Ninnis Glacier Tongue region soon after the initial calving. The resultant iceberg (sections A and B) has an area of approximately 900 square kilometers (560 square miles). NOTE: Purple dots indicate the area where the iceberg broke away from the glacier.
Perhaps the most dramatic breakup of Antarctic coastal ice in recent years was the disintegration of the Larsen Ice Shelf on the eastern side of the Antarctic Peninsula. Researchers at the National Snow and Ice Data Center and the British Antarctic Survey attributed this event to regional warming trends, reporting an increase in mean annual temperature of about 2.5 degrees Celsius (4.5 degrees Fahrenheit) since the 1940s.

February 5, 2000. This image captures the iceberg after it split into two sections (A and B). By 5 February 2000, Berg A had drifted 20 kilometers (about 12.5 miles) to the west, Berg B had drifted to the northeast, and a smaller section (C) remained grounded in front of the Ninnis Glacier.
The disintegration marks the final phase in a progressive retreat of the Ninnis Glacier Tongue. In 1989 Landsat imagery captured a split in the glacier tongue caused by shearing forces in the glacial ice. By 1993, the split had extended laterally across 60 percent of the glacier.

February 20, 2000. By 20 February 2000, Bergs A and B had almost totally separated, rotated counterclockwise, and drifted to the north. Note that both sections are now well away from the Ninnis Glacier.
Each image is a sub-section of a SCANSAR scene of the Ninnis Glacier Tongue region. (Images courtesy of Dr. Rob Massom, Antarctic CRC © 2000 Canadian Space Agency).
References
Frezzotti, M., A. Cimbelli, and J.G. Ferrigno, 1998: Ice-front change and iceberg behaviour along Oates and George V Coasts, Antarctica, 1912-96, Annals of Glaciology, 27, pp. 643-650.
Massom, R. 2000. Sudden Disintegration of the Ninnis Glacier Tongue, East Antarctica.
Wendler, G., K. Ahlnas, and C.S. Lingle, 1996: On Mertz and Ninnis Glaciers, East Antarctica, Journal of Glaciology, 42, pp. 447-453.
For more information
NASA Alaska Satellite Facility Distributed Active Archive Center (ASF DAAC)
NASA National Snow and Ice Data Center (NSIDC DAAC)
About the remote sensing data used | ||
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Satellite | Advanced Very High Resolution Radiometer (AVHRR) JERS-1 |
Landsat |
Sensor | SAR | |
Parameter | Antarctic sea ice |
|
DAAC | NASA Alaska Satellite Facility Distributed Active Archive Center (ASF DAAC) |
NASA National Snow and Ice Data Center DAAC (NSIDC DAAC) |
Page Last Updated: Jul 21, 2020 at 7:30 PM EDT