Climate Fact Of The Day – Antarctic ice shelves slowed down – “…have not been changed in a significant way in the past 12 years”

May 21st, 2012

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Climate Fact Of The Day – Antarctic ice shelves slowed down – “…have not been changed in a significant way in the past 12 years”

The Cryosphere Discuss., 6, 1715–1738, 2012 www.the-cryosphere-discuss.net/6/1715/2012/
doi:10.5194/tcd-6-1715-2012

Twelve years of ice velocity change in Antarctica observed by RADARSAT-1 and -2 satellite radar interferometry

Authors:
B. Scheuchl, J. Mouginot, and E. Rignot

Abstract
We report changes in ice velocity of a 6.5 million km region around South Pole encompassing the Ronne/Filchner and Ross Ice Shelves and a signi?cant portion of the ice streams and glaciers that constitute their catchment areas. Using the ?rst full interfero-metric synthetic-aperture radar (InSAR) coverage of the region completed in 2009 and partial coverage acquired in 1997, we process the data to assemble a comprehensive map of ice velocity changes with a nominal precision of detection of ±3–4 myr -1. The largest observed changes, an increase in speed of 100 myr?1 in 12 yr, are near the frontal regions of the large ice shelves and are associated with the slow detachment of 10 large tabular blocks that will eventually form icebergs. On the Ross Ice Shelf, our data reveal a slow down of Mercer and Whillans Ice Streams with a 12 yr velocity difference of 50 myr?1(16.7 %) and 100 myr-1 (25.3 %) at their grounding lines. The slow downspreads 450 km upstream of the grounding line and more than 500 km onto the shelf, i.e., far beyond what was previously known. Also slowing in the Ross Ice Shelf sector 15 are MacAyeal Ice Stream and Byrd Glacier with a 12 yr velocity di?erence near their grounding lines of 30 myr
-1(6.7 %) and 35 myr?1(4.1 %), respectively. Bindschadler Ice Stream is faster by 20 myr -1(5 %). Most of these changes in glacier speed extend on the Ross Ice Shelf along the ice streams’ flow lines. At the mouth of the Filchner/Ronne Ice Shelves, the 12 yr di?erence in glacier speed is below the 8 % level. We detect the largest slow down with a 12 yr velocity di?erence of up to 30 myr?1 20 onSlessor and Recovery glaciers, equivalent to 6.7 % and 3.3 %, respectively. Foundation Ice Stream shows a modest speed up (30 myr -1 or 5 %). No change is detected on Bailey, Rutford, and Institute Ice Streams. On the Filchner Ice Shelf proper, ice slowed down rather uniformly with a 12 yr velocity di?erence of 50 myr-1, or 5% of its ice 25 front speed, which we attribute to an 12 km advance in its ice front position.

Overall, we conclude that the ice streams and ice shelves in this broad region, in contrast with their counterparts in the Amundsen and Bellingshausen seas, exhibit changes in ice dynamics that have almost no impact on the overall ice balance of the region. Read Paper

Tags: Arctic Antarctica, climate