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

Abstract

We report changes in ice velocity of a 6.5 million km<sup>2</sup> region around South Pole encompassing the Ronne/Filchner and Ross Ice Shelves and a significant portion of the ice streams and glaciers that constitute their catchment areas. Using the first full interferometric 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 m yr<sup>–1</sup>. The largest observed changes, an increase in speed of 100 m yr<sup>–1</sup> in 12 yr, are near the frontal regions of the large ice shelves and are associated with the slow detachment of 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 m yr<sup>–1</sup> (16.7 %) and 100 m yr<sup>–1</sup> (25.3 %) at their grounding lines. The slow down spreads 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 are MacAyeal Ice Stream and Byrd Glacier with a 12 yr velocity difference near their grounding lines of 30 m yr<sup>–1</sup> (6.7 %) and 35 m yr<sup>–1</sup> (4.1 %), respectively. Bindschadler Ice Stream is faster by 20 m yr<sup>–1</sup> (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 difference in glacier speed is below the 8 % level. We detect the largest slow down with a 12 yr velocity difference of up to 30 m yr<sup>–1</sup> on Slessor and Recovery Glaciers, equivalent to 6.7 % and 3.3 %, respectively. Foundation Ice Stream shows a modest speed up (30 m yr<sup>–1</sup> 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 difference of 50 m yr<sup>–1</sup>, or 5 % of its ice 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

The influence of subglacial hydrology on the flow of Kamb Ice Stream, West Antarctica

“…The neighboring Whillans Ice Stream (WIS) slowed down by 23% in 1979–1997 [ Joughin et al ., ] and is now slowing down by about 1% per year [ Joughin et al ., ], possibly to become stagnant within this century [ Bougamont et al ., ]. Less dramatic, but nonetheless important, is the 6% slowdown of MacAyeal Ice Stream and the 5% speed up of Bindschadler Ice Stream in 1997–2009 [ Scheuchl et al ., ], which shows that the Siple Coast ice streams are not flowing at a steady pace. This unsteady flow is seemingly consistent with inferred past flow: WIS apparently stagnated 850 years ago and reactivated 350 years later, while MAIS stopped 800 years ago and reactivated 150 years later [ Hulbe and Fahnestock , ; Catania et al ., ].…”

Geomorphological mapping of ice-free areas using polarimetric RADARSAT-2 data on Fildes Peninsula and Ardley Island, Antarctica

“…Research work has been published to illustrate the surface mapping capabilities of RADARSAT-2 and its potential for global exploration applications within the Antarctic region (Scheuchl et al, 2012;Schmid et al, 2012). This has also been shown by the RADARSAT-2 Antarctica mosaic that was acquired during 2008 (Hillman et al, 2011).…”

Sedimentology and biomarker geochemistry of a Kamb Ice Stream subglacial channel, West Antarctica

“…The influence of the subglacial hydrology in the Siple Coast system is apparent from the changes in ice stream flow over time, which are all hypothesised to be due to the availability and rerouting of subglacial water. For example, KIS stagnated approximately 160 years ago (Retzlaff and Bentley, 1993), WIS slowed down by 23 % between 1979 and 1997 (Joughin et al, 2002), and BIS sped up by 5 % between 1997 and 2009 (Scheuchl et al, 2012). Before the stagnation of KIS, it flowed at speeds >350 m yr -1 (Ng and Conway, 2004) until it slowed to ~10 m yr -1 approximately 150 years ago (Ng and Conway, 2004;Retzlaff and Bentley, 1993).…”