1. Helen Amanda Fricker Scripps Institution of Oceanography Ted Scambos National Snow and Ice Data Center Bob Bindschadler NASA/GSFC Space Flight Center Laurie Padman Earth & Space Research Photos of Whillans Ice Stream courtesy of Lee Powell and Charlie Bentley, 1987-88 season & edited by Robert Phillips AAAS/NASA press briefing – San Francisco – 15 February 2007 Antarctic subglacial plumbing mapped from space

2. Helen Amanda Fricker Scripps Institution of Oceanography, La Jolla, CA AAAS/NASA press briefing – San Francisco – 15 February 2007

3. NASAs ICESat mission and launch Ice Cloud and land Elevation Satellite (ICESat) launched 12 Jan 2003 from Vandenberg, CA Primary goal of ICESat mission is ice sheet change detection AAAS/NASA press briefing – San Francisco – 15 February 2007

4. Schematic of single profile science data measurements, compiled through time to build elevation data sets ICESat laser altimeter Surface elevations along a ground track determined from laser time of flight, combined with precise orbit and pointing information ICESat has 3 lasers and is switched on for ~33 days every ~4 months in a repeat track pattern (which enabled this discovery) Geoscience Laser Altimeter System (GLAS) AAAS/NASA press briefing – San Francisco – 15 February 2007

5. ICESat repeat-track analysis + indicates surface uplift (filling) - indicates surface deflation (draining) ~ indicates oscillating (i.e. doing both) Conway Ridge Engelhardt Ridge Whillans Ice Stream (B) Mercer Ice Stream (A) Elevation range 2003-06 (m) 0 9m MOA (NSIDC) AAAS/NASA press briefing – San Francisco – 15 February 2007

6. Subglacial Lake Engelhardt Conway Ridge Engelhardt Ridge Largest event in magnitude: deflating WAIS Meeting 2006 ICESat elevation range (m) 09 Whillans Ice Stream (B) Mercer Ice Stream (A) AAAS/NASA press briefing – San Francisco – 15 February 2007

7. Ted Scambos National Snow and Ice Data Center, Boulder, CO (by telephone) AAAS/NASA press briefing – San Francisco – 15 February 2007

8. Conway Ridge Engelhardt Ridge Elevation range 2003-06 (m) 0 9m + indicates surface uplift (filling) - indicates surface deflation (draining) ~ indicates oscillating (i.e. doing both) Satellite image differencing Uplift Subsidence Whillans Ice Stream (B) Mercer Ice Stream (A) MOA (NSIDC) AAAS/NASA press briefing – San Francisco – 15 February 2007

9. Hydraulic potential map Conway Ridge Engelhardt Ridge Conway Ridge Engelhardt Ridge Whillans Ice Stream (B) Mercer Ice Stream (A) Whillans Ice Stream (B) Mercer Ice Stream (A) Elevation range 2003-06 (m) 0 9m MOA (NSIDC) AAAS/NASA press briefing – San Francisco – 15 February 2007

10. Hydraulic potential map Engelhardt Ridge Conway Ridge SGL Engelhardt SGL Conway SGL Whillans SGL Mercer IMPORTANT: This is *not* topography AAAS/NASA press briefing – San Francisco – 15 February 2007

11. MODIS difference image: December 2005 minus December 2002 Subglacial Lake Engelhardt AAAS/NASA press briefing – San Francisco – 15 February 2007

12. Bob Bindschadler NASA Goddard Space Flight Center, Greenbelt, MD AAAS/NASA press briefing – San Francisco – 15 February 2007

13. Drawdown vs time at 3 crossovers Subglacial Lake Engelhardt Total volume loss ~ 2.0 km 3 to ocean cavity under Ross Ice Shelf through subglacial channel AAAS/NASA press briefing – San Francisco – 15 February 2007

14. Conway Ridge Engelhardt Ridge Whillans Ice Stream (B) Mercer Ice Stream (A) How much water in the system? Isolated Subglacial Lake Engelhardt lost ~2.0 km 3 over the observation period (33 months) Elevation range 2003-06 (m) 0 9m -2.0 km 3 SgLE SgLC SgLM +1.2 km 3 +0.12 km 3 +0.27 km 3 SgLW Remainder of the system had a net gain ~1.6 km 3 over the same period (~0.6 km 3 a -1 ) Net water gain is likely both reflecting and influencing the motion of these major Antarctic ice sheet outlet streams AAAS/NASA press briefing – San Francisco – 15 February 2007