Helen Amanda FrickerScripps Institution of Oceanography

Ted ScambosNational Snow and Ice Data Center

Bob BindschadlerNASA/GSFC Space Flight Center

Laurie PadmanEarth & 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 Antarctic subglacial plumbing mapped from spacemapped from space

Helen Amanda FrickerScripps Institution of Oceanography,

La Jolla, CA

AAAS/NASA press briefing – San Francisco – 15 February 2007

NASA’s 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

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

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

Subglacial Lake Engelhardt

Conway Ridge

Engelhardt Ridge

Largest event in magnitude: deflating

WAIS Meeting 2006

ICESat elevation range (m)

0 9

Whillans Ice Stream (B)

Mercer Ice Stream (A)

AAAS/NASA press briefing – San Francisco – 15 February 2007

Ted ScambosNational Snow and Ice Data Center,

Boulder, CO (by telephone)

AAAS/NASA press briefing – San Francisco – 15 February 2007

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

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

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

MODIS difference image: December 2005 minus December 2002

Subglacial Lake Engelhardt

AAAS/NASA press briefing – San Francisco – 15 February 2007

Bob BindschadlerNASA Goddard Space Flight Center,

Greenbelt, MD

AAAS/NASA press briefing – San Francisco – 15 February 2007

Drawdown vs time at 3 crossovers

Subglacial Lake Engelhardt

Total volume loss ~ 2.0 km3

to ocean cavity under Ross Ice Shelf through subglacial channel

AAAS/NASA press briefing – San Francisco – 15 February 2007

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 km3 over the observation period (33 months)

Elevation range 2003-06 (m)

0 9m

-2.0 km3

SgLE

SgLC

SgLM+1.2 km3

+0.12 km3

+0.27 km3SgLW

Remainder of the system had a net gain ~1.6 km3 over the same period (~0.6 km3a-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