Special Physics Seminar*

March 7, 2:00 SC-170

  Using Satellite Radars to Measure Motion and Change on the Earth's Large Ice Sheets

Dr. Laurence Gray
Canada Centre for Remote Sensing

Radar data from remote sensing satellites can now be used to measure subtle movement on the Earth's surface, e.g. volcano inflation and deflation, terrain subsidence and displacements, and glacier and ice sheet motion. The radar looks perpendicular to the direction the satellite is moving, and as the satellites are in ‘polar orbits,' images can be created over most of the Earth's surface irrespective of weather or sunlight. I'll explain how these images from the “synthetic aperture radar” are created, and how surface motion can be estimated using a technique known as “interferometric SAR”, or InSAR.

Although InSAR is now used for many applications, I will concentrate on how it has trans-formed our understanding of the motion of glacial ice. Perhaps the most striking and surprising result from this effort has been an appreciation of how fast things can change. For example, over a period of a few years some outlet glaciers in southern Greenland have increased speed significantly, apparently the result of regional warming and increased surface melt. I'll also describe some of the work done by the joint Canadian Space Agency - NASA Antarctic Mapping Mission which produced the first high resolution image map of Antarctica showing new ice streams and tributary systems. The results have enabled us to calculate the flux of ice entering the oceans (and thereby estimate the contribution to sea level rise), to measure melt on the bottom surface of ice shelves and even gauge the flux of water transport beneath the ice.

  Satellite image map of ice velocity in West Antarctica showing the fast-flowing ice streams and their tributaries. Orange to purple colors indicate velocities greater than 400 m/year.

  * This lecture is sponsored by the Grace A. Whittier Endowment for the Natural Sciences