We have been focused on monitoring changes in the motion and thickness of the large ice fields in Alaska and Patagonia between 1992 and present. Although these non-polar ice fields are not as massive as Greenland or Antarctica, they are much more responsive to climate forcing than the larger ice fields and appear to have a significant effect on recent sea level rise and the availability of fresh water resources.
We are using primarily space-based techniques (SAR and optical feature tracking, Digital Elevation Models from optical stereo data, and InSAR) to measure changes in ice elevation and velocities.
To date we have been primarily focused on developing software to calculate the elevation change and glacier velocities using large quantities of SAR and optical images and validating our software against independent measurements -- including ground measurements from the Juneau Icefield Research Program and the COSI-CORR software (Leprince et al., 2007). We have released a version of this software that performs the velocity measurements using other open- source packages like AROP (Gao et al., 2009) and ROI_PAC (roipac.org).
Our initial results using this software indicate thinning of glaciers in some areas of northern Patagonia (top image) without appreciable increase in velocity, suggesting that local changes in precipitation/melting are the cause instead of glacier dynamics.
We are making similar observations over the Juneau Icefield (bottom image) in Alaska because we are able to compare our space-based measurements of glacier velocity to those made by GPS surveying by the Juneau Icefield Research Program (JIRP). Our initial results confirm the JIRP studies showing relative unchanging velocities between 1993-2007.
Conference abstracts:
Willis, M. J., A. K. Melkonian, M. E. Pritchard, and S. A. Bernstein (2010) Remote sensing of velocities and elevation changes at outlet glaciers of the northern Patagonian Icefield, Chile (abstract), Ice and Climate Change Conference: A View from the South, Valdivia, Chile
Melkonian, A. K., M. J. Willis, M. E. Pritchard, and S. A. Bernstein (2009) Glacier velocities and elevation change of the Juneau Icefield, Alaska (abstract C51B-0490,), AGU Fall meeting.