Ph.D. University of Colorado (Boulder), 1996
Director of CIRES
Professor of Geography
My research interests are in the use of satellite and airborne remote sensing techniques, integrated with in situ observations and modeling, to understand how and why the Earth's ice cover is changing, and what those changes mean for life on Earth. In particular, my research focuses on the contributions of ice sheets and high-latitude glaciers to sea level rise and their relationship to the changing climate. Toward that end, I have been heavily involved in the development of NASA's Ice Cloud and land Elevation Satellite (ICESat) and its successor, ICESat-II, and I have worked on cryospheric applications of various other satellites and aircraft instruments. Most of my research is supported by NASA, where I worked as a scientist for 12 years, before joining CIRES. In 2011, I returned to NASA on a two-year assignment as the agency’s Chief Scientist, serving as principal adviser to the NASA Administrator on NASA scienceprograms, strategic planning, and the evaluation of related investments.
Current Research: Studying Ice from Space
From January 2011 through December 2012, I was on leave from the University of Colorado Boulder to serve as Chief Scientist of the National Aeronautics and Space Administration. In this capacity, I was the principal science advisor to the NASA Administrator and interfaced with the Executive Office of the President and Congress to ensure alignment among NASA, White House, and Congressional science priorities. The challenges and experiences as Chief Scientist, in particular interacting with an incredibly diverse array of scientists, politicians, and others, will enable me to better serve the CIRES and University community, particularly in my new role as CIRES Director (effective July 1, 2013). While I was on leave and since my return, I have worked with my graduate students and CIRES research scientists, using spacebased observations to study changes in Earth’s glaciers and ice sheets. This research is focused on three areas. The first is the development of methods for determining how much meltwater is stored in—and subsequently lost from—melt lakes on the surface of the Greenland Ice Sheet. This meltwater has significant implications for the speed at which the ice sheet flows toward the sea because the meltwater reduces friction between the ice and the bedrock on which it rests and also changes the deformation properties of the ice as the warm meltwater penetrates into the ice.
The second area of research has focused on understanding the nature of compaction of the near-surface firn (snow) on the Greenland Ice Sheet; this will improve the interpretation of satellite altimetry observations of ice-sheet-thickness changes. The third area has involved the use of data from the Gravity Recovery and Climate Experiment (GRACE) mission to separate the sea-level contributions from Greenland’s peripheral glaciers and ice caps from those of the main ice sheet. This partitioning helps us understand the relative importance of the mechanisms driving today’s ice-sheet changes and what that may mean for the future.
These areas of research are fundamental to our ultimate overarching objective of determining how and why Earth’s glaciers and ice sheets are changing and what those changes mean for life on Earth.
Honors and Awards
- Selected to serve as NASA Chief Scientist, 2011–2012
- NASA GSFC Center Director’s Team Recognition Award, 2007
- American Institute of Aeronautics and Astronaustics Space Systems Award, 2006
- National Aeronautics and Space Administration Exceptional Service Medal, 2004
- NASA Group Achievement Award, ICESat Science Team, 2004
- NASA Office of Earth Science Award, 2003
- NASA Group Achievement Award, Honor Award Team 2003
- NASA Office of Earth Science Terra Peer Award, 2002
- NASA Office of Earth Science Award, 2002
- NASA Office of Earth Science Award, 2001
- Presidential Early Career Award for Scientists and Engineers, 1999
- Tau Beta Pi National Engineering Honor Society (since 1985)