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. In addition, I focus on improving the ways in which sea level rise information is packaged and presented in ways that can maximize its use by and value to planners, decision-makers, and policy-makers.
Using satellites and in situ measurements to study polar ice, my group works with space-based, airborne, and in situ observations to study changes in Earth’s glaciers and ice sheets, with a focus on three areas. The first is the development of methods for determining the nature and distribution of crevasses on the Greenland ice sheet from satellite laser altimetry data, and their implications for Greenland’s contributions to sea level rise. Crevasses are inherently three-dimensional in structure, so, while visible imagery can be used to map crevasses, laser altimetry, such as that provided by ICESat and its successor, ICESat-2, provide an opportunity to examine three-dimensional structure of the surface in ways that provide new information and new insights into crevasse distribution and structure on the Greenland ice sheet. These crevasses are a direct result stresses accumulated and released during glacier flow, and they provide a mechanism for delivering meltwater to the bottom of the ice sheet, which can have significant implications on glacier flow and ice sheet losses.
The second area of focus is on the characteristics of the seas surrounding Greenland and how their interactions with the outlet glaciers that drain the ice sheet impact the ways in which the sea/ice exchanges affect the discharge of ice from the ice sheets. The melting and retreat of floating ice (ice tongues) at the glacier fronts comprise the greatest uncertainty in determining how much and how fast the Greenland ice sheet will contribute to sea level rise. Understanding the thermodynamic and dynamic processes where the ice meets the water is critical to reducing that uncertainty and developing more reliable forecasts. Satellite observations of temperature, combined with in situ observations of temperature, salinity, and circulation, as well as ocean modeling results provide the opportunity to gain new insights into the processes that occur at these critical interfaces.
Finally, in addition to understanding the physical processes that affect ice sheet contributions to sea level rise, I lead an effort that engages scientists, decision-makers, policy-makers and planners to ensure that the users of sea level rise data are aware of and understand the current state of scientific knowledge and that the producers of sea level rise information understand user needs and communicate the state of scientific knowledge in ways that are most effective and useful.
Honors and Awards
- Selected to serve as NASA Chief Scientist, 2011–2012
- NASA GSFC Center Director 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)