HR: 11:50h
AN: C12A-07    [Abstracts]
TI: Estimates of Glacier Mass Change in the St.~Elias Mountains of Alaska, USA and Yukon Territory, Canada: a Strategy for Combining GRACE and Aircraft Laser Altimetry Data
AU: * Arendt, A
EM: arendt@icesat2.gsfc.nasa.gov
AF: Oak Ridge Associated Universities at NASA Goddard Space Flight Center, Cryospheric Sciences Branch, Greenbelt, MD 20771, United States
AU: Luthcke, S
EM: Scott.B.Luthcke@nasa.gov
AF: NASA Goddard Space Flight Center, Planetary Geodynamics Laboratory, Greenbelt, MD 20771, United States
AU: Abdalati, W
EM: waleed@icesat2.gsfc.nasa.gov
AF: NASA Goddard Space Flight Center, Cryospheric Sciences Branch, Greenbelt, MD 20771, United States
AU: Larsen, C
EM: chris@gi.alaska.edu
AF: Geophysical Institute, University of Alaska, Fairbanks, Fairbanks, AK 99775, United States
AU: Lingle, C
EM: clingle@gi.alaska.edu
AF: Geophysical Institute, University of Alaska, Fairbanks, Fairbanks, AK 99775, United States
AU: Echelmeyer, K
AF: Geophysical Institute, University of Alaska, Fairbanks, Fairbanks, AK 99775, United States
AU: Rowlands, D
EM: david.d.rowlands@nasa.gov
AF: NASA Goddard Space Flight Center, Planetary Geodynamics Laboratory, Greenbelt, MD 20771, United States
AU: Krabill, W
EM: william.b.krabill@nasa.gov
AF: NASA Wallops Flight Facility, Cryospheric Sciences Branch, Wallops Island, VA 23337, United States
AB: We describe a strategy for estimating the contribution of mountain glaciers to rising sea level by combining two independent geodetic techniques: (1) repeat-pass aircraft laser altimetry measurements of glacier surface elevations; and (2) Gravity Recovery and Climate Experiment (GRACE) estimates of variations in Earth mass. Repeated laser altimetry measurements provide elevation changes along the central flowline of individual glaciers, but extrapolating these to entire glacier regions is a challenge, especially for glaciers with complex dynamics. Conversion of elevation to mass changes can also be problematic, especially over short measurement intervals. GRACE yields a direct measure of mass change over broad regions, but corrections must be made for non-glacier sources of mass change in order to isolate the glacier mass balance signal. In some cases, uncertainties in models or observations of non-glacier sources of mass change, such as glacial isostatic adjustments, can be large. By combining GRACE with aircraft altimetry, we are developing more robust regional estimates of mass change and can make a better assessment of errors in each approach. We apply these methods to glaciers of the St.~Elias Mountains, home to approximately one-half of glaciers (by surface area) in Alaska and northwestern Canada. Most glaciers in this region receive abundant precipitation and terminate in lakes or at tidewater, and many have a large proportion of their surface area at low elevations, making them particularly sensitive to changes in climate. Our GRACE solutions show that this region had the highest rate of mass loss during 2003-2007, relative to all other regions in Alaska/northwestern Canada. During August 2007 we collected laser altimetry surface elevation data along flight paths last measured during August 2003 and, in some cases, September 2005. By calculating the difference between these elevations, and extrapolating to all glaciers in the region, we obtain the net contribution of this region to rising sea level. These new altimetry data are the first regional glacier mass change dataset to be collected concurrently with data from GRACE, and will provide an independent dataset for validation of GRACE estimates. Our updated assessment of glacier mass changes in the St.~Elias Mountains will provide new insights into the response of glaciers to regional climate changes.
DE: 0758 Remote sensing
DE: 0762 Mass balance (1218, 1223)
DE: 0776 Glaciology (1621, 1827, 1863)
DE: 1217 Time variable gravity (7223, 7230)
DE: 1621 Cryospheric change (0776)
SC: Cryosphere [C]
MN: 2007 Fall Meeting