1. Department of Geological Sciences; Brigham Young University; Provo Utah USA
2. Cryospheric Sciences Laboratory; NASA Goddard Space Flight Center; Greenbelt Maryland USA
3. University of Utah; Department of Geography; Salt Lake City Utah USA
4. Center for Ice and Climate, Niels Bohr Institute; University of Copenhagen; Copenhagen Denmark
5. Department of Earth and Space Sciences; University of Washington; Seattle Washington USA