1. Department of Geosciences and Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, Pennsylvania 16802;
2. Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195
3. Courant Institute of Mathematical Sciences, New York University, New York, NY 10012
4. Antarctic Research Centre, Victoria University of Wellington, Wellington 6140, New Zealand
5. Mathematics and Geoscience, The Pennsylvania State University, DuBois, Pennsylvania 15801
6. Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20742
7. Cryospheric Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771