1. Lamont-Doherty
Earth Observatory, Columbia University, Palisades, New York 10964, United States
2. School
of Earth Sciences, University of Western Australia, 35 Stirling
Highway, Perth, West Australia 6009, Australia
3. Department
of Earth Sciences, Dartmouth College, Hanover, New Hampshire 03755, United States
4. Research
and Development Center, Cold Regions Research and Engineering Laboratory, 72 Lyme Road, Hanover, New Hampshire 03755, United States