1. Institute of Arctic and Alpine Research, UCB 450, University of Colorado at Boulder, Boulder, CO 80309–0450, USA.
2. Department of Physical Geography and Quaternary Geology, Stockholm University, SE-1061, Stockholm, Sweden.
3. Department of Atmospheric and Oceanic Sciences, UCB 311, University of Colorado at Boulder, Boulder, CO 80309–0311, USA.
4. Geophysical Institute, University of Alaska-Fairbanks, Fairbanks, AK 99775–7320, USA.
5. Department of Geological Sciences, UBC 399, University of Colorado at Boulder, Boulder, CO 80309–0399, USA.