1. International Arctic Research Center and College of Natural Science and Mathematics, University of Alaska Fairbanks, Fairbanks, AK 99775, USA.
2. Institute of Marine Research, Bergen, Norway.
3. International Arctic Research Center, University of Alaska Fairbanks, Fairbanks, AK 99775, USA.
4. Geophysical Institute and College of Natural Science and Mathematics, University of Alaska Fairbanks, Fairbanks, AK 99775, USA.
5. Woodwell Climate Research Center, Falmouth, MA 02540, USA.
6. Alfred-Wegener-Institute, Helmholtz Centre for Polar and Marine Research, D-27570 Bremerhaven, Germany.
7. Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, WA 98105, USA.
8. Bjerknes Centre for Climate Research, Bergen, Norway.