University of British Columbia, Earth and Ocean Sciences 6339 Stores RD, Vancouver, BC V6T1Z4 Canada
University of British Columbia, Earth and Ocean Sciences 6339 Stores RD, Vancouver, BC V6T1Z4 Canada; Scripps Institution of Oceanography, Institute of Geophysics and Planetary Physics University of California, San DIego, San DIego, CA 92093-0225, USA
University of California, Los Angeles, Earth and Space Sciences and the Institute of Geophysics and Planetary Physics, Los ANgeles, CA 90095, USA