Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, USA
University of British Columbia, Department of Earth and Ocean Sciences, 2329 West Mall, Vancouver, BC V6T 1Z4 Canada; Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
University of California Berkeley, Department of Earth and Planetary Science, 307 McCone Hall, Berkeley, CA 94720, USA
Carnegie Institution of Washington, Department of Terrestrial Magnetism, 5241 Broad Branch Road NW, Washington, DC 20015, USA