1. Applied Physics Laboratory, University of Washington, 1013 Northeast 40th Street, Seattle, Washington 98105, USA
2. Department of Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA
3. University of New Hampshire, Center for Coastal and Ocean Mapping, 24 Colovos Road, Durham, New Hampshire 03824, USA
4. British Antarctic Survey, High Cross Madingley Road, Cambridge, CB3 0ET, United Kingdom