1. Department of Earth and Environmental Science, College of Arts and Sciences, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
2. Marine Mammal Laboratory, Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration (NOAA), Seattle, Washington 98115, USA
3. Department of Physics, College of Arts and Sciences, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
4. Department of Mathematics, College of Arts and Sciences, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
5. Wharton School, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
6. Cooperative Institute for Climate, Ocean and Ecosystem Studies, University of Washington, Seattle, Washington 98195-5672, USA
7. Department of Philosophy, College of Arts and Sciences, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA