[1] Polar Sci Ctr, Seattle, WA 98105 USA
[2] Japan Agcy Marine Earth Sci & Technol, Inst Observsat Res Global Change, Yokosuka, Kanagawa 2370061, Japan
[3] Oregon State Univ, Coll Ocean & Atmospher Sci, Corvallis, OR 97331 USA
[4] Lamont Doherty Earth Observ, Palisades, NY 10964 USA