[1] Univ Michigan, Glaciochem & Isotope Geochem Lab, 1100 N Univ Ave, Ann Arbor, MI 48109 USA
[2] Ohio State Univ, Byrd Polar & Climate Res Ctr, 108 Scott Hall,1090 Carmack Rd, Columbus, OH 43210 USA
[3] Ohio State Univ, Mendenhall Lab 275, Sch Earth Sci, 125 South Oval Mall, Columbus, OH 43210 USA
[4] Univ Milano Bicocca, Disat, Piazza Sci 1, I-20126 Milan, Italy
[5] Vrije Univ Amsterdam, de Boelelaan 1085, NL-1081 HV Amsterdam, Netherlands
[6] Stiftung Alfred Wegener Inst Polar & Meeresforsch, Alten Hafen 26, D-27568 Bremerhaven, Germany