Sam Jaccard, University of Bern, Institute of Geological Sciences and Oeschger Centre for Climate Change Research, Bern, Switzerland, Adam Patrik Hasenfratz, ETH Swiss Federal Institute of Technology Zurich, Zurich, Switzerland, Julia Gottschalk, Lamont -Doherty Earth Observatory, Palisades, United States, Alfredo Martinez-Garcia, Max Plank Institut for Chemistry, Mainz, Germany and Gerald H Haug, Max Planck Institute for Chemistry, Mainz, Germany