1. Institute of Geology and Mineralogy University of Cologne Zülpicher Str. 49a Cologne D‐50674 Germany
2. Arctic and Antarctic Research Institute Bering Str. 38 St. Petersburg 199397 Russia
3. St. Petersburg State University Universitetskaya Nab. 7/9 St. Petersburg 199034 Russia
4. Institute of Geosciences University of Kiel Otto‐Hahn‐Platz 1 Kiel 24118 Germany
5. Institute of Geography University of Cologne Otto‐Fischer‐Str. 4 Cologne 50674 Germany
6. Herzen State Pedagogical University of Russia Moika 48 St. Petersburg 191186 Russia
7. Northern Water Problems Institute Karelian Research Centre of Russian Academy of Sciences Alexander Nevsky 50 Petrozavodsk 185030 Russia