[1] Imperial Coll London, Dept Earth Sci & Engn, London, England
[2] Univ Catholique Louvain, Dept Environm Sci & Land Use Planning, B-1348 Louvain, Belgium
[3] Delft Univ Technol, Fac Civil Engn & Appl Earth Sci, NL-2600 AA Delft, Netherlands
[4] Alfred Wegener Inst Polar & Marine Res, D-2850 Bremerhaven, Germany