Nour-Eddine Omrani, University of Bergen and Bjerknes Centre, Geophysical Institute, Bergen, Norway, Noel S Keenlyside, Geophysical Institute, Juneau, Norway, Katja Matthes, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany, Davide Zanchettin, Max Planck Inst. for Meteorol., Hamburg, Germany and Johann Jungclaus, Max Planck Institute for Meteorology, Hamburg, Germany