Katja Bettina Matthes, GEOMAR Helmholtz Centre for Ocean Research, Ocean circulation and climate dynamics, Kiel, Germany, Wenjuan Huo, Helmholtz Centre for Ocean Research Kiel, Kiel, Germany, Annika Drews, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany and Tim Kruschke, SMHI - Swedish Meteorological and Hydrological Institute, Norrköping, Sweden