Richard G Williams, University of Liverpool, Earth, Ocean and Ecological Sciences, Liverpool, L69, United Kingdom, Andrew Meijers, NERC British Antarctic Survey, Cambridge, United Kingdom, Vassil M Roussenov, University of Liverpool, Liverpool, United Kingdom, Anna Katavouta, National Oceanography Centre, Liverpool, United Kingdom, Paulo Ceppi, Imperial College London, Physics, London, United Kingdom, Jonathan Rosser, British Antarctic Service, Cambridge, United Kingdom and Pietro Salvi, ETH Zurich, Institute for Atmospheric and Climate Science, Zurich, Switzerland