Towards a re-assessment of the surface mass balance of the Greenland ice sheet M. van den Broeke, J. Ettema, W. J. van de Berg and E. van Meijgaard EPJ Web of Conferences, 1 (2009) 171-176 Published online: 25 February 2009 DOI: 10.1140/epjconf/e2009-00918-7