ICESat, CryoSat and PIOMAS sea ice thickness measurements in the Arctic. Figure (a) shows the 2003–07 average ICESat ice thickness for October/November and (b) the 2004–08 average for February/March. Figures (c) to (f) are measurements based on CryoSat data, for October/November 2010 (c), February/March 2011 (d), October/November 2011 (e) and February/March 2012 (f). The final two figures are based on PIOMAS measurements for October/November 2011 (g) and February/March 2012 (h).