Satellite records show a decline in ice extent over more than three decades, with a record minimum in September 2012. Results from the Pan-Arctic Ice-Ocean Modelling and Assimilation system (PIOMAS) suggest that the decline in extent has been accompanied by a decline in volume, but this has not been confirmed by data. Using new data from the European Space Agency CryoSat-2 (CS-2) mission, validated with in situ data, we generate estimates of ice volume for the winters of 2010/11 and 2011/12. We compare these data with current estimates from PIOMAS and earlier (2003-8) estimates from the National Aeronautics and Space Administration ICESat mission. Between the ICESat and CryoSat-2 periods, the autumn volume declined by 4291 km³ and the winter volume by 1479 km³. This exceeds the decline in ice volume in the central Arctic from the PIOMAS model of 2644 km³ in the autumn, but is less than the 2091 km³ in winter, between the two time periods. Key Points CryoSat-2 can provide accurate pan-Arctic measurements of sea ice thickness The data show a decrease in sea ice volume over the last decade This is the first observational evidence to confirm the decline from models ©2013. American Geophysical Union. All Rights Reserved.