A new European Space Agency (ESA) study has shown that Arctic sea ice has declined significantly since 2003.

The study, published recently in the journal Geophysical Research Letters, has confirmed that Arctic ice volume is declining, rather than just sea ice coverage. The paper shows that the ice has declined by (36%) during the fall months and 9% during winter since 2003. The decline in sea ice during summer, though, was shown to be the greatest.

“The data reveal that thick sea ice has disappeared from a region to the north of Greenland, the Canadian Archipelago and to the northeast of Svalbard,” said Katharine Giles, co-author of the study and a researcher at the Centre for Polar Observation and Modelling (CPOM) in the U.K.

The data used in the study was collected using the NASA’s ICESat satellite and the ESA’s CryoSat satellite, which uses its high-resolution radar altimeter to fire microwave pulses at the arctic. The pulses bounce off of both the surface ice and the water below, giving researchers a measurement with which to estimate volume.

“Other satellites have already shown drops in the area covered by Arctic sea ice as the climate has warmed, but CryoSat allows scientists to estimate the volume of sea ice – a much more accurate indicator of the changes taking place in the Arctic,” said Tommaso Parrinello, CryoSat mission manager.