Summer ice in the Antarctic is melting 10 times quicker than it was 600 years ago, with the most rapid melt occurring in the last 50 years, a joint Australian-British study showed Monday.

A research team from the Australian National University and the British Antarctic Survey drilled a 364-metre (1,194 feet) long ice core from James Ross Island in the continent’s north to measure past temperatures in the area.

Visible layers in the ice core indicated periods when summer snow on the ice cap thawed and then refroze.

By measuring the thickness of these melt layers, the scientists were able to examine how the history of melting compared with changes in temperature at the ice core site over the last 1,000 years.

“We found that the coolest conditions on the Antarctic peninsula and the lowest amount of summer melt occurred around 600 years ago,” said lead author Nerilie Abram of the ANU Research School of Earth Sciences.