A massive and surprising change is unfolding around Antarctica. Scientists have discovered that the Southern Ocean is getting saltier, and sea ice is melting at record speed, enough to match the size of Greenland.

A study published Monday in the Proceedings of the National Academy of Sciences found that increases in salinity in seawater near the surface could help explain some of the decrease in Antarctic sea ice that have been observed over the past decade, reversing a previous period of growth.