Greenland’s ice sheet is melting faster than scientists previously estimated, according to a study released Wednesday in the journal Nature, with the loss believed to be 20% worse than previously reported.

Since 1985, Greenland’s ice sheet has lost approximately 5,091 square kilometers of ice researchers found using satellite imagery. Scientists said earlier estimates did not track melting at the edges of the ice sheets, known as calving, which measures ice breaking off at the terminus of a glacier.

Greenland’s ice sheet loses about 193 square kilometers of ice per year, researchers found.