Scientists researching the vast Greenland ice sheet say the melting in the northern hemisphere's summer has been one of the most severe on record.
Climate change, they say, is accelerating the rate of melting - and the effects will be felt far beyond the shores of the autonomous Danish territory.
Greenland has lost enough sea ice this year alone to raise the global sea level by more than one millimetre, including one glacier which thinned as much as 100 metres since 2004, the BBC reports.
If the entire ice sheet - seven times the size of the UK and up to 2-3 kilometres thick – were to melt, it would raise sea levels by up to 7 metres worldwide. The sea level rise could have catastrophic implications for millions of people living in low-lying areas, including Bangladesh. If the melting accelerates, Florida and many other areas will also be affected this century.
Geological Survey of Denmark and Greenland's Dr Jason Box, one of the scientists studying the ice sheet, said understanding more of the consequences is "actually keeping me awake at night".
"I realise the significance of this place around the world and the livelihoods that are already affected by sea level rise," he said.
Greenland is expected to lose at least 450 billion tonnes of ice this year, in line with 2012's figures, with some researchers suggesting it could raise sea levels by up to two millimetres.