Greenland is losing ice seven times faster than in the 1990s, according to a study published in the journal Nature.
"As a rule of thumb, for every centimetre rise in global sea level another six million people are exposed to coastal flooding around the planet," said one of the study authors Andrew Shepherd, Professor at University of Leeds in Britain.
"On current trends, Greenland ice melting will cause 100 million people to be flooded each year by the end of the century, so 400 million in total due to all sea level rise," Shepherd said.
For the study, a team of 96 polar scientists from 50 international organisations combined 26 separate surveys to compute changes in the mass of Greenland's ice sheet between 1992 and 2018.
Altogether, data from 11 different satellite missions were used, including measurements of the ice sheet's changing volume, flow and gravity.
The findings showed that Greenland has lost 3.8 trillion tonnes of ice since 1992 enough to push global sea levels up by 10.6 millimetres.
In 2013, the Intergovernmental Panel on Climate Change (IPCC) predicted that global sea levels will rise by 60 centimetres by 2100, putting 360 million people at risk of annual coastal flooding.
But this new study shows that Greenland's ice losses are rising faster than expected and are instead tracking the IPCC's high-end climate warming scenario, which predicts seven centimetres more.
So 40 million more people are likely to be exposed to coastal flooding by 2100 than earlier projected.
"These are not unlikely events or small impacts; they are happening and will be devastating for coastal communities," Shepherd said.
The team also used regional climate models to show that half of the ice losses were due to surface melting as air temperatures have risen.
The other half has been due to increased glacier flow, triggered by rising ocean temperatures.
Ice losses peaked at 335 billion tonnes per year in 2011 - ten times the rate of the 1990s - during a period of intense surface melting.
( With inputs from IANS )