Greenland ice sheet melting at an unprecedented rate

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The melting rate for Greenland's ice sheet in the past two decades is five times higher than it was before the Industrial Revolution due to warmer summers, according to new research from the U.S. and the Netherlands.

The study, funded by the U.S. National Science Foundation, provides new evidence of climate change's impact on Arctic melting and global sea level rise. Previously, scientists tracked the shrinking size of Greenland ice sheets from satellites, with satellite data only tracing back to the late 1970s.

Meltwater canyon on the Greenland ice sheet. /VCG Photo

Meltwater streams cross the ice sheet. /VCG Photo

Meltwater filled crevasses, Greenland. /VCG Photo

Meltwater plume exiting an outlet glacier of west Greenland. /VCG Photo

Sea ice breaks up in Disko Bay, West Greenland. /VCG Photo

To go further back in time, scientists drilled ice cores from the ice sheet and an adjacent coastal ice cap to calculate the thickness and age of the melt layers directly. Basically, the thicker the melt layers are, the more melting occurred in that year.

Based on these ice core samples and satellite observations, researchers employ complex climate models to estimate how intensely the surface of ice sheets has melted over the past 350 years in central west Greenland.

Melt stream on the Greenland ice sheet. /VCG Photo

Ice-covered meltwater lake on the Greenland ice sheet. /VCG Photo

Ice cap on Disko Island, west Greenland, with the sea ice and iceberg-filled Disko Bay and the Greenland Ice Sheet in the distance. /VCG Photo

Meltwater canyon on the Greenland ice sheet. /VCG Photo

Exposed cliff of an ice cap in west Greenland. /VCG Photo

The result shows that the melting of Greenland's ice sheet began increasing in the mid-19th century, which correlates with the explosion in output from the Industrial Revolution. The melting rate has accelerated during the 20th and early 21st centuries.

Melting ice from Greenland is a key contributor to global sea level rise. Researchers say that over half of the water entering the ocean comes from runoff from melted snow and glacial ice atop the ice sheet. According to the study, Greenland ice sheet meltwater runoff has increased 30 percent since the 20th century.

If Greenland's mile-thick ice sheets completely melt, it can raise global sea levels over seven meters (23 feet). The global sea level rise could damage coastal cities in the coming years and make 40-50 percent of the global population who currently live in coastal areas lose their homes.

Iceberg in west Greenland. /VCG Photo

Scientists warn that a very small rise in temperature in recent years could cause an exponential increase in the ice sheet's melting rate. Considering that air temperatures in the Arctic are rising the fastest on Earth, global warming today means much than it did in the past.