Greenland ice river becomes world's fastest flowing glacier

A massive glacier in Greenland - which is believed to have produced the iceberg that sank the Titanic - has become the fastest-flowing glacier in the world, according to a new study.
The Jakobshavn Glacier is moving ice from the Greenland ice sheet into the ocean at a speed that appears to be the fastest ever recorded, researchers said.
Researchers from the University of Washington and the German Space Agency (DLR) measured the dramatic speeds of the fast-flowing glacier in 2012 and 2013.
"We are now seeing summer speeds more than 4 times what they were in the 1990s on a glacier which at that time was believed to be one of the fastest, if not the fastest, glacier in Greenland," said Ian Joughin, from the University of Washington and lead-author of the study.

In the summer of 2012, the glacier reached a record speed of more than 17 km per year, or over 46 m per day.
These flow rates are unprecedented: they appear to be the fastest ever recorded for any glacier or ice stream in Greenland or Antarctica, the researchers said.

They noted that summer speeds are temporary, with the glacier flowing more slowly over the winter months. But even the annually averaged speedup over the past couple of years is nearly three times what it was in the 1990s.
This speedup means that the glacier is adding more and more ice to the ocean, contributing to sea-level rise.

"We know that from 2000 to 2010 this glacier alone increased sea level by about 1 mm. With the additional speed it likely will contribute a bit more than this over the next decade," said Joughin.
Jakobshavn glacier, which is widely believed to be the glacier that produced the large iceberg that sank the Titanic liner in 1912, drains the Greenland ice sheet into a deep ocean fjord on the coast of the island.
At its calving front, where the glacier effectively ends as it breaks off into icebergs, some of the ice melts while the rest is pushed out, floating into the ocean.

As the Arctic region warms, Greenland glaciers have been thinning and calving icebergs further and further inland.
This means that, even though the glacier is flowing towards the coast and carrying more ice into the ocean, its calving front is actually retreating.
In 2012 and 2013, the front retreated more than a kilometre further inland than in previous summers.
The calving front of the glacier is now located in a deeper area of the fjord, where the underlying rock bed is about 1,300 metres below sea level, which the scientists said explains the record speeds it has achieved.
"As the glacier's calving front retreats into deeper regions, it loses ice - the ice in front that is holding back the flow - causing it to speed up," Joughin said.

The research was published in The Cryosphere, a journal of the European Geosciences Union (EGU).