NASA study on hottest summers in Greenland churned out a new discovery and it's worrying!

Rink Glacier in western Greenland, with a meltwater lake visible center. (Image courtesy: NASA/OIB)

New Delhi: Along with providing us with numerous insights into the working of the universe, US space agency NASA has time and again forewarned us of potential dangers like asteroids buzzing past the Earth, hurricanes and storms and most importantly, climate change.

With the discourse on global warming and climate change taking over a larger domain in the last few years, its rapidly growing effects have raised questions on Earth's habitability in the future.

Just last month, NASA's IceBridge mission acquainted us with the first photographs of a new, ginormous crack in Greenland's enormous Petermann Glacier, which sent out worrying signals regarding the glacier's sustenance.

Now, scientists at NASA have drawn attention towards another point of concern that has come forward in Greenland again. As per a study, during 2010 and 2012 – the hottest summers of Greenland on record – the ice in Rink Glacier on the island's west coast didn't just melt faster than usual, it slid through the glacier's interior in a gigantic wave, like a warmed freezer pop sliding out of its plastic casing.

The wave persisted for four months, with ice from upstream continuing to move down to replace the missing mass for at least four more months.

This solitary wave is a new discovery that may increase the potential for sustained ice loss in Greenland as the climate continues to warm, with implications for the future rate of sea level rise.

The study was conducted by three scientists – including an Indian-origin one who led the study – from NASA's Jet Propulsion Laboratory in Pasadena, California, and was the first to precisely track a glacier's loss of mass from melting ice using the horizontal motion of a GPS sensor.

Using data from a single sensor in the Greenland GPS Network (GNET), sited on bedrock next to Rink Glacier, the research is published online in the journal Geophysical Research Letters.

According to a NASA report, Rink is one of Greenland's major outlets to the ocean, draining about 11 billion tons (gigatons) of ice per year in the early 2000s – roughly the weight of 30,000 Empire State Buildings. In the intensely hot summer of 2012, however, it lost an additional 6.7 gigatons of mass in the form of a solitary wave. Previously observed melting processes can't explain that much mass loss.

The wave moved through the flowing glacier during the months of June through September at a speed of about 2.5 miles (4 kilometers) a month for the first three months, increasing to 7.5 miles (12 kilometers) during September. The amount of mass in motion was 1.7 gigatons, plus or minus about half a gigaton, per month. Rink Glacier typically flows at a speed of a mile or two (a few kilometers) a year.

The wave could not have been detected by the usual methods of monitoring Greenland's ice loss, such as measuring the thinning of glaciers with airborne radar. "You could literally be standing there and you would not see any indication of the wave," said JPL scientist Eric Larour, a coauthor of the new paper. "You would not see cracks or other unique surface features."

The researchers saw the same wave pattern in the GPS data for 2010, the second hottest summer on record in Greenland. Although they did not quantify the exact size and speed of the 2010 wave, the patterns of motion in the GPS data indicate that it must have been smaller than the 2012 wave but similar in speed.

During the two summers when solitary waves occurred, the surface snowpack and ice of the huge basin in Greenland's interior behind Rink Glacier held more water than ever before. In 2012, more than 95 percent of the surface snow and ice was melting. Meltwater may create temporary lakes and rivers that quickly drain through the ice and flow to the ocean. "The water upstream probably had to carve new channels to drain," explained coauthor Erik Ivins of JPL. "It was likely to be slow-moving and inefficient." Once the water had formed pathways to the base of the glacier, the wave of intense loss began.

The scientists theorize that previously known processes combined to make the mass move so quickly. The huge volume of water lubricated the base of the glacier, allowing it to move more rapidly, and softened the side margins where the flowing glacier meets rock or stationary ice. These changes allowed the ice to slide downstream so fast that ice farther inland couldn't keep up, NASA reported.