Melting glacier released a 6.7 gigaton ‘megawave’

  • NASA studied Greenland’s hottest summers on record, 2010 and 2012
  • Found ice in Rink Glacier slid through the glacier’s interior in a gigantic wave
  • May increase the potential for sustained ice loss in Greenland 
  • Could have implications for the future rate of sea level rise

NASA has revealed a never before seen phenomenon that caused a ‘giant wave’ on a melting glacier. 

The wave – which occurred during the 2012 record melt year – traveled nearly 15 miles through the Rink Glacier in western Greenland over four months before reaching the sea, the researchers said. 

It was so big that it warped the solid Earth – a surge equivalent in mass to 18,000 Empire State Buildings. 

The study found that during Greenland's hottest summers on record, 2010 and 2012, the ice in Rink Glacier on the island's west coast slid through the glacier's interior in a gigantic wave

The study found that during Greenland’s hottest summers on record, 2010 and 2012, the ice in Rink Glacier on the island’s west coast slid through the glacier’s interior in a gigantic wave

THE RINK GLACIER 

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.

 

Scientists say it was ‘like a warmed freezer pop sliding out of its plastic casing’ and found 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.

‘It’s a gigantic mass,’ said Eric Larour, one of the study’s authors and a researcher at NASA’s Jet Propulsion Laboratory. 

‘It is able to bend the bedrock around it.’ 

This long pulse of mass loss, called a 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 by three scientists from NASA’s Jet Propulsion Laboratory in Pasadena, California, was the first to precisely track a glacier’s loss of mass from melting ice using the horizontal motion of a GPS sensor. 

They used data from a single sensor in the Greenland GPS Network (GNET), sited on bedrock next to Rink Glacier. 

A paper on the research is published online in the journal Geophysical Research Letters.

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 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 GLACIAL MEGAWAVE 

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. 


This animation shows a solitary wave passing through Rink Glacier, Greenland, in 2012, recorded by the motion of a GPS station (circle with arrow). Darker colors within the flow indicate mass loss, red colors show mass gain. The star marks the center of the wave

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.

‘We know for sure that the triggering mechanism was the surface melting of snow and ice, but we do not fully understand the complex array of processes that generate solitary waves,’ said JPL scientist Surendra Adhikari, who led the study.

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. 

Intense melting such as we saw in 2010 and 2012 is without precedent, but it represents the kind of behavior that we might expect in the future in a warming climate 

‘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.

The glacier gained mass from October through January as ice continued to move downstream to replace the lost mass. 

‘This systematic transport of ice in fall to midwinter had not been previously recognized,’ Adhikari emphasized.

‘Intense melting such as we saw in 2010 and 2012 is without precedent, but it represents the kind of behavior that we might expect in the future in a warming climate,’ Ivins added. 

‘We’re seeing an evolving system.’ 

 





Courtesy: Daily Mail Online

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