How to

31 May 2017

Discovery of ‘Solitary Wave’ Phenomenon Looks like Bad News for Greenland’s Glaciers

The planet’s glaciers are in serious trouble, of that there is no doubt, and one of the regions in which this is most evident is the icy expanse of Greenland. Home to the second largest ice cap on Earth, beaten to the top spot only by Antarctica, the ultimate fate of Greenland and its glaciers will have a substantial impact upon the world as a whole, and as such understanding the mechanisms which influence the decline of these breathtaking geographical features is of vital importance.

A new NASA study has recently shone a spotlight upon the issue once more, drawing attention to an until-now-unknown phenomenon which could substantially shorten the predicted lifespan of such features. Known as a ‘solitary wave’, the discovery is both important and worrying.

NASA describes the solitary wave phenomenon as a ‘long pulse of mass loss’, in which the glacier’s interior moves below the surface at an increased rate, sliding out of the glacier much like “a warmed freezer pop sliding out of its plastic casing”.

The discovery was made through analysis of the Rink Glacier on Greenland’s west coast during Greenland’s warmest recorded summers in 2010 and 2012. The team of three scientists from NASA’s Jet Propulsion Laboratory in Pasadena, California made use of a GPS sensor sited on bedrock next to the Rink Glacier, one of many that make up the Greenland GPS Network (GNET), to track the glacier’s horizontal motion and resulting loss of mass.

It was found that while the Rink Glacier drained at a rate of approximately 11 billion tonnes per year during the early 2000s, this stepped up considerably during the hot summer of 2012 in particular, during which time it shed an additional 6.7 billion tonnes, amounting to a total of 17.7 billion tonnes of ice mass lost.
Img: NASA/JPL-Caltech
The speed at which the wave moved through the glacier during the months of June to September 2012 peaked well above the Rink Glacier’s usual pace of a couple kilometres per year, clocking in as high as 4 kilometres per month during the first 3 months before rising again up to 12 kilometres in September alone.

The reason as to why the discovery of such an important natural occurrence took so long is that on the surface, there is little visible evidence of anything happening, as co-author of the paper and renowned JPL scientist Eric Larour states, “You could literally be standing there and you would not see any indication of the wave. You would not see cracks or other unique surface features.”

A similar yet smaller wave was observed in 2010, although the researchers did not quantify its size and 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 which saw an occurrence of the solitary wave, there was more water held in the interior basin behind Rink Glacier than ever before. As 90% of the surface snow and ice began to melt, this meltwater is believed to have created temporary lakes which then drained through the glacier en route to the ocean, as co-author and JPL scientist Erik Ivins explains, “The water upstream probably had to carve new channels to drain. It was likely to be slow-moving and inefficient.”

Once these new channels were formed, the ice began to move at a vastly accelerated rate.

It is also stated that the water may have contributed to speed of the glacier’s movements in more ways than just the creation of these new flow channels; the large quantity of water also likely lubricated the base and sides of the glaciers, which allowed it to move at an increased pace.

From October through to January the glacier did begin to regain mass, as ice travelled downstream to replace that which was lost. According to Adhikari, “This systematic transport of ice in fall to midwinter had not been previously recognised.”

“Intense melting such as we saw in 2010 and 2012 is without precedent, but it represents the kind of behaviour that we might expect in the future in a warming climate,” Ivins added. “We're seeing an evolving system.”

Surprisingly, the GNET stations used to conduct this research are no longer maintained by any company, organisation or agency; the team were in fact investigating whether there were any scientific reasons to keep the network running at the time they spotted the Rink Glacier’s unusual activity. Ivins proudly states, “Boy, did we find one!”

Sam Bonson

Sam is an aspiring novelist with a passion for fantasy and crime thrillers. He is currently working as a content writer, journalist & editor in an attempt to expand his horizons.