As COP 23 kicks off, a new map of Greenland shows glaciers...

As COP 23 kicks off, a new map of Greenland shows glaciers are at a great risk

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Left: Greenland topography color-coded from 4,900 feet (1,500 meters) below sea level (dark blue) to 4,900 feet above sea level (brown). Right: regions below sea level connected to the ocean, either shallower than 600 feet (200 meters, light pink); between 600 and 1,000 feet (300 meters, dark pink); or continuously deeper than 1,000 feet below sea level (dark red).
Courtesy: UCI

A new map of Greenland’s coastal sea floor and the surface beneath the sheets of ice – released by NASA – shows that glaciers there are melting at a very fast pace and the number of glaciers that are at an alarming risk of melting are 4 times more than previously estimated. This map has released just ahead of COP 23 summit at Bonn, Germany, which will begin on 6th November and end on 17th November. Implementation of Paris Agreement will be the key agenda at COP 23. The principal goal of the Paris Agreement is combating climate change and endeavoring to reduce global rise in temperature to less than 2 degree Celsius by the end of this century. Last year, when US President Donald Trump pulled out of COP22, it was a shocking setback that risked derailing the progress made in climate change goals and reducing carbon emissions.

Comprehensive mapping for the first time

Scientists and researchers at the University of California at Irvine (UCI), NASA and 30 other institutions have created the most accurate high-resolution maps ever made of Greenland’s bedrock and coastal seafloor.  The map uses data from NASA’s Ocean Melting Greenland (OMG) campaign, alongside other data that was fetched.

Mathieu Morlighem, lead author at UCI, had painstakingly demonstrated in an earlier paper that data from OMG’s survey of the shape and depth of the seafloor in Greenland’s fjords improved scientists’ understanding not only of the coastline, but of the inland bedrock underneath the glacial surface that flow into the ocean. This is because the bathymetry where a glacier meets the ocean impedes the possibilities for the shape of bedrock farther upstream.

More in proximity to the shoreline, more valuable the bathymetry data are for understanding on-shore topography, Morlighem said. “What made OMG unique compared to other campaigns is that they got right into the fjords, as close as possible to the glacier fronts. That’s a big help for bedrock mapping.”

Moreover, the OMG campaign surveyed large sections of the Greenland coast for the very first time. In fjords, for which there are no data, it’s very difficult to reckon how deep the glaciers extend below sea level.

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Greenland coastline before and after the inclusion of OMG data. Courtesy: UCI

The OMG data are only one of many datasets Morlighem and his team used in the ice sheet mapper, which is named BedMachine. Another exhaustive source is NASA’s Operation IceBridge airborne surveys. IceBridge measures the ice sheet thickness directly along a plane’s flight path, creating a set of long, narrow strips of data rather than a complete map of the ice sheet. Other than NASA, 40 other collaborators also contributed various types of survey data on different parts of Greenland.

The baleful risk of glacial melting

No survey — not even OMG — covers every glacier on Greenland’s long, convoluted and difficult to track coastline.  Deducing the bed topography in lesser analyzed areas, BedMachine averages between existing data points using physical principles such as the conservation of mass.

The new maps reveals that two to four times more oceanfront glaciers extend deeper than 600 feet (200 meters) below sea level than earlier maps showed.

That’s certainly a bad news!

Top 600 feet of water around Greenland comes from the Arctic and is comparatively very cold. The water below it comes from farther south and is 6 to 8 degrees Fahrenheit (3 to 4 degrees Celsius) warmer than the water above.

Deeper-seated glaciers are exposed to this warmer water, which melts them more rapidly.

Morlighem’s team used the maps to gain more insight on their estimate of Greenland’s total volume of ice and its potential to add to global sea level rise, if the ice were to melt completely and vanish, which is not expected to occur within the next few hundred years even by the most conservative estimates. The new estimate is higher by 2.76 inches (7 centimeters) for a total of 24.34 feet (7.42 meters).

OMG Principal Investigator Josh Willis of JPL said, “These results suggest that Greenland’s ice is more threatened by changing climate than we had anticipated.”

The five-year OMG campaign completed its second annual set of airborne surveys to meticulously measure – for the first time – the amount that warm water around the island is contributing to the loss of the Greenland ice sheet. Besides the one-time bathymetry survey, OMG is collecting annual measurements of the changing height of the ice sheet and the ocean temperature and salinity in more than 200 fjord locations. Morlighem is looking forward to further improve BedMachine’s maps with data from the aerial surveys.

The maps and related research are included a paper titled “BedMachine v3: Complete bed topography and ocean bathymetry mapping of Greenland from multi-beam echo sounding combined with mass conservation”