Category Archives: Greenland

Something strange is happening to Greenland’s ice sheet

What should be like a snowcone is becoming more like a popsicle, speeding up the runoff from the melting ice sheet.

When the remnants of Europe’s second summertime heat wave migrated over Greenland in late July, more than half of the ice sheet’s surface started melting for the first time since 2012. A study published Wednesday in Nature shows that mega-melts like that one, which are being amplified by climate change, aren’t just causing Greenland to shed billions of tons of ice. They’re causing the remaining ice to become denser.

“Ice slabs”—solid planks of ice that can span hundreds of square miles and grow to be 50 feet thick—are spreading across the porous, air pocket-filled surface of the Greenland ice sheet as it melts and refreezes more often. From 2001 to 2014, the slabs expanded in area by about 25,000 square miles, forming an impermeable barrier the size of West Virginia that prevents meltwater from trickling down through the ice. Instead, the meltwater becomes runoff that flows overland, eventually making its way out to sea.

As the ice slabs continue to spread, the study’s authors predict more and more of Greenland’s surface will become a “runoff zone,” boosting the ice sheet’s contribution to global sea level rise and, perhaps, causing unexpected changes.

It’s easy to think of Greenland as a solid, impenetrable hunk of ice. But in reality about 80 percent of the ice sheet’s surface is like a snowcone: A dusting of fresh snowfall covers a thick layer of old snow, called firn, that’s slowly being compressed into glacier ice but still contains plenty of air pockets. When the top of this snow cone melts in the summer, liquid water percolates down into the firn, which soaks it up like a 100-foot-thick sponge.

MacFerrin and his colleagues got their first hint that the firn may be losing its absorbency in the spring of 2012, when they were drilling boreholes through the firn in southwest Greenland. They started finding dense, compacted layers of ice in core after core, just below the seasonal snow layer. It was, MacFerrin says, as if a “turtle shell” had formed over the firn.

MacFerrin and his colleagues immediately wondered whether that shell might be preventing meltwater from percolating into the firn.

“That was May of 2012,” MacFerrin says. “And July was this record-breaking melt year, and we got our answer very quickly.”

That summer, for the first time on record, meltwater from this part of Greenland visibly started to flow away as runoff.

Realizing they had witnessed something significant, the researchers set about drilling more cores over a larger region to see how extensive the ice shell was. They discovered that it spanned a transect 25 miles long and was having widespread effects on local hydrology.

Those findings, published in 2016 in Nature Climate Change, were the springboard for the new study. Using radar data from NASA’s IceBridge airborne campaign, as well as ground-based surveys, MacFerrin and his colleagues have now created a first-of-its-kind map of ice slabs across the entire surface of Greenland.

Based on modelling results, the researchers think the shell began to form and spread widely in the early 2000s. As of 2014, it covered some 4 percent of Greenland’s surface, according to the new analysis. Every summer that extensive melting occurs, it gets thicker and spreads inland to colder, higher ground.

“Every handful of years, these big melt summers are doing a number on the firn,” MacFerrin says. “That’s causing this whole process to grow inland pretty quickly.”

This photo is a segment of a firn core, essentially a baby ice slab that eventually will grow into a meters-thick slab of ice.

PHOTOGRAPH BY DR. KAREN ALLEY

Sea level rise and unexpected consequences 

Ice slabs have already caused Greenland’s runoff zone to expand by about 26 percent, according to the new study. So far the additional runoff has only added about a millimeter to global sea levels. Greenland now contributes a little under a millimeter per year to rising sea levels, through a combination of icebergs breaking off glaciers and melt occurring at the surface and base of the ice sheet.

But if Greenland’s surface hardens more, runoff could rise dramatically. Under a worst-case scenario where carbon emissions continue to climb until the end of the century, the researchers calculated that ice slab proliferation could add up to 3 inches of sea level rise by 2100, boosting the ice sheet’s overall sea level rise contribution by nearly a third. In both a middle-of-the-road scenario where emissions peak by mid-century and the high emissions one, the amount of runoff from Greenland’s interior roughly doubles by century’s end.

But more runoff is only one potential consequence of the transformation taking place in Greenland’s ice. Kristin Poinar, a glaciologist at the University of Buffalo who wasn’t involved in the study, pointed out that slabs of solid ice aren’t nearly as reflective as bright white snowfall.

“And so, if we start getting these ice slabs forming near the ice sheet’s surface, it could potentially…cause the ice sheet to absorb more solar radiation and warm up,” she says. “And that would create more ice slabs.”

And runoff from ice slabs doesn’t have to flow into the ocean, said Indrani Das, a glaciologist at Columbia University who wasn’t involved in the study. She worries about how it could seep into the large crevasses that exist at lower elevations on the ice sheet. From there, the runoff could, potentially, flow all the way down to bedrock, lubricating the zone where the ice makes contact with it.

“That could make the ice sheet flow faster,” Das says, which could cause glaciers to spill their contents into the ocean more quickly, like ice cream sliding off a piece of cake.

To Poinar, the most significant contribution of the new study is that it will allow scientists to improve their projections of future sea level rise, giving coastal communities the information they need to prepare. At the same time, the study highlights the fact that the more carbon we spew into the atmosphere, the more we’re likely to transform Earth’s northern ice sheet in insidious and unexpected ways. And that could have consequences that are difficult to anticipate.

“We have never observed an ice sheet behaving this way before,” Poinar says. “It’s unprecedented in human scientific history.”

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    Benicia: Getting ready to retreat from coastline properties?

    By Roger Straw, August 22, 2019

    What’s to do about the possible 6-foot sea level rise along our Carquinez coast?

    As glaciers melt, they release significant volumes of organic carbon, with unknown impacts on marine life. CREDIT: ISTOCK

    Actionable sea level rise is scientific consensus.  This from the National Oceanic and Atmospheric Administration (NOAA)’s Climate.gov website:

    NOAA scientists conducted a review of the research on global sea level rise projections, and concluded that there is very high confidence (greater than 90% chance) that global mean sea level will rise at least 8 inches (0.2 meter) but no more than 6.6 feet (2.0 meters) by 2100.

    Some researchers have predicted worse.  See What Does U.S. Look Like With 10 Feet of Sea Level Rise? where huge numbers of homeowners would be affected:

    Cities with the Most Population on Affected Land
    CITY POPULATION
    1.  New York City 703,000
    2.  New Orleans 342,000
    3.  Miami 275,000
    4.  Hialeah, FL 224,000
    5.  Virginia Beach 195,000
    6.  Fort Lauderdale 160,000
    7.  Norfolk 157,000
    8.  Stockton, CA
    (Sacramento-San Joaquin Delta)
    142,000
    9.  Metairie, LA 138,000
    10.  Hollywood, FL 126,000
    All cities

    An interactive map by ClimateCentral.org can be adjusted to show Benicia at various levels of sea level rise.  Here we are at 6 feet:

    Click on the image to enlarge. Better yet, go to ss2.climatecentral.org/#16/38.0476/-122.1575 to  scan nearby locations. Mare Island and State Route 37 are particularly of interest. The map will take you anywhere in the world.

    The odds of reaching a 6 foot rise are good, given the slow pace of corporate and government action to slow global warming.

    There is one single lifetime – 81 years – between now and the year 2100.  What should Benicia city leaders be doing in anticipation of a 5 or 6 foot inundation of our shores?  What should homeowners on Semple Crossing and everyone in lower downtown – all the way up to and including Rancho Benicia on East H Street – be doing?

    I don’t have answers.  But it’s a very real question….

    The breaking news this week is about Greenland’s temps soaring 40 degrees above normal.  Benicia: we need to wake – sea level rise is real, and will surely affect us here in our beautiful coastal city.

    ‘We Should Be Retreating Already From the Coastline,’ Scientist Suggests After Finding Warm Waters Below Greenland

    EcoWatch Jordan Davidson, Aug. 20, 2019
    The Eqip Sermia Glacier is seen behind a moraine left exposed by the glacier’s retreat during unseasonably warm weather on Aug. 1 at Eqip Sermia, Greenland. Sean Gallup / Getty Images

    Andrew Yang’s assertion that people move away from the coast at the last Democratic debate is the completely rational and correct choice for NASA scientists in Greenland.

    “There is enough ice in Greenland to raise the sea levels by 7.5 meters, that’s about 25 feet, an enormous volume of ice, and that would be devastating to coastlines all around the planet,” said Josh Willis, a NASA oceanographer, to CNN. “We should be retreating already from the coastline if we are looking at many meters [lost] in the next century or two.”

    Willis and his research team at NASA’s Ocean Melting Greenland have been seeing some alarming patterns as they jet around the island’s coastline since heat waves bore down on the U.S. and Europe at the end of July, as CNN reported. Not only is the surface temperature warmer, turning Greenland into a slush-filled mess, but the ocean temperature deep under the water is also rising. The warming water eats away at the foundation of the glaciers, meaning Greenland’s massive ice sheet is getting weaker at the top and the bottom, which spells trouble for the entire world.

    “Greenland has impacts all around the planet. A billion tons of ice lost here raises sea levels in Australia, in Southeast Asia, in the United States, in Europe,” said Willis to CNN. “We are all connected by the same ocean.”

    The scientists looking at the ice and waters found a large opening of water near Helheim glacier, a huge 4-mile glacier on Greenland’s east coast, that had warm water along its entire depth, more than 2,000 feet below the surface, as CNN reported.

    “It’s very rare anywhere on the planet to see 700 meters of no temperature variation, normally we find colder waters in the upper hundred meters or so, but right in front of the glacier it’s warm all the way up,” said Ian Fenty, a climate scientist at NASA, to CNN. “These warm waters now are able to be in direct contact with the ice over its entire face, supercharging the melting.”

    Helheim has made news the past two summers. Two years ago it lost a huge 2-mile piece. Last summer a chunk the size of lower Manhattan broke off and was captured on video, as National Geographic reported.

    This year the glacier has continued to melt.

    “It retreats by many meters per day, it’s tens of meters per day. You can probably set your iPhone on timelapse and actually see it go by,” said Willis to CNN.

    The ice in Greenland started the summer weak. There was little snowfall this past winter to reinforce the ice or to absorb the sunlight in the peak of summer, when the sun never fully goes down. Fresh snow stays bright and reflective, which bounces away solar radiation. Older snow is less reflective and absorbs the sun’s heat. When the first heat wave hit in June, 45 percent of Greenland’s ice sheet was ready to melt, according to National Geographic.

    Arctic ice like Greenland’s is also vital to removing carbon from the atmosphere, according to a study in the journal Polar Biology. The calcium carbonate crystals that make up sea ice trap carbon dioxide in a cold brine. When the sea ice melts, it drops that carbon dioxide into the ocean where it binds to algae, which stops it from circulating around the atmosphere.

    As sea ice decreases, less carbon will be removed from the atmosphere. Plus, the melting ice will raise sea levels. Glaciers like Helheim are big enough to make global sea levels rise by one millimeter in just one month, which concerns scientists, as CNN reported.

     

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