'Like ice cream sliding off a piece of cake,' Greenland ice cap melts in a new and disturbing way.

“We have never observed an ice sheet behaving this way before. It’s unprecedented in human scientific history.” - Kristin Poinar, Glaciologist, University of Buffalo

Greenland is, for the most part, a very moist environment (with the exception of northern Greenland which until recently had been a dry environment).

The ice sheet works like a sponge absorbing the meltwater of Summer. Now the slushie has turned into a popsicle. Massive ice slabs have formed that prevents percolation into the slushy layers of snow known as firn. This process is worsening runoff into the sea (as well as a lack of reflectivity of solar heat back to space).

Madeleine Stone writes in National Geographic:

When the remnants of Europe’s second summertime heatwave 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 is being amplified by climate change, aren’t just causing Greenland to shed billions of tonnes 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 15 metres 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 64,750 square kilometres, 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.

x

Holy cromboly : 4 Celsius warming in 60 years is 0.7 C per decade or 7 C per century!! By contrast the last great global warming during deglaciation was about 5 C in 10,000 years or 0.05 C per century. Starting 14k BP sea levels rose a foot a decade for 400 years. Uh oh. 😲 https://t.co/M7JM8UjUF9

— Scott Denning (@airscottdenning) October 2, 2019

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.

“We're watching an ice sheet rapidly transform its state in front of our eyes, which is terrifying,” says lead study author Mike MacFerrin, a glaciologist at the University of Colorado, Boulder.

x

As a result, the relative contribution of the North to the total Greenland ice sheet runoff increased substantially [3/n] pic.twitter.com/ycpxm5kPaV

— Stef Lhermitte (@StefLhermitte) September 4, 2019

Stone continues noting that increased runoff is not the only consequence of the phenomenon. 

“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.

x

In the North, these clouds act as a blanket that enhances warming and triggers an early melting of the shallow snow cover. Since N-Greenland is dry with only little snowfall in winter, this results darker ice that absorbs more sunlight, amplifying the melt. [8/n] pic.twitter.com/SYpqq0JnuE

— Stef Lhermitte (@StefLhermitte) September 4, 2019

Bob Berwyn of Inside Climate News writes:

To understand how the growing ice slabs affect runoff, it's helpful to know that the Greenland Ice Sheet has three zones.

In the coastal melting zone, snow that falls in winter melts away completely, exposing darker ice that melts quickly during warm summer weather. High on the ice sheet is the permanent dry snow and ice zone, where there has been little melting, at least up to now.

Some of the ice slabs have thickened from 5 meters to 7 meters in just five years, and they are expanding inland.

The thick layers prevented water from percolating down, and so the scientists found slush fields and runoff channels on the surface that sent torrents of water rushing toward the ocean.

x

Greenland sharks are known to frequent the dark waters of the Arctic—but they're rarely caught on camera pic.twitter.com/s8S7tzSjpc

— National Geographic (@NatGeo) September 30, 2019

"Up until recently, nobody was paying attention to the cold slow moving ice in the interior, but now it's waking up, turning into warm wet ice very quickly," MacFerrin said. "These interior regions of Greenland didn't use to run off, so you didn't have to worry about them in terms of sea level rise."

The entire Arctic system, from its thawing permafrost to its diminished sea ice, is in a state of transition as global temperatures rise, said Mark Serreze, director of the National Snow and Ice Data Center.

"These ice slabs are not the sort of thing we were thinking about 20-30 years ago. Basically, the ice slabs are making the runoff process more efficient. Every time we look, we see changes that suggest more rapid melting of the Greenland ice sheet than we thought 20 years ago."

x xYouTube Video The ~9 km wide Spalte Glacier is a tributary of the 79 Glacier which today (2016) has the Arctic’s largest ice shelf. The ice shelf forms the end of North-East Greenland Ice Stream, the only Greenland ice stream clearly reaching the highest elevations.

Professor Jason Box writes in the EGU Blog about several of the victims of the 2019 melt season in the Arctic. One of which is a significant calving event at Spalte Glacier. Box notes that the Manhattan size chunk of ice that emptied into Dijmphna Sound had cracked during the 2015-2016 melt season, the iceberg finally detached this summer.  Anytime a significant chunk of ice breaks away from the part of the glacier that floats in the ocean it will eliminate any resistance that it had provided to slow down the land ice from advancing.

The loss of sea ice has multiple impacts on the climate and cryosphere. When the bright, white sea ice melts, it exposes the darker ocean surface. As the dark ocean surface has a lower albedo (is darker) than sea ice, more sunlight is absorbed, further warming the area. This is called Arctic Amplification (see this post). Sea ice loss can also impact the Greenland ice sheet! A loss of sea ice near the coast of Greenland can cause glaciers to calve (large chunks break away) into the ocean when the pressure of the sea ice is removed. Spalte glacier, a tributary of the larger 79°N glacier in the northeast of Greenland, lost an area the size of Manhattan this summer. The whole northeast region had reduced sea-ice cover throughout summer.

x

The northern branch of 79-fjord glacier (Spalte glacier) is almost detached from the main glacier. Have a look at the animated gif. pic.twitter.com/tUMXfbr0n1

— PROMICE (@PromiceGL) August 30, 2019

Summer air temperature records at all 11 Danish Meteorological Institute stations around Greenland are correlated with glacier front area change… in warm summers, more ice area is lost. At 4 of the 11 sites, the confidence in that correlation is above 95%. At 7 of the 11 sites, the confidence in that correlation is above 80% (Box and Hansen, 2015). The physical mechanisms at work are probably hydrofracture in which the weight of water, being more than ice, adds force that can disaggregate ice (e.g. Weertman, 1973; Van der Veen, 1998) and forced convection driving more heat exchange between the (overall warming) ocean and the ice underbelly.

Box notes that from 2012 until today, Spalte glacier was the largest ice shelf in northern Greenland after Petermann Glacier experienced a major calving event significantly reducing the shelf’s volume. After the Spalte detachment, Petermann is once again the largest ice shelf.

In August 2010, the longest ice shelf connected to the Greenland ice sheet at Petermann Glacier (also then the Arctic’s largest ice shelf) calved 245 km2. Petermann ice shelf disintegration continued with a 140 km2 calving in 2012 (Jensen et al. 2015). The largest and most consistent (year to year) changes in Greenland glacier area are concentrated in the north of the island (Howat and Eddy, 2011; Box and Decker, 2011). The largest Greenland and Arctic ice shelf is now at the front of the North East Greenland Ice Stream.

A melange is the icy mix of icebergs cemented together with sea ice at the front of a glacier. 

x

Finally, direct evidence of mélange collapse prior to calving #glacier retreat. Nice work Suzanne! #climate#science#Greenland@EGU_TChttps://t.co/YClypXrWigpic.twitter.com/rxWzk9ulgJ

— StAndrews Glaciology (@StAndrewsGlacio) September 5, 2019

What happens in the Arctic doesn’t stay in the Arctic. Exhibit A: See Dorian, Lorenzo, Wutip and now, super typhoon Hagibis.

You more than likely have not seen this video. Loss of sea ice up to and including September of 2019

x xYouTube Video