National Geographic News
A photo of the Jakobshavn Glacier.

Chunks of ice litter the ocean in front of Greenland's Jakobshavn glacier.

PHOTOGRAPH BY PAUL SOUDERS, CORBIS

Jane J. Lee

National Geographic

Published February 4, 2014

A Greenland glacier named Jakobshavn Isbrae, which many believe spawned the iceberg that sank the Titanic, has hit record speeds in its race to the ocean. Some may be tempted to call it the king of the glacier world, but this speedy river of ice is nothing to crow about.

A new study published February 3 in the journal Cryosphere finds that Jakobshavn's averaged annual speed in 2012 and 2013 was nearly three times its rate in the 1990s. Its flow rate during the summer months was even faster.

"We are now seeing summer speeds more than four times what they were in the 1990s on a glacier which at that time was believed to be one of the fastest, if not the fastest, glaciers in Greenland," Ian Joughin, a researcher at the University of Washington in Seattle, told the BBC.

In summer 2012, Jakobshavn reached speeds of about 150 feet (46 meters) per day.

Other glaciers may periodically flow faster than Jakobshavn, but Greenland's most well known glacier is the bellwether of climate change in the region and likely contributes more to sea-level rise than any other glacier in the Northern Hemisphere—as much as 4 percent of the global total, Joughin and his colleagues found in an earlier study. (Read about glacial meltdown in National Geographic magazine.)

In Too Deep?

When glaciers flow into the ocean, their floating edge, or terminus, slows the river of ice behind it. Where the terminus is grounded on the seafloor, it can act like a doorstop, slowing the glacier's flow even further.

As warming temperatures in Greenland cause the Jakobshavn glacier to retreat up a long fjord, however—shedding icebergs in the process—the depth of the seafloor directly beneath the terminus varies.

In 2012 and 2013, the study authors say, the glacier's terminus retreated over a trough in the fjord that is 4,265 feet (1,300 meters) deep. As ice flowed into this deeper terminus, they think, the glacier behind the terminus accelerated and thinned—much as taffy thins in the middle when it's pulled from one end. The thinning in turn causes the glacier to melt faster. (See pictures of icebergs from James Balog's Extreme Ice Survey project.)

The Jakobshavn terminus now seems to be retreating up a hump in the seafloor, and that may slow the ice loss a bit in the coming years. But beyond that hump lies 30 miles (48 kilometers) of deep fjord.

The researchers suggest that in the coming decades Jakobshavn's speed could hit ten times that seen in the 1990s, slowing down only when the glacier has retreated to the head of the fjord.

The good news, says Penn State glaciologist Richard Alley, who was not involved in the new study, is that "the scariest possibilities are not happening." The Greenland ice sheet does not seem to be collapsing wholesale into the ocean over a timescale of years or decades.

Nevertheless, Alley says, the changes detected by Joughin and his colleagues "are not good news for the ice sheet or for people living near sea level."

"As the retreat of Jakobshavn 'unzips' this part of Greenland to let the warm waters in along the fjord," Alley says, it will allow more ice from the sides and the head of the glacier to fall into the sea. If other fjords around Greenland follow suit, he explains, the country's glaciers could accelerate sea-level rise.

Follow Jane J. Lee on Twitter.

21 comments
Tom Pugh
Tom Pugh

Wonder how all that fresh water will impact the conveyer that maintains temp equilibrium in waters of the northern/southern latitudes.  


Joe G.
Joe G.

I always hated Miami! If the greenland ice sheet melts that city and many others will disappear

Tako Nadibaidze
Tako Nadibaidze

It's sad, all we do is commenting out of anger, frustration. Hopefully, awakening won't happen too late especially since most of the biggest cities in the world are located at the coastlines or riverbanks.

Kiko del Mundo
Kiko del Mundo

Unless we do something about it, we can never slow the trend.

Heidi Morgan
Heidi Morgan

Mother Nature or Nature always wins, We will go extinct

Phillip Noe
Phillip Noe

We are seeing more and more consequences of climate change.  How many of us are doing anything about it?  Apathy in effect is a willingness to put future generations at risk.  We can and should do more to leave them a world that isn't in decline.  Please join the efforts.

ExhaustingHabitability(dot)com

James Crissman
James Crissman

@Ian Sloan Change that to YOU don't have a clue, Ian. The rest of us get it. The cure is a revenue neutral carbon tax and rebate system. See CitizensClimateLobby.org.  All we need is the political will before it's too late.

Ian Sloan
Ian Sloan

@Phillip Noe until you recognise the climate has always changed, and always will, and more importantly, such change is currently unpredictable, then any action is going to be pointless and detrimental.

jim adams
jim adams

Hey paulm -- several truisms about scientists:

>We'll argue vociferously with each other over almost every major scientific subject;



>Like you and every one else on the planet, we don't like to be wrong -- and so we tend to be a bit on the conservative side. Unlike you, scientists don't make sweeping judgments and in the case of IPCC, it is getting them in hot water on the climate front. Here's a brief but cogent article from one of the major scientific journals out there:http://www.scientificamerican.com/article/how-the-ipcc-underestimated-climate-change/



>science doesn't have a spokesperson or even group of spokespeople who speak for all of science;



>Scientists cite sources which have research-based date from which valid conclusions can be made using the scientific method (i note you have no sources -- just statements of your un-backed-up opinions);

_________________________

The SciAm article also mentions tipping points. Please note that the Arctic ice sheet has mostly melted it's thick ice. We do get annual increases of thin ice which annually disappears along with some more of the thick ice. The dark water now exposed to sunlight warms (ice reflects sunlight), and the Arctic is one of the fastest warming places on the planet. As shoreline snow melts, so does the permafrost around it's borders where billions of tons of frozen methane is stored, and it is starting to turn to methane gas in increasing quantities. For more on this, go to: http://www.planetextinction.com/planet_extinction_permafrost.htm    Also google: methane bomb and look at some of the sites it lists.



Please also note that the Arctic sea ice melted and we didn't -- and haven't -- done anything to change our behavior, and it may be too late to do something to keep the permafrost from completely melting. If you know of some way of doing this, please tell us. Otherwise we have the decade long emergency actions the Planet Extinction site talks about.

_________________________

Don't trust the carbon cap and trade -- it seems that it was put together by Enron (remember Enron?) and Goldman-Sachs people to create another economic bubble which most major corporations try to ride right up to just before it bursts -- then they get out a lot richer and we all pay the price like we did for the 2008 derivative bubble and the later mortgage bubble.  http://dev.storyofstuff.org/wp-content/uploads/2011/10/capandtrade_footnoted_script.pdf.

____________________________

Besides this NatGeo article, also go to http://ngm.nationalgeographic.com/2010/06/melt-zone/jenkins-text This article documents that soot from wildfires settles on the Greenland glacier and causes it to melt faster. Considering that Greenland is about the size of the Louisiana Purchase, the small amount they report here is a huge amount of melting over the whole glacier.

____________________________

And you may be wondering why the CO2 content of our atmosphere is so low, considering how much anthropogenic CO2 we have dumped in our air. Google: ocean acidification. Also, go to http://ngm.nationalgeographic.com/2011/04/ocean-acidification/kolbert-text and learn a bit more of what we're doing to our planet.

_________________________

This is just a brief introduction to a few of the environmental hassles we have to confront and conquer if we want a future on our world.



Mother Nature always bats last, and it's her turn at bat.



Colin Kellogg
Colin Kellogg

@Paul M.  Paul, the great thing about science is that it is not a "belief system" but rather, it is a "discipline" with a rich history of rules of observation, replicability, demands for rigor, and it is a world-wide agreed-upon language that is as salient in Soeul Korea as it is in Cambridge Massachusetts. We do not teach our children to "believe science", we teach them to test it, to challenge it, to observe ever more closely. Science, by its very definition, cannot be "certain" of anything that includes natural variability. You cannot be certain that I, for example, "hate neo-cons", but I sure do hate whiny little miscreants who did not pay attention in class.

Phillip Noe
Phillip Noe

@Paul M.   Same old baseless babble paulm?  You still haven't said why you can't find ONE respected scientific institution that agrees with you.  Why is that?

Blue WingedOlive
Blue WingedOlive

@James Crissman @Ian Sloan  Crissman, try a little critical thought.  Sloan's point is that we really don't know the cause of temp variation, and the article supports his view.  Do you have a reply to the central point?

Richard Ainsley
Richard Ainsley

Looks like God kinds wants that from what I know. Are you content to go along with that?


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