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New Greenland Ice Melt Fuels Sea Level Rise Concerns

Stability in the rapidly changing Arctic is a rarity. Yet for years researchers believed the glaciers in the frigid northeast section of Greenland, which connect to the interior of the country’s massive ice sheet, were resilient to the effects of climate change that have affected so much of the Arctic.

But new data published Sunday in Nature Climate Change reveals that over the past decade, the region has started rapidly losing ice due to a rise in air and ocean temperatures caused in part by climate change. The increased melt raises grave concerns that sea level rise could accelerate even faster than projected, threatening even more coastal communities worldwide.

Helheim glacier in southeast Greenland.
Credit: Henrik Egede-Lassen

“North Greenland is very cold and dry, and believed to be a very stable area,” said Shfaqat Khan, a senior researcher at the Technical University of Denmark who led the new study. “It is surprisingly to see ice loss in one of the coldest regions on the planet.”

The stability of the region is particularly important because it has much deeper ties to the interior ice sheet than other glaciers on the island. If the entire ice sheet were to melt -- which would take thousands of years in most climate change scenarios -- sea levels would rise up to 23 feet, catastrophically altering coastlines around the world.

Sea levels have risen 8 inches globally since the start of the 1900s, and current projections show that figure could rise another 3 feet by the end of this century.

Some recent research has suggested that Greenland’s ice loss may slow, but not all researchers agree. Jason Box, a glaciologist at the Geological Survey of Denmark and Greenland, said the new study presented a novel analysis of the region and that other factors such as soot could contribute to even more rapid melt in Greenland and other parts of the Arctic.

“These new measurements show that the sleeping giant is awakening and suggest -- given likely continued Arctic warming -- that it’s not going back to bed,” Box said in an email.

Greenland houses 680,000 cubic miles of ice in its ice sheet, which stretches up to 3 miles thick in some places and covers roughly three-quarters of the island. Glaciers stretch from this frozen mass in all directions, eventually meeting the sea. In the past 20 years, some of these glaciers, particularly in the southeast and northwest, have dumped ever increasing amounts of ice into the ocean. That water has accounted for more than 15 percent of global sea level rise over that period.

Since the mid-1960s, climate change has helped drive average air temperatures up about 3.6°F across the Arctic, more than double the increase compared to midlatitudes. The rise in air temperatures has fueled a tumultuous decline in sea ice, which has also helped warm the region’s ocean waters. Around parts of Greenland, ocean surface temperatures rose 1.8°-3.6°F between 1990-2011.

While the northwest and southeast section of Greenland have dramatically lost ice, researchers believed the northeast section was holding its ground. From 1978-2003, that was true, but ice loss has accelerated rapidly since mid-2003.

The Zachariae glacier has long acted as a sentinel on the northeast coast of the island, keeping ocean waters at bay from a 370-mile long stream of ice that stretches into the heart of Greenland’s massive ice sheet.

But a series of unusually warm summers around 2003 started to trigger glacial melt. At the same time, a spike in ocean surface temperatures also helped melt sea ice that normally acts as a buttress for the Zachariae and other glaciers in northeast Greenland. Without reinforcement, the glaciers suddenly started to draw down more ice from on high and retreat faster.

That fueled a feedback loop by allowing the anomalously warm ocean water to flow under the glaciers, helping them slide further to the sea. The Zachariae glacier is particularly susceptible to this process because the land under it slopes downward for miles inland, potentially inviting more ocean water to slide under it and further destabilize the glacier.

A view of Upernavik glacier in northwest Greenland.
Credit: Shfaqat Abbas Khan

By 2012, the snout of the Zachariae glacier had receded more than 12.4 miles from its 2003 position. In comparison, the Jakobshavn glacier, located in southwest Greenland and long considered one of the fastest-changing glaciers on the island, has retreated 21.7 miles over the past 150 years.

Sea ice concentrations have climbed in recent years, yet the glaciers in the region are still losing mass faster than at any time in the past decade. The most dramatic form of ice loss comes during calving events, when large chunks of ice break off their ends and drift out to sea. Khan said glaciers in this and other parts of Greenland experience calving events 4-6 times a year.

The most famous event in Greenland occurred in August 2010 when an iceberg four times the size of Manhattan ripped away from Petermann glacier on the northwest side of the island. Another major chunk of ice also fell of the same glacier in July 2012.

While calving events garner headlines, Khan said understanding the underlying processes that lead to calving are much more important in determining the fate of glaciers around Greenland, but particularly Zachariae and other glaciers in the northeast.

“We really want to know what is going on beneath the glaciers,” he said. “This is the area where it may become unstable, causing retreat, thinning and huge dynamic ice loss.

“The northeast drainage area is twice that of Jakobshavn. Thus, here we have an area that could be Greenland’s largest contributor to sea level rise in a few years.”

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Comments

By Mauri S Pelto (West Boylston)
on March 16th, 2014

Interesting report worthy of our attention. I would recommend using images from the actual area of northeast Greenland.  There are plenty from either Storstrommen or Zacharaiae .  It is also worth noting that at present Zachariae has a velocity that is close to 10% of Jakobshavn.

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By Lewis Cleverdon (Central Wales)
on March 16th, 2014

Brian - how about posting an addendum giving the critical numbers describing the potential of the decline of the GIS - specifically the cubic kilometers of ice lost in 2013 and the doubling period this represents ? (Doubling period being the number of years since the output was half that of 2013). Taking the trend of a decade of doubling periods gives a strong indication of the current acceleration of ice loss.

For the record, the image shown above of darkened snow - alongside discussion of the impact of soot on the ice sheet - is actually showing an area of quite severe Cryoconite infestation, and has nothing to do with soot. For any reader unaware of these microbes, they occur as small black granules formed of microbes and windblown minerals collected from melting ice in the ablation zone of ice sheets. Being black, once the winter snowfall has melted off, they capture solar heat and melt themselves little suntraps in the clean ice surface.

Given that the ablation zone is gaining altitude each year on the GIS, and that upper levels are far less steep than lower down, the area of cryoconite ice-degradation is increasing at an accelerating rate. The additional melt water they generate is almost entirely drained via streams, melt-lakes and moulins, but the rising ablation zone means that there are increasing areas that drain down within Greenland’s encircling ring of mountains beneath the ice sheet, thus accelerating the transport of solar heat to melt its base from within.

Quite why Dr Box is studying soot deposition (which doesn’t appear to show up in the sides of newly-melted ice ravines despite the northern hemisphere’s massive historical soot output) rather than the albedo loss effects of the cryoconites, is a mystery to me.

Regards,

Lewis

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By Dave (Basking Ridge, NJ 07920)
on March 17th, 2014

I would be interested in a discussion of that question from an ice dynamics expert too Lewis.  Projected future ice mass loss rates and future rates of SLR are highly sensitive to the functional form of sustained changes. Any long term and systematically sustained acceleration in ice mass loss rate would also have an accumulating effect such that out year rates could get so high under such scenarios as to be difficult to imagine regarding the corresponding magnitude of the environmental challenges.

So what does the data say? The published GRACE measurements of recent ice mass loss for Greenland during the period 2003 – 2012 that I have seen, (example - Slide 9: http://congrexprojects.com/docs/12c20_docs2/2-grace_esa-clic_forsberg.pdf?sfvrsn=2), do show a current overall, albeit lumpy, trend upwards in the rate of ice mass change during this recent period – with a large net loss registering since 2007 - 2009.  However that is only 10 years worth of data whereas technically we would much prefer to have a century of data. So to be practical, maybe it is at least fair to say, in view of the current data including the observations in this and similar articles, that some acceleration has obviously occurred and that for various reasons an acceleration could indeed plausibly continue.

Then I think it adds focus to consider what different sustained levels of mass loss and acceleration of that rate imply. GRACE shows a current average linear rate (over ten years) of ice loss of around 244 Gt per year for GIS. That’s equivalent to 220 cubic km of ice. If that rate continued unchanged then the entire ice sheet would disappear in around 10,000+ years. On the other hand, with a sustained 20 year doubling period for the rate of loss, that time instead drops like a stone to under 300 years. Also, the average annual rate of melting of GIS under that example 20 year doubling rate scenario in the final years just before total disappearance would be on the order of 200,000 cubic km equivalent to a mean sea level rate of rise of about one foot each year. And of course that would not include any contribution to SLR from Antarctica. But most importantly, most of the ice as a fraction of the current amount there today would only be lost in the final doubling period before total disappearance.

Perhaps a sustained geometric acceleration in the rate of ice loss will turn out to be unrealistic. I hope so. On the other hand it seems to me important to ask the question and consider this possibility. This is because of the implications of the clearly demonstrable basic fact that if it is indeed realistic, then by the time enough data is accrued in order to be able to confidently characterize the ice loss rate and make projections with reasonable certainty, GIS (and possibly the WAIS as well) may be so far gone that catastrophic total deterioration would be just around the corner. That seems like a point worth discussing!

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By Dave (Basking Ridge, NJ 07920)
on March 18th, 2014

Sorry – there were numerical errors in my comment yesterday.

In “…. on the order of 200,000 cubic km equivalent to a mean sea level rate of rise of about one foot each year.” This should instead read 50,000 cubic km and 5 inches per year.

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By Ray Del Colle
on March 28th, 2014

“Whether you look at tide gauges or satellite data, sea levels are going up.” http://clmtr.lt/c/EXy0hY0cMJ

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By Richard Guy (New York)
on March 28th, 2014

The method of measuring sea level with Sea Level Guages is ludicrous and has to be abolished. To fix a guage to a wharf or a landing is farcical because it is not stable and neither is the sea level. The wharf is supposed to be rising if you believe that the land mass is responsing to Isostacy. On the other hand the sea level is receding while the wharf is rising. So to equate which method is more relaible we see how rediculous both methods are, The sea is receding so the guage will register a falliong sea level. Attaching the guage to any land founded object is useless.
You may as well place the sea level guage on a floating object. See the Video series entitled “The Mysterious Receding Seas” by Richard Guy on www.youtube.com an see web Page :http://xbraille.wix.com/receding-seas
email: richardguy9@gmail.com

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By Wiley Wayne (North Olmsted, OH 44070)
on April 23rd, 2014

Tidal Gauges have been used for hundreds of years.  We don’t know the full story of how they were set up and used. However, in Australia you will find some very long term tidal gauge archives with pretty good explanations. As a scientist, I can assure you, your observations are correct for some tidal gauge measurements. Precautions against
bogus measurements would include:  Use of land based sighting rods to determine land movement, dock movement, and so forth. Not insurmountable by any means. Satellite measurements are not without their problems either. Claiming an accuracy of better than the thickness of two dimes from space is a wonder to behold.  I guess that is why NASA is building a better space-born SLR measuring system.

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