Is it Time to Bid Greenland Farewell?
by Jeremy Elton Jacquot, Los Angeles on 04.25.08
Are Greenland's days already numbered? And, if so, can anything be done to avert the looming disaster posed by a massive sea level rise? The simple answer is that though Greenland's fate is not yet set into stone (at least when it comes to a specific date), the present melting trends do not bode well.
Calling Greenland's potential collapse another climate "tipping point" would be doing it fair justice -- after all, scientists have estimated that were its ice sheet (which holds one-twentieth of the world's ice) to melt completely, global sea levels would jump 7 meters. As Alexandra Witze reports in the latest issue of Nature (sub. required), Greenland's disappearance is one of the foremost concerns weighing on climate researchers' minds.
It's no big secret that Greenland has been melting at an accelerated rate over the past few summers: It has lost an average of 380 - 490 billion tonnes of ice each year over the last 4 years -- or around 150 billion tonnes more than it gains in snow during the summer. Despite this worrying trend, however, cautious scientists will tell you that it is still too early to predict Greenland's untimely demise. One main reason is that the models and tools scientists use simply aren't yet up to the task.
Various resources exist, primarily satellites, that have driven most of the recent research in this field. The Gravity Recovery and Climate Experiment (or GRACE, for short), a pair of U.S.-satellites orbiting the Earth 500 kilometers above us, has proven an invaluable asset in documenting much of Greenland's changes. The satellite pair continuously measure the distance separating them -- a value that changes as massive objects on Earth pull one or the other (through gravity) -- and use it as a proxy for assessing the changes in Greenland's ice sheets.
Yet the data GRACE provides is not foolproof: one problem is that it fails to accurately take the effect of "post-glacial rebound" into account. During the last ice age, Greenland's ice sheet was much bigger and, as a result, pressed the underlying crust into the dense mantle below; even though much of this ice has now disappeared, large portions of the crust have not yet rebounded from their position. This slow, gradual bounceback has made the analysis of GRACE's data difficult.
The Greenland GPS Network (GNET), a system of GPS receivers installed around Greenland to measure the bounceback effect, could eventually help resolve these discrepancies, though scientists will first need to ramp up their measurements and improve the quality of their models. The ever-evolving nature of climate science -- and the changes in our understanding of the subject it inevitably sparks -- mean that the tools we use will need to constantly adapt to the changing circumstances and, in some cases, simply be discarded.
In addition to air temperatures, scientists are now also starting to assess the impact of changing ocean temperatures on the rate of retreat of Greenland's glaciers. Many realize that their past models were too conservative in estimating the rate of ice sheet melting -- a problem many ascribe to a lack of data. Moreover, the modelers are wary of using a single set of data from one melting season or location to generalize over the whole ice sheet.
Tackling these challenges will, at the very least, take many months, if not years. As satellite technologies improve and scientists develop new tools to obtain data and measure other variables, our understanding will improve and our predictions will become more precise. The worry is that by the time we get it just right, it might already be too late.
In her blog post on the subject, Witze provides more insight and some updates on our understanding of the science and links to several other posts dealing with Greenland's melting, including a very incisive one from the crack team at RealClimate, which is well worth the reading.
Image courtesy of NASA/GSFC via Nature
Via ::Climate Feedback: Losing Greenland (blog)
Check out an animated version of Greenland melting on Discovery's Earth Live tool.
See also: ::Greenland Ice Melting at Record Rate, ::Global Warming Beer: Greenland Brews with Melting Ice Cap
Call for Entries: Discovery Young Scientist Challenge 2008
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This story should be on the front pages of major newspapers; it is that important. In my view, the writing is on the wall that we, especially in the U.S., have to change the way we are living to deal with global warming. We can still have an excellent quality of life as we consume less fossil fuels. More at Diamond-Cut Life http://alison97215.wordpress.com/
best,
Alison in Portland, Oregon
This is what I would call alarmism. Compared to how much ice is on Greenland and how much water is in the ocean, the amount that it's losing isn't that much. Plus, you said it's 150 billion tonnes more than what snow falls on it "during the summer". That's a curious statement.
In summary, scientists aren't sure about Greenland's fate, it's melting a decent amount, but it's not melting too much, and we really can't be sure.
I'm not sure why this is on Treehugger. There's nothing new here. It's alarmism.
Just to put things into perspective a bit, here are some excerpts from the Wikipedia entry on Greenland. Make of it what you will.
"Data from ice cores indicate that from AD 800 to 1300 the regions around the fjords of southern Greenland experienced a relatively mild climate similar to today. Trees and herbaceous plants grew there, and the climate initially allowed farming of livestock..."
"Analysis of the layering and chemical composition of the cores has provided a revolutionary new record of climate change in the Northern Hemisphere going back about 100,000 years and illustrated that the world's weather and temperature have often shifted rapidly from one seemingly stable state to another, with worldwide consequences."
"Scientists who probed two kilometers (1.2 miles) through a Greenland glacier to recover the oldest plant DNA on record said Thursday the planet was far warmer hundreds of thousands of years ago than is generally believed. DNA of trees, plants and insects including butterflies and spiders from beneath the southern Greenland glacier was estimated to date to 450,000 to 900,000 years ago, according to the remnants retrieved from this long-vanished boreal forest. That view contrasts sharply with the prevailing one that a lush forest of this kind could only have existed in Greenland as recently as 2.4 million years ago. The existence of those DNA samples suggest the temperature probably reached 10 degrees C (50 degrees Fahrenheit) in the summer and -17 °C (1 °F) in the winter. They also indicated that during the last interglacial period, 116,000–130,000 years ago, when temperatures were on average 5 °C (9 °F) higher than now, the glaciers on Greenland did not completely melt away."
"In 2007, the existence of a "new" island was announced. Named "Uunartoq Qeqertoq" (English: Warming Island), this island has always been present off the coast of Greenland, but was covered by an ice sheet. This ice sheet was discovered to be shrinking rapidly in 2002, and by 2007 had completely melted away, leaving the exposed island. This however was not the first occurrence of the island distinction. In Arctic Riviera, published by Ernst Hofer in 1957, in maps, and pictures, Ernst Hofer showed the distinct three fingered island separate from the mainland, during a similar warming event."
Greenland so I believe was named as during earlier melts the land was Green. So if in earlier times the ice melted and land was farmed and green why wasn't it under water then?
The roof of York minster was decorated with grape, the designs coming from local vegitatian growing readily. We have had periods of warming in the past and will have periods of cooling again.
Remember in the 70's we were just about to enter a world threatening ice age.
Pollution and environment are important issues and we need to look after the fragile Earth. However the money and investment in Greenwashing is distorting the facts.
It was interesting reading on the energy saving forums how bloggers in the US were managing to survive on yearly 3-4MW! (the average being 9MW!) Its surprising that 'green' Americans cutting back and blogging on forums still manage to use more energy than myfamily of 4 living in a 6 bed house in the UK!
Chris, re: your comment "Remember in the 70's we were just about to enter a world threatening ice age."
I ran across the following written by John Fleck and William Connolley
During the period we analyzed, climate science was very different from what you see today. There was far less integration among the various sub-disciplines that make up the enterprise. Remote sensing, integrated global data collection and modeling were all in their infancy. But our analysis nevertheless showed clear trends in the focus and conclusions the researchers were making. Between 1965 and 1979 we found (see table 1 for details):
* 7 articles predicting cooling
* 44 predicting warming
* 20 that were neutral
In other words, during the 1970s, when some would have you believe scientists were predicting a coming ice age, they were doing no such thing. The dominant view, even then, was that increasing levels of greenhouse gases were likely to dominate any changes we might see in climate on human time scales.
Anonymous; you might also add to your list, the following:
"ScienceDaily (Apr. 16, 2008) — A team of scientists including polar expert Dr. Derek Mueller from Trent University and Canadian Rangers have discovered that the largest ice shelf in the Northern Hemisphere has fractured into three main pieces...."
That article concludes with the observation "...Only five large ice shelves remain in Arctic Canada, covering less than a tenth of the area than they did a century ago."
"...scientists have estimated that were its ice sheet (which holds one-twentieth of the world's ice) to melt completely, global sea levels would jump 7 meters."
It's not the melting in place that will happen so quickly. Surface melt on top of the ice bores through the ice sheets and lubricates the underside. This, in turn, accelerates their travel to the sea.
When ice sheets meet the sea, they break up and float away where the ice melts very rapidly causing sea level rise. This process can empty the vast ice sheets of interior Greenland into the ocean fairly quickly.