Search Results for Tag: glaciers
Human action speeds glacial melting
It might sound like stating the obvious, but in fact it is not easy to find clear evidence that human behavior is behind the retreat of glaciers being monitored in different parts of the world. Hence my interest in a study just published in the journal Science.
The main problem is that it usually takes decades or even centuries for glaciers to adjust to climate change, says climate researcher Ben Marzeion from the Institute of Meteorology and Geophysics of the University of Innsbruck. He and his team of researchers have just published the results of a study for which they simulated glacier changes during the period from 1851 to 2010 in a model of glacier evolution. They used the recently established “Randolph Glacier Inventory” (RGI) of almost all glaciers worldwide to run the model, which included all glaciers outside Antarctica.
“Melting glaciers are an icon of anthropogenic climate change”, the authors say. However, they stress that the present-day glacier retreat is a mixed response to past and current natural climate variability and “current anthropogenic forcing”. Their modeling shows though that whereas only 25% of global glacier mass loss between 1851 and 2010 can be attributed to human-related causes, the fraction increases to around 69% looking at the period between 1991 and 2010. So human contribution to glacier mass loss is on the increase, the experts write.
Marzeion says the global retreat of glaciers observed today started around the middle of the 19th century at the end of the Little Ice Age, responding both to naturally caused climate change of past centuries (like solar variability), and to human-induced changes. Until now, the real extent of human contribution was unclear. The authors say their latest piece of work provides clear evidence of the human contribution.
Once more I am happy to refer to the Climate News Network, in this case to Tim Radford, for an easy-to-read summary of the main research results and the background. There is no doubt that glaciers are losing mass, retreating uphill and melting at a faster rate, says Radford. He refers to some Andes glaciers and the the Jakobshavn glacier in Greenland, or Sermeq Kujualleq as I prefer to call it, using the indigenous name. Ice Blog followers may remember my own trip to Greenland and that particular glacier. I have also written on the speeding of the melt there on the Ice Blog and on the DW website.
Radford also refers to ascertaining the melting of alpine glaciers by comparing historic paintings and other documentation with the current ice mass. That decline is something I have observed at first hand in Valais in Switzerland during regular visits over the past 30 years. Look out for a comparative photo gallery of my own pics, when I get time to put it together. Since most of the shots are from the pre-digital era, that will be a time-consuming task.
I also remember a trip to the Visitor Centre of the Begich Boggs glacier in Alaska in 2008. The glacier has already retreated so far you can’t see it at all from the Centre built specially for the purpose of viewing it.
The question until now was how much of all this was caused by natural developments and how much to changes in land use and the emission of greenhouse gases? The latest study supported, among others, by the Austrian Science Fund (FWF) and the research area Scientific Computing at the University of Innsbruck, has come up with some answers. Since the climate researchers were able to include different factors contributing to climate change in their model, they can differentiate between natural and anthropogenic influences on glacier mass loss
“While we keep factors such as solar variability and volcanic eruptions unchanged, we are able to modify land use changes and greenhouse gas emissions in our models,” says Ben Marzeion, who sums up the study: “In our data we find unambiguous evidence of anthropogenic contribution to glacier mass loss.”
As always, there is still need for further research – and a lot more monitoring. The scientists say the current observation data is insufficient in general to derive any clear results for specific regions, even though anthropogenic influence is detectable in a few regions such as North America and the Alps, where glaciers changes are particularly well documented.
With global glacier retreat contributing to rising sea-levels, changing seasonal water availability and increasing geo-hazards, the study’s conclusions should help put a little more pressure on the world’s decision-makers to get serious about emissions reductions.
DateAugust 18, 2014 | 1:03 pm
Cryosphere in Crisis?
You can’t say the latest research results on the thinning of the West Antarctic ice sheet didn’t make the media. From the news agencies through the quality media and even publications not known for their detailed science or environment coverage – nearly all reported that two separate studies each independently come to the conclusion that parts of the West Antarctic ice sheet are already “collapsing”. They say this could result in a considerable sea level rise within the next century or two. This would have devastating consequences for low-lying coastal areas around the globe.
No-one can really say they didn’t know about this. For once, the Antarctic ice has made into the headlines of the mainstream media. This is the region people tend to think of as having “eternal ice”, where global warming will “not make much difference”. There are those who criticize the media for sensationalism or exaggeration by taking over the term “collapse” for a process which will still take hundreds to thousands of years. See for example Andrew Revkin’s post on Dot Earth (New York Times), (and an excellent response by Tom Yulsman in ImaGeo: (Discover Magazine). But, semantic discussions apart – as Yulsman puts it:
“On a human timescale, 200 years or more for the start of rapid disintegration is a very long time indeed. But on a geologic timescale, it is the blink of an eye. And that’s important to keep in mind too — that in a blazing flash, geologically speaking, we humans are managing to remake the life support systems of our entire planet. This is why I think today’s news may eventually be seen as having historic significance”. At any rate, he concludes “it is yet another clear sign that human-caused changes to the planet once regarded as theoretical are now very real”.
Indeed Tom. The question is: what are we going to do about it? Has it set the alarm bells ringing? Did anybody see a rash of reactions promising quick action on reducing emissions to mitigate climate change? If so, please point me in the right direction. So far, I haven’t seen any indication of anything other than business as usual.
The West Antarctic ice sheet contains so much ice that it would raise global sea level by three to four meters if it melted completely. As it sits on bedrock that is below sea level, it is considered particularly vulnerable to warming sea water. Until now, scientists assumed it would take thousands of years for the ice sheet to collapse completely. The two new studies indicate that could happen much faster – as early as 200 years from now or, at the most, 900. Both research teams, using different methods and looking at different parts of the ice sheet, conclude that the trend is probably unstoppable.
The NASA study published in “Geophysical Research Letters” uses data from satellites, planes, ships and measurements from the shelf ice to examine six large glaciers in the Amundsen Sea over the last 20 years. The second report, from the University of Washington published in the journal “Science,” uses computer models to study the Thwaites glacier. It is considered of particular importance because it acts as a type of “lynch pin”, holding back the rest of the ice sheet.
According to NASA researcher Eric Rignot, the glaciers in the Amundsen Sea sector of West Antarctica have “passed the point of no return.” He told journalists this would mean a sea level rise of at least 1.2 meters (3.93 feet) within the next 200 years.The University of Washington scientists worked out, using topographical maps, computer simulations and airborne radar, that the Thwaites glacier is also in an early stage of collapse. They expect it to disappear within several hundred years. That would raise sea levels by around 60 centimeters (23.62 inches). The NASA study showed that sea level rises of 1.2 meters are possible
The good news, according to author Ian Joughlin, is that while the word “collapse” implies a sudden change, the fastest scenario is 200 years, and the longest more than 1,000 years. The bad news, he adds, is that such a collapse may be inevitable: “Previously, when we saw thinning we didn’t necessarily know whether the glacier could slow down later, spontaneously or through some feedback,” Joughlin says. “In our model simulations it looks like all the feedbacks tend to point toward it actually accelerating over time. There’s no real stabilizing mechanism we can see.”
The latest IPCC report does not adequately factor ice loss from the West Antarctic ice sheet into its projections for global sea level rise, on account of a lack of data. These “will almost certainly be revised upwards,” according to Sridar Anandakrishnan from Pennsylvania State University at the presentation of the University of Washington study. The scientist was not involved in the research.
NASA glaciologist Rignot said he was taken aback by the speed of the changes. “We feel this is at the point where … the system is in a sort of chain reaction that is unstoppable,” he said.
Rignot also makes the key point that this development tells us not only about the area down at the South Pole, but about the whole climate system: “This system, whether Greenland or Antarctica, is changing on a faster time scale than we anticipated. We are discovering that every day.”
My last two blog posts have been about melting of the Greenland ice sheet and melting even in the East Antarctic, which is usually cited as the last bastion against ice-destroying climate change. We are subjecting our cryosphere to huge pressures and have set a “snowball” rolling, which is picking up momentum and will ultimately carry masses of ice into a rising ocean.
Rignot says even drastic measures to cut greenhouse gas emissions could not prevent the collapse of the West Antarctic ice sheet. That is a terribly depressing thought. I would like to think this will prove wrong. But if there is any chance to avert that disaster and preserve our polar ice for thousands of years rather than just a few hundred, surely the time for action is now?
DateMay 14, 2014 | 2:46 pm
Greenland melt natural or man-made?
And does it ultimately make any difference? Scientists from the University of Washington (UW) have published a paper in Nature estimating that up to half of the recent warming in Greenland and surrounding areas may be due to climate variations that originate in the tropical Pacific and are not connected with the overall warming of the planet. You can just hear the “I told you so”, from the climate skeptics. “Still”, the UW scientists add, “at least half the warming remains attributable to global warming caused by rising carbon dioxide emissions”.
With all due respect to the scientists who do this essential research – I repeatedly find myself wondering how we can talk about “natural” climate variations at all any more, given that we have changed the parameters so much you could argue none of it is really without human impacts. Does natural fluctuation not act differently if you are starting from completely different base data, brought about by man-made warming through greenhouse gas emissions?
Greenland and parts of neighboring Canada have experienced some of the most extreme warming since 1979, at a rate of about 1 degree Celsius per decade, or twice the global average, the scientists say. “We need to understand why in the last 30 years global warming is not uniform”, says first author Qinghua Ding, a UW atmospheric research scientist. “Superimposed on this global average warming are some regional features that need to be explained”.
The study uses both observations and advanced computer models. It comes to the conclusion that a warmer western tropical Pacific Ocean has caused atmospheric changes over the North Atlantic that have warmed the surface by about half a degree per decade since 1970. “The pattern of the changes in the tropical Pacific that are responsible for remarkable atmospheric circulation changes and warming in Greenland and the Canadian Arctic are consistent with what we would call natural variability”, says co-author David Battisti, a UW professor of atmospheric sciences.
Of course there will always be natural variability in the course of the seasons and changing meteorological conditions. But in many of the fastest—warming areas on earth, co—author of the new study John “Mike” Wallace, also professor at UW, says global warming and natural variations combine to create a “perfect storm” for warming.
The scientists attribute the natural variations in their study to an “unusually warm western tropical Pacific, near Papua New Guinea. Sind the mid-1990s the water surface there has been about 0.3 degrees hotter than normal. Computer models show this affects the regional air pressure, setting off a stationary wave in the atmosphere that arcs in a great circle from the tropical Pacific toward Greenland before turning back over the Atlantic”. Wallace says there are warm spots where the air has been pushed down, and cold spots where the air has been pulled up. And Greenland, he explains, is in one of the warm spots”.
This and other research by these scientists has documented the existence of decades-long climate variations in the Pacific Ocean which resemble the better known shorter-range El Nino variations. Other studies have indicated that waves starting in the same place in the tropical Pacific but radiating southward are warming West Antarctica and melting the Pine Island Glacier, which has been the subject here on the Ice Blog before.
The experts describe this natural variation as “unpredictable”, whereas the half of the warming in Greenland from the “forcing of climate by anthropogenic greenhouse gases” is “predictable”.
So what do we learn from all of this? One thing is clear. It does NOT change the threat to Greenland’s ice from our man-made warming: “Nothing we have found challenges the idea that globally, glaciers are reatreating, says Battisti. “Ice appears to be exquisitely sensitive to the buildup of greenhouse gases, more than we ever would have thought”, says his colleague Wallace.
Ultimately, the researchers say, natural variations could either accelerate or decelerate the melting rate of Greenland’s glaciers in coming decades. But, “in the long run, the human induced component is likely to prevail”.
So don’t let anybody use this as an excuse to talk down the need to cut emissions in a big way asap.
DateMay 7, 2014 | 4:09 pm
Greenland’s icecap losing stability
Catching up on the last few weeks of icy news after a spring holiday, my eye was caught by an item by Tim Radford from the Climate News Network, dated April 13th. I quote: “Greenland is losing ice from part of its territory at an accelerating rate, suggesting that the edges of the entire ice cap may be unstable”. This caught my attention not just because anything relating to Greenland tends to do that, but because the development could have major significance for the future world climate and sea level- and because it doesn’t seem to have made its way into the mainstream media at a time when sensitivity to the issue should have been high after the IPCC report.
The Greenland ice sheet is the largest terrestrial ice mass in the northern hemisphere. Radford draws attention to a study in Nature Climate Change by Shfaqat Khan from the Technical University of Denmark and colleagues, which indicates that the ice sheet could be melting faster than previously thought. This would mean Greenland’s contribution to sea level rise has been under-estimated (once again!), and oceanographers may need to think again about their projections.
The scientists used more than 30 years of surface elevation measurements of the entire ice sheet to discover that overall loss is accelerating. Previous studies had identified melting of glaciers in the island’s south-east and north-west, but the assumption had been that the ice sheet to the north-east was stable, Radford writes:
“It was stable, at least until about 2003. Then higher air temperatures set up the process of so-called dynamic thinning. Ice sheets melt every Arctic summer, under the impact of extended sunshine, but the slush on the glaciers tends to freeze again with the return of the cold and the dark, and since under historic conditions glaciers move at the proverbial glacial pace, the loss of ice is normally very slow.”
But with global warming, Greenland’s southerly glaciers have been in retreat and one of them, Jakobshavn Isbrae or Sermeq Kujalleq, is now flowing four times faster than it did in 1997. I first reported on this during a trip to Greenland in 2010, and have presented various new studies on it here on the Ice Blog since.
The new research by the Danish-led team considers changes linked to the 600 kilometre-long Zachariae ice stream in the north-east, using satellite measurements. It has retreated by some 20 kilometres in the last DECADE, whereas Sermeq Kujalleq has retreated about 35 kms in 150 years. The Zachariae stream drains around one-sixth of the Greenland ice sheet, and because warmer summers have meant significantly less sea ice in recent years, icebergs have more easily broken off and floated away, which means that the ice stream can move faster. “North-east Greenland is very cold. It used to be considered the last stable part of the Greenland ice sheet,” said one of the team, Michael Bevis of Ohio State University in the US, in an interview with the Climate News Network.
“This study shows that ice loss in the north-east is now accelerating. So now it seems that all of the margins of the Greenland ice sheet are unstable.”
The scientists used a GPS network to calculate the loss of ice. Glacial ice presses down on the bedrock below it: when the ice melts, the bedrock rises in response to the drop in pressure, and sophisticated satellite measurements help scientists put a figure on the loss of ice. They calculate that between April 2003 and April 2012, the region was losing ice at the rate of 10 billion tons a year.
“This implies that changes at the margin can affect the mass balance deep in the centre of the ice sheet,” said Dr Khan. Sea levels are creeping up at the rate of 3.2 mm a year. Until now, Greenland had been thought to contribute about half a mm. The real figure may be significantly higher, according to the report.
This is a very worrying development, but it seems to me it did not get a lot of public attention. This brings me back to the question of the discrepancy between what we know about the impacts of climate change and the widespread lack of political and consumer action. (See my article Denial or Disconnect: Why don’t we act on climate change?)
Are people sticking their heads in the sand (or melting snow)? Have we just been assured so many times that the Greenland ice sheet will never melt that we don’t sit up and take notice? Is it too far away in time and space to bother us? Are too many people giving up and resigning themselves to the fact that climate change is inevitable? Is it just so much easier to hold on to the status quo instead of having to make changes to our 21st century lifestyles?
DateApril 22, 2014 | 2:38 pm
Greenland glacier at record speed
I have been working on a story about whether the Arctic infrastructure would be able to cope with a shipping or oil spill accident, which is increasingly likely to occur as development speeds ahead. During the Arctic Frontiers conference in Tromso, I attended an interesting workshop on the topic, where the organisers, the Arctic Institute Center for Circumpolar Security Studies, came to what their experts describe as “worrisome” conclusions. Malte Humpert, Kathrin Keil and Marc Jacobsen presented three incident scenarios involving shipping and oil exploration in the Arctic. Jacobsen’s scenario involved a giant cruise boat with 3000 people on board hitting an iceberg off the West Greenland Coast, near Ilulissat.
In 2009 I was in Ilulissat, working on radio features on climate change in Greenland. This is the Greenland of the tourist brochures, with a constantly changing panorama of icebergs floating past your hotel window – or porthole if you are on a ship. While I was there, the fragility of that beautiful glacier ice was brought home to me.
The Sermeq Kujalleq glacier, also still known by its Danish name “Jakobshavn Isbrae”, is the fastest flowing glacier in Greenland (or Antarctica, these two major ice sources being of key importance to global sea level). The icebergs which create the spectacle floating past the brightly coloured houses of Ilulissat, are breaking off from the glacier. Beautiful to look at, extremely worrying if you think about the background. Back in 2009, scientists were already telling me the glacier was speeding up. Now the latest research published in The Cryosphere (the journal of the European Geosciences Union) confirms that the summer flow of the ice mass has reached a record speed. The scientists, from the University of Washington in Seattle and the German Aerospace Center DLR, say the speeding up in 2013 was 30 to 50 percent higher than previous summers. The scientists analysed satellite images taken every 11 days from early 2009 to spring 2013. Satellite technology plays a key role in observing the ice. Two German radar satellites TerraSAR-X und TanDEM-X provide high resolution data that facilitates precise calculations, according to DLR. One of the authors, Dana Floricioiu from the DLR Earth Observation Center in Oberpfaffenhofen, told journalists it had been striking to see how much the glacier was changing within a very short time.
The researchers found that the glacier’s average speed peaked at 46 metres per day during the summer of 2012. This is the fastest ever recorded for a glacier in Greenland or Antarctica. The big surges take place in summer, but the researchers say the average annual speed of the glacier over the last two years is almost three times what was measured in the 1990s. It is retreating by around 17 kilometres per year. The scientists say these speeds were achieved “as the glacier terminus appears to have retreated to the bottom of an over-deepened basin with a depth of around 1300 m below sea level. The terminus is likely to reach the deepest section of the trough within a few decades, after which it could rapidly retreat to the shallower regions some 50 km farther upstream, potentially by the end of this century”.
The huge volume of ice going into the sea from the Sermeq Kujalleq glacier is already influencing sea level. The glacier drains around 6 percent of the massive Greenland ice sheet Scientists estimate it added about 1 millimetre to global sea levels from 2000 to 2010. The increased speed of the discharge will exacerbate this further.Badnews for people in low-lying coastal areas around the globe. And this is not the only Greenland glacier melting increasingly.
Coming back to the subject of disaster-preparedness – this glacier is thought to be the source of the iceberg that sank the Titanic in 1912. The Arctic Institute’s scenario indicates that an accident like the “Costa Concordia”, which happened in an easily accessible region with no ice or dangerous weather conditions, would have devastating consequences if it happened, say, off the coast of Ilulissat. Search and rescue, accommodation and medical treatment, lack of transport facilities, poor communications infrastructure, no adequate oil spill response technology for icy waters…. food for thought for companies looking to profit from the changing climate of the Arctic – and the governments that should be responsible for protecting humans, wildlife and that beautiful but fragile Arctic ecosystem.
DateFebruary 6, 2014 | 12:43 pm