Search Results for Tag: ice
Cloudy skies speed up Greenland melt
With Greenland known to be one of the main contributors to global sea level rise, mainly through increased meltwater runoff, it is hardly surprising that there is increasing and widespread scientific interest in finding out exactly what factors influence the melting and to what extent. Approximately half of Greenland’s current annual mass loss is attributed to runoff from surface melt.
In my last Ice Blog post, I looked at a study showing that recent atmospheric warming is reducing the ability of some layers of the Greenland ice sheet to store meltwater. That, in turn, can mean runoff is released into the ocean faster than previously assumed, rushing down a kind of icy chute.
Clouds as a night-time warmer
This week, a study led by the University of Leuven in Belgium was published in Nature Communications that suggests that clouds are playing a greater role in this whole process than previously thought. The study concludes that clouds could be enhancing meltwater runoff by about a third relative to clear skies. The scientists used a combination of satellite observations, ground observations, climate model data and snow model simulations.
The impact is not just because the radiative effect of the clouds directly increases surface melt, but because the clouds actually reduce meltwater refreezing at night. They trap heat like a kind of blanket.
Tristan L’Ecuyer, professor in the Department of Atmospheric and Oceanic Sciences at the University of Wisconsin-Madison and co author of the study, is quoted on the phys. Org science website as saying we could be dealing with another foot of sea level rise around the world over the next 80 years. “Parts of Miami and New York City are less than two feet above sea level; another foot of sea level rise and suddenly you have water in the city”, he warns.
L’Ecuyer stresses that clouds are still not adequately accounted for in climate models. He also stresses that climate models have not kept pace with the rate of melting actually observed on the Greenland ice Sheet.
Viewing clouds from above
Improved satellite coverage is improving the situation. L’Eciyer is affiliated with the UW-Madison Space Science and Engineering Center, a pioneer institute in satellite meteorology. Within the last 10 years, NASA has launched two satellites which, L’Ecuyer says, have changed our view of what clouds look like around the planet. He used “X-ray images” of Greenland’s clouds taken by CloudSat and CALIPSP between 2007 and 2010 to determine the structure of clouds, how high they were in the atmosphere, their vertical thickness and whether they were composed of ice or liquid. The Belgian team combined this data with ground-based observations, snow model simulations and climate model data to map the net effect of clouds. This indicated that cloud cover prevents ice that melts in the daytime sunlight from refreezing at night. That, in turn, flows off as meltwater.
The lead author of the study, Kristof Van Tricht from the University of Leuven, who spent six weeks in Madison last year working with L’Ecuyer, uses the sponge image to describe the snowpack. “At night, clear skies make a large amount of meltwater in the sponge refreeze. When the sky is overcast, by contrast, the temperature remains too high and only some of the water refreezes. As a result, the sponge is saturated more quickly and excess meltwater drains away”.
Clouds can cool the earth’s surface by reflecting sunlight back into space. Or they can trap heat like a blanket. On Greenland, scientists agree that clouds primarily act to trap heat.
As with so many climate phenomena, clouds can both affect the climate, and be changed by it. While on the one hand cloud cover can lead to more warming and more meltwater, the resulting effect on the ice sheet can, in turn, affect the cloud cover itself.
The scientists hope studies like this one, making use of advanced satellite technology, can help make future climate models become more accurate by taking this into account. To date, different models disagree on how clouds affect the largest body of ice and so freshwater in the northern hemisphere.
DateJanuary 15, 2016 | 4:22 pm
Greenland ice a speedy chute to rising seas?
As I checked through the news agencies to keep tabs on what’s been happening with Greenland as 2016 kicks off, the only agency piece I came across is a German story (on AFPD) on how climate change is apparently bringing the world’s biggest island an “economic upswing”. New fish species off the coast, better conditions for agriculture and exportable powdered rock from retreating glaciers are listed amongst the benefits.
No mention of a study published in Nature Climate Change this week showing that recent atmospheric warming – especially the exceptional summers in 2010 and 2012 – are reducing the ability of some layers of the giant ice sheet to store meltwater. That, in turn, can mean runoff is released into the ocean faster than previously assumed, rushing down a kind of icy chute. Clearly, this has considerable implications for global sea level rise.
Approximately half of Greenland’s current annual mass loss is attributed to runoff from surface melt. At higher elevations, the melt does not necessarily equal runoff, because meltwater can refreeze in the porous snow and firn near the surface. Horst Machguth from the Geological Survey of Denmark and Greenland, the lead author of the study, explains the background in a news release by CIRES, the Cooperative Institute for Research on Environment Sciences, Boulder Colorado: “The near-surface of the large ice sheet interior is comprised of snow that is slowly being converted into glacier ice. This porous firn layer can be up to 80 m thick,” he writes. Recent studies indicated that this firn is an important buffer against contributing to sea level rise for decades to come, because it absorbs and stores the meltwater like a sponge, refreezing it to form ice layers as it percolates down from the ice sheet surface. But the authors say the new study shows this may not be the case.
After the Greenland Ice Sheet was hit by a series of warm summers, it was unknown how the firn reacted to exceptional amounts of meltwater, says Machgut. The research aimed to clarify whether the firn was indeed capable of retaining the meltwater, or whether the sponge had been “overwhelmed” by all the extra water.
The scientists drilled cores to sample the firn at sites where similar cores had been drilled 15 to 20 years ago. They found that the amount of refrozen ice layers in the firn had increased substantially over the past two decades in many places, but not everywhere. Cores drilled at lower elevations suggested the recent exceptional meltwater amounts had only trickled through to shallow depths within the firn, conglomerating into massive ice layers directly below the ice sheet surface.
“It appears that the firn was overwhelmed by the melt to a degree where so many ice lenses had formed that they started to hinder percolation of further meltwater. Initially small ice lenses grew to form ice layers of several meters in thickness that act as a lid on top of otherwise sponge-like firn. Radar measurements identified that these massive ice lenses were continuous over tens of kilometres,” says Dirk van As, a co-author of the study from the Geological Survey. “Surface meltwater wants to refreeze in firn locally, which it does at higher elevation, but at lower elevations it hits that lid of ice and is forced to stay at the surface where it cumulates.”
Satellite images show that meltwater then formed rivers on the surface flowing towards the margin of the ice sheet.
More data required
“In contrast to storing meltwater in porous firn, this mechanism increases runoff from the ice sheet,” says CIRES researcher Mike MacFerrin, a second author on the study. “This process has not previously been observed in Greenland. The extent of this ice lid capping the ice sheet firn remains unknown. For this reason, the total amount of additional ice sheet runoff associated with this newly observed process cannot yet be quantified.”
The scientists are now combining their core data with radar measurements from NASA, which cover the entire ice sheet. They say similar changes in firn structure have been observed on various ice caps in the neighbouring Canadian Arctic, which indicates the phenomenon could be widespread in Greenland. Only west Greenland was covered by the new study.
The Greenland ice sheet is already a great concern, with the melting ice rate increasing continually as the atmosphere and the oceans warm. As well as contributing to rising sea levels, the increase in runoff from the ice sheet could also result in feedback processes which could lead to even more melt in the future. The water running down the ice sheet can create darker, slushy channels, the scientists say, which can reduce the albedo effect of the ice sheet, its ability to reflect sunlight away from its surface. As more sunlight is absorbed instead of being reflected off, the surface temperature could warm further.
Given the huge significance of the Greenland ice sheet in terms of global sea level rise and its role in the global climate system, the findings of this study deserve a little more attention than being confined to the publications of the scientific communities.
But maybe potatoes from the “ice island” and mackerel and tuna off its snow-tipped coasts make for more striking headlines?
DateJanuary 6, 2016 | 3:09 pm
TagsArctic, CIRES, Climate, firn, Geological Survey of Denmark and Greenland, glaciers, Greenland, ice, Machguth, meltwater, research, science, Sea level, snow, Warming
As 2015 draws to a close, the NOAA report card on the state of the Arctic and a substantial new study on the Greenland ice sheet belie the myth that the Paris climate conference has put us on track for averting the worst climate change impacts. NOAA confirms that the Arctic experienced record air temperatures and a new low in peak ice extent during 2015, and the scientists warn that climate change is having “profound effects” on the entire marine ecosystem and the indigenous communities that rely on it.
DateDecember 18, 2015 | 11:51 am
TagsArctic, Climate, COP21, Emissions, Greenland, Greenpeace, ice, Living Planet, Paris, Renewables, science, sea ice, UN talks, wildlife
Paris: A COP-out for Arctic Peoples?
As I write, the climate negotiations have been extended into Saturday. Same procedure as every year? While I still hope the seemingly never-ending bickering will result in a document which will at least signal the end of the fossil fuels era, I cannot help feeling a sense of sadness and regret, that this is all way too late for the Arctic, as I discussed in the last blog post. And I wonder how all this feels to indigenous folk living in the High North, as they see their traditional lifestyles melting away.
On a recent edition of DW’s Living Planet programme, Lakeidra Chavis reported on the effect of melting permafrost on indigenous communities in Alaska. Chatting to a colleague in between times about the story, she told me how moved she was to hear how skulls had been washed up in a river as the permafrost at a burial site thawed.
Climate change impacts the present, future – and past
I had a kind of déjà vu feeling. Back in 2008, in those early days of the Ice Blog, I travelled out to Point Barrow, the northernmost point in the USA, with archaeologist Anne Jensen. We visited the site where a village had had to be re-located because of coastal erosion, with melting permafrost and dwinding sea ice. She told me how she was called up by distraught locals in the middle of the night and asked to help recover the remains of their ancestors before they were washed into the ocean. My colleague here in Bonn was surprised to hear that I had conducted that interview back in 2008. How could this have been known at that time already, yet so little publicized?
Victims or culprits?
While a lot of attention is focused (and rightly so) on the impacts on developing countries, Asia, Africa, rising sea levels, this is an issue a lot of people know very little about. In an article for Cryopolitics Mia Bennet puts her finger on an interesting aspect of all this. The Arctic indigenous peoples are living in industrialized, developed states. That gives them an interesting status, somewhere between being victims and perpetrators of climate warming.
“A discourse of victimization pervades much Western reporting on the Arctic”, she writes. A lot of people in the region tend to blame countries outside the region for climate change. She quotes a study in Nature Climate Change in which researchers found that emissions from Asian countries are the largest single contributor to Arctic warming. But she notes that gas flaring emissions in Russia and forest fires and gas flaring emissions in the Nordic countries are the second two biggest contributors. And these industries are often supported by locals, not least because of the jobs and prosperity they bring.
This brings me back to some encounters I had during that trip to Alaska in 2008 – and others since, with Inuit people employed in the oil sector. They were reluctant to accept that the industries that provided their livelihoods could ultimately be literally eroding the basis of their cultures. Russia, the USA, Canada, Norway – are all countries involved in oil and gas exploitation. Some northern regions are highly dependent on the industries which are warming the climate.
“And for their part, Arctic countries must realize that reducing emissions begins at home on the region’s heavily polluting oil platforms and gas flaring stacks – not in Paris”, says Mia Bennet.
All up to Paris?
The sad truth is that even the two-degree target – or the 1.5 currently being debated – will not have much of an impact on Arctic warming.
Mia Bennet puts it bluntly. “Regardless of whether a positive or negative outcome is reached in Paris at COP 21, it will not dramatically affect the Arctic.”
A delegation of indigenous leaders from the Arctic countries is in Paris at the talks. Both the Inuit Circumpolar Council and the Saami Council have sent delegates, with the aim of highlighting the consequences of a warming climate for the polar regions.
Council representatives are from three distinct Inuit regions: Canada, the USA and Greenland. The Chukotka region of Russia also has a substantial Inuit population, who are not directly represented in Paris, but belong to the Council. The Saami Council has representatives from Finland, Russia, Norway and Sweden. Both sets of delegates are attending as observers, without voting rights.
In a position paper, Inuit Circumpolar Council Chair Okalik Eegeesiak of Canada stresses the Inuit’s deep concern about the impacts of climate change on their cultural, social and economic health.
She describes the Arctic’s sensitive ecosystem as a “canary in the coal mine for global change”. Following that metaphor, the canary must be close to suffocating.
The Inuit representatives in Paris are appealing for stronger measures to keep global temperature rise below 1.5 degrees C. They stress that the land and sea sustain their culture and wildlife, “on which we depend for food security, daily nutrition and overall cultural integrity”.
But ultimately, in a world where altruism seldom plays a part, it may be their other argument – the role of the Arctic in influencing the global climate system – that convinces negotiators of the need to work against global warming. With increasing knowledge and awareness of the extent to which the Arctic influences global processes and thus weather and climate all over the globe, the willingness to take measures to prevent further deterioration of the cryosphere is likely to increase. Whether it will be in time is another question. Any negotiator in Paris who has taken a brief moment off to read this – remember, we are not talking about a remote region with a small population. We are all in this together.
DateDecember 11, 2015 | 2:51 pm
TagsAlaska, Arctic, Barrow, Climate, Climate Change College, COP21, Greenland, Greenpeace, ice, Oil, Paris, permafrost, sea ice, snow, UN talks, Warming
Can Paris avert climate threat to cryosphere?
To those of us who work on polar subjects, there is no question about the relevance of the cryosphere to the annual UN climate negotiations. But in the run-up to the annual mega-event – especially in a year dubbed by some to be the “last chance” for climate – it was not easy to get attention for the Arctic, Antarctic and high-altitude peaks and glaciers of the world.
I had a discussion with some of my colleagues who focus on Africa and Asia. With problems like political unrest, wars, famine and drought to cope with, the fate of polar bears, one told me, is completely irrelevant.
You could say this colleague is suffering from a kind of tunnel vision. But it also prompts me to wonder whether the way we communicate the threat of climate change is partly to blame.
Not just polar bears
Earlier this week I read about a study indicating that people were more likely to donate to campaigns which focus on people, on social injustice rather than on conservation and environmental degradation. Somehow, we journalists have to make the connection between the two. When you remind people that increasing sea levels caused to a large extent by changes in our ice sheets pose a huge threat not only to small island states but to many of the world’s megacities, the cryosphere takes on a new relevance. Not to mention the fact that the ice, snow and permafrost covered regions of our planet play a major role in regulating the world’s climate and water supplies.
One organization that works to bring the attention of delegates at the UN climate talks to our icy regions is the International Cryosphere Climate Initiative, ICCI. In time for this year’s COP21, it commissioned a report from leading scientists: “Thresholds and closing windows. Risks of irreversible cryosphere climate change”. The report summarizes the levels of risk in five key areas: ice sheets loss and related sea-level rise, polar ocean acidification, land glacier loss, permafrost melt, and the loss of Arctic summer sea ice. The report is based on the last IPCC assessment plus literature published in the three years since.
Bringing the ice closer
Pam Pearson is the director and founder of ICCI. I have interviewed her on various occasions, including during visits she made to Bonn, the home of the UNFCCC, to brief delegates. This time we were not able to meet in person, but we have been in Email contact. I asked her how difficult it was to arouse interest within the negotiations at the moment, with so much going on. She told me it was difficult mainly because very few people globally actually live near cryosphere.
“Yet we are all deeply connected to these regions, because of their role in the Earth climate system — especially through sea-level rise, water resources from land glaciers, and permafrost release that will make it harder to meet carbon budgets. “
The Arctic, parts of Antarctica and many mountain regions have already warmed two to three times faster than the rest of the planet, between 2 and 3.5 degrees Celsius up on pre-industrial levels. Climate change is also affecting high altitude areas such as the Himalayas and the Andes, where seasonal glacier melt provides water for drinking and irrigation, especially in dry periods.
When the outside risk becomes the norm
The changes are far more extreme than those forecast in even the most pessimistic scenarios of a few years ago. In the IPCC’s 2007 Fourth Assessment, the outer extreme estimate for sea level rise (mostly from glacier ice melt) was about one meter by the end of this century. Today, the experts say even if we could halt warming now, it would be impossible to avoid sea-level rise of one meter from glaciers, ice sheets and the natural expansion of warming waters, within the next two hundred years. Most scientists also agree that the West Antarctic ice sheet has already been destabilized by warming to the extent where this probably cannot be halted, which will increase sea level further.
Pearson used to be a climate negotiator herself, so she knows the pressures and constraints. She told me that while participants in the climate conferences were broadly aware of issues like ice melt at the poles and on high-altitude glaciers, they tended to lack awareness of two key aspects:
“First, that we have already passed, or are close to passing temperature levels that will cause certain processes to begin; and second, that some of these processes cannot be stopped once they get started.”
She says a “sense of urgency” is lacking, and stresses that although some of the most damaging consequences will only occur in hundreds or even thousands of years, they will be determined by our actions or inactions in the coming few decades. That includes the 2020-30 commitment period that is the focus of the agreement being worked on in Paris Pearson stresses.
The cryosphere needs more ambitious targets
The report analyses the implications of the INDCs, or current pledges put on the table by the countries of the world for the Paris climate talks. The scientists come to the conclusion that these will not be enough to prevent the onset of many irreversible cryosphere processes.
Even the two-degree pathway agreed by the international community translates into a peak cryosphere temperature of between 4 and 7 degrees above pre-industrial levels, according to the ice experts. Yet the UN and others say current commitments would lead to global temperatures 2.7 to 3.5 degrees Celsius above pre-industrial levels by 2100, rising later to between 3.4 and 4.2 degrees. The peak in global carbon emissions would occur well after 2050. The associated temperatures would trigger permanent changes in our ice and snow that cannot be reversed, including the complete loss of most mountain glaciers, the complete loss of portions of West Antarctica’s Ice Sheets and parts of Greenland. This would ultimately equate to an unstoppable sea level rise of a minimum four to ten meters, the scientists find.
In addition, the increase of CO2 being absorbed in the Southern Ocean around Antarctica and the Arctic Ocean is turning the water more acidic and so threatening fisheries, marine ecosystems and species.
Another of the key issues which is often neglected is that of permafrost. About a quarter of the Northern Hemisphere’s land area contains ground that remains frozen throughout the year. This holds vast amounts of ancient organic carbon. So when it thaws, carbon dioxide and methane are released, which fuel further warming. Even a temperature rise of 1.5 degrees could result in a 30% loss of near-surface permafrost. This would mean 50 Gigatonnes of additional carbon emissions by 2100. Given that the total carbon budget allocated to a two-degree temperature rise is only 275 Gigatonnes, that would be a huge factor. The ICCI experts say this thaw would not be reversible, except on geological time scales.
Dwindling Arctic sea ice
Arctic summer sea ice has declined rapidly, especially since 2000. Only about half the sea ice survives the summer today compared to 1950. This is “both a result and a cause of overall Arctic and global warming”, according to the ICCI report. White ice reflects heat into space. When it melts, it is replaced by dark water, which absorbs the heat, exacerbating warming further.
The Arctic sea ice has a tempering effect on global temperatures and weather patterns. It would only be possible to reverse the disappearance of the ice in summer with a return to regular global temperatures of 1 to 2 degrees above pre-industrial times, according to the report.
Andes and Himalayas
Receding mountain glaciers in the European Alps, American Rockies, Andes and East Africa were among the first identified, visible impacts of climate change, originally from natural factors. Sometime in the past 50 years, anthropogenic climate change surpassed natural warming as the main driver of retreat, and caused about two-thirds of glacier melt between 1991 and 2010, according to the ICCI report.
Glaciers are important to nearby communities as a source of water for drinking or irrigation. Some are especially important in dry seasons, heat waves and droughts. Melting glaciers provide an increase in water for a limited time. But ultimately, the lack of water could make traditional agriculture impossible in some regions of the Himalayas or the Andes.
So unless governments in Paris move fast to increase their commitments and bring the deadlines for emissions reductions forward, the windows to prevent some of these irreversible impacts on the polar and high mountain regions may close during the 2020-2030 commitment period.
It is not too late
However, the scientists stress that it is still possible to reduce emissions to the required level, if the political will becomes strong enough. Pam Pearson says the world has to get onto the path towards the two-degree goal now. Like many experts, she says this in itself is risky enough for the cryosphere, and a 1.5 degree pathway would be safer:
“So if countries indeed agree with UNFCCC chief Christiana Figueres’ proposal to meet every five years to strengthen INDCs, moving onto these lower-temperature pathways should be a concrete goal. Perhaps even more important, I understand the French COP presidency may be aiming at strengthening actions PRIOR to 2020, in the 2015-2020 period. This kind of earlier action is really vital, and will make the job of keeping temperatures as low as possible easier”
Without much more ambitious targets, the ICCI study concludes it will be “close to impossible” to avoid rapid deterioration of our snow and ice regions.
The challenge is to make the delegates in Paris understand that that does not just mean cosmetic changes to distant parts of the globe, but that it would also destabilize the global climate, displace millions of people and endanger food and water supplies in many parts of the world.
DateDecember 1, 2015 | 3:00 pm
TagsAntarctic, Arctic, Climate, CO2, COP21, Emissions, glaciers, Greenland, ice, Media, ocean acidification, Paris, polar bears, science, Sea level, snow, UN talks