EurekAlert, 13 Oct 16 Extreme Antarctica ice melt provides glimpse of ecosystem response to global climate change
PORTLAND STATE UNIVERSITY New research led by Portland State University glacier scientist Andrew Fountain reveals how a single warming event in Antarctica may be an indication of future ecosystem changes.
In the scientific paper, “The Impact of a Large-scale Climate Event on Antarctic Ecosystem Processes,” published in a special section Thursday in Bioscience, Fountain and his team detail the climate event and summarize the cascading ecological consequences over the last 15 years caused by a single season of intense melting in Antarctica between 2001 and 2002……..https://www.eurekalert.org/pub_releases/2016-10/psu-cfa101216.php
Record high to record low: what on earth is happening to Antarctica’s sea ice? https://theconversation.com/record-high-to-record-low-what-on-earth-is-happening-to-antarcticas-sea-ice-66114September 29, 2016 2016 continues to be a momentous year for Australia’s climate, on track to be the new hottest year on record.
To our south, Antarctica has also just broken a new climate record, with record low winter sea ice. After a peak of 18.5 million square kilometres in late August, sea ice began retreating about a month ahead of schedule and has been setting daily low records through most of September.
It may not seem unusual in a warming world to hear that Antarctica’s sea ice – the ice that forms each winter as the surface layer of the ocean freezes – is reducing. But this year’s record low comes hot on the heels ofrecord high sea ice just two years ago. Overall, Antarctica’s sea ice has been growing, not shrinking.
So how should we interpret this apparent backflip? In our paper published today in Nature Climate Change we review the latest science on Antarctica’s climate, and why it seems so confusing.
First up, Antarctic climate records are seriously short.
The International Geophysical Year in 1957/58 marked the start of many sustained scientific efforts in Antarctica, including regular weather readings at research bases. These bases are mostly found on the more accessible parts of Antarctica’s coast, and so the network – while incredibly valuable – leaves vast areas of the continent and surrounding oceans without any data.
In the end, it took the arrival of satellite monitoring in the 1979 to deliver surface climate information covering all of Antarctica and the Southern Ocean. What scientists have observed since has been surprising.
Overall, Antarctica’s sea ice zone has expanded. This is most notable in the Ross Sea, and has brought increasing challenges for ship-based access to Antarctica’s coastal research stations. Even with the record low in Antarctic sea ice this year, the overall trend since 1979 is still towards sea ice expansion.
The surface ocean around Antarctica has also mostly been cooling. This cooling masks a much more ominous change deeper down in the ocean, particularly near the West Antarctic Ice Sheet and the Totten glacier in East Antarctica. In these regions, worrying rates of subsurface ocean warming have been detected up against the base of ice sheets. There are real fears that subsurface melting could destabilise ice sheets, accelerating future global sea level rise.
In the atmosphere we see that some parts of the Antarctic Peninsula and West Antarctica are experiencing rapid warming, despite average Antarctic temperatures not changing that much yet.
In a rapidly warming world these Antarctic climate trends are – at face value – counterintuitive. They also go against many of our climate model simulations, which, for example, predict that Antarctica’s sea ice should be in decline.
Winds of change
The problem we face in Antarctica is that the climate varies hugely from year to year, as typified by the enormous swing in Antarctica sea ice over the past two years.
This means 37 years of Antarctic surface measurements are simply not enough to detect the signal of human-caused climate change. Climate models tell us we may need to monitor Antarctica closely until 2100 before we can confidently identify the expected long-term decline of Antarctica’s sea ice.
In short, Antarctica’s climate remains a puzzle, and we are currently trying to see the picture with most of the pieces still missing.
But one piece of the puzzle is clear. Across all lines of evidence a picture of dramatically changing Southern Ocean westerly winds has emerged. Rising greenhouse gases and ozone depletion are forcing the westerlies closer to Antarctica, and robbing southern parts of Australia of vital winter rain.
The changing westerlies may also help explain the seemingly unusual changes happening elsewhere in Antarctica.
The expansion of sea ice, particularly in the Ross Sea, may be due to the strengthened westerlies pushing colder Antarctic surface water northwards. And stronger westerlies may isolate Antarctica from the warmer subtropics, inhibiting continent-scale warming. These plausible explanations remain difficult to prove with the records currently available to scientists.
Australia’s unique climate position
The combination of Antarctica’s dynamic climate system, its short observational records, and its potential to cause costly heatwaves, drought and sea-level rise in Australia, mean that we can’t afford to stifle fundamental research in our own backyard.
Our efforts to better understand, measure and predict Antarctic climate were threatened this year by funding cuts to Australia’s iconic climate research facilities at the CSIRO. CSIRO has provided the backbone of Australia’s Southern Ocean measurements. As our new paper shows, the job is far from done.
A recent move to close Macquarie Island research station to year-round personnel would also have seriously impacted the continuity of weather observations in a region where our records are still far too short. Thankfully, this decision has since been reversed.
But it isn’t all bad news. In 2016, the federal government announced new long-term funding in Antarctic logistics, arresting the persistent decline in funding of Antarctic and Southern Ocean research.
The nearly A$2 billion in new investment includes a new Australian icebreaking ship to replace the ageing Aurora Australis. This will bring a greater capacity for Southern Ocean research and the capability to push further into Antarctica’s sea ice zone.
Whatever the long-term trends in sea ice hold it is certain that the large year-to-year swings of Antarctica’s climate will continue to make this a challenging but critical environment for research.
They may be small, but krill—tiny, shrimp-like creatures—play a big role in the Antarctic food chain. As climate change warms the Southern Ocean and alters sea ice patterns, though, the area of Antarctic water suitable for krill to hatch and grow could drop precipitously, a new study finds.
Most Antarctic krill are found in an area from the Weddell Sea to the waters around the Antarctic Peninsula, the finger of land that juts up toward South America. They serve as an important source of food for various species of whales, seals and penguins. While those animals find other food sources during lean years, it is unclear if those alternate sources are sustainable long-term.
Over the past 40 years, populations of adult Antarctic krill have declined by 70 to 80 percent in those areas, though researchers debate whether that drop is due to the effects of climate change, a rebound in whale populations after the end of commercial whaling or some combination of those pressures.
Because of its key role in the regional food chain, scientists are concerned about the impacts that future climate change may have on the krill population and the larger Antarctic ecosystem.
In the new study published in the journal Geophysical Research Letters, Andrea Piñones and Alexey Fedorov examined how expected changes in ocean temperatures and sea ice coverage might affect krill during their earliest life stages when they are most vulnerable to environmental conditions.
Krill has a complex, regimented life cycle that requires a delicate balance of conditions. …..
While warmer ocean temperatures help the krill hatch faster, declines in sea ice area, delayed sea ice formation, and a drop in phytoplankton populations meant that overall, the habitat suitable for young krill could decline by up to 80 percent, they found………http://www.scientificamerican.com/article/krill-are-disappearing-from-antarctic-waters/
Earth’s ability to absorb CO2 reduced by global warming, Antarctic study finds http://www.abc.net.au/news/2016-07-29/global-warming-reduces-earth-co2-absorption-arctic-study/7673032 By Stephanie Smail Global warming reduces the amount of carbon dioxide the earth can absorb, which could amplify climate change, landmark research in Antarctica has revealed.
CSIRO researchers extracted ice bubbles in pre-industrial polar ice to measure the planet’s sensitivity to changes in temperature.
They found that for every degree Celsius of global temperature rise, the equivalent of 20 parts per million less CO2 is stored by the land biosphere.
CSIRO principle research scientist Dr David Etheridge said the research confirmed the relationship for the first time and revealed how it impacted the cycles of carbon between land, ocean, and the atmosphere.
“That’s useful to know. It’s a bit concerning because it’s going to amplify the climate change, but it’s good news in a way because it can be used in modelling.”
The research team used ice core samples from the Australian Antarctic Program’s unique Law Dome site, together with ice cores from the British Antarctic Survey.
The study focused on CO2 changes preserved in ice before, during, and after a naturally-cool period known as the Little Ice Age (1500 to 1750 AD).
“It gives global planners something to work with, to help estimate what CO2 emissions are allowable to limit global warming to one and a half or two degrees Celsius,” Dr Etheridge said.
The finding is a result of a collaboration between CSIRO, the Seconda Universita di Napoli, University of Melbourne, British Antarctic Survey, University of East Anglia, Australian Antarctic Division, University of Tasmania, and the Australian Nuclear Science and Technology Organisation.
The world decided to take an action on these chemicals, and the planet is responding as we expected. People can take heart by seeing that our choices can help the environment.”
Hole in the ozone layer is finally ‘healing’ ABC Science Dani Cooper 1 July 16 The ozone hole over Antarctica is finally “healing” almost 30 years after the world banned the chemicals responsible for its creation, researchers say.
- The ozone hole fluctuates from year to year due to natural factors
- Last year volcanic eruptions increased the hole to its largest size ever
- But now there is evidence it is finally on a downward trend
- This is 30 years after the decision to ban the chemicals that created it
According to the latest measurements, the ozone hole above the Antarctic is now smaller than it was around the year 2000, by about 4 million square kilometres.
However, renowned ozone hole expert Professor Susan Solomon, from the Massachusetts Institute of Technology, said the hole still averages about 17 million square kilometres in size.
“It isn’t completely healed, but it’s better than the 21 million we had around 2000,” she said. The surprise finding comes just a year after scientists reported the ozone hole was the biggest it had ever been.
However, Professor Solomon and colleagues have pinpointed the growth in the hole in 2015 to the eruption of the Calbuco volcano in Chile, which increased particles in the Antarctic stratosphere.
“The reason we have an ozone hole is because Antarctica is so cold that clouds form in the Antarctic stratosphere, and chlorine can react on the surfaces of those cloud particles,” Professor Solomon said.
“Volcanic particles are one thing that can serve as the ‘seed corn’ for those clouds, so a volcanic eruption will increase the clouds, and slow down the healing.”
Legacy of past pollutionThe ozone layer plays a critical role in protecting life on Earth by absorbing ultra-violet radiation from the sun. UV radiation is linked to skin cancer, genetic damage and immune system suppression in living organisms.
It is also linked to reduced productivity in agricultural crops and the food chain.
In 1987 there was an international decision to phase out the use of chlorine-containing gases called chlorofluorocarbons (CFCs), which were identified as being the main cause of depletion of the ozone layer.
But Professor Solomon said the chemicals that had led to the ozone hole had a life span of between 50 to 100 years in the atmosphere.
“These molecules have long lifetimes in our atmosphere so even though we aren’t making them anymore there is still a lot in the atmosphere,” she said.
“It will be many years before the hole closes completely, but we can now see signs that it is not only not getting worse, but actually starting to get better.”
Professor Solomon said the discovery, published today in Science, lent hope for the fight against climate change.
“The ozone example shows that when people engage with environmental problems, policymakers have a basis for making choices,” she said.
“The world decided to take an action on these chemicals, and the planet is responding as we expected. People can take heart by seeing that our choices can help the environment.”………http://www.abc.net.au/news/2016-07-01/hole-in-the-ozone-layer-is-finally-healing/7556416
Scientists Are Watching in Horror as Ice Collapses Everything we learn about ice shows that it is disturbingly fragile, even in Antarctica. National Geographic, By Douglas Fox APRIL 12, 2016 “……..The catastrophic collapse of Larsen A and several other ice shelves along the Antarctic Peninsula has yielded important lessons about the vulnerability of Antarctica’s ice sheets to a warming climate. A new analysis of ice sheet instability, published March 31 in Nature, took the public by surprise when it projected that global sea level might rise six feet by 2100, and as much as 40 to 50 feet by the year 2500. (Read “Why the New Sea Level Alarm Can’t Be Ignored.”) That study seemed to double, overnight, the amount of sea level rise that can be expected. But many glacial scientists weren’t surprised. The new estimate is based on insights that have emerged slowly, over 20 years, in the aftermath of these ice shelf collapses.
The Aftermath of an Ice Shelf Collapse
Explore the fjords along the northeastern Antarctic Peninsula today, and it’s easy to find landscapes that look scarred even to the casual observer. …..
The glacier, now absent, had retreated several miles into its fjord. The fjord used to hold 2,000 feet (600 meters) of ice. Now it held 2,000 feet of seawater instead.
The aftermath of an ice shelf collapse is obvious in Sjögren’s fjord. When the ice shelf in front of Sjögren disintegrated in 1995, it removed the buttress that stabilized the glacier. The glacier started sliding into the sea at twice its original speed. Sjögren erupted in crevasses and thinned by several hundred feet as it stretched. After a few years, the glacier had retreated miles into its fjord as icebergs splintered off the glacier’s front faster than the ice could flow forward…….
Every ice shelf that disintegrated along the Antarctic Peninsula has shown the same pattern: summer melting of its top layers, winter refreezing of those top layers into icy crusts able to hold large melt ponds, and the re-exposure of long-buried crevasses.
For all of these ice shelves, the moment of death occurred suddenly. Each collapse began when water from the melt ponds drained into the crevasses. The weight of the water drove the cracks deeper—like a wedge, says Ted Scambos, a glaciologist with the National Snow and Ice Data Center at the University of Colorado in Boulder, who discovered the process. These fluid wedges eventually broke through the bottom of the ice shelf, calving off one iceberg, then another and another—a process called hydrofracturing that can devour an ice shelf nearly the size of Rhode Island in a matter of hours or days……..
Ice loss may have begun at a narrow beachhead in Antarctica, at the north end of the Antarctic Peninsula, but it has expanded on multiple fronts, as new regions of ice come into play every several years. As warm summer temperatures push farther south, so will the problems of melt ponding, ice shelf disintegration, and ice cliff collapse, which drive the rapid retreat of ice. (Read more about how calving causes mini-tsunamis daily in Antarctica.)
Scattered melt ponds already appear on some of the ice shelves that surround the Antarctic mainland, much farther south than any that have collapsed so far. The amount of ice lost each year from all of Antarctica’s ice shelves has increased 12-fold between 1994 and 2012.
Aside from warm air, the fringes of Antarctica’s ice are under assault from another source—warming ocean currents that melt the undersides of ice shelves. (Read more about research on what climate change will mean for whales.)……..http://news.nationalgeographic.com/2016/04/160412-ice-sheet-collapse-antarctica-sea-level-rise/
Ice melt studies say we underestimate sea level rise, Independent Australia Peter Boyer 11 April 2016, Are melting polar ice sheets as stable as we think, or have we missed something? If a couple of new ice studies are only partly right, we face massive disruption from sea level rise within decades.
SCIENTIFIC DEBATE about this has picked up in the wake of the March publication of two major research papers by scientists from the U.S., France, Germany and China.
A paper by James Hansen and 18 other climatologists in the open-access science journal Atmospheric Chemistry and Physics, examined ancient climate change to assess how that compares with today’s melting of Greenland and Antarctic ice sheets.
It argues that during this century, ice sheet meltwater spreading over parts of the Southern Ocean and the North Atlantic will increase the temperature variation between these cooler parts and warming regions, resulting in more violent storms.
The meltwater layer also acts as a transparent lid on warming ocean waters undermining polar ice sheets sitting on bedrock below sea level. The paper’s startling prediction is that consequent disintegration could bring several metres of sea level rise within 150 years and possibly by 2070.
A paper published last week in the science journal Nature, also examining past rapid changes, looked at how the Antarctic ice sheet might react to warming of atmosphere as well as ocean, and reached similarly disturbing conclusions.
Their modelling showed that if today’s high carbon emissions continue, warmer air would add to the impact of warming seas. Fracturing ice shelves and coastal cliffs would bring rapid ice loss and contribute ‘more than a metre of sea-level rise by 2100’………https://independentaustralia.net/environment/environment-display/ice-melt-studies-say-we-underestimate-sea-level-rise,8866
Tipping point: how we predict when Antarctica’s melting ice sheets will flood the seas https://theconversation.com/tipping-point-how-we-predict-when-antarcticas-melting-ice-sheets-will-flood-the-seas-56125 March 14, 2016 Antarctica is already feeling the heat of climate change, with rapid melting and retreat of glaciers over recent decades.
A recent article on The Conversation raised the concept of “climate tipping points”: thresholds in the climate system that, once breached, lead to substantial and irreversible change.
Such a climate tipping point may occur as a result of the increasingly rapid decline of the Antarctic ice sheets, leading to a rapid rise in sea levels. But what is this threshold? And when will we reach it?
What does the tipping point look like? The Antarctic ice sheet is a large mass of ice, up to 4 km thick in some places, and is grounded on bedrock. Ice generally flows from the interior of the continent towards the margins, speeding up as it goes.
Where the ice sheet meets the ocean, large sections of connected ice – ice shelves – begin to float. These eventually melt from the base or calve off as icebergs. The whole sheet is replenished by accumulating snowfall.
Floating ice shelves act like a cork in a wine bottle, slowing down the ice sheet as it flows towards the oceans. If ice shelves are removed from the system, the ice sheet will rapidly accelerate towards the ocean, bringing about further ice mass loss.
A tipping point occurs if too much of the ice shelf is lost. In some glaciers, this may spark irreversible retreat.
Where is the tipping point?
One way to identify a tipping point involves figuring out how much shelf ice Antarctica can lose, and from where, without changing the overall ice flow substantially.
A recent study found that 13.4% of Antarctic shelf ice – distributed regionally across the continent – does not play an active role in ice flow. But if this “safety band” were removed, it would result in significant acceleration of the ice sheet.
Antarctic ice shelves have been thinning at an overall rate of about 300 cubic km per year between 2003 and 2012 and are projected to thin even further over the 21st century. This thinning will move Antarctic ice shelves towards a tipping point, where irreversible collapse of the ice shelf and increase in sea levels may follow.
How do we predict when will it happen?
Some areas of West Antarctica may be already close to the tipping point. For example, ice shelves along the coast of the Amundsen and Bellingshausen Seas are the most rapidly thinning and have the smallest “safety bands” of all Antarctic ice shelves.
To predict when the “safety band” of ice might be lost, we need to project changes into the future. This requires better understanding of processes that remove ice from the ice sheet, such as melting at the base of ice shelves and iceberg calving.
Melting beneath ice shelves is the main source of Antarctic ice loss. It is driven by contact between warmer sea waters and the underside of ice shelves.
To figure out how much ice will be lost in the future requires knowledge of how quickly the oceans are warming, where these warmer waters will flow, and the role of the atmosphere in modulating these interactions. That’s a complex task that requires computer modelling.
Predicting how quickly ice shelves break up and form icebergs is less well understood and is currently one of the biggest uncertainties in future Antarctic mass loss. Much of the ice lost when icebergs calve occurs in the sporadic release of extremely large icebergs, which can be tens or even hundreds of kilometres across.
It is difficult to predict precisely when and how often large icebergs will break off. Models that can reproduce this behaviour are still being developed.
Scientists are actively researching these areas by developing models of ice sheets and oceans, as well as studying the processes that drive mass loss from Antarctica. These investigations need to combine long-term observations with models: model simulations can then be evaluated and improved, making the science stronger.
The link between ice sheets, oceans, sea ice and atmosphere is one of the least understood, but most important factors in Antarctica’s tipping point. Understanding it better will help us project how much sea levels will rise, and ultimately how we can adapt.
Ozone hole over Antarctica expands to near-record levels, now four times size of Australia, ABC News The World Today , 3 Nov 15 By Lucy Carter The hole in the ozone layer over Antarctica has expanded to near-record levels this year, covering an area almost four times the size of Australia.
Scientists from the UN said the increase was due to colder-than-usual temperatures, rather than any extra damage being done to the Earth’s protective layer.
But that could still mean extra UV radiation and the risk of more people getting sunburnt in Australia’s southern states this summer.
The hole in the ozone layer above Antarctica has been carefully monitored for over 30 years.
According to atmospheric scientist Professor David Karoly from the University of Melbourne, its size fluctuates greatly when it emerges each spring. “Each springtime over the last now nearly 35 years, there’s been a depletion of stratospheric ozone over Antarctica primarily due to two really important factors,” he said.
“It’s the increase in ozone-depleting chemicals in the atmosphere and a very special cold conditions that occur in winter and spring over Antarctica which provide a special, if you like, catalytic ozone destruction vessel that allows the ozone to be rapidly deployed by the higher concentrations of chlorofluorocarbons — ozone-depleting chemicals that have occurred in the stratosphere due to human activity.”
The UN’s weather and climate agency said this year’s seasonal ozone hole peaked on October 2, covering an area over Antarctica of 28.2 million square kilometres — close to four times the size of Australia or the size of Russia and Canada combined…….
“We do know that the substances that cause the ozone hole, the chlorines and bromines up there are decreasing … have decreased by about 18 per cent since their peak in the late 1990s, early 2000s,” he said.
Since 1987, gases known to cause ozone depletion have been banned and last year the World Meteorological Organisation reported the first positive signs of “ozone recovery”.
Professor David Karoly from the University of Melbourne said this fluctuation in size was not a long-term concern.
“It makes it harder to then see the long-term improvement, the declining trend in the size of the ozone hole but that is still expected to continue,” he said.
“We expect in the southern hemisphere that the ozone hole will not completely recover for another 40 to 60 years, when it recovers back to pre-1980 levels when the ozone hole was first discovered.”
However, this year’s ozone hole size does have the potential to affect Australians.
“Once the ozone hole does start to break up, air that’s depleted in ozone may be transported over to the southern parts of Australia which can, of course, during those periods increase the amount of UV radiation which in the Earth’s surface,” Mr Krummel said.
“So there could be a tendency for a bit more sunburn. “I would say mostly the southern states is where it is likely to impact……..http://www.abc.net.au/news/2015-10-30/ozone-hole-over-antarctica-expands-to-near-record-levels/6898824
the results leave a narrow opening through which humanity can slip. If temperatures remain within 2C (3.6F), the collapse of the shelves will stabilise and the sheets will remain mostly intact. Sea-level rise from Antarctica would remain within 23cm (9 inches) by 2300.
To achieve this, the authors said the world will have to follow the Intergovernmental Panel on Climate Change’s (IPCC) lowest emissions scenario.This requires global emissions to peak around 2020 and decline to below zero by 2100.
The new study “ultimately confirm[s] the suspicions of earlier glaciologists that the fate of ice shelves largely determines whether Antarctica contributes less than 1 metre or up to 9 metres to long-term sea-level rise”
Antarctic ice sheets face catastrophic collapse without deep emissionscuts, http://www.theguardian.com/environment/2015/oct/14/antarctic-ice-sheets-face-catastrophic-collapse-without-deep-emissions-cuts Guardian, Karl Mathiesen, 15 Oct 15
Study finds that a global temperature increase of 3C would cause ice shelves to disappear, triggering sea-level rise that would continue for thousands of years. A team of researchers has found that steep cuts to emissions during the next decade are the only way to avoid a catastrophic collapse of Antarctic ice sheets and associated sea-level rise that will continue for thousands of years.
The study, published in the journal Nature on Wednesday, found that should the global temperature increase to around 3C (5.4F) above the pre-industrial era then the ice shelves that hold back the giant continental ice sheets would be lost over the next few centuries. Continue reading
New study projects that melting of Antarctic ice shelves will intensify http://www.eurekalert.org/pub_releases/2015-10/whoi-nsp100915.phpWOODS HOLE OCEANOGRAPHIC INSTITUTION New research published today projects a doubling of surface melting of Antarctic ice shelves by 2050 and that by 2100 melting may surpass intensities associated with ice shelf collapse, if greenhouse gas emissions from fossil fuel consumption continue at the present rate.
Ice shelves are the floating extensions of the continent’s massive land-based ice sheets. While the melting or breakup of floating ice shelves does not directly raise sea level, ice shelves do have a “door stop” effect: They slow the flow of ice from glaciers and ice sheets into the ocean, where it melts and raises sea levels.
“Our results illustrate just how rapidly melting in Antarctica can intensify in a warming climate,” said Luke Trusel, lead author and postdoctoral scholar at Woods Hole Oceanographic Institution (WHOI). “This has already occurred in places like the Antarctic Peninsula where we’ve observed warming and abrupt ice shelf collapses in the last few decades. Our model projections show that similar levels of melt may occur across coastal Antarctica near the end of this century, raising concerns about future ice shelf stability.”
The study, published Oct. 12, 2015, in Nature Geoscience, was conducted by Trusel, Clark University Associate Professor of Geography Karen Frey, WHOI scientists Sarah Das and Kristopher Karnauskas, Peter Kuipers Munneke and Michiel R. van den Broeke of the Institute for Marine and Atmospheric Research Utrecht University, and Erik van Meijgaard of the Royal Netherlands Meteorological Institute.
To study how melting evolves over time and to predict future ice sheet melting along the entire Antarctic coastline, the scientists combined satellite observations of ice surface melting with climate model simulations under scenarios of intermediate and high levels of greenhouse gas emissions until the year 2100.
The results indicate a strong potential for the doubling of Antarctica-wide ice sheet surface melting by 2050, under either emissions scenario. However, between 2050 and 2100, the models reveal a significant divergence between the two scenarios. Under the high-emissions climate scenario, by 2100 ice sheet surface melting approaches or exceeds intensities associated with ice shelf collapse in the past. Under the reduced-emissions scenario, there is relatively little increase in ice sheet melting after the doubling in 2050.
“The data presented in this study clearly show that climate policy, and therefore the trajectory of greenhouse gas emissions over the coming century, have an enormous control over the future fate of surface melting of Antarctic ice shelves, which we must consider when assessing their long-term stability and potential indirect contributions to sea level rise,” said Frey.
Funding for the research was provided by NASA, the Doherty Postdoctoral Scholarship Program at WHOI, the Netherlands Earth System Science Centre, the Polar Program of the Netherlands Organization of Scientific Research, and the Dutch Ministry of Infrastructure and the Environment.
The Woods Hole Oceanographic Institution is a private, non-profit organization on Cape Cod, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate a basic understanding of the ocean’s role in the changing global environment. For more information, please visitwww.whoi.edu.
Why scientists are so worried about the ice shelves of Antarctica, WP, By Chelsea Harvey October 12 When it comes to climate change, Antarctica is one of the world’s major places of concern, mostly because of the sheer amount of ice it contains — enough to theoretically cause about 200 feet of sea-level rise if it were all to melt — not that anyone thinks that will happen anytime soon. Still, smaller parts could be destabilized, and understanding how the Antarctic ice sheet will react to future climate change is a big priority for scientists.
One important key to building this understanding is studying Antarctic ice shelves, which are large, floating platforms of ice — sometimes spanning hundreds or thousands of square miles — that form where where an ice sheet meets the ocean.
“They play an incredibly important role in constraining the flow of this land ice into the ocean,” says Luke Trusel, a postdoctoral scholar at the Woods Hole Oceanographic Institution, comparing ice shelves to the “cork in a champagne bottle.” If an ice shelf breaks off, it can unleash a flow of ice into the ocean from the ice sheet behind it, which can contribute to sea-level rise in a major way. Indeed, without ice shelves to provide buttressing, glaciers behind the ice shelves flow faster, pouring more and more ice into the ocean.
In order to get a better grip on how climate change could affect Antarctic ice shelves, Trusel and a group of other researchers conducted a study to see how rising air temperatures might affect surface melting in Antarctica. This is a process that can directly influence the destabilizing of ice shelves.
Past observations have shown that as ice melts on a shelf’s surface, the melted water starts to pool, or “pond,” and trickle down into imperfections in the ice, causing the cracks to deepen and widen — which can eventually cause ice shelves to collapse, unleashing the flow of land ice behind them.
“Increases in air temperature, and surface melt and ponding, has led to the abrupt and catastrophic collapse of a number of ice shelves,” says Trusel, lead author of the study, which was published Monday in Nature Geoscience. These collapses have mostly been observed on the Antarctic Peninsula, where the thinning and retreat of ice shelves has been particularly pronounced, thanks to higher-than-average warming in the area. The concern, though, is that more ice shelves that ring around Antarctica, including its colder regions, will start to give way as temperatures continue to rise and that other more inland parts of Antarctica will then follow suit.
The researchers used models to investigate the potential future impacts of two different climate scenarios: a “business-as-usual” trajectory, in which greenhouse gas emissions continue to rise throughout the century, and a more middle-of-the-road trajectory, in which emissions start declining before mid-century and there’s less associated global warming.
They found that under both scenarios, Antarctic-wide surface melt doubles by the year 2050, with the amount of meltwater produced coming close to 200 gigatons per year (a gigaton is a billion metric tons). This is a troubling finding, said Nerilie Abram, a researcher from the Centre of Excellence for Climate System Science at Australian National University who was not involved with the study, in an e-mail to The Post. But, she said, “I think that the more interesting result is to look at the huge divergence in predicted Antarctic ice melt during the second half of the century.”
After 2050, the projections for the two climate scenarios differ drastically. In the middle-of-the-road scenario, melt doesn’t increase much after mid-century. But in the business-as-usual scenario, melt continues to speed up, eventually hitting a rate of more than 600 gigatons per year by the end of the century.
“The most important results are … that we can see how quickly melting can evolve,” Trusel said. The results suggest that ice shelf surface melting increases exponentially with air temperature……….
One of the most important takeaways from the paper is “how important human action is on the climate of Antarctica,” Trusel added in a follow-up e-mail to The Post. Past observations show that humans have already altered the face of the continent, and the projections suggest that we have the power to continue doing so, he said.
“This shows that we do have a choice in how the Earth changes over the coming century,” said Abram, the researcher from Australian National University. “[We have] the option of a future where many of Antarctica’s ice shelves are still viable if we can curb emissions, compared to a future where many of Antarctica’s remaining ice shelves will probably have been lost if we continue our current emissions trajectory.” http://www.washingtonpost.com/news/energy-environment/wp/2015/10/12/why-scientists-are-worried-about-the-ice-shelves-of-antarctica/
This is quite an old article, but I find it remarkable because, for once, it mentions the enormous cost of security measures needed for small nuclear reactors in remote areas.
That is what is being proposed for Australia – by both the thorium enthusiasts, and the overseas companies desperate to keep the nuclear industry alive by selling small reactors to Australa (or, even more insidiously, by providing them to Australia “for free”, in exchange for South Australia importing radioactive trash, as outlined by nuclear proponent Oscar Archer )
the PM-2A’s purpose was to test whether reactors could be built in remote locations using prefabricated parts.
After the reactor was closed down, the US shipped 7700 cubic metres of radioactive contaminated rock and dirt to California, but passed through Dunedin, with a population of 124,000, the second largest city on New Zealand’s South Island, where it stayed for four days, raising local concerns, the New Zealand news site stuff.co.nz.
Russia has found that the logistics of even finding customers for its ANPP’s outweigh even the logistics of operating the plants. Russia has staked a financial bonanza on prospective orders for the plants, but there are, simply, no takers. And if there were, the logistics of securing such a plant against terrorists or accidents in remote areas would require at least the staff of a stationary plant.
Small-scale US nuclear reactor blamed for spiking cancer rates, casting pall over Russia’s FNPP fetish AMSTERDAM – A small nuclear power plant operated the United States at Antarctica’s McMurdo Sound has been implicated in dozens of cases of an unusual cancer in personnel who worked at or near the station between the years 1964 and 1973, US and New Zealand media have indicated. March 7, 2011 by Bellona Continue reading
Some Antarctic glaciers reached a tipping point in 2009 SARA PHILLIPS ABC Environmen t22 MAY 2015
Antarctic glaciers on the Bellinghausen Sea coast suddenly started melting in 2009.Credit: Alba Martin Espanol (Science)
Antarctic glaciers emptying into the Bellinghausen Sea all suddenly started melting around 2009. Scientists warn the sea level rise could be dramatic.
THE FIRST SIGNS Antarctic glaciers have reached some kind of melting ‘tipping point’ have been noticed by scientists from Europe.
The group of eight scientists, led by Dr Bert Wouters from the University of Bristol used sophisticated satellite measurements of the Antarctic glaciers that empty into the Bellinghausen Sea, on the Southern Antarctic Peninsula which reaches up almost to South America.
Glaciers are in effect, frozen rivers of snowpack, moving incrementally towards the ocean. These glaciers have existed in their current form for at least 5,000 years.
The scientists found that the height of the glaciers had dropped — some by as much as four metres. By analysing years of data, they could rule out the snow becoming more compact or a reduction in snowfall as the cause. This left only one possibility: that the glaciers were sliding faster towards the sea.
“The most likely explanation is that the glaciers have accelerated because the temperature of the ocean water has increased in the area, which we know from measurements. These warm waters will melt the floating ice shelves and the glaciers where they enter the sea from below and cause them to lose more ice,” said Dr Wouters, Marie Curie Research Fellow at the University of Bristol.
As the sea ice holding back the glaciers melts away, the glaciers slide faster into the sea. Last week researchers warned that elsewhere in Antarctica, the Larsen C ice shelf could collapse this century and what remains of the Larsen B ice shelf would be all gone by 2020, the majority of it having collapsed in 2002.
A tipping point
Curiously, the glaciers studied were relatively stable until 2009. After then, Dr Wouters said the glaciers appeared to have reached a “tipping point” with the glaciers studied simultaneously starting to slip into the sea…….http://www.abc.net.au/environment/articles/2015/05/22/4239285.htm
‘Stable’ Antarctic ice sheet may have started collapsing, scientists say, Guardian, Karl Mathiesen, 22 May 15 Southern Antarctic Peninsula ice sheet losing ice 8,500 times the mass of the Great Pyramid of Giza every year, satellite data shows A vast slab of Antarctic ice that was previously stable may have started to collapse, according to new analysis of satellite data.
Research published in the journal Science on Thursday found the Southern Antarctic Peninsula (SAP) ice sheet is losing ice into the ocean at a rate of 56 gigatons each year – about 8,500 times the mass of the Great Pyramid of Giza. This adds around 0.16mm per year to the global sea level.
The sheet’s thickness has remained stable since satellite observations began in 1992. But Professor Jonathan Bamber of Bristol university, who co-authored the study, said that around 2009 it very suddenly began to thin by an average of 42cm each year. Some areas had fallen by up to 4m.
“It hasn’t been going up, it hasn’t been going down – until 2009. Then it just seemed to pass some kind of critical threshold and went over a cliff and it’s been losing mass at a pretty much constant, rather large, rate,” said Bamber……http://www.theguardian.com/environment/2015/may/21/stable-antarctic-ice-sheet-may-have-started-collapsing-scientists-say
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