New analysis: global sea ice suffered major losses in 2016 http://blogs.discovermagazine.com/imageo/2017/01/07/sea-ice-extent-in-2016-at-both-poles-tracked-well-below-average/#.WHMiWtJ97Gj The extent of sea ice globally took major hits during 2016, according to an analysis released yesterday by the National Snow and Ice Data Center.
At both poles, “a wave of new record lows were set for both daily and monthly extent,” according to the analysis.
In recent years, Arctic sea ice has been hit particularly hard.
“It has been so crazy up there, not just this autumn and winter, but it’s a repeat of last autumn and winter too,” says Mark Serreze, director of the NSIDC.
In years past, abnormal warmth and record low sea ice extent tended to occur most frequently during the warmer months of the year. But for the past two years, things have gotten really weird in the colder months.
In 2015, Serreze says, “you had this amazing heat wave, and you got to the melting point at the North Pole on New Years Eve. And we’ve had a repeat this autumn and winter — an absurd heat wave, and sea ice at record lows.”
Lately, the Southern Hemisphere has been getting into the act. “Now, Antarctic sea ice is very, very low,” Serreze says.
From the NSIDC analysis:
Record low monthly extents were set in the Arctic in January, February, April, May, June, October, and November; and in the Antarctic in November and December.
Put the Arctic and the Antarctic together, and you get his time series of daily global sea ice extent, meaning the Arctic plus Antarctic:
As the graph [on original] shows, the global extent of sea ice tracked well below the long-term average for all of 2016. The greatest deviation from average occurred in mid-November, when sea ice globally was 1.50 million square miles below average.
For comparison, that’s an area about 40 percent as large as the entire United States.
The low extent of sea ice globally “is a result of largely separate processes in the two hemispheres,” according to the NSIDC analysis.
For the Arctic, how much might humankind’s emissions of greenhouse gases be contributing to the long-term decline of sea ice? The graph above [on original] , based on data from a study published in the journal Science, “links Arctic sea ice loss to cumulative CO2emissions in the atmosphere through a simple linear relationship,” according to an analysis released by the NSIDC last December. Based on observations from the satellite and pre-satellite era since 1953, as well as climate models, the study found a linear relationship of 3 square meters of sea ice lost per metric ton of CO2 added to the atmosphere.
That’s over the long run. But over a shorter period of time, what can be said? Specifically, how much of the extreme warmth and retraction of sea ice that has been observed in autumn and winter of both 2015 and 2016 can be attributed to humankind’s emissions of greenhouse gases?
“We’re working on it,” Serreze says. “Maybe these are just extreme random events. But I have been looking at the Arctic since 1982, and I have never seen anything like this.”
We’ve seen a lot of commentary on the fact that utility-scale solar power has become the least expensive source of electricity in many places. There is more than that to be found in the data in Lazard’s Levelized Cost of Energy Analysis, Version 10.0, however, and what it tells us is that solar and wind power have benefits apart from the simple facts that their costs are low.
We have always needed a variety of power sources. Conventional baseload power provided by coal-burning and nuclear plants lacks flexibility and is, in fact, a really bad match for grid demand. Baseload generation cannot be ramped up or down as demand changes, and this is one reason why such power plants never provided all of our electricity. There always had to be other, more flexible generating facilities available.
The greatest need for power is often on warm, sunny afternoons, when air conditioners are running in work spaces, stores, and homes, in addition to normal human activities. These have been the times when peaking plants could make their money. With high demand, come the high prices they need to be profitable.
As solar photovoltaics (PV) have come on the market in quantity, however, sunny afternoons suddenly bring the sun as a competing power source. The early evening, after the sun has gone down, is still potentially a time of high demand, when solar power does not cut into the use of fossil-fuel peaking plants. This situation, however, is clearly coming to an end.
According to Lazard, the levelized cost of utility-scale solar power with storage is $92 per megawatt-hour (MWh). This means that solar-plus-storage can be highly competitive, even after dark, with natural gas peaking plants, which have levelized costs ranging from $165 to $217 per MWh. It is even competitive to a degree with gas-powered reciprocating engines, whose costs are from $68 to $101 per MWh.
There is more to this story, however. It happens that wind power is usually strongest when the sun is not shining brightly, and solar power output is often highest when the wind does not blow much. A storage system that is charged by the sun could be charged by the wind when the sun does not shine. This means that a solar-plus-storage system can be made more valuable by storing excess power from wind as needed.
The fact that power from solar-plus-storage is becoming relatively inexpensive makes it likely that the combination will increasingly be used instead of peaking plants using fossil fuels. This will increase production of batteries, and it will increase research and development into storage technologies. And these changes imply further reductions in costs.
The declines in costs of energy storage have already been impressive. Tesla lithium-ion batteries are delivering about double the amount of electricity that they had been providing when they were first introduced, and their cost has not increased appreciably. This implies that the cost of the electricity from them has been roughly halved. Other battery technologies have alsoseen exciting developments. For example the ViZn flow battery shows a number of improvements over earlier designs at considerably lower costs. Salt water batteries, such as those from Aquion Energy, also come to mind. As fast as the price of electricity from solar PVs has been dropping, we should not be surprised if the costs of solar-plus-storage or wind-plus-storage drop considerably faster.
There are other advantages implicit in adding storage to the power supply. One is that the power can be ramped up or down much faster than it can be with conventional approaches to equipment. Power demands on batteries and some other storage solutions can be ramped up or down in fractions of a second.
Indeed, the storage component moves us into a situation where solar and wind, with support from other types of renewable energy, can take on larger baseload power systems. Clearly, if utility-scale solar + storage = $92/MWh, it will always be less expensive than the $97 to $136 per MWh cost of nuclear power. It is competitive with power from coal. The only fossil fuel remaining in Lazard’s analysis that is clearly less expensive than solar-plus-storage is combined cycle natural gas, with a cost range of $48 to $78 MWh, and we have no guarantees those prices will last. And remember, this is not solar power alone, but solar with energy storage.
We seem to be moving into a new age, and it is not merely an age when the sun and wind provide the least expensive power we have. It is an age when the sun and the wind may replace baseload power altogether, not only as the least expensive solution, but as the best general solution. And we might come to that faster than we dreamed possible.
What Would Happen if the Entire West Antarctic Ice Sheet Collapsed? http://www.ecowatch.com/west-antarctic-ice-sheet-2159166639.html By Tim Radford, Dec 24 2016
Scientists in the U.S. have identified an ominous trend in the Southern Ocean—the creation of enormous icebergs as rifts develop in the shelf ice many miles inland. And although three vast icebergs have broken from the Pine Island glacier in West Antarctica and drifted north in this century alone, researchers have only just worked out what has been going on.
Their first clue came from a telltale shadow in the south polar ice, caught by a NASA satellite and visible only while the sun was low in the sky, casting a long shadow.
It was the first sign of a fracture 20 miles inland, in 2013. Two years later, the rift became complete and the 580 sq km iceberg drifted free of the shelf.
“It’s generally accepted that it’s no longer a question of whether the West Antarctic Ice Sheet will melt—it’s a question of when,” said study leader Ian Howat, a glaciologist in the School of Earth Sciences at Ohio State University in the U.S.
“This kind of rifting behavior provides another mechanism for rapid retreat of these glaciers, adding to the probability that we may see significant collapse of West Antarctica in our lifetimes.”
The scientists report in Geophysical Research Letters journal says that they discovered that although shelf ice could be expected to wear at the ocean edge, something else was happening in West Antarctica.
The Pine Island glacier is grounded on continental bedrock below sea level, which means that warming ocean water could penetrate far inland beneath the shelf, without anyone being conscious of any change.
The first evidence of something unusual was a valley—the one highlighted by shadows visible only at a particular time and captured by NASA imagery—in the ice, where it had thinned. The valley was the first outward sign that ice was melting far below the surface.
The shelf ice plays an important role in slowing the progress of south polar glaciers: remove the shelf ice and the glacier flow accelerates.
Researchers have already identified evidence of glacier retreat in the West Antarctic and warned that bodies of ice massive enough together to raise global sea levels by three meters could—thanks to global warming as a consequence of fossil fuel combustion—be increasingly unstable.
Dr. Howat said:
The really troubling thing is that there are many of these valleys further up-glacier. If they are actually sites of weakness that are prone to rifting, we could potentially see more accelerated ice loss in Antarctica.
Antarctica is home to more than half the world’s fresh water. The Pine Island glacier and its neighbor and twin, the Thwaite glacier, are at the outer edge of an ice stream. In effect, they have “corked” the flow.
But West Antarctica is warming far more swiftly than the rest of the south polar region. And the calving of huge icebergs fuels researchers’ fear that, within 100 years, the entire West Antarctic ice sheet could collapse, with disastrous consequences for many coastal cities worldwide.
Sea ice hit record lows in November, EurekAlert, 6 Dec 16 UNIVERSITY OF COLORADO AT BOULDER Unusually high air temperatures and a warm ocean have led to a record low Arctic sea ice extent for November, according to scientists at the National Snow and Ice Data Center (NSIDC) at the University of Colorado Boulder. In the Southern Hemisphere, Antarctic sea ice extent also hit a record low for the month, caused by moderately warm temperatures and a rapid shift in circumpolar winds.
“It looks like a triple whammy–a warm ocean, a warm atmosphere, and a wind pattern all working against the ice in the Arctic,” said NSIDC director Mark Serreze.
Arctic sea ice extent averaged 9.08 million square kilometers (3.51 million square miles) for November, 1.95 million square kilometers (753,000 square miles) below the 1981 to 2010 long-term average for the month. Although the rate of Arctic ice growth was slightly faster than average, total extent actually decreased for a brief period in the middle of the month. The decrease in extent measured 50,000 square kilometers (19,300 square miles) and was observed mostly in the Barents Sea, an area of the Arctic Ocean north of Norway, Finland, and Eastern Russia.
NSIDC scientists said the decrease in extent is almost unprecedented for November in the satellite record; a less pronounced and brief retreat of 14,000 square kilometers (5,400 square miles) happened in 2013. November 2016 is now the seventh month this year to have hit a record low extent in the 38-year satellite monitoring period. The November extent was 3.2 standard deviations below the long-term average, a larger departure than observed in September 2012 when the Arctic summer minimum extent hit a record low………
In the Southern Hemisphere, sea ice surrounding the continent of Antarctica declined very quickly early in the month and set a record low. The average extent for November was 14.54 million square kilometers (5.61 million square miles), 1.81 million square kilometers (699,000 square miles) below the 1981 to 2010 average. This was more than twice the previous record departure from average set in November 1986 and was 5.7 standard deviations below the long-term average.
NSIDC scientists said that higher-than-average temperatures and a rapid shift in Antarctic circumpolar winds appear to have caused the rapid decline in Antarctic sea ice……..
NASA scientist and NSIDC affiliate scientist Walt Meier said, “The Arctic has typically been where the most interest lies, but this month, the Antarctic has flipped the script and it is southern sea ice that is surprising us.” https://www.eurekalert.org/pub_releases/2016-12/uoca-sih120616.php
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.
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