Antarctic ice will likely melt much faster than originally feared, enough to double the rate of sea level rise

Scientists in the US predict that the alarming rate at which Antarctica’s ice continues to thaw could be enough to double global sea level rise within this century.

The towering ice cliffs of Antarctica could be at increasing risk of crumbling. Image: Michael Van Woert, NOAA NESDIS, ORA

by Tim Radford, Climate News Network, April 2, 2016

LONDON, 2 April, 2016 – Climate scientists may have collectively underestimated the hazards of sea level rise. If greenhouse gas emissions continue to increase at their present rate, then, in Antarctica alone, enough ice will have run into the seaby the end of the century to raise the high tide mark worldwide by a metre.

And if the process continues, then by 2500 enough of Antarctica’s massive ice cap will have melted to raise sea levels by 15 metres.

The new finding focuses only on revised calculations for Antarctica. It does not count the melting from all the world’s mountain glaciers, the permafrost, or the Greenland ice cap, and it is concerned principally with the immediate impact of global warming. But the consequences are ominous enough.

“This could spell disaster for many low-lying cities,” says Robert DeConto, professor of climatology  at  the University of Massachusetts-Amherst. “For example, Boston could see more than 1.5 metres of sea level rise in the next 100 years. But the good news is that an aggressive reduction in emissions will limit the risk of major Antarctic ice retreat.”

Professor DeConto and co-author David Pollard, senior scientist at Penn State University’s Earth and Environmental Systems Institute, publish their new simulations in Nature and begin by thinking about sea level rise long before the emergence of humankind, let alone human civilisation.

Waiting for action

“We looked at the long-standing problem posed by geological evidence that suggests sea level rose dramatically in the past, possibly by up to 10 to 20 metres around 3 million years ago in the Pliocene,” Dr Pollard says. “Existing models couldn’t simulate enough ice sheet melting to explain that.”

The scientists’ warning comes with an important proviso: this is what could happen if humans continue to burn fossil fuels at the present rate, to increase the carbon dioxide composition of the atmosphere, and to drive global warming. In Paris in December 195 nations vowed to take steps to contain climate change.

But promises have yet to become sustained action. And the predictions of climate change on which the Paris judgment was based were essentially compromise: a consensus around a median between the most and least hopeful calculations.

“We regard the results as worst-case envelopes of possible
future behaviour, and the mechanisms should be
considered seriously in future work”

The two US scientists are not the only ones to see heightened dangers of south polar melting or to suggest that warming is happening faster, or thatAntarctica’s glacial ice is running more swiftly into the sea than the consensus predicts.

They started with an exquisitely detailed model that embraced the physical processes that conserve ice or lead to its loss.

These include the fine detail of atmospheric warming and ice dynamics – what rainwater might do to the ice sheet that floats on the Southern Ocean and blocks the glacial flow from the land, for instance, and what makes ice cliffs collapse into the sea – along with a lot of lessons from the past.

Warmer ocean

Right now, what pushes the loss of ice is a warmer ocean, thinning the ice sheet from below. Melting water from the surface will penetrate the ice and cause it to crack.

When the ice shelves are gone, the glaciers can accelerate. But the continent bears a massive burden of ice: the remaining ice cliffs would be so huge they could not support their own weight, and these too would collapse at an increasing rate. Once the process begins, then atmospheric warming will prevent the formation of more ice.

“Although the future sea-level contribution in our model is greater than previously thought, it is based on credible mechanisms and is consistent with geologic evidence of past sea-level rise,” Dr Pollard says. “We regard the results as worst-case envelopes of possible future behaviour, and the mechanisms should be considered seriously in future work.”

http://climatenewsnetwork.net/antarctic-may-melt-far-faster-than-thought/

Joe Romm: Leading Climate Scientists: ‘We Have A Global Emergency,’ Must Slash CO2 ASAP!

by Joe Romm, Climate Progress, March 22, 2016

James Hansen and 18 leading climate experts have published a peer-reviewed version of their 2015 discussion paper on the dangers posed by unrestricted carbon pollution. The study adds to the growing body of evidence that the current global target or defense line embraced by the world — 2 °C (3.6 °F) total global warming — “could be dangerous” to humanity.

That 2 °C warming should be avoided at all costs is not news to people who pay attention to climate science, though it may be news to people who only follow the popular media. The warning is, after all, very similar to the one found in an embarrassingly under-reported report last year from 70 leading climate experts, who had been asked by the world’s leading nations to review the adequacy of the 2 °C target.

Specifically, the new Hansen et al. study — titled “Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 °C global warming could be dangerous” — warns that even stabilizing at 2 °C warming might well lead to devastating glacial melt, multimeter sea level rise and other related catastrophic impacts. The study is significant not just because it is peer-reviewed, but because the collective knowledge about climate science in general and glaciology in particular among the co-authors is quite impressive.

Besides sea level rise, rapid glacial ice melt has many potentially disastrous consequences, including a slowdown and eventual shutdown of the key North Atlantic Ocean circulation and, relatedly, an increase in super-extreme weather. Indeed, that slowdown appears to have begun, and, equally worrisome, it appears to be supercharging both precipitation, storm surge, and superstorms along the U.S. East Coast (like Sandy and Jonas), as explained here.

It must be noted, however, that the title of the peer-reviewed paper is decidedly weaker than the discussion paper’s “Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 °C global warming is highly dangerous.” The switch to “could be dangerous” is reminiscent of the switch (in the opposite direction) from the inaugural 1965 warning required for cigarette packages, “Caution: Cigarette Smoking May Be Hazardous to Your Health” to the 1969 required label “Warning: The Surgeon General Has Determined that Cigarette Smoking Is Dangerous to Your Health.”

And yes I’m using the analogy to suggest readers should not be sanguine about the risks we face at 2 °C warning. Based on both observations and analysis, the science is clearly moving in the direction that 2 °C warming is not “safe” for humanity. But as Hansen himself acknowledged Monday on the press call, the record we now have of accelerating ice loss in both Greenland and West Antarctica is “too short to infer accurately” whether the current exponential trend will continue through the rest of the century.

Hansen himself explains the paper’s key conclusions and the science underlying them in a new video:

The fact that 2 °C total warming is extremely likely to lock us in to sea level rise of 10 feet or more has been obvious for a while now. The National Science Foundation (NSF) itself issued a news release back in 2012 with the large-type headline, “Global Sea Level Likely to Rise as Much as 70 Feet in Future Generations.”  The lead author explained, “The natural state of the Earth with present carbon dioxide levels is one with sea levels about 70 feet higher than now.” Heck, a 2009 paper in Science found the same thing.

What has changed is our understanding of just how fast sea levels could rise. In 2014 and 2015, a number of major studies revealed that large parts of the Antarctic and Greenland ice sheets are unstable and headed toward irreversible collapse — and some parts may have already passed the point of no return. Another 2015 study found that global sea level rise since 1990 has been speeding up even faster than we knew.

The key question is how fast sea levels can rise this century and beyond. In my piece last year on Hansen’s discussion draft, I examined the reasons the Intergovernmental Panel on Climate Change (IPCC) and scientific community have historically low-balled the plausible worst-case for possible sea level rise by 2100. I won’t repeat that all here.

The crux of the Hansen et al. forecast can be found in this chart on ice loss from the world’s biggest ice sheet:

Antarctic ice mass change from GRACE satallite data (red) and surface mass balance method (MBM, blue). From Hansen et al.

Hansen et al. ask the question: if the ice loss continues growing exponentially how much ice loss (and hence how much sea level rise) will there be by century’s end? If, for instance, the ice loss rate doubles every 10 years for the rest of the century (light green), then we would see multi-meter sea level rise before 2100? On the other hand, it is pretty clear just from looking at the chart that there isn’t enough data to make a certain projection for the next eight decades.

The authors write, “our conclusions suggest that a target of limiting global warming to 2 °C … does not provide safety.” On the one hand, they note, “we cannot be certain that multi-meter sea level rise will occur if we allow global warming of 2 °C.” But, on the other hand, they point out:

There is a possibility, a real danger, that we will hand young people and future generations a climate system that is practically out of their control.
We conclude that the message our climate science delivers to society, policymakers, and the public alike is this: we have a global emergency. Fossil fuel CO2 emissions should be reduced as rapidly as practical.

I have talked to many climate scientists who quibble with specific elements of this paper, in particular whether the kind of continued acceleration of ice sheet loss is physically plausible. But I don’t find any who disagree with the bold-faced conclusions.

Since there are a growing number of experts who consider that 10 feet of sea level rise this century is a possibility, it would be unwise to ignore the warning. That said, on our current emissions path we already appear to be headed toward the ballpark of 4-6 feet of sea level rise in 2100 — with seas rising up to one foot per decade after that. That should be more than enough of a “beyond adaptation” catastrophe to warrant strong action ASAP.

The world needs to understand the plausible worst-case scenario for climate change by 2100 and beyond — something that the media and the IPCC have failed to deliver. And the world needs to understand the “business as usual” set of multiple catastrophic dangers of 4 °C if we don’t reverse course now. And the world needs to understand the dangers of even 2 °C warming.

So kudos to all of these scientists for ringing the alarm bell: James Hansen, Makiko Sato, Paul Hearty, Reto Ruedy, Maxwell Kelley, Valerie Masson-Delmotte, Gary Russell, George Tselioudis, Junji Cao, Eric Rignot, Isabella Velicogna, Blair Tormey, Bailey Donovan, Evgeniya Kandiano, Karina von Schuckmann, Pushker Kharecha, Allegra N. Legrande, Michael Bauer, and Kwok-Wai Lo.

http://thinkprogress.org/climate/2016/03/22/3762111/climate-scientists-global-emergency/

James Hansen: ‘Emergency Cooperation Among Nations’ Is Needed to Prevent Catastrophic Sea Level Rise

“Roughly 10 feet of sea level rise—well beyond previous estimates—would render coastal cities such as New York, London, and Shanghai uninhabitable.” Photo credit: Woodbine

by Jon Queally, Common Dreams, July 21, 2015

If a new scientific paper is proven accurate, the international target of limiting global temperatures to a 2 °C rise this century will not be nearly enough to prevent catastrophic melting of ice sheets that would raise sea levels much higher and much faster than previously thought possible.

According to the new study—which has not yet been peer-reviewed, but was written by former NASA scientist James Hansen and 16 other prominent climate researchers—current predictions about the catastrophic impacts of global warming, the melting of vast ice sheets and sea level rise do not take into account the feedback loop implications of what will occur if large sections of Greenland and the Antarctic are consumed by the world’s oceans.

A summarized draft of the full report was released to journalists on Monday, with the shocking warning that such glacial melting will “likely” occur this century and could cause as much as a 10 foot sea-level rise in as little as 50 years. Such a prediction is much more severe than current estimates contained in reports issued by the Intergovernmental Panel on Climate Change (IPCC) — the UN-sponsored body that represents the official global consensus of the scientific community.

“If the ocean continues to accumulate heat and increase melting of marine-terminating ice shelves of Antarctica and Greenland, a point will be reached at which it is impossible to avoid large scale ice sheet disintegration with sea level rise of at least several meters,” the paper states.

Separately, the researchers conclude that “continued high emissions will make multi-meter sea level rise practically unavoidable and likely to occur this century. Social disruption and economic consequences of such large sea level rise could be devastating. It is not difficult to imagine that conflicts arising from forced migrations and economic collapse might make the planet ungovernable, threatening the fabric of civilization.”

The Daily Beast‘s Mark Hertsgaard, who attended a press call with Dr. Hansen on Monday, reports that the work presented by the researchers is

"...warning that humanity could confront “sea level rise of several meters” before the end of the century unless greenhouse gas emissions are slashed much faster than currently contemplated.

This roughly 10 feet of sea level rise—well beyond previous estimates—would render coastal cities such as New York, London, and Shanghai uninhabitable. “Parts of [our coastal cities] would still be sticking above the water,” Hansen said, “but you couldn’t live there.”

This apocalyptic scenario illustrates why the goal of limiting temperature rise to 2 degrees Celsius is not the safe “guardrail” most politicians and media coverage imply it is, argue Hansen and 16 colleagues in a blockbuster study they are publishing this week in the peer-reviewed journal Atmospheric Physics and Chemistry. On the contrary, a 2C future would be “highly dangerous.”

If Hansen is right—and he has been right, sooner, about the big issues in climate science longer than anyone—the implications are vast and profound.

In the call with reporters, Hansen explained that time is of the essence, given the upcoming climate talks in Paris this year and the grave consequences the world faces if bold, collective action is not taken immediately. “We have a global crisis that calls for international cooperation to reduce emissions as rapidly as practical,” the paper states.

Hansen said he has long believed that many of the existing models were under-estimating the potential impacts of ice sheet melting, and told the Daily Beast: “Now we have evidence to make that statement based on much more than suspicion.”

Though he acknowledged the publication of the paper was unorthodox, Hansen told reporters that the research itself is “substantially more persuasive than anything previously published.”

For his part, Eric Holthaus, a meteorologist who writes about weather and climate for Slate, said the “bombshell” findings are both credible and terrifying. Holthaus writes:

To come to their findings, the authors used a mixture of paleoclimate records, computer models, and observations of current rates of sea level rise, but “the real world is moving somewhat faster than the model,” Hansen says.

[…] The implications are mindboggling: In the study’s likely scenario, New York City—and every other coastal city on the planet—may only have a few more decades of habitability left. That dire prediction, in Hansen’s view, requires “emergency cooperation among nations.”

In response to the paper, climate scientist Michael Oppenheimer of Princeton University affirmed: “If we cook the planet long enough at about two degrees warming, there is likely to be a staggering amount of sea level rise. Key questions are when would greenhouse-gas emissions lock in this sea level rise and how fast would it happen? The latter point is critical to understanding whether and how we would be able to deal with such a threat.”

The new research, Oppenheimer added, “takes a stab at answering the ‘how soon?’ question but we remain largely in the dark. Giving the state of uncertainty and the high risk, humanity better get its collective foot off the accelerator.”

And as the Daily Beast‘s Hertsgaard notes, Hansen’s track record on making climate predictions should command respect from people around the world. The larger question, however, is whether humanity has the capacity to act.

“The climate challenge has long amounted to a race between the imperatives of science and the contingencies of politics,” Hertsgaard concludes. “With Hansen’s paper, the science has gotten harsher, even as the Nature Climate Change study affirms that humanity can still choose life, if it will. The question now is how the politics will respond—now, at Paris in December, and beyond.”

http://ecowatch.com/2015/07/21/james-hansen-climate-report/

NSIDC: Arctic sea ice conditions, April 7, 2015

from the National Snow and Ice Data Center, April 7, 2015

After reaching its seasonal maximum on February 25, 2015, the beginning of the melt season was interrupted by late-season periods of ice growth, largely in the Bering Sea, Davis Strait and around Labrador. Near the end of March, extent rose to within about 83,000 square kilometers (32,000 square miles) of the February 25 value. The monthly average Arctic sea ice extent for March was the lowest in the satellite record.

Overview of conditions

Figure 1. Arctic sea ice extent for March 2015 was 14.39 million square kilometers (5.56 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data. Credit: National Snow and Ice Data Center. High-resolution image

Arctic sea ice extent for March 2015 averaged 14.39 million square kilometers (5.56 million square miles). This is the lowest March ice extent in the satellite record. It is 1.13 million square kilometers (436,000 square miles) below the 1981 to 2010 long-term average of 15.52 million square kilometers (6.00 million square miles). It is also 60,000 square kilometers (23,000 square miles) above the previous record low for the month observed in 2006.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of April 5, 2015, along with daily ice extent data for four previous years. 2015 is shown in blue, 2014 in green, 2013 in orange, 2012 in brown, and 2011 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data. Credit: National Snow and Ice Data Center. High-resolution image

The change in total Arctic sea ice extent for March is typically quite small. It tends to increase slightly during the first part of the month, reach the seasonal maximum, and then decline over the remainder of the month. Following the seasonal maximum recorded on February 25, this year instead saw a small decline over the first part of March, and then an increase, due largely to periods of late ice growth in the Bering Sea, Davis Strait and around Labrador. On March 26, extent had climbed to within 83,000 square kilometers (32,000 square miles) of the seasonal maximum recorded on February 25. Despite this late-season ice growth, analysts at the Alaska Ice Program report in their April 3 post that ice in the Bering Sea was very broken up.

March 2015 compared to previous years

Figure 3. Monthly March ice extent for 1979 to 2015 shows a decline of 2.6% per decade relative to the 1981 to 2010 average. Credit: National Snow and Ice Data Center. High-resolution image

The monthly average Arctic sea ice extent for March was the lowest in the satellite record. Through 2015, the linear rate of decline for March extent is 2.6% per decade.

Overview of the winter season

Figure 4. The plot shows Arctic air temperature anomalies at the 925-hPa level in degrees Celsius for March 2015. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures. 
Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
High-resolution image

As discussed in our previous post, the winter of 2014/2015 was characterized by an unusual pattern of atmospheric circulation, with the jet stream lying well north of its usual location over Eurasia and the North Pacific, and then plunging southwards over eastern North America. This pattern was associated with unusually warm conditions extending across northern Eurasia, the Bering Sea and Sea of Okhotsk, Alaska and into the western part of the United States, contrasting with cold and snowy conditions over the eastern half of the United States. The record low seasonal maximum in ice extent recorded on February 25, 2015, was largely due to low extent in the unusually warm Bering Sea and Sea of Okhotsk. This pattern of atmospheric circulation and temperatures largely continued through March.

Recent work by Dennis Hartmann of the University of Washington suggests that this unusual jet stream pattern was driven, at least in part, by a particular configuration of sea surface temperatures over the tropical Pacific known as the North Pacific Mode, or NPM. The NPM pattern consists of above-average sea surface temperatures in the western Tropical Pacific that extend north along the California coast and across the far northern Pacific Ocean. While the better-known El Nino-Southern Oscillation (ENSO) pattern has been in a neutral state for the past few winters, the NPM has been in an extreme positive state since the summer of 2013.

The pattern of air temperatures seen this past winter has persisted through March; note the unusually warm conditions over northern Eurasia, Alaska and western North America, contrasting with unusually cold conditions over eastern North America.

Snow cover update

Figure 5. This map shows the rank of snow water equivalent measured at SNOTEL sites across the western U.S. A rank of 1 (black dots) corresponds to the lowest SWE in the SNOTEL record; a rank of 31 (magenta dots) is the highest. Credit: Andrew Slater, NSIDC. High-resolution image

The unusual atmospheric circulation pattern just discussed also helps to explain the snow drought over the western United States. NSIDC scientist Andrew Slater maintains regular updates of western U.S. mountain snowpack conditions using data from the SNOTEL (snowpack telemetry) system – a network of automated sensors that measure snow water equivalent. The automated SNOTEL sites are complemented by snowcourses, where snow water equivalent is measured manually on a periodic basis.

Typically, the snowpack peaks around April 1. As seen in Figure 5, the April 1 snowpack over most of the western United States is far below average. At many sites, snow water equivalent is at historic lows for this time of year. Conditions are somewhat better along the Front Range of Colorado and in Arizona, Wyoming and Montana.

Record warmth in Antarctica

Air temperatures reached record high levels at two Antarctic stations last week, setting a new mark for the warmest conditions ever measured anywhere on the continent. On March 23, at Argentina’s base Marambio, a temperature of 17.4 °C (63.3 °F) was reached, surpassing a previous record set in 1961 at a nearby base, Esperanza. The old record was 17.1 °C (62.8 °F). However, Esperanza quickly reclaimed the record a few hours later on March 24, reaching a temperature of 17.5 °C (63.5 °F).

The cause of these warm conditions is familiar to people living in mountainous regions: a foehn or chinook wind, in which air flows up and over a steep mountain ridge. On the windward side, moisture is wrung out of the air mass in the form of rain or snow. As the air descends on the leeward (downwind) side, it compresses and warms.

This airflow pattern is a key part of the climate conditions that led to past ice shelf disintegrations in the region, such as the dramatic break-up of the Larsen B Ice Shelf in 2002. Air pressure patterns during the event indicated a near-stationary high pressure center in the Drake Passage north of the Antarctic Peninsula, and a strong area of low pressure at the base of the Peninsula, favoring the foehn pattern. Events like this have been recorded by a network of sensors installed by the National Science Foundation LARISSA project.  This network recorded temperatures as high as 16.9 °C (62.4 °F), westerly winds up to 23 meters per second (45 miles per hour), and a ~100-hour period of temperatures above freezing over the Larsen B area. A recent publication by a colleague at the Scripps Institute of Oceanography describes the impact of foehn or chinook patterns on ice shelf and sea ice stability in the region, making use of the network of Automated Meteorology-Ice-Geophysics Observing Systems (AMIGOS) in the area.

Further reading

Cape, M., M. Vernet, P. Skvarca, S. Marinsek, T. Scambos, and E. Domack. 2015. Foehn winds link climate-driven warming to coastal cryosphere evolution in Antarctica. Jour. Geophys. Res., Atmospheres, accepted.

Scambos, T., R. Ross, T. Haran, R. Bauer, D.G. Ainley, K.-W. Seo, M. Keyser, A. De, Behar, D.R. MacAyeal. 2013. A camera and multisensor automated station design for polar physical and biological systems monitoring: AMIGOS. Journal of Glaciology, 59 (214), 303-314, doi: 10.3189/2013JoG12J170.

http://nsidc.org/arcticseaicenews/

63.5°F in Antarctica: Possible Continental Record

by Jeff Masters and Bob Henson, wunderblog, March 27, 2015

The warmest temperature ever recorded on the continent of Antarctica may have occurred on Tuesday, March 24, 2015, when the mercury shot up to 63.5 °F (17.5 °C) at Argentina's Esperanza Base on the northern tip of the Antarctic Peninsula. According to weather records researcher Maximiliano Herrera, the previous hottest temperature recorded in Antarctica was 63.3 °F (17.4 °C) set just one day previously at Argentina's Marambio Base, on a small islet just off the coast of the Antarctic Peninsula. Prior to this week's remarkable heat wave, the hottest known temperature in Antarctica was the 62.8 °F (17.1 °C) recorded at Esperanza Base on April 24, 1961. (The World Meteorological Organization—WMO—has not yet certified that this week's temperatures are all-time weather records for Antarctica, though the Argentinian weather service has verified that the temperatures measured at Esperanza Base and Marambio Base were the highest ever measured at each site.) A new all-time temperature record for an entire continent is a rare event, and Weather Underground's weather historian, Christopher C. Burt, has full details in his latest post. 


Figure 1. Argentina's Esperanza Base on the northern tip of the Antarctic Peninsula: the hottest place in Antarctica. Image credit: Wikipedia.

The Antarctic Peninsula is one of the fastest warming spots on Earth. A 2012 Climate Central post by Michael Lemonick documented how while the Earth as a whole warmed up by 1.3 °F between 1900 and 2011, the Antarctic Peninsula warmed by 5 °F, forcing massive ice shelves to disintegrate and penguin colonies to collapse. A 2012 paper in Nature found that the recent warming is faster than 99.7% of any other given 100-year period in the last 2,000 years.

New all-time national and territorial heat records set or tied in 2015

So far in 2015, five nations or territories have tied or set all-time records for their hottest temperature in recorded history. For comparison, only two nations or territories did so in 2014, and nine did in 2013. The most all-time national heat records in a year was nineteen in 2010 (21 records at the time, but two have been broken since). Since 2010, 46 nations or territories (out of a total of 235) have set or tied all-time heat records, and four have set all-time cold temperature records. Since each of those years ranked as one of the top twelve warmest years in Earth's recorded history, this sort of disparity in national heat and cold records is to be expected. Most nations do not maintain official databases of extreme temperature records, so the national temperature records reported here are in many cases not official. I use as my source for international weather records Maximiliano Herrera, one of the world's top climatologists, who maintains a comprehensive list of extreme temperature records for every nation in the world on his website. If you reproduce this list of extremes, please cite Maximiliano Herrera as the primary source of the weather records. Wunderground's weather historian Christopher C. Burt maintains a database of these national heat and cold records for 235 nations and territories on wunderground.com's extremes page. Here are the national heat and cold records set so far in 2015:

Antarctica set a new territorial heat record of 17.5 °C (63.5 °F) at Esperanza Base on March 24. Previous record: 17.4 °C (63.3 °F) at Marambio Base, set the previous day.

Equatorial Guinea set a new national heat record of 35.5 °C (95.9 °F) at Bata on March 17. Previous record:  35.3 °C (95.5 °F) at Malabo in February 1957.


Ghana tied the national record of highest temperature with 43.0 °C (109.4 °F)  at Navrongo on February 12.


Wallis and Futuna Territory (France) set a new territorial heat record with 35.5 °C (95.9 °F) on January 19 at Futuna Airport.

Samoa tied its national heat record with 36.5 °C (97.7 °F) on January 20 at Asau. Previously record: same location, in December 1977.

http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=2944

Robert Schribbler: Warm Water Rising From the Depths: Much of Antarctica Now Under Threat of Melt

by Robert Schribbler, Robert Schribbler's blog, December 5, 2014

Antarctica. A seemingly impregnable fortress of cold. Ice mountains rising 2,100 meters high. Circumpolar winds raging out from this mass of chill frost walling the warm air out. And a curtain of sea ice insulating the surface air and mainland ice sheets from an increasingly warm world. A world that is now on track to experience one of its hottest years on record.

Antarctica, the coldest place on Earth, may well seem impregnable to this warming. But like any other fortress, it has its vulnerable spots. In this case, a weak underbelly. For in study after study, we keep finding evidence that warm waters are rising up from the abyss surrounding the chill and frozen continent. And the impact and risk to Antarctica’s glacial ice mountains is significant and growing.

(Collapse of ice structure at the leading edge of the Filchner-Ronne Ice Shelf adjacent to a rapidly warming Weddell Sea during January of 2010. A new study has found warm water upwelling from the Circumpolar Deep Water is rapidly approaching this massive ice shelf. Loss of Filchner-Ronne and its inland buttressed glaciers would result in 10 feet of sea level rise. Image source: Commons.)

For a study this week confirmed that Antarctica is now seeing a yearly loss of ice equal to one half the volume of Mt Everest every single year. A rate of loss triple that seen just ten years ago. An acceleration that, should it continue, means a much more immediate threat to coastal regions from sea level rise than current IPCC projections now estimate.

Shoaling of the Circumpolar Deep Water

The source of this warm water comes from a deep-running current that encircles all of Antarctica. Called the Circumpolar Deep Water, this current runs along the outside margin of the continental shelf. Lately, the current has been both warming and rising up the boundaries of the continental zone. And this combined action is rapidly bringing Antarctica’s great ice sheets under increasing threat of more rapid melt.

According to a new study led by Sunke Schmidtko, this deep water current has been warming at a rate of 0.1 degrees Celsius per decade since 1975. Even before this period of more rapid deep water warming, the current was already warmer than the continental shelf waters near Antarctica’s great glaciers. With the added warming, the Circumpolar Deep Water boasts temperatures in the range of 33 to 35 degrees Fahrenheit — enough heat to melt any glacier it contacts quite rapidly.

Out in the deep ocean waters beyond the continental shelf zone surrounding Antarctica, the now warmer waters of this current can do little to effect the great ice sheets. Here Sunke’s study identifies the crux of the problem — the waters of the Circumpolar Deep Water are surging up over the continental shelf margins to contact Antarctica’s sea fronting glaciers and ice shelves with increasing frequency.

In some cases, these warm waters have risen by more than 300 feet up the continental shelf margins and come into direct contact with Antarctic ice — causing it to rapidly melt. This process is most visible in the Amundsen Sea where an entire flank of West Antarctica is now found to be undergoing irreversible collapse. The great Pine Island Glacier, the Thwaites Glacier and many of its tributaries altogether composing enough ice to raise sea levels by 4 feet are now at the start of their last days. All due to an encroachment of warm water rising up from the abyss.

(Antarctic rivers of ice. Rising and warming waters from the Circumpolar Deep Water along continental margins have been increasingly coming into contact with ice shelf and glacier fronts that float upon or face the surrounding seas. The result has been much higher volumes of melt water contributions than expected from Antarctica. Image source: University of California.)

But the warm water rise is not just isolated to the Amundsen Sea. For Sunke also found that the warm water margin in the Weddell Sea on the opposite flank of West Antarctica was also rapidly on the rise. From 1980 to 2010, this warm water zone had risen from a depth of about 2100 feet to less than 1100 feet. A rapid advance toward another massive concentration of West Antarctic ice.

The impacts of a continued rise of this kind can best be described as chilling.

Sunke notes in an interview with National Geographic:

If this shoaling rate continues, there is a very high likelihood that the warm water will reach the Filchner Ronne Ice Shelf, with consequences which are huge.

Filchner Ronne, like the great Pine Island Glacier, has been calving larger and larger ice bergs during recent years. Should warm waters also destabilize this vast ice shelf another 1.5 feet of sea level rise would be locked in due to its direct loss. Including the massive inland glaciers that Filchner Ronne buttresses against a seaward surge, much larger than the ones near the Amundsen sea, would add a total of 10 feet worth of additional sea level rise.

Together, these destabilized zones would unleash much of West Antartica and some of Central Antartica, resulting in as much as 14 feet of sea level rise over a 100 to 200 year timeframe. This does not include Greenland, which is also undergoing rapid destabilization, nor does it include East Antarctica — which may also soon come under threat due to the encroachment of warm waters rising from the depths.

Are IPCC Projected Rates of Sea Level Rise Too Conservative?

The destabilization of glaciers along the Amundsen sea, the imminent threat to the Filchner Ronne Ice Shelf, and the less immediate but still troubling threat to East Antarctica’s glaciers, together with a rapidly destabilizing Greenland Ice Sheet, calls into question whether current IPCC predictions for sea level rise before 2100 are still valid.

IPCC projects a rise in seas of 1-3 feet by the end of this Century. But much of that rise is projected to come from thermal expansion of the world’s oceans — not from ice sheet melt in Antarctica and Greenland. Current rates of sea level rise of 3.3 milimeters each year would be enough to hit 1 foot of sea level rise by the end of this Century. However, just adding in the melting of the Filchner Ronne — a single large ice shelf — over the same period would add 4.4 milimeters a year. Add in a two century loss of the Amundsen glaciers — Pine Island and Thwaites — and we easily exceed the three foot mark by 2100.

Notably, this does not include the also increasingly rapid loss of ice coming from Greenland, the potential for mid century additions from East Antarctica, or lesser but still important additions from the world’s other melting glaciers.

Such more rapid losses to ice sheets may well reflect the realities of previous climates. At current CO2e levels of 481 ppm (400 ppm CO2 + methane and other human greenhouse gas additions) global sea levels were as much as 75-120 feet higher than they are today. Predicted greenhouse gas levels of 550 to 600 ppm CO2e by the middle of this century (Breaking 550 ppm CO2 alone by 2050 to 2060) are enough to set in place conditions that would eventually melt all the ice on Earth and raise sea levels by more than 200 feet. For there was no time in the past 55 million years when large ice sheets existed under atmospheric CO2 concentrations exceeding 550 parts per million.

Glaciologist Eric Rignot has been warning for years that the IPCC sea level rise estimates may well be too conservative. And it seems that recent trends may well bear his warnings out. If so, the consequences to millions of people living along the world’s coastlines are stark and significant. For the world, it appears we face the increasing likelihood of a near-term inland mass-migration of people and property. A stunning set of losses and tragedy starting now and ongoing through many decades and centuries to come.

Links:

Warming Seas Drive Rapid Acceleration of Melting Antarctic Ice

Mass Loss of the Amundsen Sea Embayment of West Antarctica

Multidecadal Warming of Antarctic Waters

Research Casts Alarming Light on Decline of West Antarctic Glaciers

Antarctic Ice Shelf Being Eaten Away by Sea

http://robertscribbler.wordpress.com/2014/12/05/warm-water-rising-from-the-depths-much-of-antarctica-now-under-threat-of-melt/