Peter Sinclair at the AGU, interviews scientists about extreme weather events

by Peter Sinclair, This Is Not Cool, January 7, 2014

This is the first video to include interviews conducted at the American Geophysical Union  Fall Meeting in San Francisco in December 2013.

I started out with a focus on what we were hearing about extreme events, then took a little jog when the latest extreme even presented itself – our current polar vortex, which is a pretty good textbook example of the kind of weather that we may be seeing more of, paradoxically, in this case, cold snap made more likely by increasingly lazy jet stream flow.

The video above contrasts arctic cold and snow in the east with mild temps and droughts in California.

Complete report on  drought from California TV station KSBW below.

Additional report now up on dry lakes in the California area.

The Hill:

Global warming may be contributing to the “polar vortex” causing frigid temperatures across most of the nation on Monday, according to some climate change researchers. 

While it seems counter-intuitive, the research argues that plunging temperatures could come from changes in the jet stream caused by climate change. 

Rutgers University climate scientist Jennifer A Francis has released a number of papers about changes in the jet stream brought about by warming Arctic temperatures. 

Her conclusions suggest that warming Arctic air caused by greenhouse gas emissions has caused changing to the jet stream that is pushing colder Arctic air further south, causing temperatures to plunge from the High Plains to the Deep South. 

The jet stream shift has sent frigid air across the central part of the country, and deeper into the south than normal. 

Alaska, meanwhile, is being hit by unusually warm conditions and California is facing record-breaking drought, Francis said. 

She said the strange weather is becoming more likely because of climate change. 

“We can’t say that these are extremes are because of climate change but we can say that this kind of pattern is becoming more likely because of climate change,” Francis said. 

NASA analysis has also drawn a link between the jet stream, climate change and colder temperatures. 

A 2010 NASA analysis tied colder temperatures over the course of 2009 to an event similar to the wavy jet stream, called “Arctic oscillation” — a see-sawing pressure system over the North Pole. That oscillation pushed cold air to the south. 

The NASA analysis also said that despite cold snaps, and other weather changes being a part of naturally occurring patterns, they are still in line with a “globally warming world.”

 Washington Post:

Almost half of the Lower 48 will shiver under sub-zero wind chills Tuesday morning. Countless records will be set. Yet none of that means a thing about the existence of climate change, its severity or its consequences. 

The breaking off of a large chunk of the polar vortex and its visit to the northern U.S. is a random event resulting from a serendipitous arrangement of weather systems. In short, the clockwise flow around giant areas of high pressure over Alaska and west of Greenland have forced the atmosphere’s steering currents to shove the vortex into the northern U.S. 

 

It happened before humans dumped billions of tons of carbon dioxide into the atmosphere and will happen again. 

This polar vortex excursion is a single weather event directly affecting about 2% of the world. 

Climate change is measured by evaluating continental to global trends in weather over decades – not events happening over a few days in a little region.  For this reason, a fleeting cold wave (or snowstorm) over part of a continent should never be used as evidence for or against climate change. 

The record shows winter temperatures have risen markedly in recent decades across the northern hemisphere. 

 

In short, climate change has reduced the intensity/frequency of cold extremes averaged over time. But that doesn’t mean they’re over or have been eliminated. Events like the record cold in Europe in 2011 and this polar vortex event are clear examples of the exceptional cold weather extreme in a warming world. 

(Were  it not for the build-up of man-made greenhouse gases in the atmosphere, I’d posit the extreme cold events we witness now would be even colder. In other words, take these same cold air outbreaks and project them on the climate of the 1800s, and they’d be more severe. We’d need a model to test that, but it’s an educated guess.) 

The truth is that increasing greenhouse gases act to warm the globe and, on average over time, should take an edge off the cold.  But the planet is a really big, complicated place and the weather changes fast and randomly.  Conversely, the climate changes very gradually. Taking all of this together, cold shouldn’t come as a shock, nor should it have anyone second-guessing the reality of climate warming.

http://climatecrocks.com/2014/01/07/new-video-climate-jetstream-polar-vortex/ 

Arctic Ice Hits Annual Max and Its 6th Lowest on Record

by Andrew Freedman and Michael D. Lemonick, Climate Central, March 26, 2013

The skin of sea ice that covers the Arctic Ocean has reached its maximum extent for 2013, the National Snow and Ice Data Center announced Monday, and the annual melt season has begun. As of March 15, ice covered 5.84 million square miles of ocean, the sixth-lowest since satellite observations began in the 1970s, and 283,000 square miles lower than the 1979-2000 average. Reflecting the influence of global warming, the 10 lowest sea ice maximums have all occurred over the past 10 years.

Animation of the ice fracture using satellite AVHRR data. Credit: Arctic Sea Ice blog via NSIDC.

Last summer’s ice minimum, moreover, was the lowest on record, with 2007 coming in a distant second. Taken together, it’s one more sign that the planet is warming under the influence of heat-trapping greenhouse gases.

The Arctic is warming especially quickly, however, thanks to a sort of vicious cycle that operates between ice, ocean and sunlight. When the sea is covered with bright, reflective ice, incoming sunlight bounces back into space. When the darker water underneath is exposed, some of the Sun’s energy is absorbed, heating the seawater. That warms the air in turn, increasing the melting and exposing even more dark seawater to the incoming sunlight, and so on.

This feedback cycle, known as Arctic amplification, triggered by warming temperatures, has been reducing ice cover more or less steadily for the past 40 years, at least. This sea ice decline may be impacting areas well outside the Arctic Circle, by setting in motion a chain of events that lead to altered weather patterns in the Northern Hemisphere, favoring some types of extreme weather events. 

The ice returns every winter — and in fact, this winter’s ice growth has been greater than ice experts have seen. But that’s only because last summer’s meltback was so drastic, leaving more open water to freeze. And unlike the thick, multi-year ice that once covered much of the Arctic, this new, seasonal ice cover is very thin, making it prone to rapid melting as the Sun emerges after the months-long winter night.

The thin sea ice is also more prone to cracking when under strain from strong winds or currents. In late February and early March, large fractures were observed in the sea ice cover off the north coast of Canada and Alaska, an event that experts called unusual given the area that was affected.

“That entire region is largely covered by seasonal ice, not multiyear ice, and that’s a real different ice pack than what we used to have,” said Walt Meier, a research scientist at the National Snow and Ice Data Center in Boulder, Colo.

Meier said that thin sea ice is now covering the North Pole itself, which is typically capped by thick ice that survives multiple melt seasons. This is only the second time in the 35-year satellite record that this has happened. The first time was in 2008, following the previous record-low ice extent.

“The amount of hard, thick ice has just collapsed. There are now just remnants of it,” said retired Rear Adm. David Titley, an expert in Arctic climate policy, during a conference call with reporters. “So far, we see no evidence that it’s coming back.”

In recent years, sea ice volume, which includes a measure of ice thickness, has been declining at an even faster rate than sea ice extent.

Average surface temperature anomalies during March 2013. It illustrates the influence of the very strong high pressure area over Greenland, with above average air temperatures there (orange and red) and colder than average conditions in the U.S. and Eurasia. Click on the image to enlarge. 
Credit: Weatherbell.com.

Titley said the Arctic does not exist in a “vacuum,” and that changes in the Far North will affect countries far to the south. For example, some studies have shown that a warming Arctic has already had a ripple effect on the world’s weather, contributing to outbreaks of cold and stormy weather in parts of Eurasia and the Eastern U.S. in recent winters.

The snowstorms that have affected the U.S. and Europe this March may be an example of a growing Arctic influence in midlatitude weather. March has been an unusually cold and snowy month across a wide swath of the U.S. and Europe, thanks in part to a slow-moving, sprawling area of High pressure above Greenland. While surface air temperatures have been running well above average in Greenland and northeastern Canada, cold Arctic air has surged into the mid-latitudes, effectively delaying spring’s arrival by several weeks in the Midwest and East Coast. 

This type of weather pattern, with a sharp and persistent deviation in the west-to-east flow of air that steers weather systems across the Northern Hemisphere, may be an indication that Arctic warming is already altering the weather in the mid-latitudes, said Steven Vavrus, a senior scientist at the University of Wisconsin-Madison.

Along with Jennifer Francis, a professor at Rutgers University, Vavrus is one of the principal proponents of the hypothesis that rapid Arctic warming is paradoxically causing colder and snowier winters in the mid-latitudes, along with increased bouts of other extreme weather events. Other researchers have expressed different views about how Arctic climate change is affecting the global climate system.

Vavrus said it’s not yet clear if the recent unusual weather pattern can be attributed to the loss of summer sea ice. “One thing that I think is useful is we can use examples like this winter . . . to look at how the climate system behaves,” he said.

Ultimately, scientists believe, the Arctic Ocean could be largely ice-free for much of the summer, a phenomenon that could happen as early as a decade or two from now. That could be good news for shipping companies, which are already looking to save money by taking an Arctic shortcut from Asia to Europe and back; NOAA, meanwhile, is revising its charts of Alaskan waters to help ships and boats navigate newly ice-free waters.

While that may be good for commerce, the heat-absorbing open water in an ice-free Arctic is likely to keep warming the region, leading to changes on land as well. The most worrisome: if the permanently frozen soil, or permafrost, in northern Alaska, Siberia and Canada thaws substantially, it could release massive amounts of carbon that has been deep-frozen for tens of thousands of years, adding an extra burst of heat-trapping greenhouse gases to the atmosphere and turbo-charging the rate of global warming.

As for what the 2013 winter ice maximum means for this summer’s ice minimum, it’s hard to make a prediction. Sea ice extent declined to the 9th lowest on record in 2012, and the all-time summer low followed six months later. This year’s maximum is lower — but the vagaries of prevailing winds and ocean currents don’t mean we’ll necessarily end the summer with less ice than we did last year. It’s always possible that summer melting will be more moderate than it was in 2012 — after all, it took 5 years after the previous record, set in 2007, for the ice to hit a new low.

But it’s equally possible that Arctic sea ice will shatter last summer’s record. And if it doesn’t happen this year, it will come soon enough.

http://www.climatecentral.org/news/arctic-ice-hits-annual-max-may-be-tied-to-cold-snowy-march-15782

SciAm: What Will Ice-Free Arctic Summers Bring?

by David Biello, Scientific American, September 24, 2012

On Sunday, September 16, 2012, the sun did not rise above the horizon in the Arctic. Nevertheless enough of the sun's heat had poured over the North Pole during the summer months to cause the largest loss of Arctic sea ice cover since satellite records began in the 1970s. The record low 3.41 million square kilometers of ice shattered the previous low—4.17 million square kilometers—set in 2007. All told, since 1979, the Arctic sea ice minimum extent has shrunk by more than 50 percent—and even greater amounts of ice have been lost in the corresponding thinning of the ice, according to the U.S. National Snow and Ice Data Center (NSIDC).

"There is much more open ocean than there used to be," says NSIDC research scientist Walt Meier. "The volume is decreasing even faster than the extent [of surface area] as best as we can tell," based on new satellite measurements and thickness estimates provided by submarines. Once sea ice becomes thin enough, most or all of it may melt in a single summer.

Some ice scientists have begun to think that the Arctic might be ice-free in summer as soon as the end of this decade—leaving darker, heat-absorbing ocean waters to replace the bright white heat-reflecting sea ice. The question is: Then what happens? Although the nature and extent of these rapid changes are not yet fully understood by researchers, the impacts could range ["could range" ?  This is already occurring.] from regional weather-pattern changes to global climate feedbacks that exacerbate overall warming. As Meier says: "We expect there will be some effect…but we can't say exactly what the impacts have been or will be in future." [No, we can't say "exactly" but we have a damned good idea and none of the impacts is good!]

On thin ice
Arctic ice influences atmospheric circulation and, hence, weather and climate. Take away the ice and impacts seem sure to follow. There's more warming to come, as well, particularly in the Arctic, which is warming faster than the rest of the globe. Given cumulative greenhouse gas emissions, there's likely at least as much warming to come as has occurred to date—a rise of 0.8 degree Celsius in global average temperatures, most of that in the past 30 years.

The biggest impacts of the loss of Arctic sea ice, of course, will be felt locally: from the potential for more snowfall (which can act like an insulating blanket keeping the ice warm and incapable of growing) to more storms with stronger winds. These will also whip up waves to pound the shore, eroding it [already happening], as well as bringing warmer temperatures to thaw the permafrost—leading to "drunken" trees and buildings as well as villages slipping into the sea [already happening]. A loss of sea ice will also affect the largest animals in the Arctic: seals, walruses and polar bears [already happening]. "My people rely on that ocean and we've seen some dramatic changes," said Inupiat leader Caroline Cannon at a Greenpeace event on the Arctic in New York City on September 19. "We are the gatekeepers of the ocean. We speak for the animals. They provide for us so it's our time to speak for them," by arguing to ameliorate climate change.

Noting the climate change in Cannon's backyard, the rest of the globe is indeed taking action—just not the type that could reduce greenhouse gas emissions. "The world is looking at the Arctic as a new ocean to be developed and exploited," notes Arctic system scientist David Barber of the University of Manitoba, most particularly oil as evidenced by Shell's bid to drill the first offshore well in the Chukchi Sea. The U.S. Geological Survey estimates that the Arctic holds an oil and gas bonanza—and companies from Russia to the U.S. are lining up to start exploiting it.

But the dwindling sea ice may actually interfere with that effort. Shell's bid to drill this year had to be halted due to the dangers of drifting ice. In fact, the reduction in sea ice actually makes the Arctic Ocean more hazardous for oil exploration, not less, thanks to massive chunks floating free and much more speedily than in the past. "Overall, sea ice is becoming much more mobile," Barber says. On the other hand, shipping across the Arctic Ocean has become viable for the first time—and weak or rotten ice, as it is called, suggests a path across the topmost part of the planet is already open for at least a short period of time. "We have already reached that point," Barber argues, based on three decades of field experiments on the ice.

The warmer Arctic waters and land have also begun to release methane, a short-lived but potent greenhouse gas that is also the primary hydrocarbon in natural gas fuel. The Arctic Ocean alone contains more methane than the rest of the world's oceans combined—though when and even if such a thawing would contribute a massive methane release remains a "known unknown" in the words of former Defense Secretary Donald Rumsfeld and oceanographer Wieslaw Maslowski of the Naval Postgraduate School in Monterey. "If we release that methane, we will amplify global warming by an unknown amount," Maslowski says. "We have no idea."

Global impacts
On a larger scale, the biggest impact may be the changes in the Arctic's ability to function as a cooling system for the global ocean. Both the Pacific and Atlantic now have warmer waters from the top to the bottom, based on measurements from computerized floats. The Arctic has been functioning as a global air conditioner, losing roughly 350 watts of heat per square meter of open ocean to the atmosphere during the fall storm season as well as the early part of the winter. A warmer Arctic may not be able to shed those greater amounts of heat.

That inability, in turn, will affect the temperature differences between the northern polar region and areas further south. In the atmosphere, it is that temperature gradient that creates and sustains the jet stream—a band of high winds at altitude flowing from west to east that typically steers weather systems in the Northern Hemisphere. "The jet stream becomes more kinked," NSIDC's Meier notes, which allows cold air to spill further south or warm air to penetrate further north [already happening].

The loss of this temperature gradient may also stall weather patterns within the jet stream, allowing particular weather systems to park for a while in one place [already happening]. That may, in turn, create stronger heat waves and droughts or precipitation [already happening]. "If it's a rain pattern that gets stuck in place, you get flooding that becomes a problem," Meier says.

Understanding these so-called "teleconnections" is an urgent area of scientific rsearch, given the potential impacts on farming [already happening] and other vital pursuits. "Our society depends on stable agriculture," Barber notes. It is also likely to be the one that people notice. As climate scientists Jennifer Francis of Rutgers University and Stephen Vavrus of the University of Wisconsin–Madison wrote in a paper laying out how Arctic warming might stall weather patterns via the jet stream: "Gradual warming of the globe may not be noticed by most, but everyone—either directly or indirectly—will be affected to some degree by changes in the frequency and intensity of extreme weather events as greenhouse gases continue to accumulate in the atmosphere."

Warming oceans globally will also allow for more thermal expansion of the waters themselves—the distance between liquid water molecules rises as the water grows warmer. That will raise sea levels further than the current roughly three millimeters per year.

Those warmer ocean waters are already lapping at the icy shores of Greenland, speeding the melt of outlet glaciers for the massive ice sheet. Combined with weather anomalies, like a heat wave that hit central Greenland this July and temporarily melted nearly the entire ice sheet surface, this could presage a more precipitous meltdown in the North. "Extreme melting from past years is preconditioning this year's melt," says ice melt researcher Marco Tedesco of the City College of New York, by melting away any accumulated snowfall from the winter sooner. "It's like putting money in a bank account. If you start spending more money than you put in, you go negative. That is what is happening on the ice sheet."

If Greenland were to melt entirely—which is still a distant prospect according to most glaciologists' estimates—the ice sheet contains enough water to raise sea level by six meters globally. "How many people live within six meter sea level rise of the coast?" Barber asks. "The answer is: too many."

Not all is lost
The seasonal loss of all "Arctic sea ice is one of those tipping points and unfortunately we're going to pass that tipping point," said climate scientist James Hansen, director of the NASA Goddard Institute for Space Studies in New York City, at the same Greenpeace event. "I think we're going to lose that sea ice. The good news is: this tipping point is reversible." Should local conditions change, for whatever reason, however, it is possible the ice could regrow.

After all, the ice spreads anew each cold, dark Arctic winter. Some scientists and environmentalists have even suggested it might be time to attempt geoengineering of one form or another to restore the Arctic's cooler temperatures. "We need to look at the possibility of [solar radiation management], which some people call geoengineering," which could be an option to control or reverse the Arctic meltdown, argues environmentalist Rafe Pomerance, former Deputy Assistant Secretary of State for Environment and Development. "Effectiveness and downsides and what the risks are, we need to know all that." Cutting back on emissions of greenhouse gases other than carbon dioxide—such as methane or black carbon—might also have a bigger impact in the Arctic than elsewhere, given the role that soot plays in melting ice.

There are potential positives to the loss of sea ice to consider as well. Open ocean might permit more carbon-absorbing plankton to bloom, much as happens in the Southern Ocean around Antarctica. "At this time, the Arctic Ocean is a biological desert," notes ecologist Louis Fortier of Laval University in Quebec City. [I would beg to differ -- lots on the sea floor, and plenty of blooms occur under the ice and where there is no ice.] If the plankton blooms, the tiny photosynthesizers pull carbon dioxide out of the air and can serve as the bottom of a food chain that could create new and productive fisheries. Plus, if the plankton die without being eaten or decomposed, they could bury CO2 with them as the tiny corpses fall to the seafloor. In fact, artificially fertilizing such plankton blooms has been tried as a geoengineering technique in the Southern Ocean, with some success.

But that success is unlikely to be repeated in a more watery Arctic Ocean. The northerly sea is "already more productive [in terms of plankton] than the ice-covered ocean of the near-past," says marine biologist Victor Smetacek of the Alfred Wegener Institute for Polar and Marine Research in Germany, who helped lead those biological sequestration experiments in the Southern Ocean. But local conditions, such as a lack of nutrients and a lack of deep- and shallow-ocean water mixing, suggest that the newly open waters of the Arctic Ocean are unlikely to produce massive blooms [there are already massive blooms occurring, but there are possibly related to methane-eating organisms, which is not so good], large fisheries or sequester CO2. "The CO2 sequestration potential of the Arctic is very limited," Smetacek says. The Arctic will not save itself.

Model failure
Regardless of what the Arctic meltdown reveals, what is increasingly clear is that the computer models that scientists rely upon to make predictions have failed to capture the rapid pace of change in the far north. The problem stems from spatial resolutions that are too large (a single grid in a typical computer model encompasses 100 square kilometers) to "see" small but important features such as warm ocean water currents or ice export. And the computing capacity is insufficient to render Arctic cyclones and the role they play in breaking up the ice. "Are the models still too conservative or not?" Maslowski asks of the computer simulations that underpin future predictions. "If this present trend continues, we might be having almost no ice by the end of this decade."

Such a total summer loss of sea ice remains speculative at this point. "I wouldn't expect it to keep going straight down," NSIDC's Meier says. "The ice that is remaining may continue to stay thick [and just where is this supposedly "thick" ice? Have a look at this graphic: http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticictn/nowcast/ictn2012092518_2012092300_035_arcticictn.001.gif] even with more melt and that may be harder to get rid of. The melt could plateau." At the very least, the sea ice is likely to rebound next year, as has happened after every previous ice melt record. "That wouldn't surprise me at all," Meier says. [Actually, the sea ice rebounded after the record 2007 loss, but each year after that represented a decline over the previous year, so it is unlikely that it will rebound a great deal, and certainly not to levels that existed before 2007.]

What may surprise [not if you have been paying attention to the science for the past few years], however, are the global impacts of the already far advanced loss of Arctic sea ice, particularly on the weather. "We need a few more years of empirical evidence to give a confident answer," Hansen says [I personally can't believe he said this -- we may never have a confident answer, but we do know that the weather will (is) becoming averse to food production.] of the challenge of figuring out how the Arctic meltdown will affect the rest of the globe. Thanks to ever increasing greenhouse gas emissions trapping more and more heat, the world will find out this winter—and for many years to come.

"There's evidence in the paleo-climate record that the climate system is capable of changing quite rapidly," Barber notes. "We're moving into new territory and the impacts of that are unknown scientifically." [Yup -- it's the "no-analogue" world.]

http://news.yahoo.com/ice-free-arctic-summers-bring-100100621.html

"Trends in Arctic sea ice extent from CMIP5, CMIP3 and observations," Julienne C. Stroeve et al., GRL 39 (2012); doi: 10.1029/2012GL052676

Geophysical Research Letters, 39 (2012) L16502; doi: 10.1029/2012GL052676

Trends in Arctic sea ice extent from CMIP5, CMIP3 and observations

Key Points

• CMIP5 models continue to underestimate rate of sea ice loss
• CMIP5 models are more consistent with observations than CMIP3
• CMIP5 suggests 60% of 1979-2011 rate of decline is externally forced

Julienne C. Stroeve (National Snow and Ice Data Center, Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Boulder, CO, U.S.A.), Vladimir Kattsov (Voeikov Main Geophysical Observatory, Roshydromet, St. Petersburg, Russia) and  Andrew Barrett and Mark Serreze (National Snow and Ice Data Center, Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Boulder, CO, U.S.A.),  Tatiana Pavlova (Voeikov Main Geophysical Observatory, Roshydromet, St. Petersburg, Russia), Marika Holland (National Center for Atmospheric Research, Boulder, CO, U.S.A.) and Walter N. Meier (National Snow and Ice Data Center, Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Boulder, CO, U.S.A.)

Abstract

The rapid retreat and thinning of the Arctic sea ice cover over the past several decades is one of the most striking manifestations of global climate change. Previous research revealed that the observed downward trend in September ice extent exceeded simulated trends from most models participating in the World Climate Research Programme Coupled Model Intercomparison Project Phase 3 (CMIP3). We show here that as a group, simulated trends from the models contributing to CMIP5 are more consistent with observations over the satellite era (1979–2011). Trends from most ensemble members and models nevertheless remain smaller than the observed value. Pointing to strong impacts of internal climate variability, 16% of the ensemble member trends over the satellite era are statistically indistinguishable from zero. Results from the CMIP5 models do not appear to have appreciably reduced uncertainty as to when a seasonally ice-free Arctic Ocean will be realized.

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Received 7 June 2012; accepted 17 July 2012; published 25 August 2012.

Stroeve, J. C., V. Kattsov, A. Barrett, M. Serreze, T. Pavlova, M. Holland, and W. N. Meier (2012), Trends in Arctic sea ice extent from CMIP5, CMIP3 and observations, Geophys. Res. Lett., 39, L16502, doi: 10.1029/2012GL052676.

http://www.agu.org/pubs/crossref/2012/2012GL052676.shtml

NOAA: Summer weighing heavily on Greenland Ice Sheet

Summer weighing heavily on Greenland Ice Sheet

by Rebecca Lindsey, NOAA's Climate Watch Magazine, August 2, 2012

In late July, NASA announced that satellites had detected signs of melting across virtually the entire surface of the Greenland Ice Sheet in mid-July, even at the two-mile-high summit of the ice cap—a first for the satellite record and a historically rare occurrence based on ice core data.

The unusual melting event followed several months during which high pressure systems repeatedly parked over Greenland. As many a weather forecaster has explained, high pressure generally leads to calm winds and sunny skies, both of which boost temperatures during the all-day sunshine of mid-summer at high latitudes.

The map on the left shows the difference from average pressure at the 700 millibar pressure level from May-July 2012 compared to the 1981-2010 average. Gold colors indicate higher-than-average pressure. A large dome of high pressure camped over Greenland and the Northwest Atlantic this summer. The influence on temperatures (map on right) was dramatic. Temperature anomalies at the same altitude were as much as 11 degrees Fahrenheit warmer than average over Greenland.

At Summit Station, a research camp at the top of the Greenland ice sheet, the temperatures made a clear excursion above freezing in mid-July, lending supporting evidence to the satellite observations of ice melting even at the ice sheet’s highest location. Temperatures flirted with the melting threshold again late in the month.

The graph below shows hourly average summer temperatures at Summit Station, Greenland. Gray lines show temperatures from 2005-2011; 2012 summer temperatures through late July are shown in red. Even compared to the past 7 years—globally some of the warmest on record—the 2012 summer temperatures at Summit Station stand out for their repeated warmth.

Graph adapted from original by Mike Schnaubelt and Christopher Shuman, NASA-GSFC, based on NOAA data provided by Tom Mefford.

Strong anomalies of both high and low pressure come and go across Greenland and the North Atlantic over the span of weeks to months, and they exert a powerful influence on regional weather and seasonal climate. In addition to favoring cloudless skies, high pressure tends to bring southerly winds across western Greenland, providing another warming influence.

Research published earlier this year found that since the late 1950s, the 6 warmest summers and 5 of the 6 largest melt years in Greenland have occurred since 2000. A similar “dome” of persistent high pressure was common to each of the episodes, but it is probably not the sole cause of the unusual warmth and melting.

Scientists continue to investigate how the anomalous atmospheric circulation pattern interacts with other climate conditions, including natural cycles of ocean temperature in the North Atlantic and human-caused climate change, to influence the summer melt rate on the Greenland Ice Sheet.

References
Hanna, E., Jones, J. M., Cappelen, J., Mernild, S. H., Wood, L., Steffen, K., & Huybrechts, P. (2012, in press). The influence of North Atlantic atmospheric and oceanic forcing effects on 1900-2010 Greenland summer climate and ice melt/runoff. International Journal of Climatology. doi:10.1002/joc.3475

Links
Satellites Observe Widespread Melting on Greenland
NOAA Summit June-August Temperatures—1-hour averages
Greenland Ice Sheet Getting Darker
Greenland Ice Sheet Surface Melting, 2000-2011

Reviewed by James Partain, Jim Overland, John Nielsen-Gammon, Ted Scambos, Walt Meier, Christopher Shuman, and Edward Hanna.

http://www.climatewatch.noaa.gov/article/2012/summer-weighing-heavily-on-greenland-ice-sheet

Richard Black, BBC: New warning on Arctic sea ice melt by Wieslaw Maslowski's team, causing albedo flip and Arctic amplification

New warning on Arctic sea ice melt

by Richard Black, Environment correspondent, BBC News, April 7, 2011

The researchers are now working with a new computer model for Arctic sea ice

Continue reading the main story

Related Stories

• Arctic sea ice melt 'even faster'
• Arctic losing long-term ice cover
• Arctic summers ice-free 'by 2013'

Scientists who predicted a few years ago that Arctic summers could be ice-free by 2013 now say summer sea ice will probably be gone in this decade.

The original prediction, made in 2007, gained Wieslaw Maslowski's team a deal of criticism from some of their peers.

Now they are working with a new computer model -- compiled partly in response to those criticisms -- that produces a "best guess" date of 2016.

Their work was unveiled at the European Geosciences Union (EGU) annual meeting.

The new model is designed to replicate real-world interactions, or "couplings," between the Arctic ocean, the atmosphere, the sea ice and rivers carrying freshwater into the sea.

"In the past... we were just extrapolating into the future assuming that trends might persist as we've seen in recent times," said Dr Maslowski, who works at Naval Postgraduate School in Monterey, California.

"Now we're trying to be more systematic, and we've developed a regional Arctic climate model that's very similar to the global climate models participating in Intergovernmental Panel on Climate Change (IPCC) assessments," he told BBC News.

"We can run a fully coupled model for the past and present and see what our model will predict for the future in terms of the sea ice and the Arctic climate."

And one of the projections it comes out with is that the summer melt could lead to ice-free Arctic seas by 2016 -- "plus or minus three years."

It does not make predictions about the Greenland ice cap.

Thin evidence

One of the important ingredients of the new model is data on the thickness of ice floating on the sea.

Satellites are increasingly able to detect this, usually by measuring how far the ice sits above the sea surface -- which also indicates how far the ice extends beneath.

Inclusion of this data into the team's modelling was one of the factors causing them to retrench on the 2013 date, which raised eyebrows -- and subsequently some criticism -- when it emerged at a US science meeting four years ago.

Since the spectacularly pronounced melting of 2007, a greater proportion of the Arctic Ocean has been covered by thin ice that is formed in a single season and is more vulnerable to slight temperature increases than older, thicker ice.

Even taking this into account, the projected date range is earlier than other researchers believe likely.

But one peer -- Dr Walt Meier from the US National Snow and Ice Data Center in Boulder, Colorado -- said the behaviour of sea ice becomes less predictable as it gets thinner.

"[Maslowski's] is quite a good model; one thing it has is really high resolution, it can capture details that are lost in global climate models," he said.

"But 2019 is only eight years away; there's been modelling showing that [likely dates are around] 2040-2050, and I'd still lean towards that.

"I'd be very surprised if it's 2013 -- I wouldn't be totally surprised if it's 2019."

Crystal method

The drastic melt of 2007 remains the record loss of ice area in the satellite era, although subsequent years have still been below the long-term average.

But some researchers believe 2010's melt was equally as notable as 2007's, given weather conditions that were favourable to the durability of ice.

Although many climate scientists and environmental campaigners are seriously concerned about the fate of the Arctic sea ice, for other parts of society and other arms of government its degradation presents challenges and opportunities.

The Russian and Canadian governments, for example, are looking to the opportunities for mineral exploitation that will arise; while the US military has expressed concern about losing a natural defence around the country's northern border for part of the year.

"I'm not trying to be alarmist and not trying to say 'we know the future because we have a crystal ball,' " said Dr Maslowski.

"Basically, we're trying to make policymakers and people who need to know about climate change in the Arctic realise there is a chance that summer sea ice could be gone by the end of the decade.

"For the national interest, the defence interest, I think it's important to realise that 2040 is not a crystal ball prediction."

http://www.bbc.co.uk/news/science-environment-13002706