Wieslaw Maslowski of the US Naval Postgraduate School predicts lower-bound summer ice free Arctic by 2016

Is conventional modelling out of pace with speed and abruptness of global warming?

Greenpeace icebreaking ship, Arctic Sunrise, among broken floes of Arctic sea ice, photographed from the air. This image was taken in the Fram Strait, in the month that the sea ice coverage receded to the second lowest extent since records began. Photograph: Nick Cobbing

by Nafeez Ahmed, The Guardian, December 9, 2013

An ongoing US Department of Energy-backed research project led by a US Navy scientist predicts that the Arctic could lose its summer sea ice cover as early as 2016 – 84 years ahead of conventional model projections.

The project, based out of the US Naval Postgraduate School's Department of Oceanography, uses complex modelling techniques that make its projections more accurate than others.

A paper by principal investigator Professor Wieslaw Maslowski in the Annual Review of Earth and Planetary Sciences sets out some of the findings so far of the research project:

"Given the estimated trend and the volume estimate for October–November of 2007 at less than 9,000 km3, one can project that at this rate it would take only 9 more years or until 2016 ± 3 years to reach a nearly ice-free Arctic Ocean in summer. Regardless of high uncertainty associated with such an estimate, it does provide a lower bound of the time range for projections of seasonal sea ice cover."

The paper is highly critical of global climate models (GCM) and even the majority of regional models, noting that "many Arctic climatic processes that are omitted from, or poorly represented in, most current-generation GCMs" which "do not account for important feedbacks among various system components." There is therefore "a great need for improved understanding and model representation of physical processes and interactions specific to polar regions that currently might not be fully accounted for or are missing in GCMs."

According to the US Department of Energy describing the project's development of the Regional Arctic System Model (RASM):

"Given that the Arctic is warming faster than the rest of the globe, understanding the processes and feedbacks of this polar amplification is a top priority. In addition, Arctic glaciers and the Greenland Ice Sheet are expected to change significantly and contribute to sea level rise in the coming decades."

Such Arctic changes "could have significant ramifications for global sea level, the ocean thermohaline circulation and heat budget, ecosystems, native communities, natural resource exploration, and commercial transportation."

The regional focus of RASM permits "significantly higher spatial resolution" to represent and evaluate the interaction of "important fine-scale Arctic processes and feedbacks," such as:

"... sea ice deformation, ocean eddies, and associated ice–ocean boundary layer mixing, multiphase clouds as well as land–atmosphere–ice–ocean interactions."

The role of the Department of Energy in backing the research is not surprising considering that President Obama's national Arctic strategy launched in May is focused on protecting commercial and corporate opportunities related to control of the region's vast untapped oil, gas and mineral resources.

The model coheres with the predictions of several other Arctic specialists – namely Prof Peter Wadhams, head of polar ocean physics at Cambridge University and Prof Carlos Duarte, director of the Ocean Institute at the University of Western Australia – who see the disappearance of the Arctic sea ice in the summer of 2015 as likely.

Prof Wadhams is co-author of the controversial Nature paper which calculated the potential economic costs of climate change based on a scenario of 50 Gigatonnes (Gt) of methane being released this century from melting permafrost at the East Siberia Arctic Shelf (ESAS), a vast region of shallow-water covered continental crust. The scenario was first postulated by Natalia Shakhova and Igor Semiletov of the International Arctic Research Centre at the University of Alaska, Fairbanks.

In 2010, Shakhova's team published results showing that 7 teragrammes of methane was bubbling to the surface annually in the ESAS. Last month, she released a new paper in Nature Geoscience updating these findings on the basis of more rigorous measurements using an unmanned underwater vehicle with advanced sonar capability. She found that annual bottom water temperatures have increased over the last 14 years, correlating with a release of about 17 teragrammes of methane a year, accentuated by storms. This conservative estimate is more than double the earlier assessment.

However, the source of these methane emissions remains a matter of dispute, as other scientists investigating the phenomenon point out that while large deposits of methane hydrates could be breaking up, the other possibility is a slow leak of methane that has already gone on for hundreds of years. Christian Berndt, of the GEOMAR/Helmholz Centre for Ocean Research, has speculated that both phenomena could be going on at once, but he admits, "We have no proof."

Despite their latest study uncovering higher levels of methane than previously recognised, Shakhova has also distanced herself from the 'methane bomb' scenario she had once previously posited, noting a lack of direct evidence for the scenario.

Commenting on the study, the US National Snow & Ice Data Centre (NSIDC) observes:

"Ship-based observations show that methane concentrations in the air above the East Siberian Sea Shelf are nearly twice as high as the global average... Layers of sediment below the permafrost slowly emit methane gas, and this gas has been trapped for millennia beneath the permafrost. As sea levels rose at the end of the ice age, the shelf was once again covered by relatively warm ocean water, thawing the permafrost and releasing the trapped methane... In the short-term... methane has a global warming potential 86 times that of carbon dioxide."

Most scientists agree that more research is needed to determine the source and nature of these methane emissions.

But scientists also largely agree that an ice free Arctic in the summer could have serious consequences for the global climate. Some research has pointed out a link between the warming Arctic and changes in the jet stream, contributing to unprecedented weather extremes over the last few years. These extreme events in turn have dramatically impacted crop production in key food basket regions.

A landmark new study in Nature Climate Change finds the melting of the sea ice over the last 30 years at a rate of 8% per decade is directly linked to extreme summer weather in the US and elsewhere in the form of droughts and heatwaves. Lead study author Quihang Tang at the Institute of Geographic Sciences and Natural Resources Research in Beijing said:

"As the high latitudes warm faster than the mid-latitudes because of amplifying effects of melting ice, the west-to-east jet-stream wind is weakened. Consequently, the atmospheric circulation change tends to favour more persistent weather systems and a higher likelihood of summer weather extremes."

The new study supplements earlier research published in Geophysical Research Letters demonstrating a link between Arctic sea ice loss and extreme weather particularly in both the summer and winter, including prolongation of "drought, flooding, cold spells, and heat waves."

Last year Prof Duarte was lead author of a paper in the Royal Swedish Academy of Science's journal AMBIO warning that the Arctic was at risk of passing critical "tipping points" that could lead to a cascading "domino effect once the summer sea ice is lost." Prof Duarte said at the time:

"If set in motion, they can generate profound climate change which places the Arctic not at the periphery but at the core of the Earth system. There is evidence that these forces are starting to be set in motion. This has major consequences for the future of human kind as climate change progresses."

Dr Nafeez Ahmed is executive director of the Institute for Policy Research & Development and author of A User's Guide to the Crisis of Civilisation: And How to Save It among other books. Follow him on Twitter @nafeezahmed

http://www.theguardian.com/environment/earth-insight/2013/dec/09/us-navy-arctic-sea-ice-2016-melt

NPS researchers predict summer Arctic ice might disappear by 2016, 84 years ahead of schedule

by David Schmalz, Monterey County Weekly, November 27, 2013

Tucked away on the third floor of the Naval Postgraduate School’s building of Engineering and Applied Sciences, a small team of researchers is leading an effort that will change the way the world thinks about the world. Their project is the Regional Arctic System Model (RASM), and it is arguably the most advanced – and accurate – Arctic climate model in existence.

Nick Coury

Lt. Dominic DiMaggio describes the area captured by NPS’s innovative Arctic climate model, a project involving 25 researchers and graduate students from 10 institutions.

On a recent, sunny winter day, U.S. Navy Lt. Dominic DiMaggio – a master’s student in physical oceanography and meteorology and a RASM team member – lays out the model’s virtues and complexities, casually throwing around terms like “parameterization” and “highly non-linear functions.”

Then, almost 60 dizzying minutes later, he just as casually points to a graph showing a RASM projection for melting Arctic sea ice, a phenomenon that occurs every summer but has been accelerated by climate change: By the summer of 2016, the Arctic Ocean could be ice-free, opening the door to vast reserves of fossil fuel, and eventually, freeing up a shipping lane between Europe and Asia.

NPS Professor Wieslaw Maslowski, who leads the team of researchers behind RASM, says 2016 is at “the lower bound” of the current range of projections, while DiMaggio calls it “an aggressive interpretation” of RASM. But most conventional climate models predict the Arctic won’t have a sea ice-free summer until 2100. So why is the RASM model so different?

Mainly, it’s a matter of scope. Because most climate models are projecting the global climate, there is not enough computing power to account for what can often be key regional details.

One example DiMaggio gives is the Bering Strait, a narrow strip of water that is too small (51 miles wide) to be accurately accounted for in the wider lens of global models, but which “is significant in its impacts to the central Arctic.”

The amount of detail that RASM is able to capture in the Arctic is at least 10 times greater than a global model, and not only calculates projections based on air, ocean and ice conditions (which are standard in global models), but also includes inputs for land and riverflow.

“We’re modeling river runoff, the permafrost, the glaciers, even the chemical and biological processes,” says DiMaggio. “The ocean isn’t just the water, it’s the entire environment. And that’s what we’re trying to capture.”

RASM’s findings will help inform the Navy’s understanding of a region that is home to over a thousand miles of U.S. coastline, and which is changing faster than many expected, a reality charged with geopolitical implications. The Navy predicts the potential for extracting fossil fuels and minerals, as well as significantly shorter shipping routes, will likely attract commercial interests.

The stark image of an ice-free Arctic, meanwhile, might also impact the climate change discussion, one that Maslowski hopes “will be a critical argument against skeptics of global warming.”

RASM has the potential to greatly alter current global climate models.

“We’re hoping global modeling groups will use what we’ve learned to improve their models,” Dimaggio says, “so the decision makers have a better understanding of what’s actually happening.”

http://www.montereycountyweekly.com/news/local_news/article_f0d1fc46-56dc-11e3-9766-001a4bcf6878.html

David Spratt: Is climate change already dangerous? Part IV. Tipping points and climate modelling

by David Spratt, Climate Code Red, September 24, 2013
Fourth in a series
A tipping point may be understood as a step change, or passing of a critical threshold, in a major earth-climate system component, where a small perturbation (a small push or change) unleashes a bigger change in the component.  Potsdam Institute Director, Prof. Hans Joachim Schellnhuber, says that tipping points “identify the most vulnerable components (tipping elements) of the Earth System, the critical warming thresholds where the respective Earth System elements flip into a qualitatively new state.”  These elements include ecosystems, major ocean and atmospheric circulation patterns, the polar ice sheets, and the land- and ocean-based carbon stores.
This process is often tied to positive feedbacks, where a change in a component leads to other changes that eventually “feed back” onto the original change to amplify it.  The classic case in global warming (or, in reverse, cooling) is the ice-albedo feedback, where decreases (increases) in the ice cover area change surface reflectivity (albedo), trapping more (less) heat and producing further ice loss (gain).

In some cases, passing one threshold will trigger further threshold events, for example where substantial releases from permafrost carbon stores increase warming, releasing more permafrost carbon but also pushing other systems, for example parts of the Antarctic ice sheet, past a threshold point.
Once a tipping point is crossed, it is irreversible (under natural conditions) within certain time frames, so the consequence is to significantly affect the earth’s climate and ecosystems, for example by raising temperatures or greenhouse gas levels, or changing the efficiency of the land and ocean carbon sinks.  Given enough time and the right conditions, most processes (but not extinctions, for example) can be reversed.
In a period of rapid warming, most major tipping points once crossed (ice sheet loss, large-scale land carbon store releases such as permafrost) are irreversible on human time frames running to a few generations, principally due to the longevity of atmospheric CO2 (several thousand years). Large-scale human interventions in slow-moving earth system tipping points might allow a tipping point to be reversed (for example, a large-scale atmospheric CO2 drawdown program, or solar radiation management).
There is discussion, for example, that Arctic sea-ice loss is “easily reversible” in a cooling world, but that is easier said than done.  That would require greenhouse gas levels to be reduced significantly, below the level equivalent to the temperature at which the sea-ice system tipped in 2007, to produce a sufficiently cooler world.  This would be around 300–325 ppm CO2, compared to the present level of 400 ppm, so it is not so “easy” in the real world.
The scientific literature on tipping points is relatively recent, with a significant contribution by Lenton, Held et al. in 2008 on “Tipping elements in the Earth’s climate system” in an issue of the journal Proceedings of the National Academy of Sciences devoted to the subject. However, our knowledge is limited because “a system-level understanding of critical Arctic processes and feedbacks is still lacking” (Maslowski, Kinney et al.) and “no serious efforts have been made so far to identify and qualify the interactions between various tipping points” (Schellnhuber).
 
Climate models are not yet good at dealing with tipping points. This is partly in the nature of tipping points, where a particular and complex confluence of factors suddenly change a climate system characteristic and drives it to a different state. To model this, all the contributing factors and their forces have to well identified, as well as their particular interactions, plus the interactions between tipping points. Duarte, Lenton et al. conclude that “complex, nonlinear systems typically shift between alternative states in an abrupt, rather than a smooth manner, which is a challenge that climate models have not yet been able to adequately meet.”
The classic case was the Arctic sea ice “big melt” in 2007. Many models, including those on which the 2007 IPCC report had relied to conclude that Arctic sea-ice was pretty much likely to remain till the end of the century, did not fully capture the dynamics of sea-ice loss. Thus when in 2007 the summer sea-ice extent dropped radically compared to previous years, some model-oriented researchers exclaimed that the Arctic was melting “a hundred years ahead of schedule.”
Even today, papers are still being published with modelling that suggests a sea-ice free Arctic will not occur till mid-century. Given the observations, it’s difficult not to conclude that given a choice between their models and real-world observations, some modellers will always choose the former. 
In an overview of the current state of Arctic climate research, Maslowski, Kinney et al. conclude that: “Model limitations are hindering our ability to predict the future state of Arctic sea ice,” and that the majority of general climate models (GCMs) including those used in IPCC (2007) “have not been able to adequately reproduce observed multi-decadal sea-ice variability and trends in the pan-Arctic region,” and their ensemble mean trend in September Arctic sea-ice extent “is approximately 30 years behind the observed trend.”
For example, what would be the impact of a sea-ice-free Arctic summer and the consequent amplified regional warming on the stability of the Greenland Ice Sheet (GIS)? Research does not yet provide a robust framework for considering such questions, yet most scientists if asked for their expert elicitation would probably say that it is hard to imagine the GIS doing anything other than melting at an accelerating rate and passing a critical tipping point in such circumstances.
The sea-ice model that has performed best (acronym NAME), is one of a new range of more specialised regional climate models developed by Dr Wieslaw Maslowski and colleagues. Maslowski is highly regarded, in part because his position at the American Naval Postgraduate School has given him unique access to half a century of Arctic sea-ice thickness scans from polar US military submarines. Maslowski told BBC News:

In the past… we were just extrapolating into the future assuming that trends might persist as we’ve seen in recent times. 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 IPCC assessments. 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. 

He emphasizes “the need for detailed analyses of changes in sea ice thickness and volume to determine the actual rate of melt of Arctic sea ice,” and concludes that:

The modeled evolution of Arctic sea ice volume appears to be much stronger correlated with changes in ice thickness than with ice extent as it shows a similar negative trend beginning around the mid-1990s. When considering this part of the sea ice–volume time series, one can estimate a negative trend of −1,120 km3 year−1 with a standard deviation of +/-2,353 km3 year−1 from combined model and observational estimates for October–November 1996–2007. Given the estimated trend and the volume estimate for October–November of 2007 at less than 9000 km3, one can project that at this rate it would take only 9 more years or until 2016 +/-3 years to reach a nearly ice-free Arctic Ocean in summer. Regardless of high uncertainty associated with such an estimate, it does provide a lower bound of the time range for projections of seasonal sea ice cover.

The point cannot be emphasized enough that the best-performing Arctic sea-ice model projects 2016 +/-3 years to reach a nearly ice-free Arctic Ocean.

Arctic sea ice volumes estimates from observations and from the NAME model
(Maslowski, Kinney et al., 2012, Figure 9)

 The non-linear problem still plagues many Arctic GCMs, and indeed parts of the IPCC process which largely excludes tipping points and carbon cycle feedbacks from consideration, exemplified by the 2007 IPCC’s reticence on sea level rises. Several fundamental projections found in IPCC reports have consistently underestimated real-world observations in at least eight key areas.  In its February 2007 report on the physical basis of climate science, the IPCC said that Arctic sea-ice was responding sensitively to global warming: ‘While changes in winter sea-ice cover are moderate, late summer sea-ice is projected to disappear almost completely towards the end of the twenty first century.’ And apparently the forthcoming 2013 IPPC AR5 has omitted consideration of permafrost feedbacks – another glaring example of that body’s scientific reticence (Romm, 2012).

http://www.climatecodered.org/2013/09/is-climate-change-already-dangerous-4_24.html

David Spratt: Is climate change already dangerous? Part II. Arctic sea ice

by David Spratt, Climate Code Red, September 19, 2013

Second in a series:  Arctic sea ice

 

Download full report

On 16 September 2012, Arctic sea-ice reached its minimum extent for the 2012 northern summer of 3.41 million square kilometres, the lowest seasonal minimum extent in the satellite record since 1979, and just half of the average area for the 1979–2000 period.  There was a loss of 11.83 million square kilometres of ice from the maximum extent on 20 March 2012.  This was the largest summer ice extent loss in the satellite record, more than one million square kilometres greater than in any previous year.

Two-thirds of the loss of sea-ice extent has happened in the 12 years since 2000, and the process appears to be accelerating.  From 1979 to 1983 in the Arctic, the sea ice summer minimum covered an average of just over 51% of the ocean.  It fell to just 24% of the Arctic ocean surface in 2012.

Not only does the sea ice cover a smaller area of ocean in summer, it is also thinning rapidly.  The sea-ice volume is now down to just one-fifth of what it was in 1979.  The PIOMAS project, which captures the process of sea-ice retreat far better than any other general climate models, finds a September 2012 minimum of 3,263 km3 of ice.  Contrasted with the figure of 16,855 km3 in 1979, more than 80% of ice volume has been lost.

Arctic sea-ice volume loss (based on PIOMAS)

It is now clear that the Arctic is heading quickly for summer periods free of sea ice.  A linear extrapolation of sea-ice mass loss suggests it may occur within a decade or so.  An exponential fit, which is a better fit for the current data, suggests it might occur within a few years . At time of publication, the minimum volume figure for 2013 was not available, but it may be a little higher than the record low of 2012, and similar to 2011.

Because climate models generally have been poor at dealing with Arctic sea-ice retreat , expert elicitations play a key role in considering whether the Arctic has passed a very significant and “dangerous” tipping point.  Here’s what leading figures in the research field say:

PIOMAS Arctic sea ice annual minimum volume (black) plus “best fit” trend (red)

• Dr Tim Lenton of the University of Exeter told the March 2012 Planet Under Pressure
conference that sea ice since 2007 had departed from model predictions, and that disappearance of Arctic sea ice has crossed a “tipping point” that could soon make ice-free summers a regular feature across most of the Arctic Ocean.  This conclusion was drawn from a subsequently published paper  which finds that “an abrupt and persistent increase in the amplitude of the seasonal Arctic sea-ice cover in 2007 which we describe as a (non-bifurcation) ‘tipping point.’ ”  If 2007 is the crucial point on the Arctic sea-ice decline timeline, it is also important to note that global warming above pre-industrial was 0.76 ºC at that time. At equilibrium, a 0.76 ºC rise is equivalent to CO2 levels of 335 ppm, so the “safe boundary” of 350 ppm already looks too optimistic from this perspective.
• The Australian Climate Commissioner, Professor Will Steffen, told The Age in September last year: “I’m pretty certain that we have now passed the tipping point for Arctic sea ice.”
• Dr Seymour Laxon, of the Centre for Polar Observation and Modelling at University College London, says: “Preliminary analysis of our data indicates that the rate of loss of sea-ice volume in summer in the Arctic may be far larger than we had previously suspected…  Very soon we may experience the iconic moment when, one day in the summer, we look at satellite images and see no sea-ice coverage in the Arctic, just open water.”
• Professor Carlos Duarte, Director of University of WA’s Oceans Institute, says an Arctic “snowballing” situation would prove as hard to slow down as a runaway train.  He says melting of the ice is accelerating faster than any of the models could predict and the prospect of an Arctic Ocean free of ice had been brought forward to 2015, compared with a prediction in 2007 that at least one-third of the normal extent of sea ice would remain in summer in 2100.  Duarte says that the Arctic region is fast approaching a series of imminent “tipping points” which could trigger a domino effect of large-scale climate change across the entire planet with “major consequences for the future of humankind as climate change progresses.”
• US National Snow and Ice Data Centre Director Dr Mark Serreze told Climate Progress in 2010: “I stand by my previous statements that the Arctic summer sea-ice cover is in a death spiral.  It’s not going to recover.”   Without human intervention to drive recovery, the evidence is very clear that Serreze is right.
• Professor Peter Wadhams, of Cambridge University and the Catlin Arctic Survey, and a leading authority on the polar regions, concludes in a research paper: “Has Arctic sea ice reached a tipping point? I believe that it has...”

Wadhams explains:

I have been predicting [the collapse of sea ice in summer months] for many years.  The main cause is simply global warming: as the climate has warmed there has been less ice growth during the winter and more ice melt during the summer… in the end the summer melt overtook the winter growth such that the entire ice sheet melts or breaks up during the summer months.  This collapse, I predicted would occur in 2015–16 at which time the summer Arctic (August to September) would become ice-free.  The final collapse towards that state is now happening and will probably be completed by those dates.  As the sea ice retreats in summer the ocean warms up (to +7 ºC in 2011) and this warms the seabed too.  The continental shelves of the Arctic are composed of offshore permafrost, frozen sediment left over from the last ice age.  As the water warms, the permafrost melts and releases huge quantities of trapped methane, a very powerful greenhouse gas so this will give a big boost to global warming.

Wadhams’ analysis relies in part on a new, more specialised regional climate model, acronym NAME, developed by Dr Wieslaw Maslowski and colleagues. NAME is head and shoulders above other models so far in projecting and replicating sea-ice losses.“The future of Arctic sea ice” found that: “Given the estimated trend and the volume estimate for October–November of 2007 at less than 9,000 cubic kms, one can project that at this rate it would take only 9 more years or until 2016 +/-3 years to reach a nearly ice-free Arctic Ocean in summer.”

The impacts of lengthening periods of sea-ice-free Arctic summers are significant and will, together with warming already “in the system,” push more climate elements past their tipping points. Our knowledge is limited because “a system-level understanding of critical Arctic processes and feedbacks is still lacking” (Maslowski, Kinney et al.) and “no serious efforts have been made so far to identify and qualify the interactions between various tipping points” (Schellnhuber).

However, we do know that the Arctic is warming quicker than the global average.  Duarte, Lenton et al. find that: “Warming of the Arctic region is proceeding at three times the global average, and a new ‘Arctic rapid change’ climate pattern has been observed in the past decade.” Reductions in the sea-ice cover are believed to be the largest contributor toward Arctic amplification. Maslowski, Kinney et al. note that: “a warming Arctic climate appears to affect the rate of melt of the Greenland ice sheet, Northern Hemisphere permafrost sea-level rise, and global climate change.”

The sea-ice cover in June is about 2% of the earth’s surface.  Replacing that during summer in the Arctic with darker, more heat-absorbing ocean waters is equivalent to about 20 years of human greenhouse emissions, or about +0.5 ºC of warming, according to Peter Wadhams.  This is consistent with a study by Stephen Hudson, which found that, if the Arctic were ice-free for one month a year plus associated ice-extent decreases in other months, then, without taking cloud changes into account, the global impact would be about +0.2 ºC of warming.  If there were no ice at all during the main three months of sunlight, the increase would be +0.5 ºC.

The consequences of the Arctic big melt and the subsequent regional amplification and global temperature increase will include:

• Accelerated melting of the Greenland ice sheet, very likely pushing it past its tipping point;
• Pushing Arctic temperatures into a range that will trigger large-scale Arctic carbon store releases of methane and CO2, a positive feedback which will drive further warming;
• Further destabilisation of the Jet Stream and hence more northern hemisphere extreme weather; and
• The destruction of the Arctic ecosystem, which is already well under way. This has been chronicled by many researchers and organisations, including the Center for Biological Diversity and Care for the Wild International.  In the Arctic, the rate of climate change is now faster than ecosystems can adapt to naturally, and the fate of many Arctic marine ecosystems is clearly connected to that of the sea ice (Duarte, Lenton et al.). I remember well attending an Academy of Science conference in Canberra in May 2008 where the international guest speaker was Dr Neil Hamilton, then head of the WWF Arctic Programme. He told a somewhat stunned audience that the WWF was not trying to preserve the Arctic ecosystem because “it was no longer possible to do so.”  Whilst the campaign to stop the development of an oil and gas industry in the Arctic is necessary (if only to prevent more global warming emissions), the claim that in so doing we can thereby “save the Arctic” seems wide of the mark.

Greenland Ice Sheet

Complex, non-linear systems typically shift between alternative states in an abrupt, rather than a smooth manner, so it is often difficult to identify tipping points in advance. Only a few Arctic specialists, including Ted Scambos, Mark Serreze and Ron Lindsay, said prior to 2007 that the sea ice was close to a phase change.

If it is sometimes hard to see tipping points coming, it is also too late to be wise after the fact. And that is precisely the case with the Greenland Ice Sheet (GIS).

Current-generation climate models are not yet all that helpful on GIS. They have a poor understanding of the processes involved, and acceleration, retreat and thinning of outlet glaciers are not represented.

Recent research (next post) puts a lower boundary of 0.8 ºC on GIS’s tipping point, a warming level we have already reached.  In July 2013, a new study found that stretches of ice on the coasts of Antarctica and Greenland are at risk of rapidly cracking apart and falling into the ocean: “rapid iceberg discharge is possible in regions where highly crevassed glaciers are grounded deep beneath sea level, indicating portions of Greenland and Antarctica that may be vulnerable to rapid ice loss through catastrophic disintegration.”

In 2012, GIS melting shattered the seasonal record; the duration of GIS melting was the longest yet observed; a rare, nearly ice sheet-wide melt event (covering as much as 97% of the ice sheet’s surface on a single day) occurred in July; and the reflectivity of GIS, particularly at the high elevations that were involved in the mid-July melt event, declined to record lows. Unfortunately, data from the GRACE satellite observation of GIS is not yet of sufficient duration to robustly describe the melt trend, but observations are that the rate of melting is increasing, and many glaciers are picking up speed. Since 2001, the Jakobshavn Glacier, the world’s fastest flowing glacier, has more than doubled its flow rate, and total GIS mass loss in 2011 was 70% larger than the 2003–2009 average annual loss rate.

Previously, studies have estimated that it would take centuries to millennia for new climates to increase the temperature deep within ice sheets such as GIS. But a new study finds that when the influence of meltwater (which drains through cracks in an ice sheet and can warm the sheet from the inside, softening the ice and letting it flow faster) is considered, warming can occur within decades and produce rapid accelerations. Lead author Thomas Phillips says this research “could imply that ice sheets can discharge ice into the ocean far more rapidly than currently estimated,” thus requiring a re-assessment of the rate of both future sea-level rises and the rate of mass loss of GIS. 
  
Has Greenland passed its tipping point?  What would be the impact of a sea-ice-free Arctic summer and the consequent amplified regional warming on the stability of the Greenland ice sheet? Research does not yet provide a robust framework for considering such questions, yet most scientists if asked for their expert elicitation would probably say that it is hard to imagine the GIS doing anything other than actively de-glaciating at an accelerating rate and passing a critical tipping point in such circumstances.

NASA climate research chief Dr James Hansen answered this question in the affirmative, in a peer-reviewed paper in 2007:

Could the Greenland ice sheet survive if the Arctic were ice-free in summer and fall? It has been argued that not only is ice sheet survival unlikely, but its disintegration would be a wet process that can proceed rapidly. Thus an ice-free Arctic Ocean, because it may hasten melting of Greenland, may have implications for global sea level, as well as the regional environment, making Arctic climate change centrally relevant to definition of dangerous human interference.”

In the same year, Hansen said that today’s level of CO2 was enough to cause Arctic sea-ice cover and massive ice sheets such as in Greenland to eventually melt away: “I think in most of these cases, we have already reached the tipping point.”

And last year, Hansen told Bloomberg that: “Our greatest concern is that loss of Arctic sea ice creates a grave threat of passing two other tipping points – the potential instability of the Greenland ice sheet and methane hydrates… These latter two tipping points would have consequences that are practically irreversible on time scales of relevance to humanity.”

Glaciologist Jason Box told reporters at the annual conference of the American Geophysical Union last December: “In 2012 Greenland crossed a threshold where for the first time we saw complete surface melting at the highest elevations in what we used to call the dry snow zone… As Greenland crosses the threshold and starts really melting in the upper elevations, it really won’t recover from that unless the climate cools significantly for an extended period of time, which doesn’t seem very likely.”

Next post: Dangerous impacts from the current implied temperature rise

Link: http://www.climatecodered.org/2013/09/is-climate-change-already-dangerous-2_19.html

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