WUWT readers surely remember all the media hype over this story. This was REP’s last entry on WUWT:
As WUWT readers are aware, there has been a great deal of attention paid by the main stream media to the extensive melt on the Greenland icecap that occurred during July (for example, see here, here, here, here, and here). The topic was addressed here at WUWT in two postings here and here. Anthony noted in the later posting that Andrew Revkin was almost alone in taking a more nuanced and skeptical view of the unprecedented nature of the event and has taken a fair amount of heat in comments for his effort.
And then there was the paper that showed that a shift in the jet stream caused warmer than normal temperatures in July 2012. Now a new paper in PNAS nails the trigger for the “insta-melt”, finding carbon soot combined with warmer temperatures was the trigger, not just in 2012, but also in 1889.
They get one attribution wrong, confusing climate change and weather events, but the science on the black carbon (BC) and albedo seems right. Their use of Oxygen 18 isotope records show that it was unusually warm in 1889 as well. They say in the Figure 2 caption:
…widespread melt events only occurred in 1889 and 2012. In C and E, melt occurred because of the deposition of high concentrations of BC and ammonium, indicating an albedo reduction due to BC from summer forest fires.
Visual evidence of carbon soot can be found in meltwater ponds in Greenland from this and other photos by James Balog, a real eye opener:
Image from National Geographic online slide show – Photo: James Balog – click for more
He writes:
In the winter a huge among of snow are accumulated on the Ice (2-3 meters, sometimes more) and we are not talking about 1 or 2 square-miles, it’s about 100.000′s of square miles (up to 1 million) on the Westside of the Ice cap and a similar picture on the Eastside… when the melting season starts in april-sep… the meltwater has to go somewhere, and for sure it goes downhill in huge meltwater rivers.
The black stuff on the bottom of the lakes is carbon dust and pollution in general… but not from one year, but several decades (the topographical conditions don’t change from year to year). On a flight over the Ice Cap a sky clear day, you can see hundreds of huge lakes with the black spot on the bottom.
The paper: http://www.pnas.org/content/111/22/7964.figures-only
Climate change and forest fires synergistically drive widespread melt events of the Greenland Ice Sheet
Significance:
Through an examination of shallow ice cores covering a wide area of the Greenland Ice Sheet (GIS), we show that the same mechanism drove two widespread melt events that occurred over 100 years apart, in 1889 and 2012. We found that black carbon from forest fires and rising temperatures combined to cause both of these events, and that continued climate change may result in nearly annual melting of the surface of the GIS by the year 2100. In addition, a positive feedback mechanism may be set in motion whereby melt water is retained as refrozen ice layers within the snow pack, causing lower albedo and leaving the ice sheet surface even more susceptible to future melting.
Abstract
In July 2012, over 97% of the Greenland Ice Sheet experienced surface melt, the first widespread melt during the era of satellite remote sensing. Analysis of six Greenland shallow firn cores from the dry snow region confirms that the most recent prior widespread melt occurred in 1889. A firn core from the center of the ice sheet demonstrated that exceptionally warm temperatures combined with black carbon sediments from Northern Hemisphere forest fires reduced albedo below a critical threshold in the dry snow region, and caused the melting events in both 1889 and 2012. We use these data to project the frequency of widespread melt into the year 2100. Since Arctic temperatures and the frequency of forest fires are both expected to rise with climate change, our results suggest that widespread melt events on the Greenland Ice Sheet may begin to occur almost annually by the end of century. These events are likely to alter the surface mass balance of the ice sheet, leaving the surface susceptible to further melting.
Fig. 1.
Melt extent over the GIS determined from Oceansat-2 satellite scatterometer, Special Sensor Microwave Imager/Sounder, and Moderate-resolution Imaging Spectroradiometer satellite data for (A) July 8, 2012, and (B) July 12, 2012. Red areas indicate melt detected by the satellites, white areas indicate no melt, and blue represents ocean. The surface of almost the entire ice sheet, including the dry snow region, experienced melt on July 12, 2012. Figure courtesy of Dorothy Hall, NASA Goddard Space Flight Center.
Fig. 2.
(Lower) The annual average BC concentrations (ng g−1) from 1750 to 2010 of the Summit-2010 firn core and the 2012 surface section. (Upper) Sections of the BC record along with δ18O and ammonium records, plotted on a relative scale normalized to the maximum and minimum values in each record, for the time intervals (A) 1783–1788, (B) 1865–1870, (C) 1887–1892, and (D) 1905–1910, as well as (E) the normalized average value of BC and ammonium concentrations from the July 2012 surface sample, and approximate δ18O. These time intervals demonstrate extreme scenarios in the center of the GIS with (B−E) depicting the highest concentrations of BC, and (A) the warmest temperature since 1750, but widespread melt events only occurred in 1889 and 2012. In C and E, melt occurred because of the deposition of high concentrations of BC and ammonium, indicating an albedo reduction due to BC from summer forest fires. Importantly, these deposition events occurred during warm summers. In B, a high concentration of BC and presence of ammonium during a cooler summer suggest that the surface was below the energy threshold for melt. In D, the highest concentrations of BC and ammonium in the record were recorded during an average summer, suggesting that the BC was deposited at a time of the year when the available surface energy was well below the threshold for melt. The warmest temperature recorded in the core occurred in 1785, but widespread melting did not occur due to low BC concentration.
The summer of 2012 saw huge forest fires in Labrador, according to this article from December 2012: http://www.theguardian.com/environment/2012/dec/07/greenland-ice-melting-arctic-wildfires
Lots of stuff here: http://darksnowproject.org
I live in Massachusetts. We have two pellet stoves that generate many pounds of ash. Instead of shoveling the back walkway so the oil and propane people can get to their filling areas, I take the ash and sprinkle it on the snow. The sun does the rest regardless of ambient temperatures. Then the spring showers wash the ash from the walkway.
But isnt’ the effect only good til the next snow?
Joe G.,
Great idea. You should start a project with a name like “Solar Driveways” and start applying for DOT grants to refine your technology. Emphasize how you’re recycling carbon in your process. Could be very lucrative.
Nonsense. Forest fires were far worse than they are today. In the early 1900’s, Oregon was ablaze with them. And that was just one state. Multiply Oregon by exponential multipliers to get an idea of past forest fire conditions. It doesn’t take much more than a thought experiment to readily hypothesize that under current conditions regarding widespread forest fire suppression, the incident of black soot related to forest fires has gone down in the presence of long term warming.
Pamela, see my links, there were relatively nearby (on Labrador) huge forest fires in 2012!
Anthony, I agree that black carbon reduces reflectivity, and enhances warming of glaciers such as those in Greenland. And I’ve seen collections of black solid matter in melt ponds of various sizes in glaciers in Alaska. Much of the dark solid matter in these melt ponds is wind blown dust, which darkens when wet. I’ve seen tiny little melt ponds a couple of inches across, less than an inch deep, with just a few dust particles in them, visibly tiny particles. That was enough to cause localized melt, at above freezing summer temperatures. The black carbon, though, is usually in tiny size fractions, called “PM2,5,” for particles which are 2.5 micrometers or smaller in diameter. You might not actually see much of the black carbon because it is so tiny, about 1/30th of the width of a human hair, but it will nevertheless cause the surface of the glacier to be imperceptibly darker, and thus warmer. When you get to the larger melt ponds, and deeper places in rivers on the glacial surface, such as pictured above, I agree with the author that it is probably a mixture of wind blown dust and black carbon.
DayHay, It all depends on how much snow accumulates on top of the soot and how soon that next snow comes. My pellet stoves are making ash every day during the winter so I have plenty to spare for recovering fresh snow. I usually only spread the soot 4 times a season. It beats shoveling.
Only two comments. One is: Is anybody going to go back to the media and have them (as) loudly proclaim “Never mind…” (h/t to Saturday Night Live, circa late 1970s) as they initially proclaimed that this was the “unprecedented” beginning of the end for the Greenland Ice Sheet? I didn’t think so. That would require actual honesty, sort of like not attributing the cause of the observed (tiny!) melt in the first place until people had time to figure it out.
The second question is: What was the cause of the soot deposit in 1889? Do we know of any large near-polar fires that might have carried soot onto Greenland? Did the jet stream shift and carry coal soot from industrial Europe west? Is there a corresponding coherent soot event in the Iceland glaciers? How about the Alaskan glaciers. OK, so that is more than one question, but enquiring minds like to know…
A comment. Did anyone else notice the throwaway line of the entire abstract?
What the heck? This was way, way back just after the end of the Little Ice Age. Anthropogenic CO_2 was all but non-existent! Again, is there evidence that this warmest temperature event was coherent in similar icelandic glaciers, in Alpine glaciers, in Himalayan glaciers, in Alaskan glaciers, in Antarctic ice pack? What about the known (but nearly unremarked upon) great melt of the Arctic sea ice in the early 1930s, reported in the news but not scientifically or systematically documented in a world essentially without airplanes and where nobody went into the dangerous arctic ice even in steel ships unless they were prepared for a disaster of Titanic proportions…?
rgb
More evidence of soot in the Arctic lowering albedo.
Imagine that! We will no longer need to pay for snow and ice removal anywhere in the US because of the particulate matter spewed from our trucks and fireplaces!!….or does this phenomena only occur in Greenland? If I have a cup of coffee and the next day all that is left is sediment from coffee beans and sugar…did the beans and sugar dehydrate it.
Somehow the snow samplers continue to ignore concentrations. Just because you observe a flake of terra preta at the bottom of a pool of melt, do not conclude it is not anywhere else in the snow/ice.
On side note: if anyone caught the interview with the guy taking ice samples who fell down a crevasse and then called it an abandoned mine….
What gets me is this sentence; “We use these data to project the frequency of widespread melt into the year 2100.”
These “data” being two events 115 years apart. Clever.
rgbatduke says:
June 6, 2014 at 7:57 am
When the surface melt was in the news, a journalist & novelist buddy of mine predicted that the Greenland ice sheet would be gone by 2016.
This report on the paper cites Pacific NW forest fires that year, while also predicting more fires from “global warming”, thus threatening the ice sheet:
http://phys.org/news/2014-05-climate-forest-drove-widespread-surface.html
Both Seattle & Spokane burned in 1889, but nothing occurred on the scale of other forest fires in this region. Maybe it was a WX pattern that carried not much above normal soot toward Greenland.
Climate change and forest fires synergistically drive widespread melt events of the Greenland Ice Sheet
Rubbish!
http://www.meltfactor.org/blog/?p=1240
See second photograph.
… boots on the ice offer a close look (and to sample) impurities concentrating at the surface. The fact is, much of this dark material is from cyanobacteria and blue-green algae. Photo J. Box.
Carbon taking a bad rap – again!
Could volcanic ash be the primary component of the black stuff in the bottom of the melt ponds?
Pamel Gray has put her finger on the nub of the problem.
Carbon soot, from natural sources, has always been present in the atmosphere in appreciable quantities. Nothing is different today except that some natural sources (such as U.S. forests) now make less contribution.
You don’t really need tons of soot in the case of large ice/snow areas like Greenland.
The fresh snow surface is highly scattering (refractive0 rather than reflective, which gives it an apparent reflectance in the 80% range. For comparison, the highest polished fresh aluminum surface is only about 80% – 90 % reflectance.
But once you get some localized surface melting from just a little bit of BC or other dust, the liquid water surface is only 2% reflectance at normal incidence, and perhaps 3% for total spherical reflectance (of a diffuse source).
So once those puddles form, they are an efficient conduit for solar radiant energy, down into the snow.
And it’s a two edged sword. The carbon soot or other dust in the atmosphere, makes a perfect substrate for formation of water droplets; AKA “rain”, which in one swell foop, deposits out the soot to clear the air for solar transmission, and then warming of the melt ponds.
It would not surprise me, if this forest fire sooty behavior is every bit as well unknown, as is the effect of clouds, on total solid / liquid surface solar insolation. That’s just a WAG. I have no special knowledge, that this is so; but then, neither do they. And we know who they are.
From – GEOPHYSICAL RESEARCH LETTERS, VOL. 22, NO.2, PAGES 89-92, JANUARY 15, 1995
Biomass burning record and black carbon in the GISP2 ice core
The average black carbon concentration during the 320 to 330 A.D. decade is found to be 2.1
micro g of black carbon per kg of snow melt water. The current snow (1989 and 1990) from the GISP2 site shows an average black carbon concentration of about 2.0 micro g/kg suggesting that the rate of black carbon deposition at the GISP2 Greenland site during 1989-1990 was about the
same as 1670 years ago.
http://w3.pppl.gov/~pdamiano/publications/Chylek_et_alGRL1994.pdf
Please note the concentrations these guys are talking about. Micro G/Kg or G/1,000,000 Kg of snow melt water. How many gram of soot is there in the picture?
Please also remember earlier studies of soot levels, where the highest values are from the late 1800’s.
In 2007, Joe McConnell, a hydrologist at the Desert Research Institute in Reno, Nevada, had measured black carbon levels in ice cores pulled from west central Greenland that dated back to 1788. Between 1850 and 1910, black carbon concentrations grew seven-fold and then fell, charting the path of coal burning during early industrialization. Major wildfires also showed up on the record as peaks of vanillic acid, which is produced when lignin from conifer trees is burned.
http://www.pbs.org/wgbh/nova/next/earth/greenland-and-wildfires/
We are dealing with ppm levels that make CO2 seem gigantic.
I do believe we were still in the Little Ice Age in 1785. The last frost fair on the River Thames was in 1814. An elephant was led over the ice near Blackfriars Bridge apparently. You now need to think about the effect of soot throughout the Arctic. It really does make me wonder.
Well, that was my impression too, although we were out of the peak of it by then IIRC and starting to warm (until factors that may or may not have included Tambora caused the Dalton minimum “relapse”). But as Anthony might say, Watt’s Up With That? A highest temperature observed by proxy in the Greenland ice cores in the heart of the Little Ice Age?
I can’t tell whether to weep or laugh. Does this mean that the proxies being used are utterly meaningless for estimating past temperature (due to some sort of confounding effect) or does it mean that Greenland really did spike way up in temperature to the warmest in over 200 years while most of the world was in the grip of the coldest stretch in the entire Holocene, a near-return to glacial conditions?
Hence my interest in whether or not this was in any sense a coherent event. Was it “Just Greenland”? Did Iceland have a heat wave too? Is there any corroboratory evidence that there was a localized temperature spike during an era when (as you say) elephants were dancing on the frozen Thames? As it stands (alone), Bayesian reasoning makes me want to doubt the entire result, and hence the entire method they are using, lacking some fairly solid evidence that their method is calibrated to non-confounded “reality”. It’s sort of like finding evidence that Cro-Magnon tribes opened up an exotic beach resort on the shores of Norway in the year 25,000 BCE. Yeah, maybe, sure, but — no. No, I can’t believe that. Most of Norway was covered by a big block of ice at the time (like all of northern North America) it it’s hard to hang out on the beach sunbathing in the nude when the “beach” is a kilometer or so beneath you with nothing but 20,000 year old ice in between you and it. A heat wave in Greenland in the late 18th century seems just about as likely.
It’s worse than we thought.
The Great Hinkley Fire of September 1894 burned 300,000 acres of pine forest in rural MN.
But of course today’s fires are much more severe/sarc off
Joe G says:
June 6, 2014 at 6:34 am
I live in Massachusetts. We have two pellet stoves that generate many pounds of ash. Instead of shoveling the back walkway so the oil and propane people can get to their filling areas, I take the ash and sprinkle it on the snow. The sun does the rest regardless of ambient temperatures. Then the spring showers wash the ash from the walkway.
_________________________
Have you noticed any effect on the lawn/flora next to the walkway?
In addition, a positive feedback mechanism may be set in motion whereby melt water is retained as refrozen ice layers within the snow pack, causing lower albedo and leaving the ice sheet surface even more susceptible to future melting.
There is a second +ve fedback, as BC/dust becomes concentrated on the surface reducing albedo.
This, IMO, is the primary mechanism causing the rapid transition from glacial phases to inter-glacials.
I’ll note the irony off efforts to reduce carbon emissions and forest fires risking triggering the next glaciation.
Rgbatduke
Several answers to your questions.
The lia was characterised by both extremely cold and extremely warm weather. This juxtaposition of the two states is well documented. I wrote of changing climate through the centuries here, and there are many references to heat during the 18th and 19th centuries
http://wattsupwiththat.com/2011/11/01/a-short-anthology-of-changing-climate/
As regards soot, when researching for my article on the arctic melting circa 1820 I came across scientific papers from that era which commented on the high levels of soot and how it melted the ice. The blame was put on the growth of American industry and prevailing winds carrying this carbon onto the arctic. A few weeks ago the BBC showed an interesting documentary on the arctic and I commented here at the time as to the astonishing amount of soot that could be seen in virtually every picture including the meltwater lakes far under the surface.
So, yes, it is quite likely there was extreme heat in Greenland in 1785 . There was also extreme heat in the 1930’s and 1940’s which caused Phil jones to remark that this was the warmest two consecutive decades in the record. We will not know until 2020 if the previous two decades will beat this.
Soot is in my opinion a likely factor in arctic melt and I am surprised there has not been more research on the subject. To Joe G I would say that during the freezing winter of 1962/3 it was my task before school to take the ash from our coal fires and spread it on the paths which, as he has discovered, is a great way of melting ice..
Nature appears to be doing this on a grand scale in the arctic with the help of man made soot and that from first fires, yet we seem to want to refuse to see it or to realise that the arctic periodically has very high temperatures
Tonyb
Tonyb says:
June 6, 2014 at 1:56 pm
I repeat my post from above:
Climate change and forest fires synergistically drive widespread melt events of the Greenland Ice Sheet
Rubbish!
http://www.meltfactor.org/blog/?p=1240
See second photograph.
… boots on the ice offer a close look (and to sample) impurities concentrating at the surface. The fact is, much of this dark material is from cyanobacteria and blue-green algae. Photo J. Box.
Billy Liar – thanks! I was going to ask . . . did anyone actually sample and test this stuff? Or did they see the dark stuff at the bottom of the pool and assume they knew what it is?
Of course the Iceland volcanic eruptions could account for some melting. If the ice is covered with dust from the volcano it will not reflect the sunlight as well. This happened in the Austrian and Italian Alps in 1991, and that is how they found ‘Ortzi’ the mummified ice man. Anyway it will freeze up again soon.
Hi Pamela
I wouldn’t attribute the recent mega fires to climate change but to poor forest management ie smokey the bear. Burning off has not been carried out during the cool seasons in a sustainable way to reduce the fuel load your forests. So these mega fires are essentially caused by fuel loads building up in the forests fueling these massive mega fires. Australia has the same issue. Prior to European settlement in Oz the aboriginal people employed fire stick technology to keep fuel loads low in the eucalypt forests and to promote the growth of edible grass instead of woody species to feed their prey animals. Unfortunately the greenies in Oz are promoting this myth that if you don’t carry out fuel reduction burns the unburnt forests are suppose to become more fire retardant.
As far as I know, nothing out of the ordinary (never mind “unprecedented”) happened in Greenland in July 2012. The ice cap is still very much there. At most, surface melting was more extensive than usual, as it must be sometimes.
billy liar
Bit confused about your reference to me as I never said those words.
Many things contribute to arctic soot, man made and natural. Man made soot is fairly low hanging fruit that can be dealt with if it can be demonstrated it is a significant contributory factor to arctic ice melt. I don’t think its been proven yet but it strikes me as being worthy of research.
tonyb
Here are a few soot studies. See the first study from Hansen as well as the year. Then look at the last reference for CFCs, also from Hansen as well as the date. What he is saying is that most of the warming up to 2000 was driven by soot and CFCs!
—
Billy Liar’s blog reference says
How much is much? We know soot is up there in Greenland and much of the Arctic. Measurements of BC have been made dated back to over 3,000 years.
Nature – 28 May 2014
“Soot drives Greenland melting”
http://www.nature.com/nature/journal/v509/n7502/full/509537c.html
Even SkS has seen some light on this sooty issue.
http://www.skepticalscience.com/print.php?n=1804
In Oz we have some native trees that need fire to germinate seeds. Now botanists know that for a tree to evolve and adapt to this, requires millions of years to adjust. In the New England National parks rainforest patches, the Antarctic beech is dominant over eucalyps, and instead of being a deciduous tree as it is in other regions, it is like the gum trees, shedding leaves around the year. Trees do adapt to climate, but of course any Australian imported trees, like Oaks or wattles are not fire resistant etc., as are all deciduous trees. Gum trees of course like pines have oils in their leaves and needles and they burn very well. Too Well in bush fire regions. Pamela is correct, wild fires are not new, they occur from lightening strikes, and well before humans roamed these great forests. Unfortunately in Australia some human arsonists take great delight starting fires to destroy the bush, and any living thing that can’t escape.
When Keegan’s images are placed next to Greenland topography e.g. http://www.livescience.com/39298-under-the-greenland-ice-sheet.html, they still make no sense to me – soot or not.
Hi bushbunny
For anyone who wants to read a good reference on the subject I would recommend “The Biggest Estate on Earth How Aboriginals Made Australia” by Bill Gammage. It is well research book with 87 pages of reference notes if you want to go to the source documents.