Through the Ice, Darkly

Guest Post by Willis Eschenbach

As always, I get distracted by the daily news. The weather news today is a lovely rainy morning here in drought-plagued California, we got just under an inch (2cm) in last night’s storm, and the outer world is green and happy. Regarding the climate news, Anthony highlighted a claimed recent darkening of the Greenland ice cap.  This is said to be reducing the ice cap’s albedo, which is the percentage of sunshine reflected back to space, and thus leading to more solar absorption and more melting.

Being an inherently suspectful type oif fellow, I thought I’d take a look at the albedo and other anatomical features of Greenland. First, the big view. Let me start with a map showing the global “all-sky” albedo from the CERES satellite data. It shows the average of all satellite observations, both when the sky is clear and when it is cloudy.

greenland all sky average albedoFigure 1. All-sky average albedo, CERES top-of-atmosphere data Mar 2000 – Feb 2015. 

Overall, the combination of the clouds and the surface reflect just under a third of all the sunlight that hits the planet. In general the albedo is smallest in the tropics and increases towards both poles. In Figure 1, you can see the inter-tropical convergence zone just above the equator. You can also see Greenland, bright red up near the north pole, with an average albedo of about 65%

The CERES data provides us with another view of the albedo, which is just the measurements taken when the sky is clear. Figure 2 shows that clear-sky albedo, the solar reflection from the surface when there are no clouds..

greenland clear sky average albedoFigure 2. Clear-sky average albedo, CERES top-of-atmosphere data Mar 2000 – Feb 2015. 

As you can see, without the clouds there is much less sunlight reflected from the surface. For example, the ocean reflects less than 10% of the incident sunlight … but even without clouds, Greenland still has an albedo of about 65% because like Antarctica, it has a permanent ice cap. It is the darkening of this Greenland ice cap that I set out to investigate.

Now, there’s a problem with measuring albedo near the poles. Albedo is a ratio. It is a fraction with reflected solar energy on the top and the incoming sunshine on the bottom. Most of Greenland is above the Arctic Circle. So when the sun gets to very near zero in the winter, the albedo gets very uncertain and averages get distorted. As a result, I look instead at the total amount of sunshine that is reflected from Greenland. The incoming sun is constant on an annual basis, so any change in the albedo will be reflected as a change in the total amount of sunshine reflected.

Figure 3 below shows the month-by-month changes in the all-sky reflections from Greenland. I masked out the ocean, so Figure 3 represents solar reflections of just the area of the island itself.

greenland toa reflected solar all skyFigure 3. All-sky average reflected solar energy, CERES top-of-atmosphere data. Units are watts per metre squared (W/m2). Mean value is 119.8 W/m2. Top panel shows raw data. Middle panel shows the average seasonal variation in the data. Bottom panel shows the residuals, which are the raw data minus the seasonal component. Standard deviation of the residuals is indicated by the horizontal gold dashed lines.

The average amount of energy reflected by the clouds plus the surface is about 120 W/m2. There is no trend visible over the period, and the standard deviation of the residuals (bottom panel) is only about ± 2.5 W/m2.

“Ah”, I hear you thinking, “but that includes the clouds”. Indeed it does, it is not the surface albedo from the ice cap. I like to look at what is happening overall before I look at the specifics. Having seen that there is no overall albedo trend in Greenland, Figure 4 shows the Greenaland surface reflections when the sky is clear.

greenland toa reflected solar clear skyFigure 4. Clear-sky average reflected solar energy, CERES top-of-atmosphere data. Units are watts per metre squared (W/m2). Mean value is 115.9 W/m2. Top panel shows raw data. Middle panel shows the average seasonal variation in the data. Bottom panel shows the residuals, which are the raw data minus the seasonal component. Standard deviation of the residuals is indicated by the horizontal gold dashed lines.

I note first that the surface average reflection is about 116 W/m2, only slightly smaller than the 120 W/m2 we saw in the all-sky data in Figure 3. This shows that the albedo of the surface and the albedo of the clouds are quite similar, with the clouds reflecting slightly more than the ice cap

And just like with the all-sky data, there is no trend in the surface data either. There is no indication at all of the claimed darkening of the surface.

Finally, I was interested in what to me was the most curious feature of Figure 4. This is the large dip in surface reflection in the summer of 2012 that reaches a minimum in July. I seemed to remember some oddity that year, and a bit of searching found this from the National Snow and Ice Data Center:

An intense Greenland melt season: 2012 in review

February 5, 2013

Greenland’s surface melting in 2012 was intense, far in excess of any earlier year in the satellite record since 1979. In July 2012, a very unusual weather event occurred. For a few days, 97% of the entire ice sheet indicated surface melting. 

Now, we know from Figure 2 that water has a much lower albedo than ice. So we can see that meltwater on the icecap reduced the reflection of sunlight, and led to the 2012 summer drop in reflected solar energy shown in the CERES data.

The appearance of this July 2012 event in the CERES data supports the validity of the data, and also shows that the data should be more than precise enough to show any trend in the solar reflection over the fifteen-year period of the record … and despite that, there is no such trend visible.

Go figure … I don’t know why the original researchers are claiming a darkening of Greenland, but I’m unable to find it in the CERES data.


My Usual Request: If you disagree with me or anyone, please quote the exact words you disagree with. I can defend my own words. I cannot defend someone else’s interpretation of some unidentified words of mine.

My Other Request: If you think that e.g. I’m using the wrong method on the wrong dataset, please educate me and others by demonstrating the proper use of the right method on the right dataset. Simply claiming I’m wrong doesn’t advance the discussion.

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March 3, 2016 4:01 pm

[snip – wildly off topic from a known troll – Anthony]

Gunga Din
Reply to  Willis Eschenbach
March 3, 2016 4:24 pm

“The world wonders …”
Halsey was set off in the wrong direction by such nonsense… 😎

Reply to
March 3, 2016 4:18 pm

So, oldnwise – any comments on your link? Since you posted it twice, you must agree with the source. And this relates to albedo ….. how?

FJ Shepherd
Reply to
March 3, 2016 4:34 pm

OH my, that link is so frightening: “Global warming is going into overdrive.” Isn’t it amazing how much more powerful mother nature is with her El Nino that can do that? I hope you noticed that,

Reply to  FJ Shepherd
March 3, 2016 5:32 pm

1oldnwise4me is a nut case, based on some of his recent posts.

March 3, 2016 4:12 pm

“Go figure … I don’t know why the original researchers are claiming a darkening of Greenland, but I’m unable to find it in the CERES data.”
They looked at the period 1981-2012. It looks like a downtrend in your plot up to 2012, and there’s almost twice as long you haven’t looked at.
“So we can see that meltwater on the icecap reduced the reflection of sunlight, and led to the 2012 summer drop in reflected solar energy shown in the CERES data.”
Yes. Wet ice is part of their feedback mechanism.

Reply to  Nick Stokes
March 3, 2016 4:27 pm

Yes, there is a clear drop from 2000-2003 in Willis’ graphs. About 4 W/m^2 by eye.
Pretty flat since but may well have also changed leading up to y2k. However, not much evidence of Greenland getting “locked into a feedback loop” as suggested by the paper.
That is the old “tipping point” argument again. Recovery after the sharp dip in 2012 is not in any way consistent with that claim.
Good work Willis.

Reply to  Greg
March 4, 2016 2:15 am

Actually this is just standard Climate Science® practice – start at an outlier year in one direction and end at an outlier year in the other direction and you can get a nice trend of your choice.
They were lucky they had 2012 available though. Large melt events only occur about once a century (the previous one was in 1888). During the previous (warmer) interglacial they came about once per decade.

Reply to  Willis Eschenbach
March 3, 2016 4:49 pm

I’d give Nick the benefit of the doubt, Willis. He’s knowledgeable & unflappable. That said, he does appear to have an agenda at times…

Reply to  Willis Eschenbach
March 3, 2016 5:17 pm

“you are just making stuff up”
Not made up. The time intervals are different. But below I’ve aligned the albedo plot from their Fig 1 with your Fig 4, scaled. Their grey is the MAR result, black is GLASS. The main features are similar, especially for MAR. Theirs has less detail, being annual. But there is the steep dip in 2012, peak about 2006 and high values around 2000. As for trend, you probably should add an actual 2000-2012 trend line.

Reply to  Willis Eschenbach
March 3, 2016 5:32 pm

Thanks Nick, I think you’ve put your finger on it. I was curious about their data stopping in 2012 in a 2016 paper. See how easy it is to fool the eye of the reader.
They generate the impression of runaway melting : a tipping point by stopping the data at the bottom of the 2012 spike. Their paper fails to see the rebound the following year.
It’s like plotting Arctic sea ice area and stopping in the OMG 2012 minimum and not reporting the massive increase in ice volume that followed.
Anyway, don’t forget : “More than half of the Greenland ice sheet melted last summer”

Reply to  Willis Eschenbach
March 3, 2016 6:36 pm

Their paper was “Received: 6 September 2015“. I find it very suspicious indeed that the paper’s study period ended in mid-2012, at exactly the moment that albedo hit a minimum before rapidly and completely rebounding. Given the date of the paper, how is this not a blatant and fraudulent cherry-pick?

Reply to  Willis Eschenbach
March 3, 2016 9:10 pm

“the problem being that I hadn’t looked at a long enough record”
I simply pointed out that the record they analysed was quite different to yours. That is true, and was a relevant observation. You didn’t mention anywhere in your post what period they were analysing. It matters.

John in Oz
Reply to  Willis Eschenbach
March 3, 2016 11:07 pm

Willis appears to be plotting the full year data but the plot being discussed is only J(une), J(uly), A(ugust).
Isn’t this apples vs oranges?

Reply to  Willis Eschenbach
March 3, 2016 11:39 pm

“Isn’t this apples vs oranges”
Willis is plotting total solar reflection. As his plots show, that mostly happens in summertime, so summer albedo is about right.
OTOH, it shows a reason why his plot looks different to the paper, and with flattish trend. Willis is plottig monthly, and the winter months are bound to be at zero. So you see a succession of spikes, with these flat bits in between. The plot from the paper is annual.

Paul Mackey
Reply to  Willis Eschenbach
March 4, 2016 1:32 am

I would be interested to get an idea of the error bars on the anomoly data. It seems a small difference compared to the absolute magnitude.

Reply to  Willis Eschenbach
March 4, 2016 3:15 am

The surface energy balance and meltwater production of the Greenland ice sheet
(GrIS) are modulated by snow and ice albedo through the amount of absorbed solar
radiation. Here we show, using spaceborne multispectral data collected during the
three decades from 1981 to 2012, that summertime surface albedo over the GrIS
decreased at a statistically significant (99 %) rate of 0.02 decade−1
between 1996 and 2012. The negative trend is confined to the regions of the GrIS that undergo
melting in summer with the dry-snow zone showing no trend. The period 1981–1996
showed no statistically significant trend. The analysis of the outputs of a regional
climate model indicates that the drivers of the observed albedo decrease is imputable
to a combination of increased near-surface temperatures, which enhanced melt and
promoted growth in snow grain size and the expansion of bare ice areas, as well
as by trends in light-absorbing impurities on the snow and ice surfaces. Neither
aerosol models nor in situ observations indicate increasing trends in impurities in the atmosphere over Greenland, suggesting that their apparent increase in snow and ice
might be related to the exposure of a “dark band” of dirty ice and to the consolidation
of impurities at the surface with melt. Albedo projections through the end of the
century under different warming scenarios consistently point to continued darkening,
with albedo anomalies in 2100 averaged over the whole ice sheet lower than in 2000
by 0.08, driven solely by a warming climate. Future darkening is likely underestimated
because of known underestimates in projected melting and because the model albedo
scheme does not currently include light-absorbing impurities and the effect of biological
activity, which themselves have a positive feedback, leading to increased melting, grain
growth and darkening.”
Let me repeat:
“Albedo projections through the end of the
century under different warming scenarios consistently point to continued darkening,
with albedo anomalies in 2100 averaged over the whole ice sheet lower than in 2000
by 0.08, driven solely by a warming climate. ”
This is clearly cherrypicking, making trends and projections based on —what?
So: M. Tedesco, S. Doherty, X. Fettweis, P. Alexander, J. Jeyaratnam, E. Noble and J. Stroeve:
Is this science or is it mission impossible?

Reply to  Willis Eschenbach
March 4, 2016 9:17 am

Mike Jonas March 3, 2016 at 6:36 pm
Their paper was “Received: 6 September 2015“. I find it very suspicious indeed that the paper’s study period ended in mid-2012, at exactly the moment that albedo hit a minimum before rapidly and completely rebounding. Given the date of the paper, how is this not a blatant and fraudulent cherry-pick?

As far as I can tell the GLASS data ends in 2012 so it would not be possible to continue further.

Reply to  Willis Eschenbach
March 4, 2016 10:53 am

Phil. Thx. Is there any way of checking that?

bit chilly
Reply to  Willis Eschenbach
March 4, 2016 4:23 pm

nick stokes, being one of the most respectful and knowledgeable people posting on climate blogs today i cannot believe what you just posted in reply to willis. my gob is smacked.

Reply to  Willis Eschenbach
March 4, 2016 6:21 pm

Mike Jonas March 4, 2016 at 10:53 am
Phil. Thx. Is there any way of checking that?

I found the ftp link here and the last Modis file there is dated 2012.

george e. smith
Reply to  Nick Stokes
March 3, 2016 4:33 pm

I am under the impression that ” albedo ” is the solar energy reflectance of planet earth, that is the percentage of total incident solar energy reflected back out into space still as solar spectrum energy.
So I don’t see how Antarctica can be reflecting 72% of 342 W.m^2 back into space. I don’t think it even receives that much energy from the sun.
If they are confusing albedo with reflection coefficient, they should say so.
There is a very basic reason why there is all of that ice there in Antarctica with its high reflection coefficient (which might be 72% for fresh snow).
That reason is that very little solar energy is incident there. It would be even colder there in Antarctica and also in the Arctic, if it wasn’t for the astronomical amounts of heat energy that is convected from the tropics to the polar regions, by warm ocean currents, and atmospheric currents.
Their phony color map of painting the polar regions red, gives the impression that lots of energy is being reflected from the poles. It isn’t.
Albedo should be (and is in my view) a SINGLE number for the entire planet; it isn’t regional. Reflection coefficient can be regional.

Don K
Reply to  george e. smith
March 3, 2016 11:52 pm

“Perhaps it should be, but it isn’t a single number. Here’s a typical list:”
1. Water seems to be missing from the list. But between oceans and lakes isn’t water by far the dominant surface material on Earth?
2. What causes the dramatic peaks in the residuals in the Summer(?) of 2000, 2001, etc? It’s probably obvious if one is smart. But I’m not.
3. Surely sun elevation angle is a major variable, especially with water, but probably with ice, snow and even other materials. You do address the case of angles near zero (sort of), but it’s unclear to me exactly how sun elevation gets handled.
4. I’m a bit hazy on the geometry of this thing. Are you/we/they plotting the location of the satellite or the location of the reflection point? I think the latter is directly under the satellites only near the equator? And it’s location varies with the elevation of the reflection? Is the difference between the positions significant? It would seem to me that when the sun is low in the sky, it might be quite a ways, but I could be visualizing entirely the wrong thing.
I see that Clyde Spencer has addressed some of my concerns below. Regretably, he seems to have even more questions than I do.
And as always, thanks for taking all this on.

Reply to  george e. smith
March 4, 2016 12:39 am

I kinda hate the term ‘albedo’. Reason is that it doesn’t actually say much, or perhaps it is so general that to me it becomes meaningless or in fact aggravating. I am currently doing some private research involving integrating spheres.
My research to date has shown that there is a lot of confusion regarding terms ie. albedo, reflectance, reflectivity. All of these are actually different in the specifics. Reflectivity is like a mirror. Albedo takes a look at the entire spectrum (it should) and determines the light bouncing off. Reflectance is about the wavelengths that are absorbed/reflected.
What am I really saying?
Be careful about what you are looking at.
Never forget the cosine rule.
Take atmospheric thickness into account.
The above three things are involved in the ‘product’ you use for calculations. Algorithms all the way down.
Accuracy of algorithms is up in the air as far as I’m concerned.
They have a certain usefulness.
As NASA says useful for remote sensing but not accurate for qualitative work.
Keep up your good work

Reply to  george e. smith
March 4, 2016 2:23 am

“Water seems to be missing from the list. But between oceans and lakes isn’t water by far the dominant surface material on Earth?”
Yes, but it is difficult to put a single number to water albedo. The amount of suspended particles (largely plankton, but also sediment) affects the albedo, and at low sun-angels specular reflection is also a significant factor. However the albedo of oceans is low – on the order of 0.1 – so the vast majority of heat is absorbed by the oceans.

Don K
Reply to  george e. smith
March 4, 2016 4:57 am

tty: “and at low sun-angels specular reflection is also a significant factor. However the albedo of oceans is low – on the order of 0.1 – so the vast majority of heat is absorbed by the oceans.”
Near the equator, that’s probably true. But we’re dealing with far Northern latitudes here where the sun elevation angle is always pretty low assuming that the sun is even visible. The lower the elevation angle, the higher the reflection. You can test that by walking toward any nearby body of water whose surface isn’t rippled. A rainwater pond will do just fine. From a distance what you see is a reflection of whatever is beyond the water. You have to get pretty close before the bottom under the water becomes visible.

Reply to  Nick Stokes
March 3, 2016 4:36 pm

You mean a downtrend between 2000 and 2002? Or are you looking at the minimum in July 2012? Was CERES around in 1981?

Reply to  Nick Stokes
March 3, 2016 6:47 pm

Nick Stokes: They looked at the period 1981-2012. It looks like a downtrend in your plot up to 2012, and there’s almost twice as long you haven’t looked at.
The record before 2000 is pretty flat, and the record since 2012 shows a rebound to what might be called nearly “average”. Why submit a paper in Sept 2015 with data truncated at an observed minimum in 2012? We must look forward to their update to learn why, perhaps.

Reply to  matthewrmarler
March 3, 2016 7:50 pm

Don’t hold your breath while waiting for that update!

Reply to  matthewrmarler
March 6, 2016 12:11 am

As Phil. noted elsewhere, the MODIS data finished in 2012. The GLASS project was described in this 2013 paper. They published there results, and AFAIK, there was no ongoing updating.

Reply to  Nick Stokes
March 4, 2016 2:00 am

An albedo figure for all of Greenland is not going to show a reducing trend. As the paper demonstrates, the albedo of the highlands is static or increasing, and the reductions are only on the margins and in the south. See their figure 2.
If you want to see the albedo reductions, you will need a dataset for southern Greenland.

March 3, 2016 4:24 pm

The British would say “Spot-on!!!”
Well done & well researched!!! The 2012 melt has other implications but I lack the time to address them here!
Nice job Willis!!!

Reply to  Willis Eschenbach
March 4, 2016 8:01 am

And jungles don’t reflect sunlight, the plants eat it. 🙂

March 3, 2016 4:50 pm

Thanks Willis, I have to wonder too. I took that study’s conclusions at face value because I have been seeing so many photographs of surface darkening in Greenland, and so many moulins with leftover soot and ash at the bottom after they drain meltwater, so this seems to only make sense that there would be an Albedo change going on.
The 2012 Instamelt that created the spike was triggered by forest fire soot along with a weather event, see:
The last time an event like that happened was 1889. According to this researcher:
So, we know this can happen and it makes sense…but
From the study I posted today:

The study used satellite data to compare summertime changes in Greenland’s albedo from 1981 to 2012. The first decade showed little change, but starting around 1996, the data show that due to darkening, the ice began absorbing about 2 percent more solar radiation per decade.

And from the paper:

…surface albedo retrieved under the Global LAnd Surface Satellite (GLASS) project

I have to wonder, could we be missing something in the CERES data? Is the CERES resolution good enough to detect the 1-2% change they note from the GLASS data?

Reply to  Anthony Watts
March 3, 2016 5:17 pm

Also note that they are only looking at JJA summer data. The change in albedo could be because of surface melt water not black carbon.
BC would presumably affect the annual data W was looking at, melt water not. So that 1-2% would be 1/2 to 1/4 of that in the annual data.
2% of 182 W/m^2 would be detectable like the downward slope from 2000-2003 in Willis’ graph; 0.25 – 0.5% probably not.
To question their result it would be better to do apples to apples comparisons. ie extract JJA from CERES.

Reply to  Greg
March 3, 2016 7:37 pm

Good point about the JJA and melt water Greg. Maybe Willis will take your challenge and look at JJA for an apples to apples comparison. The melt water could certainly be a confounding factor.

Clyde Spencer
Reply to  Anthony Watts
March 3, 2016 6:27 pm

There are further confounding factors. The things that Willis listed with representative albedos all have diffuse reflectance, albeit often with a strong forward scattering. The proper and complete characterization of them is with a bidirectional reflectance distribution function (BRDF), which I doubt that CERES is capable of measuring. In the laboratory it is measured with a specimen at the center of a sphere or at least a hemisphere. Calm water and smooth ice have specular reflectance where the reflectivity varies with the angle of incidence of the sunlight (as well as the index of refraction, which in ice and water are similar). One often gets the impression that the total reflectance of water is much lower than what it is unless they are opposite the illumination and viewing the surface at the same angle at which it is being illuminated. I doubt that CERES is taking its readings by looking across Greenland into the sun. It would probably blind the sensors because all of the sunlight is concentrated into a narrow cone. All other things being equal, if one is observing a diffuse reflector, and sprinkle something else on it that has a lower diffuse reflectance, the composite will look darker. I suspect that what CERES is providing is relative diffuse reflectance, or a ratio to some material such as snow. It isn’t telling us everything about how much light the object is actually absorbing.

Reply to  Clyde Spencer
March 4, 2016 12:48 am

Algorithms. You only need a small tweek to make major changes. I don’t have a problem with algorithms, just the people designing them. You never get to see this stuff. Just take it on faith. BS. If I don’t see the algorithm then I dismiss it. Throw it on the table so everyone can see it. There are various ways to do things and some are better than others. I hate a produced ‘product’. Willis accepts it as gospel. Nothing against Willis.

Reply to  Clyde Spencer
March 4, 2016 12:56 am

Hemispherical reflectance is the main standard. That is qualitative. BRDF is ok for computer simulations of games

Paul Mackey
Reply to  Clyde Spencer
March 4, 2016 1:50 am

Hear Hear!

Don K
Reply to  Clyde Spencer
March 4, 2016 5:14 am

Clyde. What you are saying makes sense to me. This is far too complex for me to absorb in a few minutes. I’ve never worked in this area. But, I suspect that what CERES is measuring is indirect, diffuse reflection from under the satellite and that probably that is not easily related to albedo because a large, indeterminable(?) amount of the energy being reflected is going elsewhere. If so, CERES might be of great use for a lot of things. But likely not for determining albedo.

Clyde Spencer
Reply to  Clyde Spencer
March 4, 2016 9:20 am

Those involved in computer graphics use BRDF modeling because it is the only way to get realistic-appearing results. The corollary of that is if you aren’t using BRDF in the real world, you aren’t getting accurate results. What CERES and most satellites are measuring is an apparent reflectance — only what is seen by the satellite overhead. What the satellite doesn’t see is a part of the energy balance also, however. The question is whether it is a significant portion. Most diffuse reflectance, such as with snow, has a strong forward reflectance. If one isn’t measuring that forward lobe, then a lot of the energy is missed. For materials at the poles of Earth, the sun is never overhead! Therefore, there is going to be a substantial amount of reflected light that is not observed. For background on BRDF, see the following link:

Clyde Spencer
Reply to  Clyde Spencer
March 4, 2016 9:30 am

See . In particular, see the section on Terrestrial Albedo. They confirm that the satellites cannot see the total albedo and a model is used to estimate the total albedo based on BRDF of the assumed material. I have no personal experience with the model used and how effective it is or whether or not they take into account the sun elevation and topography.

Reply to  Clyde Spencer
March 5, 2016 12:59 pm

Agreed. Just to reinforce your point: BRDF is the standard for the modeling of light scatter from surfaces in optical systems. Albedo often assumes a Lambertian scatterer (reflected radiance is uniform in angle). Snow is a Lambertian reflector for light incident from directly overhead. Whenever one approaches steep angles of incidence, even a rough surface will develop a strong specular (forward) component. This could have a significant influence on the interpretation of the data. We know this in everyday experience, just by looking at a very quiet pond in the early morning. The smoother the surface, the darker it will appear from above, even if a significant amount of light is reflected. (By the way, the reflected light is also polarized, but that may be beside the point of this discussion.)
Tom Brown

Paul Mackey
Reply to  Anthony Watts
March 4, 2016 1:48 am

Good points Anthony. Having skimmed the above paper, I see much description of the computing systems used to resolve the data from the satallites, but I see no details of the capabilities of the sensor, even basic stuff like response vs wavelength and noise figures. Presumably these are available in the references somewhere.
It is important, for example the work I am involved with at present involved using remote satelite sensing to validate agricultural useage, such as areas and crop type. But there are some crops/land types that cannot be distinguished. So the utility of satellite data gathered, as with all experimental data, must be carefully looked for each use case.

richard verney
March 3, 2016 5:11 pm

What is significant here is that the albedo is lowest in the area covered by the tropical ocean, just where the impact of energy from the sun is most important. The absorption of solar irradiance into the tropical ocean is is powering/charging the heat pump of the planet, and one reason why the K&T energy budget cartoon is incapable of explaining planet Earth.
It is also noteworthy that albedo is highest where solar irradiance is at is weakest.

March 3, 2016 5:21 pm

It is clear from the photographs of moulins that BC gets wasted down and out by melting, so melting has a self correcting effect on albedo.

March 3, 2016 5:33 pm

Willis, thank you. Presenting these beautiful albedo graphics, figures 1 and 2. They are new to my eyes, and are worth, as you have done, deep pondering. For me the NH role for Greenland and SH Antarctica ice is massive as one can see from the red (72% Albedo). The recent posting on soot on/in ice is very interesting.

March 3, 2016 5:40 pm

Nick has posted the paper’s fig 1 against Willis’ graph upthread. They are not too dissimilar. It’s just that they cut off their graph at the bottom of the spike.
2012 was the end of what could have been read as “runaway” melting of Arctic sea ice. Any current analysis in 2016 that stops in 2012 will be very misleading.

Reply to  Greg
March 3, 2016 7:38 pm

Apparently dropped at the 2012 minimum to be intentional misleading and sensational.

Reply to  Greg
March 4, 2016 12:39 am

Its interesting when you flip the NH sea ice graph (not that one , but a similar one) and put it against the AMO.

richard verney
Reply to  Greg
March 4, 2016 1:17 am

Isn’t it a pity that you cannot easily at the data pre 1980.
The warmists have the data, but do not want people to see it since it shows the extent of natural variability. Increasing NH ice extent in the 1970s does not fit in well with the manmade global warming mantra and is difficult to explain given the increasing CO2 during that time.
For example see:comment image
See how the NH ice extent rose rapidly from 1974. Hence the promotion of the fear of a coming ice age.
This data is no longer included in recent IPCC Reports. Do you wonder why?

Reply to  richard verney
March 6, 2016 8:54 am

Has anyone tried to get the 70s data? FOIA? One for the USA congressional probe? Also, I have never seen this graph extended to today.

March 3, 2016 5:42 pm

Here’s a quote from the previous story:

The study also raises questions about whether Greenland’s high plateau is darkening as previous reports have suggested. The scientists found no long-term trend of darkening at the top, and they suspect that the Terra MODIS satellite sensor that has detected darkening in the past may actually be degrading, as previous studies have suggested. At lower elevations, the signal is much stronger.

It seems clear, to me at least, that the albedo change applies only to part of Greenland. In fact, this image makes it look like the high plateau covers most of Greenland.
In light of the above it seems unlikely that the albedo of Greenland, as a whole, changes much (which is pretty much what Willis found).

Reply to  commieBob
March 4, 2016 2:33 am

No such thing as a “high plateau” on Greenland. Large icecaps are flattish domes, not plateaus. Ice can only flow downhill, so a completely flat glacier is dynamically impossible. The Greenland cap consists of two coalescing domes, one southern and one northern. I presume by “high plateau” they mean the higher northern dome.

Reply to  tty
March 4, 2016 9:39 am

Perhaps they are referring to the rock underlying the glaciers rather than the glaciers themselves.

Other plateaus are … and the Canadian Shield or Laurentian Plateau, a U-shaped region of ancient rock, the nucleus of North America, stretching north from the Great Lakes to the Arctic Ocean. Covering more than half of Canada, it also includes most of Greenland … link

On the other hand, here’s a link to a map with contour lines. It shows Greenland as a big pile of ice with a kind of rounded top that falls off sharply on all sides.
My (not so well) calibrated eyeball tells me that about a third of Greenland would qualify as high, a third would qualify as low, and the rest would be the sloped bit that connects the two.
Your guess is as good as mine. 🙂

Reply to  tty
March 4, 2016 11:58 am

The bedrock in central Greenland is a Precambrian shield, so it’s fairly flat. However it is definitely not a high plateau, much of it is actually below sea-level.

Reply to  commieBob
March 4, 2016 2:14 pm

I’m pretty sure Willis’ results are correct. The problem seems to be that more than one viewpoint is represented in the story.

Yet the darkening of Greenland around its periphery remains a source of concern because it contributes to making the ice sheet melt away faster.

Willis’ results show that there is no measurable overall change in Greenland’s albedo. At most any albedo change would be local, which is implied by the above quote.

March 3, 2016 5:55 pm

“The average amount of energy reflected by the clouds plus the surface is about 120 W/m2. There is no trend visible over the period, and the standard deviation of the residuals (bottom panel) is only about ± 2.5 W/m2.”
CO2 collective RF 1750 to 2011 is 2 W/m^2. That’s less than one half the uncertainty in albedo.

March 3, 2016 5:55 pm

Anthony, have you seen this :
“More than half of the Greenland ice sheet melted last summer”
That is so stupid and ignorant that it deserves a fairly loud and public ridiculing.
I don’t recall reading about the resulting 3 metre high tsunami inundating most of the world last year.
I notified the editor about it but seem quite happy to carry on misleading their readers with this nonsense.

Reply to  Greg
March 3, 2016 7:34 pm

Greg march 3 @ 5;55 pm, thanks. This is the first time I actually read a complete article by the “Guardian” and read some of the comments, your evaluation of “stupid and ignorant” is very polite. I have a few other words that AW probably would not print. The comment are priceless, though I truly didn’t think people were THAT ignorant. Why are most of these people not fleeing to higher ground? I thought the right was always the “conspiracy”, “Trailer park” group, I have changed my mind on that one.( but maybe these people live in one room apartments and share the bathroom at the end of the hall on alternating days).

Reply to  asybot
March 4, 2016 2:40 am

The Guardian is a very leftist rag. Leftists are stupid and/or ignorant, if they weren’t, they wouldn’t be leftists.
Remember what Clemenceau said “If You aren’t a socialist at twenty you have no heart, if you are still is a socialist at thirty you have no brain”

March 3, 2016 6:29 pm

thanks again, Willis. i don’t always comment on your essays, but I always look forward to reading more.

March 3, 2016 6:47 pm

It is just incredible to me that the original “darkening” paper cut off their analysis at 2012. That is lying by omission.

March 3, 2016 6:58 pm

Terrific post. Dunno how accurate and precise (two different things) CERES is. Dunno how accurate the ‘black snow’ data is. Do know this is an impecably delightful post. Thanks, Willis.

Reply to  ristvan
March 5, 2016 5:22 pm

Willis: Thank you for the careful, thorough work as usual. Keep it up.
The point of the original was that “we” are darkening Greenland and the world is subject to “runaway” warming. A slightly different “we” from 1888-1889. Still, soot is soot so the Chinese (:-)) are at it again. Pretty soon them thar commies will be blamed for EVERYTHING. Err…well… modern free market economics will get the blame.

March 3, 2016 7:03 pm

This a NASA study for the first four years of your study period, while the sea ice was declining faster.
“Sea Ice and Snow Change, but Reflection Remains the Same”

March 3, 2016 7:23 pm

I think you may have indirectly answered why ice age glacials end so abruptly.
Once insolation is high enough, the first melt causes a dramatic water driven albedo shift to latch up the melting process. Not in Greenland, as we are at too low an insolation level right now, but 10,000 years ago, insolation over New York in summer was enough to have full surface melt… add some spring rains too and the melt would be dramatic. Shifting rapudly to more melt than winter snow.
That 2012 on steroids.
Oh, and per the Greenland graph: Their ending in 2012 is scientific malpractice. You caught them at it. Way to go!

Reply to  Willis Eschenbach
March 4, 2016 2:49 am

But there was always a vast amount of melting on the margins of the big icecaps in summer, even at Glacial Maximum. In Europe you have a huge belt of outwash sandplains all along the edge of the old icecap. In the US the Nebraska Sandhills are much the same, though the high winds off the Rockies have blown the sand into dunes.
A really big volcanic ashfall and a warm summer might do the trick though.

Reply to  Willis Eschenbach
March 4, 2016 7:04 am

Yep. That huge latent heat of liquefaction/solidification is one heck of a powerful tipper truck. I notice the radiative myopia merchants (who seem to forget water rapidly washes dust away or fresh snow rapidly covers it up) are back with their fag packets in hand. Diffusion through ice still has to happen; solid ice is far from a perfect insulator as its fluid behaviour shows. And my guess is it’s a lot more complex than we think, especially in thick ice sheets.

Reply to  E.M.Smith
March 4, 2016 2:06 am

Never mind the water driven albedo shift (whatever that is). The greatest change is the concentration of many previous dust layers further down through the ice sheet. This concentration of dust decreases the albedo almost exponentionally, and increases insolation absorption likewise.

Don K
Reply to  E.M.Smith
March 4, 2016 5:31 am

I wonder occasionally exactly how the continental ice sheets could ever have formed and have extended as far South as NYC (40N). I always come to the same answers. Either a dimmer sun. Or constant cloud cover accompanied by lots of snow. A few weeks ago, I watched the Winter sun at 45N take out 5 cm of fresh snow on a day when the temperature never got above -15C. If the Summer sun at 40N gets down to the surface any significant amount of the time, that glacial ice would seem to be doomed.

Reply to  Don K
March 4, 2016 8:19 am

Yeah but remember that last year the last snow clearings in Boston didn’t go away until July! So obviously survival and accumulation to the next year doesn’t take a huge change.

March 3, 2016 8:07 pm

Great work Willis. Very interesting. Seems to me that changing albedo and complicated ocean effects coupled with small variations in incoming solar radiation over time are the major drivers in climate. These effects apparently have driven the numerous glacial cycles in our current ice age that began about 3 million years ago. Large explosive volcanic events, large meteor impacts, and maybe even galactic dust are wild cards to add into the long-term mix. But CO2 seems to be a minor player and possibly more from how it effects plant growth than how it might possibly directly effect the radiation balance.
Unfortunately, it may take decades or even centuries to develop a real consensus and understanding of the complicated workings of climate and that may only happen when Earth inevitably begins trending into the next glacial period. I see nothing to indicate that the glacial cycles are going to be broken, although it would be greatly helpful for humans to break that cycle at the high temperature end as we are now. The next glacial period will be devastating for humanity, though certainly not insurmountable, especially considering our ancestors survived them … but with tiny populations compared to today. All this fuss about a small amount of likely net beneficial warming and CO2 increase seems such a waste of resources that could be much better spent. Perhaps we should be thinking more about ways to prevent the next glacial cycle. I don’t think more CO2 will help in that regard unfortunately. That would be too easy.

Reply to  Willis Eschenbach
March 4, 2016 1:25 am

I fully agree Willis, I would much rather work with 12 months per year and analyse it correctly. Your method was far better. I was just curious as to whether the JJA approach accounted for the difference. It seems not.
The main problem with the study is that it stops at the bottom of the spike and gives a very misleading impression.

Reply to  Willis Eschenbach
March 4, 2016 2:17 am

But oblique Sun angles do not show the true albedo, as the soot and dust particles bury themselves in the ice and are not visible at low Sun angles. And so the effective low albedo is only visible at midday in midsummer, and melting will only occur then (slope angle of the ice sheet notwithstanding). I will try to dig out the paper, when I get back.

Reply to  Willis Eschenbach
March 4, 2016 3:19 am

Here is the paper on Sun angle and albedo, showing that low Sun angles give little or no reduction in albedo because the soot particulates are hidden.
I am still sure that some of their diagrams are misllabled, but they did not answer my query.

Reply to  Willis Eschenbach
March 4, 2016 2:03 pm

>>False albedo.
Yeah, I see what you mean. Poorly explained. It highlights a couple of things.
If the satellite is measuring from above, and the Sun is lower on the horizon, then the albedo measured by the satellite will not be the albedo ‘observed’ by the Sun. The Sun will see a much higher albedo. And vice versa.
More importantly, the ‘albedo masking’ effect suggests that only a the three months around the summer solstice are important, when the Sun is in the zenith. At any other time of year, the effective albedo will be high no matter how much dust and soot there is on the surface, and no matter what the observed or calculated albedo may say.

Reply to  Willis Eschenbach
March 5, 2016 1:02 pm

using scene-dependent diurnal albedo models, which describe how TOA albedo (and therefore flux) changes with solar zenith angle for each local time, assuming the scene properties remain invariant throughout the day.
Interesting. So they do try.
However, are these adjustments simply for solar zenith angle changes on standard snow? Or do they actually allow for embedded and recessed soot deposits? I might suspect the former. No mention of soot or dust in that advice sheet.

Reply to  Willis Eschenbach
March 4, 2016 10:27 am

I always liked the Sidak correction more, as it is is universally more powerful than Bonferroni (hence Bonferroni correction got modified into Holm-Bonferroni which is also universally more powerful than naive Bonferroni; though Sidak is still slightly more powerful). Not that it has any relevance here, since the trend can’t even pass a 0.05 alpha, but I definitely encourage Sidak over Bonferroni whenever possible. Unless you need a per-family Type I error control, where one penalizes multiple simultaneous Type I errors as greater than just each Type I error on its own, which is where Bonferroni does actually excel over Holm-Bonferroni and Sidak.
Anyways, sorry for the random statistics ramblings!

March 3, 2016 9:07 pm
The change in albedo began ca. 1996 and may have been a stepwise change before your data began. This occurred exactly when the AMO flipped positive. They mention the NAO as a possible cause of this sudden change, but then continue with “Later records show those conditions shifted in 2013-2014 to favor less melting, but the damage was already done – the ice sheet had become more sensitive.”
Certainly a climate scientist would know that Greenland summer melt isn’t explained by the NAO, is strongly correlated to the AMO, and is very strongly correlated to the Greenland Blocking Index, right? They know that the AMO is still positive, right?

Reply to  RWTurner
March 4, 2016 12:34 am

“They know that the AMO is still positive, right?”
But just started to turn.
Arctic sea ice is pretty much exactly where it should be for the phase of the AMO.
Just outside 1sd from the mean.
PioMass shows increase in the last few years. We are pretty much out of the trough.
(unlike the climate alarmista, who’s nature place is in the trough)
This year will be a bit tough because of the temperature anomaly in northern Russia, but once the El Nino effect subsides, Arctic sea ice will be on the climb again..
And won’t it be fun to watch the AGW alarmist PANIC then !! 🙂

Reply to  AndyG55
March 4, 2016 1:19 am

Andy: Mention of the significance of the phase of the AMO reminded me of a comment in the (somewhat gushing) wiki biography of ME Mann:
“A paper published in April 2014 by Mann and co-authors set out a new method of defining the Atlantic Multidecadal Oscillation (AMO) in place of a problematic method based on detrending the climate signal. They found that in recent decades the AMO had been in a cooling phase, rather than a warming phase as researchers had thought. This cooling had contributed towards the recent Global warming hiatus in surface temperatures, and would change to enhanced surface warming in the next phase of the oscillation.[28] ”
It seems to me that the period 2000- present (the Pause) is actually in the positive trending part of AMO according to the chart above, contrary to Mann, so am I reading the AMO charts the wrong way round?

Reply to  AndyG55
March 4, 2016 4:31 am

The thing Mann was trying play on was that a perfect cycle on top of a upward slope will have it’s max a little later than the max of cycle itself.
It’s very little different , certainly not “decades”. But when you are desperate any little helps.

James at 48
Reply to  AndyG55
March 4, 2016 9:49 pm

I’m glad in a way that my life expectancy does not take me much past 2040. If I can hit my late 80s then out past mid century. I suspect by the 2060s the world will be fighting many unexpected issues having nothing to do with AGW. Some may have to do with cooling.

March 4, 2016 12:54 am

Low ice cover in Arctic is said to heat up the ocean and accelerate the melting. I always say the opposite.
Low Ice cover is typical in fall, late September.
Is it possible to figure out this using DMIs chart combined with Your figures?

Reply to  oppti
March 4, 2016 11:54 am

Since the rebound from 2012, it seems clear that the idea of open sea adding warming and leading to a postive feedback is demonstrably wrong.
This is just a handwaving alarmist claim that does not match observations.
while open water does have a much lower albedo than ice it is not the only process. What also happens is that water is almost “black” in the IR spectrum. This means much more outgoing IR and that happens 24/7/365 .
The rebound from the 2012 low in sea ice seem unequivocal in terms of which effect dominates.
If Willis can pull something out of CERES that will be interesting confirmation.

Reply to  Greg
March 4, 2016 11:57 am

Plus evaporative cooling of course and the latent heat of evaporation is huge.
It takes almost as much energy to change the state of a gram of water as it requires to get it from 20C to boiling.

March 4, 2016 1:03 am

This is a great post and I would not dare question things I no little about but would like to ask a question.
I’m just a layman so I’m sure many here might find the following a silly question but I find albedo confusing.
As I understand it, albedo is frequency dependant. For example, fresh snow/ice is a white body for visible or shortwave radiation but it is a blackbody for infrared wavelengths. Snow and ice melt due to infrared rather than sunlight because it reflects almost all SWR. Shouldn’t we be looking for sources of LWR to explain snow and ice melt (Such as warm ocean/water or rocks or air currents etc).
Does albedo say more about reflection and thus grey body calculations and should or do energy balance equations take frequency dependance into account when considering albedo?

Clyde Spencer
Reply to  Willis Eschenbach
March 4, 2016 5:02 pm

Emissivity is different from reflectance. Emissivity is the radiation from a heated body, e.g. the classic Black Body. Infrared can be reflected from an object, notably opaque bodies, as with an IR mirror.

Clyde Spencer
Reply to  Willis Eschenbach
March 4, 2016 5:13 pm

I should have also remarked about the classic relationship between emissivity and reflectivity: E = 1 – R

Reply to  Willis Eschenbach
March 5, 2016 2:29 am

Thanks for responding Willis, I was feeling a little foolish!
I was mixing up ideas about the adaptions some animals use to cope with heat exchange.
White seems like a bad choice for an animal at the poles and growing up I used to discuss this (However unscientifically!) with a mate, who also enjoyed musings about such things! 😉
If you want gain warmth in a cold place from insolation, black would be a better colour but it is a bad choice for heat loss! Polar bears have black skin and the fur is actually transparent. Their white appearance is caused by partial reflection and absorption. The fur is able to block all outgoing radiation such that they are invisible against background temperatures (Ice and snow) and impossible to detect with night-vision goggles (Except for a small patch visible when they exhale).
This made me think about the trade-off of darkening ice. Clean Ice absorbs visible light to such a depth that there is insufficient energy to melt it. Apparently, only thermal energy will do the trick. But dirty snow and ice will melt quickly from the thermal radiation provided by direct insolation alone. The trade off I guess, is that dirty ice and snow will also lose heat quicker but is the effect big enough to make a measurable difference to the slowing of a melt, enough to provide a feedback?
I’m not asking again, just musing out loud.
If I had any “swag’ I’d guess that no is the answer to my question!! 😉

Gareth Phillips
March 4, 2016 1:17 am

“Being an inherently suspectful type oif fellow”
I suspect your detractors may agree, but I believe you meant “I am a naturally suspicious type of person”
A suspect label is usually applied to the person in question as a negative term, not their thought processes, though it can be used in specific situations, as in “I think my wife suspects me”.
I know, I know, I need to get out more, but the weather here in Wales has been so bad for so ruddy long.
On the other hand, I’ll go and get my coat :

Reply to  Gareth Phillips
March 4, 2016 8:02 am

Gareth, “inherently suspectful” fits Willis to a T.

Jerker Andersson
March 4, 2016 1:26 am

Looking at the data for albedo I think the trend may not just tell you what is happening.
I think there is a “Flush” and “Cover” effect hiden also in the data which may make looking at the trend slightly less usefull.
What I am think is oncde the snow melts at the surface the black carbon hidden in the snow gets exposed and increase the energy absorbed. Eventually there will be water flowing on the surface and wash the black carbon away and it accumulates in certain spots or gets washed out in to the ocean.
After the meltflush is over there is less black carbon left and albedo increases and the trend gets pushed up again.
Also new snowfall will cover the black carbon and if the next years melt season does not melt all of last years snow then the underlying darker snow will cause less meltning.
So by just looking at the data I think that it is hard to say if the amount of black carbon has increased or decreased due to the “Flush” and “Cover” effect. You relly need to take snow samples every season before the melt season to see how much black carbon it contains to see if it changes.
It looks like there was a darkening 2010-2012 due to more exposed dirty snow but once it was flushed away and covered with new snow the did not melt entirely next season the albedo resumed to previous levels.

Reply to  Jerker Andersson
March 4, 2016 1:46 am

There has been problem with instrumental drift in albedo detection I recall. Darkening lenses.

Reply to  oppti
March 4, 2016 8:28 am

I would imagine that huge dust storms rose up during each Ice Age and made the ice dirty. This wouldn’t explain the sudden warming/sudden cooling of every Interglacial cycle.

March 4, 2016 1:54 am

Some observations on the paper cited here.
They are using the GLASS dataset, which uses information from the MODIS TERRA and AQUA sensors. This is the dataset.
And the data indicates that the albedo reductions are only occurring on the ice-sheet margins, and the southern portion of the ice-sheet. This was not made clear in the summary. However, this is to be expected, as significant albedo reductions will only occur where there is melting or ablation, and the dust and soot can concentrate on the surface. In the highlands, the dust is covered with fresh snow each year and is not visible (and thus not effective). So these albedo reductions only effect a small proportion of Greenland.
I am surprised that they are using ‘degrading’ satellite data, with precious little real-world confirmation. Greenland is a region that could easily be overflown with an aircraft bourne sensor. But I suppose that no grants are available for albedo research, rather than co2 research. However, they do report that ice core data suggests that soot deposites were worse in the early 20th century than today. Presumably, this was USA emissions, from when the USA had a proper manufacturing industry.
This lack of funding confirmed by the Dark Snow project, which could not get any grants and was forced to crowd-fund their research. And I am surprised that this study (which did get a grant) makes no real mention of Jason Box and the Dark Snow project, despite Box highlighting this topic since 2005. Is professional jealousy that strong in academia?
One other thing. I am not sure if this effects any of these results, but one study I saw said that you can only measure albedo from directly above. The soot grains sink into the snow and ice, and are not visible obliquely. So oblique albedo measurements will always be higher than zenith measurements. This also means that albedo melting will only really occur at midday in mid summer.

Reply to  ralfellis
March 4, 2016 4:34 am

“The version 1.0 of released GLASS albedo product has a temporal resolution of 8 days, and is available from 1981 to 2010. ”
So how did they run it out to 2012 ?

Reply to  ralfellis
March 4, 2016 4:38 am

… maybe by using data that the GLASS team regarded as unreliable. Maybe by graphing in another satellite.

Clyde Spencer
Reply to  ralfellis
March 4, 2016 9:44 am

For a second opinion on what is happening in Greenland, check this out:
Actually, whether there is soot/dust present or not, texturing of the surface from differential melting will create shadows if the sun is not directly overhead (which it never is). Thus, the apparent reflectance will be decreased in proportion to the shadow component, which is a function of the sun altitude and micro topography. It is all very complex!

Reply to  Clyde Spencer
March 4, 2016 2:15 pm

But clouds reflect insolation, and I rather think the redused insolation effect is greater than the increased insulation effect.
And regards albedo measuremnts. What this means is that measurements should be taken at the equal and opposite declination and azimuth as the Sun, otherwise the observed albedo will be incorrect. But that is not what has been done. Which rather suggests that aircraft should be used for observations, rather than satellites.

bit chilly
Reply to  Clyde Spencer
March 4, 2016 5:44 pm

same effect when the wind blows over the ocean,which is most of the time.

JJM Gommers
March 4, 2016 2:10 am

The residuals demonstrate sizeable peaks. The solar component is pretty constant. The differencies in the peaks represent more or less meltwater. The process of melting ice can be described as intial melting by changes in the atmospheric condition and accelerated by the subsequent change in albedo.
The number of peaks are limited so it seems that the local conditions are controlling the entire process

March 4, 2016 2:11 am

Tks Willis,
The take that I find important is the surface melt attributed to July 2012.
In decades to come, that will appear in ice cores as a paraconformity or disconformity or unconformity, a happening very well known to stratigraphers in geology. (Wiki defines terms. The period in which normal deposition was not happening was named a “hiatus” in anticipation of future fun: not).
Of interest is not so much a single season with melting, but a succession of seasons with melting, when non-melting is showing above and below in the core. The hiatus would be expected in almost any case where drilling was done where ice cover is transient. Less expected would be a hiatus in a well frozen area like inland Antarctica.
When we do not know the length of the hiatus in ice core, we have a timing problem because in ice core, as opposed to rock core, one relies much on layer counting to determine ages and time intervals. Hiatus can mean missing layers, missing years, a mistimed sequence.
It would be so easy to miss an unconformity in ice core. How can a core logger tell easily between an unconformity and a plastic flow layer of reduced thickness?
There is even the possibility of a hiatus lasting thousands of years. Therefore emphasis is placed on regional or global markers, where for example dust deposits from volcanos as matched in ice cores in time and space.
Personally, I think that there is too little mention of the possibility, even likely occurrence, of a hiatus or two in the ice core literature. Is this because it is overlooked, because it is seldom found in the chosen locations, or why? A recognised hiatus in Antarctic ice has important implications.
From readers, I’d be grateful for references in ice core literature to unconformities etc and hiatus periods.

Reply to  Geoff Sherrington
March 4, 2016 12:41 pm

Actually a major melt unconformity would be very conspicuous since it would collect all insolubles (dust, volcanic ash, micrometeorites etc) from the missing period in a single layer. Unconformities do occur and are a major problem in the deeper part of the cores, but they are caused by deformation of the ice as it moves over uneven bedrock.

Reply to  tty
March 5, 2016 2:39 am

Thanks, tty
The dust etc. ‘should’ accumulate and aid detection, but one can envisage scenarios where accumulation ‘might not’ happen. Any references in mind?

Berényi Péter
March 4, 2016 10:10 am

Glacier Girl (a Lockheed P-38F) was lost in 1942, 10 miles from the South-Eastern shore of Greenland on the ice sheet. Search began in 1981, it was found in 1988 using ground penetrating radar, two miles away under 264 feet of ice. It was dug out and flown again eventually.
Therefore average annual ice accumulation at that site was almost 6 feet for half a century, meaning much more snow, because it gets compacted into ice once buried.
I can hardly believe a single season’s surface melt may have lasting effect on albedo under such circumstances.

Reply to  Berényi Péter
March 4, 2016 12:05 pm

Nope, under 264 feet of compacted snow. The pressure is only high enough to turn the firn into solid ice at about 300 feet. Details here:

Berényi Péter
March 4, 2016 12:55 pm

Planes were found at a depth of 80 m.
Average density of firn down to that depth is much higher than that of fresh snow, because as pressure builds up, it gets compressed ever more.
To reach a depth of 80 m in half a century at least ten feet of annual snowfall is needed. It is never going to melt back sufficiently during the next summer to expose darker layers beneath, no way.

March 4, 2016 2:33 pm

The Dark Snow project also found a reduction in albedo in recent years.

March 6, 2016 6:27 am

I was poking around and discovered back in the 1960s for Cold War military exercises they were flying B52s constantly over Greenland. B52s belch out incredible amounts of soot, Ive seen it firsthand with the B52s that flew out of KI Sawyer, one smokey one also shown in the attached pic. I gotta wonder if a lot of that soot can be traced back to the B52s.

Reply to  Scott
March 6, 2016 6:44 am

Official name was Operation Chrome Dome, ran from 1960 to 1968.

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