UNIVERSITY OF CAMBRIDGE
Using satellite data to ‘see in the dark’, researchers have shown for the first time that lakes on the Greenland Ice Sheet drain during winter, a finding with implications for the speed at which the world’s second-largest ice sheet flows to the ocean.
The researchers, from the University of Cambridge, used radar data from a European Space Agency satellite to show that even when the heat from the Sun is absent, these lakes can discharge large amounts of water to the base of the ice sheet. These ‘drainage events’ are thought to play a significant role in accelerating the movement of the ice by lubricating it from below.
Previous studies of draining lakes have all been carried out during the summer months, through a combination of direct field observations and optical satellite data, which requires daylight.
The approach developed by the Cambridge researchers uses the radar ‘backscatter’ – the reflection of waves back to the satellite from where they were emitted – to detect changes in the lakes during the winter months, when Greenland is in near-total darkness.
The results, reported in the journal The Cryosphere, imply that the ‘plumbing’ system beneath the Greenland Ice Sheet doesn’t just slowly leak water from the previous summer, but even in the depths of the Arctic winter, it can be ‘recharged’, as large amounts of surface lake water cascade to the base of the ice sheet.
Many previous studies have shown that the Greenland Ice Sheet is losing mass, and the rate of loss is accelerating, due to melting and runoff.
“One of the unknowns in terms of predicting the future of the ice sheet is how fast the glaciers move – whether they will speed up and if so, by how much,” said co-author Dr Ian Willis from Cambridge’s Scott Polar Research Institute (SPRI). “The key control on how fast the glaciers move is the amount of meltwater getting to the bottom of the ice sheet, which is where our work comes in.”
Lakes form on the surface of the Greenland ice sheet each summer as the weather warms. They exist for weeks or months but can drain in a matter of hours due to hydrofracturing, transferring millions of cubic metres of water and heat to the base of the ice sheet. The affected areas include sensitive regions of the ice sheet interior where the impact on ice flow is potentially large.
“It’s always been thought that these lakes drained only in the summer, simply because it’s warmer and the sun causes the ice to melt,” said co-author Corinne Benedek, also from SPRI. “In the winter, it’s dark and the surfaces freeze. We thought that the filling of the lakes is what caused their eventual drainage, but it turns out that isn’t always the case.”
Benedek, who is currently a PhD candidate at SPRI, first became interested in what happens to surface lakes in the winter while she was a Master’s student studying satellite thermal data.
“The thermal data showed me that liquid water can survive in the lakes throughout the winter,” she said. “Previous studies using airborne radar had also identified lakes buried a few metres beneath the surface of the ice sheet in the summer. Both of these things got me thinking about ways to observe lakes all year long. The optical satellite imagery we normally use to observe the lakes isn’t available in winter, or even when it’s cloudy.”
Benedek and Willis developed a method using data from the Sentinel-1 satellite, which uses a type of radar called synthetic aperture radar (SAR). SAR functions at a wavelength that makes it possible to see through clouds and in the dark. Ice and water read differently using SAR, and so they developed an algorithm that tracks when sudden changes in SAR backscatter occur.
Over three winters, they identified six lakes which appeared to drain over the winter months. These lakes were buried lakes or surface lakes that were frozen over. The algorithm was able to identify where the backscatter characteristics of the lake changed markedly between one image and the next one recorded 12 days later.
The SAR data was backed up with additional optical data from the previous autumn and subsequent spring, which confirmed that lakes areas shrank considerably for the six drained lakes. For three of the lakes, the optical data as well as data from other satellites was used to show the snow- and ice-covered lakes collapsed, dropping by several metres, again confirming the water had drained.
“The first lake I found was surprising,” said Benedek. “It took me a while to be sure that what I thought I was seeing was really what I was seeing. We used surface elevation data from before and after the events to confirm what we were thinking. We know now that drainage of lakes during the winter is something that can happen, but we don’t yet know how often it happens.”
“Glaciers slow down in the winter, but they’re still moving,” said Willis. “It must be this movement that causes fractures to develop in certain places allowing some lakes to drain. We don’t yet know how widespread this winter lake drainage phenomenon is, but it could have important implications for the Greenland Ice Sheet, as well as elsewhere in the Arctic and Antarctic.”
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If lakes drain, that amount of fresh water floating on the top, when it freezes may not melt by the following summer, that would indeed be climate change emergency.
Huh? We have this phenomenon that hasn’t been previously described. We have no idea of what it has done over history. As far as we can tell, it’s doing what it has always done.
It’s like treating the ozone hole like something that has never before occurred in the history of the planet.
Oh look, there’s something. OMG, it just changed. We’re all going to die! Something like that.
Something changed and we’re all going to die is the pillar of AGW.
The rent seekers only have to quantify change to get paid.
It would be loverly if they had to take it one step further and qualify how much and how long the change has to be before even 2% of the population is affected.
If I recall correctly, at it’s current rate of melt, refreeze, and accumulation, Greenland will raise the ocean sea level about a foot in a thousand years?
“… at it’s current rate of melt,…Greenland will…“
Please stop buying into the bullshit! Greenland isn’t melting. It may have some surface melt much like the surface melt and re-freeze that forms icicles on your roof in January. But in general it isn’t melting, it’s well below freezing nearly everywhere, nearly all the time, it can’t melt.
Er, or maybe several localized source of heat that isn’t affected by darkness or -40 temperatures. Volcanoes and geysers exist, without dependency on alarmism. But I wouldn’t mind sacrificing some extinction cosplay hysterics into a few.
These lakes must have existed before this study started looking at them. Therefore the scientists have to re-assess all past work and all past observations of ice gain or loss, in order to understand what has been happening up until now. We aren’t looking at a sudden acceleration of ice loss from these lakes, in spite of the writer’s intention to make us think that way. We are looking at a process that has been going on for ages and that we weren’t aware of. Basically, nothing has changed. Before this study at the observed rate of ice loss, it was going to take 10,000 years or more just for half of Greenland’s ice to melt. After this study, it will still take 10,000 years or more just for half of Greenland’s ice to melt.
Spot on – BINGO – Plus Ten – Exactly etc.
Besides all that:
These ‘drainage events’ are thought to play a significant role in accelerating the movement of the ice by lubricating it from below.
The operative word in that line of bullshit is “Thought”.
The glaciers move over the surface the same way ice skates do. The weight of the skater or the glacier forms a thin layer of water allowing it to slide. Adding more water isn’t going to make it slide any faster. And as was pointed out this has been going on right along as it is with every other breathless “worse than previously thought” announcement of newly discovered phenomenon in the world of Climate “Science”.
.
.
It’s worse than we thought! Apparently none of the Climate Cyan Tits (h/t Leo smith) have ever ice skated.
Shocking!
Cyan (/ˈsaɪ.ən, ˈsaɪˌæn/)[1][2][3] is a greenish-blue color. [Wikipedia]
Ha ha ha ha ha ha ha ha ha!
First chuckle of my day and saved to my file of factoids, quotes and smart remarks. (-:
It’s my understanding that much of the interior ground-level of Greenland is bowl-shaped. So the drainage of the lakes enable the interior ice sheet to move uphill?!
Yes, I saw that a few days ago. I’m going to check to make sure that I added that one to my file of factoids, quotes & smart remarks
As long as the top surface of the ice is sloping down towards the edge of the ice cap, the ice will move in that direction. If you look at glaciated terrain like the Canadian Shield, you can see lots of places where the ice has moved over hills. It’s easy to visualise if you learn to regard ice as a plastic, not a rigid medium.
Credit Leo Smith, Steve. I stole it from him. He used it a couple of days ago.
In the context he used it, the word play was not as obvious, and it took me a minute.
Leo wrote about the writers of the science releases – “wannabe Cyan Tits.”
Then I cottoned on to what he was referring to: the type who flunked math, then physics, then chemistry, then accounting, then psychology (crikey!), and they couldn’t weave a basket and flunked basket weaving 101. So they got their degree in journalism 😜 and write these releases.
Thanks for lesson in etymology (-:
“The key control on how fast the glaciers move is the amount of meltwater getting to the bottom of the ice sheet, which is where our work comes in.”
But it isn’t the only one. The roughness of the rock surface (friction) and the weight of the glacier will also affect how fast it moves
“Pressure beneath glaciers is not constant due the roughness of the ground surface. Higher pieces of ground increase the ice pressure as the glacier moves over that bump, thereby increasing the temperature and reducing the level of friction. Moving on from that higher piece of ground the pressure reduces, decreasing the temperature and then the level of friction increases. The cycle continually reoccurs at different rates and locations, depending on the roughness of the ground surface.”
https://www.tribonet.org/modeling-ice-friction-in-glaciers/.
Did they factor that in? I’m not sure that they did.
fretslider
Yes, the topography and total relief are important considerations. If the bedrock is polished and has little relief, then the ice can speed up if water is newly introduced to the ice-bedrock contact. However, this is only likely near the terminal margins where the ice might be thin enough that plastic flowage won’t seal tension cracks.
If the topography has high relief, then the ice will either have to shear over, or flow around, obstructions. Adding water won’t have much impact because the ice movement is being buttressed by obstructions, not just retarded by friction.
So I wondered how many of these “lakes” there were in Greenland. I went to Google Earth Pro /tm) and scanned around, even zoomed into select areas, like where someone had noted a photo. The majority of satellite data is obviously old data with large pixels, like maybe Landsat, I saw one scene labelled as 1984, for example, with newer Quickbird smaller pixel data only near items of interest. I can report that I found no lakes, even though these were all summer scenes. Changing to the comment that the water from draining lakes speeds up a glacier, I will remark that all of the glaciers visible were moving to the sea, often in fiords, where they calved, all appearing normal. The movement of a glacier is controlled by the recharge rate in upper areas and the inclination and roughness of the topographic low the glacier travels over. Without recharge at the origin a glacier stops moving, and judging from the amount of calving ice clearly visible, these Greenland glaciers are moving along in a mode that has to be close to normal. Nothing to see here, folks, move along.
Using satellite data to ‘see in the dark’, researchers have shown for the first time that lakes on the Greenland Ice Sheet drain during winter, a finding with implications for the speed at which the world’s second-largest ice sheet flows to the ocean.
“Many previous studies have shown that the Greenland Ice Sheet is losing mass, and the rate of loss is accelerating, due to melting and runoff.”
That’s wrong! The DMI reports here:
http://polarportal.dk/fileadmin/user_upload/PolarPortal/season_report/polarportal_saesonrapport_2020_EN.pdf
beginning on page 3 on the melting and calving of the ice sheet.
Figure 2 on page 4 shows, that the melting in 2017, 2018 and 2020 was less than in previous years and -surprise (?!)- and in 2017 and 2018 was no loss in the Total Mass Balance. The loss in 2020 was only about 150 Gt/y.
The data show that the ice sheet has lost less and less mass since its maximum loss in 2012, with fluctuations until today, i.e. just the opposite of what is often claimed.
The rate of loss is not accelerating, it is slowing down, and very significantly!
Says in there that melting started 10 days later than average in 2020
I just checked the date, are we sure this is a genuine story?
Sadly, it looks to be a genuine story, not an April Fool joke.
https://tc.copernicus.org/articles/15/1587/2021/
Quote:””Cambridge researchers uses the radar ‘backscatter’ – the reflection of waves back to the satellite from where they were emitted””
Well isn’t that the craziest thing
Because when we’re all being lectured, told, re-educated, brainwashed, arm-twisted, trolled, ad-hommed, bore-holed, ignored, cancelled, fined, taxed, tattooed and derided about the Green House Gas Effect….
…. No Such Thing as ‘backscatter’ Is Possible.
We’re told that when a photon, carrying (electromagnetic) energy is emitted from somewhere anywhere, it HAS to be absorbed by whatever it hits.
No matter what the temperature of either ‘party’
Otherwise we are bludgeoned by a supposed violation of the 1st Law
We are told about ‘Net Energy Flow’
Isn’t that right Spencer? No, this is not some sweet Socialist Share & Share Alike Disneyworld.
Thermodynamics is cold and hard.
There is NO net flow. Energy flow ONLY goes in one direction and if it cannot be absorbed by whatever it hits, it ‘backscatters’
Yet here it is with all the Inarguable Authority of A Sputnik
This climate thing is the Biggest Pile Of Stinking Rotten Shyte that there ever was.
But its now too late to call it out.
Hansen should have been pulled to shreds 30 years ago, but, The Good Men Said Nothing.
and there’s nowhere left to run to…
Edit to add:
And yes, i do realise this is radar and ‘reflection’ we’re talking about.
OK
Why was Grenfell Tower covered on plastic foam to try keep it warm,
Why not inward facing mirrors?
Ah you say, the foam was coated with Aluminium – that’s shiny stuff
Yes it is but it also has vanishingly low emissivity, hence why the Aluminium is fitted on the cold-side or the outside, not on the warm inside
Thus the combination of low thermal conductivity allied to low emissivity would have kept the tower warm
Exactly as Earth’s Atmosphere has. Low conductivity and low emissivity
Whether one is talking about visible light, IR, or radio waves, a fraction will penetrate and be absorbed in solid objects like water, ice, or rock, and the rest will be reflected, with the proportions being determined by the complex refractive index applicable at the particular wavelength, and the angle of incidence of the wave front. Look up Fresnel’s Equation for reflectivity.
Stupid comment. Ever use a “space blanket”? It’s an aluminized blanket used for wintertime emergencies. It doesn’t have any insulating properties as it’s made from only 12 micron thick mylar – it’s thinner than a human hair. It works by reflecting the IR emitted by the human body back to the body and, secondarily, by helping to reduce convection heat loss. Other than making the person who is being saved clammy, it works very well. Warms a person right up. They’re now being used at Biden’s border cages as cheap blankets. So why don’t you just cover the person with a few microns of dirt to save them? The reason that a space blanket works is that Aluminum reflects IR while dirt absorbs IR and re-radiates it away from the body.
What reflects and what is absorbed depends on the frequency of the EM radiation and the material. Most people learned that in school, it’s why different objects can have different colors under a white light.
Here and I always thought that the way radar worked was to emit a signal, detect the reflected signal (that part of the backscatter reaching the detector) figure out the time difference and you’ve got the distsance to the object reflecting the signal. (This is, clearly, a simplified explanation.)
Interesting issue. Greenland is losing ice mass since the end of the little ice age, but Greenland has gained a tremendous amount of ice over the last 5k years. The recent acceleration is nothing more than the positive phase of the AMO. We know since 2012 or so that Greenland has been getting colder.
What they don’t tell you is that the Greenland glacier contains 2 850 000 cubic kilometers of is and that the main glaciers thickness is between 2 to 3 kilometers which I mention in this video.
https://youtu.be/UJOEr964GpI
Thanks for the You Tube link. I’ve book marked it for reference
Here is a recent paper on Greenland temperatures that was posted at No Trick Zone
Yawn.
Mountain, meet molehill.
Sorry Bruce, but I think that should be something like “Molehill, henceforth you shall be called Mountain”
3 of the 6 lakes they tracked showed elevation declines associated with the change in backscatter. I agree this is evidence the water below an ice layer drained away. But the other 3?
If they didn’t get any significant elevation decline yet the backscatter change indicated a decrease in liquid water, maybe it flash froze from a super-chilled state? That water would be pretty pure, so a rapid freeze could occur and actually releasing latent heat. Still its so cold, -30 to -50 C warming a few degrees wouldn’t matter.
Reusable handwarmers work by releasing latent heat when snapping a metal clip induces a rapid crystallization inthe amorphous gel.
Typically an aqueous solution of ammonium nitrate.
It’s not winter and 99.9% of Greenland is currently below freezing. This must be that fresh water that doesn’t freeze at 0 C.
I remember, probably a decade ago, about ice penetrating radar showing ancient river systems under the ice on Greenland. These were estimated as having existed for 2 million years. My guess is that melt water follows the course of these rivers to the sea. I’d guess that this has been happening for as long as gas there’s been a Greenland Ice cap.
Ben,
The water has to make it to bedrock to flow in the old river channels (Most of which no longer have the same gradient because the weight of the ice has depressed the center of the land.) The water would encounter plastic deformation of the ice after a couple hundred feet depth, which would tend to seal tensional cracks for the next few thousand feet.
In short, it is improbable that meltwater can reach bedrock in the interior, and if it did, it would then have to flow uphill to reach the sea.
I don’t give much credence to your “guess.”
Current rate at which Greenland drains is around 9,500m^3/s. (This is after that 10% increase) Let me know when it hits 20,000m^3/s. That is when the final draining of the ice sheet will begin. It should give us 150-250 years to finish draining.
Nothing new here, please check A. E. Nordenskiöld, Science 1883.
Antero Järvinen, Finland
OMG! Greenland drains water?!?!
Haven’t you heard? It just started last week. Now we’re doomed. If it doesn’t stop, we’ll all be rooned! Evacuate the coastlines, before it’s too late! Oh, the humanity!
Radiation from the sun is the primary source of energy for the Earth’s climate system. Changes in the Earth’s orbit around the sun cause variations in the seasonal distribution and amount of solar radiation reaching the earth. Records of past climate show that there is a correlation between these variations and long‐term climate changes [Hays et al., 1976; Imbrie et al., 1992]. Interglacial conditions begin with increasing mid‐latitude summer insolation and end as mid‐latitude summer insolation decreases. Orbital‐scale climate cycles are driven largely by variations in solar radiation associated with precession, obliquity and eccentricity of the Earth’s orbit. Recent studies of the Asian monsoon show that the transitions between the glacial and interglacial conditions took place abruptly, perhaps only in century‐long events [Wang et al., 2001; Yuan et al., 2004]. However, it generally takes about 10 ka for the insolation to change from a minimum to maximum and vice versa.
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2005GL025401
“The key control on how fast the glaciers move is the amount of meltwater getting to the bottom of the ice sheet, which is where our work comes in.”
The amount is nil in the interior! The lubricating effect, if any, will be restricted to the terminal margins and is typically revealed by tensional cracks at the boundary between the accelerating ice and the unaffected ice. The movement of the ice is similar to that of a river, where friction slows the water at the bottom and sides, with maximum velocity at some distance above the bottom in the center of the channel.
It would be important to know where in Greenland these lakes are located that supposedly drain through crevasses in the glacier. If they are located only a few miles from the edge of the ice cap, the water at ground level may have a clear path to the sea, which would result in a net loss of mass of the ice cap, and a rise in sea level.
However, Greenland has a mountain range a few dozen miles inland from most of the coastlines, with an inland plain, or basin, surrounded by higher mountains. If the “lake” water seeped through the glacier into this basin, it would be trapped by the mountains, and could not flow to the sea. Since ice has about 91% of the density of water, about half of the ice would have to melt before the remaining ice could float above the lake water below.
Summer melting is only one component in the mass balance of the Greenland ice sheet. Snowstorms in autumn and winter add snow on top of the ice sheet, which becomes packed down as snow accumulates, and some is turned into ice, in the absence of sunlight. Snowfall is particularly abundant along the east coast of Greenland, since the Atlantic remains ice-free for much of the autumn and winter, providing an ample supply of moisture for storms along the coast (similar to the nor’easters observed along the Atlantic coast of the USA in winter).
In 1945, a group of American World War II pilots were trying to land their planes in Iceland for refueling after returning from Europe, and were blown off course by a storm and forced to ditch their planes in southern Greenland, then were rescued a few days later. During the 1990’s, these pilots went on an expedition to search for their planes. They did not find the planes at the surface, although the planes were located using remote sensing, under about 100 meters of ice. This shows that, at least at the ditching site, ice was accumulating at a rate of about 2 meters per year.
(There were several posts on the WUWT site about this incident).
Would this ice accumulation balance out any losses due to “lakes” seeping into the glacier and maybe flowing out to sea?
In the book “The Two Mile Time Machine” (an Ice Core), it is pointed out that fresh water added to the North Atlantic will freeze,during the winter and eventually shut down the Gulf Stream that brings warm weather to Europe.
There is certainly enough water in the Greenland Ice cap to bring that about, perhaps it is already beginning to happen!
Let’s summarize.
They’re using synthetic aperture radar (SAR) data that images water differently from ice.
When the “lakes” showing drastic drops of water imaging, these researchers automatically assume the lake drained…
Why not the water froze? A far more likely possibility in a Greenland winter.
Full confirmation bias on display.