From THE EARTH INSTITUTE AT COLUMBIA UNIVERSITY
By mid-century, more Antarctic snowfall may help offset sea-level rise
Increasing precipitation masked by natural variability — for now
In a new study, scientists used historical records and climate simulations to examine that question. They found that the effect of rising temperatures on snowfall has so far been overshadowed by Antarctica’s large natural climate variability, which comes from random, chaotic variations in the polar weather. By mid-century, however, as temperatures continue to rise, the study shows how the effect of human-induced warming on Antarctica’s net snow accumulation should emerge above the noise.
The expectation of more snowfall is something of a silver lining as temperatures rise. Global warming is already increasing sea level through melting ice and thermal expansion. The increase in snowfall over Antarctica could help reduce the amount of global sea level rise by 51 to 79 millimeters, or about 2 to 3 inches, by the year 2100, according to the study. That would be a small but important benefit: the Intergovernmental Panel on Climate Change estimates global sea level rise will be at least 10 times that by 2100 under the same high-emissions scenario used in the new study.
“Increased snowfall over Antarctica is the sole process connected to global warming that is thought to have a significant mitigating effect on global sea level rise,” said lead author Michael Previdi, a professor at Columbia University’s Lamont-Doherty Earth Observatory. “While the magnitude of this effect is uncertain, it is likely that the balance of different processes determining Antarctica’s net contribution to global sea level rise will be decidedly different in the future than it has been in the recent past.”
On a continental scale, surface mass balance is the difference between the amount of snowfall that accumulates and the amount of snow lost to sublimation. It affects global sea level because the amount of water on earth is essentially constant, so when more water is stored as snow or ice on land, less water is available to contribute to rising seas.
For the study, published this week in the journal Environmental Research Letters, Previdi and co-author Lorenzo Polvani of Lamont-Doherty Earth Observatory evaluated surface mass balance simulations from 35 coupled atmosphere-ocean climate models, which simulate the physical forces that affect Antarctica.
The models allow scientists to quantify both the human influence on surface mass balance and the influence of natural variability. The scientists found that from 1961 to 2005, global warming increased Antarctica’s surface mass balance by 124 billion tons per year, smaller in magnitude than natural year-to-year variability, which was found to be plus or minus 126 billion tons per year.
When the scientists looked at all 35 models, 46 percent of the individual simulations showed a statistically significant trend in surface mass balance from 1961 to 2005, the year that most of the models’ historical simulations end. The likelihood of seeing a statistically significant trend in surface mass balance rises as the models forecast ahead in time. After 2015, the models cross a threshold where it becomes “likely,” with a 66 percent chance, that evidence of anthropogenic climate change will emerge in Antarctica’s surface mass balance. By 2040, it becomes “very likely,” with a higher than 90 percent chance.
Previdi and Polvani repeated their analysis with different emissions scenarios and also considered surface mass balance trends starting in 1979, at the dawn of the satellite era. The analyses showed similar results, with the global warming signal “very likely” to emerge by mid-century.
“The apparent discrepancy between models and observations can be easily reconciled by considering the large surface mass balance variations generated naturally within the Antarctic climate system,” they write.
Previous studies also found no significant change in the total Antarctic surface mass balance in recent decades, though a 2013 ice core study found a 10 percent increase in surface mass balance in coastal regions since the 1960s. All temperature records, meanwhile, indicate that Antarctica warmed from 1961 to 2005. Ice cores also show a strong relationship between the continent’s surface mass balance and temperature changes through history, including the end of the last ice age when temperatures rose dramatically.
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The paper, “Anthropogenic Impact on Antarctic Surface Mass Balance, Currently Masked by Natural Variability, to Emerge by Mid-Century,”
http://iopscience.iop.org/article/10.1088/1748-9326/11/9/094001
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Another wasted study what else is new.
‘May’ Warning sign, right there.
And ‘46% of the models show…’
But clearly, 54% didn’t.
“The apparent discrepancy between models and observations can be easily reconciled by considering the large surface mass balance variations generated naturally within the Antarctic climate system,” they write.
Wikipedia says that a surface mass balance is the difference between accumulation and ablation (sublimation and melting). So they could have said the net gain or loss of snow and ice but that would be too clear.
Did they realize they are saying that their models can’t follow natural climate? And that makes them a waste of money and time? These guys are clueless.
It is well established in the literature that global climate models do not downscale regionally. So to use CMIP5 for just Antarctica was a fools errand from the beginning.
ristvan, you are correct, but as I have pointed out repeatedly before, these aren’t global climate models that downscale regionally. The model structure is based on small pieces of ocean/atmosphere over very small timescales. By definition, conditions in a small place over a short time are weather not climate. The models are therefore local weather models that try to upscale regionally and globally. None of them are climate models.
They are hedging their bets. They been predicting that sea level rise will accelerate due to global warming. When it doesn’t happen they can explain that global warming caused more snowfall in Antarctica which affected the sea level rise.
In other words, if sea level rise does accelerate it will be due to global warming. If sea level rise does not accelerate it will be due to global warming. No matter what happens, it will be evidence of global warming.
“By mid-century, however, as temperatures continue to rise,”
The temperatures are not rising. Think: Flatline.
It would be the most accurate statement to say without apology, “we don’t know what is going to happen at the South Pole over the next 50 years”. It would also be completely truthful.
Perhaps there has been no increase in snowfall because the oceans around Antarctica haven’t increased in temperature.
I do find it interesting that their excuse is that natural variability ate their data.
The only time natural variability exists with these guys is when they need to it to hide the fact that the real world doesn’t match their models.
Somehow I have the feeling the “13 state of the art climate simulators which were built by hundreds of scientists over many years” [Liu & Allan (2013)] did not predict this.
“There was a clear tendency for the wet regions to become wetter and the dry regions drier during the 21st century in response to global warming.”
Bouvet island lies 1100 miles to the norh of Antarctica and is almost completely covered in permanent ice, although nowhere is it above 800meters altitude. Bouvet is significantly “warmer” than Antarctica and even the wildest projections of the Warmists don’t give Antarctica similar temperatures in a hundred years time. In fact average temperatures in Bouvet are only around 2C colder than Winnipeg, it has an icecap because summer temperatures barely rise above freezing and precipitation is very high. Hard to see how giving Antarctica a more Bouvet like climate would diminish its ice cover
All based on an unproven assumption then:
Have they quantified the ‘human induced global warming’? apart from the natural global warming? If they have not then their study is mere confirmation bias and cherry picking.
Wow – they finally discovered chaotic climate variability! What happened? They must have run out of routes to skirt around the 6000 pound gorilla in the room. But no matter – chaotic variation that will soon be swept aside by global warming.
What if it were the other way around? What if global warming were about to be swept aside by chaotic variation?
This is the perfect study!! It’s bound to be proved correct. When it gets to 2100, and sea level has risen by, say 8 inches, they (or their descendants), can confidently say – ” We told you so – without the extra snowfall in Antarctica, it would have risen 11 inches”
Seriously, though, it does sound rather far-fetched.
The world’s oceans have about 25 times the area of Antarctica, so 3 inches of sea level is equivalent to about 75 inches of extra snowfall. Between now and 2100 that works out to about an extra inch per year.
Now according to their “model” , which is probably not too far off whatever measured values there are for snowfall on the Antarctic plateau, there is about 25mm (1 inch) per year of accumulated snowfall. So they are expecting it to double……
Presumably they have factored in an assumed warming of about 2 degrees, which would push average annual temperatures in the interior from about -40 to -38. Enough to cause snowfall to double???.
On the other hand, imagine going to all the trouble of producing a paper which concluded “There won’t be much difference”. Not the way to get invited back for another one…….
Oh Dude we all have better things to do than giggle over stupid all day lol this whole article is like what happened to be today, I got a txt message from the Boss saying “get over here you have to see this” So I turned up on site (hung over) and spotted our two guys standing around a board on the wall with around 15 wires hanging out, so I walked over to inquire what was going on when I get a call from the boss laughing his ass off saying “do you see it yet?” he was behind us watching from the office, I said “no what’s going on?” he said “have a look” it took me 5 seconds to notice that there was a circuit missing, so basically our two engineers were stuck all morning testing the board and sending the Boss almighty txt messages that there has to be a new circuit wired which would actually cost around 5k, That’s all well and good if your customer doesn’t mind getting an additional 5 grand to their bill and that wasn’t going to happen, so while my boss was laughing down the phone I told our guy’s (who are really great btw) to dress the board and I’ll take it from there, to save any embarrassment, I went up to the office and found my boss laughing in delight how he spent the morning watching two engineers lose the plot over something so simple, He’s paying them and I just didn’t care lol anyway, how I resolved the issue was to walk back down to our guys and show them how to save 5 grand by simply replacing the circuit with a cheep 2k resister to make the board work correctly.
See the relevance? lol I don’t care 🙂
“Anthropogenic Impact on Antarctic Surface Mass Balance, Currently Masked by Natural Variability, to Emerge by Mid-Century,”
high addictive potential. tiring repetitions.
An oceanographer buddy of mine swallowed the AGW hook, line & sinker. I referred him to this site, and I hope he takes a look at it. He’s been claiming 9″ of 20’th Century sea level rise, but there’s been scarcely a millimeter in Miami since 1980. Your own eyes can debunk that myth.
It may have already masked sea level rise.
We can expect the most dramatic increases of sea level to happen during droughts in Antarctica.
No doubt snowfall in what is now central Canada increased 20,000 years ago.
It didn’t stop that ice cap from disappearing.
Snow doesn’t fall and stick when ice is melting.
stevekeohane
Depends on the circumstance. Land ice, sea ice, surface (skim layers) of thin ice over a freshwater melt pond, air temperature, dew point, wind … For example, the sea water under a layer of ice may be continuously melting “up” while snow accumulates on top. (This often occurs down south around Antarctica.) Snow may fall on a thin layer of ice overnight, while the air temperature and solar energy melts both through the day .. This is what Judith Curry observed in August-September up north. True, if the surface of the land is at “air temperature” and snow is falling, both will melt – you see this on your driveway as the concrete/earth melts snow while snow accumulates on the grass nearby.
@ur momisugly RACookPE1978
What you are describing is more along the line of a weather event. I was referring to the climate shift that caused the glaciers to retreat. If glaciers are melting and retreating, there is no snow accumulation.
That any given glacier is retreating (losing mass) does NOT imply nor confirm that there is no snowfall. It does imply that there is less snowfall gains (at the top of the glacier) than the mass loss away from the top of the glacier.
More properly, For a Alpine-style glacier, if the snowfall at the top of the glacier is cumulatively less than the the mass of compressed ice and snow moving down the mountain, then the total mass of the glacier decreases. As mass decreases, the toe of the glacier moves uphill (towards the head) and the glacier shortens.
But only a few areas of the Antarctic are alpine-style mountainous glacier with a clearly defined head and toe ending in the sea. The entire central mass of the continent is a huge high plateau of near-solid compressed ice. That glacier mass is increasing overall, while only the short glaciers on the West pennisula are decreasing.
Like the Greenland icecap, there is almost no slope across the central antarctic continent: Some slope? Yes over many hundreds of kilometer it drops by meters, but not enough to “move” the ice mass like an Alpine glacier down a mountain valley.
“By mid-century, however, as temperatures continue to rise, the study shows how the effect of human-induced warming on Antarctica’s net snow accumulation should emerge above the noise.”
My first thought is that if the signal is supposed to be in the noise, how do they know it’s there? (Oh right… the models told them)
One has visions of them all sitting around waiting for the the signal to peer up above the noise… could be a long wait.
According to the tidal gauge measurements the rate of sea level rise in the 19th century was the same as it was in the 20th. Roughly 1.5-2mm per year. And yes I realize there are now people (hack frauds) who claim 3mm or more but they are not it measuring it the same way and obviously can not compare that to 19th century rates.
You need to warm the water in the ocean to melt the ice caps. And according to the measurements that has not occurred
http://science.nasa.gov/science-news/science-at-nasa/2014/06oct_abyss/
These tiny surface temperature changes (half the warming since 1950 according to the catastrophic proponents) don’t melt the ice caps. Go to your freezer and turn the temperature up 0.2 C and see what happens
Then again, it may not.
Another study by people who have never been to Antarctica. In my experience the major winds are katabatic flowing from the centre of the East Anatrctic ice sheet down slope to the oceans. Falling snow only occurs near the coast after the sea ice has broken up in mid to late summer. The moisture in the cloud adds to the snow cover when cloud and surface come in contact with each other. Mt Odin in the Dry Valleys is without snow until December ish. The snow line that then appears is a consequence of the cloud height.. the snow line does not represent snow above and rain below (because it never rains) snow forms when cloud touches the colder land or ice. I doubt that coastal cloud actually penetrates inland very far at all before all its vapour has been accreted to existing ice.
I only experienced one snow fall that was maybe 10 mm deep but it had all sublimed within a few hours.
In the Transantarctic mountains, just below the polar Plateau, the annual snowfall was of the order of 5 mm per year. It is uncertain whether that was fallen snow or blown snow.
I have seen blown snow the plateau that was over 400 m thick, anyone within that area would call it a blizzard and not realise that it was blown snow not falling snow. It is so cold in Antarctica that snow does not compact and become part of the ice for years, it just gets blown around from place to place with every storm.
On the basis of what I have observed their paper smacks of people sitting in front of computers making assumptions based on their ignorance. Science ain’t what it used to be.
No. Those winds you describe exist. Where you were.
Your experience of your small position on the continent is as valid for the entire continent as a life-long, never-traveled Indiana, Illinois, or Kansas resident to condemn a description of the ski-slopes of NH, VT, or Colorado. Or the deserts of Nevada and Utah. Or the lava fields and tunnels in Idaho.
There is a map of Antarctic wind patterns on this thread: It shows only a few such adiabatic winds off of the central highlands and ice of Antarctica. most of the coastal winds are sideways (parallel to) the coast, with the remainder split between on-coastal and off-coastal average directions.
There ARE such high, dry, very cold winds as you experienced. But they are NOT everywhere, nor are they the dominant winds around the entire 14 Million sq kilometer continent.
Great comment. As a meteorologist, I often wondered how Antarctica got all that ice in the first place, since it is extremely cold there on the ice cap almost all the time. Could it be that snow falls on the upwind edges of the continent, where air enters from the sea, (not just condensing directly on the surface) then gets blown around from there? Katabatic winds that descend from height (the glacier) are dry, warming as they descend. Such winds would evaporate snow and ice, not deposit it or blow it around.
RACookPE1978 is quite correct, it depends very much where you are. The continual gale force winds described by Mawson at Commonwealth Bay were katabatic. The ceaseless down slope wind referred to by Scotts party on route to the pole etc. The graphs you refer to are winds at present and even those show that at least 75% of the plateau wind is down slope. Katabatic winds do not occur all the times maybe once a fortnight where we were, obviously more at Commonwealth Bay.
At Lake Vanda in the Dry Valleys to predominant wind, in summer (like 95%) is easterly but that is due to the thermal effect of the dry valleys causing air to rise once the sun is high enough and being replaced by air off the sea ice coming up valley. .The katabatic winds were the only winds strong enough to override the daily thermal induced wind. I have no doubt that near the coast the winds would be predominantly westerly (as they are in NZ and for the same reason) but I suspect that such moisture laden winds do not get far inland before their vapour is accreted to the ice. A view supported by the graph earlier showing where snow is deposited in Antarctica.
Both at Cape Hallett and at Vanda (before the daily easterly starts) the weather for most of the time is fine and calm.
With reference to R Blacks comment, yes the katabatic wind is warm and dry (about 7% RH), but that is relative in Antarctica -10 is warmer than -20 but not warm enough to melt ice. They certainly increase the rate of sublimation but to say that snow would not be blown around simply tells me you have never been there. I spent a week in by Upper Wright glacier that spills ice from the plateau into the Wright Valley. 3 days of that week were spent in a tent waiting for the katabatic to finish, blasted by blown snow the whole time. We also witnessed many times from Vanda the layer of blown snow above the plateau with clear sky above during the katabatic winds.