From the AGU and the “but, but, the continent is melting!” department.
COLDEST PLACE ON EARTH IS COLDER THAN SCIENTISTS THOUGHT
WASHINGTON — Tiny valleys near the top of Antarctica’s ice sheet reach temperatures of nearly minus 100 degrees Celsius (minus 148 degrees Fahrenheit) in the winter, a new study finds. The results could change scientists’ understanding of just how low temperatures can get at Earth’s surface, according to the researchers.
Scientists announced in 2013 they had found the lowest temperatures on Earth’s surface: Sensors on several Earth-observing satellites measured temperatures of minus 93 degrees Celsius (minus 135 degrees Fahrenheit) in several spots on the East Antarctic Plateau, a high snowy plateau in central Antarctica that encompasses the South Pole. But the researchers revised that initial study with new data and found the temperatures actually reach minus 98 degrees Celsius (minus 144 degrees Fahrenheit) during the southern polar night, mostly during July and August.
When the researchers first announced they had found the coldest temperatures on Earth five years ago, they determined that persistent clear skies and light winds are required for temperatures to dip this low. But the new study adds a twist to the story: Not only are clear skies necessary, but the air must also be extremely dry, because water vapor traps some heat in the air.
The researchers observed the ultra-low temperatures in small dips or hollows in the Antarctic Ice Sheet. The super cold, super dry air is denser than the slightly warmer air around it, so it falls into the hollows and becomes trapped. This allows the snow surface and the air above it to cool further, until the clear, calm, dry conditions change and the cold air mixes with warmer air higher in the atmosphere.
“In this area, we see periods of incredibly dry air, and this allows the heat from the surface of the snow to radiate into space more easily,” said Ted Scambos, a senior research scientist at the National Snow and Ice Data Center at the University of Colorado-Boulder and lead author of the new study in Geophysical Research Letters, a journal of the American Geophysical Union.
The record of minus 98 degrees Celsius is about as cold as it is possible to get at Earth’s surface, according to the researchers. For the temperature to drop that low, clear skies and dry air need to persist for several days. Temperatures could drop a little lower if the conditions lasted for several weeks, but that’s extremely unlikely to happen, Scambos said.
Blowing snow conditions at a camp site near Vostok Station in Antarctic summer.
Credit: Ted Scambos, NSIDC/University of Colorado-Boulder.
Finding the coldest place
The high elevation of the East Antarctic Plateau and its proximity to the South Pole give it the coldest climate of any region on Earth. The lowest air temperature ever measured by a weather station, minus 89 degrees Celsius (minus 128 degrees Fahrenheit), was recorded there at Russia’s Vostok Station in July 1983.
But weather stations can’t measure temperatures everywhere. So in 2013, Scambos and his colleagues decided to analyze data from several Earth-observing satellites to see if they could find temperatures on the plateau even lower than those recorded at Vostok.
In the new study, they analyzed satellite data collected during the Southern Hemisphere’s winter between 2004 and 2016. They used data from the MODIS instrument aboard NASA’s Terra and Aqua satellites as well as data from instruments on NOAA’s Polar Operational Environmental Satellites.
The researchers initially saw a broad region of the plateau more than 3,500 meters (11,000 feet) above sea level where temperatures regularly dropped below minus 90 degrees Celsius (minus 130 degrees Fahrenheit) at the snow surface. The lowest temperature they observed was minus 93 degrees Celsius (minus 135 degrees Fahrenheit).
Data from the MODIS instruments is calibrated using temperature measurements from weather stations on the ground. In 2016, NASA recalibrated the MODIS data with more up-to-date weather station measurements, and the researchers reanalyzed the temperature data. The weather conditions on the plateau did not change, but the adjusted satellite data gave the researchers a more accurate picture of what the actual lowest temperature was.
They found the record low was about 5 degrees Celsius (9 degrees Fahrenheit) colder than they originally reported, about minus 98 degrees Celsius (minus 144 degrees Fahrenheit).
Persistent winds shape the surface of East Antarctica’s snow into small dune forms called ‘sastrugi’.
Credit: Ted Scambos, NSIDC/University of Colorado-Boulder.
How cold can it get?
Scambos and his colleagues analyzed the terrain where they saw these ultra-low temperatures and found they occurred in small hollows 2 to 3 meters (6 to 9 feet) deep in the surface of the ice, on the southern side of high ridges on the plateau.
Interestingly, the researchers noticed a whole cluster of places where temperatures plunged almost exactly to that record low over the 14-year period, even though they were located hundreds of kilometers apart. That got them wondering: Is there a limit to how cold it can get on the plateau?
For the temperature to drop to that record low, skies must be clear and the air must be bone-dry for several days. After the temperature drops below a certain point, the air cools so slowly that it can’t get perceptibly colder before the weather conditions change, according to the researchers. Minus 98 degrees Celsius, then, appears to be the limit to how cold it can get at Earth’s surface, Scambos said.
“There’s a limit to how long the conditions persist to allow it to cool to these ultra-low temperatures, and a limit to how much heat you can actually get through the atmosphere, because water vapor has to be almost nonexistent in order to emit heat from the surface at these temperatures,” he said.
The research team has developed a set of instruments designed to survive and operate at the very coldest places throughout the winter to measure both snow and air temperatures. They are planning to deploy the instruments within the next two years.
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This paper is freely available for 30 days. You can download a PDF copy of the article by clicking on this link:
https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2018GL078133
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Its been some time since I heard anyone use the expression “bone dry”.
Wow. If they run this analysis in another 5 years or so, no telling how cold it’ll get.
Another way of looking at it: the difference between the “coldest ever” and our current “global temperature” (snicker) has gotten larger – IT’S WORSE THAN WE THOUGHT!
Yup. As long as there are bucks in CACA, the spin will be that global warming is making Antarctica colder!
Where is Tisdale and his cold related adjective?
“The researchers observed the ultra-low temperatures in small dips or hollows in the Antarctic Ice Sheet. The super cold, super dry air is denser than the slightly warmer air around it, so it falls into the hollows and becomes trapped. This allows the snow surface and the air above it to cool further, until the clear, calm, dry conditions change and the cold air mixes with warmer air higher in the atmosphere.”
____________________________________________________
It’s not that these “super cold, super dry air” dips get deeper.
Just that the surrounding “warmer = wetter environment” gets more precipitation
and stacks the ice shield higher ’round the dips.
What’s new, pussycat.
No. Read the paper. The (shallow) hollows get colder because the air there gets trapped and doesn’t flow downhill towards the coast as it gets colder and heavier. These are the infamous katabatic winds that have caused the coasts of East Antarctica to be called “the home of the blizzard”.
Precipitation is extremely low everywhere in inland East Antarctica.
Say what – we name such “Inversionswetterlage”:
https://www.google.at/search?q=inversion+weather+situation&oq=inversion+weather&aqs=chrome.
“because water vapor traps some heat in the air.”
I did get a chuckle at this understatement.
Having done considerable instrument calibration work over 35 years, I find this description problematic. It sounds as though the researchers applied new 2016 calibration results to data taken in earlier years. Presumably the instruments had been calibrated in some previous time. Maybe several years earlier. A serious problem arises when a recalibration of an instrument shows it is no longer within normal tolerances. That is, trying to determine when it changed and whether or not previously recorded data is valid. Was the change a gradual linear drift? Did it start right after the previous calibration or only recently? Was the previous calibration just not done correctly?
When this issue arises, as it sometimes does in critical laboratory measurements involved in litigation, it is not uncommon to simply declare all measurements made between calibrations invalid. In many cases there is simply no way to prove convincingly that data can be corrected for the error discovered.
One must also ask, was this 5C error in MODIS measurements of temperature also present in all the other temperature data collected in the previous years? Will it be necessary, or indeed possible to correct that data as well?
The problem was apparently that the very coldest temperatures (<180 K) had been rejected as cloud-contaminated. You can read the details here:
http://sci-hub.tw/10.1029/2018GL078133
“The continent is melting”?
If you go look at the CO2 phase diagram, you’ll note that CO2 is hitting the depositional line (phase change gas to solid) at that temp (-98 C) and pressure (11,000 feet).
No it doesn’t. That phase diagram is for pure CO2. At the very low partial pressure in the atmosphere it won’t condense until -135 C.
However if you put a slab of solid CO2 there it would evaporate very slowly if it was windless. Some CO2 would evaporate and since it is heavier than air it would accumulate locally and raise the partial pressure. However even a breath of wind would disperse the CO2 cloud and speed up evaporation.
The cooling of the atmosphere is influenced by the increase in the amount of O3 and 14CO2 in the lower stratosphere, because it causes a decrease of water vapor in the tropopause.
Therefore, the temperature in winter during low solar activity must fall.
How can there be no water in the air where these low temperatures have been recorded? The whole interior of the continent is buried in ice!
Something tells me neither Nasa GISS nor Cowtan & Way of ‘Best’ are clamoring to add that temperature extrapolation into their temperature reconstructions.
So they admit that even fairly small quantities of water vapour have a big effect? Now if they just model that correctly the CO2 thing should disappear forever and water will become a pollutant!
If mankind fails to take action soon, then eventually the maximum low temperature will be only 96 degrees C.
Which put new perspective on alleged 0.6°C global warming over the last century.
It also intimates that if the Arctic was a similar sized land mass with 11,000 meter altitudes, that the Arctic would be equally cold.
Which suggests that alleged 0.6°C CAGW warming or even 6.0°C CAGW warming barely affects Arctic or Antarctic temperatures.
Joe Bastardi regularly points out that Global Warming claims rely upon sparse polar temperature measurements. That global temperature increases are dependent upon warming during Polar winters, not evident during Polar summers, and most evident during night, due to water vapor levels.
Concordia Station
-71 °C
Snow flurries. Passing clouds.
Feels Like: -83 °C
Latest Report: 27 cze 2018 02:00
Not to worry it will be better than two degrees F warmer in another hundred years or so.
Not only are clear skies necessary, but the air must also be extremely dry, because water vapor traps some heat in the air.
DUH!!