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Denman Glacier–Latest Antarctic Meltdown Scare

March 24, 2020
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By Paul Homewood

 

From the “We’re all going to drown department”:

 

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Scientists have found a new point of major vulnerability in the Antarctic ice sheet, in a region that already appears to be changing as the climate warms and has the potential to raise sea levels by nearly five feet over the long term.

Denman glacier, in East Antarctica, is a 12-mile-wide stream of ice that flows over the deepest undersea canyon in the entire ice sheet before spilling out into the ocean. That subsea trough is more than 2 miles deep, or double the average depth of the Grand Canyon. While there are far deeper trenches in the open ocean, such as the Marianas Trench, in this case the extreme undersea topography lies right on the outer fringe of the Antarctic continent — making it the “deepest continental point on Earth.”

That deep canyon is a potential pathway for the ocean to infiltrate deep into Antarctica’s center — posing a threat of significant sea level rise.

Denman glacier, which fills the submerged canyon with extremely thick ice, has begun to respond to climate change. It is creeping backward down a slope that plunges into these extreme depths, new research finds, potentially igniting a feedback process that could ultimately unload trillions of tons of ice into the ocean

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“The configuration of the bed of the glacier makes this one of the weakest spots in east Antarctica,” said Virginia Brancato, a NASA scientist who was the lead author of the new study in Geophysical Research Letters. “If I have to look at East Antarctica as a whole, this is the most vulnerable spot in the area.”….

The study used satellite techniques to determine the “grounding line” of Denman glacier has retreated inland more than 3 miles toward the center of Antarctica in the past 20 years.

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The “grounding line” of a marine glacier, such as Denman, is the point deep beneath the sea surface where ocean, bedrock and ice all meet. Farther outward from the grounding line, the ice is afloat and no longer touching bedrock. Farther inland, the ice no longer has contact with the ocean.

If a grounding line is moving backward, more ice is floating, and the ocean is penetrating further inland with the glacier in retreat. That’s what’s happening at Denman, scientists say.

In this case, the grounding line has not only moved backward, but it has also moved down a steep slope into the two-mile-deep canyon atop which the glacier sits. This means the ice front that the glacier presents to the ocean has gotten thicker. It is more than a mile thick, but it has the potential to increase to two miles of thickness if the glacier backs fully into the depths.

Scientists describe this type of glacier configuration as a “retrograde slope” and have determined it can lead to a runaway feedback process in which ice loss begets more and more ice loss. The more the glacier’s grounding line backs down the slope, the thicker the ice becomes. This means the ice can flow outward faster and also that more of it will be exposed to ocean waters capable of melting it.

“In this configuration, it means that once the glacier starts retreating, it’s very hard to stop it,” said Eric Rignot of the University of California, Irvine, one of the study’s authors. “You sort of open the floodgates.”

Elephant seals fitted with sensors on their heads have been used to take measurements of the water temperatures off the coast of Denman glacier. The resulting readings show temperatures more than sufficient to melt ice, around -1 degrees Celsius, in the ocean offshore at about 300 meters of depth. If that water is making its way beneath the glacier’s floating portion, its “ice tongue,” and all the way to the grounding line, the melting potential would be high and explain why Denman already is in retreat.

“We have the indirect signature of that warm water by the fact that the ice is melting from the bottom at relatively high rates compared to the rest of East Antarctica,” said Rignot.

Denman already has lost over 250 billion tons of ice, researchers have calculated, equivalent to a little over half a millimeter of sea level rise. But there are 540 trillion tons of ice loss potential if the glacier were to travel backward across the entire subterranean canyon — a distance of nearly 100 miles. At this point, the melting could then reach a critical area of Antarctica called the Aurora Subglacial Basin.

Here, enormous volumes of ice rest on a bed well below sea level. If the ocean gets into the Aurora Basin due to the loss of Denman glacier, there is the potential for nearly five feet of sea level rise.

It’s unclear how fast this dynamic could play out. In a region with a complex and little understood undersea topography, it’s unknown how much warm water is making it to the base of Denman, and that makes a huge difference, said Donald Blankenship, a glaciologist at the University of Texas at Austin who has conducted extensive research on East Antarctica.

https://www.washingtonpost.com/climate-environment/2020/03/23/denman-glacier-climate-change/

It’s hard to know where to start with this nonsense.

For a start, it is implied that the recent retreat of the glacier is linked to a warming climate. However the climate has actually been getting colder in that part of Antarctica during the period of the study, which begins in 1979:

station

https://data.giss.nasa.gov/tmp/gistemp/STATIONS/tmp_AYM00089611_14_0_1/station.png

The point is admitted that it is actually warm water at a depth of about 300m which is undercutting the glacier. But it is physically impossible for greenhouse gases to have any measurable effect at all on waters at such a depth.

But what is measurable is that sea surface temperatures are currently colder than average all around Antarctica:

https://www.ospo.noaa.gov/data/sst/anomaly/2020/anomnight.3.12.2020.gif

https://www.ospo.noaa.gov/data/sst/anomaly/2020/anomnight.3.12.2020.gif

 

In reality the scientists who wrote this study do not have a clue whether the retreat of the Denman is anything new or not, or whether the deep ocean temperatures are any warmer than before 1979. Or whether what they are observing is just a natural process.

 

We can then go on to explore sea level implications.

They claim that since 1979, 250 billion tonnes of ice has been lost, equivalent to 0.5mm of sea level rise. In other words, 1.3mm/C, hardly cataclysmic.

They then go on to talk about a potential loss of 540 trillion tonnes, raising sea levels by 5 feet. Yet at current rates, it would take 86400 years for this to occur!

As always with these sort of studies, the authors refuse to say how long all this will take to happen.

 

But it gets even more absurd!

Look again at the topography of the Denman Glacier:

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It is reckoned to be 11500 feet deep, the deepest point on continental Earth apparently.

Yet the canyon comes to a halt roughly at the place where the glacier ends. In other words, most of the ice locked into the canyon cannot simply escape into the ocean, as it would have to flow uphill.

Even if it all melts, as a result of the inflow of warmer ocean water, the ice in the canyon will simply be replaced by water. Crucially, this means that sea levels cannot rise as a result. This can only happen when ice on land enters the sea.

18 Comments
  1. Broadlands permalink
    March 24, 2020 6:51 pm

    Last September it got so bad that: “Scientists propose Artificial Wall to stop collapse of Antarctic glaciers”. “Scientists think a giant artificial wall propped up under Antarctica’s ice sheets could stop catastrophic sea level rise.” Problem solved!

    • Gary Pearse permalink
      March 28, 2020 2:52 am

      Or that such a wall could actually stop a glacier like this!!

  2. Gamecock permalink
    March 24, 2020 6:59 pm

    ‘and has the potential to raise sea levels by nearly five feet over the long term.’

    “Long run is a misleading guide to current affairs. In the long run, we are all dead.”— John Maynard Keynes

  3. Simon Kelly permalink
    March 24, 2020 7:01 pm

    Thank you Paul for keeping going with the day job. You can sure as mustard that the Ecoloons will be emboldened and back in force once the Coronafascits have destroyed western civilization by using a nuclear warhead to crack a rather nasty but not that large nut.

  4. Gamecock permalink
    March 24, 2020 7:06 pm

    There is a logical problem for the melting glacierists.

    The rate of sea level rise has been constant for a hundred years. Either glaciers are not melting, or their melting makes no difference to sea level.

    Either way, they can be ignored as cranks.

  5. jack broughton permalink
    March 24, 2020 7:28 pm

    It remains amazing that “scientists” are publishing and “peer reviewing” such poor quality biased work. The press are also continuing as far as they dare at the moment with the fear campaign, i.e. publishing any sensational opinion from a “scientist” or “expert” without any allowance for alternative opinions. The tragedy is that people are being conned by pseudo-scientists.

  6. March 24, 2020 8:20 pm

    As they search for more ‘new points of major vulnerability’ in the Antarctic ice sheet, the more they will find.
    It’s just an axiom of scientific research.

  7. March 24, 2020 9:52 pm

    It’s like whack-a-mole with these endless fake glacier alarms.

  8. Gary Kerkin permalink
    March 24, 2020 10:01 pm

    I’m not a poet but here is my view of the BBC and this article in particular.

    Gotta keep the pressure up,
    The world is going to shit.
    If we don’t keep the pressure on,
    It certainly won’t be long,
    Despite being just so brave,
    Before we are in our grave.

    But, dammit, this is the pits,
    The BBC’s forlorn,
    Have we all done lost our wits,
    Because coronavirus’ s thorn,
    Has displaced climate change.

    So we will strive to keep alive,
    Alarm which is so chilling,
    Just in case of interest dive,
    In things we think top billing.

    There is no doubt we’ll publish here,
    Info most misleading.
    By citing numbers huge and large,
    Which keep alarmists feeding.
    And prevent with all our strength and might,
    The absolute reality,
    That such large numbers might be right,
    But tell us, in honest common sense,
    That but a tiny fraction of the whole
    Is all it represents.

  9. Graeme No.3 permalink
    March 24, 2020 10:08 pm

    I recall that a few years ago a number of scientists (plus media from the ABC and The Guardian) set off to visit Mawson’s huts in the Antarctic and study the loss of ice due to global warming climate change.
    They got stuck in sea ice 110 km. from where he moored his ship in 1910.

    Called for some reason “the ship of fools”. They tried to arrange another trip the next year but it fell through (lack of funds?).

  10. March 25, 2020 7:12 am

    Have they given up on West Antarctica?

    https://tambonthongchai.com/2020/03/22/10684/

  11. dave permalink
    March 25, 2020 11:48 am

    “…retrograde slope…”

    Surely, before the glacier ‘creeps backwards’ it has to melt downwards at its front using water at -1 C. (a couple of degrees above the freezing point of salt water. ) How can this happen ‘rapidly’ ?

    • dave permalink
      March 25, 2020 12:13 pm

      On further consideration, how can water at -1 C melt ANY ice in the glacier at depth? That ice is pure water and -1 C is below the freezing point of it.

      The whole point about ‘calving’ is that the berg does not MELT into the ocean; it breaks away, and stays intact until it is swept away into warmer waters.

      This particular pebble dropped into the global echo-chamber is desperately silly. The whole ‘paper’ (technically, merely a ‘letter’) is only a few lines of jargon. The ‘news’ seems to be that there is a hole in the bottom of the ocean under the Denman Glacier, full of ice.

  12. Mad Mike permalink
    March 25, 2020 12:27 pm

    It could be argued that the melting of under sea ice is actually inhibiting sea level rises as ice expands when it is frozen and presumably the volume of water seen after melt will be lower that the ice it replaces. This being so the melting should be welcomed. I don’t think it will get a hooray from Greta though.

  13. March 25, 2020 2:16 pm

    This is just a replay of the EAIS Totten Glacier nonsense I wrote about over at Climate Etc a couple of years ago. Same faulty iceshed assumptions.

  14. Bemused Bill permalink
    March 27, 2020 11:10 am

    Its all just the usual bollocks, I don’t even pay any attention to it at all anymore…every time they go on with this crap about Antarctica it turns out to be insane exaggeration or an outright lie…here is the current SST anomalies from Weather Zone…and I have been keeping an eye on this now for over a decade…and this is actually about as warm as I have seen it around the Antarctic…does it look like its under terrible threat to you? Because if it does I have an excellent bridge in Sydney I am selling…going plenty cheap, not making any profit…..another observation I would make is the oceans as a whole globally are unusually cool. A legit scientist would be asking questions about that ….
    https://www.weatherzone.com.au/climate/indicator_sst.jsp?lt=global&lc=global&c=ssta
    Keep up the good work guys, the general public internationally are voting against the bullshitters…meaning we are winning. Even after the latest huge climate hysteria spend.
    PS. Remember a few weeks back how the world was coming to an end because of the terrible warm conditions at the Antarctic below Tierra del Fuego? FAIL!!! How much research money do you think those retards received for that crap?

  15. dennisambler permalink
    March 27, 2020 1:04 pm

    “once the glacier starts retreating, it’s very hard to stop it”

    You can see why he’s a scientist.

  16. Gary Pearse permalink
    March 28, 2020 2:50 am

    A good dose of sense as usual, Paul. No one thought to consider that the trench may have been gouged out by this enormous glacier over countless millennia? In any case, it surely has been doing what it is doing for millions of years. All glaciers issue ice or water into the sea.

    Also, heat flux from the interior of the planet and friction of the moving ice makes the interface between the bottom of the ice and the rock ‘wet’. The Russians drilled through a couple of miles of ice and found a water lake, complete with living micro organisms that hadn’t seen the light of day for what? 30 million years?

    https://sciencenordic.com/animals-and-plants-climate-denmark/bacteria-thrive-on-methane-deep-beneath-the-antarctic-ice-sheet/1448111

    Paul, I’ve cited your work on raw temperatures on several continents that have a very similar pattern to that of the US with 1930s-early 40s highest temperatures for the 20th century, now adjusted out of existence. Capetown raw, “pre-homogenization” could be mistaken for the US record. I think a redo of this topic would be timely.

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