Record of Antarctic ice sheet response to climate cycles found in rock samples

Posted: September 17, 2022 by oldbrew in climate, Natural Variation, research, sea levels, Temperature
Tags: ,

Antarctica


Climate cycles and natural variability do exist then?! No need to re-visit those discussions. Quote: “One of the key findings is that the ice sheet was responding to temperature changes in the Southern Ocean”. The study says: ‘Our findings imply that oscillating Southern Ocean temperatures drive a dynamic response in the Antarctic ice sheet on millennial timescales, regardless of the background climate state.’
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By analyzing unusual rock samples collected years ago in Antarctica, scientists at the University of California, Santa Cruz, have discovered a remarkable record of how the East Antarctic Ice Sheet has responded to changes in climate over a period of 100,000 years during the Late Pleistocene, says Phys.org.

The East Antarctic Ice Sheet is the world’s largest ice mass. Understanding its sensitivity to climate change is crucial for efforts to project how much sea level will rise as global temperatures increase.

Recent studies suggest it may be more vulnerable to ice loss than previously thought.

The new study, published September 15 in Nature Communications, provides evidence of changes at the base of the ice sheet over a broad area in response to cyclic changes in climate during the Pleistocene. The changes are reflected in the types of minerals deposited at the base of the ice sheet.

“One of the key findings is that the ice sheet was responding to temperature changes in the Southern Ocean,” said coauthor Terrence Blackburn, associate professor of Earth and planetary sciences at UC Santa Cruz. “The warm water eats at the edges of the ice sheet and causes the ice to flow faster, and that response reaches deep into the heart of the ice sheet.”

The rock samples analyzed in the study consist of alternating layers of opal and calcite that formed as mineral deposits at the base of the ice sheet, recording cyclic changes in the composition of subglacial fluids.

“Each layer in these samples is a manifestation of a change at the base of the ice sheet driven by changes in the motion of the ice streams,” said first author Gavin Piccione, a Ph.D. candidate working with Blackburn at UCSC.

By dating the layers, the researchers found a striking correlation between the layers of mineral deposits and the record of polar sea surface temperatures derived from ice cores. The opal was deposited during cold periods, and the calcite during warm periods.

“These climate oscillations are causing changes in ice sheet behavior such that the chemistry and hydrology beneath the ice is changing,” said coauthor Slawek Tulaczyk, a professor of Earth and planetary sciences at UCSC who has been studying the behavior of ice sheets and glaciers for decades.

The climate cycles that match the mineral layers are relatively small fluctuations that occur every few thousand years within the more pronounced glacial-interglacial cycles that occurred every 100,000 years or so throughout the Pleistocene. The glacial-interglacial cycles are driven primarily by changes in Earth’s orbit around the sun.

The smaller millennial-scale climate cycles involve oscillations in polar temperatures driven by weakening and strengthening of a major ocean current (the Atlantic Meridional Overturning Circulation, or AMOC) which transports large amounts of heat northward through the Atlantic Ocean.

Tulaczyk said the new findings reveal the Antarctic Ice Sheet’s sensitivity to small, short-term climate fluctuations.

“As important as the Antarctic Ice Sheet is—it’s responsible for close to 17 meters of sea level rise since the last glacial maximum—we really know very little about how it has responded to climate variability,” he said. “We know the last 20,000 years pretty well, but beyond that we’ve been almost blind. That’s why these results are so mind-blowing. People have been banging their heads against the wall over this for decades.”

Full article here.
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Study: Subglacial precipitates record Antarctic ice sheet response to late Pleistocene millennial climate cycles (Sep. 2022)

Comments
  1. oldbrew says:

    From the study:
    Mineralogic and geochemical variations in subglacial precipitates provide evidence for periodic changes in subglacial hydrologic connectivity between the AIS interior and margin that occur contemporaneously with bipolar seesaw-related Southern Hemisphere climate cycles.
    – – –
    ‘The polar see-saw (also: bipolar seesaw) is the phenomenon that temperature changes in the northern and southern hemispheres may be out of phase.’
    https://en.wikipedia.org/wiki/Polar_see-saw

  2. Gamecock says:

    ‘Understanding its sensitivity to climate change is crucial for efforts to project how much sea level will rise as global temperatures increase.’

    No, son, your work isn’t crucial.

  3. […] Record of Antarctic ice sheet response to climate cycles found in rock samples | Tallbloke’s T… […]

  4. They keep writing stuff as if it was “proven facts” when it is just peer review consensus of “pure guesses” by people who have been wrong about most things that have actual proof.

    They frequently write: The glacial-interglacial cycles are driven primarily by changes in Earth’s orbit around the sun.

    The glacial-interglacial cycles are internal cycles of the climate systems that “resonate with” changes in Earth’s orbit around the sun, and over millions of years the internal climate cycles evolved a huge amount while the changes in Earth’s orbit around the sun evolved very little.

    This was written: “As important as the Antarctic Ice Sheet is—it’s responsible for close to 17 meters of sea level rise since the last glacial maximum. (That cannot be a known fact, it is another guess by people who are paid to scare everyone)
    Antarctic Ice Core Records show that ice accumulation increased as warming occurred out of the last ice age, since twenty thousand years ago. Ice Core Records “PROVE” that most of the ice on Antarctica was accumulated in warmest times!

    This was written: “The warm water eats at the edges of the ice sheet and causes the ice to flow faster, and that response reaches deep into the heart of the ice sheet.”
    The warm water at the edges of the ice sheet floats away the floating ice shelves that break away and then the warm water promotes evaporation and snowfall that now falls on the old ice on the land and not on ice shelves that are already floating. AGAIN, ice core records PROVE that ice accumulation is most in the warmest times. The sequestered ice on land flows faster when it is deeper and heavier and it flows slower when it is less deep and lighter. The flow of ice over land slows it down, the floating of ice shelves does not, cannot push back, if one breaks off, it just floats away, it would not float away if it was pushing back. They do not use common sense; they use their billions of dollars they are paid to scare people. If they write stories that are not frightening, they lose their jobs and grant money.

    This was written: These climate oscillations are causing changes in ice sheet behavior
    Yes, data shows warmer times increase ice accumulation and that extra weight does increase ice flow rates, data shows colder times have less ice accumulation and ice depletion does slow the ice flow rates.
    This was written: Tulaczyk said the findings do show that the ice sheet can retreat during warm periods and then recover during subsequent cooling. “In the context of the threshold question—is the ice sheet sitting on a threshold beyond which there would be runaway melting and it will all go—that’s not what I see here,” he said. “The ice is sensitive to these short-term fluctuations, but the magnitude of ice loss is small enough that it can recover with cooling.”

    Ice Core Records have documented the “actual facts”, ice accumulation is more in warmer times which makes the sequestered ice on land grow in volume and weight. The heavier ice flows faster and spreads and causes colder times with growing ice shelves and then sea ice. The ice shelves and sea ice prevent evaporation and snowfall on the old ice, any snowfall is then on the floating sea ice and ice shelves. The sequestered ice on land flows and thins and depletes until the flow rate reduces. This allows the warming as less ice is pushed into the ocean, the sea ice is thawed, and the ice shelves break off and float away and the resulting repeating warm period rebuilds the sequestered ice on land again.

    The article ends with a link to a new story:
    “New study shows retreat of East Antarctic ice sheet during previous warm periods”
    https://phys.org/news/2020-07-retreat-east-antarctic-ice-sheet.html

    Of course, they have no clue that the previous warm periods were causes by cold periods with not enough evaporation and snowfall on the old ice sheets to maintain the ice volume and weight and flow rate.
    The retreat of the ice sheets causes the warm periods, which are necessary to replenish the ice.
    At least they get the correlation, but they have no clue if the chicken or the egg was first.
    Then again, they get paid billions if they say the ice retreat was caused by warming and they get paid nothing, get fired, if they admit that it is a natural self-correcting cycle.

  5. Ice Core Records PROVE, over and over, sequestered ice on land accumulated most in warmest times and cold times followed.

    Ice Core Records PROVE, over and over, sequestered ice on land accumulated least in coldest times and warm times followed.

    It did not snow on polar land, it did not snow on polar sequestered ice, enough to maintain the ice volumes, while the polar oceans were covered with ice shelves and sea ice. Colder times does not cause the ice to grow, colder times does not cause ice to advance and spread.

    COLDER AND WARMER TIMES ARE RESULTS OF ICE EXTENT, NOT CAUSES.

  6. JB says:

    “We know the last 20,000 years pretty well,”

    Yah, uh huh. What you “know” is the geologic record, such as it is. What you think you know about that is a figment of your speculations.

  7. oldbrew says:

    “We know the last 20,000 years pretty well”

    So what’s the ratio of natural warming in the Antarctic to (supposedly) non-natural, and what data would that be based on?

  8. Gamecock says:

    ‘We know’

    The first thermometer was planted on Antarctica AFTER 1900.

    Each weather station in Antarctica TODAY represents ~100,000 square miles.

    Satellite temperature measurement doesn’t work below 60°S.

    We not only don’t know ‘the last 20,000 years pretty well,’ our knowledge of TODAY is quite limited.

  9. Paul Vaughan says:

    CO[www]$play: “WhoaMIT˚˚disagree?” -Eurythmic$Penso11 western math “education” vs. ll+in=guiSST˚UK pageantri

    If westerners all had Chinese or Indian-level math & computer science education we’d have more than linguistic pageantry no doubt.

    “$we eat dr. EAM$
    [Earth Angle[˚the0˚terre] Moment um….]
    R MAID” weather˚ca the0 ll˚˚K pro˚T˚est ai n’t

  10. Phoenix44 says:

    Everywhere they look they find evidence of changing climate and natural variability except in the last 150 years.

    At what point does the edifice collapse?

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