Antarctica is rising in response to change that started with end of last ice age

New study shows that the land underneath a part of West Antarctica is rising five times faster than expected as the ice melts, revealing a surprisingly soft Earth structure beneath the ice sheet.

How fast can Antarctica rise when the ice melts?

Earth finally free to rise after hundreds of thousands of years of ice suppression.

That, of course, is a provocative statement, however, from the point of view of the Earth, it is actually true. The Pine Island, Thwaites, Haynes, Smith and Kohler Glaciers, located in the Amundsen Sea Embayment of West Antarctica (see the map below), have been the stars of many alarming headlines regarding the accelerating pace of ice melt (also here and here), the possible collapse of the West Antarctic ice sheet, and sea level rise.

And it is true: The Amundsen Sea Embayment is one of the most important regions of the world in terms of ice melt.

These glaciers contain enough ice to cover an area the size of Denmark (43,000 square kilometres) with more than 11 kilometres of ice, which would raise the global sea level by 1.2 metres if it were to melt all at once.

That massive amount of ice has been burdening and pushing down on the surface of the Earth since the beginning of last ice age, 115,000 years ago. So, what can we expect as it melts and the pressure it exerts lifts?

Our new study published in Science has some answers.

 

Parts of West Antarctica are rising

At the peak of the last ice age, ice covered a much larger area of the Amundsen Sea Embayment than it does today, but it shrank to reach its modern configuration around 10,000 years ago, as shown in the figure below.

Since then, the glaciers in this region have been pretty much stable until about 200 years ago, when they started to melt and retreat. This happened slowly at first, but there has been a clear increase of ice loss since 2005.

Our study shows that the Earth surface, progressively relieved from the big burden of ice, is finally rising and it is doing so at an accelerating pace – up to 41 millimetres a year in 2014, which is between four and five times faster than expected.

GPS records the land rising

To see just how the land underneath the ice sheet is responding to recent ice loss, we studied data collected by high-precision GPS (Global Positioning System) instruments placed on remote rock outcrops in West Antarctica.

The Amundsen Sea Embayment (ASE) study area in West Antarctica, with the outline of Denmark shown for comparison. The top images show the location of the West Antarctic Ice Sheet (WAIS) and the ASE (top, image credit: NASA/Landsat Image Mosaic). The main image below is a close up of the ASE. (Hill shading is from the upcoming Reference Elevation Model of Antarctica product. DEMs produced using DigitalGlobe Inc. data. Data Compiled by Ian Howat (OSU), and the visualisation is by Paul Morin (PGC)). (Graphic: Author provided)

These GPS sensors work pretty much in the same way as the GPS in your phone or in your car, but they are much more precise and can measure movements of millimetres. Most importantly, the GPS sensors also measure vertical movements (such as rising bedrock) as well as horizontal movements.

In this way, they can actually measure the uplift of the land as the ice sheet melts.

team led by Professor Terry Wilson at Ohio State University (OSU), installed the sensors more than a decade ago—both GPS and seismic stations.

After what I would say was a heroic effort to install and maintain the network of sensors in one of the least accessible places on the planet, the team has been rewarded with incredibly valuable data, which tell an incredible story about the Earth.

Specifically, we discovered a very different Earth structure than was previously thought to exist underneath the ice sheet, which is driving the bedrock beneath the ice to rise faster than expected.

Video: West Antarctica is on the rise. (Video: ESA/Planetary Visions)

Why does the land rise when the ice melts?

To explain this, we need to understand the process by which the earth rises, known as glacial isostatic adjustment to give it its proper name.

A useful analogy is to imagine the structure of the Earth beneath Antarctica as a double-layer mattress with a springy, elastic layer at the top and a thick, memory foam underneath.

As the ice thins, the land immediately underneath the ice sheet quickly springs back in response to the loss of weight. This is like the springy layer at the top of your mattress, which springs back as you get out of bed. This immediate response is called elastic rebound.

Secondly, there is a delayed uplift as the mantle beneath the bedrock responds. This is analogous to the deeper memory foam layer of the mattress. Like the memory foam, the mantle ‘remembers’ its past load for a while before slowly creeping back to its original, unloaded shape.

If the mantle is stiff, this delayed uplift, occurs very slowly on time scales of millennia or more. This is what we see today in North America and in Scandinavia, where the land is still rising (by one centimetre per year) to ‘erase’ the footprint left by the vast ice sheets that once covered the northern hemisphere during the last ice age.

The Ice Sheet Grounding Line at the end of the last Ice Age; about 10,000 years ago; and today. (Credit: Jonathan Kingslake of Columbia University’s Lamont-Doherty Earth Observatory. Author Provided)

Conversely, if the mantle is soft and full of water, it will be far less viscous (i.e. less resistant to flow), and will respond much more rapidly to a loss of ice above. In this case, the mantle ‘memory’ will only persist for decades to centuries and uplift will mostly depend on recent ice loss. The more uplift we see, the softer the mantle underneath.

It is this fast surface response that we have now detected underneath Antarctica, suggesting the presence of a soft mantle.

A softer mantle than expected

A soft and warm mantle is typically found in very active tectonic areas at the edge of tectonic plates. And very fast uplift rates, like those recorded in our study, only occur where ice is also actively melting, such as Alaska (also here and here), Iceland (also here), and Patagonia.

Although the Amundsen Sea Embayment is not tectonically active, it does share some common features with these places, including the presence of volcanoes and rift systems. So, we expected to see a little bit of a delayed rebound (uplift) on top of the instantaneous elastic response. But what we found went beyond our wildest imagination.

With GPS, we measured (and continue to measure) an uplift rate up to five times faster than the elastic rebound, which means that the mantle is very soft.

This is 100 times less viscous than below North America, and 10 times less viscous than what we had expected.

Our results have a number of important implications for scientists to study further, such as improving our knowledge of the solid Earth response to the ice melting processes in Antarctica, which in turn is very important to understand the long-term sea level evolution of the ice age cycle.

But it is the implications for the very short-term contribution to sea level rise that caught many people’s attention, as rising bedrock could slow down ice retreat and perhaps even protect the ice sheet from collapse.

We have not yet investigated these implications and the processes involved are complex, but clarifying them will certainly improve the reliability of the future projections of sea level rise in the race against climate change. We will explore this in more detail in the next article.

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61 thoughts on “Antarctica is rising in response to change that started with end of last ice age

  1. That should all be a warning to go back and triple check the data and the calibrations like they do at LIGO and IceCube.

  2. “But it is the implications for the very short-term contribution to sea level rise that caught many people’s attention, as rising bedrock could slow down ice retreat and perhaps even protect the ice sheet from collapse. We have not yet investigated these implications and the processes involved are complex, ”

    In other words they don’t know what in hell is going on. Send more money.

    • Scientists have been studying glaciers for over 200 years and they are still clueless as to what is happening here? I thought the science was settled. Oh, only the Co2 science has been settled you say. Well note this. It is estimated that there is 1,350, 000, 000, 000, 000 grams of aerosols or 1,350,000,000 metric tons. Each particle is from .002 microns to 100 microns in size. Each particle is as different as snowflakes are and can carry dozens of elements in the periodic table as well as thousands of compounds. The chemical composition changes over time as does their behaviour in the atmosphere. Aerosols generally cause global cooling but soot can cause global warming according to NASA. We have very poor estimates of the aerosol cycle and an even poorer understanding of the actual range of effect that aerosols have on temperature and climate. So I ask you what is settled? Even the CO2 question isnt settled because there is no proven theory of how CO2 would act to raise temperatures. And we are being asked to spend trillions of dollars to limit CO2 becuse they say it is a pollutant!!!!!!!!!!!!!!!!!!!!!!!!!!.

      Toto has not pulled back the curtain yet on this gigantic fraud but Toto’s training is going well and we should see results soon.

  3. I wonder if enough geological investigation has been carried out in the barely accessible region to determine the length of the glaciers during warmer intervals of the Holocene, such as its Climatic Optimum (~5 Ka), the Egyptian (~4 Ka), Minoan (~3 Ka), Roman (~2 Ka) and Medieval (~1 Ka) Warm Periods.

  4. of course…it’s worse than we thought

    The land is rising…..and it’s compensating for more ice melting
    …and the sea floor is sinking
    the heat is hiding in the deep ocean
    …and Miami is under water

    Climate science…the only science where the facts are smart enough to hide

    • …of course…using this logic….every mountain would be sinking and incapable of rising

      Mt Everest would be a lake by now

  5. Well I hope that the mantle is not soft enough to revive Hapgood’s Crustal Displacement Hypothesis. 🙂

    • No, but the difference between “soft” and “stiff” mantle is pretty big. Rebound completed in 2,000 years on Iceland, Still going strong after 12,000 years in Scandinavia.
      Incidentally this makes any estimate of ice-loss based on gravity data (like GRACE) pretty meaningless since we have virtually no idea about the viscosity of the mantle in Antarctica, except along the coasts (no exposed rock to put GPS stations on inland).

      • Not just the GRACE data but also laser and radar surveys become meaningless when used to estimate ice thickness and accumulation rates. Much more ground based survey data is required to establish uplift rates across the continent, which will be a huge job and will take decades. And while isostatic rebound can be expected around the margins of the ice sheet, there is no reason for that to extend far inland where ice is still accumulating and the crust may be sinking.

        • Laser and radar surveys are much less sensitive to the isostatic problem since ice is much less dense than rock, so altitude changes of the ice surface are less affected by isostatic adjustment. Of course there are other problems, particularly that the density of snow varies geographically.

          And unfortunately ground surveys are impossible in most of Antarctica since there is no ground to survey, just ice. GPS stations must be on bedrock. And sinking crust affects the measurements just as much as rising, only with the opposite sign. Also there is a time delay. The ground under a thickening glacier can be rising, because it is still reacting to an earlier ice-loss that was greater than the current accumulation. Or the other way around, of course.

          • Laser and radar surveys measure the topographic surface directly. But if you can’t tell whether ice is being added or lost from the surface because the crust is moving, then it’s not possible to use the data for ice volume calculations.

            Perhaps someone can prove otherwise, but I don’t see why survey stations couldn’t be installed in stable ice to last at least a few years. It would have legs drilled a few metres into the ice and it might move laterally a bit, but I don’t see an alternative to get hard data. Geophysics is all very well, but it has to be ground truthed somehow.

          • What good would a GPS station on ice be? It is the bedrock you need to measure to determine the isostatic adjustment. And yes, it would move sidewise, and vertically. There is no such thing as “stable ice”. The definition of a glacier is that it consists of moving ice.

            And because of the greater density of rock relative to ice the isostatic movement of bedrock affects the results of a direct measuremenr of the ice height much much less than a gravity measurement.

            And incidentally a simultaneous measurement of gravity change and ice surface absolute altitude change over the same area and for a reasonably long time period would make it possible to separate the two factors unambiguously, though still with a considerable uncertainty due to variations in rock and snow/ice density and the very different definition of the two measurements. As yet it hasn’t happened, but GRACE-FO and Icesat 2 could theoretically do it.

  6. This just adds the WAIS to the list of regions recovering GIA wise from the LIA, and goes to show why virtually all glaciologists take a global LIA for granted. As always, the consensus is that the Hockey Stick is junk science. –AGF

  7. This is hardly world-shaking science. West Antarctica is known to be a tectonically very active, rifted area. The only similar area we have good data for, Iceland, also exhibited exceptionally fast isostatic rebound, reaching equilibrium less than 2000 years after the end of the ice age.
    Now the interesting part is only obliquely touched upon: “…rising bedrock could slow down ice retreat and perhaps even protect the ice sheet from collapse”.

    Now rapid ice-sheet collapse is itself a theoretical construct. It has never been shown to have actually happened in the real world. However even theoretically it can only happen under very special circumstances:

    1. Water depth at the ice front must be >90% of the thickness of the ice.
    2. The ground under the ice must slope monotonically downward up-glacier, and the slope must be greater than the rate the thickness of the glacier increases.
    3. There must be no rock thresholds or pinning-points under the glacier.

    A fast isostatic rebound will of course decrease the likelihood of any of these three conditions occurring.

    • How did the mass of its ice per sq mi compare with that over Scandinavia and Britain?

      Its own density must differ from that of continental crust, as well, being made out of mid-ocean ridge erupted volcanic material.

      • The Density of glacier ice is about 0.91. The density of typical crustal rocks are about 2.5-3.5, so as an average 3 meters of ice is equal in weight to 1 meter of rock. The ice-cap over Iceland was fairly thin, perhaps 500-1500 meters (there were apparently a number of nunataks).

        • Tty,

          Thanks. I suspected that Iceland’s ice cap might not have been as massive as over Scandinavia or even Britain.

          Hvannadalshnúkur, highest point on Iceland, rises to 2110 m.

  8. “How fast can Antarctica rise when the ice melts?”

    “Since then, the glaciers in this region have been pretty much stable until about 200 years ago, when they started to melt and retreat. This happened slowly at first, but there has been a clear increase of ice loss since 2005.”

    “…..up to 41 millimetres a year in 2014, which is between four and five times faster than expected.”

    The 4cm per year is stable for such a huge continental glacier. These changes could have easily occurred over 200 years ago.

    Ice melting and ice loss has nothing to do with temperatures over land where it has suppose to have risen for past 200 years.

    Below was the warmest Summer month last season closest to the West Antarctica coast.

    Year/Month Observation Normal
    Mean Temp.[degC] Max. Temp.(Monthly Mean)[degC] Min. Temp.(Monthly Mean)[degC]
    2018-01 -15.5 -12.5 -18.8

    The warmest Summer month last season on the coast off Ross Sea.

    Year/Month Observation Normal
    Mean Temp.[degC] Max. Temp.(Monthly Mean)[degC] Min. Temp.(Monthly Mean)[degC]
    2018-01 -7.2 -4.4 -9.9

    It is far too cold for ice to melt here in Summer around West Antarctica without volcanic activity, so any ice loss/ice melt are down to something else usually exposed warmer ocean water many miles away from the coasts or a change in the trend of precipitation totals.

    • Very nearly all ice-loss in Antarctica is due to calving, although there is some subglacial melting this is quite minor. And there is actually some surface “melting” even below freezing through sublimation, i e ice turning directly into water vapour without first becoming liquid. This is also minor, though noticeable in e. g. blue-ice areas.

    • Actually most penguins aren’t true arctic birds. Out of 16 species only two occur exclusively in Antarctica: Adelie and Emperor. Three more, though mostly further north also breed at the northern tip of the Antarctic Peninsula: Gentoo, Chinstrap and Macaroni. The other eleven don’t occur in Antarctica at all. One, the Galapagos penguin breeds on the Equator.

  9. Ah yes, when the sea shore advances then the “sea level is rising” and when the sea shore retreats then the “land is upthrusting”. No wonder the sea level is rising on average, duh.

    • Both can happen quite independently of any change in level of either land or sea, or they can happen as a result of the sea rising/sinking or the land rising/sinking and any combination thereof. Shoreline displacement is a complicated process.

    • Ice loss is (mostly) not happening either at the base or the surface, but rather by calving at the edges, though this causes a drawdown of the thickness since the ice flows plastically, though slowly.

  10. Have they ruled out volcanic activity as a possible cause for some of the land rise, as well as some of the ice melt, in West Antarctica? I’ve never understood why ‘global’ climate change would selectively pick on West Antarctica but leave East Antarctica, where ice is increasing, alone.

    • It seems as though “Global warming” tends to be most severe where researchers are found. Also where grants are dispersed.

      • It seems as though “Global warming” tends to be most severe where researchers are found. Also where grants are dispersed.

        It seems as though “Global warming” tends to be most severe where when researchers are found. Also where before, during, and after grants are dispersed.

    • East and West Antarctica have very different topography and considerably different climate. And are about as different as two landmasses can be tectonically.

  11. As I understand things West Antartica is a part of the chain of volcanos starting at the West coat of South America and ending at Mt. Erebus at the South Pole. So same melting would be expected. But the rest of Antarctica is gaining ice cover. So of course the Western end is rising.

    MJE

    • Nope. The last glacial period commenced at end of the Eemian interglacial c. 115,000 years ago and continued to the end of the Younger Dryas about 11,700 years ago. Things have warmed up since them a Little Ice Age and similar blips notwithstanding.

      • Umm…noo. The “climatic optimum”, as it was known before good weather became dangerous, occurred quite early in the Holocene, 8,000-10,000 years ago. Since then temperatures have been going slowly down MWP and similar blips notwithstanding.

    • Face the Prime Meridian, towards Greenwich. East is to your right, towards Asia, West is to your left.

      [Rather: Face North at the Prime Meridian, in Greenwich … .mod]

  12. Who cares if the West Antarctic Peninsula, a small fraction of the continent, is experiencing Glacial Isostatic Adjustment, or more properly Glacial Isostatic Rebound? Has nothing to do with the amount of heat in the atmosphere of the Earth.

    The amount of heat in the atmosphere of the Earth is controlled by two phenomena, the Albedo of the Earth which changes minute by minute, and the amount of heat trapped in the atmosphere by the height at which the atmosphere is freely radiating to space. A little more CO2 raises the altitude at which the atmosphere can freely radiate to space, thus lowering the temperature at which the ENTIRE ATMOSPHERE radiates to space, thus lowering the radiative heat transfer to space. A little. No one can calculate this effect.

    CO2 absorbs, and up there re-radiates half up and half down, radiation which originates from atmospheric molecules, ALL OF THEM, at -80 C. This is the temp at 8 or 9 miles up, or so, maybe 8 or 9 kilometers, cannot remember. All of the Infrared from the surface is absorbed and thermalized by CO2 within 10 meters of the surface, so this effect has been Saturated for millenia. Do not listen to propaganda involving Pressure Broadening or the Shoulders of the infrared spectrum of CO2 absorption, these are trivial effects, an attempt to intimidate non-technically educated people.

    So much mis-information in this controversy.

    • And, the Albedo of the Earth is not so easy to measure. Reflections from Moonshine at the New Moon are probably the best way, but no consistent results are found. No satellite can measure this because no satellite can see the entire reflection from the entire Earth.

      Man, the BS from these so-called “Climate Scientists” goes on and on….

      • A satellite at one of the Lagrangian points could easily measure the albedo each 24 hours but nobody seems interested.

    • Isostatic adjustment is by no means restricted to the Antarctic peninsula. Look at the image below. The little round dots show GPS stations, and their color indicate how much GIA there is at that place. The background color shows four different GIA models. It is these models that are used to calculate actual ice loss. If the models were good the dots and the background color would be identical. As you can see they are all different and all waaaay off, and the most used model ICE-5G, is by far the worst.

      https://academic.oup.com/view-large/figure/9138524/190-3-1464-fig014.gif

      The reason ICE-5G is so popular despite the bad fit might possibly be that Antarctic ice loss comes out highest by using it….

  13. After some decades working in geological sciences, I cannot recall many occasions when we knew all of the parameters, variables, inputs, or whatever the name, that we would like to know about when arriving at deductions leading to a decision on whether to invest more funds, or to cease. Pure geology has many unknowns. For example, there is no general theory of metalliferous ore formation, for example, beyond geologists attaching names to loose processes with which their minds are most comfortable. The same with petrogenesis. The problem of not being able to take direct samples from deeper than say 10 km below the surface means a lack of understanding of process that happen deeper than that, except when the processes are inferred from rocks that have been uplifted, with attendent time delay and uncertainty of what might have happened in that time.
    In the present case of the uplift rate on the edge of the Antarctic, it is more than an accident of nature that the most accessible rocks on which to mount GPS gear to measure uplift are those on the edge of the continent. There is a fundamental geologic question or two, in the light of my first paragraph, that could be asked.
    1. Why does the continent have the boundaries that it does?
    2. Is this because the marginal geology is different to the internal geology in fundamental ways that disturb our ability to extrapolate from margin to interior?
    When fundamental questions like this can be asked, it should be no surprise that time and again we find that the science is not settled.
    The bigger surprise is why those who made the ‘science is settled’ statements have not apologised for their ignorance by now and withdrawn their silly posturing.

    • 1. It rifted away from the rest of Gondwana that way. And of course nobody knows why rifts occur in particular places, except that there seems to be a tendency for the continents to split at or near previous sutures.

      2. Unlikely for East Antarctica which seems to be mostly a precambrian shield rather similar to Australia (which split off from it), though the origins of the Gamburtsev Mountains are quite enigmatic. West Antarctica is very different with a quite uniquely huge Rift Valley through the middle and is really more an archipelago than a continent.

      So, yes, extrapolating geophysical parameters far from exposed bedrock is a decidedly shaky proposition, particularly in West Antarctica.

  14. So now we’re in a race against Climate Change? What happens if we win? Will the Climate stop changing from then on? Ho hum!

  15. Perhaps that has something to do with the 90 new volcanoes discovered under the ice in this region, discovered a little while back, the most dense volcano field on land on Earth? Enough magma to melt a Gigatonne of ice pa. That will cause a bit of thawing at glacial bases and assist separation of ice shelves, etc. Tierra del Fuego is a clue for Spanish speakers.

    West Antarctica is not representative of the Antarctic geology and climate in general, which I recall is betting colder and accumulating ice? Not sure about that.

    https://www.geos.ed.ac.uk/homes/rbingha2/48_2017_Vries.pdf

    Given ice is not unloading much then this is magmatic pressure from the tectonic rim of the Antarctic Plate? Think Rift Valley/Jellystone. Land usually rises as ice unloads the supporting structures as it melts BTW, so not a given cause if the ice isn’t melting. If unloaded, the volcanoes will also become much more active, as Huybers and Langmuir have described elsewhere as a characteristic of the later part of the last 7Ka interglacial warming (2-6 times more active), still rising in many formerly ice covered but structurally rigid areas.

    But only for a few thousand more years, as the ice will be back, interglacials being a short term warming perturbation to stable long term ice age climate, on the earlier 2.5 Million year series of 41Ka Milankovitch obliquity cycle driven ice ages and for the last 1 Million years of the 100Ka eccentricity Milankovitch cycles. Nothing to see here except same old same old, really. Check the Vostok core data (Petit et al) or Ellis and Palmer for recent details of key variables over the last 0.5 Million years or so.

  16. I’m sure that with the right combination of tax increases, wealth transfers, and new regulations we can stop the uplift.

  17. Land is rising.
    Ice is melting, claimed; as too much research conducted in this area is agenda driven.

    These characters have measured land rise; so the land must be springing back from loss of ice…

    Another group that jumps from association to loose correlation and then immediately to causation.

    According to them, an annual 3 foot change in ice height results in massive land rise…

    Without ever identifying what they believe the original height/weight of melting glaciers.
    Without ever identifying how much of the land rise is due to solely tectonic or volcanic sources.

    It’s all confirmation bias.
    Decide result, use data to prove result, ignore other possibilities.

  18. so antarctica is getting bigger because ice is increasing so they wanna put out this bullshit story that it’s just the land underneath that is ‘rising’.

    [The mods have it on good authority that there is no BS on Antarctica.
    Penguin S? Yes. Bird S? Yes. People S? Yes.
    But no BS on Antarctica. .mod]

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