Melting of the Antarctic Ice Sheet Could Cause 5-Meter Rise in Sea Levels by the End of the Millennium

Simulated Mass Loss of the Antarctic Ice Sheet From 1990 Until 3000

Simulated mass loss of the Antarctic ice sheet from 1990 until 3000 expressed as sea-level contribution: Fourteen experiments for the unabated warming pathway (RCP8.5, SSP5-8.5), three experiments for the reduced emissions pathway (RCP2.6, SSP1-2.6), a historical run (‘hist’) for 1990–2015 and a control run for a constant 1995–2014 climate (‘ctrl_proj’) under which the ice sheet is essentially stable. The red and blue boxes to the right show the means for RCP8.5/SSP5-8.5 and RCP2.6/SSP1-2.6, respectively; the whiskers show the full ranges. Phase 1 is the original ISMIP6 period until 2100. Phases 2-4 are valid for RCP8.5/SSP5-8.5 and show an accelerated mass loss (phase 2), the main instability of the West Antarctic ice sheet (phase 3) and a final phase 4 where the mass loss levels out. Map-view plots below are ice surface elevation differences relative to 2015 (in meters; blue means thickening, red/brown means thinning) for the simulation forced by MIROC-ESM-CHEM/RCP8.5. Credit: Christopher Chambers et al. Journal of Glaciology. December 22, 2021

Scientists predict that continued global warming under current trends could lead to an elevation of the sea level by as much as five meters by the year 3000 CE.

One of the many effects of global warming is sea-level rise due to the melting and retreat of the Earth’s ice sheets and glaciers as well as other sources. As the sea level rises, large areas of densely populated coastal land could ultimately become uninhabitable without extensive coastal modification. It is therefore vital to understand the impact of different pathways of future climate change on changes in sea level caused by ice sheets and glaciers.

A team of researchers from Hokkaido University, The University of Tokyo and the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) explored the long-term perspective for the Antarctic ice sheet beyond the 21st century under global-warming conditions, assuming late 21st-century climatic conditions remain constant. Their models and conclusions were published in the Journal of Glaciology.

The Ice Sheet Model Intercomparison Project for the Coupled Model Intercomparison Project Phase 6 (ISMIP6) was a major international effort that used the latest generation of models to estimate the impact of global warming on the ice sheets of Antarctica and Greenland. The objective was to provide input for the recently published Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC). The contribution of the Antarctic ice sheet to sea-level rise by 2100 was assessed to be in the range between −7.8 and 30.0 centimeters (-3.1 to 11.6 inches)under unabated warming and between 0 and 3 centimeters (1.2 inches) under reduced emissions of greenhouse gases.

The team used the ice-sheet model SICOPOLIS (SImulation COde for POLythermal Ice Sheets) to extend the whole ISMIP6 ensemble of fourteen experiments for the unabated warming pathway and three for the reduced emissions pathway. Until the year 2100, the set-up was the same as in the original ISMIP6 experiments. For the time beyond 2100, it was assumed that the late 21st-century climatic conditions remain constant—no further climate trend was applied. The team analyzed the results of the simulations with respect to the total mass change of the ice sheet, regional changes in West Antarctica, East Antarctica, and the Antarctic Peninsula, and also the different contributors to mass change.

The simulations of mass loss of the Antarctic ice sheet show that, by the year 3000, the unabated warming pathway produces a sea-level equivalent (SLE) of as much as 1.5 to 5.4 meters (4.9 to 17.7 feet), while for the reduced emissions pathway the SLE would be only 0.13 to 0.32 meters (0.43 to 1.05 feet). The main reason for the decay under the unabated warming pathway is the collapse of the West Antarctic ice sheet, made possible by the fact that the West Antarctic ice sheet is grounded on a bed that is mostly well below sea level.

“This study demonstrates clearly that the impact of 21st-century climate change on the Antarctic ice sheet extends well beyond the 21st century itself, and the most severe consequences — multi-meter contribution to sea-level rise — will likely only be seen later,” says Dr. Christopher Chambers of Hokkaido University’s Institute of Low Temperature Science and lead author of the paper. “Future work will include basing simulations on more realistic future climate scenarios, as well as using other ice-sheet models to model the outcomes.”

Reference: “Mass loss of the Antarctic ice sheet until the year 3000 under a sustained late-21st-century climate” by Christopher Chambers, Ralf Greve, Takashi Obase, Fuyuki Saito and Ayako Abe-Ouchi, 22 December 2021, Journal of Glaciology.
DOI: 10.1017/jog.2021.124

This study was supported by Japan Society for the Promotion of Science (JSPS) KAKENHI (JP17H06323, JP17H06104) and Grant-in-Aid for Japan–France Integrated Action Program (SAKURA Program; JPJSBP120213203).

4 Comments on "Melting of the Antarctic Ice Sheet Could Cause 5-Meter Rise in Sea Levels by the End of the Millennium"

  1. “There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.” Mark Twain

    Indeed! Based on some data points at the nearly flat portion of the beginning of a sigmoidal curve, and then off into the wild blue yonder, we are expected to be stampeded into draconian restrictions that will have significant consequences for the world economy and life styles, let alone standard of living.

    These sigmoidal extrapolations are based on a fossil fuel consumption rate that results in radiative forcing (RCP 8.5) that some studies have shown to be improbable because there just isn’t enough fossil fuels to maintain ‘Business as Usual.’ Besides that, the warming that IS occurring seems to be a forcing more in line with RCP 2.6, yet without the mitigation strategies that are a part of the definition of the scenario.

    I would like to see more substantive evidence for what will happen over the next 1,000 years than conjecture based on modeling of questionable veracity.

    The world a thousand years ago would not have been able to comprehend what today is like. I think that implicit in the hand wringing of these researchers is the unexamined assumption that the technology 500 years from now will be no more advanced than currently, and that our descendants will be at the mercy of rising waters, and they wouldn’t have long ago solved the problems of controlled thermonuclear fusion.

  2. We are still in a 2.588-million-year ice age called the Quaternary Glaciation in a warm interglacial period that has happened every 100,000 years for a million years, before that it was every 41,000 years. The warm periods usually last about 10,000 years, this one named the Holocene has lasted 11,700 years.

    The Earth orbits the Sun in an orbit that also depends on Jupiter and Saturn. The Earth’s orbit cycles between a near circle and more of an ellipse over 100,000 years. When the Earth’s orbit gets more circular the Earth has more sunlight, which brings on an interglacial period and warms the Earth but still with permanent ice existing, like the present. The warming oceans release CO2 and that warms the Earth even more. That warm period lasts for about 10,000 years. Then the orbit of the Earth starts to get more elliptical, the Earth gets farther from the Sun on average, the Earth gets colder, the oceans absorb more CO2 from the atmosphere, and it gets even colder, which lasts about 90,000 years.

    Plants or the oceans capture all the CO2 including fossil-fuel CO2 in an average of 4 years according to the IPCC. The plants turn the CO2 into sugar. The animals eat the plants and turn the sugar back into CO2 and exhale it and that is mostly what our CO2 measurements reflect. We have more plants since there is more CO2 as the Earth gets closer to the Sun and burning fossil fuel contributes some, and more plants mean more animals as well. page 8 of the report, actual page 56, under 1.2 Carbon Dioxide “The turnover time of CO2 in the atmosphere, measured as the ratio of the content to the fluxes through it, is about 4 years”

    As an aside, we have 4.5 million people dying each year from moderately cold weather-related causes, mainly from strokes and heart attacks, while only about 500,000 are dying from heat-related causes and most of them were also from moderate heat. This apparently has been going on for eons but is proportional to the population although in earlier times the proportion was probably higher due to the more primitive technology.

    In this interglacial period, we are still about 6 degrees Celsius colder than the average of the last 500 million years when our biochemistry developed. Biological enzymes are often very sensitive to temperature possibly leading to the strokes and heart attacks.

    The sun is beginning a Grand Solar Minimum where it will produce less output for about 30 years which will reduce the temperature of the earth for that time.
    ‘Modern Grand Solar Minimum will lead to terrestrial cooling’

  3. Clyde Spencer said exactly what I wanted to say.

  4. I have lost count of how many “doomsday” scenarios I have survived in my life. Fossil fuels were supposed to be used up by now, sea levels were supposed to have completely drowned out our current coastlines by now, the Ozone layer was supposed to be non-existent, we are well past the doomsday dates laid out by Al Gore.

    I really just don’t care what predictions of doom that people today have for a millennium from now. They have used up their chances of alarming us all for what will happen this week. Now they’re working on the next 1,000 years. Realistically speaking, humans will face extinction no matter what we do today or what we do tomorrow. The scientific truth is, this plant cannot maintain life indefinably. It was never intended to. Life was here and went extinct 5 times before humans were even around. No one knows how long we were even meant to be here. So, another 1,000 years at most is just fine with me.

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