The West Antarctic Ice Sheet Approaches a Critical Point: An 800,000-Year Simulation Highlights Decisions in the "Coming Years" and a Warning for Japan

The West Antarctic Ice Sheet Approaches a Critical Point: An 800,000-Year Simulation Highlights Decisions in the "Coming Years" and a Warning for Japan

2025年06月03日 18:26

1. Why the "Next Few Years" Are Critical

A paper published in the academic journal Communications Earth & Environment on May 30, 2025, indicates that the West Antarctic Ice Sheet (WAIS) has "two stable states" and can hysteretically switch to a "collapse mode" with just a slight increase in sea temperature. Once the collapse begins, the outflow of ice continues self-reinforcingly, causing a global average sea level rise of about 4 meters. The team warns that this could occur with additional warming of just 0°C to 0.25°C.nature.com


2. Research Methodology—800,000 Years × Parallel Ice Sheet Model

The study, which also involved NORCE in Scandinavia and Northumbria University in the UK, is the first attempt to continuously calculate the glacial-interglacial cycles over 800,000 years using the Parallel Ice Sheet Model (PISM). The results showed a severe scenario that overturns previous understanding: "Even if sea temperatures drop by 1°C, natural recovery from the collapse state would take thousands of years." Because the ice sheet recovery cycle is extremely long compared to modern anthropogenic CO₂ emissions, once a critical point is exceeded, it can be considered "irreversible" on the scale of human history.researchportal.northumbria.ac.uk


3. Collapse Mechanism: "Bottom-Up Melting" from the Ocean

The WAIS is a "marine ice sheet" that largely rests on land below sea level. The main cause is "ocean-ice sheet interaction," where warm deep water enters behind the ice shelves and melts the bottom. This is called **Marine Ice Sheet Instability (MISI)**. When the ice shelves thin, the "brake" that restrains the ice sheet's advance is released, leading to an accelerating vicious cycle of outflow. Particularly, the Thwaites Glacier, known as the "Doomsday Glacier," could begin a large-scale collapse in the latter half of this century.nypost.com en.wikipedia.org


4. The Reality of a 4 m Sea Level Rise for Japan

The figure of 4 meters would expose low-lying areas such as most of Koto and Edogawa wards in Tokyo Bay, the Nagoya Port area, and the Kitakyushu coastal region to constant storm surge risks. Estimates based on Ministry of Land, Infrastructure, Transport and Tourism statistics suggest that about 22% of total asset value would enter long-term inundation zones, and additional infrastructure costs for strengthening coastal defenses and relocating ports could reach hundreds of trillions of yen. Unlike short-term impacts from storm surges and typhoons, constant water level rise would necessitate the relocation of urban functions themselves.


5. Reactions on Social Media—A Sense of Crisis and a "Call to Action"

Just days after the paper's release, the scientist account "@dorfman_p" tweeted, "We have almost no time left," garnering tens of thousands of views. The official account of the academic journal also shared the paper link, and reposts spread rapidly. Domestically, the climate NGO "Fridays For Future Japan" argued that "keeping the Paris Agreement's 1.5°C target is the only way," and related hashtags #WestAntarcticIceSheet and #DecarbonizeNow briefly trended.

6. "Heatwave Antarctica"—Recent Rapid Change Cases

In the winter of 2024 (Southern Hemisphere), an abnormal high temperature of over +10°C compared to the average hit East Antarctica, and the sea ice area recorded the lowest in observation history. In 2023, for the first time, temperatures exceeding 70°F (about 21°C) were recorded, causing multi-year ice to collapse rapidly, described as a "red alert." Such extreme phenomena are feared to hasten the MISI ignition point.theguardian.com en.wikipedia.org


7. Implications for Japan's Policy and Industry

Japan aims for carbon neutrality by 2050, but the research team emphasizes that "avoiding WAIS collapse will be extremely difficult unless global emissions are halved by 2035." While the spread of renewable energy is progressing, the current situation where plans for new coal-fired power plants and new chemical plants remain is a "sitting duck" scenario. The budget for sea level rise countermeasures by the Ministry of Land, Infrastructure, Transport and Tourism and the Ministry of the Environment remains in the scale of several hundred billion yen per year, with a large gap compared to future costs.


8. Technological Options—Negative Emissions and Ice Sheet Reinforcement

In the short term, emission reductions are essential, but as measures extending into future centuries, discussions are ongoing about (1) negative emission technologies like Bioenergy with Carbon Capture and Storage (BECCS), (2) Direct Air Capture (DAC), and (3) geoengineering such as constructing "iceberg barriers" for ice shelves. All of these are high in cost and risk and can only be used as a "last resort." Researchers argue that "postponement narrows options both technically and ethically."


9. Conclusion—The "Reiwa Decade" Determines the Next Millennium

The fate of the WAIS falls into the category of the most long-term and high-impact changes due to global warming. If a world exceeding 3°C becomes the norm, collapse is almost certain, forcing coastal civilizations, including Japan, to redesign under new geographical constraints. On the other hand, if emission reductions and natural regeneration are thoroughly pursued, there is still room to avoid the critical point. The "remaining carbon budget" we hold is also the "safety valve" for future ice sheets.


"Human dependence on fossil fuels is what shakes the ice sheet on a millennial scale in just a few decades. Only humanity can pull the lever to slow down immediately." — Co-author Julius Garbe (PIK)

Determination and action are the only ways to change the damage from the climate crisis from "irreversible" to "avoidable."


This article is based on "Nächste Jahre entscheidend für die Zukunft des westantarktischen Eisschilds."


References and Sources

  1. Sonnenseite.com "Nächste Jahre entscheidend für die Zukunft des westantarktischen Eisschilds" (2025-05-31) sonnenseite.com

  2. Chandler, D. M. et al. "Antarctic Ice Sheet tipping in the last 800,000 years warns of future ice loss." Communications Earth & Environment 6:420 (2025-05-30, Open Access Paper) nature.com

  3. Potsdam Institute for Climate Impact Research (PIK) Press Release "Stability inspection for West Antarctica: marine ice sheet not destabilized yet, but possibly on a tipping path" (2023-07-09) pik-potsdam.de

  4. NPR News. "New research on Thwaites Glacier could reshape sea-level rise projections." (2024-05-21) npr.org

  5. International Thwaites Glacier Collaboration. "Thwaites Glacier Facts." (Last accessed 2025-06-03) thwaitesglacier.org

  6. The Guardian. "Antarctic temperatures rise 10 °C above average in near-record heatwave." (2024-08-01) theguardian.com

  7. The Washington Post. "Scientists found the most intense heat wave ever recorded — 70 °F above normal in East Antarctica." (2023-09-23) washingtonpost.com

  8. Columbia Climate School News. "'Doomsday' Antarctic Glacier melting faster than expected, fueling calls for geoengineering." (2024-10-30) news.climate.columbia.edu

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