“We May Have Lost Control”: The Melting Ice Sheets and What Happens Next
Scientists now believe significant melting of the ice sheets is inevitable. What does this mean for everyday life and the planet?
You would be forgiven for gasping in wonder if you visit the Earth’s polar regions. Here you’ll find some of the planet’s last belts of untouched wilderness: vast landscapes of snow and ice bathed in ethereal light; humpback whales and leopard seals cutting through Prussian-blue seas; and picture-perfect polar bears leading their cubs across the sea ice. It’s also where you’ll encounter Earth’s two remaining ice sheets: the Greenland ice sheet (GIS), sitting below the North Pole, and the Antarctic ice sheet (AIS), wrapped around the South Pole. Together, they play a crucial role in regulating the climate: they stabilize sea levels (by storing 99% of Earth’s freshwater), moderate surface temperatures (by reflecting over 80% of solar radiation back into space) and recirculate nutrient-rich water that sustains marine life (via the Atlantic’s ocean currents).
But there’s another reason to gasp — in horror. That’s because these ice sheets are melting before our eyes. Since 1901, they’ve lost 49,000 gigatons of ice — enough to cover the continental United States in an ice sheet 22 feet high (7 meters). In fact, the Arctic is warming four times faster, and the Antarctic three times faster, than the global average. Last July, the Antarctic hit 28°C above expected levels. If the ice sheets melt completely, they would raise the global sea level by a stunning 65 meters. It’s estimated that for every centimeter of sea level rise, around six million people globally are exposed to coastal flooding — tens of meters, then, would threaten our civilization.
When it comes to the West Antarctic ice sheet (WAIS), the most vulnerable part of the AIS, Kaitlin Naughten, lead author of a 2023 study published in Nature, sounded the alarm:
“It appears we may have lost control of the West Antarctic ice shelf melting over the 21st century. West Antarctic ice shelf melting is one impact of climate change that we’re probably just going to have to adapt to, and that very likely means some amount of sea level rise we cannot avoid.”
These statements should concern us deeply. If significant parts of the ice sheets melt, Earth may experience conditions not witnessed since the last glacial period 100,000 years ago. How will this affect our everyday life? What changes will it bring to our cities, our economies, our geopolitics, and the ecosystems and species that depend on the polar regions? Can we stop the melting or reverse it? Most crucially, how much time do we have to act or prepare for this new normal? The answers aren’t always clear or straightforward, but one thing is certain — the ice sheets, like all Earth systems, are subject to tipping points we dare not cross.
Earth System Tipping Points
One of the reigning concepts in climate science is tipping points — critical thresholds believed to exist in every Earth system including the cryosphere (Earth’s frozen regions) where the ice sheets sit. If you’ve ever leaned back too far in a chair and lost your balance, you intuitively understand how a tipping point works. Past a certain angle, all it takes is a gentle nudge in the wrong direction to send you hurtling backwards; but if you catch yourself in time, it’s easy to return to a stable position.
When it comes to the climate, the International Panel on Climate Change defines a tipping point as “a critical threshold beyond which a system reorganizes, often abruptly and/or irreversibly.” And that’s the rub: unlike a chair that you can prop back up, it’s difficult, if not impossible, to reset a planetary system that’s tipped. So far, scientists have identified 25 planet Earth-system tipping points, of which five are believed to be near critical thresholds including the GIS and the WAIS. This makes the ice sheets canaries in the coalmine for climate change, and we ought to pay close attention.
Crucially, the window for corrective action may still be open for the ice sheets (excluding perhaps the WAIS ice shelf), although probably not for long. Already, global temperatures breached 1.5C above pre-industrial levels in 2024, the warmest year since records began in 1850. Granted this was boosted by a warming El Niño event, but dare we push our luck further? Some scientists worry that 1.5C already puts us at risk of losing not just the ice sheets but triggering a cascade effect of multiple Earth system tipping points that would be extremely challenging to manage.
The Melting Ice Sheets
Ice sheets are continental-sized slabs of ice, the product of accumulated snow that’s hardened and compressed into layers over millennia. They’re dome-shaped near the center, slope downward near the edges, and slide slowly under their own weight. Where the ice sheets meet the sea, they can extend over the water and float as an ice shelf; over time, an ice shelf can break off into icebergs (through so-called calving events), such as the iceberg from the Jakobshavn glacier that sank the Titanic.
Up until the start of the twentieth century, the Greenland Ice Sheet (GIS) is believed to have been in a state of balance: it gained mass from snowfall at roughly the same rate it lost mass from surface melting and calving. Then it started shrinking — at first slowly and then at an accelerated pace beginning in the 1980s. Since then, the GIS has been losing mass rapidly, contributing 15mm to sea level rise (see chart). This inflection point in the Anthropocene isn’t surprising, as it coincides with the rapid rise in global temperatures caused by carbon emissions.
Contributing to the accelerated rate of melting are feedback effects. The most relevant for the GIS include melt-elevation feedback, a self-reinforcing cycle whereby higher temperatures melt the ice and lower its elevation, exposing it to warmer air that induces further melting. The other key dynamic impacting the GIS is melt-albedo feedback, whereby higher temperatures melt the ice to reveal darker surfaces (such as ocean water or rocky terrain) that absorb more solar radiation and cause more melting.
Scientists estimate that the thermal tipping point of the GIS is between 0.8 to 3.0C above pre-industrial levels. A wide range, to be sure, but highly concerning, since in 2024 average surface temperatures globally reached 1.5C of warming. It’s therefore possible that we have already crossed the tipping point and that the GIS is on an irreversible path to becoming ice-free, although this won’t be knowable for decades. The graph below isn’t a projection — it shows what has already happened.
Like the GIS, the Antarctic Ice Sheet (AIS) entered a period of accelerated decline in the 1980s. To date, the AIS has contributed nearly 14mm to sea level rise, only slightly less than the GIS (see chart). However, the AIS differs in several important ways from its northern counterpart. For starters, it’s nine times the size of the GIS, covering 5.4 million square miles (compared to 656,000 square miles). It stores far more freshwater, so its collapse would be felt much more widely. Luckily, air temperatures are cooler in the Antarctic than at northern latitudes, limiting surface melt. However, the AIS faces a different kind of threat: warming ocean water that melts the ice shelf. The WAIS is particularly vulnerable to this phenomenon, which is why it’s losing mass faster than the rest of the ice sheet.
The AIS is also susceptible to accelerated mass loss from feedback effects. The key one is marine ice sheet instability, which occurs because the WAIS sits on a sloping bedrock that allows warm water underneath the ice shelf, weakening it and producing icebergs that cause it to retreat into even deeper water. The other major feedback effect is marine ice cliff instability, which occurs when the collapse of an ice cliff (the edge of an ice shelf) reveals an even taller ice cliff that is more likely to collapse in the future.
Some of the biggest calving events in polar history have occurred in the WAIS, such as the 2,200 square mile A-68 Iceberg that detached in 2017. However, a 2024 study suggests that small calving events, not spectacular ones, are driving most of the AIS’s decline. Lead author and University of Florida professor Emma MacKie said:
“Our results suggest that the primary threat to our ice shelves is ‘death by a thousand cuts’ via small calving events, rather than catastrophic extremes.”
Consequences of the Great Melt
Perhaps the most discussed impact of the melting ice sheets is coastal flooding driven by sea level rise. The Intergovernmental Panel on Climate Change expects an increase of up to one meter by 2100. This would put 800 million people at risk by 2050, not to mention trillions of dollars of real estate and infrastructure in cities like Miami, Amsterdam, Bangkok, Jakarta, Manila, and Shanghai. In the case of low-lying Pacific island nations, such as the Maldives, Tuvalu, and Kiribati, the rising water poses an existential risk. UN Secretary General António Guterres has warned that inaction will result in the “mass exodus of entire populations on a biblical scale.” Vulnerable populations like the Guna in Panama have already resettled en masse, and these early climate refugees won’t be the last.
The disappearing ice sheets also threaten to destabilize ecosystems and endanger the species that inhabit them. Melting polar ice introduces sediment particles into the ocean that harm marine organisms like krill, a keystone species that forms the basis of the Antarctic food chain. Krill are also likely to suffer from reduced availability of algae, which grows underneath increasingly scarce sea ice. Some species even face the risk of extinction, such as the emperor penguin, whose chicks are born on sea ice and die when it breaks before they grow waterproof feathers. Upsetting the polar regions’ delicate balance will also impact walruses, seals, polar bears, arctic foxes, narwhals, whales, orcas, seabirds, and other species.
Below the waves, the melting ice sheets will weaken the AMOC system of ocean currents that regulates global temperature and re-distributes nutrients. When functioning normally, the AMOC sends warm water from the tropics to the North Atlantic, where it cools and sinks before returning south in a continuous loop. However, as the ice sheets melt, the ocean’s salinity and density falls, preventing the AMOC from sinking to the correct depth for its southward journey. The result is a slower AMOC (perhaps 15% weaker than 1950), higher sea levels in the Atlantic, and erratic temperatures globally including the risk of drastic cooling in Northern Europe. Some scientists even worry that the AMOC may collapse completely by mid-century, amplifying these effects.
The impact of continued melting will also affect global trade — with some positive surprises. As the Arctic’s navigability improves, shorter routes for ships will become viable, potentially lowering prices of imports and reducing the shipping industry’s carbon footprint by 24%. China’s dream of a Polar Silk Road may become a reality, enabling ships to shave off two weeks from their journey between Shanghai and Rotterdam while ending reliance on the Suez canal. A related economic boon involves rare earth metals in the GIS, which will become more accessible and likely trigger a mineral “gold rush.”
These events are sure to heat up geopolitical rivalries among the United State, Russia, and China (despite not being an Arctic nation). President Donald Trump has already made repeated attempts to buy Greenland on international security grounds. Moreover, the melting of the GIS will open up a vulnerable northern flank for the United States, which will have to contend with a greater threat from Russia’s Northern fleet.
What’s Next?
We’re tempting fate when it comes to the ice sheets — something the Maldives government tried to signal when it hosted a symbolic underwater cabinet meeting in 2009. The risk of the ice sheets entering a period of irreversible decline is terrifyingly real. According to the United Nations, we’re on track for 2.6 to 3.1C of warming above pre-industrial levels by 2100, which will put us in the upper range of the ice sheets’ tipping point. The silver lining is that it will take centuries, if not millennia, for the ice sheets to completely disappear — and we may even get a second chance at reversing their collapse if we reduce temperatures quickly enough. Still, this isn’t much consolation to countries that will face catastrophic flooding this century.
On the technology front, there’s no shortage of ideas for saving the polar regions. Drawing inspiration from ice rinks, one proposed solution involves deploying underwater drones to drill holes beneath the ice sheets and pumping ocean water to the surface where it freezes into ice. The Seabed Curtain Project, another approach, contemplates lowering a 100 kilometer underwater curtain in the warming Amundsen sea to protect the WAIS. Another concept involves coating thousands of square miles of surface snow and ice in reflective glass micro-spheres. Whether any of these ideas are viable remains to be seen, but even in the best case they are years away from implementation.
At the diplomatic level, the cryosphere and polar regions have started to receive greater attention from world governments in specialized forums. In November 2023, President Macron hosted the One Planet — Polar Summit in Paris, which saw countries make commitments to stop melting the ice sheets. Another initiative, Ambition on Melting Ice, founded in 2022 with Iceland and Chile as co-chairs, shares similar goals as the Polar Summit and is looking to expand its membership.
Perhaps most promising are positive social tipping points that can offset negative ones from nature. For example, if electric vehicles or renewable energy sources become attractive enough, entire cities, countries, and regions may shift to electric cars and 100% renewable energy. Seven countries have already achieved the latter, and the tipping point dynamics appear favorable for more to join their ranks.
But even if we can’t stop the ice sheets from melting, we can take steps to slow their retreat and make our societies more resilient, sparing millions of people from flooding, food shortages, and extreme weather. The Paris Climate Agreement picked 1.5C as a critical threshold for good reason—to reduce the risk of triggering early climate tipping points. We shouldn’t squander the opportunity to act now to bend the emissions curve and climate-proof our communities. At stake is not only humanity’s future but the survival of breathtaking landscapes that have existed for millions of years and wildlife found nowhere else on Earth.
