The vast ice sheets that cover Greenland and Antarctica have the potential to trigger catastrophic sea level rise as the climate warms.
But the ice-sheet models that scientists use to project future changes underestimate how fast sea levels are rising now and how much they have risen in the past.
This suggests the models are missing important processes driving ice-sheet retreat.
New research suggests that melting at grounding zones – where the ice transitions from sitting on land to floating on water – could be the missing piece of the puzzle.
And it is potentially a big piece. For example, when one study on the Thwaites glacier in west Antarctica included these processes, its projections of ice-sheet loss more than doubled.
In this guest post, we unpack the latest research on grounding-zone mechanisms and why they suggest that current global projections of sea level rise may be substantially underestimated.
Ice sheets are shrinking faster than models project
Scientists use ice-sheet models to project how fast – and by how much – the Earth’s ice sheets will shrink as global temperatures rise.
These models, developed by scientists at universities and national research institutes, represent physical real-world processes using sets of equations. By solving these equations, scientists gain understanding how the physical system will respond to different scenarios. There are around 20 ice sheet models in use around the world today.
The models capture what we know about how ice sheets flow and deform. Projections using these models suggest that ice sheets will contribute 10s of centimetres to sea level rise by the end of the century.
However, it increasingly looks like these models underestimate the true sensitivity of ice sheets to climate change.
First, we can look at sea level rise from ice sheets over the past 20-25 years. Over this period, we have detailed satellite observations to compare to model predictions.
The figure below shows the spread in projections from models (blue shading) for Greenland’s contribution to sea level rise compared to the satellite data (blue line). This spread is generated by a range of factors, such as how different models describe ice flow, how fine of a resolution they use to represent the real system and the initial state used for model runs. Sea levels are presented relative to 2015, as this was chosen as a benchmark year.
It is clear that the majority of models underestimated the rate of Greenland melt.
Next, we can consider whether models have succeeded in reproducing ice sheet loss from historical warm periods.
For example, proxy records, such as reconstructions of previous shorelines, indicate that during the Pliocene (5.3-2.6m years ago) sea levels were between six and 40 metres higher than today.
This extreme sea level rise would have required a substantial contribution from the world’s ice sheets. However, models are largely unable to reproduce these values, with almost all failing to even attain lower bounds.
Finally, from a different standpoint, we can ask how much climate forcing is required to reproduce current ice sheet retreat rates. Models of the west Antarctic ice sheet typically require ice shelves, which restrain the flow of grounded ice, to be melted very rapidly in order to reproduce current rates. However, recent observations of melting in these regions suggest it is in fact far smaller than models require.
Together, this evidence suggests that ice-sheet models are not entirely capturing what is going on: they should be more sensitive to changes in the climate than they currently are. Two recent papers have suggested that what happens in so-called “grounding zones” could be the missing piece of this puzzle.
Grounding zones
Ice sheets are not static; they spread out like a very thick liquid. The majority of ice in the world’s ice sheets sits on top of land, above sea level. As the ice spreads out and thins, it begins to float, transitioning into a floating ice shelf.
The boundary between ice on land and floating ice shelves – shown in the figure below – is known as the “grounding zone”.
The classical picture of grounding zones is as distinct boundaries between floating and grounded ice. It was previously thought that they migrate on annual-to-decadal timescales as ice sheets retreat and advance, and that little melting took place there.
Recently, however, a different picture has emerged, where grounding zones are actually highly dynamic regions.
In particular, two independent mechanisms – called “tidal intrusion” and “porous intrusion” – are thought to be taking place in grounding zones.
Both of these mechanisms are thought to allow relatively warm ocean water to rush under ice sheets, enabling vigorous melting to take place there.
Tidal intrusion
Antarctica has one of the largest tidal ranges in the world, with sea levels fluctuating by up to seven metres each day.
As the tide rises, water pressure under ice shelves increases, lifting the ice and creating a new cavity in the grounding zone. As a result, this newly formed cavity, which can be up to 15km long, is rapidly filled with ocean water.
When the tide falls, the reverse happens: the ice settles back down and water flushes out of the cavity. This cyclic process – named “tidal intrusion” – occurs up to twice per day, driving rapid flows of warm ocean water into and out of the grounding zone, where it can melt the ice from below.
The tidal opening and closing of grounding zone cavities can be observed using surface elevation and radar measurements from satellites. However, these observations – particularly in fast-changing regions – have typically been limited by how frequently the satellites pass over the same spot, which varies between weeks and months.
Recent research, published last month, has used a unique set of sub-daily satellite observations from the ICEYE constellation to show that tidal intrusion is widespread beneath Thwaites glacier.
This research indicates that warm water is able to intrude up to 6km beneath the Thwaites ice shelf during each high tide, where it could accelerate ice melt from below.
Thwaites – nicknamed the “doomsday glacier” – holds enough ice to raise global sea levels by up to 65cm and has long concerned scientists because of its rapid present retreat, potential for runaway ice loss and possibly important role as a keystone in the west Antarctic ice sheet.
This new research suggests that Thwaites may be even more vulnerable than previously thought.
Porous intrusion
Beneath ice sheets, there are networks of channels and tunnels, as well as porous sediments, through which meltwater from the bottom of ice sheets flows.
In grounding zones, this cold, fresh meltwater meets relatively warm, salty ocean water. The ocean water is denser, allowing it to intrude beneath the meltwater and into the grounding zone. This process is called “porous intrusion”.
Recent modelling has suggested that ocean water can intrude kilometres beneath ice sheets via this mechanism.
However, previous research has not considered how the geometry of these regions change in response to melting. In our new study, published in Nature Geoscience, we show that, when this effect is considered, the porous intrusion mechanism can be far more powerful.
In particular, we show that these systems display a tipping-point like behaviour, in which a small change in ocean temperatures can lead to a dramatic change in the distance that warm water is able to intrude through grounding zones.
We also show that the porous intrusion mechanism is not only applicable to ice shelves exposed to warm water or with high melt rates at a glacier’s base, such as Thwaites, but can also influence cold water ice shelves.
The susceptibility of a glacier to porous intrusion is linked to the slope of the seabed and how quickly melted ice is replaced. This is illustrated in the figure below; glaciers in the purple-shaded area are the most susceptible.
In fact, Thwaites appears to be relatively unsusceptible to porous intrusion – despite being highly vulnerable to tidal intrusion – because it flows very rapidly and ice is replaced very quickly.
Other ice shelves, such as the Ross and Ronne ice shelves, which sit in relatively cold water may, surprisingly, be amongst the most susceptible ice shelves.
Are grounding zones the missing piece?
The majority of ice-sheet models still represent grounding zones as a distinct transition between grounded and floating ice, with no melting there from either tidal or porous intrusion.
The only models able to attain anything resembling sea level rise values during past warm periods have included a grounding-zone melting mechanism or a similar mechanism that boosts their sensitivity to climate change.
These same models have also received much attention for their pessimistic future sea level rise projections. Capturing the past requires an increased sensitivity to climatic change, meaning that they predict much higher sea level rise in future.
So, grounding zone intrusion and melting might be the missing piece to reconcile observed and modelled sea level rise.
While scientists have yet to run model simulations with grounding-zone melting included for the whole of Antarctica, studies focusing on specific regions of the continent’s ice sheets project up to twice as much sea level rise.
Current global projections of sea level rise also do not include grounding-zone melting. This means that these projections – including those that inform the reports of the Intergovernmental Panel on Climate Change (IPCC) – may be substantial underestimates.
Ice-sheet models have “known unknowns” – things we know that we do not know perfectly, but can account for imperfect knowledge of. However, they also have “unknown unknowns” – things that we do not even know are happening and therefore cannot quantify the full effects of.
Although grounding-zone melting might result in higher sea level than we expected, at least we now know that it is happening and can begin to incorporate it into our models. The devil we know is better than the devil we don’t.
The post Guest post: The critical role of ‘grounding zones’ in the retreat of Earth’s ice sheets appeared first on Carbon Brief.
Guest post: The critical role of ‘grounding zones’ in the retreat of Earth’s ice sheets
New Zealand’s parliament has adopted a controversial new law blocking a whole avenue of climate litigation and shutting down its most advanced corporate lawsuit, which has been blamed by the government for shaking business confidence and investment.
The Climate Change Response (Tort Liability) Amendment Bill, expected to take effect in the coming days after it is formally signed by the Governor-General, prevents all current and future civil claims for climate loss or harm under tort law.
Justice minister Paul Goldsmith said last week that the aim was to give businesses “certainty around their climate change obligations”, noting it would not alter the government’s responsibilities under the Climate Change Response Act 2002 nor business obligations under the Emissions Trading Scheme.
“Our response to climate change is best managed by the Government at a national level and not through piece-meal litigation in the courts,” he added in a statement.
Such litigation, he said, “risks developing a new regime that contradicts the framework Parliament has already enacted” to tackle climate change.
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Experts say that despite dismissing the lawsuit, the ruling sets a precedent by confirming that climate science can establish legal liability for the damage caused by emissions
Goldsmith singled out a key domestic climate lawsuit brought by Northland iwi leader and activist Mike Smith against six big companies: dairy firms Fonterra and Dairy Holdings, energy firms Genesis Energy and Z Energy, New Zealand Steel and coal mining firm BT Mining. A seventh original defendant, Channel Infrastructure, was dropped after it permanently decommissioned its Marsden Point oil refinery.
Smith argued that these companies had caused him harm under public nuisance and negligence law, as well as a third breach of a duty to cease contributing to climate change that has yet to be tested domestically. He did not seek financial compensation, instead asking for the companies to immediately stop emitting or contributing to net greenhouse gas emissions.
In one of the most advanced corporate climate accountability lawsuits in the world, a trial had been scheduled for April 2027 after the Supreme Court unanimously allowed the case to continue.
Corporate lobbying in the shadows
Smith described the passing of the bill as “deeply concerning”, particularly as it coincided with the Supreme Court hearing another of his climate lawsuits. In that case, Smith v Attorney-General, he argues that the government’s response to climate change and its impacts on Māori communities in particular breaches rights to life and culture.
“That timing raises profound questions about the separation of powers and the rule of law,” said Smith. “Whatever one’s view of the merits of these cases, it is deeply troubling when parliament intervenes to remove a legal pathway while the courts are actively considering fundamental questions about climate responsibility, rights and the crown’s obligations.”
The bill – which says that no person (including the government) can be found liable in tort for emissions-related climate change effects – followed major lobbying efforts by the companies defending themselves in Smith’s lawsuit. They outlined a proposed legal amendment in a briefing note to the government in 2024.
The centre-right government has been fiercely criticised over its lack of transparency in relation to this lobbying activity. The national ombudsman recently found that the Prime Minister’s Office effectively withheld information requested by the Environmental Law Initiative about meetings, discussions and conversations regarding Smith’s case.
Green groups fail to stop bill
The bill sparked huge concern among environmental campaigners in New Zealand and elsewhere. Greenpeace Aotearoa called it a “shocking abuse of executive power” and the vast majority of submissions to a parliamentary inquiry said it should be rejected.
But in the end, it was adopted with little resistance, moving relatively smoothly through parliament, passing its third reading by 67 votes to 53. Sam Bookman, climate law lecturer at Melbourne Law School, told Climate Home News he was not surprised by this, given that the coalition government has a secure majority.
A complaint has been made to the UN special rapporteur on climate change and human rights by Smith, the National Iwi Chairs Forum Pou Tikanga and youth coalition Climate Clinic Aotearoa over what they see as the government’s heavy-handed approach. Smith is also challenging the new law in yet another lawsuit.
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Bookman thinks it “very unlikely” that such a challenge will succeed, noting that New Zealand’s constitution is firmly anchored in parliamentary sovereignty.
But the expert in climate law does not see the bill as the end of legal action in the country, noting that New Zealand has a “sophisticated climate litigation landscape with a growing number of specialist and experienced lawyers and NGOs”.
The country is also approaching its next general election in November, and some opposition parties have pledged to restore access to the courts if elected.
Amanda Larsson, global project lead on agriculture for Greenpeace International, said: “This law deserves to be tested, and I strongly encourage the international climate litigation community to unite and help defend New Zealanders’ fundamental right to hold polluters accountable before this becomes a global blueprint.”
Copycat legislation on the rise
New Zealand’s move is part of a small but growing legislative effort to shut down climate litigation around the world.
In the US, Republican politicians introduced legislation in the House and Senate in April that would shield fossil fuel firms from climate liability lawsuits. Similar laws have already been passed at state level in Tennessee, Utah, Iowa and Louisiana.
The German state of Bavaria has put forward a similar proposal to the Federal Council, aiming to block private climate claims as well as the recognition and enforcement of foreign judgments imposing such liability. There are also proposals to limit available remedies and actions in the Netherlands and Belgium.
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Bookman said he expects more efforts to counter climate damages litigation and advised plaintiffs to think about how to respond, including drawing on broader support in opposing them.
“Even though it’s very hard for plaintiffs to win these types of cases, companies are very eager to avoid the expense, embarrassment and political accountability that come even with unsuccessful lawsuits,” he said.
The post New Zealand moves to protect business with law curtailing climate litigation appeared first on Climate Home News.
New Zealand moves to protect business with law curtailing climate litigation
Bhima Yudhistira Adhinegara is the Executive Director of the Center of Economic and Law Studies (CELIOS), an Indonesia-based economic think tank. Muhammad Zulfikar Rakhmat is the Director of the China-Indonesia desk at CELIOS.
Indonesia produces around 60% of the world’s nickel, a metal used to manufacture batteries for electric vehicles (EVs) – more than any other country in the world. But in 2026, the government sharply reduced how much of its nickel can be extracted from the ground.
Production quotas were reduced by around 40% this year compared to 2025. Weda Bay, the largest nickel mine on Earth, had its allowance cut by more than 70% and exhausted its full-year quota by the end of May, halting mining entirely; it cannot resume large-scale extraction until next year unless regulators grant an extension.
The policy has sparked a vivid debate in Indonesian policy circles: how can the country shift its strategy from a decade of mining vast quantities of cheap nickel to producing a high-value and low-carbon material that the rest of the world wants for EV batteries.
The cuts aren’t a silver bullet to clean up Indonesia’s nickel industry, whose smelters are powered by coal – the most polluting fossil fuels. But alongside stricter enforcement of environmental rules, it is one side of efforts to produce more sustainable nickel for a premium.
Restricting Indonesia’s nickel output
Production quotas were introduced to stop the collapse of nickel prices because of oversupply in the market. Prices had fallen more than 40% in 2023 alone and kept sliding as Indonesian supply kept growing, hitting a four-year low of around $13,900 a ton in late 2025.
Critics called the recent tightening of production quotas proof that Indonesia’s nickel strategy has failed, arguing that the industry shouldn’t need to throttle its own output to survive. But when assessed against what the policy was supposed to do – push up nickel prices – it has worked. Prices jumped to $20,000 a ton in May, the highest since 2024.
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Chinese industry groups representing companies that have invested billions to mine and refine the country’s nickel were furious, warning Indonesia’s president Prabowo Subianto that the cuts put $50 billion worth of investment at risk. But much of that Chinese capital is sunk into smelters and processing plants built specifically to run on Indonesian ore, and cannot simply be moved elsewhere. That gives Jakarta more room to hold its ground than the warning suggests.
Stronger environmental enforcement
Since the start of the year, Indonesia’s forestry task force has seized more than four million hectares of land from mines and plantations operating illegally in protected forests, collecting over two trillion rupiah ($113 million) in fines.
This included 148 hectares seized from Weda Bay for lacking a forestry permit. The share of nickel produced from illegal small-scale mining also fell from about a quarter in 2022 to roughly 10% by 2024.
The crackdown responds to serious environmental damages in the nickel industry. On Obi Island, a waste pond collapsed after heavy rain in June 2025, flooding three villages and killing a resident. Internal company tests found chromium-6 – a carcinogen – in the water, in quantities far above the legal limit. The footprint of another mine near Raja Ampat, which is home to some of the world’s richest coral reefs, grew 60-fold in just eight years.
The market is responding to early cleanup efforts. Low-carbon nickel now sells for a real premium, roughly $18,800 to $19,300 a ton compared with $17,900 to $18,300 otherwise, as carmakers seek to source cleaner materials to comply with the European Union’s new emissions rules for imports.
In turn, this is incentivising the industry to do more to green its operations. Vale Indonesia’s smelter in South Sulawesi now runs almost entirely on hydropower, for example.
None of this addresses coal use, however. Major Indonesian nickel producers still emitted an estimated 15 million metric tons of greenhouse gases in 2023. Indonesia may be cracking down on illegal mining and rewarding cleaner producers but it is still running its mines on the dirtiest fuel available.
Unequal benefits
For Indonesia to truly benefit from producing cleaner and high-value nickel, it needs to reap the economic benefits too. Although the industry has boosted the country’s economic growth, the reality on the ground tells a different story.
Konawe in Southeast Sulawesi is home to a major smelting complex. Growth in the district jumped from 6% to 22% between 2015 and 2023, driven almost entirely by the nickel industry, according to a study by the Lowy Institute study. At the same time, poverty levels increased slightly and unemployment remained unchanged.
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In Halmahera, another epicentre of the nickel industry, spending by the poorest fifth grew just 5% between 2019 and 2022, compared with 28% for the wealthiest fifth, according to a separate study.
Part of the reason for this inequality is the system for transferring mining royalties to district authorities where the mines are located. In theory, they are entitled to the largest share. But in practice, payments are delayed, companies routinely dispute what they owe and royalties are pooled and distributed across a larger area.
The Natural Resource Governance Institute has found that decentralisation handed local governments power to approve new mines faster than they could build their capacity to manage them. Higher output raises national income on paper, but local governments remain constrained by fiscal rules and infrastructure costs that scale with mining.
None of this makes the 2026 quota cuts a mistake. Indonesia has every right to defend its pricing power over a resource it controls. But limiting extraction isn’t going to fix underlying issues around environmental enforcement and revenue-sharing. That requires rules that are consistently enforced, royalties that reach communities living by the mines, and a plan to wean smelters off coal.
The post Indonesia’s nickel production cuts are not enough to create a sustainable industry appeared first on Climate Home News.
Indonesia’s nickel production cuts are not enough to create a sustainable industry
Climate Change
Risk of “catastrophic” oil spill reaching Kimberley coast found in Woodside’s Scott Reef gas drilling plans
SYDNEY, Monday 24 August 2026 – New analysis of Woodside modelling released by Greenpeace Australia Pacific and Environs Kimberley has revealed the oil and gas corporation’s plans to drill at Scott Reef could cause an oil spill up to 30 times bigger than the 2009 Montara disaster, impacting the Kimberley coastline and reaching as far as Indonesia.
The new analysis details the “catastrophic” oil spill risk put to environmental regulators for approval by Woodside in its Browse to North West Shelf Project (Browse) plans, the worst-case scenario being a blowout directly below Scott Reef, polluting whale migratory pathways and covering isolated turtle nesting ground with oil condensate.
An FOI application (F348) revealed the federal environment department (DCCEEW) asked offshore oil and gas regulator NOPSEMA to look into the oil spill risk in 2025. NOPSEMA’s response to the application refused access to its report, and one document shows DCCEEW sought further advice this year.
Greenpeace and Environs Kimberley are calling on the Federal Government to publicly release the NOPSEMA report given the risk of an uncontrolled release of oil condensate from directly below Scott Reef.
Hannah Schuch, Senior Campaigner at Greenpeace Australia Pacific, said: “Woodside is aware that drilling at Scott Reef risks a massive oil spill that would have severe, far-reaching consequences. It appears environmental regulators are aware too.
“The state and federal governments need to take this risk from Woodside’s drilling plans seriously, as they could end up allowing the worst oil spill in Australian history.
“The pygmy blue whales that migrate up and down the WA coast with their newborns each year could be swimming and feeding in toxic, oil-slicked water. Woodside’s proposal to drill at Scott Reef is an environmental disaster waiting to happen, and the WA and federal governments have one surefire way to prevent catastrophe — reject Browse.”
Martin Prichard, Executive Director at Environs Kimberley, said: “A catastrophic oil spill by Woodside would be disastrous not just for marine life in the area but also for the Kimberley’s $500 million tourism industry.
“The state and federal governments will see five marine parks on the Kimberley coast included in the risk area of a catastrophic Woodside oil spill.
“The Montara oil spill was disastrous for West Timor with the toxic oil destroying seaweed farmers’ livelihoods. The Kimberley dodged a bullet with Montara, we were lucky the spill didn’t head our way. Myself and a crew flew over the Montara oil spill and followed it as far as we could. It was like a scene from a disaster movie.”
After the WA Environmental Protection Authority deemed Browse “unacceptable” due, in part, to oil spill risk, Woodside submitted a mitigation plan based on technology that has never been used “in anger”, a weakness stated in an independent expert review of the plan.
Professor Richard Steiner, independent oil spill expert, said: “A large offshore spill is impossible to effectively contain or recover. Historically, only 2-6% of total spill volume is recovered and the ecological injury from the release of toxic hydrocarbons in the sea can be severe, extensive, and long-term.
“Here in Alaska, government research concludes that several marine populations injured by the 1989 Exxon Valdez oil spill, including whales, fish, and seabirds, are still not recovering today, 37 years later. We should expect similar long-term ecological impacts in Western Australia if there were to be a major oil spill. The only sure way to avoid the risk of a catastrophic marine oil spill is to not develop oil and gas projects in marine environments.”
-ENDS-
Media contact
Emma Sangalli on emma.sangalli@greenpeace.org or 0431 513 465
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