A vast network of lakes and streams lies beneath the thick ice sheet. This water can lubricate the ice, allowing it to slide more rapidly toward the ocean.
Our new research shows “subglacial water” plays a far larger role in Antarctic ice loss than previously thought. If it’s not properly accounted for, future sea-level rise may be vastly underestimated.
Including the effects of evolving subglacial water in ice sheet models can triple the amount of ice flowing to the ocean. This adds more than two metres to global sea levels by 2300, with potentially enormous consequences for coastal communities worldwide.
How hidden lakes threaten Antarctic Ice Sheet stability. (European Space Agency)
Understanding the role of subglacial water
Subglacial water forms when the base of the ice sheet melts. This occurs either due to friction from the movement of the ice, or geothermal heat from the bedrock below.
So it’s crucial to understand how much subglacial water is generated and where it goes, as well as its effect on ice flow and further melting.
But subglacial water is largely invisible. Being hidden underneath an ice sheet more than two kilometres deep makes it incredibly difficult to observe.
Scientists can drill boreholes through hundreds to thousands of metres of ice to get to it. But that’s an expensive and logistically challenging process.
Alternatively, they can use ice-penetrating radar to “see” through the ice. Another technique called laser altimetry examines changes in the height of the ice at the surface. Bulges might appear when lakes under the ice sheet fill, or disappear when they empty.
More than 140 active subglacial lakes have been identified beneath Antarctica over the past two decades. These discoveries provide valuable insights. But vast regions — especially in East Antarctica — remain unexplored. Little is known about the connections between these lakes.
Hot water drilling at Shackleton Ice Shelf, East Antarctica.Duanne White, University of Canberra/Australian Antarctic Division
What we did and what we found
We used computer simulations to predict the influence of subglacial water on ice sheet behaviour.
Then we explored how different assumptions about subglacial water pressure affect ice sheet dynamics. Specifically, we compared scenarios where water pressure was allowed to change over time against scenarios where it remained constant.
When the effects of changing subglacial water pressure were included in the model, the amount of ice flowing into the ocean under future climate nearly tripled.
These findings suggest many existing sea-level rise projections may be too low, because they do not fully account for the dynamic influence of subglacial water.
Our research highlights the urgent need to incorporate subglacial water dynamics into these models. Otherwise we risk significantly underestimating the rate and magnitude of future sea-level rise.
We simulated subglacial water pressure across Antarctica, revealing vulnerable regions potentially influenced by subglacial water, and mapped both active (blue) and stable (yellow) subglacial lakes and subglacial water channels (black lines).Zhao, C., et al, 2025. Nature Communications.
In the video below, the moving dark lines show where grounded ice begins to float. The left panel is a scenario where subglacial water is not included in the ice sheet model and the right panel is a scenario that includes the effects of evolving subglacial water.
Simulated Antarctic ice velocity over 1995–2300, using the Elmer/Ice model of ice sheets.
A looming threat
Failing to account for subglacial water means global sea-level rise projections are underestimated by up to two metres by 2300.
A two-metre rise would put many coastal cities in extreme danger and potentially displace millions of people. The economic damage could reach trillions of dollars, damaging vital infrastructure and reshaping coastlines worldwide.
It also means the timing of future tipping points are underestimated too. This is the point at which the ice sheet mass loss becomes much more rapid and likely irreversible. In our study, most regions cross this threshold much earlier, some as soon as 2050. This is deeply concerning.
The way forward
Understanding Antarctica’s hidden water system is challenging. The potential for rapid, catastrophic and irreversible ice loss remains.
More observations are needed to improve our models, particularly from remote regions such as East Antarctica. Continuing to gather information from boreholes, ice-penetrating radar and satellites will help us better understand how the underside of the ice sheet behaves. These techniques can then be combined with computer simulations to enable more accurate projections of future ice loss and sea-level rise.
Our new research shows integrating subglacial water dynamics into ice sheet models is a top priority. Understanding this hidden threat is crucial as the world grapples with the consequences of global warming especially rising seas.
Chen Zhao is the recipient of an Australian Research Council Discovery Early Career Researcher Award. Dr Zhao is affiliated with Australian Antarctic Program Partnership (AAPP), at the Institute of Marine and Antarctic Studies (IMAS), University of Tasmania, supported under the Antarctic Science Collaboration Initiative program.
Ben Galton-Fenzi is also affiliated with Australian Antarctic Program Partnership (AAPP), at the Institute of Marine and Antarctic Studies (IMAS), supported under the Antarctic Science Collaboration Initiative program, and the Australian Centre for Excellence in Antarctic Science, supported under the Australian Research Council Special Research Initiative, both based at the University of Tasmania.
Over the weekend, Labor promised to subsidise home batteries by 30%. This would save about A$4,000 per household up front for an average battery. The scheme has a goal of one million batteries by 2030, costing an estimated $2.3 billion.
The promise was received broadly favourably as a measure to help with cost of living pressures and encourage the broader shift to clean energy. Labor’s policy has some similarity to an earlier Greens pledge. Last month, the Coalition hinted it was working on its own home battery plan. Opposition leader Peter Dutton has attacked Labor’s plan, claiming the subsidies would benefit the rich.
Dutton makes a good point. Upfront subsidies have to be well targeted. If they’re not, they could easily go to wealthier households and leave poorer ones behind.
To fix it, Labor should start with lower subsidies – and means test them.
What’s the fuss about home batteries?
Homes with batteries can use stored solar energy instead of grid energy, or charge from the grid when power is cheap and use it when grid power is expensive. They can reduce power bills by around $1,000 a year.
Over 300,000 Australian households already have a home battery. Uptake was already accelerating in Australia and overseas, as battery prices fall and power prices climb.
If this policy leads to 1 million batteries by 2030 as Labor hopes, they would boost grid stability, reduce demand for expensive peak power from gas generators and even avoid the need to build some new transmission lines. These would be positive – if the benefits can be spread fairly.
Subsidies must be properly targeted
Caution is necessary, because we have seen very similar issues with previous schemes.
When solar panels were expensive in the 2000s, many state governments offered subsidies to encourage more households to put them on their roofs. On one level, this worked well – one third of all Australian households now have solar. But on another, it failed – richer households took up solar subsidies much more than poorer, as my research has shown. As solar prices have fallen, this imbalance has partly been corrected.
Home batteries are now in a similar situation. Installing an average sized home battery of between 5 and 10 kilowatt hours can cost less than $10,000, without the proposed federal subsidy. But this upfront cost means it’s currently largely wealthy households doing it, as I have shown in other research.
If Labor’s policy isn’t properly targeted, wealthier households are more likely to take it up. This is because they can more easily afford to spend the remaining cost. Studies on electric and other vehicle subsidies in the United States show at least half of the subsidies went to people who would have bought the vehicle regardless. That’s good for wealthy households, but unfair to others.
Targeting has advantages for governments, too. Proper targeting would reduce the cost to the public purse.
Wealthier households like these in an expensive Sydney suburb were more likely to take up solar – and benefit from early subsidies.Harley Kingston/Shutterstock
So who should be eligible?
Wealthier households are likely to be able to afford home batteries without the subsidy – especially as costs fall.
The cost of living crisis has hit less wealthy households hardest. A home battery policy should focus heavily on giving these households a way to reduce their power bills.
How can governments do this? Largely by means-testing. To qualify for the subsidy, households should have to detail their financial assets.
To begin with, a policy like this should only be eligible for households outside the top 25% for wealth.
What about the 31% of Australians who rent their homes? This diverse group requires careful thought.
Governments may have to offer extra incentives to encourage landlords to install home batteries. The solar roll-out shows landlords do benefit, as they can charge slightly higher rent for properties with solar.
How much should subsidies be?
Labor’s election offering of a 30% subsidy is too generous.
While home batteries can cost more than $10,000, cheaper battery options are now available and state incentive schemes are also emerging. Western Australia, for instance, will have its own generous battery subsidy scheme running before July 1.
Some households might be able to get subsidies at both state and national levels, which would cover most of the cost of a smaller battery.
When governments offer high subsidies at the start of a new scheme, there’s a real risk of a cost blowout.
To avoid this, governments should begin with the lowest subsidy which still encourages household investment. If low subsidies lead to low uptake, the government could then raise subsidies after an annual review.
Another option is to vary how much the subsidy is based on household wealth. Lower wealth households get higher subsidies (say $2,500) while higher wealth households get a much lower subsidy (say $500).
Governments could even consider equitable reverse auctions, where households with similar wealth compete for subsidies. Governments can then choose lower bids in the interest of cost-effectiveness.
At present, Labor’s policy would give higher subsidies for larger batteries. This isn’t ideal. On solar, there’s a lack of evidence higher subsidies lead to larger solar systems, while households with more wealth tend to get larger solar systems.
Good start, improvement needed
Labor’s home battery policy has been welcomed by many in the energy sector. But as it stands, we cannot be sure it will fairly share the benefits of home batteries.
If Labor or the Coalition does offer a well-targeted home battery policy, it would be world leading. Over time, it would directly help with the rising cost of living and ensure less wealthy households benefit.
Rohan Best previously received funding from the Economic Research Institute for ASEAN and East Asia (ERIA).
As climate change wreaks havoc with the world’s oceans, future production of fish, crustaceans and other aquatic organisms is under threat.
Our new research shows how this disturbance will play out for Australia’s prawn industry, which is concentrated in Queensland. We found by 2100, sea level rise threatens to flood 98% of the state’s approved prawn areas.
The problem is not confined to prawns – Queensland barramundi farming is also at risk from sea-level rise. Climate change also poses challenges for other major seafood industries in Australia, including salmon in Tasmania.
Australian seafood is vital to our culture and diets, and the national economy. We must take steps now to ensure the aquaculture industry thrives in a warmer world.
Spotlight on Queensland prawns
Aquaculture refers to breeding, rearing and harvesting fish, crustaceans, algae and other organisms in water. Australia’s aquaculture industry is expected to be worth A$2.2 billion by 2028–29.
Aquaculture can involve a variety of methods, from ponds and sea cages to indoor tank systems and even giant ships.
Queensland is also expected to experience a 0.8m sea-level rise by 2100, under a high-emissions scenario. Our research investigated how this could affect the state’s aquaculture industry.
We did this by examining existing data on coastal inundation and erosion from sea-level rise, combined with data on current and future aquaculture production areas.
We found 43% of sites where aquaculture production is currently occurring are at risk from sea-level rise. Prawn farming is the most vulnerable.
About 98% of areas approved for prawn farming in Queensland are expected to be inundated by seawater by 2100. The risk includes 88% of areas currently producing prawns. Prawns are grown in large ponds on land near the coast with access to saltwater, which makes them particularly vulnerable to inundation. Annual prawn production losses due to sea-level rise could reach up to A$127.6 million by century’s end.
Inundation and coastal erosion can cause breaches in pond walls compromising their structural integrity. These risks may be amplified when sea-level rise coincides with coastal flooding. Rising seas can also increase salinity in surrounding soils and groundwater, further affecting ponds. Other aquaculture infrastructure, such as hatcheries, buildings, and roads, may also be disrupted.
The Gold Coast region – a prawn production hub – is particularly vulnerable. Damage caused by ex-Tropical Cyclone Alfred highlights the vulnerability of coastal infrastructure to extreme weather. This will only worsen as the planet warms.
Queensland barramundi farms also face a serious threat. Some 44% of areas producing barramundi are likely to be exposed to inundation, causing up to A$22.6 million in annual production losses. Meanwhile, two of Queensland’s designated “Aquaculture Development Areas” – regions earmarked by the state government for industry expansion – may be unsuitable due to future sea levels. Both are located in the Hinchinbrook Shire Council area.
Rising water temperatures stress animals such as salmon, lowering oxygen levels which slows growth rates and increases their risk of disease. Such depletion is a particular concern in already low-oxygen environments, such as Tasmania’s Macquarie Harbour.
Ocean heatwaves can cause mass fish deaths and devastate production. In Tasmania in February, more than 5,500 tonnes of dead fish were dumped at southern Tasmanian waste facilities – a problem linked to warmer water temperatures.
Dead and decomposing fish can further alter oxygen levels in water, spread disease to wild populations and attract scavengers. In the Tasmanian case, fish remains washed up on public beaches, angering the public and leading to calls for greater industry regulation.
Extreme weather further complicates aquaculture operations. Storms, flooding and abnormal rain patterns can affect water salinity which impacts species growth and survival. They can also damage vital infrastructure, which may allow animals to escape.
This occurred in 2022, when repeated flooding and disease outbreaks on oyster farms in New South Wales led to complete stock losses, prolonged farm closures and workers being laid off.
For the countries and producers that are expected to suffer, those that plan for and adapt to climate shifts can minimise losses.
Key steps industry and government can take include:
planning farms in lower-risk areas and relocating vulnerable sites
implementing climate-resilient infrastructure and restoring coastal ecosystems near farms to buffer against climate impacts
expanding to include diverse species and selectively breeding stock that can tolerate the changing conditions
strategic government policies and planning, financial incentives, and investment in resilient infrastructure to help the industry stay ahead of climate risks.
With the right strategies, Australia’s aquaculture industry can adapt to a changing climate and continue to contribute to food security and community wellbeing.
Caitie Kuempel receives funding from the Blue Economy Cooperative Research Centre. She is affiliated with BECRC Marine Spatial Planning project.
Marina receives Griffith University International Postgraduate Research Scholarship and Griffith University Postgraduate Research Scholarship as and HDR PhD Student
The rainbow lorikeet and its colourful plumage has topped Australia’s largest citizen science event as the most numerous bird recorded across the country.
More than 4.1m birds were counted as part of BirdLife Australia’s annual Aussie Bird Count, a week-long event which involved 57,000 participants across the country last October.
Rising seas are already affecting coastal communities in Aotearoa New Zealand. On a global average, the sea level is now 18 centimetres higher than it was in 1900, and the annual rate of increase has been accelerating to currently 4.4 millimetres per year.
This may not seem much, but it is already amplifying the impact of storm and tidal surges. Over the coming decades and centuries, this will pose increasingly serious problems for all coastal communities.
But this is not the end of our troubles. Some parts of New Zealand’s coastline are also sinking. In many New Zealand cities, shorelines are steadily subsiding, with growing impacts on coastal infrastructure.
Our new research reveals where and how fast this is happening. We found the coastlines near all major cities in New Zealand are sinking a few millimetres each year, with some of the fastest rates in coastal suburbs of Christchurch, where the land is still adjusting to the impact of the 2011 earthquake.
Relative increase in sea level
Sea-level rise is happening globally because the ocean is expanding as it continues to warm and glaciers and polar ice sheets are melting.
Meanwhile, land subsidence operates on regional or local scales, but it can potentially double or triple the effects of sea-level rise in certain places. This dual effect of rising seas and sinking land is know as relative sea-level rise and it gives coastal communities a more accurate projection of what they need to prepare for.
To understand which parts of the coast are most at risk requires detailed and precise measurements of land subsidence. The key to this is to observe Earth from space.
We have used a technique known as interferometric synthetic aperture radar (InSAR). This involves the repeat acquisition of satellite radar images of the Earth’s surface, tied to very accurate global navigation satellite system measurements of ground stations.
This builds on earlier work by the NZSeaRise project, which measured vertical land movement for every two kilometres of New Zealand’s coastline. Our study uses a significantly higher resolution (every ten metres in most places) and more recent datasets, highlighting previously missed parts of urban coastlines.
Urban hotspots
For instance, in Christchurch the previous NZSeaRise dataset showed very little subsidence at Southshore and New Brighton. The big differences in the new data are not due to the increase in spatial resolution, but because the rate of vertical land movement is very different from the time prior to the 2011 earthquake.
Localised subsidence in these Christchurch suburbs is up to 8mm per year, among the fastest rates of urban subsidence we observed. These areas sit upon natural coastal sand dunes above the source area of the earthquake and the Earth’s crust is still responding to that sudden change in stress.
This map shows vertical land movement (VLM) in Christchurch, highlighting areas that are sinking. The circles around the coastline show NZSeaRise estimates (2003-2011) and continous blue shading highlights new results (2018-2021).Jesse Kearse, CC BY-SA
We have tracked vertical movement of the land with millimetre-scale precision for five major cities in New Zealand. The InSAR technique works particularly well in urban areas because the smooth surface of pavements, roads and buildings better reflects the satellite radar beam back into space where it is picked up by the orbiting satellite.
This means the estimates of relative sea-level rise for these cities are close to or above 7mm per year. If sustained, this amounts to around 70cm of sea-level rise per century – enough to seriously threaten most sea defences.
Our new satellite measurements provide a detailed picture of urban subsidence, even within single suburbs. It can vary by as much as 10mm per year between parts of a city, as this map of Dunedin and the Otago Harbour shows.
This map shows vertical land movement (VLM) in Dunedin. The darker blue colours highlight parts of the city where land is sinking at a rate of 4mm per year or more.Jesse Kearse, CC BY-SA
We found hotspots of very rapidly sinking regions. They tend to match areas of land that have been modified, particularly along the waterfront. During the 20th century, many acres of land were reclaimed from the ocean, and this new land is still compacting, creating an unstable base for the overlying infrastructure.
One example of this is in Porirua Harbour, where a section of reclaimed land near the mouth of Porirua Stream is sinking at 3–5mm per year. This is more than double the average rate for Porirua’s coast.
Rapidly sinking regions often match areas of land that have been modified or reclaimed, such as along the waterfront of Porirua Harbour.Jesse Kearse, from http://retrolens.nz, licensed by Land Information NZ, CC BY-SA
Paradoxically, perhaps, it is only by looking back on our planet from outer space that we can begin to see with sufficient detail what is happening to the land in our own backyard.
The good news is that we can use the results to identify coastlines that are particularly vulnerable to sea-level rise and plan accordingly for any future development. Our new measurements are just the first step in what must become a major effort to watch the ups and downs of our coastlines and urban areas.
Jesse Kearse does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
