Globally, sea levels have risen by somewhere between 21cm and 24cm since 1880. Most of this rise is a consequence of water physically expanding as it warms, but in recent decades meltwater flowing off Greenland and Antarctica has significantly contributed too.
These rises in sea levels threaten coastal properties and the livelihoods and lifestyles of coastal communities, as well as the very existence of low-lying countries. Rising seas not only erode or flood land, they also let destructive storms reach ever farther inland. As melting polar ice becomes an ever more important contributor to sea-level rise, some have begun to embrace the notion that it could be slowed by technological means ranging from underwater curtains to ice-thickening pumps.
Let the storm rage on
Climate science has been here before. For years the field has been divided over the promise and pitfalls of solar geoengineering schemes, environmental modifications that seek to reduce the impact of climate-warming solar radiation. The most controversial methods involve spraying mists of particles into the stratosphere, which would reflect some of the sun’s energy back out into space and cool the planet. Proponents say these could help buy time to decarbonise without the world suffering the worst consequences of climate change. Critics say they are too risky. The arguments can become acrimonious. These battles are now spilling over onto the ice.
In December 2023 Ken Mankoff, a climate scientist at NASA, organised a workshop on polar geoengineering at a large science conference. Though he was warned that doing so would start a “civil war” in the field, he feels there is much more agreement than disagreement among polar scientists: no matter their position on geoengineering, all are concerned that the effects of climate change are far outpacing efforts to slow or halt them. Given the urgency, it is no surprise that fresh ideas are attracting interest.
The proposed interventions take many forms. One prominent suggestion centres on outlet glaciers, vast frozen rivers which slowly shift ice off the land mass and out to the warmer waters of the sea. Several have been accelerating. Ice loss from Thwaites glacier in Antarctica, for instance, has doubled in 30 years, currently contributing 4% of the 3.5mm of global annual sea-level rise. Glaciologists are worried it could eventually collapse, raising sea levels around the world by 65cm. Warm water is melting the ice’s marine edge from below, eroding its “grounding line”, where it grips onto the bedrock for stability. Some are, therefore, proposing enormous underwater curtains be installed to keep warming currents away from the ice’s edge.
No one can say yet what such curtains would be made of, how they would be secured, or how to stop them interfering with other vital local ecosystem services. Currents at Antarctica’s margins drive an important nutrient pump that feeds entire marine food chains farther afield. It is also possible that keeping one glacier cool would simply speed up the melting of its neighbours. To try to get some answers, scientists at the University of Cambridge’s Centre for Climate Repair are carrying out experiments in tanks and are planning outdoor trials in a local waterway.
Another prominent idea involves drilling boreholes through vertical kilometres of ice to siphon off water from the ice sheets’ base. The concept is straightforward: when a huge mass of ice sits on a bed of rock, the combined pressures and temperatures liquefy a thin layer of water at the interface of the rock and ice that helps the ice slide away. Removing this lubrication should help keep the ice in place.
For a long time such ideas—and others, including holding outlet glaciers in place with physical barriers, as well as thickening vulnerable sea ice by pumping seawater on top of it and freezing it in place—were seen mainly as science fiction. But they are gaining momentum. Dr Mankoff’s workshop was one of three held between October and December to discuss polar geoengineering; a fourth was held earlier this year. More are planned, and several research papers are in the works.
Yet opposition is growing. Martin Siegert, a climate scientist at Imperial College London, calls the whole discussion “absolutely insane”. “It came up years ago and many of us just ignored it. We thought ‘It’s not going to happen, so just don’t spend any time thinking about it.’” He and others have been taken aback by how much attention the proposals have attracted since the beginning of the year, and feel the time has come to challenge them.
Let it go
Some counter-arguments revisit themes familiar from the solar geoengineering debate—that techno-fixes detract from the main work of decarbonising, for instance, and that even exploratory research lubricates a slippery slope towards deployment. “If a government chose to make geoengineering-based research a part of its national Antarctic programme, it would send a pretty strong signal about the state’s intentions,” says Peder Roberts, a historian and member of the Scientific Committee on Antarctic Research, which advises various intergovernmental groups including the UN and the Antarctic Treaty secretariat. “The more expensive a piece of research is, the harder it is to say it isn’t political.”
Even if such research were undertaken, practical hurdles could stand in the way of implementation. Polar projects, unlike solar ones, are likely to be extremely expensive—costing many tens of billions of dollars. They present unprecedented engineering challenges: a seabed curtain to protect Thwaites glacier might be 80km long and would have to be installed, maintained and repaired in some of the roughest seas on Earth.
The political and regulatory challenges are also daunting. Antarctica is protected by international agreements known as the Antarctic Treaty System. All 57 member countries, including America and Russia, would have to come to an agreement before any geoengineering could start. Yet many of these same Antarctic Treaty countries have long failed to collaborate on two pillars of climate action: stopping greenhouse-gas emissions and raising climate funds for poor countries. Consequently, says Dr Roberts, “I’m pretty sure we will be well underwater before such an agreement could be reached.”
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