The long-term effects of climate change are significant and pervasive. Global temperatures are warming, and sea levels threaten to rise at alarming rates. By 2100, an increase in global temperatures of 2 degrees Celsius could melt the Greenland and Antarctic ice sheets enough to cause the sea to rise by as much as a meter, displacing millions of people and causing trillions of dollars in damage.

While clean energy initiatives race to catch up with rising atmospheric greenhouse gases, geoengineering projects may be a way to mitigate rising sea levels. Some of the glaciers that are in the most peril are sliding on sheets of water or sediment. These flows are only a few kilometers across. It's possible that by stopping the movement of these glaciers, we could allow them to freeze through and stop their melting—at least for a time.

A piece in Nature argues that this is the way forward. "Geoengineering of glaciers has received little attention in journals. Most people assume that it is unfeasible and environmentally undesirable," writes John C. Moore, the chief scientist at the College of Global Change and Earth System Science, Beijing Normal University, China. "Is allowing a ‘pristine’ glacier to waste away worth forcing one million people from their homes? Ten million? One hundred million?"

Moore and colleagues lay out a few options for how such a large-scale project could be accomplished. The first idea is to stop the flow of warm water heading toward the glaciers. This could be done in Greenland with a 100-meter-high wall, or berm, across a five-kilometer fjord blocking water from the Atlantic from eating away at the glacier. The authors point out that a project of this size is feasible. "Ten times more material—1 cubic kilometre—was excavated to build the Suez Canal," they note.

Another option, to address the more important problem of melting Antarctic ice sheets, is to construct artificial islands and berms to help hold back the sheets. These projects would be more challenging. To hold back the melting Pine Island Glacier, six cubic kilometers of material would be required, 60 time as much as is needed for the Greenland project. There are other barriers too. "Technologies might need to be developed to operate beneath floating ice," Moore writes.

The scientists final idea is to stop the flow of water beneath the glacier. The streams beneath the glacier melt ice through friction, so the entire glacier ends up slipping farther out on a thin sheet of water. If we could somehow access the ice streams a kilometer below the glacier's surface and stop them, it might allow the glacier to solidify.

These geoengineering ideas sound somewhat fantastical, but it's clear that Moore and his colleagues take them very seriously. If humanity is going to meet the global challenge of climate change, unconventional solutions might be required.

Source: Nature

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