Three proposed geoengineering projects could buy us some time to address global warming
Studies show that sea levels are rapidly rising due to global warming, while it is predicted that a 2 °C increase by mid-century would swell the oceans by around 20 centimeters, on average. The ice sheets of Greenland and Antarctica will play an important role to this phenomenon as they will contribute more to sea-level rise than any other source. If we do not take action, by 2100, a 0.5–5% of the world’s population will be flooded each year as most large coastal cities will face sea levels that are more than 1m higher than currently, with the global cost of damages reaching US$50 trillion a year.
Apart from the reduction of greenhouse gas emissions, a team of scientists led by John C. Moore, professor at the College of Global Change and Earth System Science, Beijing Normal University, China and professor of climate change at the Arctic Centre, University of Lapland, Rovaniemi, Finland, propose an alternative solution to the disastrous sea level rise: to stop Antarctica and Greenland’s main glaciers from melting via massive geoengineering projects. The proposed projects were recently published in the journal Nature and are the following:
1. Pumping or cooling water beneath
As the ice slides over the glacier bed, it generates heat. This heat then creates fast-flowing streams that pour into the sea which, in turn, make the glacier move faster. In Antarctica, these streams can be quite shallow, and the scientists propose either pumping out the water or freezing it by circulating cooled water beneath the glaciers, in an effort to slow their progress.
2. Artificial islands to support ice shelves
When glaciers slip into the sea, they create enormous ice shelves, which are especially vulnerable as warmer waters can more easily make them thinner, while in some cases they break off completely, exposing the glacier and speeding up sea level rise.
The Pine Island and Thwaites, in West Antarctica, are the two largest potential sources of sea-level rise over the next two centuries, as both of them are losing height and flowing more quickly than two decades ago. A solution could be to artificially pin the ice shelves in front of the two glaciers by constructing berms and islands, extended from outcrops or built on the sea floor. They estimated that for Pine Island Glacier, this would require around 6 km3 of material, or 60 times more than would be needed to plug the Jakobshavn fjord.
3. A giant wall to block warm water
Their first suggestion concerns Jakobshavn glacier in western Greenland, one of the fastest-moving ice masses on Earth that contributes more to sea-level rise than any other glacier in the Northern Hemisphere (around 4% of 20th century sea-level rise results from ice loss from this glacier). Warmer water from the Atlantic is melting the glacier's base, so scientists propose the construction of a 100m-tall wall across the 5-kilometre fjord in front of Jakobshavn glacier to prevent the warm water from reaching it. Around 0.1 km3 of gravel and sand from Greenland’s continental shelf could be piled up on the sea bed to create this artificial embankment, that would be clad in concrete to stop erosion. According to the researchers, making the sill shallower would reduce the volume of warm water and slow the melting, so that more sea ice would form, even though this method does not help with the problem of warm air reaching the top of the glacier.
As most would expect, the feasibility of these projects is not yet proved. “The glaciers concerned need extensive study, including mapping the geomorphology of their beds and the rates at which they are melting,” the research team admits. But according to them, the biggest risk is doing nothing. “We understand the hesitancy to interfere with glaciers – as glaciologists, we know the pristine beauty of these places. But we have also stood on ice shelves that are now open ocean. If the world does nothing, ice sheets will keep shrinking and the losses will accelerate. Even if greenhouse-gas emissions are slashed, which looks unlikely, it would take decades for the climate to stabilize”, they say.
Source: World Economic Forum