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Cracked ice seen on the Thwaites Ice Shelf in October 2012. Source: NASA / J. Yungel
According to a new study published in the Journal of the European Geoscience Union, targeted engineering projects to curb the melting of glaciers could slow the collapse of the ice caps and limit the rise. sea level. The cryosphere. Although an intervention of similar size to that of large existing civil engineering projects can only have a 30% chance of success, a larger project would have a better chance of resisting the collapse of the ice caps. But study authors Michael Wolovick and John Moore warn that reducing emissions is essential to halting climate change and its dramatic effects.
"Doing geoengineering often means considering the unthinkable," says Moore, a scientist from the Beijing Normal University, China, and a professor of climate change at the University of Lapland, Finland. The term "geoengineering" is generally applied to large-scale interventions to combat climate change. But instead of trying to change the entire climate, Wolovick and Moore say we could apply a more focused approach to limiting one of the most dramatic consequences of climate change: raising the level of the sea.
Their "unthinkable" idea is glacial geoengineering: it modifies the geometry of the seabed near glaciers that flow into the ocean, forming a platform of ice to prevent them from melting further. Some glaciers, such as the Thwaites Ice Course in Great Britain or Florida in West Antarctic, are retreating rapidly. "Thwaites could easily trigger a leak [West Antarctic] the collapse of the icecap that would ultimately increase the global sea level to about 3 meters, "says Wolovick, a researcher at the Department of Geosciences at Princeton University, United States.
Instead of or in addition to limiting the effects of rising seas through traditional coastal protection, using geo-engineering glaciers to stop flooding at the source could be a viable option, as shown by Wolovick and Moore. "The most important result [of our study] "Significant ice cap intervention is generally in the order of magnitude of plausible human achievements," Wolovick said.
The team studied two conceptions of glacial geoengineering. One idea would be to build an underwater wall to block hot water reaching the base of the pack ice, which is very sensitive to melting. A simpler design is to build mounds or artificial columns on the seafloor: they would not block hot water, but could support and hold the glacier, which would help repel it. "In both cases, we imagined very simple structures, just piles of sand or gravel on the bottom of the oceans," says Wolovick.
The team made computer models on which they applied these designs to the Thwaites Glacier in a warming world. Thwaites is expected to be the largest single source of sea level rise and, from 80 to 100 km wide, it is one of the largest glaciers in the world. "Yes [glacial geoengineering] working there so we expected him to work on less difficult glaciers as well, "the authors write The cryosphere study.
Research shows that even the simplest design could slow the rate of sea level rise, giving more time for coastal societies to adapt to rising water levels. According to the models, the smallest intervention has a 30% probability of avoiding a collapse of the West Antarctic Ice Sheet in the foreseeable future. This intervention would consist of constructing mounds or isolated columns 300 meters high on the seabed using between 0.1 and 1.5 cubic kilometer of aggregate, depending on the strength of the material. This is similar to the amount of material that was excavated to build the Suez Canal in Egypt (1 cubic kilometer) or used in the Palm Islands of Dubai (0.3 cubic kilometer).
A more sophisticated project, going beyond the scale that humanity has attempted so far, would have a better chance of avoiding a collapse of the ice cap over the next 1000 years (the time of the simulations), as well as better chances to provoke the ice cap to find the mass. A small submarine wall blocking about 50% of the warm water reaching the base of the sea ice could have a 70% chance of success, while the larger walls could still delay or even stop the sea. Collapse of the ice cap.
Despite the encouraging results, scientists say that they do not advocate starting these ambitious projects anytime soon. Although the simplest design is similar to that of existing engineering projects, it would be built in one of the most challenging environments on the planet. The engineering details must therefore be adjusted. Nevertheless, the team wanted to see if glacial geoengineering could work in theory and wanted the scientific community to think and improve the designs.
"We all understand that we have an urgent professional obligation to determine how much society should know the rise in sea level and how quickly sea level rise is likely to occur. we would say that we also have to try with ways that society could protect against a rapid collapse of the ice cap, "says Wolovick.
Ice physics shows glacial geoengineering could withstand collapse of ice cap, but Wolovick and Moore are both convinced that reducing greenhouse gas emissions remains a priority in the fight against climate change . "There are dishonest members of society who will try to use our research to argue against the need to reduce emissions, and our research does not support this interpretation in any way," they say.
Technical glaciers would only limit sea level rise, while reducing emissions could also limit other adverse impacts of climate change, such as ocean acidification, floods, droughts and waves. heat. In addition, the team emphasizes that increased warming will make glacial engineering projects less feasible and reduce the chances of success. After all, their underwater structures could protect the bottom of the ice trays, but would not prevent the hot air from gnawing the ice at the top.
"The more carbon we emit, the less likely it is that the ice sheets will survive in the long term at a level close to their current level," Wolovick concludes.
Explore more:
Geoengineering Polar Glaciers to Slow Sea Level Rise
More information:
Stop Flood: Could we use targeted geoengineering to mitigate the rise in sea level? The cryosphere (2018). DOI: 10.5194 / tc-12-2955-2018
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