Friday, September 21, 2018

Glacial Engineering Could Limit Sea-Level Rise, If We Get Our Emissions Under Control

This is a crevassed ice seen on the Thwaites Ice Shelf in October 2012. (Credit: NASA/J. Yungel) Click to Enlarge.
Targeted engineering projects to hold off glacier melting could slow down the collapse of ice sheets and limit sea-level rise, according to a new study published in the European Geosciences Union journal The Cryosphere.  While an intervention similar in size to existing large civil engineering projects could only have a 30% chance of success, a larger project would have better odds of holding off ice-sheet collapse.  But study authors Michael Wolovick and John Moore caution that reducing emissions still remains key to stopping climate change and its dramatic effects.

"Doing geoengineering means often considering the unthinkable," says Moore, a scientist at Beijing Normal University, China, and a professor of climate change at the University of Lapland, Finland.  The term 'geoengineering' is usually 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 targeted approach to limit one of the most drastic consequences of climate change:  sea-level rise.

Their "unthinkable" idea is glacial geoengineering: making changes to the geometry of the seafloor near glaciers that flow into the ocean, forming an ice shelf, to prevent them from melting further.  Some glaciers, such as the Britain- or Florida-sized Thwaites ice stream in West Antarctica, are retreating fast.  "Thwaites could easily trigger a runaway [West Antarctic] ice sheet collapse that would ultimately raise global sea level by about 3 meters," explains Wolovick, a researcher at Princeton University's Department of Geosciences, US.  This could have dramatic effects to the millions of people living in the world's coastal areas.

Instead of, or in addition to, limiting the effects of rising seas through traditional coastal protection, using glacier geoengineering to stop the flood at the source could be a viable option, as Wolovick and Moore show.  "The most important result [of our study] is that a meaningful ice sheet intervention is broadly within the order of magnitude of plausible human achievements," says Wolovick.

The team looked into two glacial-geoengineering designs.  One idea would be to build a wall underwater to block warm water reaching an ice shelf's base, which is very sensitive to melting.  A simpler design consists of constructing artificial mounds or columns on the seafloor:  they wouldn't block warm water but could support and hold back the glacier, helping it regrow.  "In either case, we were imagining very simple structures, simply piles of sand or gravel on the ocean floor," says Wolovick.

Read more at Glacial Engineering Could Limit Sea-Level Rise, If We Get Our Emissions Under Control

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