Geoengineering Lunacy – Sea Walls and Volcano Bases for Polar Geoengineering
Guest essay by Eric Worrall
Scientists have proposed pumping brine to refrigerate the bases of glaciers from a nearby volcano lair, and vast Arctic and Antarctic seawalls to prevent warm water from coming into contact with polar ice. But they are worried abundant sea ice might pose engineering challenges.
Geoengineer polar glaciers to slow sea-level rise
John C. Moore,
Thomas Zwinger &
If nothing is done, 0.5–5% of the world’s population will be flooded each year after 2100. For example, a 0.5-metre rise in Guangzhou, China, would displace more than 1 million people; a 2-metre rise would affect more than 2 million. Without coastal protection, the global cost of damages could reach US$50 trillion a year. Sea walls and flood defences cost tens of billions of dollars a year to construct and maintain.
To stimulate discussion, we explore three ways to delay the loss of ice sheets.
1. Block warm water
A 100-metre-high wall with sloping sides of 15–45° could be built across the 5-kilometre fjord in front of Jakobshavn glacier by dredging around 0.1 cubic kilometres of gravel and sand from Greenland’s continental shelf (see ‘Glacial geoengineering’). This artificial embankment, or berm, could be clad in concrete to stop it being eroded. The scale of the berm would be comparable with large civil-engineering projects. For example, ten times more material — 1 cubic kilometre — was excavated to build the Suez Canal. Hong Kong’s airport required around 0.3 cubic kilometres of landfill. The Three Gorges Dam used 0.028 cubic kilometres of cast concrete.
2. Support ice shelves
One solution is 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. For example, the shelf buttressing Pine Island Glacier could be jammed by a berm located on Jenkins Ridge, a high point on the sea bed below the glacier. We estimate that this would require around 6 cubic kilometres of material, or 60 times more than would be needed to plug the Jakobshavn fjord. Relatively small artificial islands in other places — reaching up 300 metres from the sea bed — would require 0.1 cubic kilometres of material each. A large berm (10–50 cubic kilometres) in the open bay could prevent warmer waters from entering.
Material could be shipped to Antarctica from elsewhere in the world, or dredged or quarried locally. But it would be difficult in practice for engineers to work around the ice shelves, which grow and shrink as the glaciers, sheets and conditions fluctuate. Sea ice would also get in the way. Technologies might need to be developed to operate beneath floating ice. Major disturbances to local ecosystems would be expected and would require thorough assessment before and after pinning.
3. Dry subglacial streams
Deeper subglacial water in Antarctica is under pressure and should drain to the ocean without pumping. It could also be frozen by circulating cooled brines beneath the 10-metre-thick layer of sediment scoured at the glacier’s base. The Pine Island Glacier might be reached through the nearby volcanic outcrops of the Hudson Mountains. These lie within 80 kilometres of the glacier and the coast, and would be a good base for research into the sub-glacial environment and ice shelves. Again, the costs of such projects appear comparable to those of other large energy and civil-engineering works.
I admire the imagination – adding a Dr. Evil volcano base to the third solution was pure comedy genius. But I can’t help thinking there might be better ways of spending public money than initiating vast civil works projects in Antarctica and Greenland to protect a bit of ice.
via Watts Up With That? http://ift.tt/1Viafi3