Scientists' 'terrible' idea calls for snow cannons to pump ice in bid to save Antarctic ice shelf | The Japan Times
Andrew Lockley
Scientists' 'terrible' idea calls for snow cannons to pump ice in bid to save Antarctic ice shelf
AFP-JIJI
PARIS - Scientists seeking to avoid catastrophic sea-level rises from the melting West Antarctic ice sheet have come up with a “terrible” solution: use snow cannons to pump trillions of tons of ice back on top.
The gargantuan ice sheet contains enough frozen water to raise global sea levels by 6 meters (20 feet).
Just 1 meter of sea-level rise would be enough to displace around 190 million people, and a rise of 3 meters would imperil mega-cities across the world, including New York, Shanghai and Tokyo.
In particular, scientists are increasingly concerned that the Pine Island and Thwaites glaciers in Western Antarctica — which could potentially cause a sea-level rise of 3 meters — have reached a “tipping point” that could see irreversible melting irrespective of cuts to greenhouse gas emissions.
And as planet-warming emissions continue to rise despite the Paris agreement on climate change, awareness is growing that limiting temperature rises to under 2.0 degrees Celsius (3.6 Fahrenheit) — the treaty’s cornerstone goal — may be insufficient to avert disaster.
Geo-engineering projects — large-scale, deliberate intervention in Earth’s climate — have garnered much attention in recent years, such as injecting particles into space or storing CO2 in the ground.
But few have addressed the issue of sea-level rises, which is likely to cause more human misery than just about any other climate impact.
Experts at the Potsdam Institute for Climate Impact Research (PIK) on Wednesday released their model for one such approach: a massive displacement of seawater from melted ice, sucked from the sea and showered back on top of the West Antarctic glaciers to stop them from disappearing.
“It’s a terrible thing to do, no doubt about it, and we are not suggesting this by any means,” said Anders Levermann, PIK physicist and lead study author of the study published in Science Advances.
“But all physical modeling shows that if we keep to the Paris climate agreement to 2 C of global warming, we will eventually get 5 meters of sea-level rise and potentially more.”
In the simulations, Levermann and the team determined that the glaciers could be saved by a massive artificial surge in annual snowfall.
In fact, the amount needed to stabilize the glaciers would be at least 7.4 trillion tons of snow — the equivalent in mass of 150,000 jumbo jets.
The operation would involve hundreds of snow cannons, powered by 12,000 wind turbines, spraying sea water that would fall as snow over an area the size of Costa Rica.
Levermann stressed that the plan is currently just a hypothesis, and that to succeed it would need to be coupled with radical emissions cuts to stand any chance of success.
Such a project has not been costed and would require “something resembling an Antarctic moon station” with years of round-the-clock work, Levermann said.
Previous geo-engineering options to stave off West Antarctic melt have included constructing Eiffel Tower-size columns on the seabed to prop up the ice shelf, and a 100-meter-tall, 100-kilometer-long berm to block warm water flowing underneath.
Levermann admitted the PIK project, if ever realized, would have “terrible” effects on Antarctica, but insisted that limiting global sea-level rises is a desirable trade-off.
“It’s as big as North America from Mexico to Canada. There’s no place on Earth that’s protected on that scale,” he said.
“This endeavor would make Western Antarctica an industrialized compound. But if we’ve destabilized (the ice shelf), everything will change dramatically anyway.
“So we either build our coastal protections as high as 5 meters worldwide, or do something crazy like this.”
Stephen Salter
Andrew
Attached are some calculations about the use of marine cloud brightening for reducing sea level rise and some graphs of the Schwartz and Slingo equations to show the effects cloud thickness and liquid water content of clouds.
My calculation assumes
that we are using mono-disperse spray with a liquid drop
diameter of 0.8 microns. This choice was based on the nozzle
size we can etch in silicon, the performance of Pentair filters
and the Kohler equation for sodium chloride. As far as I know
most modellers have used spray with the wider spread of the
accumulation mode which is built in to climate models. Our 0.8
micron diameter is at the small end skirt of the diameter
histogram while the mass of a drop at the foot of the top skirt
is more than 100 times greater. It is the number of successful
nucleations that matters for Twomey, NOT the mass of spray.
Drop number depends
directly on the initial concentration of condensation nuclei. I
was using the maps in the Vallina paper which are well below
values used by some modellers. The mobility of spray vessels
allows us to cherry pick the best places and seasons. As far as
I know the Camilla Stjern group at
were the first
modellers to think of spraying only in regions with low cloud.
If the main
contribution to sea level rise is the temperature we can spread
the cooling anywhere and choose regions with the best
susceptibility according to season or special needs like coral
or hurricane moderation.
I would be grateful for suggestions for any other values for input numbers.
Best wishes
Stephen
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