July 17, 2019

expert reaction to using artificial snow to stabilise the west Antarctic ice sheet

A study, published in Science Advances, reports that deposition of large quantities of artificial snow may reduce the rate of disintegration of the West Antarctic Ice Sheet.

Dr Robin Smith, Senior Research Scientist at the National Centre for Atmospheric Science at the University of Reading, said:

“There have been indications recently that a handful of glaciers in Antarctica have begun to collapse, which could more than double previous predictions of the sea level rise we will see in our children’s lifetimes, and lead to the eventual disintegration of a significant part of the ice sheet.

“Sea level rise will be a slow effect of climate change but very hard to reverse, increasing the frequency and severity of flooding of our densely populated coastal cities.  Could we stabilise these glaciers by pumping ocean water back onto the ice sheet and letting it freeze again?  This is the question Feldmann et al. have asked, testing how much you would have to add, and where, to prevent their collapse. 

“Theoretically they say the answer is yes, although there are still many unknowns that reduce our ability to accurately predict how these glaciers will really flow and melt in the future.  Practically, however, they find that the amount of water you would need to pump is enormous – enough to cover all of Great Britain more than 30 metres deep in water – and as they say, elevating and distributing the ocean water would mean an unprecedented effort for humankind in one of the harshest environments of the planet’.

“So although such a large-scale geo-engineering scheme is not utterly impossible, reducing greenhouse gas emissions as quickly as possible is clearly still the most reliable way to reduce the many harmful effects of climate change.”

Dr Robert Larter, Marine Geophysicist at the British Antarctic Survey (BAS), said:

“The scale of the logistic effort and the investment such a geoengineering project would require are not really clear from the paper. To put the 7400 Gt of additional snowfall over 10 years that is considered into context, this is more than four times the natural snow accumulation rate over the entire Pine Island and Thwaites drainage basins (1 Gt is slightly less than a cubic kilometre of seawater). All of the infrastructure required to provide the power, pump the water, desalinate it and turn it into snow would have to be delivered by icebreakers via a transit route that takes more than a week from southernmost South America, or even longer from New Zealand. Even for quite capable icebreakers, the area is only accessible for less than three months during the summer.

“Any such ice sheet geoengineering scheme is no more than a temporary solution to buy time. If warming continues then eventually a situation will be reached where significant surface melting occurs on the ice sheet in summer. Then, as the authors acknowledge, accumulation of water in crevasses may lead to destabilisation of the ice sheet through ice shelf hydrofracture. A more reliable and effective way to mitigate the long-term effects of climate change is to put effort and investment into technologies that will enable a zero-carbon economy.

“However, I think it is unlikely that zero carbon alone will save the west Antarctic ice sheet as even on that pathway warming is forecast to continue for some time and it will be a long time before there is significant cooling. For the same reasons the argument still stands that such a geoengineering scheme, even if it was practicable, would be just a very costly way of buying time.

“The big questions about the future of west Antarctic ice sheet are about the timescale of its retreat and contribution to sea level (how much, how fast?). These are the questions that the ITGC is aiming to provide better constrained answers to. Providing these answers will be of immense value for planning future sea defences and managed retreat strategies, and this is a practical aim that can be achieved on a tiny fraction of the budget that would be required for geoengineering schemes.

“Annual rainfall across the entire UK amounts to about 215 Gt, so the total over 10 years would be 2150 Gt. The UK is about two-thirds of the area of the combined drainage basins (catchments) of Pine Island and Thwaites glaciers, but considerably larger than the lower elevation areas over which it is suggested that the artificial snow would be added. The amount of water required to make artificial snow amounts to about three and a half times the amount of water that will fall over the same period across the entire UK.”

Prof David Vaughan, Director of Science at the British Antarctic Survey (BAS), said:

“Global society is calling for solutions to climate change, or at least, for options that might delay or reduce the severity of its impacts.  As ideas for ‘climate fixes’ emerge almost weekly, environmental scientists have an important role in testing, and challenging them.  I think Johannes Feldmann and his co-authors tread the tight-rope well.  They examined and challenge this idea without becoming advocates.  Indeed, they are careful to point out the severe side effects.  Frankly, I agree with their conclusion, ‘The ambitious reduction of greenhouse gas emissions is and will be the main lever to mitigate the impacts of sea level rise.’”

Dr Jeffrey S. Kargel, Senior Scientist at the Planetary Science Institute, Tucson, Arizona, said:

“On the surface of it, a just-published proposal by Johannes Feldmann and others sounds ridiculously impractical. However, the authors expressed the vast energy requirement to lift the water from the ocean as equivalent to energy production from 12,000 high-end wind turbines — plus more to desalinate the water– which brings it into the realm of possibility.

“Nevertheless, the plan is almost – not quite – up there with building giant glass domes to house our cities or moving people to a terraformed Mars to escape the troubles people inflict on our planet. Giving the benefit of the doubt on the economic viability and physical practicality of this plan, it still seems filled with vast unintended consequences, as the authors seem to be aware. Some potential consequences could be devastating, some maybe even making the ice sheet mass balance situation worse.

“This ‘ideas’ paper was intended neither to calculate the full energy and economic cost of their plan, nor to evaluate the unintended consequences. Such an idea as this, now that it has been hatched, will be critically examined, no doubt, and it will gain its adherents and detractors. Considering the likely impracticality of this idea, when all is considered and evaluated carefully, and if the idea then is given up for dead, one unintended consequence might not die with it: this idea, now that it has hatched, may give gullible people and manipulative politicians and those with vested interests in fossil fuels a sense that we can just keep burning fossil fuels on an expanding scale; then if things get too bad climatically we can engineer our way out of trouble – hence, no worries. On the other hand, this work does a good job of showing how one large glacial system in Antarctica is poised very near the threshold between stability and runaway instability, and now may have been pushed over the edge by climate change.  

“How many other physical and biological Earth surface systems and human infrastructural and societal systems are similarly near a threshold for runaway collapse due to climate change? 12,000 windmills will not fix most of those. The visionary thinking we need most of all is what we can do to take our civilization off dependence on fossil fuels.”

Prof Andrew Shepherd, Director of the Centre for Polar Observation and Modelling at the University of Leeds, said:

“This is a stark reminder that events happening today will affect future generations. To avoid catastrophic sea level rise over the coming centuries, we have to somehow dump three times as much snow back onto Antarctica than has been lost in just a few decades due to ocean melting. But we just don’t have the technology to do that, and so it’s important to appreciate the scale of the challenge we are facing as it will make us think harder about dealing with the sea level rise that is bound to happen.”

*‘Stabilizing the West Antarctic Ice Sheet by surface mass deposition’ by Johannes Feldmann et al. was published in Science Advances at 7pm UK time on Wednesday 17 July 2019. 

Declared interests

Dr Kargel: I have no conflicts of interest regarding this story.

Dr Larter: I am UK Principal Investigator of the Thwaites Offshore Research Project (THOR), which is part of the International Thwaites Glacier Collaboration (ITGC), jointly funded by the UK Natural Environment Research Council and the US National Science Foundation.

Dr Smith: I have no links whatsoever with the group that’s done this, nor any competing work in the area.

No others received.