VIDEO: NASA measures sea ice at the peak of melt.
The current Arctic ice cap rarely exceeds 2-3 m in thickness and it is constantly being eroded as a result of climate warming. Some scenarios suggest that the late-summer Arctic will be ice-free by the 2030s, if not sooner. Losing this summer sea ice would have a profound effect on Earth's climate, accelerating temperature increases, whilst preventing the loss of Arctic ice that will inevitably arise from climate change (or even increasing the amount of Arctic ice) would have a measurable impact on slowing temperature increases worldwide.
In the article Arctic Ice Management published in the journal Earth's Future, the ASU scientists outline a geoengineering proposal to create more ice during the Arctic winter by pumping water directly to the surface where it can freeze more rapidly, thickening the ice. This idea is not new but the implied scale of the technique (which involves the production of ice over millions of square kilometres) may have discouraged further investigation.
A network of wind-powered pumps
Since half the Arctic Ocean is characterised by ice that is less than 1.5 m in thickness on average, it is estimated that the addition of 1 m of ice each winter throughout 10% of the Arctic Ocean would offset the current decrease in ice thickness observed since 2000. Increasing the ice thickness by 1.0 m requires pumping about 1.3 m of water, equivalent to about 1.4 m of ice. The proposal states that a wind-powered pump mounted on a large buoy could perform the function of capturing wind energy to pump seawater to the surface. The basic components of the device would include:
- a large buoy;
- a wind turbine and pump, drawing up seawater from below the ice;
- a tank for storing the water; and
- a delivery system that takes the water periodically flushed from the tank and distributes it over a large area.
There is enough wind power in the Arctic for a single wind turbine with 6 m diameter blades to pump 1.3 m of water over about 0.1 km2 over the Arctic winter. About 10 million wind-powered pumps would therefore be required to cover 10% of the Arctic Ocean, or 1 million devices per year assuming an implementation period of 10 years.
These devices would have to be manufactured and delivered to the Arctic Ocean and maintained in the harsh Arctic environment. The engineering challenges of this task are evident but an equally important question concerns its financial feasibility.
How much would it cost?
In the ASU scientists' estimates, the cost to manufacture and deploy each pumping device is around $50,000. To deploy the devices over 10% of the Arctic over 10 years would therefore cost about $50 billion/year. To deploy such devices over the entire Arctic would require about $5 trillion over 10 years, or about $500 billion/year.
To put these costs into perspective the scientists point out that even $500 billion/year represents only 0.64% of current world gross domestic product (GDP) of $78 trillion or 2.7% of the current US GDP of $18.5 trillion. Thus, they say, that while clearly expensive, constructing and deploying the pumping devices over 10% of the Arctic, at $50 billion/year, is actually economically quite tractable.
They conclude that winter ice thickening by wind-powered pumps should be considered and assessed as part of a multi-pronged strategy for restoring sea ice and arresting the strongest feedbacks in the climate system. Questions about the feasibility of the device and its local effects would probably be best solved by building a prototype for experimentation in the field.
