Modified floating wood could seed the formation of new sea ice in the Arctic, helping counteract the rapid decline of ice coverage due to global warming.
The area of the Arctic Ocean covered by ice is shrinking as the climate warms, and it has been projected that the region will see its before 2030. The loss of ice leads to a vicious cycle; because the exposed water is darker than ice, it absorbs more of the sun鈥檚 heat, warming the water further and making it increasingly hard for ice to reform. This has led people to suggest various geoengineering plans to refreeze the water both in the Arctic and Antarctica.
Now, at Purdue University in West Lafayette, Indiana, and her colleagues are proposing modifying wood to help it seed the formation of new ice.
Advertisement
鈥淲e choose wood because it鈥檚 a natural material,鈥� says Li. 鈥淵ou see a lot of floating wood in ocean water and it raises much less of an environmental concern than things made of artificial materials.鈥�
To create the modified material, which they call ice-wood, the researchers took a 10-centimetre-square, 1.5-centimetre-thick piece of American basswood (Tilia americana) and cut a small chunk out of the middle. This chunk was placed on a hotplate so that one side carbonised, while the larger piece was treated with hydrogen peroxide and heat, removing much of a polymer called lignin. The two pieces were then put back together.
Lignin gives wood its colour, so removing it makes that part of the wood whiter and better at reflecting light. The idea is that when the ice-wood floats in the sea, water is drawn up through natural microchannels. Sunlight then warms the dark, carbonised part of the surface, making the water there evaporate, after which it recondenses on the colder, whiter part of the surface.
The height of the ice-wood and its white surface allow it to stay colder than the water, says Li. 鈥淭he wood essentially sucks water from the bottom and pumps it to the top, where there is a sub-freezing platform, where ice begins to form.鈥�
During tests in ponds with water kept at about 2掳C (36掳F), the top of a piece of floating ice-wood stayed below freezing, even when the ambient air temperature reached between 7掳C and 8掳C (44.6掳F and 46.4掳F). 鈥淚t acts like an ice seed 鈥� we see ice start to form from the edge and extending to the other areas,鈥� says Li.
But this probably wouldn鈥檛 work to seed new ice in the Arctic summer because the air temperature typically reaches around 10掳C, says at the University of Washington in Seattle.
Li and her colleagues also modelled how the use of ice-wood throughout the Arctic from 2005 to 2022 would have affected the amount of sea ice. By the melting season of 2022, their model indicates that covering the oceans and coastlines of the Arctic with ice-wood would have boosted the ice growth rate by 0.3 centimetres a day and cut sea surface temperatures there by about 3掳C (5.4掳F) compared with real 2022 levels.
Covering the whole Arctic isn鈥檛 realistic, but Li suggests that larger pieces of ice-wood could be used around coastal regions, where Indigenous people rely on ice to hunt fish, to accelerate the ice coverage in winter and reduce ice loss in summer.
Scaling up the process shouldn鈥檛 be a problem, says Li. As well as being environmentally friendly, wood is a cheap material, and the process of removing lignin is already done at large scales in factories to make white paper, she says.
Being able to access the chosen regions of the Arctic will also be important, says at the University of Cambridge, who is investigating various ways of restoring Arctic ice. He would like to know how this approach will stack up against other proposed interventions, such as pumping seawater onto snow to encourage new ice to form.
But a big question remains about whether our focus should be on geoengineering approaches to prevent ice loss or on slowing the climate change that is causing it.
鈥淚 find it strange to put so much energy into these ideas when we already know what is needed: reduced carbon dioxide emissions,鈥� says at University College London.
Research Square
