Glass microspheres are not the solution to Arctic sea ice preservation

A proposal to cover Arctic sea ice with layers of tiny hollow glass beads as thick as a human hair would actually accelerate sea ice loss and warm the climate, rather than creating thicker ice and lowering temperatures, as advocates claim, according to a new study. .

By reflecting most of the sun’s energy back into space, sea ice helps regulate ocean and air temperatures and affects ocean circulation. Its area and thickness are crucial for the Earth’s climate. A 2018 study claimed that repeatedly spreading hollow glass microspheres on young Arctic sea ice would increase its reflectivity, protect it from the sun and allow it to develop into multi-year ice with high reflectivity.

A new study rejects that claim, finding instead that placing layers of white hollow glass microspheres on Arctic sea ice would actually darken its surface, accelerate sea ice loss, and further warm the climate. The new study was published today in the journal AGU The future of the Earth.

According to a 2018 study, five layers of microspheres reflect 43% incoming sunlight and allow 47% to pass through the layers of spheres to the surface below. The remaining 10% will be absorbed by the microspheres – enough to accelerate the melting of ice and further warm the Arctic atmosphere, a new study shows.

“Our results show that proposed efforts to stop Arctic sea ice loss are having the opposite effect than intended,” said Melinda Webster, a polar scientist at the University of Alaska Fairbanks Geophysical Institute and an author of the study. “And that’s bad for the Earth’s climate and human society as a whole.”

Webster and his colleague Stephen G. Warren of the University of Washington calculated changes in solar energy under eight common conditions of the Arctic sea ice surface, each with a different reflectivity. They also took into account seasonal insolation, the intensity of solar radiation at the surface and in the upper atmosphere, cloudiness and how the microspheres responded to sunlight. They based their study on the same type of microspheres used in the 2018 study and the same number of layers.

The 2018 study did not fully account for the different type of surface reflectivity or variations that would occur depending on the time of year the microspheres were applied. A layer of microspheres can increase the reflectivity of thin new ice, which is naturally dark, but the effect will be minimal because thin ice is most likely to form in the fall and winter when sunlight is scarce. Thin ice is soon covered by falling snow, which increases the reflectivity of the surface.

In the spring, solar energy increases with the return of the polar day. At this time, most of the sea ice is covered with deep reflective snow. Due to the high reflectivity of snow, the microspheres darken the surface of the snow, increasing solar absorption and, accordingly, accelerating its melting – an effect opposite to the intended one.

The months that seem most favorable for the application of microspheres – March, April, May and June, when sunlight increases – are actually the worst months for the application of microspheres.

At the end of spring and beginning of summer, floating ponds begin to form on sea ice as solar energy increases. Ponds would seem like an ideal target for using hollow glass microspheres because they are dark and have low reflectivity.

But covering water reservoirs with microspheres will not achieve the desired effect. An experiment on a Minnesota pond in a 2018 study showed that the wind blows the floating spheres to the edge of the pond, where they clump together like pollen.

Totally non-absorbable microspheres, meaning they absorb 0% instead of 10% of what comes in solar energy, still may not solve the problem for a simple reason: quantity. To prevent the melting of the ice and the cooling of the climate, about 360 million tons will be needed once a year. And this is assuming that the nonabsorbable microspheres can be produced and dispersed without contamination or other unwanted effects.

“Using microspheres as a way to restore Arctic sea ice is not feasible,” Webster said. “While science must continue to explore ways to mitigate global warmingthe best option for society is to reduce the behaviors that continue to contribute to climate change.”