A new study found that a 2018 proposal to cover Arctic sea ice with layers of tiny hollow glass microspheres (HGMs) would instead warm the climate and speed the loss of sea ice.
The 2018 proposal argued that the repeated spreading of HGMs on young sea ice would increase reflectivity, which would protect the ice from the sun and allow it to mature into “highly reflective, multi-year ice.” The researchers concluded that a layer of 65-micrometer-wide glass spheres spread about five beads deep could increase the reflectivity and thickness of Arctic sea ice.
Melinda Webster, a polar scientist at the University of Alaska Fairbanks Geophysical Institute, and colleague Stephen G. Warren of the University of Washington, reject the science behind the 2018 proposal.
They argue that placing layers of white HGMs onto Arctic ice would instead darken the surface, warm the climate and accelerate the loss of sea ice. They claim that the 2018 study did not account for the varying surface type reflectivities or variations that would occur depending on the time of year of microspheres application.
“Our results show that the proposed effort to halt Arctic sea-ice loss has the opposite effect of what is intended,” Webster writes. “And that is detrimental to Earth’s climate and human society as a whole.”
Webster and Warren tested the claims of the 2018 study, which only considered thin sea ice with minimal snow cover. The duo instead studied changes in solar energy across eight sea ice conditions at different times of the year. They also considered seasonal sunlight, the intensity of solar radiation at the surface and at the top of the atmosphere, cloud cover and how the microspheres reacted with sunlight.
They based their research on the same type of microspheres used in the 2018 study and on the same number of layers. The microspheres used in the 2018 study are 3M’s Glass Bubbles K1, which are designed for use in a variety of applications, including oil and gas drilling operations and as an additive in lightweight wall repair compounds.
The 2018 study claimed that layers of HGMs can make new, thin ice more reflective. However, Webster and Warren found that the effect would be minimal because thin ice mostly occurs in autumn and winter when there is little sunlight. Thin ice soon gets covered by falling and drifting snow, which increases surface reflectivity.
The duo discovered that the months that are seen as favorable for the application of HGMs (March, April, May and June) are actually the worst months to apply microspheres. Despite the summer melt ponds that form across the sea ice as solar energy increases during late spring and early summer, which would seem like an ideal target for the use of hollow glass microspheres, covering these ponds with microspheres will not achieve the desired effect.
“Because hollow glass microspheres absorb some sunlight, spreading them onto sea ice would darken bright surfaces such as snow-covered ice,” Webster and Warren write. “The net result is the opposite of what was intended: spreading hollow glass microspheres would warm the Arctic climate and speed sea-ice loss.”
Though HGMs reflect a significant fraction of sunlight, a thin layer of glass beads still absorbs about 10% of energy from the sun’s rays, which is enough to hasten warming in the Arctic. The researchers found that if fully non-absorbing microspheres, meaning they absorb 0% rather than 10% of the incoming solar energy, were developed, they might be able to cool the Arctic. But that might still not solve the problem.
That’s because it would take about 360 million tons of hollow glass beads annually to prevent ice melt and cool the climate. And that’s assuming the non-absorbing microspheres could be manufactured and dispersed without contamination or other unintended effects.
“The use of microspheres as a way to restore Arctic sea ice isn’t feasible,” Webster writes. “While science should continue to explore ways to mitigate global warming, the best bet is for society to reduce the behaviors that continue to contribute to climate change.”