Webster, M. A., & Warren, S. G. (2022). Regional geoengineering using
tiny glass bubbles would accelerate the loss of Arctic sea ice. /Earth's
Future/, 10, e2022EF002815. https://doi.org/10.1029/2022EF002815
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022EF002815
*Abstract*
Arctic sea ice might be preserved if its albedo could be
increased. To this end, it has been proposed to spread hollow glass
microspheres (HGMs) over the ice. We assess the radiative forcing (RF)
that would result, by considering the areal coverages and spectral
albedos of eight representative surface types, as well as the incident
solar radiation, cloud properties, and spectral radiative properties of
HGMs.
HGMs can raise the albedo of new ice, but new ice occurs in autumn and
winter when there is little sunlight. In spring the ice is covered by
high-albedo, thick snow. In summer the sunlight is intense, and the snow
melts, so a substantial area is covered by dark ponds of meltwater,
which could be an attractive target for attempted brightening. However,
prior studies show that wind blows HGMs to the pond edges.
A thin layer of HGMs has about 10% absorptance for solar radiation, so
HGMs would darken any surfaces with albedo >0.61, such as snow-covered
ice. The net result is the opposite of what was intended: spreading HGMs
would warm the Arctic climate and speed sea-ice loss.
If non-absorbing HGMs could be manufactured, and if they could be
transported and distributed without contamination by dark substances,
they could cool the climate. The maximum benefit would be achieved by
distribution during the month of May, resulting in an annual average RF
for the Arctic Ocean of -3 Wm^-2 if 360 megatons of HGMs were spread
onto the ice annually.
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