In summer, Arctic waters become an ever-evolving mosaic of bare ice, meltwater ponds and open water. In June and July 2010, Bonnie Light of the University of Washington in Seattle and her colleagues measured the optical properties of ice floes formed during the previous winter in the Chukchi Sea to see how changes in ice cover affect the amount of solar radiation that reaches the ocean.

The transmission of sunlight through ice covered by meltwater ponds was generally an order of magnitude greater than that through thicker bare ice. But horizontal propagation of light in the vicinity of melt ponds, caused by scattering in the ice, led to unexpectedly high rates of light transmittance under the surface of bare ice.

Increased summer melting and thinning may substantially raise the amount of sunlight reaching the upper ocean, so this complexity could have profound effects on biological production and ocean chemistry.

Credit: B&C ALEXANDER/ARCTICPHOTO

Geophys. Res. Lett. 10.1029/2011GL049421 (2011)