News Release 

Algal darkening of Greenland ice sheet

Proceedings of the National Academy of Sciences

A study examines how algae found in glaciers darken ice sheets. Processes that darken the Greenland Ice Sheet (GrIS) accelerate surface melt, but the potential for microalgae to drive such darkening is unclear. To determine how specialized glacier algae are able to thrive on and darken the GrIS, Christopher Williamson and colleagues analyzed samples of algal blooms that grew on the GrIS surface between July and August 2016. By analyzing the algae's biooptical properties, the authors determined that secondary phenolic pigmentation allows the algae to survive under the extreme surface ice conditions of intense light and low temperatures. The authors also found that the pigments absorb damaging UV-A and UV-B light, providing shading to the underlying, low-light-adapted chloroplasts while simultaneously capturing energy that can be used to produce meltwater around the algal cells. By measuring pigment profiles of algal assemblages and modeling algal biomass within GrIS surface ice throughout the 2016 ablation season, the authors determined that the presence of glacier algae in surface ice drives widespread darkening of the southwestern GrIS during summer melt months. The findings suggest that the mechanisms needed for algal survival in the extreme environment of the GrIS also drive the ice sheet's darkening, contributing to its melt, according to the authors.

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Article #19-18412: "Algal photophysiology drives darkening and melt of the Greenland Ice Sheet," by Christopher J. Williamson et al.

MEDIA CONTACT: Christopher Williamson, University of Bristol, UNITED KINGDOM; tel: +44 (0) 117 42 82 366; email: c.williamson@bristol.ac.uk

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