UNIVERSITY PARK, Pa. – The brownish-grey algae that darken the Greenland ice sheet in summer cause the ice to melt faster, but only recently have scientists measured these blooms in the field, and only at few sites. To measure algal blooms across large regions and understand their effects on melting over time, scientists are now turning to space.
“Scientists go into the field and sample one or two spots where these algal blooms occur, but we don’t really know how they change over time or over a large region,” said Shujie Wang, assistant professor of geography at Penn State. “To solve this problem, my research team and I borrowed the methodology used to measure algae in water, which uses ocean color satellites and has a long history.”
The algae that bloom on water differ from those that bloom on ice, but both species contain chlorophyll-a, which has a distinct reflected near-infrared radiation signature that satellite sensors can detect.
Mapping glacial algae over space and time can give researchers insights into how algae affect albedo, said Wang, who conducted the research as a postdoctoral scholar at Columbia University’s Lamont-Doherty Earth Observatory under the supervision of Marco Tedesco, Lamont research professor. Albedo is a parameter that says how much incoming solar radiation is reflected by a surface.
“Albedo is crucial for understanding how ice melts and what will happen in the future to the contribution of Greenland to sea level rise,” explained Tedesco. “Little is known of the effects of algae on this, and the work by Shujie is pioneering in this regard. It was amazing to have her as a postdoctoral scientist.”