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DEEP PURPLE on the ice: algae are heating up Greenland

Purple algae are making the western Greenland Ice Sheet melt faster, as the algae darken the ice surface and make it absorb more sunlight. With an ERC Synergy Grant of €11 million, researchers from Aarhus University and two other European universities will examine the role of glacier algae in a warming climate.

The ERC (European Research Council) has awarded a Synergy grant to Alexandre Anesio at Aarhus University, Martyn Tranter at University of Bristol, UK, and Liane G. Benning at GFZ Potsdam, Germany.

The three professors have already helped change our understanding of why the ice darkens during the melt season by identifying the purple-pigmented ice algal blooms in the ice surface. The glacier algae in this area are pigmented deep purple to shield their vital elements from the intense UV radiation in sunlight.

And should the project name DEEP PURPLE make you think of the rock classic "Smoke on the Water", you are not wide of the mark.

There are now so many of these deep purple algae that they look as black as the soot from tundra fires. And they form a dark band that has been progressively growing down the western side of the Greenland Ice Sheet during the summer melt season for the last 20 years, causing increased melting of the darkening ice.

Just why these glacier algae grow so densely is not really known at the moment, and neither is whether they will grow in the new melt zones on the ice sheet surface, to the north and to the ice sheet interior, as the climate continues to warm.

Questions such as these need answering if future sea level rise is to be predicted accurately, since Greenland melt is a major driver of current sea level rise. 


Project DEEP PURPLE aims to answer these questions over the next six years, combining curiosity driven science about how the glacier algae grow and interact with their icy habitat, and societally relevant research into the processes that lead to ice surface darkening that are needed by ice melt modellers. 

The scientists will work around many different sites in Greenland, making measurements of

  • surface darkening,
  • glacier algae density,
  • how much soot and dust the algae trap on the surface
  • the physical properties of the melting ice surface

to finally understand, how biological darkening occurs, and to predict where and when it will occur in the future.

Amazing opportunity


This type of research needs the expertise of microbiologists, glaciologists and particulate biogeochemists, working in synergy, because only with a knowledge of all three aspects of melting ice surfaces can biological darkening be understood. DEEP PURPLE will host a team of 9 post doctoral researchers and 6 PhD students, along with the three principal investigators.

“This is an amazing opportunity to finally collect all the physical, chemical and biological measurements we need from around the Greenland Ice Sheet. It will also provide opportunities to perform field and laboratory experiments to understand the controls of the increasing amount of biological darkening that is occurring year by year in the Greenland ice sheet. Glaciers globally have similar processes, and the results of this project will also improve our understanding of the ice biome,” says professor and biogeochemist Alexandre Anesio from the Department of Environmental Science at Aarhus University.

Further information:


Please read about the projects Dark Snow og Black and Bloom, that paved the way for DEEP PURPLE.

...and read about Alexandre Anesio’s research in Greenland in this article in The Guardian.


Professor Alexandre Anesio
Department of Environmental Science - Environmental Microbiology and Circular Resource Flow
Aarhus University

Mail: ama@envs.au.dk
Mobile: +4522568980