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Cosmopolitan snow algae accelerate melting of Arctic glaciers
Phys.org,
22
June, 2016
The
role of red pigmented snow algae in melting Arctic glaciers has been
strongly underestimated, suggests a study to be published in Nature
Communications on June 22. White areas covered with snow and
ice reflect sunlight; the effect is called albedo. It has been known
for quite some time that red pigmented snow algae blooming on icy
surfaces darken the surface which in turn leads to less albedo and a
higher uptake of heat. The new study by Stefanie Lutz, postdoc at the
German Research Centre for Geosciences GFZ and at the University of
Leeds, shows a 13 per cent reduction of the albedo over the course of
one melting season caused by red-pigmented snow algal blooms.
"Our
results point out that the "bio-albedo" effect is important
and has to be considered in future climate models", says lead
author Stefanie Lutz.
The
red snow phenomenon occurs mainly in warm months. During late spring
and summer, thin layers of meltwater form on ice and snow in the
Arctic and on mountains. Liquid water and sunlight are crucial for
the growth of snow algae; over the winter season they fall into a
dormant state.
In
their study, the team led by Stefanie Lutz and Liane G. Benning
investigated the biodiversity of snow algae and other microbial
communities using high-throughput genetic sequencing. They took about
forty samples from 21 glaciers in the Pan-European Arctic. The
sampling sites ranged from Greenland over Iceland and Svalbard to the
north of Sweden.
Together
with UK colleagues they found a high biodiversity within the
bacteria, depending on the locations they lived, whereas the
biodiversity of the snow algal communities was rather uniform. In
other words: Throughout the Arctic regions, it is most probably the
same algal species that cause red snow and thus accelerate melting.
The blooming leads to a runaway effect: The more glaciers and snow
fields thaw the more algae bloom which in turn results in a darkening
of the surface which again accelerates melting. Liane G. Benning,
head of the GFZ's section "Interface Geochemistry", says:
"Our work paves the way for a universal model of algal-albedo
interaction and a quantification of additional melting caused by
algal blooms."
For
years, "bio-albedo has been a niche topic", says Daniel
Remias, biologist at the Fachhochschule Wels, Austria. The snow algae
specialist comments on the study: "For the first time ever,
researchers have investigated the large-scale effect of
microorganisms on the melting of snow and ice the Arctic."
Remias visited the GFZ for an international snow algae meeting
organized by Liane G. Benning.
He
stresses the interdisciplinary approach of the project: "Steffi
Lutz' and Liane G. Benning's study for the first time combines
microbiological and genetic analyses of red snow algae with
geochemical and mineralogical properties as well as with the albedo
of their habitat." An international, UK led team, including the
GFZ's researchers will work this summer on the Greenland Ice Sheet
where currently a record-breaking melting rate due to high
temperatures is observed. Steffi Lutz, Liane G. Benning and UK
colleagues will investigate whether and to what extent pigmented
algae contribute to the record melting.
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