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ERL: massive ice wedges in Yedoma permafrost amplify carbon loss
Insight: massive ice wedges in Yedoma permafrost amplify carbon loss
by environmentalresearchweb, October 1, 2013
Yedoma permafrost stores about a third of all
organic carbon in circum-Arctic permafrost and is characterized by
massive ice wedges that make up around 50% of the total volume. We
investigated how ice wedge thaw affects Yedoma permafrost and found that
organic matter engrained in the ice wedges can degrade Yedoma carbon.
The findings, published in Environmental Research Letters (ERL), highlight how this type of permafrost thawing could significantly contribute to climate change.
When permafrost thaws, the carbon contained can degrade and be released
into the atmosphere. Due to the sheer size of the carbon pool stored in
permafrost (twice as much carbon as is currently in our atmosphere), the
size of the positive feedback can be substantial. Yedoma permafrost is
widespread in Siberia and parts of Alaska. It was formed during glacial
times and has remained frozen ever since.
In a previous study, we showed that the organic matter in Yedoma thaw
streams degrades rapidly, and more than a third of the carbon can be
lost after just 14 days. We hypothesized that ice wedge melt might play a
role in the rapid decomposition of Yedoma and tested this by setting up
degradation experiments with varying ratios of ice wedge melt water and
river water.
Through compositional and enzymatic analyses we found that
the organic matter in ice wedges is enriched in low-molecular weight
compounds and has a low initial phenolic content. This seems to serve as
an easily available substrate that speeds up the degradation of the old
carbon stored in Yedoma.
The composition of ice wedge-engrained organic matter and the fragile
nature of the ice wedges in Yedoma underline the particularity of this
type of permafrost and its especially strong ability to generate
greenhouse gases upon thaw.
About the author: Jorien Vonk is a
postdoc in the Department of Earth Sciences at Utrecht University in The
Netherlands. This work was carried out as part of The Polaris Project.
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