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.

Ice wedge sampling

 

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.

Related links:

• Dissolved organic carbon loss from Yedoma permafrost amplified by ice wedge thaw, J. E. Vonk et al., 2013. Environ. Res. Lett., 8, 035023.
• ERL Focus on Changing Permafrost in a Warming World: Observation and Implication

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.

 http://environmentalresearchweb.org/cws/article/news/54832