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Observing the scars of the Arctic thaw

June 30, 2009 By Jane Qiu This article courtesy of Nature News.

Ecologist Breck Bowdon talks about the consequences of thawing permafrost in Alaska.

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Last week marked the start of a US$5 million project to study the effects of thawing permafrost on ecosystems in the Arctic. Based at the Toolik Field Station in northern Alaska and sponsored by the US National Science Foundation, the project will look at the impact of thermokarsts — the scars and pits left behind as melt water from permanently frozen ground leaks away, and soil and rock collapses in its wake.

Breck Bowden, an aquatic ecologist at the University of Vermont, Burlington, is the head of the project team, which includes 16 principle investigators. Nature News caught up with Bowden at Toolik to ask him about his fascination with thermokarsts and what the project will tell us about the future of the Arctic.

How did you get interested in thermokarsts?

It dates back to a serendipitous discovery in 2003. My colleagues and I were flying over the high Arctic in search of research sites. We noted that the Toolik River was brown and muddy, which was odd as it hadn't rained recently. As we went further upstream, we came to a tiny stream that was washing tons of thermokarst sediments into the river. We were astounded how this tiny feature was influencing the river 40 kilometres downstream. The volume that had been displaced was enough to smother the bottom of the entire river. The sediments would release a lot of nutrients normally locked up in permafrost into freshwater cycles. That's got to have a significant impact on the ecosystem.

Why is it important to study permafrost and thermokarsts?

The ice in permafrost provides an important physical structure for the frozen soil. Once that ice disappears, the soil will collapse like a failed soufflé. If this occurs on a slope, there could be a major landslide. Permafrost thaw makes a large stock of previously frozen organic carbon available to microbes through disturbances, such as thermokarsts, resulting in the production of methane, a potent greenhouse gas. It also releases nutrient materials, such as nitrogen and phosphate, and could cause major changes in vegetation. This is a particularly important issue now because the Arctic is getting warmer, which poses a great threat to permafrost in the region.

What aspect of the project are you concentrating on?

My long-term interest is on what goes on in streams, especially carbon fixation by plants and how nutrient availability affects this primary-production process, as well as its connection with what happens on the land.

As water moves through thermokarsts, it picks up sediments and nutrients that are normally locked up in permafrost. We want to know how this affects the oxygen and nutrient levels in the streams, and how carbon, nitrogen and phosphate are processed and used by the entire system.

Why is it important to study streams?

They are like blood vessels of the human body, and connect land, rivers and lakes, and ultimately the ocean. Streams are also important in their own right. For example, they nourish fish production, providing a key source of food for some communities. Only when we have a full understanding of what goes on in streams and their responses to disturbances will we be able to synthesize what goes on across the entire landscape.

How have thermokarsts in Alaska changed over the past decades?

The question is whether the rate of thermokarst formation is greater now than in the past. We now have strong evidence that this is the case. In the past few decades, thermokarst incidents have doubled in some parts of the Alaskan Arctic. This correlates well with the doubling of permafrost temperature and a decrease in the stability of the tundra surface in the region. So the warming of the Arctic seems to be accelerating thermokarst formation. This is a strong indicator that things are changing in the Arctic and has provided an exciting opportunity to watch this process unfolding in front of us.

How have permafrost thaw and thermokarsts affected life in Alaska?

They have affected different places in different ways. For example, a combination of reduced sea ice and permafrost thaw has exacerbated the erosion of the coastal village of Shishmaref. The houses were falling into the ocean and the village, which had been inhabited for 400 years, was forced to relocate. Elsewhere, the sediments from a massive thermokarst have dammed the Selwik River and are affecting the fish population and threatening the livelihood of nearby villages. If the warming trend persists, more and more these incidences will occur.

What should people living in permafrost areas be doing to adapt to these changes?

The options are rather limited. They could adapt by fishing in rivers that are not affected by thermokarsts; they could move to areas without permafrost threats, which is highly costly. Once permafrost fails, there is no engineering solution to correct that situation. The best way to deal with thermokarsts is to prevent them from happening in the first place. This immediately raises a much bigger question about what has been driving the warming in the Arctic — ultimately the production of greenhouse gases on a global scale. The world has to work together to cut down man-made greenhouse gas emissions.

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