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Siberian Permafrost

Siberian Permafrost Cracks formed from permafrost thaw.
Photo Credit: Dentren at en.wikipedia [CC-BY-SA-3.0 or GFDL], via Wikimedia Commons

Once the Earth warms to a critical temperature, permafrost in Siberia will melt, releasing massive amounts of carbon.


Transcript

Siberia faces a meltdown. I’m Bob Hirshon and this is Science Update.

Even Siberia, one of the coldest places on Earth, is getting warmer. And once it hits a certain temperature, it could release over a billion more metric tons of carbon that’s now locked in frozen groundwater called permafrost.

Oxford University geochemist Anton Vaks and his colleagues confirmed this by studying rock formations, called stalagmites and stalactites, in Siberian caves.

Vaks:
And the stalagmites and stalactites cannot grow if the water above the cave is frozen.

Using geological dating, the researchers found that the stalactites and stalagmites formed almost entirely during a warm period about 400,000 years ago. Back then, global temperatures averaged less than one degree Celsius above today’s. Vaks says that suggests there’s a tipping point for melting the permafrost, and we’re getting closer and closer to crossing that line. I’m Bob Hirshon for AAAS, the Science Society.


Making Sense of the Research

It's only been a little more than 150 years since global temperatures started being measured reliably on a day-to-day basis. But to understand the Earth's climate, scientists need to trace back millions of years. To do that, they rely on evidence etched into the Earth itself.

There are many forms of what scientists call “paleoclimate data,” or information about climate in prehistoric times. In this case, scientists studied stalactites and stalagmites: cone-shaped rock formations in caves that either hang from the ceiling or rise up from the ground. And they looked in a part of Siberia, in northern Russia, that's so cold that the soil has been permanently frozen for hundreds of thousands of years. This frozen soil is called permafrost.

Some caves in this part of Siberia feature stalactites and stalagmites, which form when water drips from cave ceilings. In order for this to happen, the water has to be liquid, which means the local temperature would need to rise above freezing for a significant length of time. Therefore, by determining when the stalactites and stalagmites formed, the researchers can identify the last time temperatures in this part of Siberia rose above freezing.

The researchers determined the age of the stalactites and stalagmites using radiometric dating, a common scientific tool that measures naturally occurring radioactive elements that slowly decay over time. In the most basic sense, the more abundant these radioactive elements are, the younger the material is. 

Using this technique, the researchers determined that the stalactites and stalagmites formed almost entirely in a relatively short time period about 400,000 years ago. Other paleoclimate research has shown that at that time, the Earth then was warmer than it is today. However, because of human-made carbon emissions, global temperatures have been rapidly rising over the past century. At the current rate, they may soon reach a point where Siberian permafrost starts to melt again.

Why does this matter? First, melting permafrost releases more greenhouse gases, including carbon dioxide and methane, into the atmosphere. This region alone could release over a trillion tons of greenhouse gases, making global temperatures rise even faster. Second, power lines, roads, buildings, railroads, fuel plants, and other human-made structures are built on permafrost in Siberia and elswhere in the world. If the ground melts, it could cause these structures to buckle and collapse, creating crises far beyond the immediate area. And if the permafrost does begin to melt, it will be difficult or impossible to reverse.

Now try and answer these questions:

  1. What is permafrost? 
  2. What are stalactites and stalagmites? What can they tell us about permafrost in Siberia?
  3. How did the researchers determine that the Siberian permafrost last melted about 400,000 years ago?
  4. What will be some of the consequences if the permafrost melts?
You may want to check out these related resources:

Other research on prehistoric climate change is described in the Science Updates Giant Snake and Early Climate Change.

For another perspective on climate change, see the two-part video Climate Change Research in California, made by Danielle Balistrieri, a college student who participated in grasslands research in California.

The Science Update Flowers and Rainfall describes the effect flowering plants have had on shaping the Earth's climate.


Going Further


For Educators

Other research on prehistoric climate change is described in the Science Updates Giant Snake and Early Climate Change.

For another perspective on climate change, see the two-part video Climate Change Research in California, made by Danielle Balistrieri, a college student who participated in grasslands research in California.

The Science Update Flowers and Rainfall describes the effect flowering plants have had on shaping the Earth's climate.


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