Expired · 26th October 2009
As the vast expanse of the Arctic continues to thaw – not only the ice but the permafrost, too – concern is shifting from the wellbeing of polar bears to the impact on Earth's climate. People who glibly note that they could happily live with a little more warmth in northern latitudes might consider the implications.
"I'm shocked, truly shocked," said Katey Walter a geologist from the University of Alaska who recently visited Siberia. Since her last visit in 2006, lakes are five times bigger and methane is bubbling out of them. "It's unprecedented," she says, using a word that is applied with increasing frequency to the warming trend in the far north.
And the events in Siberia are only part of a larger problem. Melted sea ice exposes heat-absorbing water to the sun's warmth – instead of ice reflecting 90 percent of the sun's energy back into space, open water absorbs 94 percent of it. This warming alters ocean currents and wind patterns, both of which accelerate the melting of sea ice. Furthermore, this melting also encourages inland thawing – up to 1,500 kilometres from shorelines.
Melting sea ice is not just a handicap for polar bears hunting for food. Over the last three centuries, the Arctic's average temperature increase has been about 3.0°C compared to 0.8°C for the rest of the planet. In some areas inshore from melted sea, the increase has been 5.0°C. Alaska, Greenland, Scandinavia and northern Canada all join Siberia in registering the greatest warming on the planet from climate change. When considering that about 25 percent of the land surface of the northern hemisphere is composed of carbon-rich permafrost, a big problem becomes bigger.
Permafrost contains frozen organic material from the last Ice Age, and huge amounts of methane. Science is now beginning to quantify the amount of this stored carbon. Dr. Edward Schuur of the University of Florida calculates that the Arctic contains 1.6 trillion tonnes, three times original estimates – as much as is stored in all the world's soils and twice as much contained in the atmosphere. A thawing Arctic threatens to release this carbon as greenhouse gases. Schuur calculates that warming trends could begin releasing 1 billion to 3 billion tonnes per year, with a total of 100 billion tonnes by the end of this century. (As a comparison, all the cars and light trucks in the United States release only 300 million tonnes per year.) Such a trend could easily warm the planet by 3.0°C and the Arctic by 10.0°C. Should this happen, a so-called tipping point would probably be reached long before the end of this century, and a positive feedback loop would create an unstoppable process of melted permafrost, released carbon, increased warming, and then more melting, more carbon and more warming.
A newly considered facet of this uncontrolled warming is simply the microbial breakdown of thawed organic material. Not only does decomposition increase the amount of carbon released into the atmosphere but the actual activity of the microbes produces heat, further accelerating an already accelerating process.
Now add the word talik to the vocabulary of permafrost melt. It is a layer of thawed water trapped between the frozen winter ice above the permafrost below. Not only does it increase the melting of the permafrost but it creates low-oxygen conditions that aid the release of methane when the winter ice thaws.
Methane is a gas about 24 times more "warming" than carbon dioxide, and is emitted during the anaerobic decomposition of organic material in the permafrost. Methane also exists as methane hydrates, trapped methane that is frozen into solid form. Believed to exist in vast quantities beneath the Arctic Ocean, it is held in place by cold temperatures and high pressures. If the temperature of the ocean rises or if warmer currents disturb its containment, huge quantities of these methane hydrates could be released into the atmosphere, further accelerating the global warming process.
Scientists know that the methane composition in the Earth's atmosphere has doubled since pre-industrial years. But it has remained fairly stable during the last two decades – until 2007. Then, suddenly, "several million tonnes of mysterious methane have entered the atmosphere" (New Scientist, Mar. 28/09). Remote sensors suggest this methane is coming from northern latitudes. On-site reports from across the Arctic note methane bubbling from lakes and muskeg, a further indication that permafrost melting might be occurring faster than predicted in previous climate models.
And the climate change we get is not necessarily what we commonly expect. For example, if the planet is warming, why have North America and China been getting particularly cold and snowy winters for the last several years? According to James Overland, an oceanographer at the Pacific Marine Environmental Laboratory in Seattle, the warming Arctic is drawing an unusual flow of moist air into Siberia, chilling it and then distributing the precipitation in the Arctic and across both the Asian and North American continents.
More snow is transforming the Arctic from a cold, high-latitude desert to a place that is more temperate and moist. And this means more summer melt. Arctic rivers are pouring about 10% more water into the northern ocean than 50 years ago. This additional fresh water, together with melting glacial ice, is reducing the differential of temperature and salinity that drives the thermohaline current, the great ocean conveyor belt that distributes heat around the world. Even a slowdown in this current could disrupt or even collapse the Asian monsoons, a seasonal rain on which about 2 billion people depend for food production (Ibid.). Climate changes in the Arctic mean climate changes everywhere else.
Polar bears, for all their lumbering beauty and profound significance as an iconic predator, may be the least of our worries when we think about melting ice and a warming Arctic.