There is fresh speculation that a sinister substance lies beneath the vast ice sheets covering most of Antarctica, something that could contribute to (and possibly accelerate) the process of global warming.
If you’ve already read about concerns of melting permafrost in the Arctic regions, you’re already familiar with this potential nemesis: methane. Methane is a simple organic molecule (the chemical formula is CH4, if you’re curious or like to collect scientific trivia for cocktail parties). Methane normally exists as a gas, and is a rather potent greenhouse gas. In fact, a single molecule of methane is approximately 25 times more potent as a greenhouse gas compared to carbon dioxide. Carbon dioxide gets a lot of attention because there is more of it in the atmosphere. But, methane levels are rising due to human activity. Between 1750 and 2008, levels of methane in Earth’s atmosphere rose by over 150%. While methane gas makes up a tiny fraction of the atmosphere, there are concerns that its presence will accelerate the process of global warming.
The historic concerns with methane lies in the north, beneath the Arctic tundra that dominates northern Canada, Alaska, and Siberia. A simple glimpse at a globe will confirm that currently the Northern Hemisphere has taken the lion’s share of the land. Much of that land in the far north has permafrost beneath its soil. But, as the Arctic warms (faster than the rest of the planet, as I’ve noted recently), there is evidence that the permafrost is melting due to climate change. As the Arctic absorbs more and more heat, there are even fears that the melting trend for permafrost may accelerate.
The fears for melting permafrost lie in its contents. Many microbes can generate simple methane as a by-product of metabolizing organic matter, particularly in environments where oxygen is rare or nonexistent. As a result of these biological processes carried out over millennia, scientists believe vast amounts of methane have accumulated from these microbial digestion events, and remained locked frozen within the ground. The liberation of this methane (as permafrost melts) could not only contribute to global warming, but potentially accelerate it, especially since methane is among the most potent and destructive of greenhouse gases in terms of its heat-trapping potential.
In the southern hemisphere, many had thought a different paradigm was at work. After all, the southern hemisphere contains less land and, with the exception of Antarctica itself, that land is not close enough to the polar latitudes to create a “permafrost problem.” As for the vast southern continent itself, Antarctica was often thought of as a biological desert. Sure, there are lots of penguins. But, scientists long thought that nothing could survive (let alone thrive) in the harsh, frozen, oxygen-poor environment beneath miles of ice. However, there is now vast evidence for diverse communities of microbes beneath the ice sheets, including tiny organisms that could metabolize ancient biomass crushed beneath the ice sheets and expel methane as a potent by-product. In a recent paper published in the journal Nature, a team of scientists from the United Kingdom, the Netherlands, the United States, and Canada tried to calculate the amount of methane that may be trapped beneath the massive ice sheets of Antarctica. Their findings, while speculative, are also sobering: as much as 50% of the West Antarctic ice shelf and 25% of its larger eastern counterpart may contain large basins that could provide the substrates needed to generate significant amounts of methane. Thus, like the Arctic, the Antarctic could harbor large frozen reserves of methane… reserves which would be released into the environment (including into the atmosphere as greenhouse gases) should these ice sheets retreat. Since this is methane, its addition to the atmosphere could exacerbate global warming, accelerating the melting trend which first contributed to its liberation from the ice.
This recent report is speculative in parts. We lack concrete studies of the microbial lifeforms that have made a home in the oxygen-deprived environment beneath the ice sheets. So it is difficult to calculate precisely how much methane could be frozen in Antarctica. Only a thorough, continent-wide survey of life beneath the ice sheets could begin to address this questions definitively. But, as you may have already guessed, that task is no small feat. Still, these findings, even if speculative and preliminary, do raise new concerns about how rapid melting at our poles could contribute to the process of global warming. After all, even though temperatures across the vast polar deserts of East Antarctica show that temperatures there are stable (or cooling), smaller West Antarctica is warming relatively quickly.
- Wadham JL, et al. 2012. “Potential methane reservoirs beneath Antarctica.” Nature. Volume 488: 633-637. [Subscription required, though abstract is available to all.]
- April 23, 2008. “Carbon Dioxide, Methane Rise Sharply in 2007.” National Oceanic and Atmospheric Administration. United States Department of Commerce.
- David Pape and NASA.