The Cold Carbon Checkbook
Enraptured by the Interior's so-far balmy winter, my mind lately has turned to the subject of global warming. It took only a little research to establish that even experts on the subject will do no more than speculate if global warming caused the unusual weather patterns of the winter of 1993-94, with record-breaking snow and cold in the eastern half of the United States and temperate conditions in our corner of the far north. Climate (which, metaphorically speaking, is to weather as a career is to a job) is a wonderfully complex subject, and even the experts still know too little about the earth---and for that matter, the sun---to be sure.
But I did find out that some people think they now understand one aspect of the far north's role in the global warming game. It involves the Arctic output of one of the greenhouse gases contributing to the warming, and it comes down to balancing the carbon budget.
Consider: some things, such as animals, internal combustion engines, and volcanoes, contribute carbon (chiefly in the form of carbon dioxide) to the atmosphere. In technical terms, they are considered sources in the global carbon budget. In effect, they're making deposits into the atmosphere's carbon account. Other things, such as the oceans and green plants, take up carbon; they are the sinks, making withdrawals from the atmospheric account's balance. Lately we've been hearing a great deal about the importance of the tropical rain forest as a carbon sink; it's hard to recognize the unromantic "sink" under the passionate green terms used to describe the role of those gigantic rain-forest trees in cleansing the atmosphere, but a sink they are.
Knowing that wood is mostly carbon, one can easily see the great forest storing tons of the stuff. A big Sitka spruce or Siamese teak has transformed a lot of carbon dioxide into a very tall, visible tree. But many of the biosphere's carbon-storing structures aren't as immediately visible as terrestrial plants. Coral reefs, for example, have tucked away prodigious amounts of carbon (as calcium carbonate) unseen under the warm and shallow seas. And in cold northern climes, the soil has locked up great quantities of carbon. The annual buildup of plant litter, dead but not decomposing fully because of the arctic cold, has produced one of the great carbon reservoirs of the earth. The Arctic has been the site of a slow and steady withdrawal from the atmospheric carbon account ever since the last ice age ended. Until recently, it was thought this process would continue into the future.
One study indicating that the tundra is no longer a sure-fire carbon sink has been taking place over the last few years on Alaska's North Slope. Working out of the University of Alaska Fairbanks' Toolik Lake facility, a team of researchers from California and Oregon have been measuring and analyzing the gases given off and taken up by tundra ecosystems. Their results have been remarkably consistent: every summer, everywhere they measured, the tundra ecosystems have been giving off more carbon dioxide than they've been taking up. The total amounts vary according to location, but the researchers are confident of their estimates of output, which range from near 50 to over 280 grams of carbon a year from every square meter of tundra. That may not sound like much, but given the number of square meters in the Arctic, it adds up to some pretty significant carbon additions to the atmosphere.
The researchers think that the change has come about because the Arctic is already warmer and drier than it has been. They suspect the crucial element propelling the change is not the additional warmth itself, but the lower water table and better soil drainage and aeration. That means better conditions for decomposition, and more decomposition releases more carbon dioxide, which may mean still more global warming.
