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Frontiers
Study Pulls the Plug on Arctic's Carbon Sink
March/April 1998
The arctic tundra seemed to be a straightforward
example of a carbon sink: The vast, treeless, permafrosted plain took
in more carbon through photosynthesis than it released through decay and
respiration.
But members of the Gas Flux Study, part of NSF's Arctic System Science
Program, have pulled the plug on the "carbon sink" image. In a three-year
study in Alaska's Kuparuk River Basin, the team found that some years
the tundra adds more carbon than it removes, although the total amount
released is still quite small.
The team also discovered a measurement problem. "Five or six years ago,
all of the estimates were made only on the terrestrial side," says biologist
George Kling of the University of Michigan. The estimates ignored the
tundra's streams and lakes and therefore underestimated the amount of
carbon released.
The team uses computer models to quantify the amount of carbon flux from
the arctic tundra into the global ecosystem. The estimates are only for
the current climate; if the arctic gets warmer, as predicted, all bets
are off. A warmer arctic may mean more carbon and more methane, or just
more carbon. It might also mean more nitrogen, because plants will decay
faster. Since most of the tundra plants are limited by the amount of nitrogen
in the soil, more nitrogen would mean more plant growth.
[July/August
1997]
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