Alaska fire in 2007 an ominous sign for climate

ANCHORAGE, Alaska,  (Reuters) – A wildfire that  burned over 400 square miles (1 million sq km) of Alaska tundra  in the scorching summer of 2007 poured as much carbon into the  atmosphere as the entire Arctic normally absorbs each year,  according to a new study in the scientific journal Nature.

The fire, near the Anaktuvuk River of Alaska’s North Slope,  was considered an unprecedented event at the time. It was, by  far, the largest single wildfire on treeless Arctic tundra ever  recorded, and was twice as big as all previously recorded  Alaska tundra fires combined.

It may also be an ominous sign of climate problems in the  future, according to the study and the researchers who  conducted it.

The study, published on Thursday, measured the volume of  carbon emitted by the months-long fire. Although massive, it  covered only a tiny portion of the vast North Slope — at 2.1  million metric tons.

“It was the same order of magnitude as what the Arctic  takes up and stores in plant biomass,” said Syndonia Bret-Harte  of the Institute of Arctic Biology at the University of Alaska,  Fairbanks, one of the study’s authors.

That creates the potential for a “positive feedback” loop  that would reinforce the warming trend in the far north,  according to the study.

Repeated large fires might even cancel out any  carbon-absorption benefits from increased plant growth in the  Arctic made possible by the region’s warming climate, the  researchers said.

Fires on the Arctic tundra are not unusual, but most blazes  are very small and short-lived because of the cool climate and  the dampness of the environment, Bret-Harte said.

The 2007 fire, however, occurred under extreme conditions  — an especially hot, dry year, marked by the smallest Arctic  sea ice cover ever recorded by satellite, plus strong winds.  The lightning-sparked blaze began in July of that year and  smoldered for weeks before it was whipped up by winds in  September, when tundra plants were dried out, she said.