By Christopher Neill
Principal Investigator, MBL Science Journalism Polar Program
The tomato plants I saw in Fairbanks Alaska this week were taller than the ones in my front yard in Falmouth. A clear reminder that the centers of large land masses—and Alaska qualifies as a truly large land mass—produce continental climates that often go to extremes.
Fairbanks’ weather proves the rule. The historic high is 96 degrees. The historic low is 62 below.
Climate models predict interior Alaska will get warmer and wetter later in this century. To an outsider that might sound like relief from bone-breaking winter cold.
But the reality is a bit more complicated—and not necessarily rosy.
The drive north from Fairbanks traverses one of the most spectacular and wildest landscapes on earth. It passes hills and mountains, stacked behind more hills and more mountains.
But this drive also reveals the new face of interior Alaska. And that face is driven by fire.
The Dalton Highway of 2008 was not the Dalton Highway of 1998 that I remembered. It now passes thousands and thousands of acres—literally hours of driving time—through burned black spruce forest.
This is because the summer of 2004 was the worst fire year in Alaskan recorded history. Forest the size of the state of Vermont—more than 6.7 million acres—burned. That was followed by the summer of 2005, which was the third-worst fire year in history. That burned 4.5 million acres, or merely the area of Rhode Island and Connecticut.
May 2005 was the warmest May in Alaska history. August of 2004 was the driest on record—until that was broken by even drier conditions in 2005.
In all, ten percent of interior Alaska burned in two “100-year” fire years back to back.
Unlike fires in the western US, Alaskan wildfires are all natural. The record Alaska fire years were not caused by suppressing fires for many decades. Alaskans practice wildfire control only in very limited zones around urban areas. These effects are likely to be driven entirely by climate.
The increased temperatures caused by general climate warming bring with them more energy in the form of the thunderstorms that ignite wildfires. On June 15, 2005, the Alaska lightning detection system recorded 11,163 strikes. This shattered the previous record of 9,022 set only on July 15, 2004.
As higher concentrations of carbon dioxide drive global temperatures upward, climates become more variable, and more often extreme. So phenomena that were once rare become more common.
Two dramatic fires years in a row in Alaska, or two 500-year floods on the Mississippi in 15 years.
These unusual and episodic events are by their nature unpredictable. But take them in the following context of high-latitude changes. Arctic temperature is rising, permafrost is melting, northern coasts are eroding and the discharge of northern rivers is increasing. Lakes lose ice earlier and are warmer during the summer. Glaciers are receding, the tundra is becoming shrubbier, and birds are extending their ranges north. The Arctic Ocean ice cap is reaching historic minimums.
All of these trends are consistent with scientific predictions of global change. Many of these changes, like the loss of polar sea ice, have happened even faster than models predicted. Skeptics of global change argue that outputs from models have uncertainties. True indeed. But those uncertainties can cut both ways. It looks like some predictions of arctic change have been too conservative.
When fires burn they consume wood, leaves and soil organic matter. This reduces fuel for future fires and acts as a brake—or negative feedback—on future fires.
Finding if and how these natural brakes operate is now one of the great challenges of ecological research at high latitudes. So scientists sit at chalkboards and draw arrows connecting higher temperatures to shrubbiness to greater absorption of light to yet warmer temperatures. And they design experiments to test whether the spinning of these proposed connections will make arctic ecosystems change even faster in the future.
I am sitting in bright sunlight looking south to the Brooks Range across one of the greatest natural landscapes on earth. Today’s high was more than 80 degrees. It’s 9:30 pm and puffy cumulus clouds are building. The kind that cause lightning.
A helicopter has just quit ferrying researchers 23 miles to the west and north of me to Alaska’s largest fire of 2007. It started July 16 and burned a one-quarter million acres of treeless tundra. It was the largest tundra fire anywhere on earth, ever. It went out only when buried by snow.
Extremes, it appears, are moving north. An indication, very likely, of things to come.
