The 2013 Alaska wildland fire season could best be summed up as "it could have been worse". Alot worse. 528,000 hectares burned (1.32 million acres), which is significantly above the mean value (since 1955) of 364,000 (910,000 acres). As you can see from our graph of Alaska wildfire acreages plotted along with May-Aug Fairbanks average temps., summer-time temperatures were also significantly above-average, and many high temperature records were broken, especially in June and July.
In fact, the situation was looking quite dire by mid-June, when an anomalously strong and warm high pressure ridge built in over the mainland of Alaska. High temperatures of 30-36C (86-96F) occurred on several days in many locations across the Interior and South-Central Alaska.
This led to something your lead editor had never seen before in my time in Alaska since 1998, this.
The majority of the state under Red Flag Warnings or Watches, including Anchorage and Fairbanks. Red Flag Warnings are issued by the National Weather Service to the land management agencies, Bureau of Land Management (BLM), US Forest Service, etc.., whenever pre-defined weather criteria combined with dry forest fuels, are met or exceeded. Which would lead to extreme fire behaviour in new or existing fires. Usually, just parts of the Interior, or South-Central Alaska will see these conditions at any given time during the summer.
Fortunately for residents of the Alaska Interior, where most of the fires occurred, two well-timed rainfall events during the second week of July, helped temporarily slow things down, before warmer/drier weather returned the following week. Significant rains and below-average temperatures brought an end to the season after 8/15, which is the case in most years. July and August are usually the wettest months in Interior Alaska, and when this pattern is disrupted by long dry spells of three weeks or more, large fire outbreaks occur and continue through the summer. Three good examples of this just in the past decade were in 2004 (the largest in AK recorded history), 2005, and 2009.
The fires of 2013 were also fairly evenly spatially distributed across the Interior, widespread lightning events fueled by westward-moving "easterly waves", which are remains of old frontal systems from the Gulf of Alaska, circulating around an upper-level low in the Gulf. These tend to occur several times each summer, and produce the most widespread thunderstorms, on some occasions, 10-13 thousand lightning strikes can occur with these, igniting numerous wildfires if the boreal forest is dry enough.
In the eastern Interior, east of Fairbanks, to the Canadian border, conditions in July and August were drier, so dry in fact that extreme fire behaviour occurred on many occasions. Take a look at the Alaska "Fire Tornado" that occurred near Tetlin Junction, not far from the Canadian Border, on 17 August.
This is what happens when summertime temperatures and precipitation in the Alaska Boreal Forest reflect conditions that usually occur much further south, say in southern British Columbia, or northwest Montana. Conditions the Alaska Interior will be seeing much more of in the years ahead, as global warming continues apace.
This fire, to the right, called the Mississippi Fire, burned nearly 28,000 hectares (70,000 acres), mainly from 8/06 to 8/18, when strong southerly chinook winds pushed it to life, and nearly to the Tanana River, and approaching the town of Delta Junction. Active suppression efforts on its north end though, helped ensure that it would be unable to threaten Delta again, often by "burning out" areas behind the fireline, as shown here. Nevertheless, the boreal forest tree deciduous species in this area of the interior in the first few weeks of August, such paper birch, aspen, and balsam poplar were showing significant drought stress. With brown, withered leaves, and/or early fall colour.
Conditions in Canada were much worse overall, for the country as a whole, 3.8 million hectares burned in 2013 (9.5 million acres), more than twice the 25-year average there of 1.5 million hectares.
This is all in line with the fact that the Earth is responding to global warming, albeit slowly. Because the oceans are absorbing a good percentage of the increasing heat from our escalating levels of CO2 and methane (CH4) from fossil fuel extraction and combustion.
As we have mentioned before, latest research is now showing that the last time atmospheric CO2 levels were at the current level of 400 ppm (2.2 - 3.6 million years ago), global sea levels were 20m (66ft) higher. And the climates of Siberia and Alaska were similar to that which were found in the Northwestern US and southern BC Canada, until relatively recently. Given that it is quite likely atmospheric CO2 levels will reach at least 550-600 ppm by 2060, until either nature, or humanity is able to stop this, we have to therefore expect that the Arctic climates will continue warming to levels even warmer than they were 2.2-3.6 million years ago. Interior Alaska's climate would likely then become similar to, or even warmer than that found in the interior of the Northwestern lower 48 states. Places such as Missoula, MT, Spokane, WA, or even The Dalles, OR. The main uncertainty now is how long this will take. Will it be 50 years, 100, 200 or more, before the climate system "catches up" with the increased CO2 levels?
The boreal forest ecosystems will not be able to tolerate the warmer/drier summers, leading to massive die-offs, especially at the lower elevations of the Interior, and on drier, southeast-west facing slopes. With the warmer and drier weather, and vast swaths of the Interior having dead/dying boreal forest stands, we think it's safe to say our increasing wildfire acreage trends will continue, and amplify. And the fire behaviour seen will become increasingly extreme, as we saw this summer on the Tetlin Junction fire.
As well, the increasing wildfire acreages across the boreal forest systems throughout the Arctic are also "positive feedback" mechanisms, releasing even more CO2 and CH4 from combustion and permafrost melting, leading to even more greenhouse warming.
Cheers.
