A mid-2010 update on Alaska climate change and forest health

Smoke from the Willow Creek Fire has been consistent all summer.

Professor Glenn Juday and student David Spencer will travel the Tanana River to Caribou Crossing and then follow the Kantishna River Aug. 1-5, continuing Juday’s longterm research.

Professor Juday outlines his observations:

Parts of central Alaska, especially the Fairbanks area, received heavy precipitation in a traditional near Fourth of July thunderstorm, on July 5. Some of the deepest accumulations of the largest size hail seen in recent years were part of the storms. Then from July 13 until recently a period of very slightly cooler but cloudy and rainy weather occurred across nearly all of boreal Alaska, which at least nominally ended the 2009-2010 El Nino drought. Total precipitation at most Interior stations is approaching twice normal for July. However, even this break in the weather has not been enough to extinguish the Willow Creek Fire on the Tanana Flats. After all the recent July rain, a line of smoke from smoldering fires around the perimeter is rising, even today. It is difficult not to imagine that long-term stored carbon is being mobilized. The cumulative drying that was necessary to set up this situation was historic, and public interest is so high that an information station has been placed on the George Parks monument (see photo below).



Early August appears to be favorable for a warming trend, setting the stage for a re-activated late fire season. Already the 2010 season has reached 1 million acres burned.

The persisting aspen leaf miner outbreak (pictured above), and possibly the acute heat and drying of summer 2009 are now beginning to clearly take a toll on aspen trees, as can be seen almost everywhere in low-elevation central Alaska. In the first few years of outbreak, aspen leaf miner was a nuisance, then a factor in reducing growth. But after nearly a decade of heavy feeding by leaf miners, tree death on a large scale has begun for the first time to my knowledge and others I have spoken to.

My research (soon to be submitted) shows that spruce budworm outbreaks require a critical heat sum (818F growing degree days or 454C) to be accumulated on or before July 7 at Fairbanks. In 2010, the critical heat sum was accumulated in Fairbanks on July 6. Since the local budworm population was low, it appears that 2010 is a buildup year, and that a warm August 2010 would now favor a 2011 outbreak, unless further population buildup is required to recover from the 2008/2009 budworm low. But that might only delay the outbreak to 2012.

Barrow had a brief cooler than normal period of temperatures (after near-record positive anomalies for most of a year) due to late persisting pack ice to the east in the Beaufort Sea. In late July the ice had largely dissipated, and strong positive temperature anomalies resumed. Monthly precipitation at Barrow during the past year frequently has been twice the normal (extremely low) amount, as could be expected with less ice covering the ocean to the north.

Alaska birch are showing signs of birch leaf scorch, a form of acute drought stress injury. Symptoms normally appear the year after the severe heat and drought, because of the lag effect of root dieback. July 2009 was the fourth warmest month in the entire 105-year Fairbanks record, and leaf scorch is right on schedule by appearing in summer 2010. During our trip to the Rosa Keystone Dunes Research Natural Area in the Tanana Valley State Forest, Quartz Lake, and Bonanza Creek Long-Term Ecological Research my technician, students, and I have seen leaf scorch, trees with very low leaf mass and yellow leaves in early summer, birch top dieback, and now tree death. The 2009 severe stress was the second in a decade (previous in 2004/2005), and the trees are near lethal limits of climate change.

Very severe damage from Willow leaf blotch miner has spread in 2010 across most of the Tanana Valley, as we had anticipated after 2009 observations of the Yukon Flats.