Abstracts
SEARCH Open Science Meeting
October 27, 2003
Seattle, Washington, USA
Atmosphere-Ocean Teleconnections and Alaskan Forest Fires
Paul A. Duffy1, John E. Walsh2, Daniel H. Mann3, Scott Rupp4
1Department of Forest Sciences, University of Alaska, PO Box 757200, Fairbanks, AK, 99775, USA, Phone 907-474-7535, paul.duffy@uaf.edu
2Department of Atmospheric Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA, jwalsh@seas.marine.usf.edu
3Institute of Arctic Biology, University of Alaska, PO Box 757000, Fairbanks, AK, 99775, USA, Phone 907-455-7188, Fax 907-474-7640, dmann@mosquitonet.com
4Department of Forest Science, University of Alaska, PO Box 757200, Fairbanks, AK, 99775, USA, Phone 907-474-7535, Fax 907-474-6184, srupp@lter.uaf.edu
The boreal forest is a huge biome that contains large stores of carbon. Most aspects of ecosystem dynamics in the boreal forest are controlled by wild fires, but the drivers of the fire regime are poorly understood. Some researchers suggest that the fire regime is modulated by the vegetation in the course of decade-scale cycles of secondary succession and at millennial time scales by changes in tree species abundances. Others think that regional climate is the dominant driver of the fire regime. Here we use a multiple linear regression model to quantify relationships between climatic variables and the annual area burned in Alaska over the last fifty years. The seasonality of the circulation-fire linkage is addressed through a systematic evaluation of the East Pacific teleconnection field keyed to an annual fire index. The impacts of ocean-atmosphere interactions are examined through the use of equatorial sea surface temperatures as explanatory variables in the regression model. Six explanatory variables and an interaction term collectively explain over 80% of the variability in the natural logarithm of the number of hectares burned annually in Alaska from A.D. 1952 to 2002. Results reveal that tropical sea surface temperatures and the East Pacific teleconnection (EPT) exert an influence on short-term climate and weather in Alaska. Strong positive phases of the EPT are associated with upper airflow that is more meridional in nature. This meridional flow is conducive to the development of mid-troposphere anomalies that affect short-term weather and fire behavior. Negative phases of the EPT are associated with strengthened westerlies in the eastern North Pacific as a consequence of a more zonal upper airflow. The shift in sign of the teleconnection over a period of several months exerts a significant signal on both temperature and precipitation during the spring and summer in Interior Alaska, while SST anomalies exert an influence on snow pack development through influences on October and November precipitation. These results suggest that climate is an important driver of the fire regime in the boreal forest; however, there is more to fire regime than the number of hectares burned. Lacustrine records of charcoal and observations on the interactions between fuel type and fire behavior all suggest that there are important biological feedbacks involved. We are currently exploring the rich behavior that results when climate drivers are linked to vegetation dynamics in a landscape-scale model of ecosystem dynamics.
Abstract Categories: Changes on Land
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