Journal Article Tundra burning in 2007 – Did sea ice retreat matter?

Vladimir A. Alexeev  ,  Eugénie S. Euskirchen  ,  Jessica E. Cherry  ,  Robert C. Busey

9 ( 1 )  , pp.185 - 195 , 2015-06
The goal of this study was to assess the importance of the 2007 sea ice retreat for hydrologic conditions on the Alaskan North Slope, and how this may have influenced the outbreak of tundra fires in this region. This study concentrates on two years, 2007 and 1996, with different arctic sea ice conditions and tundra fire activity. The year of 2007 is characterized by a low summer sea ice extent (second lowest) and high tundra fire activity, while 1996 had high sea ice extent, and few tundra fires. Atmospheric lateral boundary forcing from the NCEP/NCAR Reanalysis drove the Weather Research and Forecast (WRF) model, along with varying sea ice surface forcing designed to delineate the role of sea ice. WRF runs successfully reproduced the differences between 1996 and 2007. Surprisingly, replacing sea ice conditions in 1996 run by those from 2007 and vice versa (2007 run with 1996 sea ice) did not change the overall picture. The atmospheric circulation in August of 1996 included a significant low-pressure system over the Beaufort and Chukchi Seas. However, in 2007, a high-pressure system dominated the circulation over the Beaufort Sea. It is argued that this difference in large-scale patterns, rather than retreat of sea ice, was responsible for anomalously dry and warm atmospheric conditions over the North Slope in summer and autumn 2007, suitable for high tundra fire activity. Circulation in 2012 is contrasted with that in 2007 to further stress its importance for local weather on the North Slope.
2007年の北極海氷域後退がアラスカ北部斜面域のツンドラ火災を誘発したかを、1996年の海氷条件と比較することで明らかにした。現象としては2007年夏の海氷域広がりは観測史上2番目の小ささでツンドラ火災が多発したが、1996年は広がりが大きくツンドラ火災は少なかった。NCEP/NCAR再解析データを用いて、海氷表面に与える力の条件をいろいろ変えて、Weather Research Forecast(WRF)モデルを駆動した。WRFモデルは1996年と2007年の海氷広がりを再現できたが、1996年と2007年の海氷条件をそっくり入れ替えても海氷広がりの全体像に変化はなかった。一方、1996年8月はBeaufort及びChukchi海の低気圧が顕著であったが、2007年ではBeaufort海で高気圧が卓越していた。海氷域の後退よりはむしろ、大きなスケールでの大気循環パターンの相違が2007年夏から秋のアラスカ北方斜面域での異常乾燥と温暖を用意し、ツンドラ火災が多発したと考えられる。

Number of accesses :  

Other information