Climate Change at High Latitude

 
 

Annual Mean Temp. Change (°C)
1965-1995

Although general circulation models (GCMs) predict that over the next 100 years global annual mean temperatures will rise by 1.4-5.8°C, the changes at high latitudes in boreal North America are expected to be much more pronounced (on the order of 10°C). Over the past 30 years the boreal region has already experienced a 1.5-2.0°C warming, and climate models predict that this trend will continue with current rates of fossil fuel consumption, and associated CO2 emissions. The warming and drying already observed in the region most certainly affect ecosystem processes, although the feedback effects of vegetation on climate remain uncertain.

The large reservoir of carbon contained in the cold, saturated and/or frozen soils of the boreal region appears to be increasingly influenced by climatic warming and fire disturbance. Warmer air temperatures deepen the spring thaw, mobilizing a large amount of previously frozen carbon stores. Increased soil temperatures also result from greater fire frequency and severity, producing higher decomposition rates and subsequent release of carbon to the atmosphere.

 

Recent bark beetle infestations, associated with warming (reddish-brown in the photo), have devastated Alaskan forests.

    

The recent warming and drying within boreal regions has produced a steady increase in the frequency and intensity of the boreal fire regime, which not only affects direct emissions and decomposition rates but also produces positive feedbacks that may exacerbate climate changes through modifications of surface albedo (brightness), vegetation composition (via plant succession), and carbon sequestration in forest regrowth. For example, recent bark beetle infestations have killed more than 30 million trees in Alaska since the ealy 1990's. Under normal conditions, bark beetle larvae cannot survive the low wintertime temperatures. However, in the past decade, higher winter minimum temperatures have failed to curtail the flourishing beetle populations, and the subsequent effects of this have been devasting to boreal forests.

Furthermore, in 2004 we witnessed the single largest fire year on record in Alaska, with over 6 million acres burned.  Commenting on this, the Alaska Bureau of Land Management noted, "We have now shattered the record for acres burned in a season by more than a million acres -- 6.3 million acres and climbing (an area the size of Vermont)."  Associated with the record high fires, meteorological stations across the state documented record high temperatures, making 2004 the warmest summer on record. 

The 5-year running mean of temperature at Fairbanks, AK (1910-2002).