Ecosystem Studies & Management
Climate Change at High Latitude
Although general circulation models (GCMs) predict that global annual mean temperatures will rise by 1.4-5.8°C over the next 100 years, the changes at high latitudes in are expected to be much more pronounced (on the order of 10°C). Similarly, the warming observed at high latitudes in the last 50 years exceeds the global average by as much as a factor 5, that is, 2-3 °C in Alaska and Siberia versus 0.53 °C global mean (from 2001-2005 relative to 1951-1980 baseline). 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.
Annual Mean Temp. Change (°C) 1965-2009
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 early 1990s. 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, the single largest fire year on record in Alaska occurred, 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 warmest July in recorded history occurred in 2009, and 2005 was 2nd largest fire year (2009 was in the top-10). The fires of 2004 and 2005 together burned more than 4 million hectares (~10 million acres).
The 5-year running mean of temperature at Fairbanks, AK.
