EGS Seminar – Tuesday 20th November 2012

Tuesday 20th November, Room E419, 4th floor, John Dalton East Building, from 1.00-2.00pm.



Toasting Plants: How Extreme Winter Warming Events May Reverse the Greening Of the Arctic
Gareth Phoenix, University of Sheffield


The Arctic is experiencing greatest warming in winter and a greater frequency of extreme climatic events, yet the impacts of winter climatic change and extreme events have been little studied. Of considerable concern are extreme winter warming events, during which temperatures increase rapidly causing snow-melt at landscape scales and subsequently exposing ecosystems to unseasonably warm temperatures. Following warming, ambient cold winter temperatures can return rapidly, exposing vegetation and soils to extreme cold due to the absence of the insulating snow layer. Here I’ll report on consistent findings from both a field simulation study and a natural event that show major damage to plant communities occurring at landscape scales resulting from extreme winter warming events. In summary, single week-long winter warming events (both simulated and naturally occurring) resulted in up to 20 times more shoot death in plants and reduced productivity and carbon sequestration. Using satellite date, the extent of damage from a natural event indicated a 26% reduction in NDVI (a proxy for leaf area) over an area of 1424 km2.

With increasing winter temperatures predicted along with a greater frequency of extreme climatic events, these findings suggest major consequences for the productivity and diversity of Arctic ecosystems. Critically, the damage from these winter events is opposite to the shrub expansion and greening of parts of the arctic currently attributed to summer warming. Given that the arctic is warming more in winter than summer, these impacts place a significant challenge in predicting the future of arctic vegetation in a warmer world.