One effect studied intensively at the UAF Institute of Arctic Biology Toolik Field Station on Alaska's North Slope is shrub expansion on the tundra.
"Shrubs are increasing on the tundra as the climate warms and more shrubs will lead to more warming in the spring," said Bret-Harte. Snow reflects most incoming radiation, which is simply light that can transfer heat. Shrubs that stick out of the snow in spring absorb radiation and give off heat. In this positive feedback cycle, the heating of the air immediately above the snow warms the snow, causing it to melt sooner. Warmer soils lead to increased nutrient availability, which contributes to greater shrub growth, which then contributes to still more warming.
Another effect studied intensively in Alaska occurs under the snow.
"We need to better understand how winter comes and goes and how that drives shifts in plant-animal interactions," said Jeff Welker, professor of biology at the University of Alaska Anchorage. When it didn't snow at Toolik Field Station until Thanksgiving a few years ago the soil got cold and stayed cold. So cold that microbes in the soil were barely active. The spring green-up was slow in coming and likely affected caribou forage, says Welker.
In 2008, the snow started falling in September and never quit. The warmer winter soils with their active microbes were insulated from the cold and were able to provide nutrients to plants that stimulated growth.
The authors call for immediate attention to the conservation of Arctic ecosystems; understanding the ecology of Arctic winters; understanding extreme events such as wildfires and extended droughts; and the need for more baseline studies to improve predictions.
"This paper identifies gaps in our knowledge, what we need to be doing and where the public needs to spend its money," said Welker.
|Contact: Marie Gilbert|
University of Alaska Fairbanks