September 25, 2005

Early snowmelts heating Alaska Arctic-study

By Yereth Rosen

ANCHORAGE, Alaska (Reuters) - Spring snowmelt in Alaska's
Arctic is occurring progressively earlier, accelerating the
region's climate change and helping produce its warmest summers
in at least 400 years, according to a new study.

The earlier snowmelt, itself a product of a warming
climate, is one of the "positive feedback" factors that
accelerates warming in the far north, said Terry Chapin, a
professor of ecology at the University of Alaska Fairbanks'
Institute of Arctic Biology and the study's lead author.

"Each of these changes seems to trigger other changes that
mean more changes will occur," Chapin said.

The National Science Foundation-funded study published this
week in the online journal Science Express found spring
snowmelt had been occurring about 2.5 days earlier per decade,
exposing dark ground to solar heat earlier in the season.

Heat absorbed by the ground releases energy into the local
atmosphere, about three watts per cubic meter each decade, a
change that is heating the local atmosphere and even adding
incrementally to global warming, Chapin said.

"This heat is added to the atmosphere, so the atmosphere in
the north becomes warmer and is mixed with the global
atmosphere," Chapin said.

Summer warming will be amplified by two to seven times if
trees and bushes continue their northern migration into
Alaska's Arctic, the study also said.

For now, the tundra is still relatively free of large
vegetation, although such plants are starting to colonize more
northern areas, said Matthew Sturm of the U.S. Army's Cold
Regions Research and Engineering Laboratory in Fairbanks,
Alaska, one of the study's co-authors.

"When we look hard, we find that most of the warming that's
already taken place can be explained by the reduction in
winters," Sturm said. "But we know that the change in
vegetation is already underway. That has the potential to
become even more of a feedback."

Chapin said the earlier snowmelts could have profound
impacts in the Arctic. "Any kind of ecological or human
activity that requires snow or snow-free conditions are bound
to be affected by that," he said.

Caribou time their spring migrations so they can arrive at
the Arctic coast just as the snow is disappearing and the most
tender plants are emerging from the tundra, he said.

If the snow melts too early, the plants could be mature and
tough, and snow and ice bridges used to cross rivers could be
gone when caribou arrive at their coastal calving grounds, he