A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Space Science » Science
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

Early Arctic Thaw Could Have Chilling Effect



 
 
Thread Tools Display Modes
  #1  
Old September 30th 03, 01:23 AM
Ron Baalke
external usenet poster
 
Posts: n/a
Default Early Arctic Thaw Could Have Chilling Effect

http://www.jpl.nasa.gov/news/features/thaw-092903.cfm

Spotlight Feature

Early Arctic Thaw Could Have Chilling Effect
Written by Rosemary Sullivant
Media Contact: Alan Buis (818) 354-0474
Jet Propulsion Laboratory
September 29, 2003

Spring will be coming early next year to the great forests and tundra
of the Arctic. Good for the vegetation, but perhaps not so good for
the atmosphere.Spring in the high latitudes has been coming earlier in
the past few decades. The early thaw means a longer growing season for
the Arctic and the boreal forest, the ring of mostly evergreen trees
that stretches across the northern reaches of North America and
Eurasia. It also means that more carbon, now stored in the region's
usually frozen soils, may be released into the air.

"The spring thaw date in boreal North America has been advancing
almost one day a year since 1988," says JPL research scientist Dr.
Kyle McDonald. He and his colleagues are using data from NASA's
Quikscat and Japan's Midori 2 satellites to determine exactly when and
where the thaw occurs. The satellites' radar instrument, the Seawinds
scatterometer, can detect changes in water across the landscape from
its frozen to liquid state. They used data from previous microwave
missions to piece together a historical record of the spring thaw in
this large, remote area where few ground measurements exist.

The boreal forest, called the taiga in Russian, is the second largest
forest ecosystem on Earth, second only to the tropical rain forest in
size. In North America it covers almost 28 percent of the land north
of Mexico, covering much of northern Canada and reaching into Alaska.

Scientists are interested in monitoring thaw events in the Arctic and
the boreal forest for several reasons. The region is extremely
sensitive to change in temperature. "If global climate change is
happening, here's where you would expect to see it," McDonald says.
The region also plays a major role in Earth's carbon cycle.

For most of the year, the temperature of the ground in the Arctic
tundra and boreal forest is below 0 degrees Centigrade (32 degrees
Fahrenheit) and the vegetation is dormant. But a little bit of warming
has a big effect. Once surface soil temperatures edge over freezing,
plants rapidly spring into action. "There's a very abrupt change from
dormant to productive associated with the spring thaw," says Dr. John
Kimball, a research assistant professor at the University of Montana's
Flathead Lake Biological Station. "It is like a natural on and off
switch."

Over the centuries, this huge area of tundra and forest has taken
great quantities of the greenhouse gas carbon dioxide out of the air,
released oxygen back into the atmosphere and stored the remaining
carbon in vegetation. Eventually plants decompose and the carbon ends
up in the soil. "The high latitudes hold roughly 40 percent of the
world's soil carbon," says Kimball.

Earlier springs in the boreal forest and Arctic tundra mean a longer
growing season with more vegetation taking more carbon out of the
atmosphere for longer periods. However, the same warming that releases
water and nitrogen in the soil enabling plants to grow is also good
for microbes that unleash the carbon stored in the soil back into the
atmosphere.

"Frozen soil can store carbon dioxide for thousands of years," says
Kimball. "Trees and other vegetation can only store it for up to a few
hundred years or less. The residence time is much shorter and more
unstable." He also points out that since the 1960s the number of
forest fires in the region has increased dramatically, decreasing the
length of time that trees and other plants hang on to their stored
carbon before releasing it back into the atmosphere.

Could the boreal forest and Arctic tundra change from being a carbon
sink, a place where carbon is stored, to a carbon source? That's the
big, yet unanswered, question.

In the '50s horror movie "The Thing," warming up a frozen creature
discovered in the Arctic brought a monster to life. It may turn out
that some other things are better kept frozen.


 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT +1. The time now is 03:59 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.