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Alaska Warmer Dryer

Page history last edited by PBworks 13 years, 11 months ago

Institute of Arctic Biology University of Alaska - Fairbanks


12 October 2006


Shrinking ponds signal warmer, dryer Alaska



12 October 2007


FAIRBANKS, Alaska -- A first-of-its kind analysis of fifty years of

remotely sensed imagery from the 1950s to 2002 shows a dramatic

reduction in the size and number of more than 10,000 ponds in Alaska.

The analysis, by University of Alaska Fairbanks scientists and

published this week in the Journal of Geophysical Research, indicates

that these landscape-level changes in arctic ponds are associated

with recent climate warming in Alaska and may have profound effects

on climate and wildlife.


Over the past 50 years, Alaska has experienced a warming climate with

longer growing seasons, increased permafrost thawing, an increase in

water loss due to evaporation from open water and transpiration from

vegetation, and yet no substantial change in precipitation.


The shrinking of these closed-basin ponds may be indicative of

widespread lowering of the water table throughout low-lying

landscapes in Interior Alaska, write the authors. A lowered water

table negatively affects the ability of wetlands to regulate climate

because it enhances the release of carbon dioxide by exposing soil

carbon to aerobic decomposition.


"Alaska is important in terms of waterfowl production and if you have

a lowering of the water table that could have a potentially huge

impact on waterfowl production," said Dave Verbyla, co-author and

professor in the School of Natural Resources and Agricultural

Sciences at UAF.


"This is an issue relevant to flyway management in terms of all the

waterfowl that might use the Yukon Flats National Wildlife Refuge and

overwinter elsewhere, and this is something that goes beyond the

refuges in Alaska," said A. David McGuire, co-author and professor of

ecology at the Institute of Arctic Biology at UAF.


National Wildlife Refuges cover more than 77 million acres in Alaska

and make up 81% of the national refuge system. These refuges provide

breeding habitat for millions of waterfowl and shorebirds that

overwinter in more southerly regions of North America.


"No one has done a state water-body inventory of this magnitude,"

said Brian Riordan, lead author and data manager for the Bonanza

Creek Long-Term Ecological Research program at UAF. "It will allow

land managers to stop speculating about possible water body loss and

begin to address the implications of this loss."


Using black and white aerial photographs from the 1950s, color

infrared aerial photographs from 1978-1982, and digital images from

the Landsat satellite from 1999-2002, Riordan outlined each pond by

hand. "With automated classification your accuracy goes down,"

Riordan said. Cloud shadows can look like water and Alaska rarely

experiences a cloudless day, said Verbyla.


The most difficult part of the four-year project, said Riordan, was

"having the patience to circle 10,000 ponds for each time period."


The main study area was the subarctic boreal region of Interior

Alaska, which spans more than 5 million square kilometers bounded on

the north by the Brooks Range and on the south by the Alaska Range.

To contrast the semi-arid, subarctic sites of discontinuous

permafrost in Interior Alaska, the authors also selected a study area

in the Arctic Coastal Plain where the temperatures are much colder,

the growing season much shorter, and the permafrost is continuous,

and a more maritime site south of the Alaska Range.


All ponds in the study regions in subarctic Alaska showed a reduction

in area of between 4 and 31 percent, with most of the change

occurring since the 1970s. The ponds in the Arctic Coastal Plain

showed negligible change.




This project was funded through support from the National Aeronautics

and Space Administration Land Cover/Land Use Change Program and the

National Science Foundation and United States Department of

Agriculture jointly sponsored Bonanza Creek LTER program.




Brian Riordan, data manager Bonanza Creek Long-Term Ecological

Research program, University of Alaska Fairbanks, 907.474.6364,



David Verbyla, professor, School of Natural Resources and

Agricultural Science, University of Alaska Fairbanks, 907-474-5553,



A. David McGuire, professor of landscape ecology, Institute of Arctic

Biology, assistant leader, Alaska Cooperative Fish and Wildlife

Research Unit, University of Alaska Fairbanks, 907-474-6242,



Marie Gilbert, public information officer, Institute of Arctic

Biology, University of Alaska Fairbanks, www.iab.uaf.edu,

907.474.7412, marie.gilbert@uaf.edu


Notes for Journalists:


Journalists (only) may obtain a PDF of this paper upon request to

Harvey Leifert, +1-202-777-7507, hleifert@agu.org. Include your name,

name of publication, phone, and email address. The paper and this

press release are not under embargo.




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