Shrinking ponds signal warmer, dryer 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.

Source: University of Alaska Fairbanks

Related stories:

Alaska glacier speed-up tied to internal plumbing issues
A University of Colorado at Boulder study indicates meltwater periodically overwhelms the interior drainpipes of Alaska's Kennicott Glacier and causes it to lurch forward, similar to processes that may help explain the acceleration of glaciers observed recently on the Greenland ice sheet that are contributing to global sea rise.
Nutrient pollution drives frog deformities by ramping up infections
High levels of nutrients used in farming and ranching activities fuel parasite infections that have caused highly publicized frog deformities in ponds and lakes across North America, according to a new study led by the University of Colorado at Boulder.
Mathematics of Ice to Aid Global Warming Forecasts
University of Utah mathematicians have arrived at a new understanding of how salt-saturated ocean water flows through sea ice - a discovery that promises to improve forecasts of how global warming will affect polar icepacks.
Arctic Lakes Are Disappearing
Global warming appears to be causing lakes to drain and disappear in Arctic regions, a UCLA-headed team of researchers report in the latest issue of Science.
If the pattern persists, it may imperil migratory birds and wreak further havoc on the region's weather, warns Laurence Smith, the article's lead author and an associate professor of geography at UCLA.
Researchers Isolate Microorganisms That Convert Hydrocarbons to Natural Gas
(PhysOrg.com) -- When a group of University of Oklahoma researchers began studying the environmental fate of spilt petroleum, a problem that has plagued the energy industry for decades, they did not expect to eventually isolate a community of microorganisms capable of converting hydrocarbons into natural gas.
Pacific shellfish ready to invade Atlantic
As the Arctic Ocean warms this century, shellfish, snails and other animals from the Pacific Ocean will resume an invasion of the northern Atlantic that was interrupted by cooling conditions three million years ago, predict Geerat Vermeij, professor of geology at the University of California, Davis, and Peter Roopnarine at the California Academy of Sciences.
Research team draws 150-meter ice core from McCall Glacier
A 150-meter ice core pulled from the McCall Glacier in the Arctic National Wildlife Refuge this summer may offer researchers their first quantitative look at up to two centuries of climate change in the region.
Freshwater runoff from the Greenland Ice Sheet will more than double by the end of the century
The Greenland Ice Sheet is melting faster than previously calculated according to a recently released scientific paper by University of Alaska Fairbanks researcher Sebastian H. Mernild.

News discussion:

Space & Earth science news