Extreme melt season leads to ecosystem changes in Antarctic polar desert

a color photo of the the McMurdo Sound

Mazes of blue and white ice in the McMurdo Sound. Photo: Walter Andriuzzi/CSU

An abnormal season of intense glacial melt in 2002 triggered multiple distinct changes in the physical and biological characteristics of Antarctica’s McMurdo Dry Valleys over the ensuing decade, according to new research led by the University of Colorado Boulder.

Colorado State University’s Diana Wall, director of the School of Global Environmental Sustainability, is a co-author on the new study.

The findings, published August 7 in Nature Ecology and Evolution, suggest that short-lived glacial melts can cause long-term alterations in polar regions. This type of climate-related change unfolds over the span of several years and, subsequently, alters the overall trajectory of an ecosystem. There are few long-term records apart from this study documenting these changes.

Garwood Valley Antarctica Jan 2017
Diana Wall has traveled with a team of researchers to the McMurdo Dry Valleys for the past 27 years. Photo: Walter Andriuzzi/CSU

“This is not just about Antarctica — all earth-bound ecosystems are experiencing climate change and respond in different ways,” said Wall, also a professor in CSU’s Department of Biology and a senior research scientist at the Natural Resource Ecology Laboratory. “This study exposes how an ice-free polar ecosystem is changing and the finding is that it is not a directional or smooth response.”

Wall, a University Distinguished Professor, has traveled with a team of researchers to the McMurdo Dry Valleys for the past 27 years. The valleys are the largest ice-free region of Antarctica and are considered a polar desert environment due to the low humidity and scarce precipitation. Wall’s primary research interests lie in studying nematodes, roundworms that live in the soil.

A look back at climate events in Antarctica

The research team analyzed data and samples from the McMurdo Dry Valleys Long-Term Ecological Research project, which has been supported by the National Science Foundation over the past 25 years. CU Boulder’s Michael Gooseff, as associate professor, is currently the lead investigator of this project.

Between 1987 and 2000, scientists found the McMurdo Dry Valleys region experienced a period of cooling, and summer temperatures steadily declined while solar radiation gradually increased. The trend resulted in expected changes to most biological variables, including decreased streamflow and increased thickness of permanent ice covers on lakes.

In 2002, however, the valleys experienced an abnormally warm and sunny summer season, triggering the greatest amount of glacial meltwater since 1969. The abrupt event prompted numerous changes in the lakes, streams and soils of the McMurdo Dry Valleys over the following decade.

“This flood year was the pivot point,” said Gooseff, a fellow in CU Boulder’s Institute of Arctic and Alpine Research. “Prior to that, all physical and biological indicators had been moving in the same direction.”

The research team found that biological responses to the 2002 season varied and, in some cases, lagged behind by years. Scientists discovered that one dominant soil species that was previously declining increased slowly following the flood year, while a rarer species responded more positively to the moisture and saw population increases carry over into subsequent summers.

Ecosystem ‘out of whack’

CSU’s Wall said researchers will continue to examine whether the ecosystem is truly “out of whack,” as the team found, whether it returns to a more normal state or takes off on a new trajectory. That means we could even see a “greening” of Antarctica.

Diana Wall Miers Antarctica
CSU’s Wall said researchers will continue to examine whether the ecosystem is truly “out of whack” in Antarctica. Photo: Martijn Vandegehuchte

Wall and a team of researchers will travel later in 2017 to the Shackleton Glacier — located on the eastern part of the continent — to provide a contrast to the Long-Term Ecological Research. The latter research project looks at changes over tens to hundreds of years, whereas Wall will be analyzing changes that have happened over thousands of years the Shackleton Glacier area.

Trent Knoss, University of Colorado Boulder, contributed content for this story.

Co-authors of the new research include Diane McKnight and Eric Sokol of CU Boulder and INSTAAR, John Barrett of Virginia Tech University, Byron Adams of Brigham Young University, Peter Doran of Louisiana Tech University, Andrew Fountain of Portland State University, William Lyons of Ohio State University, John Priscu of Montana State University, Cristina Takacs-Vesbachh of the University of New Mexico and Martijn Vandegehuchte of Colorado State University.