From: Montana State University
Posted: Saturday, August 12, 2017
A Montana State University polar scientist has contributed to new research that describes how 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. The study was an interdisciplinary collaboration between scientists from 10 institutions.
The findings, published in the journal Nature Ecology and Evolution, suggest that even abrupt, short-lived climate events can cause long-term alterations in polar regions that unfold over the span of several years and subsequently change the overall trajectory of an ecosystem.
This is especially significant since Antarctica acts as the canary in the coal mine for Earth’s climate, said John Priscu, Regents Professor in the MSU College of Agriculture’s Department of Land Resources and Environmental Sciences and an internationally renowned polar scientist.
“Although climate variability is occurring on a global scale, ecological impacts are often specific, and vary from region to region,” Priscu said. “Climate changes in polar regions are amplified, making these high-latitude areas sentinels for monitoring not only climate variability, but also for the determination of how ecosystems respond to this variability.”
There has been a large focus on temperature warming in the Arctic and its ramifications on geopolitics, human inhabitants and changes in north polar ecosystems, Priscu said. Yet, despite its importance in regulating the planet’s climate, much less is known about Antarctica, the fifth largest continent and repository of approximately 70 percent of Earth’s freshwater.
Additionally, Priscu said, the Antarctic continent and the surrounding ocean represent “coupled components” that both drive and respond to climate.
“Remarkable changes have been observed in Antarctica over the past several decades, including the rapid collapse of ice shelves, changes in penguin populations, and extreme flooding within the polar deserts of the McMurdo Dry Valleys,” Priscu said.
“Our understanding of the mechanisms behind these events is improving, but the complex interactions between the atmosphere, ocean, cryosphere and biosphere are difficult to resolve,” he said. “Changes are occurring faster than predicted only a few years ago, and although the future trajectory remains uncertain, these changes have been projected to alter both marine and terrestrial Antarctic ecosystem structure and function.”
The McMurdo Dry Valleys, or MDV, are the largest ice-free region of Antarctica and are considered a polar desert environment due to their low humidity and scarce precipitation. Now in its 25th year, the National Science Foundation’s McMurdo Dry Valleys Long-Term Ecological Research, or LTER, has provided a continuous multi-decade record of atmospheric and ecological data at the MDV research site.
As principal investigator on the McMurdo LTER project since its inception in 1993, Priscu oversees the work on the physics, chemistry and biology of the lakes, which he has studied for more than three decades
Between 1987 and 2000, the MDV region experienced a period of cooling, during which mean 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 MDV 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 MDV over the following decade, according to the new research.
Priscu said the “flood year” seemed to be a tipping point where lake levels rose sharply and the permanent ice cover thinned from about 15 feet to nine feet.
“The productivity and biodiversity of the ecosystem is now heading in a different direction,” Priscu said. “This may be a preview of what we may see in temperate lakes as air temperature continues to rise. The integration of long-term data presented in our manuscript provides a starting point in our understanding of the cascade of environmental consequences related to rapid climate change on the Antarctic continent.”
Paul Cutler, the NSF program officer for the two LTERs in Antarctica, noted that these results underscore the value of gathering data over decadal time scales.
“The natural world operates in non-linear ways and on many different time scales, from daily cycles to processes that take centuries,” Cutler said. “The LTERs are instrumental in measuring and deciphering these complexities in order to inform basic understanding of ecosystem functioning and to refine predictions of the future of critical ecosystems, particularly in areas like the Dry Valleys, which maintain an ancient, but potentially delicate, ecological balance.”
In addition to the NSF-funded LTER, during Priscu's upcoming season this fall in Antarctica – his 34th-- he will focus on a massive effort to drill down to Subglacial Lake Mercer. As chief scientist for the Subglacial Antarctic Lakes Scientific Access, or SALSA, project, Priscu organized an interdisciplinary team consisting of geomicrobiologists, geochemists, geophysicists, and paleo-sedimentologists from eight U.S. institutions, along with three international collaborators, to directly sample the lake.
Priscu said Antarctica has more than 400 subglacial lakes, but scientists have only directly sampled one – Subglacial Lake Whillans -- so far. Priscu was chief scientist for that project, called WISSARD, an acronym for Whillans Ice Stream Subglacial Access Research Drilling. In 2013, Priscu and a team of scientists drilled half a mile through the West Antarctic Ice Sheet to Subglacial Lake Whillans, which had been covered by ice for hundreds of thousands of years, and collected samples that proved that the subglacial lake contained life and an active ecosystem.
Priscu said Subglacial Lake Mercer is deeper and bigger than Lake Whillans and will provide new information on biodiversity and geochemistry beneath the ice sheet, and provide a novel dataset to determine the stability of the West Antarctic Ice Sheet. The two lakes are approximately 100 miles apart.
During his more than 30 years studying Earth’s polar regions, Priscu has mentored a generation of scientists, including undergraduate students, technicians and numerous graduate students who have completed their degrees studying Antarctic lakes.
“It is these students who will take us through the upcoming decades and address future issues of ice loss and associated sea level rise,” Priscu said.
Other co-authors of the new research include: Lead author Michael Gooseff, Diane McKnight and Eric Sokol of University of Colorado 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; Cristina Takacs-Vesbach of the University of New Mexico; Martijn Vandegehuchte and Diana Wall of Colorado State University and Ross Virginia of the Institute of Arctic Studies at Dartmouth College.
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