Montana State researchers receive grant to study Alaskan permafrost

BOZEMAN - As the climate warms in high latitudes, Montana State University scientists are studying hillslopes in Alaska as they search for clues about past and present geologic processes that may help predict future effects of permafrost thaw.

Jean Dixon, associate professor in the Department of Earth Sciences in the College of Letters and Science, and Stephanie Ewing, professor in the Department of Land Resources and Environmental Sciences in the College of Agriculture, recently were awarded the bulk of a three-year, $850,000 grant from the National Science Foundation to study how landscapes change in permafrost environments.

Dixon, Ewing and two MSU doctoral students are using the funding to map and drill through frozen soils to determine the ages of ice and sediments. They'll then study the changes and movements of organic carbon in the soils over the past 100,000 years. The project also will provide research opportunities for two MSU undergraduate students.

Over half of Earth's soil carbon is stored in permafrost, which is defined as subsurface soil that remains frozen for at least two consecutive years. Dixon and Ewing say permafrost thawing rapidly at high latitudes could release carbon dioxide into the atmosphere and lead to irreversible ecological change. Thawing also may adversely affect infrastructure due to decreased soil stability and change landscape form and hydrology.

Scientists already know that, as soils move, they may both store and release carbon, but many questions remain about how that occurs in permafrost.

"There's a fundamental knowledge gap of past processes," said Dixon, whose primary research interest is geomorphology, the study of landforms and their evolution. "How much carbon is stored? What controls its distribution? How old is the ice?"

Answers to such questions can't be found easily, the researchers say. Ewing, a soil scientist, explained that ground ice forms and thaws in cold northern climates according to changing insulation levels on the ground that are influenced by the growth of moss layers and deposition of sediment. On hillslopes, which make up nearly half of the permafrost-covered regions of Alaska, ground ice may stabilize sediment; additionally, sediment movement due to gravity may change ground temperatures, burying and unburying stored soil carbon. As a result, adjacent ice and sediments may be close to the same age, or quite different in age, as a function of topography.

"Ice comes and goes in these dynamic landscapes," said Ewing, adding that thaw can generate rapid change by moving large amounts of sediment. "Thaw upslope could reveal carbon but then move down and bury other carbon, forming new ice."

Other geologic factors, such as cryoturbation - the mixing of materials from various layers of soil due to freezing and thawing - pose additional challenges in determining timing and deposition of sediments.

For those reasons, Ewing and Dixon will collect and analyze field samples to quantify permafrost evolution from tens of thousands of years ago to the modern day. They plan to use advanced techniques, including uranium isotope measurements to learn how long portions of the ground ice have been frozen; luminescence dating, which can determine how long sediments have been buried; and meteoric beryllium isotope analysis, which is useful in estimating soil erosion rates.

The MSU researchers have begun their fieldwork at a site near Fairbanks and will return at different times of year to collect data. Dixon and Ewing have research partners at the University of Alaska Fairbanks, which received $150,000 of the NSF grant. Because 40% of the ground in the Fairbanks area is frozen, geologists in Alaska are concerned about the effects of thaw on ground stability.

Dixon and Ewing say there is no time to waste because hillslopes with ice in interior Alaska are rapidly "unzipping," meaning that they have begun to thaw and are no longer holding sediments together.

"During a modern thaw, on a single hillslope, we can lose 80,000 years of ice," Dixon said. "The work is timely. People are racing to understand how permafrost is changing."