UA Professor Helps Discover Theory in How Glaciers Influenced Land Formations

TUSCALOOSA, Ala. – A University of Alabama geographer’s forecasting model has helped determine heavily glaciated areas in North America more than 25,000 years ago significantly affected temperatures and land formations in unglaciated areas more than 200 miles away.

Dr. Sarah Praskievicz, UA assistant professor of geography, was tasked with determining what the climate was like in the Oregon Coast Range during the Last Glacial Maximum, close to 21,000 years ago, for a collaborative study titled “Frost for the trees: Did climate increase erosion in unglaciated landscapes during the late Pleistocene?”

The study, published in the Nov. 27 issue of Science Advances, was led by Dr. Jill Marshall, of the University of California at Berkeley. Praskievicz and Marshall collaborated on the study while both were at the University of Oregon.

Praskievicz said future and past climates are typically simulated via global computer models, many of which are too coarse to determine how a climate would vary within a specific area, like a mountain range.

Praskievicz used a model she co-developed while pursuing her doctorate at the University of Oregon, in which she uses elevation to predict climate output while studying the impacts of climate change on river systems in high elevation regions.

Researchers on this study started with a sediment core from Little Lake in the Oregon Coast Range that showed erosion rates more than doubled compared to the present day and vegetation indicative of a cold climate during the Last Glacial Maximum. Researchers discovered that areas hundreds of miles away from a glaciated area were directly affected by the climate changes associated with it, likely over multiple glacial cycles.

Temperatures were far colder, as much as 18 degrees F, than modern temperatures, which influenced the land’s vegetation and the formation of the land through ice fracturing bedrock to produce sediment.

“It was like a open meadow with spruce you would see in maritime Alaska,” she said. “We see these cold climate species, and it tells us something about the setting, which drives these models. We run the model and see the temperatures they predict and compare it to the data from sediment cores.

“That’s something global models can’t tell us, like what kind of temperature changes will occur in a specific location. By looking at these relationships, we can get a better sense of these highly local impacts.”

Praskievicz’s research focuses primarily on future climate change and the interaction between climates, hyrdrology, river flow and sediment transport. She’s particularly interested in how large-scale climatic changes are affecting processes, in this case, frost-cracking and sediment, at a local scale.

Most of the research in this time period has measured the direct impact of the ice sheet on climate. Other research on non-glaciated terrain has focused on precipitation and how it shapes land, like river terraces and flood plains.

There hasn’t been as much research focusing on how temperature, itself, has affected non-glaciated terrains, Praskievicz said. The study shows that the cold climate processes, like frost-cracking, were occurring and changing the landscape more than 200 miles from the location of the glacier.

“What was helpful of this study was a validation of the approach,” she said. “I’ve used modern day outputs to compare to observed weather station data, but this was taking it and applying it to a very different environment, and it appears to hold up.”

Praskievicz said the same technique that researchers used to estimate temperatures in the Oregon Coast Range during the Last Glacial Maximum can also be used to estimate changes in temperature and precipitation associated with future climate change.

She said that by using the relationship between elevation and climate, researchers can adjust the resolution of global climate models to provide more detailed projections of temperatures and precipitation changes in specific locations.