UA Professor Helps Discover Theory in How Glaciers Influenced Land Formations

Dr. Sarah Praskievicz

Dr. Sarah Praskievicz

From the January 2016 Desktop News | Dr. Sarah Praskievicz, an assistant professor of geography at UA, recently used a forecasting model she co-developed to discover what the Oregon Coast Range might have looked like more than 25,000 years ago.

Praskievicz originally designed the model while pursuing her doctorate at the University of Oregon in order to look at the impact of climate change on river systems in high-elevation regions. But, wanting to better understand how frost shapes lower-elevation regions, Praskievicz recently used the model in a collaborative study with Dr. Jill Marshall of the University of California at Berkeley. Their research is published in Science Advances.

To jumpstart the project, the researchers analyzed sediment from Oregon’s Little Lake, a uniquely undisturbed landmass in an otherwise tectonically active area. Their analysis revealed previously unknown information about the prehistoric terrain: First, the rate of erosion during the last ice age more than doubled the current rate in the area. Second, the vegetation of the time was more indicative of modern-day Alaska than of Oregon.

With these clues, the team began to picture the climate more accurately.

“It was like an open meadow with spruce you would see in maritime Alaska,” Praskievicz 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.”

Though prehistoric Oregon was devoid of glaciers, the study shows that cold climate processes, like frost-cracking, were occurring and changing landscapes, including in Oregon, more than 200 miles from the location of the glaciers.

The team also determined that the temperatures in prehistoric Oregon were far colder—as much as 18 degrees Fahrenheit—than modern temperatures.

“That’s something global models can’t tell us,” Praskievicz said. “By looking at these relationships, we can get a better sense of these highly local impacts.”

While most of the previous research covering the last ice age measured the direct impact of ice sheets on climate, and most of the non-glaciated terrain focused on how precipitation shaped the land, Praskievicz’s research focuses on how temperature itself has affected non-glaciated terrains.

According to Praskievicz, researchers will be able to use the techniques from her study to estimate future changes in climate. 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.