Geologists use lichens to track recent climate change

November 07, 2001

Cincinnati -- There is little question that many of the Earth's great glaciers have been retreating since the Little Ice Age reached its most recent advanced position in the mid 1800s. The bigger questions remain. How fast has that change occurred, and were the dramatic changes reported in Europe similar in other parts of the world?

Katie Schoenenberger, a recent UC master's graduate now at the University of Dayton has turned to lichens in hopes of getting answers. In a poster presentation Wednesday afternoon Nov. 7 at the annual meeting of the Geological Society of America, Shoenenberger will explain how a modified version of a technique called lichenometry can help track the most recent glacial changes.

Traditional geological dating methods aren't always useful in tracking such recent climate changes. Radiocarbon dating doesn't always work, and neither does a technique called denodrochronology which relies on counting tree rings. There aren't always trees to measure, which rules out using that technique in some areas.

It turns out tiny, but durable little lichens might serve as a useful biological calendar for the time period up to 300 years ago. Lichens are hardy combinations of fungi and algae that can grow on rocks and live for hundreds of years. Rhizocarpon geographicum, the lichen used in the technique, is widespread in areas where glaciers have recently retreated and grows at a relatively constant rate. So, Schoenenberger set out to create a geologic time clock based on lichen sizes.

Schoenenberger has sampled lichen populations in New Zealand, Iceland and the Canadian Rockies over the last two years. This August, she sampled four different glaciers in south central Alaska with the help of students from the University of Cincinnati.

"The idea is to sample the whole population to reduce error," explained Schoenenberger. The previous lichenometry technique focused solely on the largest lichen in a particular area.

In her presentation, Schoenenberger will demonstrate how lichen size can be used to track the retreating glaciers in New Zealand. She was also able to confirm her findings using historic records and other dating techniques. Now, she hopes to establish a similar calibration curve for North American glaciers.

Schoenenberger worked in collaboration with University of Cincinnati geology professor Thomas Lowell and Jessica Black from the University of Maine. Lowell said the work should help answer questions about how severe the Little Ice Age was in less populated areas of the world. "There's a people filter Katie's trying to eliminate. The traditional view is that Europe was hit hardest, but that's also where most of the population was at the time."

The ultimate goal of the research is a better understanding of how quickly climate can change and whether there are differences in the Northern and Southern Hemispheres. Lowell and UC geology student Janelle Sikorski will return to New Zealand in late December for two months of fieldwork around Mt. Cook and a meeting on climate change in the Southern Hemisphere sponsored by the Abrupt Climate Change Consortium. The consortium is funded by the National Oceanic and Atmospheric Administration (NOAA).

University of Cincinnati

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