UC Riverside Study Shows Glaciers Once Existed Near Los Angeles

Lewis Owen, associate professor of geology in the department of earth sciences at UC Riverside, reports these findings in the August issue of Geology in a paper entitled "Extreme southwestern margin of Late Quaternary glaciation in North America: timing and controls." The work has implications for reconstructing past climate to aid our understanding of future climate change.

The research provides the first dates on glaciation in the southernmost region of North America and shows that glaciers existed as recently as 5,000-10,000 years ago. Results of the UC Riverside study allow researchers to determine the nature of climate change using reconstruction of the glaciers and comparing these with present climatic data on similar size glaciers that exist in other mountain regions today. These results can be used to test the validity of computer models for predicting future climate change by running experiments on past climatic conditions. This, in turn, is helpful for predicting and modeling future environmental change and testing the reliability of the models.

"We found evidence for many glaciations in the southern region of North America over the last 20,000 years," said Owen. "Higher precipitation occurred during glacial times that fell as snow to allow glaciers to grow in this southwestern most region. Moreover, we found that glaciation here occurred at the same time as glaciation in other regions of the Americas."

Owen explained that with global climatic warming after the last glaciation (~10,000 years ago) taking us into the present interglacial, the glaciers melted away, but a cold or wetter phase during the early part of the interglacial allowed them to grow again, albeit only on a very small scale.

The research, performed during 2000-2003, was funded by a Western Center grant and used 'cosmogenic radionuclide dating' to help define the timing of past glaciations with better accuracy. The research involved extensive fieldwork, including mapping and collecting samples. Samples were analyzed in laboratories at UC Riverside and Lawrence Livermore National Laboratory (LLNL), Calif.

Other coauthors of the Geology paper are Robert Finkel, Richard Minnich, and Anne Perez of the department of earth sciences at UC Riverside. Finkel is based also at LLNL.