Earth’s climate system has changed dramatically in the past. Figure 1 shows a reconstruction from the Last Glacial Maximum (20,000 years ago) illustrating the large ice sheets (more than 3 km thick) that covered North America and Northern Europe at that time and the corresponding temperatures changes.
Figure 1. Climate reconstruction of the Last Glacial Maximum (LGM). Colors show the surface temperature difference LGM minus today. Ice sheet height is indicated by contour lines every 500 m (from PMIP3). The temperature reconstructions are from MARGO (2009), Bartlein et al. (2010) and Shakun et al. (2011) as described in Schmittner et al. (2011).
Reconstructions of past changes in climate and biogeochemical cycles are important to understand how the climate system works and how its components (atmosphere, ocean, cryosphere and biosphere) interact with each other. They also may hold the key to better predict future climate. Since measurements with reliable instruments are available only for the last 150 years, indirect methods are used to infer prior variations.
Temperatures of the ocean surface, for example, are reconstructed using fossils of marine microorganisms found in sea floor sediments (Figures 2 & 3).
- Figure 2. Multi corer.
- Figure 3. Ocean sediment core.
Concentrations of greenhouse gases such as carbon dioxide and methane are measured in bubbles of air trapped in ancient ice (Figures 4-6).
- Figure 4: Ice core.
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- Figure 5: Needles used to crush ice for the extraction of air in bubbles.
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- Figure 6: Bubbles of air in ice from a polar ice core.
Isotopic measurements of cave deposits reveal changes in precipitation (Figures 7 & 8).
- Figure 7. Alan Mix taking dripwater samples in a cave.
- Figure 8. Cave.
Glacial deposits on land such as moraines and erratic bolders can be dated to reconstruct the extent of past glaciers (Figures 9 & 10).
- Figure 9. Wallowa moraines.
- Figure 10. Yellowstone moraine.
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Figure 11: Simulation of surface temperature changes at the LGM with the global climate model OSUVic. Compare to Figure 1.
Paleoclimate research is a major strength at OSU, combining the efforts of several faculty in the Department of Geosciences and College of Ocean and Atmospheric Sciences. Current research focuses on Pliocene to Holocene problems, and includes studies of the terrestrial glacial geologic record, paleoceanography from the marine sediment record, speleothems, ice cores, and state of the art paleoclimate modeling. Modern laboratories for isotopic work, trace element analysis, ice core gases, cosmogenic nuclide dating, and computing are maintained for student and faculty research.
Combining these observations with model simulations (Figure 11) allows testing hypotheses about forcing mechanisms of and interactions within the climate system.
