Open Access Thesis
Master of Science (M.S.)
Year Degree Awarded
Month Degree Awarded
Future impacts from climate change can be better understood by placing modern climate trends into perspective through extension of the short instrumental records of climate variability. This is especially true for extreme climatic events, such as extreme precipitation and wildfires, as the period of instrumental records provides only a few examples and these have likely have been influenced by anthropogenic warming. Multi-parameter records showing the past range of climate variability can be obtained from lakes. Lakes are particularly good recorders of climate variability because sediment from the surrounding environment accumulates in lakes, making them sensitive recorders of climate variability and providing high-resolution histories of local environmental conditions in the past. In some cases, such as at Basin Pond, sediment is persevered efficiently enough to produce distinguishable annual laminations (varves) in the sedimentary record. The varved record at Basin Pond was used to construct an accurate, highly-resolved age-to-depth model over the past 300 years.
Using a multi-proxy analysis, including organic biomarker analysis of molecular compounds and sedimentological features preserved in the sediment record, a history of environmental and climatic change at Basin Pond was constructed. These analyses were compared with the record of known extreme events (from instrumental measurements and historical documents), including 129 years of high-resolution precipitation and temperature meteorological data, 19 tropical systems over the past 145 years, and two known wildfire events over the past 200 years. Long-term trends in precipitation, including the increase in precipitation seen throughout the last half of the 20th century and the drought of the 1940’s, were captured in the analysis of long-chain n-alkane distributions and through varve thickness measurements obtained through X-Ray Fluorescence analysis. Furthermore, Polycyclic Aromatic Hydrocarbons (PAHs), a class of organic compounds that can be used to trace combustion activity, were found in abundance in the Basin Pond sedimentary record. Peaks in the abundances of two PAHs (retene and chrysene) and the ratio retene/(retene + chrysene) were found to be highly correlated with the known wildfire events occurring in the historical period, giving promise as using these compounds and ratio as a robust proxy for regional wildfire events in the northeastern U.S.
Raymond S Bradley
Miller, Daniel R., "A High-Resolution Paleoenvironmental and Paleoclimatic History of Extreme Events on the Laminated Sediment Record from Basin Pond, Fayette, Maine, U.S.A." (2015). Masters Theses. 286.