ESH: Magnetic Studies of Lake Sediments: Climate Variability in Alaska During the Last 14,000 Years

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9809150BanerjeeThe primary objective of the project is to provide new, high temporal resolution data on local and regional responses to climate change in Alaska during the last 14,000 years.For this purpose two lacustrine sequences in southwest Alaska (Grandfather, Ongivinuk) and detrital input will be analyzed by rock magnetic by rock magnetic, chemical and granulometric methods. The high-sensitivity magnetic signal will also be compared with our existent (and partly published) pollen and sedimentological records from the same sites. Due to this interdisciplinary approach the quality and complexity of the average Late Pleistocene and Holocene climate record of Alaska, now dominantly based on pollen data, will be validated and corrected. In the last stage of this project, this improved record will be compared with the climate records at similar high latitudes in the North Atlantic and Greenland.Preliminary studies show that short thermal fluctuations during the Late Glacial-Holocene transition, the beginning of the Holocene and the arrival of a lusher vegetation 7500 years BP are all visible in some of the magnetic properties of the target lake sediments. This indicates that the magnetic signal accurately reflects environmental changes. By using additional magnetic proxies, in situ oxidation and reduction processes can be separated from the detrital signal, and magnetic grain size can also be estimated. Validating these proxies by chemical elemental analysis, non-magnetic grain size determinations, and Mossbauer spectra and comparing these proxies with the existing vegetational data, will allow us to reconstruct a high-resolution climate record over the last 14,000 years.