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

该项目的主要目标是提供关于阿拉斯加过去14,000年来当地和区域气候变化响应的新的、高时间分辨率的数据。为此，阿拉斯加西南部的两个湖泊序列(祖父和翁吉维努克)和碎屑输入将通过岩石磁学、化学和粒度方法进行分析。高灵敏度的磁信号也将与我们现有的(和部分出版的)来自相同地点的花粉和沉积学记录进行比较。由于这种跨学科的方法，阿拉斯加晚更新世和全新世平均气候记录的质量和复杂性将得到验证和校正，目前主要基于花粉数据。在该项目的最后阶段，这一改进的记录将与北大西洋和格陵兰类似高纬度的气候记录进行比较。初步研究表明，在冰川-全新世晚期过渡、全新世开始以及7500年前更茂盛的植被到来期间，在目标湖泊沉积物的一些磁性特征中都可以看到短暂的热波动。这表明磁信号准确地反映了环境的变化。通过使用附加的磁性替代物，可以从碎屑信号中分离出原位氧化和还原过程，并且还可以估计磁性颗粒的大小。通过化学元素分析、非磁性粒度测定和穆斯堡尔谱验证这些替代，并将这些替代与现有的植被数据进行比较，将使我们能够重建过去14,000年的高分辨率气候记录。

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.