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

[809150 . banerjeh]该项目的主要目标是提供关于阿拉斯加当地和区域在过去14000年中对气候变化的响应的新的、高时间分辨率的数据。为此，我们将用岩石磁性、化学和粒度法分析阿拉斯加西南部（祖父、Ongivinuk）的两个湖相层序和碎屑输入。高灵敏度磁信号还将与我们现有的（部分发表的）同一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，现在主要基于花粉数据，将得到验证和纠正。在该项目的最后阶段，改进后的记录将与北大西洋和格陵兰岛类似高纬度地区的气候记录进行比较。初步研究表明，在晚冰期-全新世过渡、全新世开始和7500年前植被繁茂的到来期间的短暂热波动都可以在目标湖泊沉积物的一些磁性特征中看到。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指标，可以从碎屑信号中分离出原位氧化和还原过程，并可以估计出磁性粒度。通过化学元素分析、非磁性粒度测定和穆斯堡尔谱来验证这些代用物，并将这些代用物与现有的植被数据进行比较，将使我们能够重建过去14000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.