Doctoral Dissertation Research: The Nature and Rate of Environmental Change in the Sierra Nevada -- AMS Radiocarbon Analysis of the Pleistocene/Holocene Transition

小行星9406575 关于全球变化的研究侧重于了解当代自然和人类的进程，但一个重要的辅助调查线索是重建变化的历史记录，从而增进对自然进程结果的了解，而人类引起的变化模式现在又叠加在这些自然进程的结果之上。 来自世界各地的古环境记录表明，在大约1万年前从更新世到全新世的过渡时期发生了巨大的变化。 这些变化背后的主要驱动力被认为是全球大气和海洋模式的波动。 然而，为了理解这些过程，更准确的古环境记录是必要的。 本博士论文研究项目将把注意力集中在推进同步记录的变化在内华达州东部的加州在14,000年至9,000年前的这段时间。 从该地区的一些湖泊中提取了沉积物岩心，并确定了岩心中的花粉和宏体化石证据。 使用传统的放射性碳测年技术进行的初步分析表明，这些遗址之间具有很强的同步性。 将通过对针叶树针叶碎片和花粉粒进行更高分辨率的AMS（加速器质谱法）14-C测量来进行更详细的分析。 该项目将提高记录的年代精度，记录内华达州在更新世/全新世过渡期间的环境变化的性质和速率。 特别有价值的是将提高对气候如何突然变化的理解。 作为博士论文改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立研究生涯。

9406575 BYRNE Research on global change has focused on understanding contemporary natural and human processes, but an important ancillary line of inquiry consists of reconstruction of historical records of change, thereby enhancing knowledge of the outcomes of natural processes upon which patterns of human- induced change now are superimposed. Paleoenvironmental records from around the world indicate that dramatic changes took place during the transition from the Pleistocene to Holocene periods roughly 10,000 years ago. The primary driving forces behind these changes are thought to have been fluctuations in global atmospheric and oceanic patterns. More accurate timing of paleoenvironmental records is necessary in order to understand these processes, however. This doctoral dissertation research project will focus its attention on advancing the synchronous record of change in the Sierra Nevada of eastern California over the period from 14,000 years to 9,000 years before the present. Sediment cores have been drawn from a number of lakes in the region, and pollen and macrofossil evidence in the cores have been identifies. Preliminary analyses using traditional radiocarbon dating techniques indicate strong synchroneities among the sites. More detailed analyses will be conducted by making higher-resolution AMS (accelerator mass spectrometry) 14-C measurements on conifer needle fragments and pollen grains. This project will improve the chronological precision of records that document the nature and rates of environmental change in the Sierra Nevada during the Pleistocene/Holocene transition. Of particular value will be improved understanding of how abruptly climates may change. As a doctoral dissertation improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.