Paleoclimate Inferred from Lake Sediment Cores in Taylor Valley, Antarctica

极地计划，为麦克默多干谷湖泊沉积物岩心的研究提供资金。干谷湖泊的水位波动历史悠久，反映了区域气候变化。湖泊水位波动的历史一般从LGM -早全新世到古湖泊沉积物中埋藏有机质的14C年。然而，可获得的最年轻的古湖泊沉积物在距今8000至9000年的14C年之间，这表明在全新世的大部分时间里，湖泊的水位处于或低于现在的水平。因此，关于全新世湖泊历史和气候控制的任何信息都主要包含在底部沉积物中。该项目将尝试从麦克默多LTER站点研究的一系列封闭盆地干河谷湖泊的沉积物岩心中提取古气候信息。这项工作涉及多种方法来确定沉积物的年代，并使用几种气候代理方法从南极湖泊沉积物中提取世纪至千年尺度的年代学。本研究利用LTER在过去八年中获得的关于湖泊过程的知识来校准湖泊沉积物的气候代用物。湖深和冰厚的代用物在很大程度上受夏季气候的控制，是这项工作的重点。本研究主要关注四个关键问题：1。干谷湖沉积物记录全新世环境和气候变化的敏感性有多高？2. 在全新世一个世纪和千年尺度上干谷的古气候变化是什么？特别是，1200年的蒸发事件是独一无二的，还是在记录中有其他类似的事件？3. 全新世中期（距今7000年至5000年）的气候变化是否像在极地其他地方记录的那样发生在干谷？4. 在干谷湖1500年的全新世周期记录中，有没有证据最近在泰勒巨蛋记录中得到认可？岩心收集将在LTER支持下进行，使用最先进的冲击/活塞覆盖系统，该系统已成功地用于从其他偏远的极地地区回收长岩心（10至20米）。要做的分析包括藻类色素、生物硅、基本地球化学、有机和无机碳和氮含量、碳、氮和氧的稳定同位素、碳酸盐相、盐含量和矿物学以及晶粒大小。此外，该项目将采用多计时器方法，通过光激发发光，226Ra/230Th， 230Th/234U和14C技术来评估核心的年龄。使用u系列技术的新实验将进行，以便在干谷湖泊沉积物中获得更高的精度。化合物特定同位素和脂质生物标志物是推断过去湖泊状况的有力工具，也将进行评估。综合这些分析，将为罗斯海地区全新世气候变化提供一个新世纪至千年尺度的连续记录。

Polar Programs, provides funds for a study of sediment cores from the McMurdo Dry Valley lakes. The Dry Valley lakes have a long history of fluctuating levels reflecting regional climate change. The history of lake level fluctuations is generally known from the LGM to early Holocene through 14C dates of buried organic matter in paleolake deposits. However, the youngest paleolake deposits available are between 8000 to 9000 14C yr BP, suggesting that lake levels were at or below current levels for much of the Holocene. Thus, any information about the lake history and climate controls for the Holocene is largely contained in bottom sediments. This project will attempt to extract paleoclimatic information from sediment cores for a series of closed-basin dry valley lakes under study by the McMurdo LTER site. This work involves multiple approaches to dating the sediments and use of several climate proxy approaches to extract century to millennial scale chronologies from Antarctic lacustrine deposits. This research uses knowledge on lake processes gained over the past eight years by the LTER to calibrate climate proxies from lake sediments. Proxies for lake depth and ice thickness, which are largely controlled by summer climate, are the focus of this work. This study focuses on four key questions: 1. How sensitively do dry valley lake sediments record Holocene environmental and climate variability? 2. What is the paleoclimatic variability in the dry valleys on a century and millennial scale throughout the Holocene? Especially, is the 1200 yr evaporative event unique, or are there other such events in the record? 3. Does a mid-Holocene (7000 to 5000 yr BP) climate shift occur in the dry valleys as documented elsewhere in the polar regions? 4. Is there evidence, in the dry valley lake record of the 1500 yr Holocene periodicities recently recognized in the Taylor Dome record? Core collection will be performed with LTER support using a state-of-the-art percussion/piston corer system that has been used successfully to retrieve long cores (10 to 20 m) from other remote polar locations. Analyses to be done include algal pigments, biogenic silica, basic geochemistry, organic and inorganic carbon and nitrogen content, stable isotopes of carbon, nitrogen, and oxygen, carbonate phases, salt content and mineralogy, and grain size. In addition this project will pursue a multi-chronometer approach to assess the age of the core through optically-stimulated luminescence, 226Ra/230Th , 230Th/234U, and 14C techniques. New experimentation with U-series techniques will be performed to allow for greater precision in the dry valley lake sediments. Compound specific isotopes and lipid biomarkers , which are powerful tools for inferring past lake conditions, will also be assessed. Combined, these analyses will provide a new century to millennial scale continuous record of the Holocene climate change in the Ross Sea region.