Paleoclimate Inferred from Lake Sediment Cores in Taylor Valley, Antarctica

从南极洲泰勒谷湖沉积物岩心推断的古气候

• 批准号: 0126270
• 负责人: Peter Doran
• 金额: $ 9.98万
• 依托单位: University of Illinois at Chicago
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-08-01 至 2006-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0126270&HistoricalAwards=false
• 关键词: Paleoclimate; Inferred; Lake; Sediment; Cores

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.

极地计划，为麦克默多干谷湖泊的沉积物岩心研究提供资金。干谷湖泊水位波动反映区域气候变化的历史由来已久。通过对古湖泊沉积物中埋藏有机质的14 C测年，人们普遍了解了从末次冰期到全新世早期的湖平面波动历史。然而，最年轻的古湖泊沉积物之间的8000至9000年14 C BP，这表明湖泊水位处于或低于目前的水平，大部分的全新世。因此，有关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。该项目将试图从麦克默多LTER站点正在研究的一系列封闭盆地干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，并使用几种气候代用方法来提取南极湖泊沉积物的世纪至千年尺度的年表。这项研究利用LTER在过去八年中获得的湖泊过程的知识来校准湖泊沉积物的气候代理。湖泊深度和冰厚度的代理，这在很大程度上是由夏季气候控制，是这项工作的重点。本研究主要围绕四个问题展开：1.干旱河谷湖泊沉积物记录全新世环境和气候变化的敏感性如何？2.在整个全新世，干河谷在世纪和千年尺度上的古气候变化是什么？特别是，1200年的蒸发事件是唯一的，还是有其他这样的事件记录？3.中全新世（7000年至5000年BP）气候变化是否发生在极地地区其他地方记录的干旱山谷？4.有证据表明，在干旱河谷湖泊记录的1500年全新世周期最近在泰勒圆顶记录承认？ 岩心采集将在长距离采集试验的支持下进行，使用最先进的撞击/活塞取芯器系统，该系统已成功用于从其他偏远极地地点取出长岩心（10至20米）。要进行的分析包括藻类色素、生物硅、基础地球化学、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粒度。此外，该项目还将采用多计时器方法，通过光激发光、226 Ra/230 Th、230 Th/234 U和14 C技术评估地核的年龄。将使用U系列技术进行新的实验，以提高干谷湖泊沉积物的精度。化合物的特定同位素和脂质生物标志物，这是推断过去的湖泊条件的有力工具，也将进行评估。综合起来，这些分析将提供一个新的世纪到千年尺度的罗斯海地区全新世气候变化的连续记录。