Holocene Climate Change in Southwestern Patagonia: New Insights from Large Lake Paleolimnology

巴塔哥尼亚西南部全新世气候变化：大湖古湖泊学的新见解

• 批准号: 1103550
• 负责人: Robert Dunbar
• 金额: $ 59.23万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-04-15 至 2015-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1103550&HistoricalAwards=false
• 关键词: Holocene; Climate; Change; Southwestern; Patagonia

This project combines climate system modeling and field data collection to examine causes and expressions of Holocene climate change in Southern South America. This is the only significant land mass that extends into the core of the southern westerly wind field, the most energetic wind system on Earth. The project is collects information on past climate change from Lago Sarmiento, a large closed-basin alkaline lake located at 51°S. Precipitation in the area, and therefore the hydrology and water balance of the lake, is demonstrably controlled by the intensity of the wind field. Abundant carbonate sediments are present and they precipitate in equilibrium with lake waters. These sediments are analyzed using stable isotope and trace element methods to reconstruct past variations in moisture balance. An excellent chronology can be developed using a combination of AMS radiocarbon, an existing tephrochronology, and U/Th. Lago Sarmiento is located adjacent to Lago del Toro, a similar but open-system lake, as well as a marine fjord of the SW Chilean archipelago. Additional core samples from these systems are being collected and will enable the project to deconvolve the effects of changing temperature, precipitation, and evaporation. The project will use three methods to reconstruct westerly wind variability at this site. The 1st method exploits the strong connection between lake hydrology and oxygen isotope fractionation of biogenic carbonate phases. The 2nd uses carbon isotopes to constrain periods of lake stratification due to reduced wind stress on the lake. The 3rd involves grain size analysis of sediments in areas affected by wind wave-driven redeposition. By combining geochemical & sedimentological methods the project develops high resolution paleoclimate records that provide important information on Holocene climate variability. The study also includes a substantial modeling component, using a General Circulation Model and an embedded high resolution regional climate model to identify climate forcings and feedbacks and for model-data intercomparison.Broader Impacts and Significance. The project delivers a well-dated Holocene chronology of past variability in rainfall, water balance, and temperature from the Pacific margin of southwestern Patagonia. The record is of high intrinsic value as few high quality climate reconstructions are available from the core of the southern westerly wind field. However, the greatest merit comes from model-data intercomparisons and modeling experiments where the causes of climate change in the SE Pacific over timescales of centuries to millennia are examined. Results aid in climate forecasting for southernmost South America, particularly with regard to water availability. The Holocene westerly wind reconstructions should also provide a useful constraint in climate studies throughout the Southern Ocean. One benefit is likely to be an improved understanding of the capacity of the Southern Ocean to take up anthropogenic carbon dioxide. Benefits to society include greater knowledge of climatic influences on water balance (directly important to farmers, ranchers, & land-use planners in Chile & Argentina) as well as better understanding of how atmospheric flow may be related to global climate change and how it interacts with the ongoing rise in atmospheric CO2 levels. During the project two 1-week workshops for North & South American graduate students, post-doctoral fellows, and new faculty members on: 1) Large lake limnology, sedimentology and stratigraphy, & 2) Tools for examining past variability in the hydrologic cycle are being organized.

该项目结合了系统建模和现场数据收集，以检查南南南部南部南部南南南南南南南部的南南南部南南南南南南南部的气候变化的原因和表达。在南部风扇区的核心中，地球上最能量的风系统是从该地区拉戈·萨米恩托（Lago Sarmiento碳酸盐沉积物是一段时间的E同位素和trement方法从系统中收集了群岛，将使该项目的效果变化，并在现场蒸发。阶段。第二阶段使用碳的同位素来限制湖泊上的风应力。关于全新世的细胞，该研究还包括一个大量的建模循环模型和一个嵌入式的高分辨率调节模型，以识别气候强迫和反馈和模型数据。西南巴塔哥尼亚（Patagonia）的降雨，水平和温度的差异。在千禧一代的时间表上，跨二线危险限制了，在整个南部的气候研究中，pary和模型的c。 Takean到二氧化碳的二氧化碳。 ON：1）大型湖泊林格学，沉积学和地层学＆2）正在组织检查水文周期中过去变异性的工具。