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.

该项目结合了气候系统建模和现场数据收集，以检查南美南美全新世气候变化的原因和表达。这是唯一延伸到西南风场的核心的唯一重要土地，这是地球上最有活力的风系统。该项目是收集有关Lago Sarmiento过去气候变化的信息，Lago Sarmiento是一个位于51°S的大型封闭式湖泊。该区域的降水，因此湖泊的水文学和水平衡有效地由风场的强度控制。存在丰富的碳酸盐沉积物，它们与湖水的平衡中珍贵。使用稳定的同位素和痕量元素方法对这些沉积物进行分析，以重建水分平衡中过去的变化。可以使用AMS放射性碳，现有的Tephroanology和U/TH的组合来开发出色的年表。 Lago Sarmiento位于​​Lago del Toro附近，Lago del Toro是一个类似但开放系统的湖泊，也是SW智利Archivelago的海洋博览会。正在收集这些系统中的其他核心样品，并使该项目能够解除温度，降水和蒸发的影响的影响。该项目将使用三种方法在此站点重建西方风变异性。第一种方法利用了湖泊水文学和氧同位素分馏之间的牢固联系。第二次使用碳同位素来限制由于湖上的风应力减少而导致的湖泊分层周期。第三次涉及在受风波驱动重新沉积影响的区域中沉积物的晶粒尺寸分析。通过结合地球化学和沉积学方法，该项目开发了高分辨率的古气候记录，这些记录提供了有关全新世气候变异性的重要信息。该研究还包括使用通用循环模型和嵌入式高分辨率区域气候模型的实质建模组件，以识别气候强迫和反馈，以及模型数据对比比较。该项目提供了日期良好的全新世年代学，该项目从巴塔哥尼亚西南部太平洋地区的降雨量，水平和温度中的过去变异性。该记录具有很高的内在价值，因为很少有高质量的气候重建可从西部西部风场的核心获得。然而，最大的优点来自模型数据对比和建模实验，在这些实验中，检查了SE太平洋气候变化的原因，而在数百年来一直到千年。结果有助于对南美南部最南端的气候预测，特别是关于水的供应。全新世西方风重建也应在整个南大洋的气候研究中提供有用的冲突。一个好处可能是对南大洋占用人为二氧化碳的能力的一种改进的理解。对社会的好处包括对气候对水平平衡的更多了解（对智利和阿根廷的农民，牧场主和土地利用规划师至关重要），以及对大气流程如何与全球气候变化相关的方式以及它与大气CO2水平的持续增长相互作用。在项目期间，北美研究生和南美研究生的两个为期1周的研讨会，博士后研究员以及新的教职员工：1）大型湖泊林科，沉积学和地层学＆2）正在组织水文周期中的过去变异性工具。