History of the Monsoon in Arabia, a Speleothem-based Paleoclimate Study

该奖项调查了阿曼北方和也门洞穴中石笋和其他洞穴沉积物的使用情况，这些石笋和其他洞穴沉积物作为自然档案，以了解过去75，000年间冰期和冰期期间印度洋季风系统变化的性质和原因。印度洋季风是一个重要的天气系统，影响自然和管理的资源（例如，通过农业和渔业），因此，世界上人口最稠密的地区之一的经济。两个问题指导了研究策略，即：1）季风降水如何在间冰期之间变化？季风的时间是如何随纬度变化的？应用的研究策略结合了现代洞穴和洞穴沃茨的研究，现代和古代洞穴沉积物中流体包裹体水的氢同位素分析，现代和古代洞穴沉积物的高分辨率氧和碳稳定同位素分析，以及同位素时间序列的光谱分析。石笋是从洞穴地下水中沉淀出来的碳酸钙沉积物，将用于制作季风降雨量变化的高分辨率记录。降水强度的变化记录在石笋中，表现为生长速率、年生长层厚度（如果存在）以及碳和氧稳定同位素比值的变化。以前使用阿曼洞穴石笋和其他洞穴沉积物的工作表明，它们是气候信息的丰富来源。结果表明，重复的多雨（即，在过去的四个地球气候间冰期的每一个期间，阿拉伯半岛南部的潮湿）时期。对全新世早期的更详细的研究（分辨率约为4年）表明，季风降雨和太阳强迫之间存在密切的对应关系。对过去800年季风的年度分辨率研究表明，在十年和年际时间尺度上，季风与热带太平洋厄尔尼诺-南方涛动（ENSO）系统存在联系。

This award investigates the use of stalagmites and other speleothems from caves in northern Oman and Yemen as natural archives for information on the nature and cause of variations in the Indian Ocean monsoon system during interglacial and glacial periods of the last 75,000 years. The Indian Ocean Monsoon is an important weather system that affects both natural and managed resources (e.g., through agriculture and fisheries) and hence the economy of one of the most densely populated areas of the world. Two questions guide the research strategy, namely: 1) How did monsoon precipitation vary between interglacial periods? and 2) How does the timing of the monsoon vary with latitude? The research strategy applied combines studies of modern caves and cave waters, Hydrogen isotope analyses of water from fluid inclusions in modern and ancient speleothems, high resolution Oxygen and Carbon stable isotopic analyses of recent and well-dated ancient speleothems, and spectral analyses of the isotopic time series. Stalagmites, deposits of calcium carbonate that are precipitated from groundwaters in caves, will be used to produce high-resolution records of variation in monsoon rainfall. Changes in the intensity of precipitation are recorded in stalagmites as variations in growth rate, thickness of annual growth layers (if present) and in carbon and oxygen stable isotope ratios.Previous work using stalagmites and other speleothems from caves in Oman has shown that they are a rich source of climate information. The results demonstrate repeated pluvial (i.e., wet) periods in southern Arabia during each of the past four interglacial stages in Earth's climate. More detailed study of the early Holocene, at a resolution of approximately 4 years, shows a close correspondence between monsoon rainfall and solar forcing. Study of the past 800 years of the monsoon at annual resolution indicate a connection to the tropical Pacific El Nino-Southern Oscillation (ENSO) system on decadal and interannual timescales.This project is multi-national in scope and involves collaborators in Switzerland, Germany, Oman, and Yemen.