Collaborative Research: P2C2--Hydroclimatic Response of El Nino-Southern Oscillation to Natural and Anthropogenic Radiative Forcing

本项目旨在从现有的环年柚木（柚木）中提取纤维素，开发δ氧-18同位素数据系列。f.）来自印度尼西亚南苏拉威西省穆纳的树芯样本。 初步结果表明，Muna oxygen-18是ENSO相关降水变化的一个指标，但具有较高的信噪比。由于Muna收集包含多达44个交叉日期的增量核心，研究人员将使用同位素采样，每年6次重复，对1656-2005年的样本进行年度分辨率。 这是一个350年的时间间隔，跨越工业化前和人为温室气体和土地覆盖/土地利用变化的强迫水平，爆炸性火山和太阳强迫的多重实现，以及净强迫最小的年份。同位素数据的解释将测试现有的代理传感器模型，使用气象数据，降水氧-18同位素数据的新集合，和参数敏感性研究。复合纤维素氧-18同位素响应和不确定性估计将使用估计的外部辐射强迫估计相同的时间间隔。研究人员将使用叠加历元分析来测试推断的ENSO事件返回间隔和振幅是否无差异，包括非强迫年份、火山事件年份、太阳强迫几十年以及气溶胶的工业化前、过渡和人为时间窗口，土地使用/潜在的更广泛的影响包括可能提供一种新的分析技术，用于相对未开发和潜在的关键热带气候档案，支持美国指导的研究生和马里兰州大学本科生的国际研究经验，以及支持研究生该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

This project aims to develop delta oxygen-18 isotope data series from cellulose extracted from an existing collection of ring-dated teak (Tectona grandis L. f.) tree core samples from Muna, South Sulawesi, Indonesia. Preliminary results suggest that Muna oxygen-18 is an indicator of ENSO-related precipitation variation, but with a higher signal-to-noise ratio. Because the Muna collection contains up to 44 cross-dated increment cores, the researchers will use isotopic sampling at annual resolution with 6 replicates per year, on samples available for the years 1656-2005. This is a 350-year interval spanning both pre-industrial and anthropogenic greenhouse gas and land cover/land use change forcing levels, multiple realizations of explosive volcanic and solar forcing, and years for which net forcing is minimal.Interpretation of the isotopic data will be tested against existing proxy sensor models using meteorological data, a new collection of precipitation oxygen-18 isotope data, and parameter sensitivity studies. Composite cellulose oxygen-18 isotope response and uncertainty estimates will be derived using estimates of the external radiative forcings estimated for the same time interval. The researchers will test the null of no difference in inferred ENSO event return interval and amplitude using superposed epoch analysis for unforced years, volcanic event years, solar-forced decades, and pre-industrial, transitional and anthropogenic time windows for aerosol, land use/change and greenhouse gas forcings.The potential Broader Impacts include possibly providing a new analytical technique to apply to relatively untapped and potentially critical climate archives of the tropics, support of U.S. mentored international research experiences for graduate and capstone undergraduate students at the University of Maryland, as well as support for a graduate studentThis award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.