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

该项目旨在开发从印度尼西亚南苏拉威西穆纳现有的年轮测定柚木（Tectona grandis L. f.）树芯样品中提取的纤维素的δ氧-18同位素数据系列。初步结果表明，Muna oxygen-18是enso相关降水变化的一个指标，但信噪比较高。由于穆纳收集了多达44个交叉年代的增量岩心，研究人员将对1656年至2005年的样品进行年度分辨率的同位素采样，每年重复6次。这是一个350年的时间间隔，涵盖了工业化前和人为温室气体和土地覆盖/土地利用变化强迫水平，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通过现有的代理传感器模型进行测试，该模型使用气象数据、降水氧-18同位素数据的新收集以及参数敏感性研究。复合纤维素氧-18同位素响应和不确定性估计值将使用同一时间间隔估计的外部辐射强迫估计值推导。研究人员将利用非强迫年、火山事件年、太阳强迫年以及气溶胶、土地利用/变化和温室气体强迫的工业化前、过渡性和人为时间窗口的叠加年代分析，检验推断ENSO事件返回间隔和振幅无差异的零值。潜在的更广泛的影响包括可能提供一种新的分析技术，应用于相对未开发的和潜在的关键热带气候档案，支持美国指导的马里兰大学研究生和顶点本科生的国际研究经验，该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.