Oxygen Isotope Compositions of Tree-Ring Cellulose as a High-Resolution Proxy Record of Hurricane Activity

树轮纤维素的氧同位素组成作为飓风活动的高分辨率代理记录

• 批准号: 0327280
• 负责人: Claudia Mora
• 金额: $ 15万
• 依托单位: University of Tennessee Knoxville
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-09-01 至 2007-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0327280&HistoricalAwards=false
• 关键词: Oxygen; Isotope; Compositions; Tree; Ring

This research will investigate the potential use of the oxygen isotope ratios of alpha cellulose (the basic component of wood tissue) in tree rings of pines from southern Georgia, South Carolina, and coastal Texas as a proxy record of hurricane activity. Organic oxygen isotopes in tree-ring alpha cellulose mainly reflect the isotopic composition of the source water. In shallowly rooted conifers, the source water is directly related to precipitation. Hurricanes produce large amounts of precipitation with distinctly lower oxygen isotope ratios than normal surface water, and these low isotope ratios may persist in surface and soil water for several weeks. These anomalously light oxygen isotopic compositions are likely incorporated into the tree-ring cellulose, capturing an isotopic record of hurricane activity. Hurricanes most typically affect the southeastern United States during August through October, months that correspond to the latewood portion of the individual tree ring. Hurricane activity may result in negative latewood d18O values (the ratio of oxygen-18 to oxygen-16 relative to an internationally accepted standard) and relatively large differences in the isotopic compositions of earlywood and latewood in an annual ring. In years without significant hurricane activity, earlywood-latewood differences are expected to be negligible. The investigators will first separate individual tree rings into sub-annual segments of earlywood and latewood, then resins will be removed. Oxygen isotope compositions of alpha cellulose will be measured using a high temperature carbon reduction elemental analyzer interfaced to an isotope ratio mass spectrometer. Because drought can potentially mask the isotope signal caused by hurricanes, measured ring widths will be compared with the actual oxygen isotope values. Years in which drought occurred will result in both narrow tree-ring widths and anomalously heavy oxygen isotope values for the earlywood portion of the tree ring.This project has the potential to develop a proxy record of hurricane activity that extends several centuries earlier than modern instrumental or historical documents by combining detailed dendrochronological and isotopic analysis. This longer proxy record will be useful to evaluate whether hurricane activity occurs in multi-decadal-scale cycles and, independently of these cycles, whether the longer record indicates an increase in hurricane activity during the latter 20th century. These results should contribute to a refined, long-term record of hurricane activity that may enhance statistical long-range future forecasts of hurricanes, and will help to determine if there are specific actions we can take to mitigate potential increases in hurricane frequency.

这项研究将调查来自乔治亚州南部，南卡罗来纳州南部的松树环和德克萨斯州的松树环中α同位素比的潜在用途，作为飓风活动的代理记录。树环α纤维素中的有机氧同位素主要反映源水的同位素组成。在浅根针叶树中，源水与降水直接相关。飓风产生的大量降水量比正常地表水明显低，并且这些低同位素比在地面和土壤水中可能持续数周。这些异常的轻度氧同位素组合物可能被纳入树环纤维素中，从而捕获了飓风活性的同位素记录。飓风在8月至10月期间最常影响美国东南部，几个月对应于单个树环的雷电部分。飓风活性可能导致LATEDWOOD D18O值（相对于国际接受标准，氧气与氧气与氧气与氧气的比率），并且在年度环中早期伍德和Latewood的同位素组合物的差异相对较大。在没有重大飓风活动的几年中，早期木材木材差异预计可以忽略不计。调查人员将首先将单个树环分开为早期木和Latewood的次年段，然后将树脂去除。 α纤维素的氧同位素组成将使用连接到同位素比率质谱仪的高温碳还原元素分析仪进行测量。由于干旱可能会掩盖由飓风引起的同位素信号，因此测量的环宽度将与实际的氧同位素值进行比较。干旱发生的几年将导致狭窄的树环宽度和树环的早期部分的异常沉重的氧同位素值。该项目有可能发展飓风活动的代理记录，该记录比现代工具早几个世纪或通过结合详细的树突年代学和同位素分析来结合历史文档。该较长的代理记录对于评估飓风活动是否发生在多年阶段的周期中，并且独立于这些周期，是否表明越长的记录表明飓风活动在后20世纪后期增加。这些结果应有助于飓风活动的长期长期记录，这可能会增强飓风的统计长期未来预测，并将有助于确定我们是否可以采取特定的行动来减轻飓风频率的潜在增加。