Quantitative Salinity & Water D/H from Paired H & C Isotopes in Mangrove Lipids

定量盐度

• 批准号: 1348396
• 负责人: Julian Sachs
• 金额: $ 45万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-03-15 至 2017-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1348396&HistoricalAwards=false
• 关键词: Quantitative; Salinity; & Water; Paired

Global patterns of rainfall have been changing over the last half-century, impacting the lives of people worldwide. A full understanding of these changes has not yet emerged, but they have been linked to a warming of global temperatures in response to the buildup of greenhouse gases in the atmosphere. Among the more widespread changes in precipitation have occurred in the tropics, where wet regions have been getting wetter and dry regions drier. It remains unknown whether the changes in tropical rainfall observed over the last 30 years are unusual when viewed on a multi-century or multi-millennial time scale. As yet it is therefore not possible to say whether recent precipitation trends are outside the range of natural variability. Any such conclusion will require records of rainfall from the tropics extending back in time a thousand years or more. But at present there are few, if any methods to accurately reconstruct rainfall in most locations on the planet prior to the advent of rain gauges and satellites, especially in the maritime tropics. The goal of this project is to develop a method for determining the salinity and deuterium-to-hydrogen ratio of water, two parameters very closely linked to rainfall in the tropics, from the chemistry of mangrove lipids that can be recovered from ocean and lake sediment cores.Mangroves are remarkable trees that have adapted to living in saltwater. They inhabit the intertidal zones of the global tropics and subtropics. The approach of the proposed study is based upon the investigator's recent observation that the ratio of both deuterium (2H) to hydrogen (1H) and carbon-13 (13C) to carbon-12 (12C) in the lipids of mangrove leaves changes systematically when the salinity of the water in which they live changes. This study will calibrate that response in multiple species of mangroves by growing them in the laboratory at a range of different salinities. The investigator will then test whether those calibrations are consistent when applied to multiple mangrove species inhabiting the shorelines of saline lakes on the tropical island of Palau that span a wide range of salinities. Because the hydrogen isotope composition of mangrove lipids incorporates the deuterium-to-hydrogen ratio of the water in which the mangroves live, as well as the salinity of that water, and the carbon isotopes only respond to the salinity, it is possible to calculate both the salinity and the hydrogen isotope ratio of the coastal water. From these two parameters one can make good estimates of rainfall, since both the salinity and the deuterium-to-hydrogen ratio of coastal water decreases when rainfall increases. When measured on mangrove lipids extracted from sediment cores taken in coastal settings and maritime lakes it will be possible to reconstruct rainfall estimates back in time, thus providing the long-term view needed to conclude whether recent trends in tropical rainfall are outside the range of natural variability.This project is supported jointly by the Marine Geology and Geophysics Program in the NSF Division of Ocean Sciences.

在过去的半个世纪中，全球降雨模式一直在发生变化，影响了全球人的生活。对这些变化的全面了解尚未出现，但由于响应大气中的温室气体的积累，它们与全球温度的变暖有关。在热带地区，降水发生了更广泛的变化，那里的潮湿区域变得越来越干燥。在过去30年中观察到的热带降雨的变化是在多个世纪或多个千年时间尺度上观看的。因此，还不可能说最近的降水趋势是否超出了自然变异范围。任何此类结论都将需要临时延伸一千年或更长时间的热带降雨记录。但是目前，在雨量表和卫星出现之前，尤其是海上热带地区的大多数地方，几乎没有什么方法可以准确地重建地球上的大多数地点降雨。该项目的目的是开发一种方法来确定水的盐度和氘与氢比，这两个参数与热带地区的降雨密切相关，是从可以从海洋和湖泊沉积物岩心中回收的红树林脂质化学的方法。他们居住在全球热带和亚热带的潮间带中。拟议研究的方法是基于研究者最近的观察结果，即氘（2H）与氢（1H）和碳-13（13C）与碳-12（12C）在红树林脂质中的碳-12（12C）的比率在系统的盐度时会在系统上系统地变化。这项研究将通过在实验室中以各种不同的盐度种植在多种红树林中校准这种反应。然后，研究人员将测试这些校准是否适用于居住在帕拉（Palau）的盐湖海岸线的多种红树林物种中，这些校准物质遍及帕拉（Palau）的盐湖湖泊，这些矿石湖泊遍布广泛的盐分。因为红树林脂质的氢同位素组成结合了红树林所在的水的氘与氢比率，以及该水的盐度，碳同位素仅响应盐度，因此可以计算出盐度和沿海水的氢同位素比率。从这两个参数中可以很好地估计降雨，因为当降雨增加时，盐水和氘与氢的比率都会降低。 When measured on mangrove lipids extracted from sediment cores taken in coastal settings and maritime lakes it will be possible to reconstruct rainfall estimates back in time, thus providing the long-term view needed to conclude whether recent trends in tropical rainfall are outside the range of natural variability.This project is supported jointly by the Marine Geology and Geophysics Program in the NSF Division of Ocean Sciences.