P2C2: Late Holocene Changes in the SPCZ from Algal Lipid D/H in Lakes Across Oceania

P2C2：大洋洲湖泊中藻类脂质 D/H 导致的全新世晚期 SPCZ 变化

• 批准号: 1502417
• 负责人: Julian Sachs
• 金额: $ 39.66万
• 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: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2018-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1502417&HistoricalAwards=false
• 关键词: P2C2; Late; Holocene; Changes; SPCZ

Non-Technical AbstractThe tropical water cycle influences the global climate. Over the last 30 years it has undergone remarkable changes. Rainfall has increased in the regions of the tropics that normally receive lots of rain, and decreased in the drier regions. This was accompanied by a poleward expansion of the tropics in both hemispheres that has led to an expansion of desert regions over continents. Although tropical rainfall is poorly represented in many climate models, simple physical arguments and a wide range of models suggest these trends are likely to continue under global warming scenarios. It is unknown at this point whether the current changes in tropical rainfall are outside the range of natural variations of the pre-industrial climate. This is because rainfall data over the vast tropical oceans, which is derived primarily from satellites, is limited to the last 35 years. Such a brief weather record is insufficient to establish whether the recent changes in rainfall are anomalous. By extending the record of rainfall in the tropical South Pacific from the current 35 years to 2000 years, this project will produce the data necessary to assess whether rainfall changes over the last 35 years are unusual, and if so, whether they can be attributed to the buildup of greenhouse gases in the atmosphere. They will also provide the data necessary to determine which climate models are able to accurately reproduce tropical rainfall patterns, and therefore which models are likely to provide the most reliable forecasts.Technical AbstractIn order to place recent changes in rainfall over the tropical South Pacific Ocean into a longer-term context, this project will produce quantitative reconstructions of rainfall throughout the South Pacific Convergence Zone (SPCZ) that span the last 2,000 years. The hydrogen isotope ratio (2H/1H, or D/H) of (3β,4α,5α,22E)-4,23- dimethylergost-22-en-3-ol, dinosterol, will be measured in sediment cores from 8 islands across the modern SPCZ region. Dinosterol is synthesized almost exclusively by certain genera of dinoflagellate microalgae. Owing to the inverse relationship between D/H ratios in rain and rainfall rates in the tropics, the so-called "amount effect," we find that D/H ratios of dinosterol (δDdino) in 21 surface sediments throughout the SPCZ region are highly correlated with rainfall rates according to the relationship δDdino=-16.6(±2.45)*P-180(±15.3) [R2=0.71, N=21], where P is the rainfall rate in mm/day. A Monte Carlo analysis of errors indicates that rainfall rate estimates with 0.3 mm/day uncertainty are possible using this technique. Sediment cores from the Solomon Islands, Vanuatu, Wallis & Futuna, and Fiji, representing 4 of the 5 study regions have already been collected. New cores from lakes in Samoa and American Samoa will be collected as part of this project. Initial results indicate a 2.6 mm/day increase in rainfall in the Solomon Islands, on the western side of the SPCZ, and a 1.1 mm/day decrease in Wallis and Futuna, on the eastern side of the SPCZ, during the transition from the Medieval Warm Period 1,000 years ago to the Little Ice Age 600 years ago.

非技术摘要热带水周期会影响全球气候。在过去的30年中，它发生了重大变化。热带地区通常接收大量降雨并在驾驶员地区增加的地区的降雨量增加了。这是由于两个半球的热带向极力扩展而实现的，这导致了沙漠地区在大陆上的扩张。尽管热带降雨在许多攀登模型中的代表性很差，但是简单的物理论点和广泛的模型表明，在全球变暖方案下，这些趋势可能会继续。目前尚不清楚热带降雨的当前变化是否超出了工业前气候的自然变化范围。这是因为在卫星上衍生出的主要热带海洋上的降雨数据仅限于过去35年。如此短暂的天气记录不足以确定最近降雨的变化是否异常。通过将热带南太平洋的降雨记录从目前的35年延长到2000年，该项目将产生所需的数据，以评估过去35年中降雨的变化是否不寻常，如果是的话，是否可以归因于大气中的温室气体的积累。他们还将提供必要的数据，以确定哪些攀岩模型能够准确地繁殖热带降雨模式，因此哪些模型可能会提供最可靠的森林。技术摘要依令将热带南太平洋降雨的最新变化置于一个长期的降雨中，该项目将在整个South Pacific Convertence contractifection（SPCC）中（SPCCCC）产生量的降雨量，该项目将产生终止的降雨。 （3＆＃946;，4＆＃945;，5＆＃945;，22e）的氢同位素比（2H/1H或D/H） - 22e）-4,23- Dimethylergost-22-en-3-Ol，Dinosterol，Dinosterol，将在8岛各个岛屿的泥沙核中测量。害土厂几乎完全由某些鞭毛藻微藻属合成。由于热带降雨与降雨量之间的D/H比之间的反比关系，所谓的“量效应”，我们发现，在整个SPCZ地区21个地表沉积物中，Dinosterol（＆＃948; ddino）的D/H比与降雨量高度相关，该降雨量是根据降雨量的，降雨量的， [r2 = 0.71，n = 21]，其中p是mm/天的降雨速率。蒙特卡洛分析误差表明，使用此技术，可能具有0.3 mm/天不确定性的降雨速率估计值。来自所罗门群岛，瓦努阿图，瓦利斯和富米纳和斐济的沉积物核心已经收集了5个研究区域中的4个。该项目的一部分将收集来自萨摩亚湖泊和美国萨摩亚湖泊的新核心。最初的结果表明，在SPCZ的西侧，所罗门群岛的降雨量增加了2.6毫米，在SPCZ东侧的Wallis和Futuna的降雨量增加了1.1毫米/天/天，在1000年前从Medeev Medeev Warm时期过渡到SPCZ的东侧。