| 项目编号: | 1502417
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| 项目名称: | P2C2: Late Holocene Changes in the SPCZ from Algal Lipid D/H in Lakes Across Oceania |
| 作者: | Julian Sachs
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| 承担单位: | University of Washington
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| 批准年: | 2014
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| 开始日期: | 2015-08-01
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| 结束日期: | 2018-07-31
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| 资助金额: | USD424268
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| 资助来源: | US-NSF
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| 项目类别: | Standard Grant
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| 国家: | US
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| 语种: | 英语
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| 特色学科分类: | Geosciences - Earth Sciences
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| 英文关键词: | year
; spcz
; rainfall
; d/h ratio
; recent change
; rainfall change
; spcz region
; current change
; modern spcz region
; rainfall rate
; remarkable change
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| 英文摘要: | Non-Technical Abstract
The 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 Abstract
In 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. |
| 资源类型: | 项目
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| 标识符: | http://119.78.100.158/handle/2HF3EXSE/93866
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| Appears in Collections: | 影响、适应和脆弱性
气候减缓与适应
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| Recommended Citation: | |
Julian Sachs. P2C2: Late Holocene Changes in the SPCZ from Algal Lipid D/H in Lakes Across Oceania. 2014-01-01.
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