Validation of the MBT paleotemperature proxy in lakes

湖泊中 MBT 古温度代理的验证

• 批准号: 0745658
• 负责人: Josef Werne
• 金额: $ 19.94万
• 依托单位: University of Minnesota Duluth
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-02-15 至 2011-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0745658&HistoricalAwards=false
• 关键词: Validation; MBT; paleotemperature; proxy; lakes

EAR-0745658WERNE, Josef P.Temperature is one of the most critical climate parameters to understand, yet remains difficult to reconstruct. Earth's surface temperature has a tremendous impact on other climate factors, such as hydrological variability. Furthermore, the recent trend of global warming illustrates our need to understand temperature, and its influence on climate change for future generations. A recent report by the IPCC stated that the Earth warmed by 0.6 degrees C during the 20th century, and is projected to warm by an additional ~2-6 degrees C during the 21st century. In addition, a recent NRC Committee has concluded that the recent warming observed in many records is real, but that there is less confidence in temperature reconstructions prior to A.D. 1600, and much less prior to A.D. 900. The primary reason for a lack of confidence in temperature reconstructions, according to the NRC committee, is the relative scarcity of precisely dated proxy evidence. They propose that the generation of additional temperature records would improve our confidence in global temperature reconstructions during the period from 2,000 years before present to today. Furthermore, the NRC committee indicates that efforts to improve the reliability of new temperature reconstructions through use of new developing proxies are also of great interest.Paleotemperature is difficult to measure in continental systems, particularly paleoarchives such as lake sediments. Recent work has highlighted the potential for new, microbial lipid based proxies for temperature to be applied in lake sediments. Bacterial-sourced branched GDGT lipids have been identified in soils, peats, and lake sediments and it appears that the degree of branching in these GDGTs is related to temperature, which can be quantified in the "MBT" index of Weijers et al. (2007). The goal of this proposal is to validate the use of the MBT paleotemperature proxy in lake sediments by (a) determining whether the branched GDGT distribution identified in lake sediments do indeed reflect watershed mean annual air temperature, and (b) to what extent other factors such as seasonal bias and sub-environments within a given watershed are influencing the apparent temperature signal preserved by these bacterial membrane lipids.I propose a series of analyses designed to test the validity of the MBT and CBT proxies as tools to reconstruct temperature and pH from lacustrine sediments, following an approach involving three different avenues of investigation. The combination of these three analytical approaches will target some of the major questions related to reconstructing temperature with the MBT index, including issues related to accuracy of the reconstruction, biases from seasonality and environmental variability, and coherence with the instrumental record. Specifically, the proposed study will be comprised of three major objectives. 1) Development of a global calibration of CBT and MBT between lake surface sediment and watershed mean annual air temperature (MAT). 2) Analysis of MBT in soils from different sub-environments from three selected sites over an annual cycle to identify environmental factors affecting MBT and potential seasonal biases. 3) Comparison of instrumental temperature data from three selected sites with MBT temperatures reconstructed from lake sediments over the past ~100 years. Broader impacts include training graduate and undergraduate students and disseminating information on this research to the public through displays at state parks. Broader impacts to the scientific community include a much-needed validation of the application of the MBT paleotemperature proxy in lacustrine systems. Increasing temperatures predicted by modern global climate change will significantly impact natural systems as well as human populations in the coming century. Gaining a better understanding of modern system processes and how they reflect modern climatic conditions can provide a useful tool for understanding past climate and modeling future trends. Appropriate application of rigorously investigated proxies such as the MBT provides the best information about paleotemperature estimates currently available on timescales beyond the existence if instrumental records, but the use of such proxies is only valid if we fully understand all of the caveats associated with them and apply them appropriately.

EAR-0745658WERNE，JOSEF P.Temperature是要理解的最关键的气候参数之一，但仍然很难重建。地球表面温度对其他气候因素（例如水文变异性）具有巨大影响。此外，全球变暖的最新趋势表明了我们了解温度的需求及其对子孙后代的气候变化的影响。 IPCC最近的一份报告指出，地球在20世纪在0.6摄氏度上升温，预计在21世纪将加热约2-6摄氏度。此外，最近的一个NRC委员会得出的结论是，在许多记录中观察到的最近的变暖是真实的，但是对公元1600年之前的温度重建的信心较小，而公元900年之前则少得多。根据NRC委员会缺乏信心，是NRC委员会缺乏信心的主要原因。他们建议，额外的温度记录的产生将使我们对全球温度重建的信心从现在的2，000年到今天。此外，NRC委员会表明，通过使用新的发展代理来提高新温度重建的可靠性的努力也引起了人们的极大兴趣。在大陆系统，尤其是诸如湖泊沉积物之类的古构造系统中，很难衡量Pleeotemperature。最近的工作强调了新的，基于微生物脂质的新型代理，以在湖泊沉积物中施用温度。在土壤，泥炭和湖泊沉积物中已经鉴定出细菌采购的分支GDGT脂质，看来这些GDGT中的分支程度与温度有关，可以在Weijers等人的“ MBT”指数中进行量化。 （2007）。该提案的目的是通过（a）确定在湖泊沉积物中确定的分支GDGT分布是否确实反映了在湖泊沉积物中的分布是否确实反映了流域的年度空气温度以及（b）在何种程度上，例如季节性的偏见和子元素在何种程度上影响了何种程度的因素，否则在何种程度上会影响给定的水平的温度，这是在湖泊沉积物中确定的何种程度，以验证在湖泊沉积物中使用MBT的使用MBT形成的GDGT分布是否确实反映了在何种程度上，通过（a）确定在何种程度提出了一系列分析，旨在测试MBT和CBT代理的有效性，作为涉及三种不同研究途径的方法，以重建湖泊沉积物的温度和pH值。这三种分析方法的结合将针对与MBT指数重建温度有关的一些主要问题，包括与重建准确性有关的问题，季节性和环境变异性的偏见以及与工具记录相一致的问题。具体而言，拟议的研究将由三个主要目标组成。 1）在湖面沉积物和流域平均年度气温（MAT）之间开发CBT和MBT的全球校准。 2）分析来自三个选择地点的不同子环境的土壤中的MBT，以确定影响MBT和潜在季节性偏见的环境因素。 3）比较从过去〜100年中从湖泊沉积物中重建的三个选定位点的工具温度数据。更广泛的影响包括培训毕业生和本科生，以及通过州立公园的展示向公众传播这项研究的信息。对科学界的更广泛的影响包括对MBT古温代理在湖间系统中的应用急需的验证。现代全球气候变化所预测的温度升高将显着影响自然系统以及未来世纪的人口。对现代系统过程以及它们如何反映现代气候条件有了更好的了解，可以为了解过去的气候和建模未来趋势提供有用的工具。适当应用经过严格研究的代理（例如MBT）提供了有关当前在存在的时间尺度上可用的古温估计的最佳信息，如果有工具记录，则只有在我们完全了解与它们相关的所有警告并适当地应用它们时，使用此类代理才有效。