Gas Hydrate Deposits below the Arctic Ocean: Response to Glacial Cycles and Global Warming

北冰洋下方的天然气水合物沉积物：对冰川循环和全球变暖的响应

• 批准号: 0713742
• 负责人: David Archer
• 金额: --
• 依托单位: University of Chicago
• 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: 2008-01-15 至 2010-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0713742&HistoricalAwards=false
• 关键词: Gas; Hydrate; Deposits; below; Arctic

ABSTRACTBuffettOPP-0713742Scientific Merit: Global warming will inevitably destabilize gas hydrate deposits in the future. However, the magnitude and consequence of any methane release is not presently known. The difficulty in addressing concerns about gas hydrate is due to an incomplete understanding of how gas hydrate responds to warming. A crucial factor is the time scale for the response. Slow, diffusive loss of methane is largely consumed by reactions with sulfate and precipitated as CaCO3 within the sediments, with little effect on climate. A more rapid response may release methane directly into the ocean and atmosphere, where it can perturb both climate and the carbon cycle. Distinguishing between these possibilities is an overarching goal of the research. The Principal Investigator will undertake a modeling study of gas hydrate below shallow continental shelves in the Arctic Ocean. These deposits are thought to be a relic of the glacial period when lower sea level exposed the shelves to sub-zero temperatures. Rising sea level since the last glacial maximum has inundated the continental shelves and brought a temperature change to the surface of +10o to +15 oC. Gas hydrates in the underlying sediments have been responding to this warming for the past 10 kyr. The duration and magnitude of the warming provides a unique natural experiment to investigate the response of a gas hydrate deposit. The Principal Investigator will use well-log observations of temperature and pore pressure from the Beaufort Sea to constrain and test mechanistic models for gas hydrate formation and dissociation. A comparison of observations and models will be used to address two specific questions. What is the time scale for gas hydrate to respond to warming? What fraction of the hydrate deposit is capable of releasing methane into the ocean and atmosphere? The expected outcome of the research will be an improved understanding of the basic physical processes that control the release of methane from hydrate deposits. The work is specifically relevant to future warming in the Arctic, although the knowledge gained should be transferable to other marine locations. Broader Impacts: An important result of this research that extends beyond the immediate goals of the project will be an ability to account more reliably for gas hydrate in predictions of future atmospheric concentrations of CO2 and CH4. The emphasis on mechanistic models is motivated by the desire to avoid ad hoc assumptions based on present-day conditions. The Principal Investigator will apply the models developed here to investigate conditions in the past and future.The focus on gas hydrate below the Arctic Ocean is particularly relevant for future predictions of global warming because the changes in the Arctic are expected to be most dramatic. The Arctic region may also be relevant for past release of methane from hydrates during the Paleocene-Eocene Thermal Maximum. The research will support the training of a female graduate student in the development and use of quantitative physical models. The electronic databases compiled during this study (including well-log data and measurements of organic carbon concentration in shelf sediments) will be made available through a web site. The Principal Investigator will provide model source codes to interested researchers

AbstractBuffettOPP-0713742SSCIENTIFIFIFIFIC：全球变暖将来将不可避免地破坏气体水合物沉积物。但是，目前尚不清楚任何甲烷释放的大小和后果。解决对气体水合物的担忧的困难是由于对气体水合物如何对变暖的反应不完全理解。一个关键因素是响应的时间尺度。甲烷的缓慢，扩散损失在很大程度上被硫酸盐的反应所消耗，并在沉积物中以CACO3的形式沉淀，对气候几乎没有影响。更快的反应可能会直接释放出海洋和大气，在那里它可以扰动气候和碳循环。区分这些可能性是研究的总体目标。 首席研究人员将对北极海洋浅陆货架以下的气体水合物进行建模研究。这些沉积物被认为是冰川时期的遗物，当较低的海平面暴露于零下温度下。自上次冰川最大值以来，海平面上升已淹没了大陆货架，并将温度变化 +10O至+15 oC。在过去的10 kyr中，基础沉积物中的气体水合一直在响应这种变暖。变暖的持续时间和大小提供了一个独特的自然实验，以研究气体水合物沉积物的响应。主要研究者将使用Beaufort Sea的温度和孔隙压力的井作观测，以限制和测试机械模型，以形成气体水合物和解离。观察和模型的比较将用于解决两个具体问题。气体水合响应变暖的时间尺度是多少？哪种水合矿床能够将甲烷释放到海洋和大气中？该研究的预期结果将是对控制从水合物沉积中释放甲烷的基本物理过程的改进理解。尽管所获得的知识应转移到其他海洋地点，但这项工作与未来在北极的变暖特别相关。更广泛的影响：这项研究的重要结果超出了项目的直接目标，将是能够在预测未来大气浓度的CO2和CH4的预测中更可靠地考虑气体水合物。对机械模型的重视是出于避免基于当今条件的临时假设的愿望。主要研究者将在此开发的模型应用于过去和将来的状况。北极海洋以下对气体水合的关注与未来对全球变暖的预测特别相关，因为北极的变化预计将是最引人注目的。北极区也可能与在古新世热最大值中从水合物中释放出甲烷有关。该研究将支持对女性研究生在开发和使用定量物理模型方面的培训。本研究中编译的电子数据库（包括货架沉积物中有机碳浓度的测量值）将通过网站提供。主要研究人员将向感兴趣的研究人员提供模型源代码