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

科学价值：未来全球变暖将不可避免地破坏天然气水合物矿床的稳定性。然而，目前尚不清楚任何甲烷释放的幅度和后果。解决对天然气水合物的担忧的困难是由于对天然气水合物如何应对变暖的不完全理解。一个关键因素是反应的时间尺度。甲烷的缓慢扩散损失主要是通过与硫酸盐的反应消耗的，并在沉积物中沉淀为CaCO 3，对气候影响不大。更迅速的反应可能会将甲烷直接释放到海洋和大气中，在那里它会扰乱气候和碳循环。区分这些可能性是研究的首要目标。 首席研究员将对北冰洋浅大陆架下的天然气水合物进行模拟研究。这些沉积物被认为是冰川时期的遗迹，当时较低的海平面使大陆架暴露在零度以下的温度下。自末次盛冰期以来，海平面上升，淹没了大陆架，使表面温度变化了+10至+15摄氏度。在过去的10 kyr里，底层沉积物中的天然气水合物一直在对这种变暖做出反应。变暖的持续时间和幅度为研究天然气水合物存款的反应提供了一个独特的自然实验。首席研究员将使用来自博福特海的温度和孔隙压力的测井观测结果来约束和测试天然气水合物形成和分解的机理模型。将使用观测和模型的比较来解决两个具体问题。天然气水合物对气候变暖的响应时间尺度是多少？水合物存款的哪一部分能够释放甲烷到海洋和大气中？研究的预期成果将是更好地了解控制水合物沉积物释放甲烷的基本物理过程。这项工作与北极未来的变暖特别相关，尽管所获得的知识应该可以转移到其他海洋地点。更广泛的影响：这项研究的一个重要成果，超出了该项目的直接目标，将是在预测未来大气中CO2和CH 4浓度时更可靠地考虑天然气水合物的能力。强调机械模型的动机是希望避免基于当今条件的特设假设。首席研究员将应用这里开发的模型来调查过去和未来的情况。对北冰洋以下天然气水合物的关注与未来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。北极地区也可能与过去古新世-始新世热极大期水合物释放甲烷有关。这项研究将支持对一名女研究生进行开发和使用定量物理模型方面的培训。将通过一个网站提供在这项研究期间汇编的电子数据库（包括钻井记录数据和陆架沉积物中有机碳浓度的测量数据）。主要研究者将向感兴趣的研究人员提供模型源代码