Arctic hydrate dissociation as a consequence of climate change: determining the vulnerable methane reservoir and gas escape mechanisms

气候变化导致的北极水合物分解：确定脆弱的甲烷储层和气体逃逸机制

• 批准号: NE/H022732/1
• 负责人: Timothy Minshull
• 金额: $ 42.67万
• 依托单位: University of Southampton
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2011
• 资助国家: 英国
• 起止时间: 2011 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FH022732%2F1
• 关键词: Arctic; hydrate; dissociation; consequence; climate

Along the western margin of Spitsbergen, where the northern extension of Gulf Stream system conveys warm Atlantic water into the Arctic Ocean, hundreds of plumes of bubbles of methane gas were discovered in 2008, rising from the seabed at a depth close to that of the landward limit of the methane hydrate stability zone. Methane hydrate is a solid with the appearance of ice, in which water forms a cage-like structure enclosing molecules of methane. Methane hydrate is stable under conditions of low temperature and high pressure such as those found in regions of permafrost or under the ocean in water deeper than 300-600 metres, depending on the water temperature. Over the past thirty years, the ocean's temperature at the seabed has increased by 1 degree C, causing the zone in which hydrate is stable to contract down the continental slope, with the apparent consequence that hydrate has broken down and released methane, which has migrated to the seabed and into the ocean. At present, the rate of release of methane is generally too slow to overcome dissolution and oxidation in the ocean to reach the atmosphere, except in very small quantities. However, catastrophic gas venting, which is known to occur elsewhere, could release large amounts of methane over a short period of time. The strength of such venting depends upon the how much gas is stored locally beneath the seabed and the kinds of pathways that bring gas to the seabed. The proposed research seeks to define these pathways and to quantify the amount of gas. A marine research expedition will use a deep-towed, very high-resolution seismic system to image the small-scale structures that convey gas to the seabed and to detect the presence of gas in the sediments beneath the seabed. This will be done in conjunction with an electromagnetic exploration system that uses a deep-towed transmitter and receivers on the seabed to derive the variations in electrical resistivity in the sediments beneath the seabed. Higher-than-normal resistivity is caused by both gas and hydrate, whereas the presence of gas reduces seismic velocity and hydrate increases it. In combination, the two techniques can distinguish the separate amounts of hydrate and gas. The deep-towed seismic system, SYSIF, which uses a piezo-electric chirp source that gives very-high-resolution images and deeper sub-seabed penetration than similar systems mounted on a ship's hull, will be supplemented by the use of ocean-bottom seismometers to provide precise measurements of the variation of seismic velocity with depth, and seismic profiles with small airgun (mini-GI gun) to provide deeper high-resolution seismic imaging. Multibeam sonar will be used to improve definition of the shape of the seabed and high-frequency, fish-finding sonar will image plumes of gas bubbles and define their positions, providing, in many cases, comparisons with the images obtained in 2008 when they were first discovered. Two areas will be investigated, the region of the landward limit of the methane hydrate stability zone, where many bubble plumes occur in water shallower than 400 metres, and, for comparison, a pockmark in the Vestnesa Ridge, at a depth 1200 metres, from which gas is escaping and is underlain by 'chimneys' that convey gas to the seabed through the hydrate stability zone, where the gas would normally form hydrate. Geological and geophysical data, including 96-channel seismic reflection profiles, acquired in both areas during a research cruise in 2008, will complement the new data. The project will provide the sub-seabed context for a seabed observatory (MASOX Monitoring Arctic Seafloor - Ocean Exchange), which will be established in the shallow plume area in summer 2010 by a European scientific consortium to monitor the activity of the plumes and the physical and chemical fluxes through the seabed.

沿Spitsbergen的西部边缘，海湾流系统的北部延伸将温暖的大西洋水传达到北极海中，2008年发现了数百种甲烷气体气泡的羽毛，从海底上升，接近甲烷水合物稳定性地面的陆地限制。甲烷水合物是一种固体，具有冰的外观，其中水形成笼子的笼子结构，封闭了甲烷的分子。在低温和高压条件下，甲烷水合物在多年冻土区域或水下在水中发现的水中稳定，取决于水温，水中的水深于300-600米。在过去的三十年中，海底的海洋温度升高了1度C，导致水合物稳定以降低大陆斜率的区域，显然水合已经破裂并释放了甲烷，该甲烷已迁移到海底并进入海洋。目前，甲烷的释放速率通常太慢，无法克服海洋中的溶解和氧化，以至于到达大气中，除了很少的数量。但是，已知发生在其他地方的灾难性气体排气可能会在短时间内释放大量甲烷。这种通风的强度取决于在海床下方存储多少天然气以及将气体带入海床的道路的种类。拟议的研究试图定义这些途径并量化气体量。海洋研究探险队将使用深层，非常高分辨率的地震系统来对海床传达气体的小规模结构，并检测海床下沉积物中的气体存在。这将与电磁勘探系统一起完成，该系统使用海床上使用深t的发射器和接收器来得出海床下沉积物中电阻率的变化。高于正常的电阻率是由气体和水合物引起的，而气体的存在降低了地震速度，水合会增加。结合使用，这两种技术可以区分单独的水合物和气体。 The deep-towed seismic system, SYSIF, which uses a piezo-electric chirp source that gives very-high-resolution images and deeper sub-seabed penetration than similar systems mounted on a ship's hull, will be supplemented by the use of ocean-bottom seismometers to provide precise measurements of the variation of seismic velocity with depth, and seismic profiles with small airgun (mini-GI gun) to provide更深的高分辨率地震成像。多束声纳将用于改善海底和高频形状的定义，发现鱼泡的声纳将图像气泡的羽毛并定义其位置，并在许多情况下与2008年首次发现时在2008年获得的图像进行比较。将研究两个区域，即甲烷水合物稳定区域的陆上限制区域，那里有许多气泡羽流于400米的浅水中，并且为了比较，在Vestsea Ridge中的一个奇数，在1200米的深度下，气体是逃避的，并由“ Chimneys”逃脱，而“ Chimneys”的含量可以通过水合物来供应水氢，从而可以在水上综合的区域，从而可以在水上综合级别的综合区域。在2008年的研究巡航期间，在两个领域获得的地质和地球物理数据，包括96道通道地震反射曲线，将补充新数据。该项目将为海床天文台（Masox监测北极海底 - 海洋交换）提供次生环境，该项目将于2010年夏季由欧洲科学财团在浅羽流地区建立，以监测羽毛的活性以及通过海底通过海底的物理和化学磁通的活动。

项目成果

The response of methane hydrate beneath the seabed offshore Svalbard to ocean warming during the next three centuries

• DOI: 10.1002/grl.50985
• 发表时间: 2013-10-16
• 期刊: GEOPHYSICAL RESEARCH LETTERS
• 影响因子: 5.2
• 作者: Marin-Moreno, Hector;Minshull, Timothy A.;Sarkar, Sudipta
• 通讯作者: Sarkar, Sudipta

Estimates of future warming-induced methane emissions from hydrate offshore west S valbard for a range of climate models

针对一系列气候模型对南瓦尔巴德西部近海水合物未来变暖引起的甲烷排放的估计

• DOI: 10.1002/2015gc005737
• 发表时间: 2015
• 期刊: Geochemistry, Geophysics, Geosystems
• 作者: Marín-Moreno H

The response of methane hydrate offshore Svalbard to ocean warming during the next three centuries

斯瓦尔巴群岛近海甲烷水合物对未来三个世纪海洋变暖的反应

• 发表时间: 2014
• 期刊: EGU General Assembly Conference Abstracts
• 作者: Marin-Moreno Hector

A joint electromagnetic and seismic study of an active pockmark within the hydrate stability field at the Vestnesa Ridge, West Svalbard margin

• DOI: 10.1002/2015jb012344
• 发表时间: 2015-10-01
• 期刊: JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
• 影响因子: 3.9
• 作者: Goswami, Bedanta K.;Weitemeyer, Karen A.;Ker, Stephan
• 通讯作者: Ker, Stephan

Resistivity image beneath an area of active methane seeps in the west Svalbard continental slope

• DOI: 10.1093/gji/ggw330
• 发表时间: 2016-11
• 期刊: Geophysical Journal International
• 影响因子: 2.8
• 作者: Bedanta K. Goswami;K. Weitemeyer;T. Minshull;M. Sinha;G. Westbrook;H. Marín‐Moreno