Beaufort offshore permafrost and gas hydrates – Climate change impact on Arctic transgressed continental shelves

波弗特近海永久冻土和天然气水合物 â 气候变化对北极海侵大陆架的影响

• 批准号: 425875279
• 负责人: Professor Dr. Sebastian Krastel
• 金额: --
• 依托单位: Arbeitsgruppe Marine Geophysik und Hydroakustik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/425875279?language=en
• 关键词: Beaufort; offshore; permafrost; gas; hydrates

Arctic continental shelf regions with water depths of less than 100 m comprise ~30% of the total area of the Arctic Ocean. Throughout the Quaternary, the Arctic shelf experienced a varied climatic and dynamic geologic history. During periods of low sea level many of these marine shelf areas were not covered with water but were exposed to mean annual air temperatures of -20ºC or less. These cold temperatures caused the formation of significant permafrost and also established favorable pressure and temperature conditions for gas hydrates. In contrast, sea level rise during interglacial periods resulted in marine transgression, yielding degradation of offshore permafrost and associated gas hydrates. The repeated changes between permafrost/hydrate formation and degradation have had substantial impacts on the geology of Arctic shelves and slope regions in form of fast-changing styles of sedimentation pattern and sediment types, erosion and re-deposition, mass-transport deposits, changes to fluid-flow patterns, and changes in sediment compaction. These geologic processes result in the occurrence of significant and still poorly understood geohazards such as land-slides, over-pressure and gas-release. The overarching objective of the proposal is to investigate permafrost degradation, gas hydrate dissociation, and gas migration from transgression and anthropogenic climate change along the southern Beaufort Sea (Canada). We have been invited to participate in the upcoming ARAON expedition in 2019 and propose to acquire new seismic data to advance our understanding of Arctic gas hydrate and offshore permafrost that are otherwise impossible to obtain. Participation in the 2019 expedition has been granted by the Korea Polar Research Institute (KOPRI) and Geological Survey of Canada (GSC). This unique opportunity allows us to answer three critical questions about offshore permafrost and Arctic gas hydrates: (1) What is the lateral and vertical extent and concentration of offshore permafrost, especially towards the shelf edge? (2) What is the extent and concentration of gas hydrates for the offshore Beaufort region in both, deep-water, and permafrost associated settings? (3) How large are gas flow rates in the shelf and shelf-break setting and can methane emitted at the seafloor reach the atmosphere? The proposal is highly leveraged through collaboration with international partners and allows participation at comparably low costs at an international icebreaker expedition to the Canadian Beaufort Sea. We intend using ocean bottom seismometers (OBS) instrumentation provided by GEOMAR to obtain high quality seismic refraction data as well as using the onboard provided multi-channel seismic equipment to acquire seismic reflection data across the region. This will be complemented by acquiring sub bottom profiler data as well as acoustic water column data, and a suite of other on board measurements (e.g. ocean water properties, atmospheric gas composition, etc.).

水深小于100米的北极大陆架区域约占北冰洋总面积的30%。在整个第四纪，北极大陆架经历了不同的气候和动力地质历史。在海平面低的时期，许多这些海洋大陆架地区没有被水覆盖，而是暴露在年平均气温为-20摄氏度或更低的环境中，这些寒冷的温度导致了大量永久冻土的形成，也为天然气水合物的形成创造了有利的压力和温度条件。相反，间冰期期间海平面上升导致海侵，造成近海永久冻土和相关天然气水合物的退化。永久冻土/水合物的形成和退化之间的反复变化对北极大陆架和斜坡地区的地质产生了重大影响，其表现形式是沉积模式和沉积物类型、侵蚀和再沉积、物质迁移沉积、流体流动模式的变化以及沉积物压实的变化等快速变化。这些地质过程导致发生重大的地质灾害，但人们对这些灾害的认识仍然很差，如滑坡、超压和气体释放。该提案的总体目标是调查永久冻土退化、天然气水合物分解以及沿着博福特海南部（加拿大）海侵和人为气候变化引起的天然气迁移。我们已受邀参加即将于2019年进行的ARAON考察，并提议获取新的地震数据，以增进我们对北极天然气水合物和海上永久冻土的了解，否则这些数据是不可能获得的。参加2019年的探险活动是由韩国极地研究所（KOPRI）和加拿大地质调查局（GSC）批准的。这一独特的机会使我们能够回答关于海上永久冻土和北极天然气水合物的三个关键问题：（1）海上永久冻土的横向和垂直范围和浓度是什么，特别是朝向大陆架边缘？(2)近海博福特地区在深水和永久冻土相关环境中的天然气水合物的范围和浓度是多少？(3)大陆架和大陆架断裂环境中的气体流速有多大，海底排放的甲烷能否到达大气层？通过与国际伙伴的合作，该提案得到了高度的利用，并允许以极低的费用参加前往加拿大博福特海的国际破冰船考察。我们打算使用GEOMAR提供的海底地震仪（OBS）仪器来获取高质量的地震折射数据，并使用船上提供的多通道地震设备来获取整个区域的地震反射数据。此外，还将获取海底浅剖面仪数据、声学水柱数据和一套其他船上测量数据（如海水特性、大气气体成分等）。