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

水深小于100m的北极大陆架区域约占北冰洋总面积的30%。在整个第四纪，北冰洋大陆架经历了不同的气候和动态地质历史。在低海平面时期，许多海洋陆架区域没有被水覆盖，但暴露在年平均气温为-20摄氏度或更低的环境中。这些低温形成了显着的永久冻土，也为天然气水合物创造了有利的压力和温度条件。相反，间冰期海平面上升导致海洋海侵，导致近海永久冻土和相关天然气水合物的退化。多年冻土/水合物形成和退化之间的反复变化对北极陆架和斜坡地区的地质产生了重大影响，表现为沉积模式和沉积物类型的快速变化、侵蚀和再沉积、物质输送沉积、流体流动模式的变化和沉积物压实的变化。这些地质过程导致了重大但仍鲜为人知的地质灾害的发生，如滑坡、超压和气体释放。该提案的首要目标是调查(加拿大)波弗特海南部海侵和人为气候变化引起的永久冻土退化、天然气水合物分解和天然气运移。我们受邀参加即将于2019年进行的Araon探险，并提议获取新的地震数据，以促进我们对北极天然气水合物和近海永久冻土的了解，否则这些数据是无法获得的。韩国极地研究所(KOPRI)和加拿大地质调查局(GSC)已批准参加2019年的探险。这个独特的机会使我们能够回答关于近海永久冻土和北极天然气水合物的三个关键问题：(1)近海永久冻土，特别是朝向陆架边缘的横向和垂直范围和浓度是多少？(2)在深水和永久冻土相关环境下，近海波弗特地区的天然气水合物的范围和浓度是多少？(3)陆架和陆架断裂环境中的气体流速有多大，海底排放的甲烷能到达大气吗？该提案通过与国际合作伙伴的合作得到高度利用，并允许以相对较低的成本参加加拿大波弗特海的国际破冰船探险。我们打算使用GEOMAR提供的海底地震仪(OBS)仪器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获取整个地区的地震反射数据。将通过获取海底剖面仪数据和声学水柱数据以及一套其他船上测量(例如，海水性质、大气气体成分等)来补充这一点。

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.).