Toward A Process Understanding of the Methane Thermodynamics Associated with Permafrost Thaw at the Arctic Continental Shelves

北极永久冻土层在冻结的沉积物中储存了大约1.7万亿吨有机碳。这是大气中碳含量的两倍。如果只有一小部分融化，逸出的甲烷将成为世界上最大的温室气体来源之一，并将严重影响环境和气候。我们知道，在过去的2万年里，北极永久冻土中储存的有机碳有四分之一被不断上升的温暖海平面淹没。但是，当全球变暖导致海平面进一步上升时，剩余的永久冻土层及其有机碳库将会发生什么？当永冻层被淹没时，会有多少甲烷释放到海水和大气中？回答这些问题将有助于我们了解北极永久冻土的洪水和融化是否会导致海洋酸化和北极变暖加剧。然而，在北极收集数据是困难的。这意味着我们对北极碳循环的了解还不够多，无法回答这些问题。这个项目的目标是看看计算机模拟和数学是如何提供帮助的。该项目将让我们更清楚地了解永久冻土在被洪水淹没时，温度、土壤、化学物质和微生物是如何一起变化的，以及甲烷在水中冒泡时会发生什么。这将帮助我们弄清楚北极永久冻土在过去和未来的碳循环、海洋化学和气候变暖中所扮演的角色。此外，该项目将为本科生和研究生提供跨学科的教育经验，并举办专题研讨会，以增加攻读STEM学位和职业的学生的数量和多样性。它还将为未来的钻探探险提供指导，改进地球系统(气候)模型，并帮助政策制定者。该项目将调查北极大陆边缘的洪水如何促进甲烷进入海洋和大气的循环。北极永久冻土层是甲烷的重要天然储存库，甲烷是一种温室气体，在20年的时间框架内，甲烷的效力是二氧化碳的84倍。当海平面在最后一次冰川盛期之后开始急剧上升时，温暖的海水(高达10-15℃)淹没了北极，并提高了永久冻土的温度。这显著地退化了永久冻土，并导致北极大陆架上广泛的气体释放。然而，甲烷的来源、目前的速度和数量，以及未来的预测，都还没有建立模型，也没有得到很好的约束。该项目将汇编北极大陆架特有的热、水文、微生物和地球化学参数；研究小组将进行一套系统的一维数值模拟，以计算北极大陆架泛滥后甲烷释放的上下限；然后，一维结果将被放大，以预测海底微生物甲烷交换的三维概率图，并对美国波弗特海和拉普特夫海的大陆架进行未来预测。该项目将系统地了解北极永久冻土系统因气候变暖而产生的热、物理、化学和微生物相互作用的演化过程。通过了解这些过程，我们可以增进我们对北极永久冻土在碳循环、海洋化学以及过去和未来气候变暖中的作用的了解。该项目将为本科生和研究生提供跨学科培训经验，并为K-12外联方案开发以地球科学为重点的培训模块。它将支持一名女性科学家建立她的研究团队。此外，该项目将开发具体的可测试假设，以指导未来的钻探探险、地球系统建模和政策制定。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Arctic permafrost stores about 1,700 billion tons of organic carbon in frozen deposits. That’s twice as much carbon as what’s in the atmosphere. If just a fraction of that melts, the escaping methane would become one of the world’s largest sources of greenhouse gas and would severely impact the environment and climate. We know that over the last 20,000 years, a quarter of the stored organic carbon in Arctic permafrost has been flooded by the rising, warm seas. But what will happen to the remaining permafrost and its organic carbon stores when warming causes further sea level rise? How much methane will be released into the ocean water and the atmosphere when the permafrost is flooded? Answering these questions will help us understand whether the flooding and thawing of Arctic permafrost will lead to ocean acidification and stronger Arctic warming. However, collecting data in the Arctic is difficult. That means we don’t yet know enough about the Arctic carbon cycle to answer these questions. The goal of this project is to see how computer simulations and math can help. The project will give us a clearer picture of how the temperature, soil, chemistry and microbes of the permafrost change together when it’s flooded, and what happens to the methane as it bubbles through the water. That will help us figure out the role of Arctic permafrost in the carbon cycle, ocean chemistry and climate warming, both in the past and in the future. In addition, the project will provide interdisciplinary education experiences for undergraduate and graduate students and feature workshops to increase the number and diversity of students pursuing STEM degrees and careers. It will also give insights that will guide future drilling expeditions, improve Earth system (climate) models, and assist policy makers.This project will investigate how flooding of the Arctic continental margin contributes to the cycle of methane into the ocean and atmosphere. Arctic permafrost is a significant natural reservoir of methane, a greenhouse gas that’s 84 times more potent than carbon dioxide over a 20-year timeframe. When sea level began rising sharply after the Last Glacial Maximum, warmer sea water (as warm as 10-15℃) flooded the Arctic and raised the temperature of the permafrost. That significantly degraded the permafrost and caused widespread gas release along the Arctic continental shelves. However, the methane source, its current rate and magnitude, as well as future projections, have not yet been modeled and are not well constrained. This project will compile thermal, hydrological, microbial and geochemical parameters that are characteristic of the Arctic continental shelves; the research team will conduct a systematic set of one-dimensional numerical simulations to calculate the upper and lower limits of methane release following the flooding of the Arctic continental shelves; the one-dimensional results will then be scaled up to predict three-dimensional probabilistic maps of seabed microbial methane exchange, and create future projections for the U.S. Beaufort Sea and the Laptev Sea shelves. The project will develop a systematic understanding of the coupled thermal, physical, chemical and microbial evolution of the Arctic permafrost system in response to warming. By understanding these processes, we can advance our knowledge of the role of Arctic permafrost in the carbon cycle, ocean chemistry and past and future climate warming. The project will provide interdisciplinary training experiences for undergraduate and graduate students and develop an earth science-focused training module for a K-12 outreach program. It will support a female scientist to build her research team. In addition, the project will develop specific testable hypotheses that could guide future drilling expeditions, Earth system modeling, and policy making.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.