Interpretation of Arctic North Slope Permafrost Borehole Thermal Evolution in Light of Spatial and Temporal Variation in Surface Temperature Fields

基于地表温度场时空变化的北极北坡多年冻土钻孔热演化解释

• 批准号: 1203945
• 负责人: Robert Anderson
• 金额: $ 9.14万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-15 至 2015-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1203945&HistoricalAwards=false
• 关键词: Interpretation; Arctic; North; Slope; Permafrost

Permafrost is ground that has remained below 0°C for more than two years. It has the greatest areal extent of any component of the cryosphere in the Northern Hemisphere. Feedbacks between permafrost, the hydrologic cycle, and the atmosphere are key components of the Arctic system. As the health of permafrost is directly dependent upon temperature, the thermal state of permafrost is one of the key signals of climate change. In addition, the thickness, distribution and temperature of permafrost influences both ecology and engineering in the Arctic. Between the atmosphere and the top of the permafrost is the active layer, which freezes and thaws on an annual basis. This active layer translates the climate signal at the Earth?s surface into heat flow into or out of the underlying conductive permafrost. The heat flux at the base of the active layer can be determined from profiles of temperature within the active layer, based on well-known physics of conduction. The goal in this project is to identify both spatial and temporal patterns of change in the permafrost of Alaska?s Arctic North Slope, and the critical processes that govern these patterns. Temperature profiles documented in the 1970s from abandoned exploratory boreholes suggested that the permafrost had warmed significantly to depths of many tens of meters, in a pattern that could be best explained by a 2-4°C surface warming over the prior half century. Since then, an array of 21 boreholes, spanning the National Petroleum Reserve-Alaska (NPR-A), has been repeatedly re-logged by USGS researchers, providing a record of dramatic change. The simplest interpretation of these profiles suggests yet more rapid increases in surface temperature, with a change of 3°C/decade occurring in the 1990s. The surface meteorology and active layer thermal structure has simultaneously been documented in an array of automated surface stations that span the region, and have been maintained for periods ranging from one to two decades. Nine of these surface stations are co-located with deep boreholes; all are embedded in international efforts to monitor the thermal state of the globe?s permafrost. The USGS network represents both the largest array of deep boreholes in the world used for monitoring the thermal state of the permafrost, and the densest array of surface stations in the global network.The investigators will integrate the observations of temperature profiles collected periodically from the deep boreholes, and 1-2 hourly observations of near surface meteorology and near surface soil temperature, to constrain the spatial and temporal record of the energy going into the permafrost. It will also extract the cleanest climate signal possible from the borehole measurements over the measurement interval (1970s onward) with the aim of answering questions about the thermal state of the landscape and the processes responsible for its evolution. To accomplish these goals the PI will first work with USGS colleagues to finalize quality control of their observations (preliminary data available at: http://data.usgs.gov/climateMonitoring/region/ show?region=alaska). He will then develop numerical models that predict the thermal disturbance from site-specific effects (e.g., length of time drilling, presence of lakes). Finally, using the ?cleanest? climate signal of warming and heat flow into the permafrost, the team will analyze the spatial and temporal pattern of this signal.Results will be available through both the scientific literature, and the Community Surface Dynamics Modeling System (CSDMS, http://csdms.colorado.edu/wiki/Main_Page) Educational repository. We will develop interactive models, animations, and classroom exercises based on this dataset, modeling effort, and final analysis.

永久冻土是指两年多以来一直保持在 0°C 以下的地面。它的面积是北半球冰冻圈所有组成部分中面积最大的。永久冻土、水文循环和大气之间的反馈是北极系统的关键组成部分。由于永久冻土的健康状况直接取决于温度，因此永久冻土的热状态是气候变化的关键信号之一。此外，永久冻土的厚度、分布和温度影响着北极的生态和工程。大气层和永久冻土层顶部之间是活跃层，每年都会冻结和融化。该活性层将地球表面的气候信号转化为流入或流出下面的传导性永久冻土层的热流。活性层底部的热通量可以根据众所周知的传导物理学从活性层内的温度分布确定。该项目的目标是确定阿拉斯加北极北坡永久冻土变化的空间和时间模式，以及控制这些模式的关键过程。 20 世纪 70 年代废弃勘探钻孔记录的温度剖面表明，永久冻土层已显着变暖，深度达数十米，这种模式可以用过去半个世纪地表变暖 2-4°C 来最好地解释。从那时起，美国地质勘探局的研究人员反复重新记录了阿拉斯加国家石油储备区 (NPR-A) 的 21 个钻孔，提供了巨大变化的记录。 对这些曲线的最简单解释表明，地表温度的上升速度更快，20 世纪 90 年代每十年变化 3°C。地表气象和活动层热结构已同时记录在跨越该地区的一系列自动化地面站中，并已维护一到二十年。其中九个地面站与深钻孔位于同一地点；所有这些都融入了监测全球永久冻土热状态的国际努力。 USGS 网络既代表了世界上用于监测永久冻土热状态的最大深钻孔阵列，也代表了全球网络中最密集的地面站阵列。研究人员将整合从深钻孔定期收集的温度剖面观测数据，以及每小时 1-2 小时的近地表气象和近地表土壤温度观测数据，以限制进入永久冻土层的能量的时空记录。 永久冻土。它还将从测量间隔（1970 年代起）的钻孔测量中提取尽可能最干净的气候信号，目的是回答有关景观热状态及其演化过程的问题。为了实现这些目标，PI 将首先与 USGS 同事合作，最终确定其观测结果的质量控制（初步数据可参见：http://data.usgs.gov/climateMonitoring/region/show?region=alaska）。然后，他将开发数值模型来预测特定地点影响（例如钻探时间长度、湖泊的存在）造成的热扰动。最后，使用“最干净的”变暖和热量流入永久冻土的气候信号，该团队将分析该信号的空间和时间模式。结果将通过科学文献和社区表面动力学建模系统（CSDMS，http://csdms.colorado.edu/wiki/Main_Page）教育存储库提供。我们将根据该数据集、建模工作和最终分析来开发交互式模型、动画和课堂练习。