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

永久冻土是指两年多来一直保持在0摄氏度以下的地面。它的面积是北半球冰冻圈中面积最大的。永冻层、水文循环和大气之间的反馈是北极系统的关键组成部分。由于多年冻土的健康状况直接依赖于温度，因此多年冻土的热状态是气候变化的关键信号之一。此外，多年冻土的厚度、分布和温度对北极的生态和工程都有影响。在大气层和永久冻土顶部之间是活动层，它每年冻结和融化。这一活跃层将地球表面的气候信号转化为热流，流入或流出下面的导电永久冻土。根据众所周知的传导物理，可以根据有源层内的温度分布来确定有源层底部的热流密度。该项目的目标是确定阿拉斯加-S北极北坡永久冻土变化的空间和时间模式，以及支配这些模式的关键过程。20世纪70年代从废弃的探井记录的温度曲线表明，永久冻土已经显著升温到几十米深，这种模式可以用前半个世纪2-4摄氏度的表面升温来最好地解释。从那时起，跨越阿拉斯加国家石油储备(NPR-A)的21个钻孔阵列被美国地质调查局的研究人员反复重新记录，提供了戏剧性变化的记录。对这些剖面的最简单解释表明，表面温度的上升速度更快，1990年代的变化为3摄氏度/十年。地面气象和活动层热结构在该区域的一系列自动化地面站中同时记录，并已维持了十到二十年的时间。这些地面站中有九个与深井位于同一地点；所有这些都嵌入了监测全球热状态的国际努力中--S永久冻土。USGS网络既是世界上最大的用于监测多年冻土热状态的深孔阵列，也是全球网络中最密集的地面站阵列。调查人员将整合从深孔定期收集的温度剖面观测，以及每小时一到两次的近地表气象和近地表土壤温度观测，以限制进入永久冻土的能量的空间和时间记录。它还将从测量间隔(1970年代以后)的钻孔测量中提取尽可能清洁的气候信号，目的是回答有关地貌的热状态和导致其演变的过程的问题。为了实现这些目标，PI将首先与美国地质勘探局的同事合作，最终确定他们观测的质量控制(初步数据可在：http://data.usgs.gov/climateMonitoring/region/SHOW？REGION=ALASKA获得)。然后，他将开发数值模型，预测特定地点的影响(例如，钻探时间长短，湖泊的存在)造成的热干扰。最后，使用最干净的？随着气候变暖和热流进入冻土，研究小组将分析这一信号的时空模式。结果将通过科学文献和社区地表动力学模拟系统(CSDMS，http://csdms.colorado.edu/wiki/Main_Page)教育库)获得。我们将基于此数据集、建模工作和最终分析开发交互式模型、动画和课堂练习。

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.