Monitoring Heat Transfer Across the Active Layer Above Permafrost in Alaska

大气中二氧化碳和其他气体浓度的上升预计将导致全球变暖。预计变暖的影响将被放大，并首先在高纬度地区被观察到。目前的模型预测，快速变暖将与北美西北部夏季降雨和冬季降雪量的增加相结合，这种情况可能导致阿拉斯加和加拿大西北部大部分地区的永久冻土迅速退化。类似的情况也可能在欧亚大陆北部持续存在。虽然永久冻土层与大气没有直接接触，但季节性积雪、地表植被和有机垫层是缓冲热量传递的活动层。能量通过对流和非对流过程（包括蒸发和凝结、冻结和融化、挥发和升华）穿过这一活动层，这些过程消耗或释放潜能。研究者在阿拉斯加被北方森林覆盖的不连续永久冻土区对土壤中的温度和水离子浓度进行了高频测量，结果表明，在某些情况下，非导电过程可以主导冻结和解冻土壤的热传递。该项目将在这两个不连续的永久冻土地区继续这一研究路线，并将其扩展到永久冻土连续的北极地区。数据将在两个不同的尺度上收集，并在三个地点对近地表过程进行高频监测。还将在同一地点的永久冻土上层进行测量，以便改进观测这一关键区域关键变量变化的方法。这一研究将从实质性和方法论的角度作出贡献。它将增加对永久冻土上方缓冲活动性层内非导电过程作用的一般认识，特别是当该层对温度和降水变化作出反应时。将这一研究方向扩展到永久冻土层的上层将增加对这一地区过程的了解，并将为可能在许多类似地区有用的新监测程序的可行性提供测试。＊＊＊

9308334 HINKEL Rising concentrations of carbon dioxide and other gases in the atmosphere are expected to cause global warming. The effects of warming are expected to be amplified and observable first in high latitudes. Current models predict that rapid warming will combine with increases in summer rainfall and winter snowfall in northwestern North America, conditions that may result in rapid degradation of permafrost throughout large parts of Alaska and northwestern Canada. Similar conditions may also persist in northern Eurasia. Although permafrost is not in direct contact with the atmosphere, seasonal snow cover, surface vegetation, and an organic mat serve as an active layer that buffers heat transfer. Energy passes through this active layer through convection and through non-convective processes (including evaporation and condensation, freezing and melting, and volatilization and sublimation), which consume or release latent energy. High-frequency measurements of temperature and water- ionic concentrations in soils conducted by the investigator in discontinuous permafrost regions covered by boreal forests in Alaska have indicated that the non-conductive processes can, under some circumstances, dominate heat transfers in freezing and thawing soils. This project will continue this line of research in both areas of discontinuous permafrost and expand it into Arctic areas where permafrost is continuous. Data will be collected at two different scales, with high-frequency monitoring of near-surface processes conducted at three sites. Measurements also will be taken in the upper levels of permafrost at the same sites in order to refine methods for observing changes in crucial variables in this critical zone. This research will make contributions from both substantive and methodological perspectives. It will add to general knowledge about the role of non-conductive processes within the buffering active layer above permafrost, especially as that la yer responds to changes in temperature and precipitation. Expansion of this line of research into the upper layers of permafrost will increase understandings of processes in this zone and will provide tests of the feasibility for new monitoring procedures that might have utility in many similar locales. ***