Firn Properties and Processes at Shallow Coring Sites in Greenland

这项拟议的项目考察了影响空气中的热、蒸汽和化学物质结合到雪和极地降雪中的方式的物理过程。这些过程包括扩散和平流，通过雪和雪中的气流输送热量、蒸汽和化学物质。对这些过程的理解很重要，因为它们控制着颗粒生长、雪的变质作用以及大气中的化学物质融入雪和雪的速度，因此将影响对极地冰芯数据的解释。该项目的目标是确定这些转移过程在空间和时间上的大小和范围，并发展对雪和雪内现象的过程级理解和建模能力。方法是在格陵兰冰盖上获得浅层岩芯和气象数据的地点进行实地研究，以确定关键参数的空间和时间范围，以及模拟降雪内热量、质量和化学物质的传导和平流所需的边界条件。一个现有的多维数值模型正在扩展，以模拟这些过程，并作为目前和今后在化学物质的运输和分配方面的工作的基础。目前，对极地冰芯数据的解释认为，扩散控制着化学物质融入降雪的速度。拟议的项目将确定冷杉中特定地点的通风程度，并将为谷物生长、升华速率和化学物质运输的多维扩散和通风提供一个模型。

The proposed project examines physical processes that affect the manner in which heat, vapor, and chemical species in air are incorporated into snow and polar firn. The processes include diffusion and advection, the transport of heat, vapor, and chemical species by air flow within snow and firn. An understanding of these processes is important because they control grain growth, snow metamorphism, and the rate at which chemical species in the atmosphere become incorporated into the snow and firn, and thus will affect interpretation of polar ice core data. The objectives of the project are to define the magnitude and extent, both in space and time, of these transfer processes, and to develop a process-level understanding and modeling capability of the phenomena within the snow and firn. The approach is to conduct field studies at sites where shallow cores and meteorological data are being obtained on the Greenland Ice Sheet to determine the spatial and temporal extent fro key parameters, and boundary conditions needed to model the conduction and advection of heat, mass and chemical species within the firn. An existing multidimensional numerical model is being expanded to simulate the processes and serve as the basis for ongoing and future work in transport and distribution of chemical species. Currently interpretation of the polar ice core data assumes that diffusion controls the rate at which chemical species are incorporated into the firn. The proposed project will determine the site-specific extent of ventilation in the firn, and will provide a model for multidimensional diffusion and ventilation on grain growth, sublimation rates, and chemical species transport.