极地冰盖粒雪密实化过程的研究进展  

Research progress on firn densification models in polar ice sheets

作　　者：张雪玉 柳林[1,2] ZHANG Xueyu;LIU Lin(National Precise Gravity Measurement Facility(PGMF),Huazhong University of Science and Technology,Wuhan 430074,China;Institute of Geophysics,School of Physics,Huazhong University of Science and Technology,Wuhan 430074,China)

机构地区：[1]华中科技大学精密重力测量国家重大科技基础设施,湖北武汉430074 [2]华中科技大学物理学院地球物理研究所,湖北武汉430074

出　　处：《冰川冻土》2024年第3期819-831,共13页Journal of Glaciology and Geocryology

基　　金：国家自然科学基金项目(42274028,41704023)资助。

摘　　要：粒雪密实化过程在冰川物质平衡监测和冰芯古气候记录分析等冰川学研究中具有重要作用,近年来国内外学者在极地冰盖开展了大量工作并建立出一系列粒雪密实化模型。本文将典型的极地冰盖粒雪密实化模型分为经验模型(包括半经验模型)和物理模型两大类,综合分析和讨论了两类模型的建模机理、发展现状及不足之处。经验模型关注粒雪柱在密实化过程中的宏观演变,利用实测的粒雪深度-密度数据建立密实化速率方程。目前,该类模型主要研究了温度、积累率、融水渗透和再冻结过程对密实化速率的影响。物理模型聚焦于粒雪晶粒在密实化过程中的微观结构变化,利用晶界滑移、幂律蠕变和晶格扩散等物理机制解释晶粒的生长变形过程。目前,新雪-粒雪转化过程的研究主要基于晶界滑移理论,粒雪-冰川冰转化过程的研究主要基于球形粉末的压力烧结理论。总体而言,极地冰盖粒雪密实化过程的研究在过去几十年取得了长足的发展,但由于粒雪微观结构及其与宏观演变联系的认知匮乏,经验模型缺乏完善的湿粒雪密实化理论,且将稳态假设直接推广到瞬态情景存在一定问题;物理模型由于粒雪密实化的物理机制尚不明确,难以精确刻画粒雪演变的整个物理过程。Glaciers are transformed from snowflakes formed by the condensation of atmospheric water vapor at low temperatures.In general,the transformation of snowflakes to glaciers contains three processes.To begin with,the snowflakes falling on the surface of glaciers are automatically rounded and transformed into firn be-cause a system is more stable when its surface free energy is lower.The subsequent step is firn densification,a lengthy and challenging process that turns firn into glacier ice.During firn densification,firn density increases with depth and time due largely to overburden stress from the accumulation of new snow.Finally,glacier ice flows and progressively converts into glaciers under the force of gravity.Firn densification is a highly complicat-ed process since several physical mechanisms operate simultaneously during densification and dominant mecha-nisms differ at different stages.Understanding the evolution of density and the physics of firn densification is es-sential for several applications of glaciology.A firn densification model that can simulate the density evolution of firn is crucial for assessing glacier mass balance accurately via the satellite altimetry method.In this method,the differencing of digital elevation models provides a change in glacier volume,which needs to be converted to a mass change by a density model or assumption.The paleoclimate reconstruction of the ice core requires calcu-lating the age difference between the ice and the air trapped in it.A firn densification model is necessary to deter-mine the age of the ice when the bubbles are close-off,which can be coupled to a firn-air model to calculate the age difference.This paper comprehensively analyzes the research methodology and the latest progress on firn densification in polar ice sheets.Numerous firn densification models have been proposed in recent years.These models are categorized as either empirical models(including semi-empirical models)or physical models.Empir-ical models are often based upon a steady-state assumpt

关 键 词：格陵兰冰盖 南极冰盖 粒雪密实化 粒雪密度演变 

分 类 号：P941.6[天文地球—自然地理学] P343.6