Collaborative Research; A Field Validated Model for Melt-water Infiltration and Runoff from the Greenland Ice Street

卫星观测表明，格陵兰冰盖（GIS）的表面融化程度逐年大幅增加。在包围冰盖的中间高程宽带渗透相中，融雪的面积和持续时间都在增加。然而，融水的命运尚不清楚，因为格陵兰岛的渗透相的现场观测非常有限。这些变化的最终水文结果是地理信息系统产生的融水和径流的显著变化，然而，积雪过程和径流之间的耦合文献很少。特别是，径流极限，即季节性融水渗透、再冻结而不逃逸的高度，位于渗流相的较高部分，但其精确位置通常未知，径流极限对变暖的响应也知之甚少。目前和未来GIS对海平面上升贡献的模型使用了一个模型，该模型建立了“径流极限”对融化长期增加的响应的粗略界限。这项研究将量化熔融水径流过程和地理信息系统渗流相中近地表固体密度的变化，并将产生一个新的、高度改进的径流模型，该模型以实验观测为基础。实验将在克劳福德角地区沿样带的地点进行，从海拔约2025米延伸至1500米。具体目标有两个：1)主要研究人员将确定千米尺度的融水流动速度和路径，这将作为径流模型的校准；2)他们将调查近地表致密化率和过程的变化，记录跨度超过25年。这项工作将增加我们对从冰盖流出的融水比例的理解和预测能力，记录冰盖上发生的重要物理过程的变化，并提供罕见的地面观测数据，用于与基于卫星的地表融化测量进行比较。这些都对解释冰盖的表面高度、物质平衡和流动动力学以及最终的全球海平面上升具有重要意义。更广泛的影响：主要研究人员是从事本科和研究生教学以及研究生指导的活跃教学人员。他们将共同教授超过90个学分的本科和研究生课程。这项研究和相关的科学问题将为许多课程增加教学效益。这个项目将导致至少四个研究生学位。他们定期与k-12、公众以及石油和天然气行业开展外展活动。

ABSTRACTHarperOPP-0612506PffefferOPP-0612351HumphreyOPP-0612374Satellite observations suggest substantial year-to-year increases in surface melt extent of the Greenland Ice Sheet (GIS). Both the area and duration of snow melting in the percolation facies, a wide band of intermediate elevation that circumscribes the ice sheet, are increasing. The fate of the melt water, however, is unclear as in-situ observations in Greenland's percolation facies have been extremely limited. The ultimate hydrologic result of these changes is a significant change in meltwater production and runoff from GIS, however, the coupling between snow processes and runoff are poorly documented. In particular, the runoff limit, the altitude above which seasonal melt infiltrates, refreezes, and does not escape, lies within the higher part of the percolation facies, but its precise location is generally unknown, and the response of the runoff limit to warming is poorly understood. Current models for present and future contributions of GIS to sea level rise use a model which established rough bounds on the response of the "runoff limit" to secular increases in melt. This research will quantify melt water runoff processes and changes in near-surface firn densification in the percolation facies of GIS and will produce a new and highly improved model for runoff that is anchored in experimental observations. Experiments will be conducted at sites along a transect in the region of Crawford Point, extending from about 2025 m to 1500 m elevation. Specific objectives are twofold: 1) the Principal Investigators will determine km-scale melt water flow velocities and pathways which will serve as calibration for their runoff model; and 2). they will investigate change in near-surface densification rates and processes in records that span over 25 years. This work will increase our understanding and prediction capabilities of the fraction of meltwater which runs off the ice sheet, document change in important physical processes occurring on the ice sheet, and provide rare ground observations for comparison to satellite based measurements of surface melt. Each of these has important implications for interpretation of the ice sheet's surface elevation, mass balance, and flow dynamics and ultimately, global eustatic sea level.Broader Impacts: The Principal Investigators are active teaching faculty engaged in undergraduate and graduate teaching, and graduate student mentoring. They will collectively teach over 90 credit hours of undergraduate and graduate courses. This research and related scientific issues will add pedagogical benefit to numerous courses. This project will lead to at least four graduate degrees. They regularly conduct outreach activities with k-12, the general public, and the oil and gas industry.