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

ABSTRACTHarperOPP-0612506PffefferOPP-0612351HumphreyOPP-0612374Satellite的观测表明，格陵兰冰盖的表面融化程度逐年大幅增加。渗流相的积雪融化的面积和持续时间都在增加。渗流相是一种环绕冰盖的中等高程的宽阔地带。然而，由于对格陵兰岛渗流相的现场观测极其有限，融化水的命运尚不清楚。这些变化的最终水文结果是融水产生量和来自地理信息系统的径流的显著变化，然而，雪过程和径流之间的耦合很少有文献记载。特别是，径流界限，即季节性融化渗入、再冻结和不逃逸的高度，位于渗流相的较高部分，但其确切位置通常是未知的，径流界限对变暖的反应也知之甚少。目前和未来地理信息系统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。这项研究将量化融水径流过程和近地表降雪致密化的变化，并将产生一个新的高度改进的径流模型，该模型建立在实验观测的基础上。实验将在克劳福德角地区的一个横断面上进行，海拔从2025米延伸到1500米。具体目标有两个：1)首席调查人员将确定公里级的融水流动速度和路径，这将作为其径流模型的校准；以及2)。他们将调查跨越25年的记录中近地表致密化速度和过程的变化。这项工作将增加我们对流出冰盖的融水比例的理解和预测能力，记录发生在冰盖上的重要物理过程的变化，并提供罕见的地面观测，以与基于卫星的地表融化测量进行比较。其中每一项都对解释冰盖的表面高度、质量平衡和流动动力学以及最终的全球海平面有重要影响。主要研究人员是从事本科生和研究生教学以及研究生指导的活跃教师。他们将共同教授超过90学分的本科生和研究生课程。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、普通公众以及石油和天然气行业开展外联活动。

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.