Modelling the Hydrology of the Greenland Ice Sheet

• Main Author: Banwell, Alison
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: St Catharine's College 2017
• Subjects: Greenland ice sheet; glacier hydrology; modelling; glaciology; Greenland; glacier; Ice Sheet
• Online Access: https://doi.org/10.17863/CAM.13645; https://www.repository.cam.ac.uk/handle/1810/267715

There is increasing recognition that the hydrology of the Greenland Ice Sheet plays an important role in the dynamics and therefore mass balance of the ice sheet. Understanding the hydrology of the ice sheet and being able to predict its future behaviour is therefore a key aspect of glaciological research. To date, the ice sheet’s hydrology has tended to be inferred from the analysis of surface velocity measurements, or modelled in a theoretical, idealised way. This study focuses on the development of a high spatial (100 m) and temporal (1 hour) resolution, physically based, time-dependent hydrological model which is applied to the ~2,300 km2 Paakitsoq region, West Greenland, and is driven, calibrated, and evaluated using measured data. The model consists of three components. First, net runoff is calculated across the ice sheet from a distributed, surface energy- balance melt model coupled to a subsurface model, which calculates changes in temperature, density and water content in the snow, firn and upper-ice layers, and hence refreezing. The model is calibrated by adjusting key parameter values to minimize the error between modelled output and surface height and albedo measurements from the three Greenland Climate Network (GC-Net) stations, JAR 1, JAR 2 and Swiss Camp. Model performance is evaluated in two ways by comparing: i) modelled snow and ice distribution with that derived from Landsat-7 ETM+ satellite imagery using Normalised Difference Snow Index (NDSI) classification and supervised image thresholding; and ii) modelled albedo with that retrieved from the Moderate- resolution Imaging Spectroradiometer (MODIS) sensor MOD10A1 product. Second, a surface routing / lake filling model takes the time-series of calculated net runoff over the ice sheet and calculates flow paths and water velocities over the snow / ice covered surface, routing the water into ‘open’ moulins or into topographic depressions which can fill to form supraglacial lakes. This model component is calibrated against field measurements of a ...