Investigating the Hydrology of the Western Greenland Ice Sheet: Spatiotemporal Variability and Implications on Ice-Dynamics

• Main Author: Mejia, Jessica Z.
• Format: Doctoral or Postdoctoral Thesis
• Language: unknown
• Published: Digital Commons @ University of South Florida 2021
• Subjects: Glaciology; Moulins; Subglacial; Lake drainage; Climate; Geology; Geophysics and Seismology; Avannarleq; Greenland; Sermeq Avannarleq; Ice Sheet
• Online Access: https://digitalcommons.usf.edu/etd/9598; https://digitalcommons.usf.edu/context/etd/article/10795/viewcontent/Mejia_usf_0206D_16715.pdf

Since the 1990's the Greenland Ice Sheet (GrIS) has been losing mass at an accelerating rate in response to climatic warming and is currently the largest terrestrial contributor to sea-level rise. While ice sheet models agree the GrIS will continue losing mass throughout the century, there are significant uncertainties associated with future sea-level rise contributions. Predicting the GrIS's response to future climate warming scenarios is limited by gaps in our understanding of the links between ice sheet hydrology and dynamics. Meltwater produced on the ice surface flows within supraglacial streams that deliver it to crevasses or moulins—vertical conduits extending from the ice surface to the ice sheet's bed. When the rate of meltwater delivery to moulins exceeds the hydraulic capacity of the moulin-connected subglacial drainage system, meltwater will temporarily backup within moulin shafts, increasing water pressures at the bed which can increase sliding speeds. Despite the central role of moulins in connecting supraglacial and subglacial hydraulic systems, little is known about their role in coupling hydrology and sliding on the GrIS. This dissertation uses several new data sets acquired within the ablation area of Sermeq Avannarleq in the western GrIS to further our understanding of the hydraulic systems that influence sliding within the GrIS ablation area. First, I investigate whether delays in the timing of meltwater delivery for more extensive, higher-elevation catchments could explain the previously progressively later timing of peak daily ice velocity observed with increased elevation and distance from the ice sheet's margin. We measured meltwater delivery to moulins, moulin water level, and the ice velocity response for two moulins at different elevations. Our results show that differences in the timing of meltwater delivery caused peak moulin water level to consistently occur later in the day at our higher-elevation moulin, lagging behind peak pressure at the lower elevation site by 1–3.25 hours. ...