Sommers, Aleah听1听;听Rajaram, Harihar听2听;听Colgan, William听3
1听University of Colorado
2听University of Colorado at 麻豆官网, Department of Civil, Environmental, and Architectural Engineering
3听Geological Survey of Denmark and Greenland
As observations become more plentiful through remote sensing and numerical models become more sophisticated, a clear priority of the ice sheet modeling community is to compare model simulations with observations. Temperature and velocity conditions within the Greenland ice sheet and at the bed remain largely unknown with the exception of sparse borehole measurements, but much can be inferred from rigorous thermo-mechanically coupled modeling, and plausible velocity and temperature profiles can be generated for the Greenland ice sheet interior that can serve as upper boundary conditions for simulations on lower-elevation domains, such as the outer regions of the ice sheet where englacial and subglacial hydrology are important. Surface velocities on the Greenland ice sheet are well constrained, both from satellite imagery and field observations. We take advantage of the observed surface velocities at the PARCA stakes around the 2,000m elevation contour of the ice sheet as modeling targets that represent a broad range of flow characteristics in different regions. Prescribing ice geometry, we use a two-dimensional thermo-mechanically coupled model to calculate steady-state velocity and temperature profiles throughout the depth of the ice along flowlines from the main divide to the 2,000m elevation contour. Vertical velocity calculations are based on first principles of mass conservation, and the enthalpy-based temperature calculations also incorporate the effects of liquid water content in temperate ice through the flow law parameter. Using a relatively simple model gives us the freedom to explore multiple sensitivities. Of particular interest is the relative influence of geothermal flux, bed geometry, and enhancement factor for ice older than the Wisconsin-Holocene transition. Numerous insights from our simulations are presented for different regions, and results indicate that areas of temperate bed do exist in the high-elevation interior in certain sections of Greenland.