Numerical model of meltwater retention and firn aquifer formation in Greenland Ice Sheet

Abstract:

Observations show increasing surface melt and mass loss from the Greenland ice sheet. However, at present considerable uncertainty remains in understanding and predicting, much of the meltwater produced is retained and how much reaches the ocean through surface runoff or by draining through moulins. The potential for the Greenland ice sheet to retain substantial amounts of water has been highlighted by the recent and surprising discovery of a semi-permanent firn aquifer. In this study, we use a numerical model to simulate surface melt and track the meltwater evolution in the snow and firn layer to explore how the firn aquifer forms and their influence on Greenland Ice Sheet mass balance and dynamics. The model is coupled with a surface energy balance model, which computes surface energy and mass balance processes, and a snow-firn model, which simulates snow and ice metamorphic processes and englacial water transport processes. Case studies were carried on the melting part of Greenland Ice Sheet to calibrate and validate the model, driven by in situ AWS stations observational data and ERA-interim downscaled reanalysis data. Model results are used to analyze the conditions on which firn aquifer forms and examine limitations associated with driving a model with coarse scale climate data. We also examine the sensitivity to model results to different parameterization of albedo, densification and water transport.