Large-scale Modelling of Subglacial Hydrology

Abstract

Subglacial hydrology is a key component in ice sheet dynamics and controls the sliding of ice sheets. Modelling the integrated system between ice dynamics and subglacial hydrology is essential for understanding current changes in the system and projecting future evolution of ice sheets and their contribution to sea level rise. The recent acceleration of mass loss of the Greenland ice sheet can be largely attributed to dynamic thinning at the ice margin, where hydrologic processes play a significant role in the speed-up of outlet glaciers. Models of subglacial hydrology recently have progressed to incorporate multiple components of the drainage system and are able to represent observed seasonal evolution of an efficient drainage system during the melt season, but the application of models on a continental scale remains a challenge. This doctoral thesis analyzes different approaches to model the subglacial hydrology and its interaction with the ice flow in respect to their ability to be applied to large domains. Two different models are developed and analyzed. A balance flux model coupled to the ice dynamics model SICOPOLIS is used to study the effect of subglacial water on the Eurasian ice sheet, applied to the simulation of future sea level contribution of Greenland where it reveals that the effect of subglacial discharge on submarine melting is comparable to increased ocean warming. Additionally, this model is utilized in the study of subglacial lakes at Recovery Glacier, Antarctica. The second model is an equivalent aquifer model which describes the water flow in a porous layer adapted to exhibit the properties of the complex drainage system. The evolution of the system is achieved by locally adjusting the transmissivity. It is shown that this approach leads to realistic pressure and discharge distributions which compare well with more sophisticated models, while keeping computational costs low.