Abstract
Abstract. Meltwater channels form an integral part of the hydrological system of a glacier. Better understanding of how meltwater channels develop and evolve is required to fully comprehend supraglacial and englacial meltwater drainage. Incision of supraglacial stream channels and subsequent roof closure by ice deformation has been proposed in recent literature as a possible englacial conduit formation process. Field evidence for supraglacial stream incision has been found in Svalbard and Nepal. In Iceland, where volcanic activity provides meltwater with temperatures above 0 °C, rapid enlargement of supraglacial channels has been observed. Supraglacial channels provide meltwater through englacial passages to the subglacial hydrological systems of big ice sheets, which in turn affects ice sheet motion and their contribution to eustatic sea level change. By coupling, for the first time, a numerical ice dynamic model to a hydraulic model which includes heat transfer, we investigate the evolution of meltwater channels and their incision behaviour. We present results for different, constant meltwater fluxes, different channel slopes, different meltwater temperatures, different melt rate distributions in the channel as well as temporal variations in meltwater flux. The key parameters governing incision rate and depth are channel slope, meltwater temperature loss to the ice and meltwater flux. Channel width and geometry are controlled by melt rate distribution along the channel wall. Calculated Nusselt numbers suggest that turbulent mixing is the main heat transfer mechanism in the meltwater channels studied.
Highlights
Flow of water through glaciers has received considerable attention from the scientific community since theoretical treatment of the phenomena began with two publications in 1972 (Rothlisberger, 1972; Shreve, 1972)
In this paper we have presented a new model that for the first time provides explicit numerical simulation of meltwater channel evolution in glaciers, based on the combination of ice dynamics, open channel hydraulics, and ice-water thermal transfer
The model is capable of simulating channel incision over time for a given meltwater flux, meltwater temperature, channel slope, melt rate distribution in the channel, and initial ice geometry
Summary
Flow of water through glaciers has received considerable attention from the scientific community since theoretical treatment of the phenomena began with two publications in 1972 (Rothlisberger, 1972; Shreve, 1972). Simulating temporal and spatial evolution of meltwater channels in ice, which is key to understand the processes involved, requires adequate numerical models capable of resolving the underlying physics in great detail. New models of supraglacial channel evolution are required to quantify and further understand surface meltwater transport to the bed of large ice sheets. Schoof, 2010) they hold great promise for detailed modelling of the process chain from surface meltwater availability to eustatic sea level contribution of ice sheets. In this contribution we present a new model that for the first time provides explicit numerical simulation of supraglacial meltwater channels with a focus on their evolution as well as their incision behaviour.
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