Abstract
Abstract. By regulating the amount, the timing, and the location of meltwater supply to the glacier bed, supraglacial hydrology potentially exerts a major control on the evolution of the subglacial drainage system, which in turn modulates ice velocity. Yet the configuration of the supraglacial hydrological system has received only little attention in numerical models of subglacial hydrology so far. Here we apply the two-dimensional subglacial hydrology model GlaDS (Glacier Drainage System model) to a Svalbard glacier basin with the aim of investigating how the spatial distribution of meltwater recharge affects the characteristics of the basal drainage system. We design four experiments with various degrees of complexity in the way that meltwater is delivered to the subglacial drainage model. Our results show significant differences between experiments in the early summer transition from distributed to channelized drainage, with discrete recharge at moulins favouring channelization at higher elevations and driving overall lower water pressures. Otherwise, we find that water input configuration only poorly influences subglacial hydrology, which instead is controlled primarily by subglacial topography. All experiments fail to develop channels of sufficient efficiency to substantially reduce summertime water pressures, which we attribute to small surface gradients and short melt seasons. The findings of our study are potentially applicable to most Svalbard tidewater glaciers with similar topography and low meltwater recharge. The absence of efficient channelization implies that the dynamics of tidewater glaciers in the Svalbard archipelago may be sensitive to future long-term trends in meltwater supply.
Highlights
Land-based ice masses, as they undergo rapid change due to climate warming, are one of the largest potential contributors to global sea level rise (AMAP, 2017; Pörtner et al, 2019; Wouters et al, 2019)
Each glacier drainage system model run consisted of a 1year spin-up and a 14-year simulation period with one of the four water input configurations described in the previous section
The more localized recharge favours a faster evolution of subglacial channels, with an opposite effect that quickly dominates such that the moulin configurations result in overall lower water pressures during the remainder of the melt season and the subsequent winter
Summary
Land-based ice masses, as they undergo rapid change due to climate warming, are one of the largest potential contributors to global sea level rise (AMAP, 2017; Pörtner et al, 2019; Wouters et al, 2019). Regional glacier change affects surface albedo and coastal ecology, as well as hydrological management in terms of flood hazards, hydropower, and freshwater supply (Vincent et al, 2011; Fountain et al, 2012; Carey et al, 2017; Milner et al, 2017). As such, predicting and adapting to future alterations in the glacial landscape relies on better understanding glacier response to changing climate. Seasonal ice flow accelerations following periods of enhanced surface melt have been reported for glaciers worldwide On shorter timescales (i.e. hourly or daily), episodic speed-ups have been found to be concurrent with intense melting, heavy rainfall, and supraglacial lake drainage (e.g. Joughin et al, 2013; Horgan et al, 2015)
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