A Unified Blister and Subglacial Hydrology Framework for Supraglacial Lake Drainage Events

TL;DR

This paper addresses how elastic blisters formed by rapid supraglacial lake drainage influence subglacial hydrology and ice flow, a process poorly captured by existing cavity-channel models. It introduces a unified two-dimensional framework that directly couples blister evolution with a subglacial drainage system via a leakage term, allowing blister propagation on realistic topography and transient leakage into channels. The authors demonstrate seasonal differences, showing winter blisters propagate with limited leakage while summer drains rapidly through channels, and derive propagation-velocity scalings that depend on the effective viscosity $mu_eff$ and lake volume $V_l$, as well as leakage controlled by $kappa$. A regional test in western Greenland reproduces observed flood extents and surface uplift, highlighting the model’s potential to interpret subglacial floods and constrain microphysical parameters from observations. The framework provides a tool for linking surface signals to subglacial hydraulic pathways and could inform predictions of ice-sheet response to lake-driven hydrology.

Abstract

Subglacial blisters form due to the rapid drainage of supraglacial lakes into grounded ice sheets, and are characterised by elastic ice uplift and transient ice-velocity anomalies. Although blister occurrence is confirmed by observations, the dynamics of blisters and their impacts on ice flow remain poorly represented in current subglacial hydrology models, as typical cavity-channel system models cannot capture short-timescale blister formation, propagation, and relaxation. Here we present a unified, self-consistent modelling framework that directly couples blister evolution with the subglacial drainage system, extending existing subglacial hydrology models to account for transient responses to rapid lake drainage events. Numerical simulations, validated by field observations, reveal distinct seasonal behavior: during summer, lake drainage generates short-lived blisters that rapidly leak water into a pre-existing drainage system of efficient, channelised water pathways, whereas winter drainage results in persistent blisters that propagate and serve as the primary meltwater pathway at the ice-bed interface. The dynamics of blister propagation and leakage in our model are governed by effective viscosity and a characteristic leakage length scale, which reflects the connection between the blister and the surrounding hydrological network. This unified model offers a valuable tool for investigating blister dynamics and their interplay with subglacial hydrology, facilitating the interpretation of observed surface uplift and ice-velocity variations following supraglacial lake drainage events.

Figures (9)

• Figure 1: Unified model set-up and computational domain. (a) A schematic of the subglacial hydrology model including blister, cavity and channel components. (b) The computational domain for the reference cases.
• Figure 2: Full water fluxes and blister profiles for a wintertime lake-drainage event.(a) Pre-drainage water flux and positions of the moulin, lake, and hypothetical monitoring stations (S1-S3), marked with coloured dots or triangles. (b)-(d) Water flux magnitude (background colour and colorbar) and $0.01$-m contour (blue line) of the blister thickness at $t=0.0$ d, $t=1.0$ d and $t=10.0$ d. Black lines are contours of the hydraulic potential $\phi$. (e) Time series of the fluxes. The blue line is the lake-drainage input (moulin input is zero in this case). The green line is the net outflux from the right boundary. The orange line is the leakage from the blister to the drainage system. (f) Time series of the blister thickness at different locations along the centerline. The dashed-grey line is the ratio of the blister volume to the volume of the drained lake ($V_b/V_l$). The solid-grey line is the ratio of the distance from the lake position to the blister front, to the total distance from the lake to the downstream boundary. When the blister front reaches the downstream boundary, this ratio equals 1.
• Figure 3: Evolution of the subglacial drainage system and blister following a summertime lake drainage event. Figure convention is the same as Figure \ref{['fig:wintertime_drainage']}, except that the moulin influx, represented by the red line in (e), is non-zero, which leads to a subglacial channel along the centerline. The blister leaks into the drainage system more quickly.
• Figure 4: Propagation velocity of the blister front as a function of effective viscosity $\mu_{\text{eff}}$ and lake drainage volume $V_l$. (a) The propagation velocity $\bar{v}$ as a function of $\mu_{\text{eff}}$ for different lake drainage volumes $V_l$. The dashed line is the scaling in the bending-dominated regime ($\bar{v}\sim \mu_{\text{eff}}^{-1/11}$), while the dash-dotted line is the gravity-dominated regime ($\bar{v}\sim \mu_{\text{eff}}^{-1}$). Note these lines just represent the trend of the dependence, and the prefactors vary among different cases and are not included. (b) The propagation velocity $\bar{v}$ as a function of $V_l$ for different effective viscosities $\mu_{\text{eff}}$. The dashed line and the dash-dotted line are the scalings in the bending-dominated regime ($\bar{v}\sim V_l^{5/22}$) and the gravity-dominated regime ($\bar{v}\sim V_l^{5/4}$), respectively.
• Figure 5: Wintertime and summertime blister volume loss with different values of $\kappa$. (a) Time series of the normalised blister volume $V_b/V_{l}$ due to leakage for different values of $\kappa$ in the winter case (solid lines) and the summer case (dashed lines). (b) The magnitude of the time-averaged volume loss rate from $t=0$ to $t=30$ d as a function of $\kappa$ for the winter case (blue) and the summer case (red). The dashed line is a linear reference. Colours correspond to different values of $\kappa$ in (a).