A model for subglacial flooding through a preexisting hydrological network during the rapid drainage of supraglacial lakes

Abstract

Key Points:• Accounting for preexisting water causes subglacial flooding to be faster • Prior to flooding, water flow direction reverses, causing surface subsidence • The model is compatible with continuum subglacial hydrological models Abstract Increasingly large numbers of supraglacial lakes form and drain every summer on the Greenland Ice Sheet. Some of these lakes drain rapidly within the timescale of a few hours, and the vertical discharge of water during these events may find a preexisting film of water potentially within a distributed drainage system of linked cavities. Here we present a model for subglacial flooding applied specifically to such circumstances. One of many interesting results we find is that water flows in from the far field prior to the arrival of flooding. We systematically evaluate the effect of initial ice/bed opening on the degree of perturbation to the subglacial system. Of particular importance, we find that floods propagate much faster and vertical displacements are much greater for larger openings. For 10 and 1 cm of initial opening, for example, floods travel about 68% and 50% farther than in the fully coupled ice/bed scenario after 2 h of drainage, respectively. For the same choices of initial opening, the elastostatic displacement at the injection point is about 1.39 and 1.26 times that of the fully coupled scenario. Using the framework with a preexisting water film results in avoiding the pressure singularity that is inherent to classical hydrofracture models, thus opening an avenue for integrating the likes of our model within continuum subglacial hydrological models. Furthermore, we foresee that the theory presented can be used to potentially infer subglacial hydrological conditions from surface observables.

Time Scale for Rapid Draining of a Surficial Lake Into the Greenland Ice Sheet

“…It provided a remarkably clear record of the rapid disappearance of the lake's water into the ice. Our previous studies [2][3][4] supported quantitatively their [1] suggestion that the liquid had proceeded downward along a major crevasse system extending below the lake, through a process suggested by Weertman [5], and then propagated as a turbulently driven hydraulic fracture along the ice/rock interface at the base (see below).…”

“…A recent study addresses in another context how a pre-existing subglacial drainage system interacts with fluid penetration along it [18].…”

Seasonal Variability in Regional Ice Flow Due to Meltwater Injection Into the Shear Margins of Jakobshavn Isbræ

“…Commensurately, the acceleration of mass discharge, thinning, and terminus retreat has been documented for many of GrIS major marine-terminating outlet glaciers (Aschwanden, Fahnestock, & Truffer, 2016;Harig & Simons, 2016;Jin & Zou, 2015;Moon et al, 2015;Mouginot et al, 2015). Though the regional impact of active supraglacial hydrologic systems, driven by enhanced surface melt production and runoff, has been well documented (Adikari & Tsai, 2015;Alley et al, 2005;Boon & Sharp, 2003;Colgan et al, 2011;Das et al, 2008;Fountain et al, 2005;Ignéczi et al, 2016;Krawczynski et al, 2009;St. Germain & Moorman, 2016;Tsai & Rice, 2010;Van der Veen, 2007;Walder, 1986), direct meltwater injection into fast-flowing outlet glaciers has not been sufficiently studied.…”

“…Though the regional impact of active supraglacial hydrologic systems, driven by enhanced surface melt production and runoff, has been well documented (Adikari & Tsai, ; Alley et al, ; Boon & Sharp, ; Colgan et al, ; Das et al, ; Fountain et al, ; Ignéczi et al, ; Krawczynski et al, ; St. Germain & Moorman, ; Tsai & Rice, ; Van der Veen, ; Walder, ), direct meltwater injection into fast‐flowing outlet glaciers has not been sufficiently studied. There have been a few efforts focused on the impact of infiltrated surface meltwater on ice stream dynamics.…”

Mass transport waves amplified by intense Greenland melt and detected in solid Earth deformation

“…The bedrock GNSS stations have a unique ability to track the fulcrum of the mass anomaly and its motion and operate in remote locations with high-temporal resolutions. Apparently, both theory and observations suggest that a complex and inestimable chain of meltwater-related processes operating on hourly or longer timescales is involved for glacier thinning and speedup [e.g., Zwally et al, 2002;Das et al, 2008;Stearns et al, 2008;van de Wal et al, 2008;Schoof , 2010;Palmer et al, 2011;Sundal et al, 2011;Adhikari and Tsai, 2015;Stevens et al, 2015Stevens et al, , 2016.…”