Fluid resonance in elastic-walled englacial transport networks

Abstract

Englacial water transport is an integral part of the glacial hydrologic system, yet the geometry of englacial structures remains largely unknown. In this study, we explore the excitation of fluid resonance by small amplitude waves as a probe of englacial geometry. We model a hydraulic network consisting of one or more tabular cracks that intersect a cylindrical conduit, subject to oscillatory wave motion initiated at the water surface. Resulting resonant frequencies and quality factors are diagnostic of fluid properties and geometry of the englacial system. For a single crack–conduit system, the fundamental mode involves gravity-driven fluid sloshing between the conduit and the crack, at frequencies between 0.02 and 10 Hz for typical glacial parameters. Higher frequency modes include dispersive Krauklis waves generated within the crack and tube waves in the conduit. But we find that crack lengths are often well constrained by fundamental mode frequency and damping rate alone for settings that include alpine glaciers and ice sheets. Branching crack geometry and dip, ice thickness and source excitation function help define limits of crack detectability for this mode. In general, we suggest that identification of eigenmodes associated with wave motion in time series data may provide a pathway toward inferring englacial hydrologic structures.

Evolving magma temperature and volatile contents over the 2008–2018 summit eruption of Kīlauea Volcano

“…In this case, the drastic change in VLP periods over the early part of the eruption likely represents an evolving conduit geometry due to some combination of a widening upper conduit and a change in conduit length due to a changing dip angle and reservoir attachment depth. A shallow dike/sill above the main Halema'uma'u reservoir could have also impacted the resonance (54); this would potentially be consistent with some seismic inversions (21,33), but such additional source complexity is not needed according to other seismic and geodetic inversions (7,9,11).…”

Controls on Greenland moulin geometry and evolution from the Moulin Shape model

“…First, moulin cross-sectional area, and thus water storage capacity, can vary substantially over the course of a day or season (Figs. 6c and 9b), and features such as englacial crevasses and reservoirs may be present (e.g., McQuillan and Karlstrom, 2021). Second, in instances where moulins are reactivated over multiple melt seasons (Chu, 2014;Smith et al, 2017), there may be substantial deformation, as suggested by cable breakage in boreholes (Ryser et al, 2014;Wright et al, 2016).…”

Resonances of Fluid‐Filled Cracks With Complex Geometry and Application to Very Long Period (VLP) Seismic Signals at Mayotte Submarine Volcano

“…Crack waves (and their induced tube waves in wellbores) are used for diagnosing the fracture geometries in unconventional hydrocarbon reservoirs (Henry et al., 2002; Liang et al., 2017; Lipovsky & Dunham, 2015; Tary et al., 2014). The resonating or humming signals in glaciers have also been attributed to crack waves (Gräff et al., 2019; McQuillan & Karlstrom, 2021; Métaxian et al., 2003; Stuart et al., 2005). Natural cracks in the subsurface are complex in shape and usually form an inter‐connected network.…”