Supraglacial lake drainages are isolated events that deliver the largest observable fluxes of surface melt to the ice-sheet bed. This talk will present advances in the study of these lake drainages, through which we piece together an empirical understanding of glacier hydrology. We examine the ways in which lakes both respond to, and determine, the hydrologic and glaciologic conditions under which they exist. We begin with the process puzzle of what mechanisms drive the opening of fractures within the compressive regions where lakes form, allowing hydro-fracture-driven drainages to occur. Next, we follow drained lake water in time and space, using the natural experiments provided by the drainages to infer subglacial-drainage-system transmissivity and structure beneath kilometer-thick ice flowing at rates of tens to thousands of meters per year in Greenland. In widening our view to previous subglacial-flood events observed at other ice-sheet locations—as well as at alpine, valley, and tidewater glaciers—we observe surprising similarities across a wide range of ice thicknesses, flow speeds, and types of flood events. The similarities we observe are encouraging because they suggest that information on drainage-system structure and evolution gleaned from these episodic events can be used to understand the wider picture. Finally, we examine current challenges: how do we move from the observed mechanisms of individual lake drainages to an integrated understanding of the importance of hundreds of drainages for long-term ice-sheet response and ice-shelf collapse? Progress will require the combination of geodetic observations, hydrologic simulations, and geophysical models to deconvolve the differing mechanisms that result in clusters of drainages in the multiple settings in which lakes form.

How to cite: Stevens, L. A., Banwell, A. F., Behn, M. D., Chase, D. L., Das, S. B., Dell, R. L., Falconer, E., Joughin, I. R., Lai, C.-Y., Larochelle, S., Lu, G. J., McGuire, J. J., Nettles, M., Okal, M., Rines, J., and Willis, I. C.: Supraglacial Lake Drainage: from process puzzle to subglacial diagnostic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11275, https://doi.org/10.5194/egusphere-egu24-11275, 2024.

Detection, attribution and projection of glacier and ice-sheet change characterize much of our community’s work, motivated in part by the associated impacts ranging from local hazards to regional water supply to global sea-level rise. Toward improved attribution of glacier change on local to regional scales, I profile work aimed at discerning the internal versus external drivers of glacier behaviour through process-oriented studies. Using examples from northern Canada, combining observational and numerical approaches improves our understanding of fundamental processes that define the boundary conditions at the ice interface with bedrock, water and atmosphere. These studies have allowed us to revisit questions related to glacier surging, hydrology and ice-dammed lakes and the co-evolution of glacier geometry and thermal structure, with occasionally surprising and counter-intuitive results.

While the internal dynamics of glacier systems have the potential to confound the climate signal on societally relevant timescales, the direct effects of climate via surface mass balance remain as important as ever. Improved observational platforms, advances in modelling and the growing abundance and availability of remotely sensed data have amplified our capacity to study these systems, and more generously than ever reveal information archived by glacier processes. Using these tools, we are now beginning to disentangle the contributions of the geologic substrate, environmental setting, internal ice dynamics and climate forcing to observed glacier change in globally significant ice-rich parts of the world.

How to cite: Flowers, G.: Understanding glacier processes to decode the drivers of glacier change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6597, https://doi.org/10.5194/egusphere-egu24-6597, 2024.