Basal anchoring for ice streams and mountain glaciers for various subglacial drainage environments

While humanity grapples with the political, behavioral and economic challenges of reducing greenhouse gas emissions, we risk reaching tipping points that could irreversibly damage our climate system. One of these tipping points is the disintegration of the West Antarctic Ice Sheet, much of which rests on ground below sea level. Some of the gigantic glaciers in West Antarctica, such as Thwaites, are losing ice at an unprecedented and accelerating rate, but others, such as Kamb, appear to hold steady. The reason is that Kamb lost a fraction of the water beneath it in the late 1800s, anchoring the glacier to the ground. It has been building up ice mass for the last hundred years. The goal of this poster is to evaluate whether it might be feasible to induce a Kamb-like change in the subglacial hydrological system in other places to anchor fast-moving glaciers or ice streams to the ground and thereby stabilize them. Ice streams differ from glaciers by having little topographic control. As a consequence, their lateral, heavily sheared margins are inherently dynamic and have a strong control over ice mass loss. If it was possible to trigger inward migration of these shear margins, both width and speed of the ice stream would decrease, potentially reducing ice mass loss significantly. Whether it is possible to induce inward shear-margin migration depends sensitively on the nature of the subglacial hydrological system. We compare the role of various subglacial hydrological systems, such as water films, R-channels, linked cavities and till canals, in modulating spatial variations in basal strength to understand where basal anchoring could lead either to a noticeable increase in basal strength or to inward margin migration. We analyze ice flow for a 2D vertical cross-sectional plane considering both a flat topography representative of an ice stream and a curved topography representative of a mountain glacier flowing through a valley. We implement a fully coupled thermomechanical model that incorporates non-Newtonian temperature-dependent ice rheology and Coulomb plastic till rheology. Our model determines the self-consistent shear margin location and ice surface velocity based on an integrated force balance. We find that canals carved into the till underlying the ice might be the most promising hydrological setting for basal anchoring. In contrast, we find that reducing the flow rate in R-channels has no significant influence on basal strength and ice mass flux. We also find that off-target intervention around any subglacial conduit and closer to the ice stream center may have a minor but statistically insignificant influence on reduction of ice stream surface velocity. We specifically focus on unknowns and observational constraints needed to evaluate the potential efficacy of an intervention for a given field site