The mechanical properties of the ice-bed interface govern the dynamic sensitivity of glaciers to changes in climate and oceanic forcing. Recent observations have underscored the importance of understanding the mechanics of glacier beds by showing that the Greenland and Antarctic ice sheets are losing ice mass at increasing rates due to accelerating ice flow. Many glaciers exhibiting significant acceleration are flowing rapidly due to slip at the ice-bed interface, but the relationship between the rate of slip and the drag force at the bed remains unclear. This knowledge gap inhibits our ability to make reliable projections of eustatic sea-level rise and has persisted because of a lack of observations. This talk will focus on how recent observations can be leveraged to develop a deeper understanding of the mechanical properties of glacier beds. I will begin by describing a new method for deriving time-dependent, three-dimensional surface velocity fields from remote sensing data, and then presenting first-of-their-kind results from a natural experiment in which the flow of a major ice stream (Rutford Ice Stream) in West Antarctica responds periodically to forcing from ocean tides. These data allow us to observe and quantify the rate of propagation and decay of stress perturbations. After discussing the data, I will present a physical model that relates the observed spatiotemporal variations in surface velocity to the mechanics of the bed. These results provide fresh insight into the mechanics of a prototypical Antarctic outlet glacier. I will conclude the talk by discussing how the approach may form a potential strategy for using the growing volume of time-dependent remote sensing data to help improve projections of future glacier states.