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Abstract Proglacial lakes along the retreating margin of the Laurentide ice sheet (LIS) significantly influenced the ice sheet's dynamics. This study investigates the interaction between proglacial lake drainage events and ice sheet evolution during deglaciation. Using a flowline ice sheet model, we demonstrate that abrupt lake drainage caused by the opening of spillways during the retreat of the ice sheet can temporarily reverse ice retreat and trigger rapid grounding line advance despite ongoing climate warming. We also show that ice shelf regrounding on a retrograde lake bed can follow lake drainage and further amplify ice sheet advance. These processes can decouple ice dynamics from climate forcing, offering a non‐climatic mechanism to explain the observed highly irregular ice margin fluctuations of the LIS. Our findings suggest that proglacial lakes might play an important role in modulating ice sheet evolution in warming climates. 

Abstract Glacial kettles are surficial depressions that form in formerly glaciated terrain when buried stagnant ice melts within pro‐glacial sediments, often deposited by meltwater streams. Kettles, like other glacial landforms, provide insight into the impact of climate on landscape evolution, such as the extent and timing of glaciations. The geometry of kettle features is variable, but existing theory does not explain the range of observed morphologies. Our study aims to establish a quantitative relationship between the depth of ice burial and the resulting morphology of terrain collapse in kettle depressions. To do so, we simulated kettle formation in the laboratory by burying ice spheres of four sizes in well‐sorted coarse sand at four different depths. As the spheres melt at room temperature, a glacial kettle analog forms at the surface. We scanned the resulting kettle topography with a portable LiDAR scanner to produce 3D digital elevation models of each depression, from which we measured each depression's depth and width and, in one instance, the time series of kettle formation. Using this data, we quantified the relationship between the sphere diameter, burial depth and resulting dimensions of the kettle by developing a set of equations, which we then applied to full‐scale features. Our results indicate that ice burial deeper than one sphere diameter corresponds to a decrease in depression depth and an increase in depression width. This application offers insight into the interdependence of ice burial depth and kettle geometry. 

Glacial landforms provide a valuable record from which to study the history and dynamics of past ice sheets. Eskers record paleo subglacial hydrologic and sediment transport conditions because they are composed of sediment deposited by water flowing through subglacial channels. Despite decades of study, there is still debate about their formation mechanisms and little investigation of the differences between eskers formed over soft and hard beds. To address this complexity, we analysed eskers formed over soft beds along the southern margin of the Laurentide Ice Sheet (LIS) in the Lake Superior region. This included developing a new method to calculate the basal effective pressure gradient during esker formation along the subglacial channel using grain size estimates from a 20 m tall esker exposure. The morphometry and distribution of eskers were mapped with GIS to quantify their sinuosity and lateral spacing, and to compare those to the underlying bedrock elevation and sediment thickness. Lateral spacing decreased over time as the ice margin retreated, suggesting that melt rates increased during the LIS deglaciation. Furthermore, the relation between esker distribution and sediment thickness showed that eskers formed preferentially over thinner layers of sediment, irrespective of whether erosion occurred before their formation. The sedimentology of the Cable Esker exhibits a non‐monotonic pattern in channel boundary shear stress ranging from 10 to 300 Pa, alongside a basal effective pressure gradient fluctuating between −9 to −70 Pa m⁻¹. Negative basal effective pressure gradients are consistent with esker formation in channels close to the glacier terminus, which suggests lower water pressure than normally assumed. This, combined with dynamic water level fluctuations within the esker channel, supports the theory of the formation of eskers near the ice margin. 

Investigations of the time-dependent behavior of marine ice sheets and their sensitivity to basal conditions require numerical models because existing theoretical analyses focus only on steady-state configurations primarily with a power-law basal shear stress. Numerical results indicate that the choice of the sliding law strongly affects ice-sheet dynamic behavior. Although observed or simulated grounding-line retreat is typically interpreted as an indication of marine ice sheet instability introduced by Weertman (1974), this (in)stability is a characteristic of the ice sheet's steady states – not time-variant behavior. To bridge the gap between theoretical and numerical results, we develop a framework to investigate grounding line dynamics with generalized basal and lateral stresses (i.e. the functional dependencies are not specified). Motivated by observations of internal variability of the Southern Ocean conditions we explore the grounding-line response to stochastic variability. We find that adding stochastic variability to submarine melt rates that produced stable steady-state configurations leads to intermittently advancing and retreating grounding lines. They can also retreat in an unstoppable manner on time-scales significantly longer than the stochastic correlation time-scales. These results suggest that at any given time of their evolution, the transient behavior of marine ice sheets cannot be described in terms of ‘stable’ or ‘unstable’.