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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. 

Abstract. The timing of the Laurentide Ice Sheet's final retreat from North America's Laurentian Great Lakes is relevant to understanding regional meltwater routing, changing proglacial lake levels, and lake-bottom stratigraphy following the Last Glacial Maximum. Recessional moraines on Isle Royale, the largest island in Lake Superior, have been mapped but not directly dated. Here, we use the mean of 10 new 10Be exposure ages of glacial erratics from two recessional moraines (10.1 ± 1.1 ka, one standard deviation; excluding one anomalously young sample) to constrain the timing of Isle Royale's final deglaciation. This 10Be age is consistent with existing minimum-limiting 14C ages of basal organic sediment from two inland lakes on Isle Royale, a sediment core in Lake Superior southwest of the island, and an estimated deglaciation age of the younger of two subaqueous moraines between Isle Royale and Michigan's Keweenaw Peninsula. Relationships between Isle Royale's landform ages and Lake Superior bottom stratigraphy allow us to delineate the retreat of the Laurentide ice margin across and through Lake Superior in the early Holocene. We suggest that Laurentide ice was in contact with the southern shorelines of Lake Superior later than previously thought. 

The dominant source of inter-model differences in comprehensive global climate models (GCMs) are cloud radiative effects on Earth's energy budget. Intermediate complexity models, while able to run more efficiently, often lack cloud feedbacks. Here, we describe and evaluate a method for applying GCM-derived shortwave and longwave cloud feedbacks from 4 × CO₂ and Last Glacial Maximum experiments to the University of Victoria Earth System Climate Model. The method generally captures the spread in top-of-the-atmosphere radiative feedbacks between the original GCMs, which impacts the magnitude and spatial distribution of surface temperature changes and climate sensitivity. These results suggest that the method is suitable to incorporate multi-model cloud feedback uncertainties in ensemble simulations with a single intermediate complexity model.