Glacial erosion at the fjord onset zone and implications for the organization of ice flow on Baffin Island, Arctic Canada

Organized conduits of fast ice flow at the fringe of present and past ice sheets move the majority of ice from ice sheet interior to periphery. These relatively narrow corridors play a critical role in feedbacks between landscape evolution and ice sheet dynamics. Here we combine bedrock ¹⁰Be concentrations with distribution of lakes on Baffin Island, Arctic Canada, to constrain the pattern of glacial modification at a fjord onset zone - the region of increasing relief from the continental interior to the fjord head. High lake density and a lack of ¹⁰Be inheritance in the valley bottom indicate significant glacial scouring for some duration of the last glacial cycle. In contrast, ¹⁰Be inheritance and a lack of lakes at higher elevations indicate a lack of glacial scour and only slight glacial modification despite the entire region being covered by the Laurentide Ice Sheet during the last glaciation. This pattern of glacial erosion at the fjord onset zone is similar to what is found in the outer fjords ∼ 100 km toward the last glacial maximum ice margin, and indicates that ice flow becomes organized well inland from the fjorded coast. The relief-generating process of selective linear erosion occurs at the fjord onset zone and was responsible for evolving Baffin Island fjords even in the late Quaternary.