Abstract
Abstract. Variations in properties controlling ice flow (e.g., topography, accumulation rate, basal friction) are recorded by structures in glacial stratigraphy. When anomalies that disturb the stratigraphy are fixed in space, the structures they produce advect away from the source and can be used to trace flow pathways and reconstruct ice-flow patterns of the past. Here we provide an example of one of these persistent tracers: a prominent unconformity in the glacial layering that originates at Mt. Resnik, part of a subglacial volcanic complex near Kamb Ice Stream in central West Antarctica. The unconformity records a change in the regional thinning behavior seemingly coincident (∼3440±117 a) with stabilization of grounding-line retreat in the Ross Sea Embayment. We argue that this feature records both the flow and thinning history far upstream of the Ross Sea grounding line, indicating a limited influence of observed ice-stream stagnation cycles on large-scale ice-sheet routing over the last ∼ 5700 years.
Highlights
New constraints on paleo-ice-dynamics are increasingly important in glaciology
We focus on a persistent tracer in the catchment region of Kamb Ice Stream, West Antarctica (Fig. 1a) – a stratigraphic unconformity forming in response to Mt
For an unconformity to appear in radar imagery, surface processes must modify the depth–conductivity profile – snow from one regime must sit on top of snow from another regime
Summary
New constraints on paleo-ice-dynamics are increasingly important in glaciology. They form the basis for validating model hindcasts, which act as a test of model performance, add to our understanding of past ice-sheet and climate interactions, and improve the reliability of future ice-sheet projections (Pollard et al, 2015). Nization in the Ross Sea sector in the past (Conway et al, 2002; Jacobel et al, 1996; Siegert et al, 2004), but interpreting them can be challenging With uncertainty in both their formation mechanism and subsequent evolution, many of the englacial structures observed in Antarctica and Greenland do not provide sufficient information to infer paleo-velocities. Like other persistent tracers seen elsewhere in Antarctica (Ross et al, 2011; Woodward and King, 2009), these data provide multi-millennial context for the ice-flow reorganization observed during the satellite era We highlight this feature as one example of a larger class of structures that should be targeted in future radar studies of the Siple Coast ice streams
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