Spatial patterns of basal drag inferred using control methods from a full‐Stokes and simpler models for Pine Island Glacier, West Antarctica

TLDR

Basal drag is a fundamental control on ice stream dynamics that remains poorly understood or constrained by observations. The study aims to infer the spatial pattern of basal drag at Pine Island Glacier by applying control methods to surface velocities. This is achieved by using a full‑Stokes ice flow model and comparing the results with the MacAyeal shelfy stream and Blatter‑Pattyn simplified models. The full‑Stokes model shows little basal drag near the grounding line, whereas the simplified models overestimate basal drag due to neglecting bridging effects, confirming that a full‑Stokes treatment is essential near grounding lines.

Abstract

Basal drag is a fundamental control on ice stream dynamics that remains poorly understood or constrained by observations. Here, we apply control methods on ice surface velocities of Pine Island Glacier, West Antarctica to infer the spatial pattern of basal drag using a full‐Stokes (FS) model of ice flow and compare the results obtained with two commonly‐used simplified solutions: the MacAyeal shelfy stream model and the Blatter‐Pattyn model. Over most of the model domain, the three models yield similar patterns of basal drag, yet near the glacier grounding‐line, the simplified models yield high basal drag while FS yields almost no basal drag. The simplified models overestimate basal drag because they neglect bridging effects in an ice stream region of rapidly varying ice thickness. This result reinforces theoretical studies that a FS treatment of ice flow is essential near glacier grounding lines.