Refinement of the fluidity parameter range with a stress exponent of four in Glen’s law: insights from Antarctic bed topography model
Abstract. Understanding the stress-dependent behaviour of the ice sheet is critical to projecting ice mass balance. Glen's law is used to calculate ice viscosity, conventionally with a stress exponent (n) equal to three. However, a stress exponent of four has recently been proposed for ice dynamics. The suggested range of the fluidity parameter (A) for n = 4 is of the order of six (i.e., 10-35 to 10-29 Pa-4 s-1), leading to a significant uncertainty in ice velocity than when n = 3. Here, we refined A to within one order, aligning with observed Antarctic ice velocities with simplified slope and Antarctic bed topography models. The Antarctic bed topography models, based on Antarctic BedMap2 data, specifically include the Ronne, Thwaites, and Ross Ice Shelves for West Antarctica, and the Amery, Shackleton Ice Shelves, and Mertz Glacial Tongue for East Antarctica. We found that the simplified model and the West and East Antarctic models share a common range of A values for matching observed Antarctic ice velocities. Refinement narrows the range of A to within one order for both the simplified and West/East Antarctic models. The narrowed range for A is from 4.0 × to 16.0 × Pa-4 s-1. Both models have common A values for representing Antarctic ice velocity, providing an insight into the applicable A values.
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