摘要：Previous studies using Fourier transformation (FT) methods to analyze subglacial roughness have shown promise for distinguishing between different types of subglacial landscape from raw subglacial elevation data. We derive a two-parameter FT roughness index {ξ, η}, where • is based on the FT of elevation (as previously considered in isolation), and η is based on both the FT of elevation and the FT of bed-slope profile. In this way, we take account of both vertical and horizontal irregularities in subglacial surfaces. We demonstrate the statistical veracity of using {ξ, η} to consider roughness in terms of obstacle amplitudes and spacing, and consider the use of {ξ, η} in studies of ice dynamics and subglacial geomorphological interpretation. We show that {ξ, η} can be linked to basal sliding rates on the metre scale, and can be used to differentiate further than single-parameter roughness indices between different classes of subglacial landscape, in particular between erosional and depositional settings.
