Radar-Derived Internal Structure and Basal Roughness Characterization along a Traverse from Zhongshan Station to Dome A, East Antarctica

Abstract

The internal layers of ice sheets from ice-penetrating radar (IPR) investigation preserve critical information about the ice-flow field and englacial conditions. This paper presents a new detailed analysis of spatial distribution characteristics of internal layers and subglacial topography of the East Antarctic ice sheet (EAIS) from Zhongshan Station to Dome A. The radar data of 1244 km along a traverse between Zhongshan Station and Dome A of EAIS were collected during the 29th Chinese National Antarctic Research Expedition (CHINARE 29, 2012/2013). In this study, the Internal Layering Continuity Index (ILCI) and basal roughness were taken as indicators to provide an opportunity to evaluate the past internal environment and dynamics of the ice sheet. Except for the upstream of Lambert Glacier, the fold patterns of internal layers are basically similar to that of the bed topography. The relatively flat basal topography and the decrease of ILCI with increasing depth provide evidence for identifying previous rapid ice flow areas that are unavailable to satellites, especially in the upstream of Lambert Glacier. Continuous internal layers of Dome A, recording the spatial change of past ice accumulation and ice-flow history over 160 ka, almost extend to the bed, with high ILCI and high basal roughness of the corresponding bed topography. There are three kinds of basal roughness patterns along the traverse, that is, “low ξt low η”, “low ξt high η”, and “high ξt high η”, where ξt represents the amplitude of the undulations, and quantifies the vertical variation of the bedrock, and η measures the frequency variation of fluctuations and the horizontal irregularity of the profile. The characteristics of internal layers and basal topography of the traverse between Zhongshan Station and Dome A provide new information for understanding the ancient ice-flow activity and the historical evolution of EAIS.

British Antarctic Survey’s Aerogeophysical Data: Releasing 25 Years of Airborne Gravity, Magnetic, and Radar Datasets over Antarctica

“…By design, the ILCI is sensitive to the number and strength of internal reflections, such that low values indicate discontinuity and high values indicate high continuity. First tested over selected 2004-05 BBAS flightlines covering the Pine Island Glacier (Karlsson et al, 2012), the ILCI was subsequently employed over Institute and Möller Ice Stream (Bingham et al, 2015;Winter et al, 2015) and East Antarctica (Karlsson et al, 2018;Luo et al, 2020). Using the ILCI previously calculated for the 2010-11 IMAFI radar data, Ashmore et al (2020) further demonstrated that the ILCI was statistically higher where manually picked internal layers could be traced, thus showing for the first time that this method has the potential to be applied at a larger scale with reliable results.…”

Quantifying Basal Roughness and Internal Layer Continuity Index of Ice Sheets by an Integrated Means with Radar Data and Deep Learning

“…Studies have shown that ILCI is very sensitive to the number and intensity of internal reflectors. In general, low values indicate discontinuity, and high values correspond to high continuity, which shows that ILCI has a good correlation with the historical change of ice flows [20,36,42]. In addition, the ILCI method can eliminate the potential subjectivity of layer continuity evaluation and greatly improve efficiency in processing large amounts of radar data.…”

“…Basal roughness can be obtained from the radar-derived subglacial topography of ice sheets [19,20], or by utilizing the electromagnetic scattering properties of bed echo waveforms [21,22]. In [19,23,24], a Fourier transform method was used to calculate the roughness parameter ξ, which reflects the vertical irregularity of the subglacial topography, and the parameter η, which reflects the horizontal variation in the subglacial topography.…”

“…The internal layer continuity index (ILCI) is a parameter for the quantitative assessment of radar-derived englacial reflectors [20,36]. Generally, radar data can be presented in two forms, namely, A-scope, which records a single pulse signal, and Z-scope, which consists of multiple adjacent traces [37].…”

“…In addition, the ILCI method can eliminate the potential subjectivity of layer continuity evaluation and greatly improve efficiency in processing large amounts of radar data. The ILCI method is currently widely used in the assessment of internal layer continuity for airborne and ground-based radar data in Antarctica [20,[42][43][44][45]; therefore, ILCI is more efficient and reliable where internal layers can be tracked and has the potential to be applied on a larger scale of ice sheets.…”