High-resolution subglacial topography around Dome Fuji, Antarctica, based on ground-based radar surveys over 30 years

Abstract

Abstract. The retrieval of continuous ice core records of more than 1 Myr is an important challenge in palaeo-climatology. For identifying suitable sites for drilling such ice, knowledge of the subglacial topography and englacial layering is crucial. For this purpose, extensive ground-based ice radar surveys were carried out over Dome Fuji in the East Antarctic plateau during the 2017/18 and 2018/19 austral summers by the Japanese Antarctic Research Expedition, on the basis of ground-based radar surveys conducted over the previous ∼ 30 years. High-gain Yagi antennae were used to improve the antenna beam directivity, thereby significantly decreasing hyperbolic features of unfocused along-track diffraction hyperbolae in the echoes from mountainous ice–bedrock interfaces. We combined the new ice thickness data with the previous ground-based data, recorded since the 1980s, to generate an accurate high-spatial-resolution (up to 0.5 km between survey lines) ice thickness map. This map revealed a complex landscape composed of networks of subglacial valleys and highlands. Based on the new map, we examined the roughness of the ice–bed interface, the bed surface slope, the driving stress of ice and the subglacial hydrological condition. These new products and analyses set substantial constraints on identifying possible locations for new drilling. In addition, our map was compared with a few bed maps compiled by earlier independent efforts based on airborne radar data to examine the difference in features between datasets. Our analysis suggests that widely available bed topography products should be validated with in situ observations where possible.

A one-dimensional temperature and age modeling study for selecting the drill site of the oldest ice core around Dome Fuji, Antarctica

“…A recent compilation of ice thickness data around DF indicates the presence of complex and steep terrain in the area, with uncertainty in bedrock elevation of > 60 m (Tsutaki et al, 2022), highlighting the necessity of a high spatial resolution survey of bedrock topography. The results from this study help to support the interpretation of observational data and the selection of a suitable drilling site.…”

“…The gray shading indicates the reflectivity, which is an indicator of contours representing ice of the same age. The bedrock elevation, shown by brown lines, was detected based on the maximum reflectivity from the base (Tsutaki et al, 2022). The bedrock elevation was calibrated to match the observed bedrock elevation at DF.…”

“…1). Later, the 54th JARE (2012-2013 Antarctic summer) conducted ground-based radar surveys in areas where subglacial mountains were detected in the south of DF (data compiled in Tsutaki et al, 2022). More recently, Alfred Wegener Institute (AWI) in Germany conducted airborne radar surveys covering the DF area (Karlsson et al, 2018).…”

Mapping age and basal conditions of ice in the Dome Fuji region, Antarctica, by combining radar internal layer stratigraphy and flow modeling

“…Our radar data was collected with an incoherent burst radar system, which means hyperbolic effects in signals are strong and affect the accuracy of subglacial topography. According to Tsutaki et al (2022), the average difference between ice thickness observed from Japanese radar system (with high-gain and high-directivity antennae) and the AWI RES system is −8 m, and the standard deviation is 108 m. The high standard deviation implies the details of bed topography observed by two radar systems could be significantly different, which may cause the misalignment in modeling results.…”

Temporal variations of surface mass balance over the last 5000 years around Dome Fuji, Dronning Maud Land, East Antarctica

“…The large-scale spatial pattern of the SMB depends on the surface elevation, continentality, and large-scale surface topography (e.g., positions of ice divides) in combination with a dominant trajectory of airmass with moisture. Around Dome Fuji, SMB is larger on the windward (mostly north-eastern) side of ice divides than on the leeward side (Suzuki et al, 2008;Fujita et al, 2011;Tsutaki et al, 2022). In addition, local variations in surface topography, which may be influenced by the bedrock topography and ice flow (Fujita et al 2011;Tsutaki et al, 2022), also affect the precipitation patterns and snow redistribution, thus the spatial patterns of SMB (Furukawa et al, 1996, Van Liefferinge et al, 2021.…”