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, the knowledge of the subglacial topography and englacial layering is crucial. For this purpose, extensive ground-based ice radar surveys were done over Dome Fuji in the East Antarctic plateau during the 2017–2018 and 2018–2019 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 and thus attain a significant decrease in hyperbolic features 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, which sets substantial constraints for 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 sets of the data.
Highlights
Long climatic histories, from about 800 ka up to the present, have been studied using deep ice cores drilled at dome summits in the East Antarctic Ice Sheet (EAIS), such as Dome Fuji (Watanabe et al, 2003; Kawamura et al, 2017) and Dome C 15 (EPICA Community Members, 2004)
In the range of 35–55 km of Dome Fuji, where the hyperbolic effect was observed at the ice-bed interface, the ice thickness in JARE54 was thinner than that of JARE59 with a maximum and an average of 263 and 21 m, respectively
The high spatial resolution of the ice thickness data is attributed to the data interpolation smoothing effect being much smaller than that in previous data compilations, which is due to the Japanese Antarctic Research Expedition (JARE) radar data having a horizontal spacing that is equivalent to the grid size
Summary
From about 800 ka up to the present, have been studied using deep ice cores drilled at dome summits in the East Antarctic Ice Sheet (EAIS), such as Dome Fuji (Watanabe et al, 2003; Kawamura et al, 2017) and Dome C 15 (EPICA Community Members, 2004). Analyses of JARE data identified subglacial mountains with a thickness of 2000–2400 m centred at approximately 55 km south of Dome Fuji. These ice thickness data were used in the compilation of the Antarctic ice sheet thickness for BEDMAP (Lythe et al, 2001), Bedmap (Fretwell et al, 2013), AWI gridded data (Karlsson et al, 2018), and BedMachine Antarctica v1 (Morlighem et al, 2020). From the observing 25 features of radio echoes from the ice-bed interfaces, it is estimated to be frozen over the mountains with ice thickness less than ∼2500 m (Fujita et al, 2012)
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