17:15 〜 18:30
[MIS05-P03] Multibeam bathymetry off East Antarctica: 2010s Japanese observations
キーワード：マルチビーム海底地形、南大洋、東南極
The seafloor covers two-thirds of the solid-earth surface, but most parts have not been explored because of acoustic observation difficulty, especially in polar regions. Significant records of glacial erosion and sedimentation as well as tectonic activities are preserved in the seafloor. Recent developments of ocean and ice sheet numerical modeling need better topographical boundary conditions for precise and high-resolution calculations. Therefore, further observations of acoustic bathymetry are essentially required. Since 2009, multibeam swath bathymetric mapping lead by Japanese scientists has started in the Japanese Antarctic Research Expeditions (JAREs) and several campaign observations. Here, we present preliminary results of these surveys on multibeam bathymetry off East Antarctica to show geomorphological structures from continental margin to ocean basins.
Multibeam bathymetric data were acquired by a 20 kHz frequency SeaBeam3020 system (L3 Communications ELAC Nautik) installed on the Japanese icebreaker Shirase, R/V Hakuho-maru, and R/V Mirai during fifteen expeditions in 2008–2020; KH-07-4, KH-09-5, KH-10-7, KH-16-1, KH-19-1, KH-20-1, JARE 51, JARE 52, JARE 53, JARE 54, JARE 55, JARE 61, MR12-05 leg2, MR12-05 leg3, and MR19-04 Leg3. The Shirase multibeam data was mainly provided by Japan Coast Guard for the utilization of scientific purposes. The sound velocity was corrected by real-time data of the surface water velocity meter, and seawater observations of conductivity, temperature, and depth. The CARIS HIPS and SIPS software (Teledyne CARIS Inc., Ltd., Fredericton, Canada) was used for raw data processing. In the Lützow-holm bay, multibeam data were merged with the point echo sounding data using sea ice drill holes acquired during the JARE 9, 14, 15, 18, and 22 (see Hirano et al., 2020; Kusahara et al., in revision).
The obtained bathymetric map covers the continental shelf of Lützow-holm bay (off Shirase glacier), Prytz Bay (off Amelie ice shelf), and off-Totten glacier. Observed landforms are likely associated with grounded ice flow, proglacial and subglacial erosion, and grounding line retreat. The continental slope was systematically investigated off Cape Darnley and off Lützow-holm bay, showing complex submarine channels. It is considered that asymmetric channel signatures are probably related to the spatial variation of sedimentation processes controlled by Antarctic slope current and bottom water. In the Gunnerus ridge, we newly identify volcanic edifices, which show 150-m topographic high and high amplitude of magnetic anomaly. Several series of depressional lineaments were observed in the south of the Southern Kerguelen plateau. Based on these results and descriptions, we would like to discuss the role of seafloor and interaction with ocean and ice sheet from the point of long-term geomorphological perspective.
Multibeam bathymetric data were acquired by a 20 kHz frequency SeaBeam3020 system (L3 Communications ELAC Nautik) installed on the Japanese icebreaker Shirase, R/V Hakuho-maru, and R/V Mirai during fifteen expeditions in 2008–2020; KH-07-4, KH-09-5, KH-10-7, KH-16-1, KH-19-1, KH-20-1, JARE 51, JARE 52, JARE 53, JARE 54, JARE 55, JARE 61, MR12-05 leg2, MR12-05 leg3, and MR19-04 Leg3. The Shirase multibeam data was mainly provided by Japan Coast Guard for the utilization of scientific purposes. The sound velocity was corrected by real-time data of the surface water velocity meter, and seawater observations of conductivity, temperature, and depth. The CARIS HIPS and SIPS software (Teledyne CARIS Inc., Ltd., Fredericton, Canada) was used for raw data processing. In the Lützow-holm bay, multibeam data were merged with the point echo sounding data using sea ice drill holes acquired during the JARE 9, 14, 15, 18, and 22 (see Hirano et al., 2020; Kusahara et al., in revision).
The obtained bathymetric map covers the continental shelf of Lützow-holm bay (off Shirase glacier), Prytz Bay (off Amelie ice shelf), and off-Totten glacier. Observed landforms are likely associated with grounded ice flow, proglacial and subglacial erosion, and grounding line retreat. The continental slope was systematically investigated off Cape Darnley and off Lützow-holm bay, showing complex submarine channels. It is considered that asymmetric channel signatures are probably related to the spatial variation of sedimentation processes controlled by Antarctic slope current and bottom water. In the Gunnerus ridge, we newly identify volcanic edifices, which show 150-m topographic high and high amplitude of magnetic anomaly. Several series of depressional lineaments were observed in the south of the Southern Kerguelen plateau. Based on these results and descriptions, we would like to discuss the role of seafloor and interaction with ocean and ice sheet from the point of long-term geomorphological perspective.