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Pleistocene glaciomarine laminated muds in the Central Basin of the northwestern Ross Sea and their palaeoceanographic records

Mon, 01 Jan 2024 00:00:00 GMT

Title: Pleistocene glaciomarine laminated muds in the Central Basin of the northwestern Ross Sea and their palaeoceanographic records Authors: 김부근; 손영관; 이민경; Kim, Sunghan; Lee, Jae Il; Yoo, Kyu-Cheul Abstract: Glaciomarine laminated muds around the Antarctic continental margin are important in the marine geological record related to ice sheet dynamics. Microscopic observa tion and backscattered electron imagery of Pleistocene laminated muds in the Central Basin (Ross Sea) reveal that the light laminae comprise terrigenous angular to sub angular silt-sized particles, scattered diatom fragments, and eroded sand-sized lumps of fossil-bearing mud. In contrast, the dark laminae are clayey and biogenic with very tiny pieces of fossils. These laminated muds are interpreted to have been deposited by subglacial meltwater plumes underneath the advancing glaciers that torn off the earlier-deposited and semi-consolidated diatom-rich sediments. Thus, most biogenic components of these laminated muds were recycled from older deposits, indicating that they are not related to enhanced biological production during the mud deposi tion. Our study suggests that the recycling of biogenic particles should be consid ered when interpreting the palaeoclimatic and palaeoceanographic implications of Antarctic environmental system.

Evaluation of the Marine Ice Sheet/Ice Cliff Instabilities on the Glaciers of Terra Nova Bay, Antarctica

Sun, 01 Jan 2023 00:00:00 GMT

Title: Evaluation of the Marine Ice Sheet/Ice Cliff Instabilities on the Glaciers of Terra Nova Bay, Antarctica Authors: 이현희 Abstract: 남극 빙상은 남극 대륙 위에 두껍게 성장해 흘러내려가며, 말단부에서 빙붕이나 빙설로 변형되어 해양으로 소모되고 있다. 온난화와 같은 기후 요인과 더불어 지형적, 해양적 요인으로 인해 발생하는 해양 빙상 불안정성과 해양빙벽 불안정성은 빙하의 소모를 가속시키고 있다. 빙하 접지선 배후의 기저 지형은 해양에 떠있는 빙하의 지지력에 영향을 미치며, 빙하 접지선 전면부의 빙하 표면 균열은 빙벽의 붕괴와 분리를 야기한다. 수치고도자료를 이용한 빙하기저 지형과 빙하 표면의 형태 분석은 이러한 위험요소가 나타나는 지역을 찾아내고 위험도를 평가할 수 있다. 남극빙상 말단부의 소모를 유발하는 위험인자들을 지속적으로 추적, 관찰, 평가하는 연구를 통해 해수면의 추가적인 상승 위기를 예측하고 대비해야 한다.

Hunting paleoceanographic archives of ice sheet-ocean interaction in the northwestern Ross Sea, Antarctica

Sun, 01 Jan 2023 00:00:00 GMT

Title: Hunting paleoceanographic archives of ice sheet-ocean interaction in the northwestern Ross Sea, Antarctica Authors: Kim Sookwan; De Santis Laura; Hong, Jong Kuk; Colizza Ester; Kim, Sunghan; Bergamasco Andrea; Lee Sang-Hoon; Kang, Seung-Goo; Lee, Min Kyung; Kim, Hyung Jun; Choi, Yeonjin; Geniram Andrea; 최형규; Lee, Jae Il; Yoo, Kyu-Cheul; Park, Yongcheol Abstract: The analysis of sedimentary deposits influenced by bottom currents in glaciated continental margins provides crucial insights into paleo-depositional and oceanographic conditions. These reconstructions enable the assessment of interactions between advance and retreat of grounded ice sheets and past ocean circulation patterns. However, questions regarding these interactions and their specific mechanisms remain largely unanswered due to a lack of data in this remote area. In this study, we conducted a comprehensive analysis by integrating marine geophysical data, surficial sediment cores, oceanographic measurements, and ocean circulation models. Our aim was to understand spatial and temporal variations in sedimentary and oceanographic conditions during the past glacial and interglacial periods in combination with the long-term stratigraphic evolution. By integrating and cross-referencing diverse datasets, we were able to infer how bottom-current-controlled deposits (i.e., contourites) developed along the western bathymetric high of the Central Basin in the northwestern Ross Sea margin, Antarctica. Contouritic deposits lying over and along the flanks of bathymetric highs were identified through their mound-shaped external geometry and acoustically stratified facies, characterized by reflectors pinching toward the moat. Acoustic facies and multi-beam backscatter results, in conjunction with sedimentary core data, revealed contrasting patterns. Bathymetric highs exhibited thin (<10 m thick) coarser-grained sedimentary layers with higher backscatter, while the lower slope and rise displayed thick (>10 m thick), finer-grained stratified sediments with lower backscatter. These findings indicate that seabed winnowing occurred by strong bottom current during past glacial periods as supported by sedimentological analysis. The pathways of the westward-deflected dense shelf water outflow and the westward-flowing along-slope current, as simulated by oceanographic models, explain the distinctive development of contourites influenced by bottom-current processes. Moreover, the large accumulations of sediment in the contourites, resulting from bathymetric barriers in the north of the Central Basin, may contribute to submarine slope failures.

Glacial-interglacial environmental changes in the Drake Passage over the past 600 kyrs

Sun, 01 Jan 2023 00:00:00 GMT

Title: Glacial-interglacial environmental changes in the Drake Passage over the past 600 kyrs Authors: Kim, Sunghan; Lee, Jae Il; Yoo, Kyu-Cheul; Lee, Min Kyung; Young-Suk Bak; 강명일; Sookwan Kim; 박진구 Abstract: Oceanographic conditions in the Southern Ocean are closely related to the oceanic frontal system. Glacial-interglacial changes in cryosphere influence variations in oceanic fronts in the Southern Ocean and vice versa, causing changes in surface water productivity, nutrient utilization, bottom water chemistry, and/or bottom current intensity. Here, we documented geochemical, nitrogen isotope, and grain size records over the last 600 kyrs from the Drake Passage with previously published data to compare between glacial and interglacial oceanic conditions from surface to bottom. Biogenic opal (diatom) and export productions were high during interglacial periods and low during glacial periods. Surface water production was dominated by open ocean species during both glacial and interglacial periods without a clear glacial-interglacial change in sea ice species. After Marine Isotope Stage (MIS) 9, interglacial biogenic opal and diatom abundance increased distinctively with decreased terrestrial influence. Nutrient utilization increased (decreased) during interglacial (glacial) periods with increased (decreased) surface water production, particularly after MIS 9. This indicates that surface water production was regulated by light availability in association with sea ice duration/extent. According to good correlation between sortable silt mean grain size (SS MGS) and %sortable silt, SS MGS can be used for bottom current intensity indicator in this study; increased (decreased) bottom current during glacial (interglacial) periods. Increased glacial bottom current is likely related to southwestward flowing bottom current. Interglacial bottom current intensity became also significantly weakened after MIS 9. However, outstanding interglacial warmth in the Drake Passage occurred from MIS 9, not following the global trend to occur after MIS 11. This implies that more studies from the Southern Ocean in response to the Mid-Brunhes Event are required in the future.