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남극해 인도양 해역에 위치한 콘래드 해령 지역의 마지막 빙하기 이후 생물기원 오팔 생산의 변화
양주연,Minoru Ikehara,최혁,김부근 한국해양과학기술원 2023 Ocean and Polar Research Vol.45 No.3
Biological pump processes generated by diatom production in the surface water of the Southern Ocean play an important role in exchanging CO2 gas between the atmosphere and ocean. In this study, the biogenic opal content of the sediments was measured to elucidate the variation in the primary production of diatoms in the surface water of the Southern Ocean since the last glacial period. A piston core (COR-1bPC) was collected from the Conrad Rise, which is located in the Indian sector of the Southern Ocean. The sediments were mainly composed of siliceous ooze, and sediment lightness increased and magnetic susceptibility decreased in an upward direction. The biogenic opal content was low (38.9%) during the last glacial period and high (73.4%) during the Holocene, showing a similar variation to that of Antarctic ice core ΔT and CO2 concentration. In addition, the variation of biogenic opal content in core COR-1bPC is consistent with previous results reported in the Antarctic Zone, south of the Antarctic Polar Front, in the Southern Ocean. The glacial-interglacial biogenic opal production was influenced by the extent of sea ice coverage and degree of water column stability. During the last glacial period, the diatom production was reduced due to the penetration of light being limited in the euphotic zone by the extended sea ice coverage caused by the lowered seawater temperature. In addition, the formation of a strong thermocline in more extensive areas of sea ice coverage led to stronger water column stability, resulting in reduced diatom production due to the reduction in the supply of nutrient-rich subsurface water caused by a decrease in upwelling intensity. Under such environmental circumstances, diatom productivity decreased in the Antarctic Zone during the last glacial period, but the biogenic opal content increased rapidly under warming conditions with the onset of deglaciation.
Asahi, H.,Kender, S.,Ikehara, M.,Sakamoto, T.,Takahashi, K.,Ravelo, A.C.,Alvarez Zarikian, C.A.,Khim, B.K.,Leng, M.J. Pergamon Press 2016 Deep-sea research. Part II, Topical studies in oce Vol.125 No.-
A continuous composite oxygen isotope (δ<SUP>18</SUP>O) stratigraphy from benthic foraminifera in the Bering Sea was reconstructed in order to provide insight into understanding sea-ice evolution in response to Northern Hemisphere Glaciation. Oxygen isotope records from multiple species of benthic foraminifera at Integrated Ocean Drilling Program (IODP) Expedition 323 Site U1343 (54<SUP>o</SUP>33.4'N, 176<SUP>o</SUP>49.0'E, water depth 1950m) yield a highly refined orbital-scale age model spanning the last 1.2Ma, and a refined age model between 1.2 and 2.4Ma. An inter-species calibration was used to define species offsets and to successfully obtain a continuous composite benthic δ<SUP>18</SUP>O record, correlated with the global composite benthic δ<SUP>18</SUP>O stack curve LR04 to construct an orbital-scale age model. The consistency of the benthic δ<SUP>18</SUP>O stratigraphy with biostratigraphy and magnetostratigraphy confirms the reliability of both methods for constraining age. The time difference between cyclic changes in sedimentary physical properties and glacial-interglacial cycles since 0.8Ma is notable, and suggests that physical properties alone cannot be used to construct an orbital-scale age model. Amplitude changes in physical properties and a significant drop in the linear sedimentation rate during glacials after 0.9Ma indicate that the glacial sea-ice edge extended beyond the Bering Sea Slope (Site U1343) at this time.