https://repository.kopri.re.kr/handle/201206/9835 2026-04-19T16:21:09Z 2026-04-19T16:21:09Z Park, Kwangkyu Kim, Jung-Hyun Asahi, Hirofumi Polyak, Leonid Khim, Boo-Keun Schreck, Michael Niessen, Frank Kong, Gee-Soo Nam, Seung-il https://repository.kopri.re.kr/handle/201206/12434 2022-03-24T07:15:18Z 2019-01-01T00:00:00Z

Title: Cyclostratigraphic age constraining for Quaternary sediments in the Makarov Basin of the western Arctic Ocean using manganese variability Authors: Park, Kwangkyu; Kim, Jung-Hyun; Asahi, Hirofumi; Polyak, Leonid; Khim, Boo-Keun; Schreck, Michael; Niessen, Frank; Kong, Gee-Soo; Nam, Seung-il Abstract: The Quaternary paleoenvironmental history of the Arctic Ocean remains uncertain, mainly due to the limited chronological constraints, especially beyond the 14C dating limits of accelerator mass spectrometry (AMS). The difficulty in establishing reliable chronostratigraphies is mainly attributed to low sedimentation rates and diagenetic sediment changes, resulting in very poor preservation of microfossils and altered paleomagnetic records. In the absence of independent chronostratigraphic data, the age model of Pleistocene sediments from the Arctic Ocean is mainly based on cyclostratigraphy, which relates lithologic changes to climatic variability on orbital time scales. In this study, we used the Mn/Al record measured from the sediment core ARA03B-41GC retrieved from the Makarov Basin in the western Arctic Ocean. The Mn/Al variation were tuned to the global benthic oxygen isotope stack (LR04) curve under different assumptions for computational correlation. Regardless of assumptions, our computational approach led to similar ages of about 600-1,000 ka for the bottom part of the core. These age models were up to about 200 ka older than those derived from lithostratigraphic approaches. Interestingly, our new age models show that the Ca/Al peak, a proxy for a detrital input from the Laurentide Ice Sheet, first occurred about 150 ka earlier than those previously proposed. Therefore, our results suggest that the glaciers in northern North America developed more extensively at about 810 ka than in earlier glacial periods, and influenced the sedimentary and paleoceanographic environments of the Arctic Ocean much earlier than previously thought. In order to establish a more comprehensive age model, more work is needed to validate our findings with different sediment cores recovered from the western Arctic Ocean.

2019-01-01T00:00:00Z Park, Kwangkyu Nam, Seung-il Kim, Jung-Hyun Khim, Boo-Keun Vogt, Christoph Polyak, Leonid https://repository.kopri.re.kr/handle/201206/12489 2022-03-24T07:15:19Z 2019-01-01T00:00:00Z

Title: Changes of sedimentary mineral composition in the Makarov Basin for the last ~1 Ma Authors: Park, Kwangkyu; Nam, Seung-il; Kim, Jung-Hyun; Khim, Boo-Keun; Vogt, Christoph; Polyak, Leonid Abstract: The Quaternary is characterized by the development of cryosphere which mainly consists of sea ice and ice sheet. In spite of its significance in terms of climate changes during the Quaternary, cryosphere changes in the Arctic Ocean and the surrounding lands have remained uncertain. Here, we present long sedimentary records which cover early to late Quaternary (~1 Ma), focusing on mineralogical features to constrain both sedimentary sources and transport mechanisms. In general, quartz and feldspars dominate the bulk mineral composition, but carbonates and pyroxenes are also abundant. Dolomite contents drastically vary after the end of early-middle Pleistocene Transition (EMPT) and show periodic occurrence since the middle Brunhes. The occurrence of detrital dolomite indicates the onset of the Laurentide Ice Sheet (LIS) impact on the Arctic Ocean at MIS 20 (~800 ka) and periodic impacts of ~100 kyr since MIS 12 (~450 ka) based on wavelet analysis. The contents of other minerals such as quartz, plagioclase, K-feldspar, and pyroxenes and their ratios also show potential as indicators of sedimentary source changes in the continental margins of the Arctic Ocean. However, further studies are needed to better constrain mineral source areas and transport mechanisms in relation to cryosphere changes of the Arctic region during the Quaternary.

2019-01-01T00:00:00Z Schreck, Michael Nam, Seung-il Polyak, L. Vogt, C. Kong, G.S. Stein, R. Matthiessen, J. Niessen, F. https://repository.kopri.re.kr/handle/201206/10870 2022-03-24T07:14:28Z 2018-07-01T00:00:00Z

Title: Improved Pleistocene sediment stratigraphy and paleoenvironmental implications for the western Arctic Ocean off the East Siberian and Chukchi margins Authors: Schreck, Michael; Nam, Seung-il; Polyak, L.; Vogt, C.; Kong, G.S.; Stein, R.; Matthiessen, J.; Niessen, F. Abstract: Sediment cores from the East Siberian and Chukchi margins and adjacent basins are used to refine the upper Pleistocene stratigraphy and better constrain the timing of major glacial advances in the western Arctic Ocean. Cores have been analysed using high-resolution non-destructive physical properties (density, magnetic susceptibility and colour) and X-ray fluorescence elemental measurements (manganese and calcium contents). All analysed cores reveal a spatially coherent stratigraphic pattern that enables robust correlations from the East Siberian margin to the Mendeleev and Northwind Ridges, thus highlighting the potential of such multiproxy approach for improving stratigraphic framework. The distribution of sedimentary units resulting from core correlation indicates decreasing sedimentation rates by more than one order of magnitude from the East Siberian margin east- and northwards, reflecting an increased distance from the main sediment sources, increasing seaice cover, and longer residence times in the Beaufort Gyre circulation. The stratigraphy presented, consistent with existing geophysical data, indicates the most recent major glacial advance from the East Siberian margin with ice grounding at water depth > 800？m during estimated Marine Isotope Stages 4/3, roughly contemporaneous with the Middle Weichselian glaciation in northern Eurasia. Earlier glacial events are potentially indicated by glaciogenic units in cores away from the margin, where they are not overprinted by a younger ice advance. Sediment thickness increase towards the Siberian margin also suggests the possibility of a limited MIS 2 glaciation, although no direct evidence for such an ice sheet has been found thus far.

2018-07-01T00:00:00Z ASAHI, HIROFUMI Son, Yeong Ju Nam, Seung-il Mackensen, Andreas STEIN, RUEDIGER https://repository.kopri.re.kr/handle/201206/12617 2022-03-24T07:15:07Z 2018-01-01T00:00:00Z

Title: Neogloboquadrina pachyderma in the modern Arctic Ocean: a potential for its morophological variation for paleoceanographic reconstruction Authors: ASAHI, HIROFUMI; Son, Yeong Ju; Nam, Seung-il; Mackensen, Andreas; STEIN, RUEDIGER Abstract: In the Arctic Ocean, predominance of polar planktic foraminifera Neogloboquadrina pachyderma sinistral prevents utilities using their thanocoenosis in order to understand paleoenvironmental conditions in the Arctic Ocean. Although potential availability of N. pachyderma’s morphological variation for paleoceanographic reconstruction has been presented by recent studies, its application is still limited within N. Atlantic side of the Arctic Ocean. Additional data from the Pacific side of the Arctic Ocean is strongly anticipated to extend their paleoceanographic utility over the entire Arctic Ocean. Here, we will present the modern distribution of morphological variations of N. pachyderma, using 82 surface sediment samples collected in the western Arctic Ocean. Within investigated surface sediment samples, we have encountered total of seven morphological variations of N. pachyderma, compromising their description of previous study (Eynaund et al., 2010). Distinct geographic dominance of “Large-sized (>250 μm)” N. pachyderma along the offshore of Northern Alaskan margin suggests its preferences in the relatively warm and low-salinity condition. Using the distribution pattern of morphological variations of N. pachyderma, we have succeeded to establish transfer functions (PF-based TFs) for salinity, temperature and summer ice concentration. Applications of established PF-based TFs to four downcores taken from east-west transects crossing over the Chukchi Sea showed distinct opposite trend at eastern/western side of the Transpolar Drift (TPD): Clear warming, freshening and summer sea-ice concentration reduction were reconstruded at the western side of TPD, whilst rather cooling, increasing in both salinity and summer sea-ice concentration were witnessed in the eastern part during last 6,000 years. Such regional heterogenic response in the Chukchi Sea is presumably linked to relocation of TPD via long term shift in the atmospheric forcing during the Holocene.

2018-01-01T00:00:00Z