https://repository.kopri.re.kr/handle/201206/14831 2026-04-21T10:20:03Z 2026-04-21T10:20:03Z Hong, Jong Kuk https://repository.kopri.re.kr/handle/201206/15403 2024-04-08T07:52:12Z 2023-12-01T00:00:00Z

Title: Survey of Geology and Seabed Environmental Change in the Arctic Seas Authors: Hong, Jong Kuk

2023-12-01T00:00:00Z Kang, Seung-Goo Jang U. Geun https://repository.kopri.re.kr/handle/201206/14902 2023-12-06T16:38:27Z 2023-01-01T00:00:00Z

Title: Frequency-Domain Reverse-Time Migration with Analytic Green's Function for the Seismic Imaging of Shallow Water Column Structures in the Arctic Ocean Authors: Kang, Seung-Goo; Jang U. Geun Abstract: Seismic oceanography can provide a two- or three-dimensional view of the water column thermocline structure at a vertical and horizontal resolution from the multi-channel seismic dataset. Several seismic imaging methods and techniques for seismic oceanography have been presented in previous research. In this study, we suggest a new formulation of the frequency-domain reverse-time migration method for seismic oceanography based on the analytic Green's function. For imaging thermocline structures in the water column from the seismic data, our proposed seismic reverse-time migration method uses the analytic Green's function for numerically calculating the forward- and backward-modeled wavefield rather than the wave propagation modeling in the conventional algorithm. The frequency-domain reverse-time migration with analytic Green's function does not require significant computational memory, resources, or a multifrontal direct solver to calculate the migration seismic images as like conventional reverse-time migration. The analytic Green's function in our reverse-time method makes it possible to provide a high-resolution seismic water column image with a meter-scale grid size, consisting of full-band frequency components for a modest cost and in a low-memory environment for computation. Our method was applied to multi-channel seismic data acquired in the Arctic Ocean and successfully constructed water column seismic images containing the oceanographic reflections caused by thermocline structures of the water mass. From the numerical test, we note that the oceanographic reflections of the migrated seismic images reflected the distribution of Arctic waters in a shallow depth and showed good correspondence with the anomalies of measured temperatures and calculated reflection coefficients from each XCDT profile. Our proposed method has been verified for field data application and accuracy of imaging performance.

2023-01-01T00:00:00Z Kim Hyo-Im Cho Hyen Goo Lee Sangmi Koo Hyo Jin Hong, Jong Kuk Jin, Young Keun https://repository.kopri.re.kr/handle/201206/14857 2023-12-06T16:37:46Z 2023-01-01T00:00:00Z

Title: Spatial distribution of manganese oxide minerals in the natural ferromanganese nodule of the Arctic Sea: A view from Raman spectroscopy Authors: Kim Hyo-Im; Cho Hyen Goo; Lee Sangmi; Koo Hyo Jin; Hong, Jong Kuk; Jin, Young Keun Abstract: Knowledge of the spatial distribution of manganese oxide minerals in the natural ferromanganese nodules provides improved prospects for understanding the geochemical processes involved in nodule formation. In this study, we report a series of micro-laser Raman spectra along with a line profile from the center to the rim of a spherical ferromanganese nodule from the East Siberian Sea in the Arctic region. For the Raman spectra obtained at the center of the nodule, the characteristic Raman bands for todorokite at similar to 733, similar to 508, and similar to 240 cm(-1) were clearly observed, suggesting that the todorokite is predominant in the central part of the nodule. As the data acquisition point moved away from the center to the rim (D), the Raman bands corresponding to the todorokite decreased, while the intensity of the 588 cm(-1) band corresponding to the layered manganate minerals (i.e., birnessite) increased, suggesting that the proportion of manganate phases with a tunnel structure decreases with nodule growth. In addition, the distinct Raman bands at similar to 280 and 403 cm(-1) indicated that the triclinic birnessite is prevalent in the outer regions of the nodule. Semi-quantitative measurement of the intensity of diagnostic Raman bands for todorokite (I-733) allows us to effectively observe the spatial distribution of manganese oxide minerals in the ferromanganese nodule. At the center of the nodule, I-733 was similar to 0.7. Despite a few fluctuations, I-733 clearly decreased from similar to 0.7 to similar to 0.2 with increasing D from 0 to 7500 mu m, indicating that the relative fraction of todorokite in nodules significantly decreases with nodule growth. This study highlights that a highly resolved spatial distribution of manganate mineral phases in ferromanganese nodules can provide a historical record of the formation process and geochemical conditions.

2023-01-01T00:00:00Z Kim, So-Young Park, Taewook Marret Fabienne Potvin Eric Cho, Kyoung-Ho Jung, Jinyoung Lee, Youngju La, Hyoung Sul Ha, Sun-Yong Kim Seung-Kyu Kang, Sung-Ho Yang, Eun Jin Nam, Seung-il Hong, Jong Kuk https://repository.kopri.re.kr/handle/201206/14840 2023-12-06T16:37:30Z 2023-01-01T00:00:00Z

Title: Strong regionalism in dinoflagellate cysts in recent sediments from the Chukchi-East Siberian Seas, Arctic Ocean Authors: Kim, So-Young; Park, Taewook; Marret Fabienne; Potvin Eric; Cho, Kyoung-Ho; Jung, Jinyoung; Lee, Youngju; La, Hyoung Sul; Ha, Sun-Yong; Kim Seung-Kyu; Kang, Sung-Ho; Yang, Eun Jin; Nam, Seung-il; Hong, Jong Kuk Abstract: The Pacific sector of the Arctic Ocean, a region with the fastest sea-ice loss in recent decades, is experiencing unprecedented biological regime shifts in its marine ecosystems today. However, a shelf-wide characterization of marine plankton communities over this region and environmental processes behind it remain largely unresolved, despite phytoplankton phenology is now considered to be an important factor for assessing how Arctic Ocean interacts with global climate change. Here, we present the first detailed description of recent dinoflagellate cyst assemblages in 32 surface sediment samples from the Chukchi-East Siberian Sea shelves, the Pacific Arctic Ocean, to examine their biogeographic patterns and associated environmental forcing factors. We find a strong regionalization in the species composition and distribution along the shallow-shelf cyst accumulation zone; in the Chukchi Sea sector, northward flow of warm-Pacific water along with extreme seasonality, sufficient nutrient supplies and higher light availability leads to a large occupation of cosmopolitan, opportunistic-nature taxa, whilst the East Siberian Sea sector with more extensive sea-ice cover and lower temperatures is primarily dominated by "round brown spiny cyst" taxa that have a strong affinity for cold, polar conditions. Specifically, an exclusive dominance of heterotrophic taxa at the East Siberian Sea region is inferred to be closely tied to Atlantic-origin water intrusions that lift nutrient-rich, cold bottom water up to oligotrophic surface layer to grow diatoms and other prey organisms. The observed contrast in this geographical "hot spot", where the Pacific-and Atlantic-origin waters face each other, clearly manifests a growing expansion of southern waters into an increasingly ice-free Arctic Ocean that reshapes Arctic Ocean biogeography from the base of marine food chains. Our study highlights considerable potential of dinoflagellate cysts as a valuable environmental proxy to indicate complex interactions between ocean physics and marine biology under the rapidly changing Arctic climate system.

2023-01-01T00:00:00Z