https://repository.kopri.re.kr/handle/201206/15849 2026-04-05T21:39:16Z 2026-04-05T21:39:16Z Kim, Minkyung Lee, Hanbyul Lee, Subin Han, Yeongcheol Kim, Ok-Sun https://repository.kopri.re.kr/handle/201206/16143 2025-10-22T02:08:09Z 2025-07-01T00:00:00Z

Title: Millennial-scale depth-resolved ancient microbial diversity and pathogenic potential in Styx Glacier, Antarctica Authors: Kim, Minkyung; Lee, Hanbyul; Lee, Subin; Han, Yeongcheol; Kim, Ok-Sun Abstract: The cryosphere offers crucial insights into historical ecosystems and biomes on our planet, preserving ancient microorganisms and other biological materials. The recent discovery of pathogens released from permafrost and Arctic regions has emphasized potential threats to human health. However, the ancient microbial diversity in Antarctic glaciers remains largely unexplored. To address this gap, we investigated the microbial diversity and the presence of potential pathogens in the Styx ice core (Northern Victoria Land, Antarctica) with millennialscale dated between 525 and 1978 CE. A total of 656 isolates, representing 27 species, were obtained by incubation on four different media at 10 degrees C and 25 degrees C. Among the cultured isolates, the Alphaproteobacteria was the predominant class, with Sphingomonas echinoides (70 % at 10 degrees C) and Bradyrhizobium elkanii (76.2 % at 25 degrees C) being the most prevalent species across all depths. Genomic analysis of four isolates (Roseomonas mucosa, Gordonia hongkongensis, Paenibacillus glucanolyticus, and Dermacoccus nishinomiyaensis) among nine species suspected to be potential pathogens was performed to identify the presence of antibiotic resistance and virulence genes. Amino acid sequences of HbhA, a mycobacterial surface antigen, in G. hongkongensis strains exhibit AKKA repeat motifs, similar to those found in pathogenic Mycobacterium tuberculosis and Nocardia cyriacigeorgica. Furthermore, the hemolysin produced by R. mucosa and P. glucanolyticus showed no activity at 25 degrees C but exhibited activity at 37 degrees C. This study demonstrated that glacial ice contains core microbiomes and also highlighted the presence of potential opportunistic pathogens, resonating between ancient microbiology and contemporary environmental health concerns.

2025-07-01T00:00:00Z Azharuddin Syed Ahn Jinho Ryu Yeongjun Brook Ed Salehnia Nasrin https://repository.kopri.re.kr/handle/201206/16301 2025-10-31T05:54:47Z 2024-01-01T00:00:00Z

Title: Millennial-Scale Changes in Atmospheric Nitrous Oxide During the Holocene Authors: Azharuddin Syed; Ahn Jinho; Ryu Yeongjun; Brook Ed; Salehnia Nasrin Abstract: Nitrous oxide (N2O) is an important greenhouse gas which destroys the ozone in the stratosphere. Primary sources of atmospheric N2O are nitrification and denitrification in terrestrial soils and the ocean, and the main sink is photolysis in the stratosphere. Studies have mostly focused on the climate-related response of N2O during glacial-interglacial periods. However, its mechanism of variation during the Holocene remains unclear. We present a high-resolution N2O record from the South Pole Ice (SPICE) core covering the Holocene epoch. The millennial-scale N2O trend agrees with existing records. We constructed a Holocene composite consisting of the new N2O measurements in SPICE and existing records from other ice core sites. The N2O composite reveals four distinct periods of N2O variation during 11.5-10.0 ka, 10.0-6.2 ka, 6.2-2.2 ka, and 2.2-1.4 ka, including two maxima in 11.0-10.0 ka and 3.0-2.2 ka and minima in 8.8-6.2 ka and approximately 1.4 ka. Apart from these, our new high-resolution record from SPICE shows a short-term N2O decrease around 2.8 ka which is not observed in other records possibly due to lower sample resolution and/or higher age smoothing. Comparison of our new Holocene N2O composite with the paleo-proxy records suggests the plausible linkage of major monsoon (Asian, North African, South and North American, and Australian-Indonesian monsoon) and upwelling (Arabian Sea and Eastern Tropical South Pacific) regions in regulating the atmospheric N2O during the Holocene. Nitrous oxide (N2O) is an important greenhouse and ozone-depleting gas. The growing level of N2O in the atmosphere is of global concern, and records of past N2O variations can provide an essential context for understanding the links between N2O and climate change. In this study, we report a new, high-quality N2O record covering the Holocene epoch using an ice core obtained from the South Pole. Our record shows four important periods of N2O variation during 11.5-10.0 ka, 10.0-6.2 ka, 6.2-2.2 ka, and 2.2-1.4 ka. These include two local N2O maxima in 11.0-10.0 ka and 3.0-2.2 ka and minima in 8.8-6.2 ka and approximately 1.4 ka. Comparison with climate records suggests that the variation in monsoon precipitation and ocean productivity contributed to centennial- to millennial-scale N2O variations during the Holocene. High-resolution N2O record from the South Pole Ice core covering the Holocene epoch is investigated for N2O variationInsight into the key drivers of atmospheric N2O on millennial time scales during the Holocene is providedN2O exhibits two local maxima during 11.0-10.0 ka and 3.0-2.2 ka, and two local minima during 8.8-6.2 ka and at around 1.4 ka

2024-01-01T00:00:00Z Yi Yoo Soo Han, Yeongcheol https://repository.kopri.re.kr/handle/201206/16357 2025-11-06T07:50:06Z 2024-01-01T00:00:00Z

Title: Theoretical Insights into Gas Migration Within Ice on Earth and Icy Celestial Bodies Authors: Yi Yoo Soo; Han, Yeongcheol Abstract: Atmospheric gases trapped in icy environments, such as Earth's polar regions and Jupiter's moon Europa, offer a unique opportunity to explore paleoclimate and astrogeological history. While previous studies have addressed the diffusive behaviors of these gases and their implications for paleoclimatological and geochronological reconstructions, the underlying mechanisms of gas migration in ice remain largely unexplored. Achieving an atomistic-level understanding of gas migration is therefore essential for improving our knowledge of the long-term behavior of gases in icy environments. In this study, we investigated the migration of noble gases encapsulated in isolated air bubbles within bulk ice using density functional theory calculations. We focused on both the dissolution at the gas-ice interface and the subsequent molecular diffusion through the ice lattice. Our results show that energy barriers for dissolution and molecular diffusion increase almost linearly with atomic size, leading to nonlinear, exponential-like decreases in solubility and diffusivity, due to their Arrhenius behavior in relation to the corresponding energy barriers. These energy barriers primarily arise from the structural distortions in the ice lattice, as it accommodates noble gas atoms. Additionally, our findings indicate that dissolution is energetically both more demanding and slower than molecular diffusion, making it the rate-limiting step in gas migration through ice. These findings provide valuable insights into gas migration and fractionation mechanisms in Earth's polar ice, highlighting the importance of incorporating atomic-level interactions into geochronological models. By deepening our fundamental understanding of gas mobility, this work not only advances methodologies for analyzing Earth's ice but also broadens our perspective on extraterrestrial icy environments, with potential implications for the search for life-supporting conditions beyond Earth.

2024-01-01T00:00:00Z Nyamgerel Yalalt Han, Yeongcheol Hwang, Heejin Han, Changhee Hong, Sang-Bum Hur, Soon Do Lee Jeonghoon https://repository.kopri.re.kr/handle/201206/16381 2025-11-06T08:08:16Z 2024-01-01T00:00:00Z

Title: Climate-related variabilities in the Styx-M ice core record from northern Victoria Land, East Antarctica, during 1979-2014 Authors: Nyamgerel Yalalt; Han, Yeongcheol; Hwang, Heejin; Han, Changhee; Hong, Sang-Bum; Hur, Soon Do; Lee Jeonghoon Abstract: The historical climate variability in East Antarctica inferred from ice cores remains under debate owing to the vastness and complexity of the region. This study evaluates the potential climate variabilities in the Styx-M ice core records (delta 18O, d-excess, and snow accumulation) from northern Victoria Land adjacent to the Ross Sea sector of East Antarctica during 1979-2014. Results show that the primary moisture source in this area is the Pacific Ocean sector. Although the annual mean delta 18O values was limited to directly indicate the temperature changes, a weak relevance between the average delta 18O values and the temperature signal during the austral summer season is detectable. delta 18O, d-excess, and snow accumulation correlate with sea surface temperature and sea ice extent in the Ross Sea sector. A coupled influence of the SAM, ASL, and ENSO climate indices is expected, because the oceanic environment in this region is influenced by them. The pronounced intrusion of oceanic moisture coupled with atmospheric circulation patterns over the Ross Sea region makes the Styx-M ice core a promising record of the local oceanic conditions, with the snow accumulation rate being a direct proxy. Additionally, the analysis of trace elements from 1979 to 1999 revealed the presence of crustal dust sourced from the Transantarctic Mountains, as well as non-crustal sources, both intricately linked with atmospheric transport. These results demonstrate that the contributions of-and variations in-oceanic conditions associated with atmospheric circulation changes are detectable and dominant in the Styx-M ice core. This study serves as a basis for interpreting longer parts of the Styx-M ice core.

2024-01-01T00:00:00Z