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Molecular Mechanisms of Gas？Ice Interfacial Transport: Size- and Charge-Dependent Fractionation during Bubble Close-off

2025-11-01T00:00:00Z

Title: Molecular Mechanisms of Gas？Ice Interfacial Transport: Size- and Charge-Dependent Fractionation during Bubble Close-off Authors: Yi, Yoo Soo; Han, Yeongcheol Abstract: Gas？ice interfacial transport phenomena are essential across diverse cryogenic environments, ranging from gas fractionation in polar glaciers to the preservation of cosmogenic noble gases on icy celestial bodies. Bubble close-off in polar glaciers is a compelling example of the complex gas？ice interactions that challenge the interpretation of paleoclimate records preserved in ice cores. While previous studies have provided valuable insights, the molecular mechanisms governing fractionation, especially those involving both geometric and electronic characteristics, remain incompletely understood. Here, using density functional theory (DFT) calculations, we determine effective permeation energy barriers (EP) for noble gases (He, Ne, Ar, Kr, and Xe) and molecular gases (N2, O2, and CO2) through a model ice layer. Our results reveal that noble gases largely follow a size-dependent trend, whereas molecular gases deviate from such a simple relationship due to more complex gas？ice interactions resulting from their anisotropic charge distribution. The exponential dependence of permeation rates on EP accounts for the observed nonlinear depletion phenomenon. He and Ne, with their smaller sizes and weaker surface adsorption, exhibit higher permeation rates and rapid depletion from closed-off bubbles. Conversely, larger noble gases and molecular gases are preferentially retained due to increased energy barriers. Notably, molecular gases show significantly lower permeation rates than Ne despite comparable effective cross-sectional sizes, owing to stronger adsorption affinity. Chemical hardness, a descriptor reflecting electronic properties, helps reconcile the fractionation patterns observed for both gas types, indicating that interfacial interactions, not molecular size alone, govern transport through ice layers. These findings provide insights into gas preservation in diverse cryogenic environments, which is essential for the fidelity of paleoclimate reconstruction and the rational design of materials for selective transport. Discrepancies with field observations underscore the role of structural heterogeneities, such as grain boundaries, suggesting that bubble close-off fractionation involves additional pathways beyond idealized lattice permeation.

Tracing stratospheric transport using sub-annual plutonium-239 fallout in polar ice cores

2025-10-01T00:00:00Z

Title: Tracing stratospheric transport using sub-annual plutonium-239 fallout in polar ice cores Authors: Shin, Jinhwa; Lee, Seungmi; Han, Yeongcheol; Hwang, Heejin; Ro, Seokhyun; Hur, Soon Do; Hong, Sang-Bum Abstract: Polar ice cores preserve high-resolution archives of historical atmospheric transport, providing unique insights into long-term stratospheric processes. Here, we present the first subannual plutonium-239 (239Pu) deposition records from Greenland and Antarctic ice cores (1940 to 1980 CE). The limited or delayed fallout from Ivy Mike (1952 CE) compared to Operation Castle (1954 CE), despite their detonation in close proximity, exemplifies how stratospheric circulation and seasonal dynamics create periods of reduced transport to Antarctica. These records also reveal seasonal fallout patterns in Antarctica, with enhanced deposition during austral summers driven by stratosphere-troposphere exchange. Our findings refine current representations of global aerosol dispersion and provide additional constraints for modeling atmospheric processes, particularly those driven by volcanic eruptions and geoengineering interventions.

Draft genome sequence of Sphingomonas sp. GlSt437 isolated from the Styx Glacier, Antarctica

2025-08-01T00:00:00Z

Title: Draft genome sequence of Sphingomonas sp. GlSt437 isolated from the Styx Glacier, Antarctica Authors: Kim, Minkyung; Lee, Subin; Kim, Ok-Sun Abstract: We present the draft genome of Sphingomonas sp. GlSt437 isolated from the Styx ice core, Antarctica. The genome of strain GlSt437 comprises 3,409,635 bp with a GC content of 64.9%, encoding 3,274 genes.

Identification of 320000-year-old blue ice at the surface of the Elephant Moraine region, East Antarctica

2025-08-01T00:00:00Z

Title: Identification of 320000-year-old blue ice at the surface of the Elephant Moraine region, East Antarctica Authors: Lee, Giyoon; Ahn, Jinho; Ju, Hyeon Tae; Ikumi Oyabu; Florian Ritterbusch; Kim, Songyi; Moon, Jangil; Lee, Joohan; Han, Yeongcheol; Hur, Soon Do; Kenji Kawamura; Zheng-Tian Lu; Wei Jiang; Guo-Min Yang Abstract: For addressing important paleoclimatic questions, such as the cause of the Mid-Pleistocene Transition (MPT), the search for one-million-year-old ice is of great interest. Antarctic blue-ice areas (BIAs), where ancient ice outcrops on the surface of ice sheet, offer promising sites for identifying ice spanning the MPT period. To date, only two sites, the Allan Hills BIA and the Mullins Glacier in East Antarctica, have been identified as areas that contain ancient ice older than one million years. We investigated icefields in the Elephant Moraine and Reckling Moraine regions of East Antarctica to contribute to the search for ancient ice spanning the MPT. Ice-penetrating radar surveys revealed that ice thickness ranged from 200 m to 800 m across the icefields. The 81Kr dating of the surface ice (<10 m) showed ages of 83？119 kyr BP (Before Present) and 93？124 kyr BP for blue ice in the Meteorite City Icefield and 320？385 kyr BP in the Elephant Moraine Main Icefield. We also analyzed several gas compositions (δ15N-N2, δ18O-O2, δO2/N2, δAr/N2, CO2, CH4, and N2O) and revealed that gas records at very shallow depths are altered. A comparison of stable water isotopes (δ18Oice and δ2Hice) indicated that the original deposition site of the Elephant Moraine Main Icefield experienced colder condition than those of the nearby icefields. Given these findings, we expect that ice spanning the MPT period can be retrieved from the Elephant Moraine Main Icefield with only a few hundred meters of drilling.