Ulleung Island Research Articles

Long-Term Changes in Deep Ocean Currents between Ulleung Island and Dok Island in the East Sea from 1996 to 2023

This study presents a comprehensive analysis of long-term deep ocean currents between Ulleung Island and Dok Island in the East Sea, based on data observed from the East Sea Current Measurement 1 (EC1) mooring station spanning from 1996 to 2023. The deep current at the Ulleung Interplain Gap, a trough situated between Ulleung Island and Dok Island, originates from the Japan Basin, a region where deep water formation occurs within the East Sea. The southward flow and velocity of this deep water are reflective of both regional and global climate dynamics. Understanding these dynamics is crucial for assessing environmental impact, both locally in Korea and globally. Significant trends and anomalies were identified in the zonal and meridional velocities within the 1,800 and 2,500-meter depth range. Data from 2012 to 2014 required corrections due to unit inconsistencies, which, after adjustment, revealed a deceleration of the southward bottom current, with speeds decreasing from 1.49 cm s<sup>-1</sup> in November 1996 to 1.14 cm s<sup>-1</sup> in April 2023. These changes may be linked to global climate variations and bottom water formation in the Japan Basin, influencing regional circulation patterns. The findings highlight the importance of sustained ocean monitoring and enhanced data management to ensure the accuracy and utility of long-term oceanographic datasets.

Immunostimulatory activity of the aqueous extract from the leaves of Sambucus racemosa subsp. pendula through TLR4‑dependent JNK activation in RAW264.7 cells.

Sambucus racemosa subsp. pendula (SRP) is an endemic plant of Korea, exclusively found on Ulleungdo Island. SRP is widely used as both a traditional medicine and food source. However, there is a lack of research on the pharmacological activities of SRP. Therefore, the present study aimed to explore the potential use of SRP leaves (SRPL) as a natural immunostimulant by analyzing its macrophage activation properties and the underlying mechanisms of action. Among the various extraction conditions, SRPL (AE20-SRPL) extracted with 100% distilled water at 20˚C induced the highest nitric oxide (NO) production in RAW264.7 cells. Thus, the further studies were performed using AE20-SRPL. AE20-SRPL increased the production of immunostimulatory factors such as NO, prostaglandin E2, inducible nitric oxide synthase, cyclooxygenase-2, IL-1β and TNF-α and phagocytosis in a dose-dependent manner in RAW264.7 cells without exhibiting cytotoxicity. Among Toll-like receptor (TLR)2 and TLR4, inhibition of TLR4 significantly reduced AE20-SRPL-mediated increases in the production of immunostimulatory factors and phagocytosis in RAW264.7 cells. Furthermore, in RAW264.7 cells, inhibition of JNK, one of the components of MAPK signaling along with ERK1/2 and p38, attenuated the AE20-SRPL-mediated increases in the production of immunostimulatory factors and phagocytosis. Additionally, AE20-SRPL induced the phosphorylation of JNK and inhibition of TLR4 reduced AE20-SRPL-mediated JNK phosphorylation. These results suggested that AE20-SRPL may enhance the production of immunostimulatory factors and phagocytosis through TLR4-dependent activation of JNK in macrophages. Although the present study is limited to in vitro research using a cell model, AE20-SRPL demonstrated potential as a natural material capable of inducing macrophage activation for immune enhancement.

Aruncus dioicus var. kamtschaticu: A Newly Identified Source of Lactucaxanthin (ε,ε-Carotene-3,3′-diol)

Green leafy vegetables are rich in lipophilic metabolites such as carotenoids, phytosterols, tocopherols, and fatty acids, known for their significant health benefits. Goat’s beard (Aruncus dioicus var. kamtschaticus), a wild leafy vegetable native to Ulleungdo Island, South Korea, is reported to possess various biological activities and bioactive compounds. However, the content and profiles of lipophilic metabolites, especially carotenoids, have not been reported. This study investigated the composition of lipophilic metabolites in the foliage of goat’s beard using liquid chromatography–diode-array detection–mass spectrometry, gas chromatography–mass spectrometry, and gas chromatography–flame ionization detection. Five carotenoids (violaxanthin, neoxanthin, lactucaxanthin, lutein, β-carotene) and α-tocopherol were identified and quantified using liquid chromatography–diode-array detection–mass spectrometry. Lactucaxanthin, previously discovered in lettuce, was identified for the first time in goat’s beard foliage, with a higher concentration (45.42 ± 0.80 µg/g FW) compared to red lettuce (19.05 ± 0.67 µg/g FW). Furthermore, total carotenoids and α-tocopherol contents were higher in goat’s beard than in red lettuce. Gas chromatography–mass spectrometry analysis showed the presence of three phytosterols, namely, campesterol (3.53 ± 0.20 µg/g FW), stigmasterol (65.30 ± 4.87 µg/g FW), and β-sitosterol (89.54 ± 2.46 µg/g FW). Gas chromatography–flame ionization detection analysis revealed the presence of five essential fatty acids, with α-linolenic acid (57.03 ± 0.47%) being the most abundant, contributing to a favorable polyunsaturated FA/saturated FA ratio. These findings underscore the nutritional potential of a goat’s beard, suggesting its promising use in dietary supplements and the commercial extraction of valuable lipophilic antioxidants, particularly lactucaxanthin, for nutraceuticals and functional foods.

Data and early results from temporary seismic arrays for monitoring and investigating magmatic processes beneath Mt. Halla and Ulleung Island volcanoes, South Korea

Data and early results from temporary seismic arrays for monitoring and investigating magmatic processes beneath Mt. Halla and Ulleung Island volcanoes, South Korea

Implication of Nari Caldera structure of Ulleung Island from a 3-D resistivity model using magnetotellurics

Implication of Nari Caldera structure of Ulleung Island from a 3-D resistivity model using magnetotellurics

Complete chloroplast genome of Saxifraga fortunei var. pilosissima (Saxifragaceae) endemic to Ulleung-do island, Korea

The Saxifraga fortunei var. pilosissima Nakai is an endemic species to Ulleung-do island. Here we report the complete chloroplast genome sequence of S. fortunei var. pilosissima, which was 151,186 bp in total length with the large single copy (LSC) region of 83,536 bp, the small single copy (SSC) region of 17,644 bp, and two inverted repeat (IR) regions of 25,003 bp. The chloroplast genome contained 131 genes, including 86 protein-coding, 37 tRNA, 8 rRNA genes, and GC (guanine-cytosine) content was 37.8%. Additionally, we found that the chloroplast genome of S. fortunei var. pilosissima exhibited intron loss in the rpl2 gene. Within the IR region, six protein-coding genes, seven tRNA genes, and four rRNA genes were duplicated. In the chloroplast genome of S. fortunei var. pilosissima, there are a total of 17 genes containing introns. Among them, 15 genes contain one intron each, while two genes contain two introns. Phylogenetic analysis based on 37 representative chloroplast genomes of the Saxifragaceae suggested that genus Saxifraga is monophyletic and S. fortunei var. pilosissima is placed in sect. Irregulares Haw. and grouped with S. fortunei, S. rufescens, and S. stolonifera with a strong maximum likelihood bootstrap support value.

Submarine volcanic microbiota record three volcano-induced tsunamis

The precise determination of sediment provenance not only yields insights into past tsunami events but also offers a window into understanding the genesis of tsunamis in distinct environments, such as volcanic regions. Through meticulous analysis of core samples from a lagoon in east of Korea Peninsula, we unveil three previously undocumented tsunamis and identify specific bacterial taxa associated with submarine volcanism during distinct periods. Specific bacterial species (Sulfurimonas_f and Alicyclobacillus ferrooxydans) and the presence of the silicoflagellate Dictyocha byronalis indicate deep-sea volcanic origins for certain sediment layers. The presence of microfossils, typically found in high-salinity pelagic environments during Event I, strongly supports the occurrence of a tsunami. These findings align with heightened volcanic activity on Ulleung Island during Event I and provide valuable chronological insights into submarine volcanic processes near Ulleung Island for Events II and III. Our study highlights these biological markers as crucial indicator for understanding past tsunamis arising from volcanic activity.

Seed Dormancy Class and Germination Characteristics of Berberis amurensis var. latifolia Nakai, Native to Korea

Berberis amurensis var. latifolia Nakai is a plant native to the Ulleung Island in Korea. In this study, we aimed to identify seed dormancy-breaking and germination requirements of this species using water imbibition experiments, gibberellic acid (GA3) treatment (0, 10, 100, or 1000 mg/L), cold stratification (0, 2, 4, 8, or 12 weeks at 5 °C), move-along experiments, and phenological studies. In the water imbibition experiment, the seed weight increased by more than 120% after 24 h. Analysis of the internal morphological characteristics of the seeds revealed that the embryo in freshly matured seeds was fully grown and did not grow thereafter. The final germination percentages after 12 weeks of cold stratification at 5 °C were 49 ± 6.4% and 63 ± 3.4% under light and dark conditions, respectively. In move-along and phenological studies, a longer cold stratification treatment period resulted in a higher germination percentage; however, the warm stratification treatment did not affect germination significantly. The GA3 treatment had little effect on seed germination. Therefore, we concluded that B. amurensis var. latifolia seeds have intermediate physiological dormancy, and pre-treatment with cold stratification for 12 weeks and incubation in the dark are required for effective seed propagation.

An Integrative Study of Scrophularia takesimensis Nakai in an Ovalbumin-Induced Murine Model of Asthma: The Effect on T Helper 2 Cell Activation.

Scrophularia have traditionally been used as herbal medicines to treat neuritis, sore throats, and laryngitis. In particular, S. takesimensis, a Korean endemic species with restricted distribution on Ulleung Island, holds significant resource and genetic value. However, its pharmacological properties have not been thoroughly evaluated. Thus, we provide detailed morphological characteristics and genomic information for S. takesimensis in this study. Moreover, its pharmacological activity was evaluated in an ovalbumin-induced asthma rat model, using extracts of S. takesimensis roots (100 or 200 mg/kg). The distinguishing features of S. takesimensis from related species include the presence or absence of stem wings, leaf shape, and habitat. The chloroplast (cp) genome of this species is 152,420 bp long and exhibits a conserved quadripartite structure. A total of 114 genes were identified, which included 80 protein-coding genes, 30 transfer RNA (tRNA) genes, and 4 ribosomal RNA (rRNA) genes. The gene order, content, and orientation of the S. takesimensis cp genome was highly conserved and consistent with the general structure observed in S. buergeriana and S. ningpoensis cp genomes. Confirming the anti-inflammatory effects of S. takesimensis extract (STE) using an established mouse model of ovalbumin-induced asthma, we observed reduced asthmatic phenotypes, including inflammatory cell infiltration, mucus production, and suppression of T helper 2 (Th2) cell. Furthermore, STE treatment reduced Th2 cell activation and differentiation. This study underscores the medicinal value of S. takesimensis. The importance of preserving S. takesimensis was revealed and crucial insights were provided for further research on its utilization as a medicinal resource.

Wasabi Gone Wild? Origin and Characterization of the Complete Plastomes of Ulleung Island Wasabi (Eutrema japonicum; Brassicaceae) and Other Cultivars in Korea.

Korean wasabi occurs naturally on the young oceanic, volcanic Ulleung Island off the east coast of the Korean Peninsula. Although the Ulleung Island wasabi is reported as Eutrema japonicum and has been suggested to be morphologically identical to cultivars in Korea, very little is known about its taxonomic identity and relationship with other cultivars. In this study, we sequenced the complete chloroplast DNA sequences of three naturally occurring Ulleung Island wasabi plants and six cultivars ('Daewang', 'Daruma', 'Micado', 'Orochi', 'Green Thumb', and 'Shogun') from continental Korea and determined the taxonomic identity of Korean wasabi on Ulleung Island. The size and organization of the complete chloroplast genomes of the nine accessions were nearly identical to those of previously reported wasabi cultivars. In addition, phylogenetic analysis based on the complete plastomes suggested that Ulleung Island wasabi most likely comprises various wasabi cultivars with three chlorotypes ('Shogun', 'Green Thumb', and a unique Chusan type). Based on the complete plastomes, we identified eight chlorotypes for the major wasabi cultivars and the Ulleung Island wasabi. Two major groups (1-'Mazuma' and 'Daruma', and 2-'Fujidaruma'/'Shimane No. 3'/Ulleung Island wasabi/five cultivars in Korea) were also identified based on mother line genealogical history. Furthermore, different types of variations (mutations, insertions/deletions (indels), mononucleotide repeats, and inversions) in plastomes were identified to distinguish different cultivar lines and five highly divergent hotspots. The nine newly obtained complete plastomes are valuable organelle genomic resources for species identification and infraspecific phylogeographic studies on wild and cultivated wasabi.

Microstructural and microchemical analysis of zircon in a syenite lithic fragment from Ulleung Island volcano, South Korea

Abstract Background The intricate textural patterns commonly observed in metamorphosed and recrystallized zircon (ZrSiO4) underscore the crucial necessity of understanding the underlying mechanisms governing their formation to ensure accurate interpretation of the chemical and isotope data they contain. This study employed a combination of microanalytical techniques, including electron backscattered diffraction (EBSD) analysis, electron microprobe (EMP) mapping, and scanning electron microscope (SEM) imaging, to investigate the processes of formation and modification of zircon in a late Pleistocene (~ 35 ka) syenite enclosed within the Nari Tephra Formation on Ulleung Island in South Korea. Findings Under cathodoluminescence (CL), zircons within the syenite reveal dark, featureless, or oscillatory-zoned cores containing numerous inclusions of britholite. These cores are partially or entirely replaced by inward-penetrating bright-CL domains that exhibit minimal inclusion presence. Despite these changes, the external morphologies of the zircons remain largely unchanged, and the faded oscillatory zoning is preserved in the replaced regions. EMP mapping discloses amoebiform micro-domains with high Y, U, and Th concentrations within the dark-CL cores, while the bright-CL domains are relatively deficient in these trace elements. Microstructural analysis of the zircons using EBSD mapping indicates no significant misorientation between the dark-CL cores and the bright-CL rims. Deformation-related low-angle boundaries by lattice distortion are clearly observed in certain grains, cutting across the discrete SEM and EMP domains, and often aligned along submicron pore trails. Conclusions Microstructural and microchemical analyses carried out in this study establish that the zircons within the Ulleung syenite have undergone subsolidus recrystallization, a process likely influenced by the presence of fresh melts or fluids. This recrystallization process could be attributed to either coupled dissolution and reprecipitation or thermoactivated particle and defect volume diffusion due to inherent lattice strain. The subsequent deformation observed in the zircons might be a result of increased stress within the magma system after the recrystallization.

Eddy-driven sea-level rise near the frontal region off the east coast of the Korean peninsula during 1993–2020

IntroductionUnderstanding the underlying dynamics of regional sea-level rise (SLR), which often deviates from global trends, is crucial for mitigating and adapting to the impacts of severe climate change. This study investigated the causes of high regional SLR rates (> 6.0 mm yr-1) around the frontal region near Ulleung Island in the southwestern East/Japan Sea (EJS). Despite exhibiting rates higher than the global average (3.1 mm yr-1) from 1993 to 2020, the reasons for these higher rates in this region have not been clearly elucidated.MethodsWe aimed to clarify the quantitative effect of the long-term variations of the Ulleung Warm Eddy (UWE) on the high SLR rates near Ulleung Island based on satellite altimetry and ship-based hydrographic data.ResultsDuring this period, the temperature within the UWE increased, particularly at the temperature-homogeneous layer of approximately 200 m, the lower boundary of the UWE deepened, and the eddy duration per year increased, resulting in high SLR rates within the eddy owing to the steric height rise. The long-term variations in the internal temperature and vertical thickness of the UWE had significantly comparable impacts on SLR rates, with the duration being less influential. The SLR rates by integrating all long-term variations in the UWE (7.6 mm yr-1) quantitatively explained the high long-term SLR rates at Ulleung Island (7.0 mm yr-1).DiscussionThe increasing temperature within the UWE was attributed to the rising temperature of water flowing through the southwestern strait (Korean Strait) in late fall, and the deepening lower boundary and the increasing duration of the UWE resulted from the increased horizontal temperature gradients near the front, leading to enhanced baroclinic instability in the subsurface layers. Our findings suggest that long-term variations in mesoscale eddies can significantly influence the regional SLR rates, deviating substantially from the global average in the frontal region.

Dimorphostylispilocorpus sp. nov. (Crustacea, Cumacea, Diastylidae), a new cumacean from Korean waters.

A new species of Cumacea belonging to the genus Dimorphostylis Zimmer was collected from the Dokdo and Ulleung Islands in the East Sea of Korea. The new species, Dimorphostylispilocorpussp. nov., can be distinguished from all other Dimorphostylis species by the combination of the body surface covered with numerous slender simple setae; carapace with one transverse, a pair of frontal, and three pairs of oblique ridges; three pairs of oblique ridges connected on a submedian carina; telson of the female with 1 pair of short simple and 1 short, stout simple seta centrally; 1 pair of stout simple and 3 pairs of short simple setae on the post-anal section; pleonite 5 of male with 1 spiniform seta on the ventral margin; post-anal section with 2 pairs of stout simple setae bearing a single subterminal setule on both sides; terminal margin with 3 stout simple setae; and a central seta slightly longer than the outer pair of setae. Full illustrations of the new species, including the mouthparts, are given in this paper. A key to the Korean species of Dimorphostylis is also provided.

A new variety of Rubus (Rosaceae): Rubus takesimensis var. flavus

A new variety of Rubus, Rubus takesimensis Nakai var. flavus J. O. Hyun & B. T. Jang (Rosaceae), was discovered on Ulleungdo Island, Korea. This variety is different as it has yellow fruits and yellow-green branchlets and leaves compared to Rubus takesimensis var. takesimensis.

Carex chromosome numbers from Korean populations (eight taxa)

Carex L. is the most species-rich genus in Korean flora (ca. 180 taxa) as well as worldwide (more than 2,000 species). One of the hypotheses explaining high species diversity in the genus is holocentric chromosomes, which miss constricted centromeres during cell divisions; chromosome fission and fusion events are possible. To provide fundamental biological information, we report the meiotic chromosomes of eight Carex taxa investigated from twelve populations, which include four Ulleung-do Island (oceanic island) populations. The taxa and chromosome numbers observed were C. augustinawiczkii (n = 27<sub>II</sub>), C. bostrychostigma (n = 22<sub>II</sub>), C. egena (n = 25<sub>II</sub>), C. fusanensis (n = 21<sub>II</sub>), C. japonica (n = 31<sub>II</sub>, 32<sub>II</sub>), C. maackii (n = 37 II ), C. mollicula (n = 32<sub>II</sub>), and C. pediformis var. pedunculata (n = 36<sub>II</sub>). Chromosome numbers of C. augustinawiczkii, C. egena, C. fusanensis (a Korean endemic), and C. pediformis var. pedunculata are revealed for the first time. C. japonica from Ulleung-do Island populations exhibits two chromosome numbers, which differ from the chromosome numbers reported from the Korean mainland (peninsula). More chromosome data are required to understand Carex species diversity in Korean flora.

Long-lived shallow crustal magma reservoirs beneath Ulleung Island volcano (South Korea) and their rejuvenation recorded in zircon

The microanalytical data obtained from zircons collected on Ulleung Island, an emergent peak of a Quaternary alkaline magma system in the southwestern East Sea (Sea of Japan) back-arc basin, provide new insights into the origin of magma, magmatic processes, and the trigger of explosive eruptions. The U-Th ages of zircons extracted from a pumice layer formed during the intense Plinian eruption at ∼11 ka, known as the Ulleung-Oki tephra, show a wide range spanning the pre-eruption equilibrium state (>350 ka) up to the eruption event itself. Zircon grains derived from syenite and gabbro fragments entrained within the tephra yield weighted mean U-Th and U-Pb ages of 34.7 ± 2.3 ka and 1378 ± 22 ka, respectively. Under cathodoluminescence, zircons from the syenite reveal dark, featureless, or oscillatory-zoned cores, containing numerous inclusions of britholite-like Y-rich phases and pyrochlore. These cores are partially or entirely replaced by inclusion-free, brighter domains, suggesting that in situ dissolution and precipitation processes significantly influenced the transformation of zircon. The consistently low δ18O values (5.4–2.6‰) of zircons from Middle Pleistocene trachyte lavas, the Ulleung-Oki tephra, and lithic fragments indicate the persistent presence of shallow crustal magma reservoirs beneath Ulleung Island. These reservoirs have undergone substantial assimilation of hydrothermally altered rocks, with assimilation rates typically around 10–30% and reaching a maximum of approximately 50%. Zircon core-to-rim variations in oxygen isotopic composition, along with textural observations, suggest the rejuvenation of magma reservoirs through the injection of new melt, which likely served as a trigger for the explosive eruptions at Ulleung Island. The similarity in the range of εHf values between the core and rim (+7.4 to −4.3) implies the Hf isotopic consistency of the recharge melt.

Zircon U–Pb ages and O–Hf isotopes of Quaternary trachytes from the East Sea: Implications for the genesis of low-δ18O magmas

Quaternary intraplate magmatism formed several volcanic islands and seamounts, including Dokdo (DD), Ulleungdo (UD), Simheungtack (ST), Anyongbok, and Isabu in the southwest of the East Sea back-arc basin. In this study, we present whole-rock geochemical, zircon U–Pb age, and in situ O–Hf isotope data for the submerged volcanic rocks from DD, UD, and ST to provide new insights into the eruption timing of these volcanoes and constrain the magma evolution processes. All samples used in this study were trachytes and exhibited ferroan, alkalic, and metaluminous to weakly peraluminous characteristics. They showed light rare earth element (REE)-enriched patterns with (La/Yb)N ratios of 25.3–31.7 and mostly negative Eu anomalies in a chondrite-normalized REE plot. In addition, they were enriched in large-ion lithophile elements and high field strength elements; they exhibited positive Pb anomalies and strongly negative Ba, Sr, P, and Ti anomalies. The zircons yielded a weighted-mean 206Pb/238U age of 2.61, 0.348–0.704, and 2.76–2.94 Ma for the DD, UD, and ST trachytes, respectively. All zircons exhibited lower δ18O values than normal depleted mantle values, regardless of the crystallization age and spatial distribution of volcanoes. The δ18O values showed no correlation with U contents or Th/U ratios, indicating that the low δ18O signatures were of primary magmatic origin. The Hf isotopic compositions of the zircons were relatively heterogeneous but predominately characterized by positive εHf values. Binary O–Hf mixing modeling revealed that low-δ18O rocks with positive εHf values from the UD and ST volcanoes were derived from a hybrid source of recycled juvenile crustal materials with low-δ18O and positive εHf signatures and an enriched mantle source with normal δ18O and negative εHf values. The juvenile oceanic crust in the source was likely metasomatized by seawater at high temperatures prior to melting. In contrast, the felsic magma that formed the DD volcanoes may have assimilated with regional basement rocks (Triassic–Jurassic granitoids), resulting in increased δ18O values and decreased εHf values relative to those of the UD and ST volcanoes. Our study highlights the significant contribution of recycled oceanic crust materials to the generation of the Quaternary magmas.

Dormancy-release and germination improvement of Korean bellflower (Campanula takesimana Nakai), a rare and endemic plant native to the Korean peninsula.

Korean bellflower (Campanula takesimana Nakai) is a rare and perennial herb with medicinal and ornamental values, is endemic to the Ulleung Island of Korea. In this study, we investigated the dormancy-release and germination characteristics of C. takesimana (Campanulaceae) seeds by subjecting them to varying temperatures (5, 10, 15, 20, and 25°C and diurnal/nocturnal temperatures of 15/6, 20/10, and 25/15°C), cold stratification periods (0, 4, 8, or 12 weeks at 5°C), and gibberellic acid (GA3) concentrations (0, 10, 100, or 1,000 mg·L-1 at 15/6°C and 25/15°C) to identify the ideal seed propagation conditions. The seeds were stimulated to germinate (at 25°C, 12-h photoperiod with fluorescent lamps at 40 ± 10 μmol∙m-2∙s-1) after cold stratification. To examine the germination characteristics, the seeds were tested for water imbibition and found to readily absorb water. The seeds exhibited underdeveloped embryos during dispersal, showed final germination of 37.00% ± 4.43 at 25°C and were not influenced by temperature. The seeds subjected to 0, 4, 8, or 12 weeks of cold stratification germinated at a success rate of 22.00% ± 4.76, 87.00% ± 6.80, 79.00% ± 2.52, and 77.00% ± 1.91, respectively. Additionally, the germination characteristics, which were based on final germination, mean germination time, and germination velocity (Timson index), were significantly greater in the seeds pretreated with 1,000 mg·L-1 GA3 at 25/15°C than in seeds pretreated with 0 mg·L-1 GA3. Overall, the seeds broke dormancy with GA3 and short-term cold stratification. Therefore, we concluded that C. takesimana seeds have non-deep, simple, morphophysiological dormancy, and pretreatment with cold stratification and GA3 is required for effective seed propagation.

Characteristics of STILT footprints driven by KIM model simulated meteorological fields: implication for developing near real-time footprints

This study presents an analysis of the atmospheric footprint sensitivities and CO2 enhancements measured at three in situ stations in South Korea (Anmyeondo (AMY), Gosan (JGS), Ulleungdo (ULD)) using the KIM-STILT and WRF-STILT atmospheric transport models. Monthly aggregated footprints for each station were compared between the models for July and December 2020. The footprints revealed major source regions and the sensitivity of atmospheric mole fractions at the receptor to upstream surface fluxes. In July, both models showed similar major source regions for the AMY station, including Korea, the Yellow Sea, and Japan. However, a discrepancy was observed in the Eastern Pacific Ocean, with KIM-STILT showing larger sensitivity compared to WRF-STILT. In December, both models indicated strong sensitivity over Northeast and Eastern China, but KIM-STILT exhibited smaller sensitivities towards Northwestern China and Mongolia compared to WRF-STILT. At station ULD in July, both models exhibited comparable source regions, but a notable difference was found in Southeast China, where KIM-STILT showed stronger sensitivity. For the JGS station, both models agreed on major sources, but WRF-STILT demonstrated stronger sensitivity over North and Northeastern China. Regarding CO2 enhancements, both models generally underestimated the amplitude of CO2 enhancements, especially in July. However, in December, there was better agreement with observed data. The models were able to reproduce the phase of measured ΔCO2 reasonably well despite the underestimation of CO2 amplitudes. The contribution of biospheric CO2 to the observed enhancements, along with fossil-fuel emissions, was highlighted. In specific cases with significant CO2 enhancements, the models provided varying estimates of CO2ff values, particularly in the source regions of Eastern China. The differences in sensitivity estimations emphasize the need for further investigation to understand the underlying factors causing disparities. Overall, this study provides valuable insights into the potential advantages of each model in capturing dispersion patterns in specific regions, highlighting the importance of understanding these differences to improve the accuracy of atmospheric transport models. Further work is necessary to address the observed disparities and enhance our understanding of the transport models in the studied regions.

Delineation of shallow volcanic structures from audio-frequency magnetotelluric data beneath Ulleung Island, East Sea (Sea of Japan)

As volcanoes are closely related to the living environment of humans, in particular via natural hazards and geothermal energy, scientific studies on volcanic edifice structures are required. Ulleung Island is a Quaternary volcanic island located in the mid-western East Sea (Sea of Japan). In this study, we conducted an audio-frequency magnetotelluric (AMT) survey to image the substructure of the Ulleung volcanic edifice. In addition, the electrical structure was interpreted from the geothermal system perspective, geochemical compositions of volcanic rocks, and the possibility of the presence of a magma reservoir. AMT data were obtained from 25 stations and processed using the remote reference technique. Then, the three-dimensional (3-D) approach was reasonably adopted according to dimensionality analysis. Before conducting the 3-D inversion, the effects on topography and ocean were analyzed using a simplified 3-D synthetic model, because Ulleung Island is surrounded by sea and the topography is undulating. Most AMT stations on Ulleung Island are distorted by topographical and oceanic effects; in particular, oceanic effects are significant at frequencies lower than 10 Hz. The 3-D inversion was conducted with full impedance components and vertical magnetic transfer functions in a frequency range of 10,000–1 Hz. The results show that the Ulleung volcanic edifice is characterized by two layers of electrical structures as follows: near-surface resistive anomalies and an underlying conductive layer. Considering the high geothermal gradient on Ulleung Island, we suggest that the conductive layer of the volcanic edifice is due to hydrothermal alteration of basaltic rocks, with a potential heat source underneath. Based on the geochemical characteristics of the Ulleung volcanic rocks, the possibility of heat transfer from a trachytic magma reservoir within the shallow crustal is suggested. In summary, this study presents a geological interpretation of shallow volcanic structures beneath Ulleung Island and the possibility of an active magma reservoir as a potential heat source for the volcanic edifice.Graphical