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David Glacier is a significant East Antarctic outlet glacier through the Transantarctic Mountains and into the western Ross Sea. The six active subglacial lakes (D1~D6) were identified in the David Glacier catchment based on NASA’s Ice, Cloud, and land Elevation Satellite (ICESat) laser altimeter dataset for 4.5 years (2003-2008). Since 2016, Korea Polar Research Institute (KOPRI) has been preparing the hot-water drilling project in the David Glacier, starting with the geophysical surveys. KOPRI’s geophysical research team confirmed the change rate of the surface elevation of the David glaciers based on the analysis of the Double-Differential Interferometric synthetic aperture radar (DDinSAR) from satellite (Sentinel-1A) images for July to August 2015 and March 2017, then selected the D2 subglacial lake as the target for the potential hot-water drilling project. KOPRI’s Antarctic traverse team developed ground routes for logistics from the JBS to the D2 lake site in the 2017-18 season. In the 2018-19 season, a radar survey was conducted on the D2 site, and the lake's global structures and scale were confirmed. Then, in the 2021-2022 season, a multi-channel seismic survey was conducted on the D2 site to image the detailed subglacial structures of the lake. The final goal of this seismic survey is to get information on the optimal site selection for the hot-water-drilling location for subglacial sampling. The seismic survey was performed for about two months on the ice. Dynamite is used to generating the seismic source; 1.6 kg of dynamites were used per the charging hole. The charging depth is 25 m. 90 m and 180 m shot intervals were used for 8- and 4-fold data acquisition. Four sets of the Geometric Geode and a 96-channel GEOROD system were employed to record the seismic signal from the ice. The group spacing of the receiver (GEOROD) is 15 m. The seismic data were recorded for 4 seconds with two milliseconds sampling rates. The total length of the acquired seismic data is 17.2 km, consisting of 4 survey lines: two south-to-north and two east-to-west lines. The maximum and minimum fold numbers are 8 and 4, respectively. We got high-quality seismic migrated images containing actual structural and geophysical information about the subglacial lake through seismic data processing with advanced denoise and de-ghosting algorithms. We confirmed the thickness of the ice, which can estimate by the depth of the reversed-polarity reflections on the boundaries between the ice and lake water from the migrated seismic sections for each survey line for D2 lake. Also, the 200 m lake water depth, structures, and geophysical characteristics of the subglacial lake were confirmed, and then, we found the optimal hot-water drilling location for the subglacial lake D2 in the David Glacier, Antarctica.

The rising temperature in the Arctic changes marine environments such as sea ice fluctuation, primary production, and riverine input and these changes, in turn, impact on benthic ecosystems. East Siberian Sea (ESS) represents shallow shelf seas with three to seven times higher river discharge than other seas of Russian Arctic. However, studies on the microbial composition and functions according to the environmental parameters have not been performed in the ESS. In this study, the benthic microbial community structure with the environmental parameters and their ecological functions were investigated. Bacterial community was dominated by the phyla Proteobacteia (51.1±6.6%) followed by Bacteroidetes (16.4±9.5%), Planctomycetes (8.9±3.8%), Acidobacteria (6.5±4.2%), Actinobacteria (2.6±2.0%). In the archaeal community, Thaumarchaeota (70.9±11.1%) and Euryarchaeota (27.7±11.4%) were predominant. There are some microbial taxa showing significant changing pattern along the latitude. The proportion of Alphaproteobacteria and Acidobacteria increased while that of Bacteroidetes and Deltaproteobacteria and Thaumarchaeota decreased along the latitude. Microbial community composition and function of major taxa were clearly differentiated according to the latitude and concurrent environmental parameters such as salinity and concentration of ammonium and sulfate. In addition, the function of major microbial taxa including ammonium oxidation and sulfate reduction inferred from 16S rRNA identity also changed across the salinity gradient. These results imply that environmental changes in the benthic ecosystems accelerated from the climate change may impact a significant change on benthic microbial community composition and their functions.

Gas hydrates are known to be an enormous potential energy resource that are accumulated worldwide, especially in the polar regions, and yet the estimates for this resource remain uncertain. In the Arctic region, methane emissions into the atmosphere are a substantial factor in global warming that poses a great danger to the environment. Previously, several studies have been conducted to estimate the gas hydrates in the Arctic to ease such problems despite the need for more data compared to conventional reserves. In the western continental margin of the Chukchi Plateau, the sea mound morphologies were first discovered, and gas hydrate samples were obtained via gravity coring during the first expedition in 2016. In the following expedition in 2018, an intensive gas hydrate exploration including the single-channel seismic survey was conducted in the area of mound morphologies and identified the local bottom simulating reflectors. Consequently, an extensive multichannel seismic survey was conducted in 2019 to investigate the geophysical characteristics of widely distributed gas hydrates in the western continental margin of the Chukchi Plateau. The objective of this study is to estimate the potential volume of gas hydrate resources in the Chukchi Plateau based on the geophysical data. From this study, the distribution of bottom-simulating reflectors and local gas hydrate saturations were derived from the geophysical data. The gas hydrate saturation model in this study area was constructed using the kriging method with few geological assumptions. Then, the total volume of gas hydrates in the western continental margin of the Chukchi Plateau was proposed. The results of this study will provide basic information on the estimates of gas hydrates in the western continental margin of the Chukchi Plateau and contribute to assessing the size of the associated volume of methane emissions due to global warming.

The East Siberian Sea is known for its high methane emissions, and the extent of massive methane emissions in remote areas from the coast is considered an important factor in estimating total methane emissions in the Arctic Ocean. In 2021, a multidisciplinary survey was conducted on the continental shelf of the East Siberian Sea aboard the Korean icebreaker Araon. The area is in international waters and is located more than 500 km from the coast. We conducted high-resolution sparker seismic survey and sub-bottom profiling to find detailed geological structure for gas expulsion and high-frequency echo sounding using EK80 to detect gas bubbles in water column EK80. We also measured underway CH4 concentration and sampled water and sediment with CTD and a multi corer. A high methane-concentration zone was found on the very shallow continental shelf at depths of 50–70 m by the underway CH4 measurements. It is developed in a northwest-southeast direction and has a width of several kilometers in the northwest and about 50 kilometers in the southeast. Because thick sea ice remained in the southeast zone, we have to surveye in the northwest zone. During the survey, many gas flares in the echograms and gas bubbles on the sea surface were found. In the gas flare field, we conducted extensive experiments with CTDs and sediment sampling using a multi-corer. A single channel sparker seismic survey was conducted crossing the high concentration zone with a source of 3000–5000 J. The acquired data were processed to get migration section and seismic profiles show well-stratified sedimentary layers clearly. On the gas expulsion sites, the seismic profiles show many vertical faults in the shallow sedimentary layers and vertical reflections in the water column caused by the methane emission from the seafloor. Acoustic features related to gas expulsion and gas charged sediments were also observed in the SBP data. Narrow and vertical reflections are also observed in the water column above the seafloor and the location of these reflections corresponds with the edge of the high amplitude, undulated subsurface reflector at shallow depths (~5 m) below the seafloor.

Climate change in the Arctic has recently become a major scientific issue, and detailed information on the degradation of subsea permafrost on continental shelves in the Arctic is critical for understanding the major cause and effects of global warming, especially the release of greenhouse gases. The subsea permafrost at shallow depths beneath the Arctic continental shelves has significantly higher P‐wave velocities than the surrounding sediments. The distribution of subsea permafrost on Arctic continental shelves has been studied since the 1970s using seismic refraction methods. With seismic refraction data, the seismic velocity and the depth of the upper boundary of subsea permafrost can be determined. However, it is difficult to identify the lower boundary and the internal shape of permafrost. Here, we present two‐dimensional P‐wave velocity models of the continental shelf in the Beaufort Sea by applying the Laplace‐domain full‐waveform inversion method to acquired multichannel seismic reflection data. With the inverted P‐wave velocity model, we identify anomalous high seismic velocities that originated from the subsea permafrost. Information on the two‐dimensional distribution of subsea permafrost on the Arctic continental shelf area, including the upper and lower bounds of subsea permafrost, are presented. Also, the two‐dimensional P‐wave velocity model allows us to estimate the thawing pattern and the shape of subsea permafrost structures. Our proposed P‐wave velocity models were verified by comparison with the previous distribution map of subsea permafrost from seismic refraction analyses, geothermal modeling, and well‐log data.

The Arctic MArine Geoscience Expedition (AMAGE) program led by the Korea Polar Research Institute (KOPRI) is a multidisciplinary undertaking to investigate the geological environment and methane release phenomena in the Arctic seas. The icebreaking research vessel (IBRV) Araon has carried out three expeditions in the Chukchi Plateau (CP) and the East Siberian Seas in 2016, 2018 and 2019. In the first 2016 expedition, a chain of topographic mounds (with the height of several tens meters and the width of hundreds meters) was identified by subbottom profiler and multibeam bathymetric survey in the western continental slope of the CP. Gas hydrate samples were first retrieved in the Araon Mound-6 among the mound structures in the CP and ESS areas during the expedition. The detailed morphology and subsurface structures of the mounds were mapped from the subsequent expeditions in 2018 and 2019. More gas hydrate samples were obtained in the Araon Mound-3 and Araon Mound-6 in these expeditions. To examine gas hydrate occurrence conditions, we conducted geophysical surveys including seismic (sparker in 2018 and multi-channel in 2019) and heat flow methods during these expeditions. The seismic profiles obtained using two seismic methods show very well-developed bottom simulating reflectors (BSRs) which are widespread on the western slope of the study area. The BSR depths detected on the seismic profiles are well coincided with the depths of the lower boundary of the gas hydrate stability zone calculated from the geothermal gradient of heat flow measurement.Arctic gas hydrates are considered to be vulnerable to the ongoing rapid Arctic warming. The AMAGE program will provide comprehensive understanding on poorly-known gas hydrate in the Arctic in the various research fields of geology, geophysics, geochemistry, biogeoscience, and oceanography.

Much attention has recently been paid to the East Sea because of the great influence it exerts on weather in the Korean peninsula as well as its peculiar oceanographic features. A large number of oceanographic observations have been made to probe the physical properties of the waters at the East Sea. However, until now, measuring the physical properties of a broad oceanic area simultaneously was impractical. To address this problem, this study presents a methodology to measure the physical properties of seawater by introducing seismic oceanography (SO) into marine seismic surveys. SO has been attracting attention as a new technology capable of concurrent analysis of a broad oceanic area; however, hardly any research of this type has been conducted in Korea to date. The technique proposed in this study involves derivation of a seawater temperature model based on the 1D seismic waveform inversion and Leroy equations using seismic data and non-stationary ARGO data. The proposed technique was validated throug...