Jong Kuk Hong

The widespread presence of submarine permafrost in the southern Canadian Beaufort Sea provides necessary stability conditions for gas hydrates on the shallow shelf. However, the submarine permafrost is still relatively underexplored. Representing mostly relict terrestrial permafrost, submarine permafrost was formed by subaerial exposure to ∼−20°C in the Pliocene and Pleistocene. With the end of the last glaciation, the former terrestrial permafrost became inundated as a result of a marine transgression that caused a significant change in thermal conditions. The submarine permafrost is still responding to this thermal change and continues to degrade. The degradation of permafrost can cause greenhouse gas emissions having an important impact on the global climate. In this study, we use marine multichannel seismic data to calculate the base of permafrost using the seismically detected base of the gas hydrate stability zone. From the depth of the base of the gas hydrate stability zone, we estimate the theoretical gas hydrate dissociation temperature, which allows us to calculate the depth of the remotely inaccessible thermal base of permafrost (0°C isotherm). This calculated base of permafrost correlates with the lower boundary of a diffuse zone of high diffraction strength in seismic data indicating the presence of ice‐bearing permafrost. Our study provides a new approach to access the current depth and extent of submarine permafrost on the outermost Canadian Beaufort Shelf and indicates less thawing of permafrost than previously thought.

We present a comprehensive seismic characterization of the gas hydrate system in the outer continental shelf of the Mackenzie Trough, Canadian Beaufort Sea, based on recently acquired multichannel seismic (MCS) data, P‐wave velocity modeling, and 3D thermal modeling. We identified high‐amplitude, reverse‐polarity Bottom‐Simulating Reflections (BSRs) over an area of ∼406 km ² , marking the base of the gas hydrate stability zone (GHSZ). Iterative migration velocity analysis reveals high‐velocity zones (2.0–2.5 km/s) indicative of hydrate‐bearing sediments overlying low‐velocity free gas (1.0–1.6 km/s). Effective‐medium modeling indicates gas hydrate saturations of 12%–67% of pore space, with maxima near the shelf break, and free‐gas saturations of up to 9%. Combined, these estimates yield a potential methane mass of approximately 0.17–0.23 Gt within the Trough. By integrating a 3D heat flow model constrained by local ocean temperatures, we find that the theoretical base of the GHSZ closely matches observed BSR depths, except in the western sector where BSRs are 40–60 m deeper than the modeled GHSZ. This discrepancy implies that the gas hydrate system in the Mackenzie Trough exhibits localized disequilibrium. Furthermore, these findings suggest that the extensive deep‐marine gas hydrate province and its associated localized thermodynamic disequilibrium, documented off the US Alaska margin, may extend eastward to the Mackenzie Trough, which may represent the easternmost documented occurrence along the US‐Canadian Beaufort margin. While this deep hydrate system is unlikely to be undergoing destabilization from recent ocean warming, sustained long‐term climate forcing may pose a latent risk for future gas hydrate dissociation.

A multipronged, 12-year study has revealed a complex, submarine morphology dotted with pingos which are continually changing due to ongoing freezing and thawing of brackish groundwater seeping up from buried ancient permafrost. Multibeam mapping surveys on both sides of the Mackenzie Trough in the Canadian Beaufort Sea were repeated in 2025, 8 and 12 years after the initial mapping surveys. Differencing 1-m-scale bathymetry grids collected using Autonomous Underwater Vehicles reveals the tops of pingos experience up to 1.5 m of upwards growth between surveys, documenting of upwards growth approaching 20 cm per year of submarine pingos for the first time. Up to 5 m of down drops were also observed on the crest of some submarine pingos. Areas that experience 1.5 m of growth are less than 10 m from areas that experienced 2.0 m of down drops. Remotely Operated Vehicle (ROV) based low altitude surveys using stereo cameras, multibeam, a laser scanner, and vision-based Simultaneous Localization and Mapping navigation mapped sections of this dynamic morphology at sub-cm resolution providing extraordinary detail on the on-going seafloor deformation associated with submarine permafrost. An ice layer exposed in the wall of an

To facilitate geological studies of the Antarctic region south of 60°S, equivalent point magnetic dipole inversion was used to produce the comprehensive airborne‐to‐satellite altitude ADMAP‐2s magnetic anomaly model. These spherical coordinate anomaly predictions jointly match the crustal magnetic anomalies gridded at 250 km above the Earth's mean geocentric radius (mgr) from the magnetometer observations of the Swarm satellite mission and at the mgr from the Antarctic Digital Magnetic Anomaly Project’s (ADMAP) second‐generation magnetic anomaly compilation (ADMAP‐2) of over 3.5 million line‐km of aeromagnetic and shipborne survey data. The present study investigates the utility of point dipole modeling for differentially reducing the magnetic anomalies to the pole and estimating their first and second order radial (i.e., locally vertical) derivative anomalies. Where sufficiently accurate, these radially polarized magnetic anomalies and gradients help constrain the possible depths and lateral limits of the crustal magnetic anomaly sources for Antarctica and the circumjacent southern Atlantic, Indian, and Pacific oceans. For East Antarctica, the anomalies help resolve relatively ancient cratonic boundaries and related sutures and magmatic intrusions, whereas at satellite altitude, they also offer insights on variations of lithospheric heat flow.

Submarine permafrost in the Canadian Beaufort Sea is relict terrestrial permafrost, which is continuously degrading since the change of thermal conditions induced by a marine transgression that followed the last glaciation. Permafrost degradation has a crucial socio‐ecological significance because its thawing can result in geohazards like landslides or an increase in greenhouse gas emissions. These consequences are mostly regulated by the state of ice in permafrost. In this study, we use marine multichannel seismic data to apply a diving wave tomographic inversion on the outer 50 km of the Canadian Beaufort Shelf. Due to the close relationship between seismic velocity and ice content, we are able to infer detailed information about the present submarine permafrost condition. We find a clear variability of permafrost occurrences between the inner and outer Canadian Beaufort Shelf. At the inner shelf, discontinuous ice‐bonding permafrost occurs extensively close to the seafloor but is interrupted by taliks. Within the outer ∼27 km of the shelf, ice‐bonding permafrost is absent in the upper sediments and its top has plunged to >200 m below sea level. These findings add new details to the current state of the degrading permafrost. In addition, we observe seismic anisotropy in the frozen permafrost sediments.

Permafrost extends offshore in the Arctic as submarine permafrost. Near the edge of stable, continuous permafrost offshore, fresh groundwater flux contributes to regions of actively deforming thermokarst. Large-magnitude (up to ~30 m) sinkholes have been observed to form over less than a decade, posing a significant threat to offshore infrastructure. Additionally, having recently been discovered in sub-Arctic environments, thermokarst formation may be possible in a wider range of conditions than previously thought. It is critical to understand the evolution of degrading submarine permafrost, thermokarst, and the critical parameters necessary to predict the locations and magnitudes of seabed impacts.We present acoustic sub-bottom profile (3.5 kHz Chirp) data collected in the Canadian Beaufort Sea, highlighting observations just offshore of a well-studied, actively deforming thermokarst field near the shelf edge. We map a seismic horizon that marks the top of ice-bearing sediment in the active thermokarst region; seaward, this horizon becomes a choppy unconformity punctuated by low-amplitude reflections that we interpret as fluid escape pathways. Beneath this horizon, an acoustically transparent layer persists seaward until characteristically and abruptly gaining coherent layering. We map the seaward edge of the acoustically transparent layer and interpret it as paleothermokarst. Laminated shallow seismic stratigraphy and a deep continuous acoustic basement surface are also characteristic of the interpreted paleothermokarst zone and absent from active thermokarst regions. The seaward edge of interpreted paleothermokarst has remarkably consistent seafloor depths at our mapped crossings (-372 m ± 34 m), suggesting an influence of depth-related processes controlling this edge. Lowstand sea level (-120 m) and potentially colder bottom-water temperatures may have allowed lowstand thermokarst to form ~187 m deeper than the thermokarst along the Canadian Beaufort margin today (which has seaward edge depths of -185 m ± 24 m). We suggest that the locus of active thermokarst (de)formation has moved landward over time in response to rising sea level, and expect the most active deformation at the landward edge of the thermokarst field.

The Chukchi Basin, a sub-basin of the Amerasia Basin in the Arctic Ocean, remains enigmatic regarding its formation age and tectonic processes. Among the various hypotheses proposed, seafloor spreading or hyper-extended rifting during the Cretaceous are currently prominent, both supported by gravity and deep seismic survey data. Recent marine heat flow (MHF) observation efforts using the IBRV Araon from 2018 to 2024 have resulted in a comprehensive dataset covering the basin along and across the inferred N-S oriented spreading axis in the basin center. The formation age inferred from the newly observed MHF was the Early to Late Cretaceous, which is slightly older than the timing of Northwind Basin to the east. Notably, the MHF distribution revealed an asymmetric increase toward the eastern margin perpendicular to the axis and toward to southern margin parallel to the axis. Because MHF distribution often reflects deep tectonic structure such as the Moho depth or the lithosphere-asthenosphere-boundary, this asymmetric pattern suggests a difference in the depth of these boundaries within the basin. The observed discrepancy between the inferred spreading axis and the MHF distribution indicates that the Chukchi Basin may have undergone asymmetric rifting, challenging the conventional notion of symmetric rifting. Our future research will integrate gravity and magnetic anomaly data with numerical modeling to better constrain the deep structure and formation processes of the basin.

During the last 1 Ma in the Canadian Arctic, permafrost and permafrost-associated gas hydrates formed extensively due to mean annual subaerial temperatures of approximately -20°C. Following the last glaciation, a marine transgression occurred and former terrestrially exposed shelves became inundated, resulting in present submarine bottom water temperatures around -1°C. Relict submarine permafrost and gas hydrates in the Canadian Beaufort Sea are still responding to this thermal change resulting in their ongoing degradation. Thawing of permafrost and destabilisation of permafrost-associated gas hydrates can release previously trapped greenhouse gases and can lead to even further gas hydrate dissociation with important implications for the global climate. However, both the extent of the submarine permafrost and the permafrost-associated gas hydrates are still not well known. In this study, we use marine multichannel seismic data to model the base of permafrost from the depth of the base of the gas hydrate stability zone. From this depth, we estimate the theoretical gas hydrate dissociation temperature, which allows us to model the depth of the thermal base of permafrost (0°C isotherm). The base of permafrost we modelled correlates with the lower boundary of a diffuse zone of high diffractivity in seismic data suggesting the presence of ice-bearing permafrost. These results combined show that the base of permafrost still extends close to the shelf edge indicating less permafrost retreat than previously suggested. Our study provides a different approach to accessing the current depth and extent of submarine permafrost on the outermost Canadian Beaufort Shelf.

The stability and spatial distribution of subsea permafrost across the Arctic continental shelves play a pivotal role in our understanding of global warming. Serving as a significant carbon store, this permafrost has the potential to release greenhouse gases when it thaws, significantly influencing the global climate. This study is dedicated to a comprehensive investigation of the extent and state of submarine permafrost within the Arctic, with a particular focus on the comparative analysis of subsea permafrost development along the continental shelves of the Beaufort and East Siberian Seas. This research enhances our grasp of Arctic subsea permafrost's current variability and its role in global warming processes. To map the extent of subsea permafrost, we utilized multichannel seismic data from the Beaufort Sea (2014) and East Siberian Sea (2016, 2019), collected by the IBRV Araon. Employing a full waveform inversion approach, we precisely determined the seafloor permafrost's velocity structure, offering insights into its depth and state. The research reveals pronounced regional variations in the development of subsea permafrost on Arctic continental shelves. In particular, the continental shelf of the Beaufort Sea is characterized by a densely concentrated distribution of subsea permafrost extending to depths of up to 600 meters. In contrast, the continental shelf of the East Siberian Sea is dominated by permafrost that has thawed significantly, reaching depths of around 400 meters. These different regional patterns may be influenced by a number of factors, including the proximity of the shelf to the coast, the influence of ocean currents, the geological composition of the seabed and the prevailing thermal conditions. These findings suggest that the highly variable nature of submarine permafrost across the Arctic shelf is crucial to understanding warming induced changes in Arctic submarine permafrost and the potential for greenhouse gas release through permafrost dissociation.

The Amerasia Basin, one of two major basins that comprise the Arctic Ocean, is thought to have a more complex formation history than its counterpart, the Eurasian Basin. Because the harsh conditions for marine expeditions last the entire year, there is a lack of observational data for constraining the tectonic history of the Chukchi Basin. Thus, there are multiple existing hypotheses for its tectonic history, with contrasting formation ages ranging from Mesozoic to Cenozoic and crustal types ranging from hyper-extended continental crust to oceanic crust. Recently, during the 2018 and 2021 Arctic expeditions of the Korean ice-breaking research vessel Araon, we obtained the new marine heat flow data along the east-west and northeast-southwest transect lines from the abyssal plain to the continental slope/shelf of the basin. These data may play an important role in constraining the formation age of the basin, as the extending axis among the hypotheses is likely oriented from north-south. Assuming an oceanic crust, the formation age can be inferred to be Late Cretaceous. This information concerning the formation age enhances our understanding of the underestimated complex tectonic history of the Amerasia Basin, because such inferred timing aligns with the formation age of the adjacent Chukchi Borderland.