https://repository.kopri.re.kr/handle/201206/11896 2026-04-11T17:08:47Z 2026-04-11T17:08:47Z Yun, Sukyoung Lee, Won Sang Dziak, Robert P. Matsumoto, Haruyoshi https://repository.kopri.re.kr/handle/201206/13568 2022-07-07T01:23:01Z 2022-07-01T00:00:00Z

Title: Numerical Study on the Characteristics of Abyssal T-wave Envelopes Controlled by Earthquake Source Parameters Authors: Yun, Sukyoung; Lee, Won Sang; Dziak, Robert P.; Matsumoto, Haruyoshi Abstract: Hydroacoustics has been successfully applied to detect and locate small to intermediate submarine tectonic activities infrequently recorded in land-based seismic arrays. However, to extend the utilization of T-waves to extract other important earthquake source parameters, such as source strength, the roles of earthquake focal mechanisms and source depths in T-wave envelopes must be thoroughly understood. We performed 3-D numerical modeling considering anisotropic source radiation and realistic scattering in the oceanic crust for two focal mechanisms (normal and strike-slip faults) and three depths (5, 10, and 15 km) to investigate the effect of source radiation and focal depth on abyssal T-waves. By analyzing the synthetic Twave envelopes, we showed that stronger SV-energy radiation from a normal-fault earthquake event generates higher-intensity T-waves of the same source magnitude. The anisotropic source radiation of a double-couple source causes azimuthal changes in the shapes of T-waves, and deeper earthquakes cause gentle sloped envelopes; however, the slopes also vary with respect to the azimuths of receivers and focal mechanisms. Temporal changes in the slopes of T-wave envelopes of magmatic swarm events near Wordie Volcano, Bransfield Strait, Antarctic Peninsula, imply that the depth dependency can be utilized to determine relative depths for hydrothermal-vent events or sequenced earthquakes.

2022-07-01T00:00:00Z Lee, Jeonghoon Lee, Won Sang Jung, Hyejung Lee, Seung-Gu https://repository.kopri.re.kr/handle/201206/13543 2022-07-06T07:41:31Z 2022-02-22T00:00:00Z

Title: Comparison between total least squares and ordinary least squares in obtaining the linear relationship between stable water isotopes Authors: Lee, Jeonghoon; Lee, Won Sang; Jung, Hyejung; Lee, Seung-Gu Abstract: The linear relationship between two stable water isotopes (δD and δ18O) has been used to examine the physical processes and movements or changes of three water phases (water vapor, liquid water and ice), including deuterium excess. The ordinary least squares (OLS) method has been the most commonly used method to fit the linear relationship between two isotopic compositions of water. However, an alternative method, the total least squares (TLS) method, has been proposed because it considers the presence of errors in the explanatory variable (horizontal axis, δ18O). However, not many studies have examined the differences of the relationship using two stable isotopes between the OLS and TLS for various types of water. In this work, these two methods were compared using isotopic compositions of three types of water (Antarctic snow, water vapor and summer and winter rainfall). Statistically, the slopes and intercepts obtained by the two linear regression methods were not significantly different except for summer rainfall, which has the smallest coefficient of variations (R2). The TLS method produced larger slopes than the OLS method and the degrees of difference between the two methods were greater when the coefficient of variation was lower. In addition, with a Monte Carlo method, we showed that the differences between the two methods increased as the uncertainty increased. Moreover, the results of Bayesian linear regression were consistent with the two linear regressions. Although the TLS method is theoretically more suited to the linear regression for the stable water isotopes than the OLS method is, the application of the widely used OLS method can be recommended in the case of small measurements uncertainties after testing whether the linear parameters, slopes and intercepts, derived from the two methods are statistically significant different.

2022-02-22T00:00:00Z Yoon, Seung-Tae Lee, Won Sang Nam, SungHyun Lee, Choon-Ki Yun, Sukyoung Heywood, Karen Boehme, Lars Zheng, Yixi Lee, Inhee Choi, Yeon Jenkins, Adrian Jin, Emilia Kyung Larter, Robert Wellner, Julia Dutrieux, Pierre Bradley, Alexander T. https://repository.kopri.re.kr/handle/201206/13264 2022-03-24T07:15:43Z 2022-01-13T00:00:00Z

Title: Ice front retreat reconfigures meltwater-driven gyres modulating ocean heat delivery to an Antarctic ice shelf Authors: Yoon, Seung-Tae; Lee, Won Sang; Nam, SungHyun; Lee, Choon-Ki; Yun, Sukyoung; Heywood, Karen; Boehme, Lars; Zheng, Yixi; Lee, Inhee; Choi, Yeon; Jenkins, Adrian; Jin, Emilia Kyung; Larter, Robert; Wellner, Julia; Dutrieux, Pierre; Bradley, Alexander T. Abstract: Glacial melt can modify heat transport, and therefore ocean processes, associated with ice front retreat, as revealed by direct observations from the Pine Island Bay region of Antarctica. Pine Island Ice Shelf (PIIS) buttresses the Pine Island Glacier, the key contributor to sea-level rise. PIIS has thinned owing to ocean-driven melting, and its calving front has retreated, leading to buttressing loss. PIIS melting depends primarily on the thermocline variability in its front. Furthermore, local ocean circulation shifts adjust heat transport within Pine Island Bay (PIB), yet oceanic processes underlying the ice front retreat remain unclear. Here, we report a PIB double-gyre that moves with the PIIS calving front and hypothesise that it controls ocean heat input towards PIIS. Glacial melt generates cyclonic and anticyclonic gyres near and off PIIS, and meltwater outflows converge into the anticyclonic gyre with a deep-convex-downward thermocline. The double-gyre migrated eastward as the calving front retreated, placing the anticyclonic gyre over a shallow seafloor ridge, reducing the ocean heat input towards PIIS. Reconfigurations of meltwater-driven gyres associated with moving ice boundaries might be crucial in modulating ocean heat delivery to glacial ice.

2022-01-13T00:00:00Z Yoon, Seung-Tae Lee, Won Young https://repository.kopri.re.kr/handle/201206/13576 2022-07-07T02:10:14Z 2021-12-01T00:00:00Z

Title: Quality Control Methods for CTD Data Collected by Using Instrumented Marine Mammals: A Review and Case Study Authors: Yoon, Seung-Tae; Lee, Won Young Abstract: ‘Marine mammals-based observations’ refers to data acquisition activities from marine mammals by instrumenting CTD (Conductivity-Temperature-Depth) sensors on them for recording vertical profiles of ocean variables such as temperature and salinity during animal diving. It is a novel data collecting platform that significantly improves our abilities in observing extreme environments such as the Southern Ocean with low cost compared to the other conventional methods. Furthermore, the system continues to create valuable information until sensors are detached, expanding data coverage in both space and time. Owing to these practical advantages, the marine mammals-based observations become popular to investigate ocean circulation changes in the Southern Ocean. Although these merits may bring us more opportunities to understand ocean changes, the data should be carefully qualified before we interpret it incorporating shipboard/autonomous vehicles/moored CTD data. In particular, we need to pay more attention to salinity correction due to the usage of an unpumped-CTD sensor tagged on marine mammals. In this article, we introduce quality control methods for the marine mammals-based CTD profiles that have been developed in recent studies. In addition, we discuss strategies of quality control specifically for the seal-tagging CTD profiles, successfully having been obtained near Terra Nova Bay, Ross Sea, Antarctica since February 2021. It is the Korea Polar Research Institute’s research initiative of animal-borne instruments monitoring in the region. We anticipate that this initiative would facilitate collaborative efforts among Polar physical oceanographers and even marine mammal behavior researchers to understand better rapid changes in marine environments in the warming world.

2021-12-01T00:00:00Z