https://repository.kopri.re.kr/handle/201206/5330 2026-04-07T15:57:30Z https://repository.kopri.re.kr/handle/201206/16103 Title: Changes in Sedimentary Organic Carbon Compositions in the Mackenzie Trough Over Recent Centuries: Insights Into Permafrost Thawing in the Canadian Arctic Authors: Kim, Dahae; Kim, Jung-Hyun; Joe, Young Jin; Ahn, Youngkyu; Tesi Tommaso; Lohmann Gerrit; Jeong, Sujeong; Nam, Seung-il Abstract: This study analyzed three sediment cores (ARA08C/02-2BC, ARA08C/03-2BC, and ARA04C-40MUC) from the Mackenzie Trough in the Beaufort Sea, collected in 2013 and 2017. Using bulk sediment properties (carbon and nitrogen contents, stable carbon isotopes, and radiocarbon isotopes) and terrestrial biomarkers (lignin phenols), we examined the impacts of permafrost thaw on sedimentary organic carbon (OC) in the Canadian Beaufort Sea. Our objective was to investigate whether changes in OC sources reflect the environmental changes documented in the region over the past few decades. At the core site of ARA08C/03-2BC, we observed an increase in soil-derived OC accumulation rates (ARs) since the early 20th century, with a noticeable rise over the past few decades, while petrogenic OC ARs showed a slight decline. Grain size end-member (EM) modeling identified three primary EM groups, revealing a general increase in the proportion of coarse grains (sum of EM2 + EM3 end-members) since the early 1900s, with a marked acceleration in recent decades. These trends align with regional surface temperature increases over the past few decades, suggesting that permafrost thaw has increasingly affected sedimentary OC dynamics in the Canadian Beaufort Sea. Given climate models that predict accelerated warming in the Mackenzie Basin, our findings highlight the critical need for precise quantification of OC fluxes to improve projections of regional carbon budgets and climate dynamics in the Arctic. 2025-07-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/12031 Title: A pilot study of tracing terrestrial organic carbon along the Mackenzie Trough (Beaufort Sea) Authors: Kim, Jung-Hyun 2018-12-21T00:00:00Z https://repository.kopri.re.kr/handle/201206/12589 Title: New insights into the application of the PIP25 index in the Arctic Ocean Authors: Nam, Seung-il; Gal, Jong-Ku; Smik, Lukas; Wary, Melanie; Belt, Simon T.; Shin, Kyung-Hoon; Etourneau, Johan; Sanchez Goni, Maria Fernanda; Nam, Seung-il Abstract: In this study we investigated suspended particulate matter (SPM) collected along a transect from the East Sea of Korea to the Bering Sea from 18 to 28 July in 2015, a multicore (ARA01B-3MUC) retrieved from the Chukchi shelf region, and a piston core (MD95-2009) taken from the Nordic Seas. We analyzed the samples for the Arctic sea ice proxy IP25 together with a tri-unsaturated highly branched isoprenoid (HBI triene) and two sterols (epi-brassicasterol and dinosterol) to assess the suitability of these compounds for the so-called PIP25 index in the Arctic region as a proxy for sea ice change in the past. Our results highlight that the use of HBI triene, epi-brassicasterol, and dinosterol, as strict phytoplankton markers for the PIP25 index (i.e. PTIP25, PBIP25 and PDIP25, respectively), might result in misleading outcomes. Accordingly, our study highlights that more work is needed to better constrain the use of HBI triene, epi-brassicasterol, and dinosterol, as strict ice-free, open ocean phytoplankton biomarkers when applying the PIP25 index for reconstructing past sea ice changes. 2018-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/8241 Title: Distribution of pelagic phytoplankton-derived lipid biomarkers in the Northwest Pacific region: insights into their suitability as open-water indicators Authors: Gal, Jong-Ku; Shin, Kyung-Hoon; Seung-Il Nam; Simon T. Belt; Sun Yong Ha; Lukas Smik; Kim, Jung-Hyun Abstract: The phytoplankton marker-IP25 (PIP25) index has been proposed to more quantitatively reconstruct the past sea ice conditions. To date, brassicasterol, dinosterol and HBI triene have been used as pelagic phytoplankton-derived lipid biomarkers when calculating the PIP25 index. This approach has been generally applied within sedimentary work, with fewer efforts observed on material collected within the water column. Moreover, it is not clear which planktonic biomarker is more suitable for the PIP25 index. In this study, we collected suspended particulate matter (SPM) along a transect from the East Sea to the Bering Sea from 18 to 28 July in 2015 and analyzed highly branched isoprenoid (HBIs) and sterols. IP25 was not detected in any of the samples, with HBI triene only detected in the five stations across the Northwest Pacific and Bering Sea. However, all sterols considered in this study were detected in all stations. Interestingly, brassicasterol concentration showed a strong, positive relationship with cholesterol concentration, but no relationship with chlorophyll a, suggesting that the former might have been associated with not only marine phytoplankton but other sources in the study area, such as zooplankton. Dinosterol and HBI triene concentrations also showed no clear relationship with chl. a or brassicasterol concentrations, indicating likely different and diverse sources of these lipids in addition to marine phytoplankton. Therefore, our study suggests that applying brassicasterol, dinosterol, and HBI triene to PIP25 under the same sea-ice conditions may lead to different trends. Further studies on the seasonal and spatial variations of the planktonic biomarkers are needed to better constrain the use of these lipids as ice-free, open ocean biomarkers when using the PIP25 index in the western Arctic region. 2017-01-01T00:00:00Z