https://repository.kopri.re.kr/handle/201206/13389 2026-04-07T04:41:45Z https://repository.kopri.re.kr/handle/201206/14764 Title: Vulnerability and resilience of the Arctic Svalbard to climate variability Authors: Nam, Seung-il 2023-11-28T00:00:00Z https://repository.kopri.re.kr/handle/201206/14282 Title: Millennial-scale oscillations and an environmental regime shift around the Middle to Late Holocene transition in the North Atlantic region based on a multiproxy record from Isfjorden, West Spitsbergen Authors: CAMILLE BRICE; de Vernal A.; Francus P.; Forwick M.; Nam, Seung-il Abstract: Palynological and sedimentological analyses were performed in the sediment core HH16-1205-GC retrieved from the central Isfjorden, West Spitsbergen. The sequence, that spans the last 7000 years, revealed an overall cooling trend with an important climate shift between 4.4 and 3.8 cal. ka BP, in addition to millennial-scale oscillations. Sea-surface reconstruction from dinocyst assemblages indicates a decrease in summer sea-surface temperature, from 2.5 to 1.5 °C, and primary productivity, from 750 to 650 gC m-² a-1 over the last 7000 years. From around 6.8 to 5.8 cal. ka BP, the sedimentological and palynological data suggest predominant sediment supply from the inner part of the fjord, ice rafting, dense sea-ice cover, strongly stratified water masses, and high primary productivity. The interval from 4.4 to 3.8 cal. ka BP is marked by a layer of coarser material and a significant decrease in the grain size mode. Our geochemical data show large-amplitude fluctuations after 2.0 cal. ka BP, while an increase of the dinocysts Impagidinium pallidum and Spiniferites elongatus from 2.0 to 1.2 cal. ka BP suggests enhanced Atlantic Water inflow. The dinocyst-based reconstructions also reveal large-amplitude millennial fluctuations in sea-ice cover, summer sea-surface temperature, and salinity. Wavelet analysis and cross-wavelet analysis on K/Ti ratio coupled with sea-ice estimates confirm a strong signal with a periodicity of 1200 to 1500 years. 2023-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/13963 Title: Metalloenzyme signatures in authigenic carbonates from the Chukchi Borderlands in the western Arctic Ocean Authors: 이동헌; Kim, Jung-Hyun; Lee, Yung Mi; Germain Bayon; Kim, Dahae; Joe, Young Jin; Xudong Wang; 신경훈; Jin, Young Keun Abstract: Migration of methane-rich fluids at submarine cold seeps drives intense microbial activity and precipitation of authigenic carbonates. In this study, we analyzed microbially derived authigenic carbonate samples recently recovered from active gas hydrate mounds on the southwestern slope of the Chukchi Borderlands (CB), western Arctic Ocean. Our main aim was to characterize the distribution patterns of trace elements in carbonate-hosted lipid fractions to assess metalloenzyme requirements of microbes involved in anaerobic oxidation of methane (AOM). We measured stable isotopes, trace elements, lipid biomarkers, and genomic DNA, and results indicate the dominance of AOM-related lipid biomarkers in studied carbonate samples, as well as a predominant occurrence of the anaerobic methanotrophic archaea (ANME)-1. We also report evidence for significant preferential enrichments of various trace elements (Li, Ni, Co, Cu, Zn, and Mo) in the total lipid fractions of CB carbonates, relative to elemental compositions determined for corresponding carbonate fractions, which differ from those previously reported for other seep sites. We hypothesize that trace element enrichments in carbonate-hosted lipid fractions could vary depending on the type of AOM microbial assemblage. Additional work is required to further investigate the mechanisms of lipid-bound trace elements in cold seep carbonates as potential metalloenzymes in AOM. 2022-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/13923 Title: The composition and abundance of phytoplankton after spring bloom in the Arctic Svalbard fjords Authors: Seongjun Bae; Haryun Kim; Nam, Seung-il; Keun-Hyung Choi; Tae-Wook Kim; Sung Tae Yun; Hye Seon Kim; Tae-Hoon Kim; Dukki Han; Young Ho Ko; Ju-Hyoung Kim; Young Kyun Lim; Joo Myun Park Abstract: Glacial melting and massive spring blooms caused by global warming have significantly altered the environmental conditions in the Svalbard fjords of the European Arctic. These changes included reduced salinity (the gradient of salinity from inner to outer fjords, ranging from 23 to 34 PSU), stratification of the water column, increased turbidity (> 135 FTU), low nutrient conditions (0.06 to 1.13 μM PO4？, 1.19 to 3.54 μM NO3？, 1.19 to 3.54 μM NH4+, and -2.1 to 0.9 N*), reduced light penetration, and release of organic matter, resulting in changes in the structure and composition of the phytoplankton. Our study, conducted in Isfjorden, van Mijenfjorden/Bellsund, and Hornsund of Svalbard in early August 2019, observed the dominance of cryptophytes in the phytoplankton composition after the spring bloom. Our results show a different phenomenon from the previous diatom/dinoflagellate dominance in the late 1970s and the early 2020s. Changes in phytoplankton composition can be explained as follows. (1) The excessive consumption of nutrients during spring bloom and the reduction of nutrient mixing in the water column stratification due to glacier melting have formed nutrient-depleted conditions, providing favorable conditions for the small-sized phytoplankton that easily find nutrients. (2) A wide range of salinities has created beneficial conditions for cryptophytes, capable of controlling osmotic stress against various salinities, of surviving compared to diatoms and dinoflagellates. (3) Finally, the influx of organic matter into fjords due to glacier melting can increase turbidity and decrease light availability; therefore, cryptophytes with mixotrophic metabolisms could be more viable than diatoms with only autotrophic metabolisms. In summary, the dynamic environmental conditions after enhanced spring bloom and glacier melting will further alter phytoplankton compositions and, in turn, influence food webs at higher tropical levels in European Arctic fjord ecosystems. 2022-01-01T00:00:00Z