https://repository.kopri.re.kr/handle/201206/13428 2026-04-26T00:35:44Z https://repository.kopri.re.kr/handle/201206/14441 Title: Water Mass Controlled Vertical Stratification of Bacterial and Archaeal Communities in the Western Arctic Ocean During Summer Sea-Ice Melting Authors: Puthiya Veettil Vipindas; Siddarthan Venkatachalam; Thajudeen Jabir; Yang, Eun Jin; Cho, Kyoung-Ho; Jung, Jinyoung; Lee, Youngju; Kottekkatu Padinchati Krishnan Abstract: The environmental variations and their interactions with the biosphere are vital in the Arctic Ocean during the summer sea- ice melting period in the current scenario of climate change. Hence, we analysed the vertical distribution of bacterial and archaeal communities in the western Arctic Ocean from sea surface melt-ponds to deep water up to a 3040 m depth. The distribution of microbial communities showed a clear stratification with significant differences among different water depths, and the water masses in the Arctic Ocean - surface mixed layer, Atlantic water mass and deep Arctic water - appeared as a major factor explaining their distribution in the water column. A total of 34 bacterial phyla were detected in the seawater and 10 bacterial phyla in melt-ponds. Proteobacteria was the dominant phyla in the seawater irrespective of depth, whereas Bacteroidota was the dominant phyla in the melt-ponds. A fast expectation-maximization microbial source tracking analysis revealed that only limited dispersion of the bacterial community was possible across the stratified water column. The surface water mass contributed 21% of the microbial community to the deep chlorophyll maximum (DCM), while the DCM waters contributed only 3% of the microbial communities to the deeper water masses. Atlantic water mass contributed 37% to the microbial community of the deep Arctic water. Oligotrophic heterotrophic bacteria were dominant in the melt-ponds and surface waters, whereas chemoautotrophic and mixotrophic bacterial and archaeal communities were abundant in deeper waters. Chlorophyll and ammonium were the major environmental factors that determined the surface microbial communi- ties, whereas inorganic nutrient concentrations controlled the deep-water communities. 2023-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/13824 Title: Impact of Sea Ice Melting on Summer Air-Sea CO2 Exchange in the East Siberian Sea Authors: Mo, Ahra; Yang, Eun Jin; Kang, Sung-Ho; Kim, Dongseon; Lee, Kitack; Ko, Young Ho; Kim, Kitae; Kim, Tae-Wook Abstract: The role of sea ice melting on the air-sea CO2 flux was investigated at two ice camps in the East Siberian Sea of the Arctic Ocean. On average, sea ice samples from the two ice camps had a total alkalinity (TA) of ∼108 and ∼31 μmol kg-1 and a corresponding salinity of 1.39 and 0.36, respectively. A portion (18-23% as an average) of these sea ice TA values was estimated to exist in the sea ice with zero salinity, which indicates the excess TA was likely attributed to chemical (CaCO3 formation and dissolution) and biological processes in the sea ice. The dilution by sea ice melting could increase the oceanic CO2 uptake to 11-12 mmol m-2 d-1 over the next 21 days if the mixed layer depth and sea ice thickness were assumed to be 18.5 and 1.5 m, respectively. This role can be further enhanced by adding TA (including excess TA) from sea ice melting, but a simultaneous release of dissolved inorganic carbon (DIC) counteracts the effect of TA supply. In our study region, the additional impact of sea ice melting with close to unity TA:DIC ratio on air-sea CO2 exchange was not significant. 2022-02-23T00:00:00Z https://repository.kopri.re.kr/handle/201206/13666 Title: Changes in Freshwater Distribution and Pathways in the Arctic Ocean Since 2007 in the Mercator Ocean Global Operational System Authors: Cecilia Bertosio; Christine Provost; Marylou Athanase; Nathalie Sennechael; Gilles Garric; Jean-Michel Lellouche; Clement Bricaud; Kim, Joo-Hong; Cho, Kyoung-Ho; Park, Taewook Abstract: Low-salinity waters in the upper Arctic Ocean, referred to as “freshwaters”, are cold and play a major role in isolating the sea ice cover from the heat stored in the salty Atlantic Waters (AWs) underneath. We examined changes in Arctic freshwater distribution and circulation since 2007 using the 1/12° global Mercator Ocean operational model. We first evaluated model simulations over the upper water column in the Arctic Ocean, using nearly 20,000 independent in situ temperature-salinity profiles over the 2007？2020 period. Simulated hydrographic properties and water mass distributions were in good agreement with observations. Comparison with long-term mooring data in the Bering Strait and Beaufort Gyre highlighted the model's capabilities for reproducing the interannual evolution of Pacific Water properties. Taking advantage of the good performance of the model, we examined the interannual evolution of the freshwater distribution and circulation over 2007？2020. The Beaufort Gyre is the major freshwater reservoir across the full Arctic Ocean. After 2012 the gyre extended northward and increased the freshwater content (FC) in the Makarov Basin, near the North Pole. Coincidentally, the FC decreased along the East Siberian slope, along with the AW shoaling, and the Transpolar Drift moved from the Lomonosov Ridge to align with the Mendeleev Ridge. We found that these changes in freshwater distribution were followed in 2015 by a marked change in the export of freshwater from the Arctic Ocean with a reduction in Fram Strait (？30%) and an increase in the western Canadian Archipelago (+16%). 2022-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/13441 Title: Spatial and Interannual Patterns of Epipelagic Summer Mesozooplankton Community Structures in the Western Arctic Ocean in 2016-2020 Authors: Kim, Jee-Hoon; La, Hyoung Sul; Cho, Kyoung-Ho; Jung, Jinyoung; Kang, Sung-Ho; 이강현; Yang, Eun Jin Abstract: Mesozooplankton play a crucial role as primary or secondary consumers in Arctic ecosystems and are sensitive indicators of environmental changes. This research is the first comprehensive Arctic zooplankton study covering the area ranging from the southern Chukchi Sea (SCS) and the northern Chukchi Sea (NCS) to the East Siberian Sea (ESS). Mesozooplankton samples were collected at 151 stations in the western Arctic Ocean each August from 2016 to 2020. The mesozooplankton abundance of the study area ranged from 9 to 6,172 ind. m-3, and the predominant group was copepods at 7-3866 ind. m-3, of which Pseudocalanus spp. and Calanus glacialis were the most abundant copepods. In the SCS, small copepods and meroplankton, such as Pseudocalanus spp., Cirripedia larvae, Echinodermata larvae, and C. abdominalis were the predominant taxa. Especially in 2019, Centropages abdominalis dominated over meroplankton when water temperatures were high (maximum 12.5°C; sea surface temperature, SST). In the NCS and ESS, C. glacialis, Pseudocalanus spp., Metridia longa, Oithona similis, Parasagitta elegans, and Calanus hyperboreus were abundant. The distributions and structures of mesozooplankton communities indicated variability over large spatial scales in the western Arctic waters because of variations in multiple factors, such as water temperature, salinity, and sea ice; however, geographical effects cannot be ignored even during alterations in the physical properties. Our results suggest that these variable patterns of mesozooplankton communities fluctuate horizontally from south to north as warming progresses on a regional bathymetric basis, and can be used to infer the fate of mesozooplankton communities in the study area. 2022-01-01T00:00:00Z