Open Access Collection of International and Scholarly Papers
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黒潮続流および黒潮親潮混合水域における冬季海面熱フラックス変動の解明
Full text link東京海洋大学修士(工学)東京海洋大学修士学位論文 2024年度(2025年3月) 海運ロジスティクス 修士 第4624号指導教員: 小橋史明全文公表年月日: 2025-06-13master thesi
Hydrographic section along 55°E in the Indian and Southern oceans
No full textA hydrographic section along 55° E, south of 30° S, was visited from December 2019 to January 2020 as the first occupation under the Global Ocean Ship-based Hydrographic Investigations Program. The water column was measured from the sea surface to 10 dbar above the bottom with eddy-resolving station spacings and state-of-the-art accuracy. The upper profile was characterised by a conspicuous front between 42.5 and 43° S and a cold-core eddy at 39° S. The front was identified as the confluence of Subtropical and Subantarctic fronts. The Agulhas Return Current front was found at 41.6° S. When combined with the section north of 30° S observed in 2018, another subsurface front was found in dissolved oxygen around 28° S at depths of 1500 to 3000 dbar. In the eastern Weddell–Enderby Abyssal Plain, no obvious large-scale flow was observed at depths greater than 3000 dbar. We used transient tracers to estimate isopycnal diffusivity there to be 72±16 m2 s−1. Antarctic Bottom Water in the basin consisted of water masses originating from the Cape Darnley region (0 %–35 %) and Weddell Sea Deep Water (5 %–75 %) diluted by Lower Circumpolar Deep Water above. These snapshot observations not only confirm hydrographic features reported earlier in the Madagascar and Crozet basins, but also describe the diffusive nature of the deep to bottom circulation in the Weddell–Enderby Abyssal Plain.公開日: 2025-02-12journal articl
Subsurface warming associated with Pacific Summer Water transport toward the Chukchi Borderland in the Arctic Ocean
No full textRecent rapid sea ice reduction in the Pacific sector of the Arctic Ocean is potentially associated with inflow of Pacific-origin water via the Bering Strait. For the first time, we detected remarkable subsurface warming around the Chukchi Borderland in the Arctic Ocean over the recent two decades (i.e., the early 21st century). A statistically significant decadal trend of 16.6 ± 10.6 MJ m− 2 year− 1 in the subsurface ocean heat content during 1999–2020 was captured by shipboard hydrographic data, and associated with the transport of Pacific Summer Water from Barrow Canyon northwest of the Alaskan coast, where similar warming appeared. Satellite-derived geostrophic ocean velocity indicated that the northwestward ocean current flowing from Barrow Canyon to the Chukchi Borderland became faster in the late 2010s, in association with southeastward shift of the Beaufort Gyre, circulating clockwise around the Canada Basin. Therefore, we suggest that warming of the Pacific Summer Water passing over the Chukchi shelf and intensification of the northwestward ocean current along the shelf–basin boundary both acted to enhance the heat transport and contributed to the positive trend in downstream subsurface ocean heat content. Our findings fill important gaps in the understanding of ocean heat distribution/transport, which is a key factor for sea ice freezing/melting, in the central Arctic.公開日: 2025-01-102222100315H0173618H03368journal articl
Classification of sounds from Pacific white-sided dolphins using a convolutional neural network and a method to reduce false-positive detections
No full textAn automatic detector for identifying the clicks and pulsed calls of Pacific white-sided dolphins (Lagenorhynchus obliquidens) was developed using a convolutional neural network architecture for passive acoustic monitoring, particularly in the areas surrounding the Mutsu and Funka Bays in Japan. Recordings were made at one site in each bay during the spring and early summer in both 2022 and 2023. The data exhibited different soundscapes, as broadband pulses, possibly attributed to snapping shrimp, were found far more frequently in Mutsu Bay than in Funka Bay. The developed detector showed a precision, recall, and accuracy of 0.94–0.95, 0.94, and 0.98, respectively, for both call types. Furthermore, considering the social and gregarious characteristics of the investigated species, an additional selection criterion using a two-process model was proposed to eliminate hours with few positive images. The selection criterion could remove 58%–84% of false-positive images, 0%–0.5% of true-positive images for clicks, 32%–96% of false-positives, and 6%–33% of true-positives for pulsed calls during the periods that were manually inspected. Processing using a combination of the detector and selection criterion can be applied to passive acoustic monitoring around these bays to reveal the migration patterns of Lagenorhynchus obliquidens.公開日: 2025-06-0520K1997624K2093822H05651journal articl
食品中の細菌に対する過酢酸製剤の殺菌効果及びその抗菌メカニズムの解明
Full text link東京海洋大学博士(海洋科学)東京海洋大学博士学位論文 2024年度(2025年3月) 応用生命科学 課程博士 甲718号指導教員: 高橋肇doctoral thesi
海藻付着珪藻ファルキュラ属 Falcula（珪藻植物門）の宿主特異性に関する研究
Full text link東京海洋大学博士(海洋科学)東京海洋大学博士学位論文 2024年度(2025年3月) 応用環境システム学 課程博士 甲734号指導教員: 鈴木秀和doctoral thesi
Status and prospects of biogeochemical Argo observations of chlorophyll-a in the northwest Pacific
No full textBiogeochemical Argo (BGC-Argo) floats are autonomous marine observing platforms that monitor chlorophyll-a and other indicators of ocean ecosystem health globally. Since 2018, there has been an increase in the number of chlorophyll-a observations in the northwest Pacific due to the deployment of BGC-Argo floats. Such progress offers an unprecedented opportunity to develop a skillful operational ocean biogeochemical model. Here, we assess the performance of BGC-Argo floats in measuring chlorophyll-a concentrations and their spatiotemporal structures via comparison with satellite and shipboard data. Results show a good correlation (r = 0.61) between the float and satellite observations and an excellent correlation (r = 0.87) between the satellite and shipboard observations of sea surface concentrations. The float data have a bias of about 0.04 mg m−3 or 59 % with respect to the satellite observations. Rare matchups between the float and shipboard observations of winter and summer profiles in the upper 200 m reveal an excellent correlation (r = 0.86), demonstrating the reliability of the vertical structure obtained from these floats. Concurrent two-year time series from five BGC-Argo floats reveal the prevalence of subsurface chlorophyll-a maxima in the subtropical northwest Pacific that can persist throughout the year. These findings stress the importance of subsurface monitoring to better quantify biological productivity and carbon export. We discuss the status of BGC-Argo floats in the northwest Pacific and recommend possible directions for modelling work and deployment efforts in achieving the proposed global array of 1000 floats in this decade, which has significant potential to improve predictability.公開日: 2025-02-28journal articl
GNSSとIMU統合に基づくスマートフォン測位の最適化とAIを利用した静止判定
Full text link東京海洋大学修士(工学)東京海洋大学修士学位論文 2025年度(2025年9月) 海運ロジスティクス 修士 第4664号指導教員: 久保信明全文公表年月日: 2025-12-18master thesi
マプタプット工業港周辺における交通量影響の予測
Full text link東京海洋大学修士(工学)東京海洋大学修士学位論文 2025年度(2025年9月) 海運ロジスティクス 修士 第4665号指導教員: 渡部大輔全文公表年月日: 2025-12-18master thesi
船舶の電気推進化による環境負荷に関する研究
Full text link東京海洋大学修士(工学)東京海洋大学修士学位論文 2025年度(2025年9月) 海運ロジスティクス 修士 第4668号指導教員: 南清和全文公表年月日: 2025-12-18master thesi