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Phylogeny of prokaryotes involved in mercury speciation in free-living and particulate-attached fractions in Minamata Bay, Japan 日本水俣湾自由生物和微粒附着物中参与汞分化的原核生物的系统发育
IF 2.3 4区 地球科学 Q4 OCEANOGRAPHY Pub Date : 2024-09-17 DOI: 10.1007/s10872-024-00735-7
Yuya Tada, Kenji Yoshino, Katsumasa Yamada, Akito Matsuyama, Kohji Marumoto

Marine prokaryotes are involved in mercury (Hg) speciation in marine environments. However, information regarding the specific microbial lineages contributing to Hg speciation (namely, methylation, demethylation, and reduction) in seawater remains limited. In this study, we investigated the genes involved in methylmercury (MeHg) demethylation (merB), Hg reduction (merA), and Hg methylation (hgcA and hgcB) using a metagenome analysis encompassing free-living (FL; 0.2–3 µm) and particle-attached (PA; > 3 µm) fractions in April and June in Minamata Bay, Japan. We analyzed the total Hg (THg) and MeHg concentrations in dissolved, small particulate (0.2–3 µm), and large particulate (> 3 µm) fractions. Hg analysis showed no significant differences in THg and MeHg concentrations among the three fractions. However, THg and MeHg in the pooled particulate (fractions were higher than those in the dissolved fractions) in June. As for the Hg-related genes, a high merB abundance rather than merA was observed when compared using all samples, suggesting that microbial MeHg demethylation could be prominent rather than Hg reduction in the seawater column. Phylogenetic analyses revealed that Alphaproteobacteria and Actinobacteria were dominant in the total merA and merB-like sequences, respectively. For both merA and merB genes, some lineages appeared in either or both FL and PA fractions. A deltaproteobacteria-like hgcA was also detected in the PA fraction in April. Therefore, the link between distinct phylogenetic lineages within the PA and FL fractions could be significant for Hg speciation in Minamata Bay.

海洋原核生物参与了海洋环境中的汞(Hg)分化。然而,有关在海水中促进汞物种形成(即甲基化、去甲基化和还原)的特定微生物系的信息仍然有限。在本研究中,我们利用元基因组分析方法,调查了日本水俣湾四月和六月的甲基汞(MeHg)脱甲基(merB)、汞还原(merA)和汞甲基化(hgcA 和 hgcB)基因,包括自由生活(FL;0.2-3 µm)和颗粒附着(PA;> 3 µm)部分。我们分析了溶解物、小颗粒物(0.2-3 微米)和大颗粒物(3 微米)中的总汞(THg)和甲基汞浓度。汞分析表明,三种馏分中的总汞和甲基汞浓度没有明显差异。不过,6 月份的总颗粒物(馏分)中的三卤甲烷和甲基汞含量高于溶解馏分。在汞相关基因方面,与所有样本相比,merB 的丰度较高,而 merA 的丰度较低。系统进化分析表明,在全部 merA 和 merB 样序列中,变形菌和放线菌分别占主导地位。在 merA 和 merB 基因中,一些菌系同时出现在 FL 和 PA 部分中。在四月份的 PA 部分中还检测到类似于 deltaproteobacteria 的 hgcA。因此,PA 和 FL 部分中不同系统发生系之间的联系可能对水俣湾的汞物种分化具有重要意义。
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引用次数: 0
Variabilities in the estimate of 100-year return period wave height in the Indian shelf seas 印度大陆架海域 100 年重现期波浪高度估算的变异性
IF 2.3 4区 地球科学 Q4 OCEANOGRAPHY Pub Date : 2024-09-14 DOI: 10.1007/s10872-024-00733-9
Subal Vinayan, V. Sanil Kumar, R. Sajeev

Exploring the variability in design wave heights through extreme value analysis is crucial for understanding extreme oceanographic conditions and is paramount for the safe design and operation of offshore structures. This research delves into a comprehensive analysis of wave height variability in the Indian shelf seas, focusing on wave heights for a 100-year return period at 30 locations using 42 years of reanalysis data. The study employs the Generalized Extreme Value distribution and the Generalized Pareto Distribution (GPD), utilizing the annual maxima approach with three methods: maximum likelihood, probability-weighted moments, and moments of probability scale. The GPD Peaks Over Threshold (POT) approach is explored with thresholds estimated using various (91 to 99) percentiles, alongside a graphical approach utilizing threshold determination through mean residual life (MRL) plots. Results indicate that the GPD POT approach, particularly when employing thresholds derived from MRL plots, outperforms other methods. Thresholds obtained by MRL method closely align with the thresholds obtained through the 99 percentile for all locations in the Arabian Sea. This investigation not only enhances our understanding of the dynamic wave processes in the Indian shelf seas but also underscores the efficacy of specific statistical distributions and approaches in the evaluation of design wave heights.

通过极值分析探索设计波高的变化对于了解极端海洋条件至关重要,对于近海结构的安全设计和运行也至关重要。本研究利用 42 年的再分析数据,对印度大陆架海域的波高变化进行了全面分析,重点研究了 30 个地点 100 年重现期的波高。研究采用了广义极值分布和广义帕累托分布 (GPD),利用年最大值法,并使用了三种方法:最大似然法、概率加权矩法和概率标度矩法。GPD 峰值超过阈值 (POT) 方法是利用不同的(91 到 99)百分位数估算阈值,同时采用图形方法,通过平均残余寿命 (MRL) 图确定阈值。结果表明,GPD POT 方法,尤其是在采用从 MRL 图中得出的阈值时,优于其他方法。通过 MRL 方法获得的阈值与通过阿拉伯海所有地点的 99 百分位数获得的阈值非常接近。这项调查不仅加深了我们对印度大陆架海域动态波浪过程的了解,还强调了特定统计分布和方法在评估设计波高方面的功效。
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引用次数: 0
Spatiotemporal changes in chlorophyll a concentration in the inner area of Tokyo Bay from 2016 to 2020 2016 年至 2020 年东京湾内部地区叶绿素 a 浓度的时空变化
IF 2.3 4区 地球科学 Q4 OCEANOGRAPHY Pub Date : 2024-09-03 DOI: 10.1007/s10872-024-00730-y
Qiaoli Jiang, Yutaro Ando, Yo Ueno, Makoto Yasuda, Ayane Tanaka, Saori Yasui-Tamura, Fuminori Hashihama, Maiko Kagami, Toshiya Katano

Tokyo Bay is one of the most productive coastal systems in the world. Surrounded by a growing urban metropolis, the bay has experienced large fluctuations in water quality over the past decades due to eutrophication and regulatory requirements for wastewater treatment. However, the spatial and temporal variability of chlorophyll a (Chl a) and associated environmental factors remains unclear. In this study, water temperature, salinity, light condition, Chl a and nutrient concentrations was investigated monthly at three stations in the inner area from November 2016 to October 2020. In the surface water, the Chl a and nutrient concentrations largely fluctuated seasonally. In the summer season (May–September), with sufficient nutrient input from rivers and wastewater treatment plants, Chl a concentration in the northwestern part of the bay (St. AO) was positively correlated with water temperature with extremely high concentration (mean, 90.5 µg L−1). On the other hand, those in the northern (St. CB) and central (St. F3) areas were negatively correlated with nutrient concentrations, especially DIP and DSi which sometimes decreased to below the detection limit (BDL). In the winter–spring season (January–April), the Chl a concentration was relatively high at St. CB (mean, 25.9 µg L−1), which could be attributed to light availability, sufficient light penetration to the bottom, and vertical mixing of the entire water column. These results indicated that the factors controlling Chl a differed among areas and seasons in the bay.

东京湾是世界上最富饶的海岸系统之一。在过去几十年中,由于富营养化和废水处理的监管要求,该海湾被不断发展的城市大都市所环绕,水质经历了巨大的波动。然而,叶绿素 a(Chl a)的时空变化及相关环境因素仍不清楚。在本研究中,从 2016 年 11 月至 2020 年 10 月,每月在内城地区的三个站点调查水温、盐度、光照条件、叶绿素 a 和营养物质浓度。在地表水中,Chl a 和营养物质浓度主要随季节波动。在夏季(5 月至 9 月),来自河流和污水处理厂的营养物质输入充足,海湾西北部(圣 AO)的 Chl a 浓度与水温呈正相关,浓度极高(平均值为 90.5 µg L-1)。另一方面,北部(圣 CB)和中部(圣 F3)地区的叶绿素 a 浓度与营养物浓度呈负相关,尤其是 DIP 和 DSi,有时会降低到检测限(BDL)以下。在冬春季节(1 月至 4 月),St. CB 的 Chl a 浓度相对较高(平均值为 25.9 µg L-1),这可能是由于光照充足、光照可穿透至底部以及整个水体的垂直混合所致。这些结果表明,控制海湾不同区域和不同季节 Chl a 的因素各不相同。
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引用次数: 0
Marine heatwave in the Oyashio region in 2022/23 and its impact on subsurface dissolved oxygen 2022/23 年大盐生地区海洋热浪及其对表层下溶解氧的影响
IF 2.3 4区 地球科学 Q4 OCEANOGRAPHY Pub Date : 2024-09-03 DOI: 10.1007/s10872-024-00731-x
Yoshimi Kawai, Eitarou Oka, Kanako Sato, Shigeki Hosoda, Shoichiro Kido

The Oyashio region east of northern Japan has experienced frequent marine heatwaves (MHWs) since 2010, and in the summer and fall of 2022, sea surface temperature hit a record high as of that year. This study examined the impact of the 2022/23 MHW on dissolved oxygen (DO) by analyzing observations from a vessel and biogeochemical Argo floats. It was found that warm saline water from the Kuroshio Current intruded at ~ 42°N in July. DO anomalies from the climatology above a depth of 200 m were negatively correlated with the temperature anomalies at the same depth, while the opposite was true for deeper depths. In the density coordinate, DO and temperature anomalies exhibited a strong negative correlation when the potential density (σθ) was less than ~ 27.0 kg m−3. Thus, it was demonstrated that subsurface DO anomalies could be statistically predicted from temperature and salinity fields using this relationship. Notably, DO anomalies could be divided into components related to isopycnal mixing and density-surface heaving. This decomposition revealed a dynamical process, whereby the intrusion of the Kuroshio water, which is lighter than the Oyashio water, pushed down the density surfaces, causing oxygenation. Meanwhile, isopycnal mixing tended to mitigate the increase of DO concentration since DO concentration was smaller in the south than in the north on an isopycnal surface of σθ < 27.0 kg m−3. This study clarified that, during the 2022/23 MHW, deoxygenation occurred near the surface owing the warming, whereas the DO concentration increased in the subsurface layer.

自 2010 年以来,日本北部以东的大盐生地区频繁出现海洋热浪(MHW),2022 年夏秋季的海面温度创下了当年的最高纪录。本研究通过分析船只和生物地球化学 Argo 浮标的观测数据,研究了 2022/23 年 MHW 对溶解氧(DO)的影响。研究发现,来自黑潮的暖咸水于 7 月份侵入北纬约 42 度。从气候学角度看,200 米深度以上的溶解氧异常与同一深度的温度异常呈负相关,而更深的深度则相反。在密度坐标中,当潜在密度(σθ)小于 ~ 27.0 kg m-3 时,溶解氧和温度异常表现出强烈的负相关。因此,利用这种关系可以从温度场和盐度场统计预测地下溶解氧异常。值得注意的是,溶解氧异常可分为与等压混合和密度-表层翻腾有关的部分。这种分解揭示了一个动态过程,即黑潮水(比大雅叙海水轻)的侵入推低了密度面,从而导致含氧量增加。同时,等压面混合有减缓溶解氧浓度增加的趋势,因为在 σθ < 27.0 kg m-3 的等压面上,南部的溶解氧浓度小于北部。这项研究表明,在 2022/23 年中高纬度期间,由于气候变暖,表层附近出现了脱氧现象,而次表层的溶解氧浓度则有所增加。
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引用次数: 0
Temporal changes of the Oyashio water distribution east of Japan under the changing climate: development of an objective evaluation method and its application 气候变化下日本东部大盐水分布的时间变化:客观评价方法的开发及其应用
IF 2.3 4区 地球科学 Q4 OCEANOGRAPHY Pub Date : 2024-07-31 DOI: 10.1007/s10872-024-00727-7
Yuma Kawakami, Hideyuki Nakano, L. Shogo Urakawa, Takahiro Toyoda, Kunihiro Aoki, Nariaki Hirose, Norihisa Usui

The Oyashio, a southern part of the western boundary current in the North Pacific subarctic gyre, carries cold and fresh seawater with abundant nutrients southward from the high-latitude, influencing regional climate in the East Asia and marine environment in the western mid-latitude North Pacific. Previously, a distribution of the Oyashio water has been evaluated by empirical temperature thresholds; for example, in spring (March–May) when the Oyashio intrudes southward into the east of Japan, the Oyashio water is defined at 100-m depth as ≤ 5 °C. However, this method is not necessarily adequate under the changing climate because upper ocean temperature may change over time due to some causes unrelated to cold water transport by the Oyashio (e.g., surface heat fluxes). In this study, we developed an objective method to evaluate the Oyashio water distribution applicable under the changing climate with a focus on a thermohaline front located at the warm- and salty-side boundary of the Oyashio water. We identified isohalines at 100-m depth best corresponding to the thermohaline front in each month and used them as the Oyashio water threshold. Using the developed method, we further investigated the springtime Oyashio water distribution east of Japan (in the North Pacific south of 43°N, 141–148°E). The area of the Oyashio water shows inter-annual variation and significant long-term decrease. It was suggested that these temporal variation and change reflect changes in a distribution of anti-cyclonic meso-scale eddies off Hokkaido, which block the southward Oyashio intrusion into the east of Japan.

大矢潮是北太平洋亚北极涡旋西边界流的南部部分,它携带着含有丰富营养物质的冷淡海水从高纬度南下,影响着东亚地区的气候和北太平洋中纬度西部的海洋环境。以前,人们通过经验温度阈值来评估大盐水的分布;例如,在春季(3 月至 5 月)大盐水向南侵入日本东部时,100 米深处的大盐水被定义为≤ 5 °C。然而,在气候不断变化的情况下,这种方法并不一定适用,因为海洋上层的温度可能会随着时间的推移而发生变化,其原因与大矢海水的冷水输送(如表层热通量)无关。在这项研究中,我们开发了一种客观的方法来评估适用于不断变化的气候条件下的矢志水分布,重点是位于矢志水暖咸边界的温盐锋面。我们确定了各月与温盐前线相对应的 100 米等深线,并将其作为 Oyashio 水阈值。利用所开发的方法,我们进一步调查了日本以东(北纬 43°、东经 141-148° 以南的北太平洋)的春季 Oyashio 水分布情况。Oyashio 水的面积显示出年际变化和长期显著减少。研究认为,这些时间上的变化反映了北海道近海反气旋中尺度漩涡分布的变化,这些漩涡阻挡了向南侵入日本东部的 Oyashio 水。
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引用次数: 0
Disentangling mechanisms behind emerged sea surface temperature anomalies in Indonesian seas during El Niño years: insights from closed heat budget analysis 厘清厄尔尼诺年期间印度尼西亚海域海面温度异常现象背后的机制:封闭式热预算分析的启示
IF 2.3 4区 地球科学 Q4 OCEANOGRAPHY Pub Date : 2024-07-28 DOI: 10.1007/s10872-024-00728-6
Faisal Amri, Ahmed Eladawy, Joko Prihantono, Takashi Nakamura

A surface layer (upper 20 m depth) heat budget analysis, derived from a hindcast regional-scale ocean modeling experiment, was employed to examine the underlying mechanisms behind the emergence of sea surface temperature anomalies (SSTA) in the Indonesian seas during El Niño events over the 1995–2019 course. Prior to the emergence of warm SSTA, which typically appeared following the mature phase of El Niño and lasted for almost a year, apparent anomalous heat accumulation occurred for at least 2–4 months and peaked in conjunction with the climatic event. Further examination revealed possible east–west distinct dynamics in the heat budget variations within the region during El Niño years. The anomalous heat accumulation in the western part of Indonesian seas (Java Sea) was predominantly caused by modulation in the surface net heat flux. Whereas in the eastern part (Banda Sea), the ocean circulation also exerted important influence in addition to the surface net heat flux. The ocean circulation in the eastern Indonesian seas notably contributed to moderate the effect of surface net heat flux during El Niño growth. Moreover, the same ocean circulation was responsible for prolonging the anomalous heat accumulation in the eastern Indonesian seas from mature to decay phase of the El Niño, ultimately resulted in warmer SSTA than that in the western part. The study conducted here provides additional insights on how the Indonesian seas responded to the El Niño and further reaffirms the idea that the climatic event results in anomalous warming across the Indonesian seas.

根据后报区域尺度海洋建模实验得出的表层(上层 20 米深度)热量预算分析,用于研究 1995-2019 年厄尔尼诺现象期间印度尼西亚海域出现海面温度异常(SSTA)背后的基本机制。暖 SSTA 通常在厄尔尼诺现象成熟阶段出现,并持续近一年时间,在暖 SSTA 出现之前,明显的异常热量积累至少持续 2-4 个月,并与气候事件同时达到峰值。进一步研究发现,在厄尔尼诺年期间,该区域内的热量收支变化可能存在东西差异。印尼西部海域(爪哇海)的异常热量积累主要是由地表净热通量的变化引起的。而在东部海域(班达海),除地表净热流量外,海洋环流也产生了重要影响。在厄尔尼诺现象增长期间,印度尼西亚东部海域的海洋环流对减缓地表净热通量的影响起了显著作用。此外,同样的海洋环流也延长了厄尔尼诺现象从成熟期到衰减期在印度尼西亚东部海域的异常热量积累,最终导致 SSTA 暖于西部海域。这项研究为了解印度尼西亚海域如何应对厄尔尼诺现象提供了更多的信息,并进一步证实了这一气候事件导致整个印度尼西亚海域异常变暖的观点。
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引用次数: 0
Eastward extension jet driven by vorticity anomaly at the western boundary: characteristics and the effects of southward background flow 西部边界涡度异常驱动的向东扩展射流:特征和南向背景流的影响
IF 2.3 4区 地球科学 Q4 OCEANOGRAPHY Pub Date : 2024-07-23 DOI: 10.1007/s10872-024-00726-8
Haruka Onishi, Atsushi Kubokawa

In numerical models that adopt a no-slip boundary condition, a jet initially separates from the shore and flows eastward south of the inter-gyre boundary. This premature separation is caused by positive vorticity created by friction on the western boundary, which is paired with negative vorticity created by the conservation of the potential vorticity advected from the south. In this study, we propose a new model that includes vortex pair forcing in the western boundary region, where a vorticity structure causes separation and extension of the western boundary current (WBC) jet. Our model can separately treat flow that is locally driven by large-scale wind and the WBC extension jet driven by a vortex pair. We confirmed that our model could successfully replicate an extension jet prematurely separated from the western boundary for a wind-driven, two-layer quasi-geostrophic model. The dominant physical structure of the jet in our vortex pair forcing model differed in the upstream and downstream regions. In the upstream region, the intrusion of vortex pairs due to forcing is the dominant factor, while in the downstream region, the effect of eddies begins to manifest. We also examined the effects of a large-scale wind-driven background flow on the jet. When the background flow only contains an eastward component, the jet extends eastward. When the background flow contains a meridional component, this strongly affects the extended jet and can terminate the eastward jet structure.

在采用无滑动边界条件的数值模式中,喷流最初与海岸分离,并在地层间边界以南向东流动。这种过早分离是由西部边界摩擦产生的正涡度和从南部平流而来的潜在涡度守恒产生的负涡度造成的。在本研究中,我们提出了一个新模型,其中包括西部边界区域的涡对强迫,涡度结构会导致西部边界流(WBC)喷流的分离和延伸。我们的模型可以分别处理由大尺度风驱动的局部流动和由涡对驱动的西边界流扩展射流。我们证实,我们的模型可以成功地复制由风驱动的两层准地转模型中过早脱离西部边界的扩展射流。在我们的涡对强迫模型中,射流的主要物理结构在上游和下游区域有所不同。在上游区域,强制力导致的涡对侵入是主要因素,而在下游区域,涡的影响开始显现。我们还研究了大尺度风驱动背景流对射流的影响。当背景流只包含东向成分时,射流向东延伸。当背景流包含经向成分时,会对延伸的射流产生强烈影响,并可能终止向东的射流结构。
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引用次数: 0
Variations in the Central Mode Water in the North Pacific as a manifestation of the Pacific Decadal Oscillation 北太平洋中央模式水的变化是太平洋十年涛动的一种表现形式
IF 2.3 4区 地球科学 Q4 OCEANOGRAPHY Pub Date : 2024-07-03 DOI: 10.1007/s10872-024-00725-9
Iwasaka Naoto, Fumiaki Kobashi, Yoshimi Kawai

The North Pacific Central Mode Water (CMW) is examined from the viewpoint of its volume variations. The volume of the CMW layers thicker than (150 m) is used as an index of CMW variations, which successfully represents the year-to-year and decadal variations in the CMW volume. The CMW index shows the variation close to that of the Pacific Decadal Oscillation (PDO). The CMW variation is strongly tied with large-scale, dominant variations in sea surface temperature (SST), surface dynamic height (SDH), and sea surface height (SSH) anomalies in the North Pacific, with a significant correlation with the PDO. Year-to-year and decadal variations of CMW volume in May to July are significantly correlated with the wintertime Aleutian Low and 500(hPa) geopotential height variations, which indicates that the Aleutian Low induces the eastward extension/retreat of the strong winter westerlies and resultant net surface heat flux anomaly over the CMW distribution region. Thus, the CMW volume variation can be regarded as a significant manifestation of the PDO. The SST, SDH, and SSH anomalies are associated with the surface cooling in the northern sector of the CMW distribution region. On the other hand, the SDH and SSH anomalies throughout a year and the SST anomaly in the cold season in the southeastern sector of the CMW region are formed due to the heaving of isopycnal surfaces in the subsurface layer above the CMW in response to its volume variations.

从体积变化的角度研究了北太平洋中央模式水(CMW)。用厚度大于(150 米)的中模水层的体积作为中模水变化指数,成功地表示了中模水体积的年际和旬际变化。CMW指数的变化接近于太平洋十年涛动(PDO)的变化。CMW 的变化与北太平洋海面温度(SST)、海面动态高度(SDH)和海面高度(SSH)异常的大尺度主导变化密切相关,与 PDO 有显著的相关性。5-7月CMW量的年际和旬际变化与冬季阿留申低纬度和500(hPa)位势高度变化显著相关,这表明阿留申低纬度诱导了冬季强西风的东伸/后退,并由此导致CMW分布区的净表面热通量异常。因此,CMW 量变可视为 PDO 的重要表现。SST 、SDH 和 SSH 的异常与 CMW 分布区北部的地表冷却有关。另一方面,CMW 区域东南部全年的 SDH 和 SSH 异常以及寒冷季节的 SST 异常则是由于 CMW 上方次表层的等压面随 CMW 体积变化而翻腾形成的。
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引用次数: 0
Role of Japan Sea Throughflow in the spatial variability of the long-term sea surface temperature trend 日本海贯通流在海面温度长期趋势的空间变化中的作用
IF 2.3 4区 地球科学 Q2 Earth and Planetary Sciences Pub Date : 2024-05-23 DOI: 10.1007/s10872-024-00723-x
Hiromi Matsuura, S. Kida
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引用次数: 0
Long-term observation of the Soya Warm Current using HF ocean radars: relationship between the Soya Warm Current variability and the sea level anomalies in the Soya/La Perouse Strait 利用高频海洋雷达长期观测索亚暖流:索亚暖流变化与索亚/拉佩鲁斯海峡海平面异常之间的关系
IF 2.3 4区 地球科学 Q2 Earth and Planetary Sciences Pub Date : 2024-05-23 DOI: 10.1007/s10872-024-00724-w
N. Ebuchi, Y. Fukamachi, Kay I. Ohshima, H. Mitsudera, Jun Nishioka, Toru Takatsuka, K. Ono, Masao Ishikawa, Takaharu Daibo, K. Shirasawa, M. Wakatsuchi
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引用次数: 0
期刊
Journal of Oceanography
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