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Article
Kyushu Univ. Production Kyushu Univ. Production
Cover image of SC-Triggered 1.6mHz Waves Including an Interval with Latitude-Dependent Phase Shift, Observed by the SuperDARN Hokkaido East Radar in Mid Latitudes: Possible Global Magnetospheric Cavity-Mode Waves and Their Field-Line Resonance with Poloidal Alfven-Mode Waves
Kawano, Hideaki; 河野, 英昭; Yukimatsu, Akira Sessai ... [et al.]
Publication info: Memoirs of the Faculty of Science, Kyushu University. Series D, Earth and planetary sciences. 34, (1), pp. 1-15, 2016-11-21. Faculty of Science, Kyushu University
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Abstract: In this paper we present a new kind of wave event found in the ground/sea backscattered data of the SuperDARN Hokkaido East radar, located in the mid-latitude area at the AACGM latitude (longitude) of 36.5° (214.7°). The wave event started at the time of an SC at ~09:50 UT on Aug 19, 2009, and continued for about an hour until ~10:50 UT: This relatively short-living wave event, probably triggered by the SC, could be classified as a type different from the typical type seen in the ground/sea backscattered data of SuperDARN radars, i.e., waves which start without a clearly identifiable trigger and continue for a long time (4~5 hours) (e.g., Ponomarenko et al. 2003). Comparisons with ground magnetometer data suggest that the major part of this event consisted of global magnetospheric cavity-mode waves whose typical frequency is in the order of 1mHz (e.g., Kivelson and Southwood 1985, 1986). In addition, in the interval of 10:26~10:42UT which was embedded in the above-stated one-hour interval, we have found the amplitude and phase pattern typically observed when the field-line resonance (FLR) takes place; this pattern is found for the first time in the mid-latitude ground/sea backscattered data, and suggests excitation of poloidal Alfven-mode field-line eigenoscillations during this interval. Read more
2.
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Kyushu Univ. Production Kyushu Univ. Production
Cover image of Revision of the Dissolution Kinetics of Aggregated Settling Particles
Akagi, Tasuku ; 赤木, 右
Publication info: Memoirs of the Faculty of Science, Kyushu University. Series D, Earth and planetary sciences. 33, (1), pp. 1-5, 2013-12. Faculty of Science, Kyushu University — 九州大学大学院理学研究院
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Abstract: The dissolution kinetics theory of settling particles, which was developed to express the elemental concentration variation as a function of diatom productivity, is revised to allow further consideration on the presence of voids. In this revision, the number of diatom frustules which form an aggregate is introduced as a basic variable to secure the rigidity of mathematical consideration, (unlike the previous paper, where productivity is employed as one of the basic variations - Akagi et al., 2011). No exchange of elements is assumed between seawater surrounding the aggregates and seawater in the voids of the aggregates. It is shown that the presence of voids reduces the settling velocity, but does not affect the dissolution/alteration behavior of settling particles as long as the particles are collected at a certain depth. Read more
3.
Article
Kyushu Univ. Production Kyushu Univ. Production
Cover image of Alkaline leaching characteristics of biogenic opal in IODP drilled cores from the Bering Sea
Iwasaki, Shinya; Takahashi, Kozo; Kanematsu, Yoshiyuki ... [et al.]
Publication info: Memoirs of the Faculty of Science, Kyushu University. Series D, Earth and planetary sciences. 32, (4), pp. 39-44, 2012-03-01. Faculty of Science, Kyushu University — 九州大学大学院理学研究院
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Abstract: Leaching characteristics of biogenic opal in alkaline solutions were studied for Bering Sea sediment samples from the cores obtained during Integrated Ocean Drilling Program (IODP) Expedition 323. Generally, biogenic opal content is measured after alkaline leaching using Na2CO3 solution. Biogenic opal in some sediment samples could not be completely leached by Na2CO3 solutions, particularly in the deeper sections depending on sites: below the depth of ca. 122 m (CCSF-A) with 1.1 Ma at Site U1341 and ca. 211 m (CCSF-A) with 0.8 Ma at Site U1343. Strong alkaline 2M and 4M NaOH solutions were used instead of the standard Na2CO3 solution. As a result of the time-series leaching analysis, silicon contribution rates from clay minerals and other detrital grains were estimated in each of the methods employing two different concentrations of NaOH solutions. This made possible to correct for silicon contribution of clay minerals and other detrital grains. Read more
4.
Article
Kyushu Univ. Production Kyushu Univ. Production
Cover image of Long-term observations of iron-oxyhydroxide-rich reddish-brown water in Nagahama Bay, Satsuma Iwo-Jima Island, Kagoshima, Japan
Ueshiba, Takuya; Kiyokawa, Shoichi; 上芝, 卓也 ... [et al.]
Publication info: Memoirs of the Faculty of Science, Kyushu University. Series D, Earth and planetary sciences. 32, (4), pp. 45-52, 2012-03-01. Faculty of Science, Kyushu University — 九州大学大学院理学研究院
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Abstract: Nagahama Bay, in the southern part of Satsuma Iwo-Jima Island (38 km south of Kyushu Island, Japan), contains an active hydrothermal system along the beach and at the fishing port. The construction of a breakwater around the bay has resulted in a semi-closed body of water with an entrance from the south. From this bay, reddish-brown seawater enriched in iron-oxyhydroxides is discharged to the Pacific Ocean constantly. The greenish-blue seawater of the Pacific Ocean occasionally enters the bay and mixes with the reddish-brown water. The daily flow pattern of the reddish-brown seawater in the bay has been monitored previously during storms and periods of heavy rain. However, greenish-blue seawater is sometimes observed in the bay at low tide. Therefore, we monitored the color of the sea surface and water at the seafloor for periods of 26 and 12 days during spring and autumn, respectively, using automatic still cameras to compare the water color with meteorological data recorded at Iwo-Jima Island. The results show that a southerly wind is associated with the trapping of reddish-brown surface water in the bay. In contrast, a northerly wind brings greenish-blue water from the open ocean into the bay, even at low tide. The factors that control the color of seawater in Nagahama Bay are not only the tidal cycle and storm waves, but also wind speed and direction. Read more
5.
Article
Kyushu Univ. Production Kyushu Univ. Production
Cover image of Museum archives of the 19 years long time-series sediment trap samples collected at central subarctic Pacific Station SA and Bering Sea Station AB during 1990-2010
Takahashi, Kozo; 高橋, 孝三; Asahi, Hirofumi ... [et al.]
Publication info: Memoirs of the Faculty of Science, Kyushu University. Series D, Earth and planetary sciences. 32, (4), pp. 1-39, 2012-03-01. Faculty of Science, Kyushu University — 九州大学大学院理学研究院
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Abstract: PARLUX type sediment traps were moored at 600 m above the sea-floor at Station SA (water depth: 5,406m) in the central subarctic Pacific and at Station AB (water depth: 3,788m) in the Aleutian Basin of the Bering Sea. The time-series flux samples were obtained during 1990-2010 for nineteen years. This allowed us to characterize primary fluxes of biogenic particles primarily produced near the surface layers of the deep water columns as well as to decipher the environmental variations associated with climate changes. Based on the samples various studies were conducted thus far, including the followings types: quantitative plankton taxon-numerical studies on diatoms, silicoflagellates, radiolarians, coccolithophores and planktic foraminfers; and geochemical aspects of chemical compounds such as biogenic opal, calcium carbonate and hexosamine as well as elements such as rare earth elements. Such studies published thus far are cited in this paper. The sediment trap samples are archived at the Kyushu University Museum for permanent preservation. The grand total of the currently archived samples, including membrane filters and microslides for the two stations, is 3,552. The details of the samples are described herein and spreadsheet tables of the archives will also be electronically published by the Museum. This makes it possible for future scientists and students, who need to examine the relevant sediment trap samples, to access them properly. Read more
6.
Article
Kyushu Univ. Production Kyushu Univ. Production
Cover image of Chemosynthetic fossil molluscan faunas from the Neogene Taishu Group, distributed in Tsushima Islands, Nagasaki Prefecture, the southwest Japan
Ninomiya, Takashi ; 二宮, 崇
Publication info: Memoirs of the Faculty of Science, Kyushu University. Series D, Earth and planetary sciences. 32, (3), pp. 11-26, 2011-03-10. Faculty of Science, Kyushu University
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Abstract: The middle of the Neogene Taishu Group, distributed in Tsushima Islands, Nagasaki Prefecture, the southwest Japan, is considered to include the authigenic carbonates originated from cold-seep and the chemosynthetic molluscan faunas deposited in deep sea environment of greater than 500 m depth. In this study, the author examined classification of the bivalves occurred in the middle of the Taishu Group. Consequently, the molluscan faunas are assigned into the following ten species belonging to seven genera: Bathymodiolus sp., Adipicola sp., Calyptogena spp., Acharax spp., Acila sp., Nuculana sp., and Yoldia sp. Read more
7.
Article
Kyushu Univ. Production Kyushu Univ. Production
Cover image of Cell size variation of Anoplosolenia brasiliensis(calcareous nannoplankton) in the central equatorial Pacific Ocean
Tsutsui, Hideto; Takahashi, Kozo; 筒井, 英人 ... [et al.]
Publication info: Memoirs of the Faculty of Science, Kyushu University. Series D, Earth and planetary sciences. 32, (3), pp. 27-38, 2011-03-10. Faculty of Science, Kyushu University
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Abstract: A morphometric analysis on Anoplosolenia brasiliensis(calcareous nannoplankton) was conducted employing samples obtained from 0 to 120 m water depths in the central equatorial Pacific Ocean along the equator ranging from 166.3°E to 170.1°W. Measured cell length of A. brasiliensis showed the minimum of 39 μm to the maximum of 165 μm. The cell width ranged from the minimum of 1 μm to the maximum of 10 μm. Measured cell volumes ranged from the minimum of 28.3 μm3 to the maximum of 2,741 μm3. In addition, length/width ratios ranged from the minimum of 6.8 to the maximum of 37.5. The cell size of this taxon is very large compared to that of other calcareous nannoplankton taxa such as Emiliania huxleyi. Related factors for such a large cell size appears to be: (1)population density of the own taxon; (2)ambient temperature; (3)ambient dissolved oxygen concentration; and (4)other phytoplankton population density such as that of E. huxleyi. The life adaptation of A. brasiliensis is interpreted as fundamentally pursuing a K-strategy, but this taxon is also pursuing an r-strategy when appropriate situation arises. The population density of this taxon may be related to ambient nutrient concentrations, intricate balance among several species of nutrients, and competitions with other coccolithophore taxa such as E. huxleyi. Read more
8.
Article
Kyushu Univ. Production Kyushu Univ. Production
Cover image of Identification of full-substorm onset from ground-magnetometer data by singular value transformation
Tokunaga, Terumasa; Yumoto, Kiyohumi; Uozumi, Teiji ... [et al.]
Publication info: Memoirs of the Faculty of Science, Kyushu University. Series D, Earth and planetary sciences. 32, (3), pp. 63-73, 2011-03-10. Faculty of Science, Kyushu University
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Abstract: Pi 2 magnetic pulsations observed on the ground are a good indicator of the auroral breakup. However, they have not only corresponding full-substorm onsets but also most pseudobreakups. Another well-known substorm related phenomenon observed on the ground is positive bays. In order to identify full-substorm onsets from ground-magnetometer data, we developed a new algorithm based on "Singular Spectrum Analysis(SSA)". The algorithm enables us to screen Pi 2 pulsations accompanied by the magnetic positive bay. We applied proposed algorithm to ground-magnetometer data and compared to the obtained results with Polar/UVI data. As a result, we succeeded in identifying 62% of the full-substorm onsets from ground-magnetometer data obtained in the nighttime sector between 21 and 03LT. Read more
9.
Article
Kyushu Univ. Production Kyushu Univ. Production
Cover image of Occurrences of radiolarian biostratigraphic markers Lychnocanoma nipponica sakaii and Amphimelissa setosa in Core YK07-12 PC3B from the Okhotsk Sea
Ikenoue, Takahito; 池上, 隆仁; Takahashi, Kozo ... [et al.]
Publication info: Memoirs of the Faculty of Science, Kyushu University. Series D, Earth and planetary sciences. 32, (3), pp. 1-10, 2011-03-10. Faculty of Science, Kyushu University
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Abstract: Core YK07-12 PC03B obtained from the central Okhotsk plain(52°36'N, 150°08'E ; water depth: 1049 m) was analyzed every 5 cm, focusing on two radiolarian biostratigraphic markers in the late Pleistocene: Lychnocanoma nipponica sakaii and Amphimelissa setosa. The last occurrence(LO) datum of A. setosa at 67 ka conformed with those of the LO of the previously published studies. However, the LO of L. nipponica sakaii at 25 ka was off set and significantly younger than those published in the previous studies in the North Pacific and the marginal seas. We introduce herein the conceptual use of the last common occurrence(LCO) of L. nipponica sakaii as the LCO conforms with the LO of this taxon published elsewhere and hence more reliable, especially out side of the northern part of the central Okhotsk plain. The LCO of L. nipponica sakaii is 46 ka, 21 kyrs older than the LO, but is approximately the same as the LOs published elsewhere. We postulate the LCO as a practical datum which can be compared with the data from out side of the studied region. As alternative explanations, the obtained significantly younger LO than the LOs of other studies from the out side of the study region may stem from the following two reasons. Because that the present study is specifically focused on the two biostratigraphic marker radiolarian taxa with details our microscopic counts are significantly greater than those performed in the previous studies. This may have caused the documentation of the LO with the rare microscopic counts on multiple microslides, which could have been missed had we counted only one microslide. It is also possible that the effect of bioturbation due to upward transport in the slow sedimentation rate regime caused the appearance of the rare specimens of L. nipponica sakaii well above the LCO. Read more
10.
Article
Kyushu Univ. Production Kyushu Univ. Production
Cover image of Distribution of polycystine Radiolaria, Phaeodaria and Acantharia in the Kuroshio Current off Shikoku Island and Tosa Bay during Cruise KT07-19 in August 2007
Onodera, Jonaotaro; 小野寺, 丈尚太郎; Okazaki, Yusuke ... [et al.]
Publication info: Memoirs of the Faculty of Science, Kyushu University. Series D, Earth and planetary sciences. 32, (3), pp. 39-61, 2011-03-10. Faculty of Science, Kyushu University
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Abstract: The occurrences of polycystine Radiolaria, Phaeodaria, and Acantharia are reported from plankton net samples, which were obtained in the transect covering from the Kuroshio Current off Shikoku Island to Tosa Bay during Cruise KT07-19 in August 2007. We employed 100 μm as the mesh size of the plankton nets, which was coarser than the mesh size of many recent radiolarian studies (e.g., 44 or 63 μm). The obtained specimens in the samples were categorized into 130 polycystine radiolarian, and 17 phaeodarian, and 3 acantharian taxa. The marked similarity of the polycystine radiolarian assemblages encountered in this study to those reported from the tropical and subtropical oceans in the literature clearly indicates the significant influence by the warm Kuroshio Current. Furthermore, the observed polycystine radiolarian assemblages are similar to those of the previous result from the same specific study area. However, the vertical distribution patterns of some of the major polycystine radiolarian and phaeodarian taxa are different from the previous results from the same region. The differences in vertical distribution may be primarily due to the differences in vertical water mass conditions due to different sampling seasons. In spite of the lengthy sample storage for seven months after the sampling in the shore laboratory, many acantharian specimens were still preserved and encountered in the laboratory census, representing the acantharian presence in the summer sea surface waters in the Kuroshio Current area. Read more