ORCID Profile
0000-0003-2886-7282
Current Organisation
Japan Agency for Marine-Earth Science and Technology
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Publisher: Royal Society of Chemistry (RSC)
Date: 08-2014
DOI: 10.1039/C4CE90109F
Publisher: Springer Science and Business Media LLC
Date: 09-08-2017
DOI: 10.1038/S41598-017-07680-0
Abstract: Marine calcifying organisms, such as stony corals, are under threat by rapid ocean acidification (OA) arising from the oceanic uptake of anthropogenic CO 2 . To better understand how organisms and ecosystems will adapt to or be damaged by the resulting environmental changes, field observations are crucial. Here, we show clear evidence, based on boron isotopic ratio (δ 11 B) measurements, that OA is affecting the pH of the calcification fluid (pH CF ) in Porites corals within the western North Pacific Subtropical Gyre at two separate locations, Chichijima Island (Ogasawara Archipelago) and Kikaijima Island. Corals from each location have displayed a rapid decline in δ 11 B since 1960. A comparison with the pH of the ambient seawater (pH SW ) near these islands, estimated from a large number of shipboard measurements of seawater CO 2 chemistry and atmospheric CO 2 , indicates that pH CF is sensitive to changes in pH SW. This suggests that the calcification fluid of corals will become less supersaturated with respect to aragonite by the middle of this century (pH CF = ~8.3 when pH SW = ~8.0 in 2050), earlier than previously expected, despite the pH CF -upregulating mechanism of corals.
Publisher: Springer Science and Business Media LLC
Date: 25-09-2019
DOI: 10.1038/S41598-019-49739-0
Abstract: The ocean may have played a central role in the atmospheric p CO 2 rise during the last deglaciation. However, evidence on where carbon was exchanged between the ocean and the atmosphere in this period is still lacking, h ering our understanding of global carbon cycle on glacial–interglacial timescales. Here we report a new surface seawater p CO 2 reconstruction for the western equatorial Pacific Ocean based on boron isotope analysis—a seawater p CO 2 proxy—using two species of near-surface dwelling foraminifera from the same marine sediment core. The results indicate that the region remained a modest CO 2 sink throughout the last deglaciation.
Publisher: Springer Science and Business Media LLC
Date: 11-06-2014
DOI: 10.1038/SREP05261
Abstract: While biogeochemical and physical processes in the Southern Ocean are thought to be central to atmospheric CO 2 rise during the last deglaciation, the role of the equatorial Pacific, where the largest CO 2 source exists at present, remains largely unconstrained. Here we present seawater pH and pCO 2 variations from fossil Porites corals in the mid equatorial Pacific offshore Tahiti based on a newly calibrated boron isotope paleo-pH proxy. Our new data, together with recalibrated existing data, indicate that a significant pCO 2 increase (pH decrease), accompanied by anomalously large marine 14 C reservoir ages, occurred following not only the Younger Dryas, but also Heinrich Stadial 1. These findings indicate an expanded zone of equatorial upwelling and resultant CO 2 emission, which may be derived from higher subsurface dissolved inorganic carbon concentration.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 06-12-2013
Abstract: The 2011 M w 9.0 Tohoku-Oki earthquake and tsunami were remarkable in many regards, including the rupturing of shallow trench sediments with huge associated slip (see the Perspective by Wang and Kinoshita ). The Japan Trench Fast Drilling Project rapid response drilling expedition sought to s le and monitor the fault zone directly through a series of boreholes. Chester et al. (p. 1208 ) describe the structure and composition of the thin fault zone, which is predominately comprised of weak clay-rich sediments. Using these same fault-zone materials, Ujiie et al. (p. 1211 ) performed high-velocity frictional experiments to determine the physical controls on the large slip that occurred during the earthquake. Finally, Fulton et al. (p. 1214 ) measured in situ temperature anomalies across the fault zone for 9 months, establishing a baseline for frictional resistance and stress during and following the earthquake.
Publisher: Wiley
Date: 2021
DOI: 10.1111/IAR.12423
Abstract: Hydrothermal circulation beneath the spreading axis plays a significant role in the exchange of energy and mass between the solid Earth and the oceans. Deep‐seated hydrothermal circulation down to the crust/mantle boundary in the fast‐spreading axis has been introduced by a number of studies regarding geological investigations and numerical models. In order to assess a reaction between hydrothermal fluid and host rock around the crust/mantle boundary, we conducted bulk trace element and Sr isotope analyses with a series of in situ investigations for crustal anorthosite, a reaction product between hydrothermal fluid and gabbro in the lowermost crustal section along Wadi Fizh, northern Oman ophiolite. In addition, we conducted titanite U–Pb isotope analyses to evaluate timing of the crustal anorthosite formation in the framework of the evolutional process of the Oman ophiolite. We estimated the formation age of the crustal anorthosite at 97.5 Ma ± 5.0 Ma, overlapping with the timing of the crust formation in the paleo spreading axis. The crustal anorthosite shows high‐Th/U ratio (~2.5) and high‐initial 87 Sr/ 86 Sr ratio (0.7050) due to seawater‐derived hydrothermal fluid ingress into the precursor gabbro. With using analytical technique of micro‐excavation at cryo‐temperature, we detected Cl from a few micrometer‐sized inclusion of aqueous fluid and chromite grains. The solubility of Cr was enhanced by complexation reactions with Cl in the hydrothermal fluid. Regarding reconstructed three‐dimensional mass distribution of the inclusion and chromite composition, maximum Cr content of parental fluid was estimated at ~69 000 μg/g. The exceptionally high‐Cr content was achieved locally by leaking of fluid and synchronous chromite crystallization during fluid entrapment. Presence of the deep‐seated hydrothermal circulation could be assigned to the segment end, where cold seawater penetrates into the lowermost crust and extract heat along widely spaced network‐like fluid channel.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 08-02-2013
Abstract: Large seismic events such as the 2011 magnitude 9.0 Tohoku-Oki earthquake can have profound effects not just on the severity of ground motion and tsunami generation, but also on the overall state of the crust in the surrounding regions. Lin et al. (p. 687 ) analyzed the stress 1 year after the Tohoku-Oki earthquake and compared it with the estimated stress state before the earthquake. In situ resistivity images were analyzed from three boreholes drilled into the crust across the plate interface where the earthquake occurred. Stress values indicate a nearly complete drop in stress following the earthquake such that the type of faulting above the plate boundary has changed substantially. These findings are consistent with observations that the sea floor moved nearly 50 meters during the earthquake.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 06-12-2013
Abstract: The 2011 M w 9.0 Tohoku-Oki earthquake and tsunami were remarkable in many regards, including the rupturing of shallow trench sediments with huge associated slip (see the Perspective by Wang and Kinoshita ). The Japan Trench Fast Drilling Project rapid response drilling expedition sought to s le and monitor the fault zone directly through a series of boreholes. Chester et al. (p. 1208 ) describe the structure and composition of the thin fault zone, which is predominately comprised of weak clay-rich sediments. Using these same fault-zone materials, Ujiie et al. (p. 1211 ) performed high-velocity frictional experiments to determine the physical controls on the large slip that occurred during the earthquake. Finally, Fulton et al. (p. 1214 ) measured in situ temperature anomalies across the fault zone for 9 months, establishing a baseline for frictional resistance and stress during and following the earthquake.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 06-12-2013
Abstract: The 2011 M w 9.0 Tohoku-Oki earthquake and tsunami were remarkable in many regards, including the rupturing of shallow trench sediments with huge associated slip (see the Perspective by Wang and Kinoshita ). The Japan Trench Fast Drilling Project rapid response drilling expedition sought to s le and monitor the fault zone directly through a series of boreholes. Chester et al. (p. 1208 ) describe the structure and composition of the thin fault zone, which is predominately comprised of weak clay-rich sediments. Using these same fault-zone materials, Ujiie et al. (p. 1211 ) performed high-velocity frictional experiments to determine the physical controls on the large slip that occurred during the earthquake. Finally, Fulton et al. (p. 1214 ) measured in situ temperature anomalies across the fault zone for 9 months, establishing a baseline for frictional resistance and stress during and following the earthquake.
Location: No location found
Location: No location found
Location: United States of America
No related grants have been discovered for Tsuyoshi Ishikawa.