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21.
Atoll island vulnerability to flooding and inundation revealed by historical reconstruction: Fongafale Islet, Funafuti Atoll, Tuvalu 总被引:1,自引:1,他引:0
Hiroya Yamano Hajime Kayanne Toru Yamaguchi Yuji Kuwahara Hiromune Yokoki Hiroto Shimazaki Masashi Chikamori 《Global and Planetary Change》2007,57(3-4):407-416
The reef islands formed on coral atolls are generally small, low, and flat, with elevations of only a few meters. These islands are thus highly vulnerable to elevated sea levels caused by extreme events and global warming. Such vulnerability was recently evidenced at Fongafale Islet, the capital of Tuvalu, when it flooded during accelerated spring high tides possibly related to sea level rise caused by global warming. Many factors, not only environmental but also economic and social, determine the vulnerability of an island to sea level rise. In this study, we used data spanning 108 yrs to reconstruct changes in topography, land use/cover, population, and the distribution of buildings at Fongafale Islet. The results indicate that the vulnerability of Fongafale Islet relates to its original landform characteristics: the central part of the island was formerly dominated by swampland that flooded at high tides. Fongafale Islet experienced greater population in-migration and centralization beginning in the 1970s following the independence of Tuvalu and Kiribati. Migrants were also responding to declines in overseas mining operations and limited options for paid employment. As the population increased, construction took place in vulnerable swampland areas. Our results clearly demonstrate that examinations of global environmental issues should focus on characteristics specific to the region of interest. These characteristics should be specified using historical reconstruction to understand and address the vulnerability of an area to global environmental changes. 相似文献
22.
Kazuaki Okamoto Hironao Shinjoe Ikuo Katayama Kentaro Terada Yuji Sano Simon Johnson 《地学学报》2004,16(2):81-89
In order to decipher the origin of eclogite in the high‐P/T Sanbagawa metamorphic belt, SHRIMP U–Pb ages of zircons from quartz‐bearing eclogite and associated quartz‐rich rock (metasandstone) were determined. One zircon core of the quartz‐rich rock yields an extremely old provenance age of 1899 ± 79 Ma, suggesting that the core is of detrital origin. Eight other core ages are in the 148–134 Ma range, and are older than the estimated age for trench sedimentation as indicated by the youngest radiolarian fossil age of 139–135 Ma from the Sanbagawa schists. Ages of metamorphic zircon rims (132–112 Ma) from the quartz‐rich rock are consistent with metamorphic zircon ages from the quartz‐bearing eclogite, indicating that eclogite facies metamorphism peaked at 120–110 Ma. These new data are consistent with both the Iratsu eclogite body and surrounding highest‐grade Sanbagawa schists undergoing coeval subduction‐zone metamorphism, and subsequent re‐equilibration under epidote amphibolite facies conditions during exhumation. 相似文献
23.
The atmospheric stable boundary layer (SBL) with a low-level jet is simulated experimentally using a thermally stratified
wind tunnel. The turbulence structure and flow characteristics are investigated by simultaneous measurements of velocity and
temperature fluctuations and by flow visualization. Attention is focused on the effect of strong wind shear due to a low-level
jet on stratified boundary layers with strong stability. Occasional bursting of turbulence in the lower portion of the boundary
layer can be found in the SBL with strong stability. This bursting originates aloft away from the surface and transports fluid
with relatively low velocity and temperature upward and fluid with relatively high velocity and temperature downward. Furthermore,
the relationship between the occurrence of turbulence bursting and the local gradient Richardson number (Ri) is investigated.
The Ri becomes larger than the critical Ri, Ricr = 0.25, in quiescent periods. On the other hand, the Ri number becomes smaller than Ricr during bursting events. 相似文献
24.
Xuan Chen Masatoshi Aoki Shangxun Zhang Jinhua Zhang Susumu Nozoe Daisuke Komori Akinori Takami Shiro Hatakeyama 《Journal of Atmospheric Chemistry》2008,60(1):37-49
In order to study the concentrations of hydrogen peroxide (H2O2) and the factors controlling its concentrations, we monitored concentrations of H2O2 and other gases such as sulfur dioxide, ozone, and NO
x
as well as meteorological factors such as air temperature, relative humidity, and wind direction/speed during eight measurement
periods from 2000 to 2002 in a Japanese red pine forest in Japan. The H2O2 concentrations ranged from below 0.01 to 1.64 ppb, and analysis of the diurnal variation in H2O2 concentration showed high concentrations around noon, and low concentrations in the morning and late afternoon. The H2O2 concentrations were high in early summer, when O3 concentration, temperature, and solar radiation were high, and were low in fall, when O3 concentration, temperature, and solar radiation were low. We propose that O3 concentration affects the production of H2O2 in the monitored region during the period under study, but that high H2O2 concentrations were sometimes caused by the transport of polluted air from urban regions. H2O2 concentrations decreased remarkably when SO2 concentrations increased by transported volcanic emission on Miyake Island. In the absence of the effects of SO2, H2O2 concentrations increased with increasing O3 concentration and temperature. 相似文献
25.
Takanori Shimizu Koji Tamai Ikuhiro Hosoda Shoji Noguchi Yuji Kominami Toshio Abe Kenzo Kitamura Ushio Kurokawa Delphis F. Levia Tayoko Kubota Naoki Kabeya Shin'ichi Iida Tatsuhiko Nobuhiro Shinji Sawano Sho Iwagami Akira Shimizu Yoshio Tsuboyama 《水文研究》2021,35(10):e14376
This data note introduces a database of long-term daily total precipitation and stream discharge data for seven forested watersheds in Japan that have been continuously monitored by the Forestry and Forest Products Research Institute. Three of the watersheds started data collection in the 1930s. Forest cover across the sites ranges from cool to warm temperate regions with the latitude spanning from 31 to 44° N and annual precipitation ranging from 1200 to 3000 mm yr−1. The effects of vegetation change via clearcutting, thinning and forest fire (among other stressors) on stream discharge can be analysed from the long-term observation sites. Moreover, this multi-site dataset allows for inter- and intra-site comparisons of annual water loss (difference of annual precipitation and stream discharge). These long-term datasets can provide comprehensive insights into the effects of climate change and other stressors on forested ecosystems, not only in Japan but across a spectrum of forest types, if combined with other long-term records from other forested watersheds across the world. 相似文献
26.
The present study examines the petrology and geochemistry of the Early Paleozoic Motai serpentinites, the South Kitakami Belt, northeast Japan, to reveal the subduction processes and tectonics in the convergent margin of the Early Paleozoic proto-East Asian continent. Protoliths of the serpentinites are estimated to be harzburgite to dunite based on the observed amounts of bastite (orthopyroxene pseudomorph). Relic chromian spinel Cr# [=Cr/(Cr + Al)] increases with decreasing amount of bastite. The compositional range of chromian spinel is similar to that found in the Mariana forearc serpentinites. This fact suggests that the protoliths of the serpentinites are depleted mantle peridotites developed beneath the forearc regions of a subduction zone. The Motai serpentinites are divided into two types, namely, Types 1 and 2 serpentinites; the former are characterized by fine-grained antigorite and lack of olivine, and the latter have coarse-grained antigorite and inclusion-rich olivine. Ca-amphibole occurs as isolated crystals or vein-like aggregates in the Type 1 serpentinites and as needle-shaped minerals in the Type 2 serpentinites. Ca-amphibole of the Type 1 serpentinites is more enriched in LILEs and LREEs, suggesting the influence of hydrous fluids derived from slabs. By contrast, the mineral assemblage, mineral chemistry, and field distribution of the Type 2 serpentinites reflect the thermal effect of contact metamorphism by Cretaceous granite. The Ca-amphibole of the Type 1 serpentinites is different from that of the Hayachine–Miyamori Ophiolite in terms of origin; the latter was formed by the infiltration of melts produced in an Early Paleozoic arc–backarc system. Chemical characteristics of the Ca-amphibole in the ultramafic rocks in the South Kitakami Belt reflect the tectonics of an Early Paleozoic mantle wedge, and the formation of the Motai metamorphic rocks in the forearc region of the Hayachine–Miyamori subduction zone system, which occurred at the Early Paleozoic proto-East Asian continental margin. 相似文献
27.
Hidenori Terasaki Keisuke Nishida Satoru Urakawa Yusaku Takubo Soma Kuwabara Yuta Shimoyama Kentaro Uesugi Yoshio Kono Akihisa Takeuchi Yoshio Suzuki Yuji Higo Tadashi Kondo 《Comptes Rendus Geoscience》2019,351(2-3):163-170
A new experimental setup for simultaneous P-wave velocity (VP) and density (ρ) measurements for liquid alloys is developed using ultrasonic and X-ray absorption methods combined with X-ray tomography at high pressures and high temperatures. The new setup allows us to directly determine adiabatic bulk moduli (KS) and to discuss the correlation between the VP and ρ of the liquid sample. We measured VP and ρ of liquid Ni68S32 up to 5.6 GPa and 1045 K using this technique. The effect of pressure on the VP and ρ values of liquid Ni68S32 is similar to that of liquid Fe57S43. (Both compositions correspond to near-eutectic ones.) The obtained KS values are well fitted to the finite strain equation with a value (KS at ambient pressure) of 31.1 GPa and a dKS/dP value of 8.44. The measured VP was found to increase linearly with increasing ρ, as approximated by the relationship: VP [m/s] = 1.29 ρ [kg/m3] – 5726, suggesting that liquid Ni–S follows an empirical linear relationship, Birch's law. The dVP/dρ slope is similar between Ni68S32 and Fe57S43 liquids, while the VP–ρ plot of liquid Ni–S is markedly different from that of liquid Fe–S, which indicates that the effect of Ni on Birch's law is important for understanding the VP–ρ relation of planetary and Moon's molten cores. 相似文献
28.
Kojiro?ShimadaEmail author Xiaoyang?Yang Yushi?Araki Ayako?Yoshino Akinori?Takami Xuan?Chen Fan?Meng Shiro?Hatakeyama 《Journal of Atmospheric Chemistry》2018,75(2):123-139
To determine the effects of long-range transport of aerosols from an upwind area in East Asia to a downwind area in Japan, we chemically analyzed aerosols collected simultaneously on Tuoji Island (Shandong Province, China), Fukue Island (Nagasaki Prefecture, Japan), and Cape Hedo (Okinawa Prefecture, Japan). We focused on changes in the metallic composition of PM2.5 aerosols during long-range transport. The average mass concentrations of PM2.5 at the three sites decreased in the order Tuoji Island > Fukue Island ≈ Cape Hedo (48.3 ± 4.5, 13.9 ± 1.5, and 13.2 ± 0.9 μg/m3, respectively). The fraction of coarse particles in total suspended particles estimated by (1–PM2.5/TSP) was highest on Cape Hedo, indicating that the contribution of sea salts was increased by long-range transport of the aerosols over the ocean. Enrichment factor analysis revealed that at all three sites, Al, K, Ca, Mn, Fe, Co, Sr, and Ba originated from soil; whereas Cr, Ni, Cu, Zn, As, Mo, Ag, Cd, Sn, Sb, Tl, and P appeared to be of anthropogenic origin. Na was the most abundant element on Cape Hedo, indicating the addition of sea salts during aerosol transport. The V concentration was highest at Fukue Island, which was ascribed to V emission from ships. Sixty-one percent of the V on Fukue Island and 62% of the V on Cape Hedo were determined to have originated from ships, implicating of data obtained on dates during which backward trajectory analysis indicated that the same air mass passed over Tuoji Island, Fukue Island, and Cape Hedo in that order. 相似文献
29.
30.
Long-Term Variations of Potential Temperature and Dissolved Oxygen of the Japan Sea Proper Water 总被引:4,自引:0,他引:4
Observed potential temperatures and concentrations of dissolved oxygen are analyzed to elucidate their variations during the
period from 1958 to 1996 at Stn. P (37°43′ N, 134°43′ E) and from 1965 to 1996 at Stn. H (40°30′ N, 137°40′ E) in the Japan
Sea. At Stn. P, increases of the potential temperature for the period are found below 800 m depth with the largest value of
0.16 ± 0.09°C per century at 800 m depth. At Stn. H, the potential temperature increased below 500 m depth. The increase rate
has the largest value of 0.50 ± 0.18°C per century at 500 m depth and it is 0.30 ± 0.09°C per century at 800 m depth. The
concentrations of dissolved oxygen increased around 800 m depth at Stn. P. At Stn. H, they increased above 800 m depth. On
the other hand, they decreased below 1200 m depth at both stations. The layer of the dissolved oxygen minimum has deepened
in these decades. These features appearing in the distributions of temperature and dissolved oxygen are successively simulated
by a vertical one-dimensional advection-diffusion model including consumption of dissolved oxygen and termination of the deep
water supply. These results suggest that the supply of the Japan Sea Proper Water into the deep layer, which is cold and rich
in dissolved oxygen, has been decreasing for the last four decades.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献