Total amount of oceanic excess CO2 taken from the North Pacific subpolar region     

Yutaka W. Watanabe  Yoshiyuki Takahashi  Takashi Kitao  Koh Harada 《Journal of Oceanography》1996,52(3):301-312

Concentrations of total carbonate, alkalinity and dissolved oxygen were obtained near the 1973 GEOSECS stations in the North Pacific subpolar region north of 40°N along 175°E between 1993 and 1994. A difference of excess CO₂ content between the GEOSECS and our expeditions was estimated. The maximum difference in water column inventory of excess CO₂ has increased by about 280 gC m^–2 above 2000 m depth which apparently means an uptake of excess CO₂ taken from air to sea during the last two decades. An averaged value of the annual flux of excess CO₂ at 75–1000 m depth was 8.63±2.01 gC m^–2yr^–1 in the North Pacific subpolar region. By introducing the annual flux of excess CO₂ into a two-box model for the North Pacific subpolar region, a penetration factor of excess CO₂ from air to sea was obtained to be 1.08×10^–2 gC m^–3ppm^–1 in the North Pacific subpolar region. Based on this factor, the surface concentration of excess CO₂ in the North Pacific subpolar region was estimated to be 68 mole I^–1, suggesting that the North Pacific subpolar region absorbed atmospheric excess CO₂ more than the saturated concentration of excess CO₂. Total amount of excess CO₂ taken from the North Pacific subpolar region by 1993 was estimated to be 36.2×10¹⁵ gC, which was equal to about one tenth of that released by human activities after the preindustrial era.  相似文献   

A Preliminary Study of Oceanic Bomb Radiocarbon Inventory in the North Pacific during the Last Two Decades     

Yutaka W. Watanabe  Tsuneo Ono  Koh Harada  Masao Fukasawa 《Journal of Oceanography》1999,55(6):705-716

Radiocarbon and total carbonate data were obtained near the 1973 GEOSECS stations in the North Pacific along 30°N and along 175°E between 1993 and 1994. In these stations, we estimated radiocarbon originating from atomic bomb tests using tritium, trichlorofluoromethane and silicate contents. The average penetration depth of bomb radiocarbon during the two decades has deepened from 900 m to 1300 m. Bomb radiocarbon inventories above the average value for the whole North Pacific were found widely in the western subtropical region around 30°N both in the 1970s and 1990s, and its area in the 1990s was broader than that in the 1970s. In most of the North Pacific, while the bomb radiocarbon has decreased above 25.4, the bomb radiocarbon flux below 25.4 was over 1 × 10¹² atom m^-2yr^-1 in the subtropical region around 30°N. In the tropical area south of 20°N, the bomb radiocarbon inventory below 25.4 increased from zero to over 10 × 10¹² atom m^-2 during the last three decades. These distributions suggest that the bomb radiocarbon removed from the surface is currently accumulated with bomb ¹⁴C flux of over 1 × 10¹² atom m^-2yr^-1 below 25.4 in the subtropical region, mainly by advection from the higher latitude, and that part of the accumulated bomb ¹⁴C gradually spread southward with about 30 years.  相似文献   

Air-Sea Gas Transfer Velocity in Stormy Winter Estimated from Radon Deficiency     

Hitoshi Kawabata  Hisashi Narita  Koh Harada  Shizuo Tsunogai  Masashi Kusakabe 《Journal of Oceanography》2003,59(5):651-661

Thirteen vertical profiles of ²²⁶Ra and ²²²Rn in the near-surface water were obtained in the western North Pacific in winter, and the gas transfer velocities across the air-sea interface were estimated. The transfer velocities found by applying a steady state model varied widely from 2.1 to 30.2 m day⁻¹ with a mean of 9.4 m day⁻¹. The mean value is almost 5 times higher than that in summer in other oceans, and the maximum value is a record high for world oceans. This is partly due to the inadequacy of the steady state model, which overestimates when stronger winds blow in more recent days than the ²²²Rn half-life of about 4 days. In fact, a strong low pressure zone passed through the station about 2 days earlier, which was one of the low pressure zones that with a period of develop once a week or so in the northwestern North Pacific in winter. Instead of steady-state removal, if half of the radon removal occurred sporadically every 7 days, and the last removal took place two days before the observation, the transfer velocity would be 26 m day⁻¹. Our mean transfer velocity, which is less than 20% different from the steady state value including both overestimated and underestimated values, 9.4 ± 4.8 m day⁻¹, seems to represent the mean state of this region in winter. This suggests that the gas exchange fluxes under extremely rough conditions in the open ocean are larger than those estimated by using a transfer velocity equation with a linear or quadratic relationship with wind speed. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Millennial-scale climatic and environmental oscillations in the Sea of Okhotsk in response to global changes during the last 190 Ka     

S. A. Gorbarenko  N. Harada  M. I. Malakhov  Yu. P. Vasilenko  A. A. Bosin  E. L. Gol’dberg 《Doklady Earth Sciences》2008,423(2):1410-1413

  相似文献   

2500年来艾比湖的环境演变信息   总被引：22，自引：9，他引：22  

阎顺  穆桂金  远藤邦彦  Nobuhiko Handa  Masao Uchida  Naomi Harada 《干旱区地理》2003,26(3):227-232

通过对艾比湖缘1，8m浅孔的沉积相和孢粉组合，结合14C测年资料分析。指出近2500年来艾比湖的沉积环境总体是比较稳定的，但由于气候波动引起艾比湖水位曾发生较明显的变化。约在公元前300～400年，是艾比湖面积缩小时期；约公元前300—公元300年，即东周末至西晋，是艾比湖水位较高时期；约公元300—1400年，即东晋至15世纪初，是艾比湖的高水位时期；约15世纪初至17世纪中是艾比湖的水位下降期，但水位比现代仍然高；约17世纪中至19世纪初的小冰期是艾比湖的水位上升期。研究还提供了历史时期湖泊的盐度变化和湖周发生大火的信息。  相似文献   

Field survey of the East Java earthquake and tsunami of June 3, 1994     

Yoshinobu Tsuji  Fumihiko Imamura  Hideo Matsutomi  Costas E. Synolakis  Puspito T. Nanang  Jumadi  Satoshi Harada  Se Sub Han  Ken'ichi Arai  Benjamin Cook 《Pure and Applied Geophysics》1995,144(3-4):839-854

A field survey of the June 3, 1994 East Java earthquake tsunami was conducted within three weeks, and the distributions of the seismic intensities, tsunami heights, and human and house damages were surveyed. The seismic intensities on the south coasts of Java and Bali Islands were small for an earthquake with magnitudeM 7.6. The earthquake caused no land damage. About 40 minutes after the main shock, a huge tsunami attacked the coasts, several villages in East Java Province were damaged severely, and 223 persons perished. At Pancer Village about 70 percent of the houses were swept away and 121 persons were killed by the tsunami. The relationship between tsunami heights and distances from the source shows that the Hatori's tsunami magnitude wasm=3, which seems to be larger for the earthquake magnitude. But we should not consider this an extraordinary event because it was pointed out byHatori (1994) that the magnitudes of tsunamis in the Indonesia-Philippine region generally exceed 1–2 grade larger than those of other regions.  相似文献   

Amino acid precursors in lunar fines: limits to the contribution of jet exhaust     

Sidney W. Fox  Kaoru Harada  P.E. Hare 《Geochimica et cosmochimica acta》1976,40(9):1069-1071

A sample of lunar fines collected at a maximum distance, 6.5 km, from the descent engine on Apollo 17 has been analyzed for total amino acids obtainable by hydrolysis of aqueous extracts. The minimum amounts of amino acids, calculated for a disc of 6 km radius are 10⁴–10⁵ times those which could be contributed by the lunar module jet exhaust, on the basis of conservatively limiting assumptions. The amino acids thus obtained are not explainable as due to chemical or biological contamination; their source is accordingly inferred as lunar. Under the conditions of hydrolysis of lunar extracts, cyanide is found to be converted, almost exclusively to glycine, to an extent of 10^?4.  相似文献   

Suspended matter in surface waters of the eastern Gulf of Guinea     

Brian D. Bornhold  Jean R. Mascle  Kenichi Harada 《Marine Geology》1973,14(4):M21-M31

Suspended matter in the surface waters of the eastern Gulf of Guinea was studied in relation to the prevailing oceanic currents and the sediment composition and source. A confused current system arises from the confluence of the Guinea Current and the South Equatorial Current in this area. Sediment-laden water is transported to the south of Fernando Póo into the Gulf in a south-westerly direction. The southeasterly flowing Guinea Current along the western edge of the Niger delta and the enormous sediment loads of the distributaries in this area contribute to a major lobe of suspended matter off the southwestern nose of the delta. Sediment concentration is inversely related to salinity in the northeastern Gulf. Sediment is also swept northwestward from the continental shelf of Gabon and the Congo Republic into the Gulf. Diatoms are the most abundant constituents with lesser amounts of organic aggregates and two varieties of fecal pellets.  相似文献   

Effect of open gap in coastal forest on tsunami run-up—investigations by experiment and numerical simulation     

Nguyen Ba Thuy  Katsutoshi Tanimoto  Norio Tanaka  Kenji Harada  Kosuke Iimura 《Ocean Engineering》2009,36(15-16):1258-1269

The objective of this study is to investigate the effects of an open gap, such as a road, in a coastal forest on tsunami run-up. A numerical model based on two-dimensional nonlinear long-wave equations was developed to account for the effects of drag and turbulence induced shear forces due to the presence of vegetation. Experiments were conducted on a forest simulated with vertical cylinders by changing the gap width. The numerical model was validated in good agreement with the experimental results. The numerical model was then applied to a wide forest of Pandanus odoratissimus, a tree species that is a dominant coastal vegetation on a sand dune in South and Southeast Asia. The effect of vertical stand characteristics of P. odoratissimus with aerial roots was considered on the drag resistance. A straight open gap perpendicular to the shoreline was used to investigate the effect of gap width. As the gap width increases, the flow velocity at the end of the open gap first increases, reaches a maximum, and then decreases, while the run-up height increases monotonously. The maximum velocity in the present condition is 1.7 times the maximum velocity without a coastal forest. The effects of different gap arrangements in the forest on tsunami run-up were also investigated in this paper. The flow velocity at the end of an open gap can be reduced by a staggered arrangement.  相似文献   

The δ13C–δ18O variations in marble in the Hida Belt,Japan     

Hironobu Harada  Tatsuki Tsujimori  Keitaro Kunugiza  Katsuyuki Yamashita  Shogo Aoki  Kazumasa Aoki  Hideko Takayanagi  Yasufumi Iryu 《Island Arc》2021,30(1):e12389

Marble has a great potential to understand a history of various geological events occurring during tectonic processes. In order to decode metamorphic–metasomatic records on C–O isotope compositions of marble at mid-crustal conditions, we conducted a C–O–Sr isotope study on upper amphibolite-facies marbles and a carbonate–silicate rock from the Hida Belt, which was once a part of the crustal basement of the East Asian continental margin. Carbon and oxygen isotope analyses of calcite from marbles (Kamioka area) and a carbonate–silicate rock (Wadagawa area) show a large variation of δ¹³C [VPDB] and δ¹⁸O [VSMOW] values (from −4.4 to +4.2 ‰ and +1.6 to +20.8 ‰, respectively). The low δ¹³C values of calcites from the carbonate–silicate rock (from −4.4 to −2.9 ‰) can be explained by decarbonation (CO₂ releasing) reactions; carbon–oxygen isotope modeling suggests that a decrease of δ¹³C strongly depends on the amount of silicate reacting with carbonates. The occurrence of metamorphic clinopyroxene in marbles indicates that all samples have been affected by decarbonation reactions. All δ¹⁸O values of calcites are remarkably lower than the marine-carbonate values. The large δ¹⁸O variation can be explained by the isotope exchange via interactions between marble, external fluids, and/or silicates. Remarkably low δ¹⁸O values of marbles that are lower than mantle value (~+5 ‰) suggest the interaction with meteoric water at a later stage. Sr isotope ratios (⁸⁷Sr/⁸⁶Sr = 0.707255–0.708220) might be close to their protolith values. One zircon associated with wollastonite in a marble thin-section yields a U–Pb age of 222 ± 3 Ma, which represents the timing of the recrystallization of marble, triggered by H₂O-rich fluid infiltration at a relatively high-temperature condition. Our isotope study implies that the upper amphibolite-facies condition, like the Hida Belt, might be appropriate to cause decarbonation reactions which can modify original isotope compositions of marble if carbonates react with silicates.  相似文献