排序方式： 共有41条查询结果，搜索用时 78 毫秒
1.
Takushi Niki Miwa Shimizu Ayako Fujishiro Junji Kinoshita 《Journal of Oceanography》2007,63(5):873-877
During time-series observations in Sagami Bay, Japan, the concentration of dissolved dimethylsulfoniopropionate (DMSPd), a precursor of dimethylsulfide (DMS), was negatively correlated with salinity. In the laboratory, low-salinity shock reduced
DMS production rates of the natural bacterial community and induced rapid DMSP release from a dinophyte, Heterocapsa triquetra, suggesting that low-salinity shock reduced DMSPd consumption but enhanced DMSPd production, which agrees with the negative correlation between DMSPd and salinity observed in Sagami bay. In addition, low-salinity shock did not affect DMSP lyase activity of H. triquetra. Low-salinity shock would increase the contribution from algae in DMS production, leading to an increase in potential DMS
productivity in the environment. 相似文献
2.
Koji Kakinoki Shiro Imawaki Hiroshi Uchida Hirohiko Nakamura Kaoru Ichikawa Shin-Ichiro Umatani Ayako Nishina Hiroshi Ichikawa Mark Wimbush 《Journal of Oceanography》2008,64(3):373-384
Two inverted echo sounders were maintained on coastal and offshore sides of the Kuroshio south of Japan from October 1993
to July 2004. Applying the gravest empirical mode method, we obtained a time series of geostrophic transport. Estimated transports
generally agree well with geostrophic transports estimated from hydrography. Their agreement with the hydrographic transports
is better than that of transports estimated from satellite altimetry data. The geostrophic transport is expressed as the surface
transport per unit depth multiplied by the equivalent depth. The geostrophic transport varies mostly with the surface transport
and fractionally with the equivalent depth. Seasonal variation of the geostrophic transport has a minimum in March and a maximum
in September, with a range of about one fifth of the total transport. 相似文献
3.
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
4.
Abstract A recent K–Ar study elucidated that eruptive style in the eastern Izu peninsula changed from polygenetic to monogenetic volcano at 0.3–0.2 Ma. To narrow down the time of change, we determined 10 K–Ar ages on Togasayama Andesite of Amagi volcano, the youngest polygenetic volcano in the area, and Togasayama Monogenetic Volcano, one of the oldest monogenetic volcanoes in the area, which overlies a part of the Togasayama Andesite. Dating results showed that the Togasayama Andesite effused at least from 0.34 to 0.20 Ma, whereas the Togasayama Monogenetic Volcano erupted at 0.26–0.29 Ma, suggesting that the northern part of the Togasayama Andesite effused after the eruption of the Togasayama Monogenetic Volcano. Considering previous data, it is therefore inferred that change of eruptive style in the eastern Izu area occurred during the period 0.29–0.20 Ma, with considerable overlap of both polygenetic and monogenetic volcanism. 相似文献
5.
Hideo Shiogama Masahiro Watanabe Masakazu Yoshimori Tokuta Yokohata Tomoo Ogura James D. Annan Julia C. Hargreaves Manabu Abe Youichi Kamae Ryouta O’ishi Rei Nobui Seita Emori Toru Nozawa Ayako Abe-Ouchi Masahide Kimoto 《Climate Dynamics》2012,39(12):3041-3056
In this study, we constructed a perturbed physics ensemble (PPE) for the MIROC5 coupled atmosphere–ocean general circulation model (CGCM) to investigate the parametric uncertainty of climate sensitivity (CS). Previous studies of PPEs have mainly used the atmosphere-slab ocean models. A few PPE studies using a CGCM applied flux corrections, because perturbations in parameters can lead to large radiation imbalances at the top of the atmosphere and climate drifts. We developed a method to prevent climate drifts in PPE experiments using the MIROC5 CGCM without flux corrections. We simultaneously swept 10 parameters in atmosphere and surface schemes. The range of CS (estimated from our 35 ensemble members) was not wide (2.2–3.2?°C). The shortwave cloud feedback related to changes in middle-level cloud albedo dominated the variations in the total feedback. We found three performance metrics for the present climate simulations of middle-level cloud albedo, precipitation, and ENSO amplitude that systematically relate to the variations in shortwave cloud feedback in this PPE. 相似文献
6.
Masakazu Yoshimori Masahiro Watanabe Ayako Abe-Ouchi Hideo Shiogama Tomoo Ogura 《Climate Dynamics》2014,42(5-6):1613-1630
The finding that surface warming over the Arctic exceeds that over the rest of the world under global warming is a robust feature among general circulation models (GCMs). While various mechanisms have been proposed, quantifying their relative contributions is an important task in order to understand model behavior. Here we apply a recently proposed feedback analysis technique to an atmosphere–ocean GCM under two and four times CO2 concentrations which approximately lead to seasonally and annually sea ice-free climates. The contribution of feedbacks to Arctic temperature change is investigated. The surface warming in the Arctic is contributed by albedo, water vapour and large-scale condensation feedbacks and reduced by the evaporative cooling feedback. The surface warming contrast between the Arctic and the global averages (AA) is maintained by albedo and evaporative cooling feedbacks. The latter contributes to AA predominantly by cooling the low latitudes more than the Arctic. Latent heat transport into the Arctic increases and hence evaporative cooling plus large-scale condensation feedback contributes positively to AA. On the other hand, dry-static energy transport into the Arctic decreases and hence dynamical heating feedback contributes negatively to AA. An important contribution is thus made via changes in hydrological cycle and not via the ‘dry’ heat transport process. A larger response near the surface than aloft in the Arctic is maintained by the albedo, water vapour, and dynamical heating feedbacks, in which the albedo and water vapour feedbacks contribute through warming the surface more than aloft, and the dynamical heating feedback contributes by cooling aloft more than the surface. In our experiments, ocean and sea ice dynamics play a secondary role. It is shown that a different level of CO2 increase introduces a latitudinal and seasonal difference into the feedbacks. 相似文献
7.
In order to better estimate meso-scale variabilities in the energetic Kuroshio Extension (KE) region, simultaneous assimilation of drifter-derived velocity data, together with satellite and in situ hydrographic data, is attempted by using a high-resolution 4-dimensional variational data assimilation (4D-VAR) system. Our experimental results, both with and without assimilation of drifter data (Exp. Drf and Exp. Ref, respectively) for the period during Aug–Oct 2005, show that the reproduced fields in Exp. Drf better reflect the observed meso-scale features such as the KE meandering jet and associated eddies. The adjoint sensitivity analysis indicates that our 4D-VAR system has the ability to provide a more realistic timeseries of the meandering jet structures that play a key role in the intergyre exchange between the subtropical and subarctic gyres in the North Pacific. In addition, the observed information from the surface drifters works to improve the subsurface structure. These results illustrate the advantage of our 4D-VAR simultaneous assimilation with the addition of drifter-derived surface velocity information. 相似文献
8.
Ayako Fujii Sakae Toyoda Osamu Yoshida Shuichi Watanabe Ken’ichi Sasaki Naohiro Yoshida 《Journal of Oceanography》2013,69(2):147-157
N2O concentration and its isotopomer ratios were measured over a wide area from San Diego to Honolulu in the eastern subtropical North Pacific (ESNP). Waters in the study area had an N2O maximum (38.2–50.5 nmol kg?1) at 600–1000 m depth, which is similar to the profiles obtained previously in other areas in the North Pacific. We separated the seawater into five water masses (two for the surface layer, two for the middle layer, and one for the deep layer) and deduced N2O production–consumption mechanisms in each water body by use of N2O isotopomer ratios. The results showed that the mechanisms differ slightly among water masses. In the “coastal” surface layer, N2O is produced by nitrification (NH2OH oxidation). In the “open ocean” surface layer, it is produced mainly by nitrifier denitrification and to a lesser extent by nitrification under substrate-limited conditions. In both “upwelling” and “open ocean” middle layers it is produced mainly by denitrification and to a lesser extent by nitrifier denitrification. It is also partly reduced. In the deep layer, it is produced predominantly by denitrification with partial reduction. In this way, isotopomers aid elucidation of production–consumption mechanisms of N2O in the sea even though the mechanisms cannot always be ascertained. 相似文献
9.
Gravity and S-wave modelling across the Jan Mayen Ridge,North Atlantic; implications for crustal lithology 总被引：1，自引：0，他引：1
Rolf Mjelde Inger Eckhoff Ståle Solbakken Shuichi Kodaira Hideki Shimamura Karl Gunnarsson Ayako Nakanishi Hajime Shiobara 《Marine Geophysical Researches》2007,28(1):27-41
The horizontal components from fourteen Ocean Bottom Seismometers deployed along four profiles focused along the western margin
of the Jan Mayen microcontinent, North Atlantic, have been modelled with regard to S-waves, based on P-wave models obtained
earlier. The seismic models have furthermore been constrained by 2D gravity modelling. High V
p/V
s-ratios (2.3–7.9) within the Cenozoic sedimentary section are attributed to significant porosities, whereas V
p/V
s-ratios in the order of 1.9–2.2 for the Mesozoic and Paleozoic sedimentary rocks indicate shale-dominated lithology throughout
the area. The eastern side of the Jan Mayen Ridge is interpreted as a passive, volcanic margin, based on relatively high crustal
V
p/V
s-ratios (1.9), whereas lower V
p/V
s-ratios (1.75–1.8) suggest the presence of intermediate composition crust and non-volcanic margin on the western side of the
ridge. In the westernmost part of the Jan Mayen Basin, slightly increased upper mantle V
p/V
s-ratios may indicate some degree of serpentization of upper mantle peridotites. 相似文献
10.
Precise Positioning of Ocean Bottom Seismometer by Using Acoustic Transponder and CTD 总被引：1，自引：0，他引：1
Shiobara Hajime Nakanishi Ayako Shimamura Hideki Mjelde Rolf Kanazawa Toshihiko Berg Eivind W. 《Marine Geophysical Researches》1997,19(3):199-209
We have obtained precise estimates of the position of Ocean Bottom Seismometers (OBS) on the sea bottom. Such estimates are usually uncertain due to their free falling deployment. This uncertainty is small enough, or is correctable, with OBS spacing of more than 10 km usually employed in crustal studies. But, for example, if the spacing is only 200 m for OBS reflection studies, estimates of the position with an accuracy of the order of 10 m or more is required.The determination was carried out with the slant range data, ship position data and a 1D acoustic velocity structure calculated from Conductivity–Temperature–Depth (CTD) data, if they are available. The slant range data were obtained by an acoustic transponder system designed for the sinker releasing of the OBS or travel time data of direct water wave arrivals by airgun shooting. The ship position data was obtained by a single GPS or DGPS. The method of calculation was similar to those used for earthquake hypocenter determination.The results indicate that the accuracy of determined OBS positions is enough for present OBS experiments, which becomes order of 1 m by using the DGPS and of less than 10 m by using the single GPS, if we measure the distance from several positions at the sea surface by using a transponder system which is not designed for the precise ranging. The geometry of calling positions is most important to determine the OBS position, even if we use the data with larger error, such as the direct water wave arrival data. The 1D acoustic velocity structure should be required for the correct depth of the OBS. Although it is rare that we use a CTD, even an empirical velocity structure works well. 相似文献