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241.
Effect of iron enrichment on the dynamics of transparent exopolymer particles in the western subarctic Pacific 总被引:1,自引:0,他引:1
Neelam Ramaiah Shigenobu Takeda Ken Furuya Takeshi Yoshimura Jun Nishioka Tatsuo Aono Yukihiro Nojiri Keiri Imai Isao Kudo Hiroaki Saito Atsushi Tsuda 《Progress in Oceanography》2005,64(2-4):253
Dynamics of transparent exopolymer particles (TEP) was studied during the first in situ iron-enrichment experiment conducted in the western subarctic Pacific in July–August 2001, with the goal of evaluating the contribution of TEP to vertical flux as a result of increased primary production following iron enrichment in open ocean ecosystems. Subsequent to the enhancement of phytoplankton production, we observed increase in TEP concentration in the surface layer and sedimentation of organic matter beneath it. Vertical profiles of TEP, chlorophyll a (Chl a) and particulate organic carbon (POC) were obtained from six depths between 5 and 70 m, from a station each located inside and outside the enriched patch. TEP and total mass flux were estimated from the floating sediment traps deployed at 200 m depth. Chl a and TEP concentrations outside the patch varied from 0.2 to 1.9 μg L−1 and 40–60 μg XG equiv. L−1, respectively. Inside the patch, Chl a increased drastically from day 7 reaching the peak of 19.2 μg L−1 on day 13, which coincided with the TEP peak of 189 μg XG equiv. L−1. TEP flux in the sediment trap increased from 41 to 88 mg XG equiv. m−2 d−1, with 8–14% contribution of TEP to total mass flux. This forms the basic data set on ambient concentrations of TEP in the western subarctic Pacific, and evaluation of the effect of iron enrichment on TEP. 相似文献
242.
Takashi Midorikawa Sonoki Iwano Kazuhiro Saito Hiroyuki Takano Hitomi Kamiya Masao Ishii Hisayuki Y. Inoue 《Journal of Oceanography》2003,59(6):871-882
We observed the partial pressure of oceanic CO2, pCO2
sea, and related surface properties in the westernmost region of the subarctic North Pacific, seasonally from 1998 to 2001. The
pCO2
sea in the Oyashio region showed a large decrease from winter to spring. In winter, pCO2
sea was higher than 400 μatm in the Oyashio region and this region was a source of atmospheric CO2. In spring, pCO2
sea decreased to extremely low values, less than 200 μatm (minimum, 139 μatm in 2001), around the Oyashio region with low surface
salinity and this region turned out to be a strong sink. The spatial variations of pCO2
sea were especially large in spring in this region. The typical Oyashio water with minimal mixing with subtropical warm water
was extracted based on the criterion of potential alkalinity. The contribution of main oceanic processes to the changes in
pCO2
sea from winter to spring was estimated from the changes in the concentrations of dissolved inorganic carbon and nutrients, total
alkalinity, temperature and salinity observed in surface waters in respective years. These quantifications indicated that
photosynthesis made the largest contribution to the observed pCO2
sea decreases in all years and its magnitude was variable year by year. These year-to-year differences in spring biological contribution
could be linked to those in the development of the density stratification due to the decrease in surface salinity. Thus, the
changes in the surface physical structure could induce those in pCO2
sea in the Oyashio region in spring. Furthermore, it is suggested that the direction and magnitude of the air-sea CO2 flux during this season could be controlled significantly by the onset time of the spring bloom.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
243.
Hiroshi Murakami Kosei Sasaoka Kohtaro Hosoda Hajime Fukushima Mitsuhiro Toratani Robert Frouin B. Greg Mitchell Mati Kahru Pierre-Yves Deschamps Dennis Clark Stephanie Flora Motoaki Kishino Sei-Ichi Saitoh Ichio Asanuma Akihiko Tanaka Hiroaki Sasaki Katsumi Yokouchi Yoko Kiyomoto Hiroaki Saito Cécile Dupouy Absornsuda Siripong Satsuki Matsumura Joji Ishizaka 《Journal of Oceanography》2006,62(3):373-393
The Global Imager (GLI) aboard the Advanced Earth Observing Satellite-II (ADEOS-II) made global observations from 2 April
2003 to 24 October 2003. In cooperation with several institutes and scientists, we obtained quality controlled match-ups between
GLI products and in-situ data, 116 for chlorophyll-a concentration (CHLA), 249 for normalized water-leaving radiance (nLw) at 443 nm, and 201 for
aerosol optical thickness at 865 nm (Tau_865) and Angstrom exponent between 520 and 865 nm (Angstrom). We evaluated the GLI
ocean color products and investigated the causes of errors using the match-ups. The median absolute percentage differences
(MedPD) between GLI and in-situ data were 14.1–35.7% for nLws at 380–565 nm, 52.5–74.8% nLws at 625–680 nm, 47.6% for Tau_865, 46.2% for Angstrom, and 46.6%
for CHLA, values that are comparable to the ocean-color products of other sensors. We found that some errors in GLI products
are correlated with observational conditions; nLw values were underestimated when nLw at 680 nm was high, CHLA was underestimated
in absorptive aerosol conditions, and Tau_865 was overestimated in sunglint regions. The error correlations indicate that
we need to improve the retrievals of the optical properties of absorptive aerosols and seawater and sea surface reflection
for further applications, including coastal monitoring and the combined use of products from multiple sensors. 相似文献
244.
245.
Distribution of Trace Bioelements in the Subarctic North Pacific Ocean and the Bering Sea (the R/V Hakuho Maru Cruise KH-97-2) 总被引:2,自引:1,他引:2
Yukiyo Fujishima Kazumasa Ueda Masahiro Maruo Ehchiro Nakayama Chikako Tokutome Hiroshi Hasegawa Masakazu Matsui Yoshiki Sohrin 《Journal of Oceanography》2001,57(3):261-273
A column concentration-high resolution inductively coupled plasma mass spectrometry (ICP-MS) determination was applied to measure the total dissolved concentrations of Fe, Co, Ni, Cu and Zn in seawater collected from the subarctic North Pacific (~45°N) and the Bering Sea in July–September 1997. Total adsorbable Mn was determined on board by column electrolysis preconcentration and chemiluminescence detection. The vertical profiles for Fe, Ni and Zn were nutrient-like. The deep water concentration of Fe was ~0.5 nM in the northeast Pacific (18°-140°W) and increased to ~1 nM in the northwest Pacific (161°E) and ~2 nM in the Bering Sea (57°N, 180°E). The deep water concentrations for Ni and Zn in the Bering Sea were also 1.3–2 times higher than in the North Pacific. The profiles for Co and Cu were examined in the subarctic North Pacific, and results obtained were consistent with previous reports. There was a significant correlation between the concentrations of Co and Mn except for surface mixed layer. The profiles for total adsorbable Mn were similar to the reported profiles for total dissolvable Mn. The deep water concentration of Mn in the Bering Sea was also 4 times higher than in the North Pacific. Iron and zinc were depleted in surface water of the subarctic North Pacific. The relationship between these trace elements and nutrients suggests that these elements could be a limiting factor of phytoplankton productivity. In the Bering Sea, surface water contained ~0.3 nM of Fe. The Zn concentration, which was less than the detection limit in surface water, increased at shallower depths (~30 m) compared with the subarctic North Pacific. These results imply a higher flux of Fe and Zn to surface water in the Bering Sea. This in turn may cause the ecosystem in the Bering Sea characterized by a dominance of diatoms and high regenerated production. 相似文献
246.
We have detected a new interstellar molecule, H2CN (methylene amidogen), in the cold, dark molecular cloud TMC-l. The column density of H2CN is estimated to be approximately 1.5 x 10(11) cm-2 by assuming an excitation temperature of 5 K. This column density corresponds to a fractional abundance relative to H2 of approximately 1.5 x 10(-11). This value is more than three orders of magnitude less than the abundance of the related molecule HCN in TMC-1. We also report a tentative detection of H2CN in Sgr B2(N). The formation mechanism of H2CN is discussed. Our detection of the H2CN molecule may suggest the existence of a new series of carbon-chain molecules, CH2CnN (n = 0, 1, 2,...). 相似文献
247.
Hybridization of a Shallow 'I-type' Granitoid Pluton and its Host Migmatite by Magma-Chamber Wall Collapse: the Tokuwa Pluton, Central Japan 总被引:1,自引:0,他引:1
The Miocene Tokuwa pluton of I-type granitoidaffinity was emplaced discordantly into a Cretaceous to Paleogeneaccretionary complex and induced a contact aureole in whichvarious thermally metamorphosed rocks were developed, includinghornfels, metatexite, diatexite and cordierite-bearing tonalite(Crd-tonalite) of S-type granite affinity. Thethermally metamorphosed rocks show low-pressure reaction texturesculminating in partial melting. Peak PT conditions of3 kbar at 780°C are estimated on the basis of the TWQ thermobarometerfor the garnet-bearing rocks. The rocks in the contact aureoleexhibit a gradual transition from hornfels, through metatexiteand diatexite to Crd-tonalite. The Sr-isotopic composition atthe time of Tokuwa pluton emplacement at 12 Ma decreases systematicallyfrom metatexite (0·71000·7112) throughdiatexite (0·70780·7094) to Crd-tonalite(0·70670·7068); this trend is interpretedin terms of mixing between the Tokuwa magma and the aureolemigmatites. The field relationships, geochemical data, and isotopicdata collectively suggest that the emplacement of the Tokuwapluton triggered partial melting of the surrounding metasedimentaryrocks. Subsequent hybridization of the Tokuwa magma with themetatexite in variable proportions produced the Crd-tonaliteand diatexite. The hybridization was caused by invasion of theTokuwa magma into the migmatite zone, accompanied by gravitationalcollapse of the previously crystallized wall of the magma chamber.The data presented demonstrate that even a relatively low-temperature,shallow, I-type granitoid pluton can induce contactanatexis and hybrid S-type granitoid formationat the intrusive contact. KEY WORDS: contact metamorphism; hybridization; magmahost-rock interaction; migmatite; S-type granitoid 相似文献
248.
Yusuke Miyajima Ayaka Saito Hiroyuki Kagi Tatsunori Yokoyama Yoshio Takahashi Takafumi Hirata 《Geostandards and Geoanalytical Research》2021,45(1):189-205
Uncertainty for elemental and isotopic measurements in calcite by LA‐ICP‐MS is largely controlled by the homogeneity of the reference materials (RMs) used for calibration and validation. In order to produce calcite RMs with homogeneous elemental and isotopic compositions, we incorporated elements including U, Pb and rare earth elements into calcite through heat‐ and pressure‐induced crystallisation from amorphous calcium carbonate that was precipitated from element‐doped reagent solution. X‐ray absorption spectra showed that U was present as U(VI) in the synthesised calcite, probably with a different local structure from that of aqueous uranyl ions. The uptake rate of U by our calcite was higher in comparison with synthetic calcite of previous studies. Variations of element mass fractions in the calcite were better than 12% 2RSD, mostly within 7%. The 207Pb/206Pb ratio in the calcite showed < 1% variations, while the 238U/206Pb ratio showed 3–24% variations depending on element mass fractions. Using the synthetic calcite as primary RMs, we could date a natural calcite RM, WC‐1, with analytical uncertainty as low as < 3%. The method presented can be useful to produce calcite with controlled and homogeneous element mass fractions and is a promising alternative to natural calcite RMs for U‐Pb geochronology. 相似文献
249.
Wood Nathan Jones Jeanne M. Yamazaki Yoshiki Cheung Kwok-Fai Brown Jacinta Jones Jamie L. Abdollahian Nina 《Natural Hazards》2019,95(3):505-528
Natural Hazards - Population vulnerability from tsunamis is a function of the number and location of individuals in hazard zones and their ability to reach safety before wave arrival. Previous... 相似文献
250.
The variogram method for a fractal model of a rock joint surface 总被引:1,自引:0,他引:1
The variogram method can be used to make a fractal model of a rock joint surface. However, it has been found that the range of lag satisfying the power law is very small, that is, less than about 10% of the profile length. The cause of this has been investigated mathematically. The main cause of this problem is due to the fact that the profile length is assumed infinite for the theory, but it is finite for the actual calculation. This discrepancy between the actual calculation and the theory yields a significant error and causes the problem when the lag is large. To confirm the validity of this conclusion, it has been demonstrated that the range of lag satisfying the power law increases with an increase in the profile length by applying the variogram method to profiles cut from a long profile. In addition, the range of lag was investigated mathematically and it has been clarified that the range of lag increases with an increase in the fractal dimension. These results suggest that the profile length, the sampling interval and the removal of the linear trend are items to which we must pay attention when we use the variogram method. 相似文献