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111.
Masao Nakada 《Geophysical Journal International》1999,137(3):663-674
The response of a viscoelastic Earth to the melting of the Late Pleistocene ice sheets has been the subject of a number of investigations employing PREM. In PREM, a non-adiabatic density gradient (NADG) exists in the upper mantle, and to understand the implications of this model it is thus important to examine the effects of this NADG on the Earth's response to surface loads. This paper is based on the assumption that the contribution to the depth dependence of the density that is not due to self-compression is due to compositional change. This contribution is referred to as 'non-adiabatic'. We evaluate the effects of a non-adiabatic density jump (NADJ) for the 670 km discontinuity and the NADG in the upper mantle by adopting a compressible earth model with both a compositional density gradient and a density jump. Numerical calculations based on these models indicate that the magnitude of the Earth's response associated with the NADG is much smaller than that associated with the NADJ at 670 km depth. It is also confirmed that the higher modes associated with the NADJ and the NADG are much more sensitive to the existence of an elastic lithosphere than the fundamental modes associated with the density jumps at the surface and core–mantle boundary. 相似文献
112.
Futoki Sakaida Masao Moriyama Hiroshi Murakami Hiromi Oaku Yasushi Mitomi Akira Mukaida Hiroshi Kawamura 《Journal of Oceanography》1998,54(5):437-442
The Ocean Color and Temperature Scanner (OCTS) aboard the Advanced Earth Observing Satellite (ADEOS) can observe ocean color
and sea surface temperature (SST) simultaneously. This paper explains the algorithm for the OCTS SST product in the NASDA
OCTS mission. In the development of the latest, third version (V3) algorithm, the OCTS match-up dataset plays an important
role, especially when the coefficients required in the MCSST equation are derived and the equation form is adjusted. As a
result of the validation using the OCTS match-up dataset, the algorithm has improved the root mean square (rms) error of the
OCTS SST up to 0.698°C although some problems remain in the match-up dataset used in the present study. 相似文献
113.
Arne Krtzinger Ludger Mintrop Douglas W. R. Wallace Kenneth M. Johnson Craig Neill Bronte Tilbrook Philip Towler Hisayuki Y. Inoue Masao Ishii Gary Shaffer Rodrigo F. Torres Saavedra Eiji Ohtaki Eiji Yamashita Alain Poisson Christian Brunet Bernard Schauer Catherine Goyet Greg Eischeid 《Marine Chemistry》2000,72(2-4)
The ‘International Intercomparison Exercise of fCO2 Systems’ was carried out in 1996 during the R/V Meteor Cruise 36/1 from Bermuda/UK to Gran Canaria/Spain. Nine groups from six countries (Australia, Denmark, France, Germany, Japan, USA) participated in this exercise, bringing together 15 participants with seven underway fugacity of carbon dioxide (fCO2) systems, one discrete fCO2 system, and two underway pH systems, as well as systems for discrete measurement of total alkalinity and total dissolved inorganic carbon. Here, we compare surface seawater fCO2 measured synchronously by all participating instruments. A common infrastructure (seawater and calibration gas supply), different quality checks (performance of calibration procedures for CO2, temperature measurements) and a common procedure for calculation of final fCO2 were provided to reduce the largest possible amount of controllable sources of error. The results show that under such conditions underway measurements of the fCO2 in surface seawater and overlying air can be made to a high degree of agreement (±1 μatm) with a variety of possible equilibrator and system designs. Also, discrete fCO2 measurements can be made in good agreement (±3 μatm) with underway fCO2 data sets. However, even well-designed systems, which are operated without any obvious sign of malfunction, can show significant differences of the order of 10 μatm. Based on our results, no “best choice” for the type of the equilibrator nor specifics on its dimensions and flow rates of seawater and air can be made in regard to the achievable accuracy of the fCO2 system. Measurements of equilibrator temperature do not seem to be made with the required accuracy resulting in significant errors in fCO2 results. Calculation of fCO2 from high-quality total dissolved inorganic carbon (CT) and total alkalinity (AT) measurements does not yield results comparable in accuracy and precision to fCO2 measurements. 相似文献
114.
High organic carbon deposition in the northern margin of the Aleutian Basin (Bering Sea) before the last deglaciation 总被引:1,自引:0,他引:1
High-resolution geochemical, isotope and elemental data from core PC23A in the northern margin of the Aleutian Basin (Bering Sea) were used to reconstruct distinct paleoceanographic features of the last deglaciation (pre-Boreal[PB], Bølling-Allerød[BA], Younger Dryas[YD]). The PB and BA intervals are characterized by increased siliceous (diatom) and calcareous (coccolithophores and foraminifers) productivity represented by high biogenic opal and CaCO3 contents, respectively. The enhanced productivity can plausibly be attributed to an elevated sea-surface nutrient supply from increased melt-water input and enhanced Alaskan Stream injection under warm, restricted sea-ice conditions. High Corg/N ratios and low δ13C values of sediment organic matter during the PB and BA intervals reflect the contribution of terrestrial organic matters. The PB and BA intervals were also identified by laminated sediment layers of core PC23A, characterized by high Mo/Al and Cd/Al ratios, indicating that the bottom water condition remained anoxic. High δ15N values during the same period were attributed mainly to the increased nutrient utilization and subsequent denitrification of seawater nitrate. Part of high δ15N values may also be due to incorporation of inorganic nitrogen in the clay minerals. It is worthy of note that high total organic carbon (TOC) deposition occurred approximately 3,000 years before onset of the last deglaciation. Simultaneous high Corg/N ratios and low δ13C values clearly suggest that the high TOC content should be related to terrestrial organic carbon input. Low δ15N values during the high TOC interval also confirm the contribution of terrigenous organic matter. Although abundant calcareous phytoplankton production under cold, nutrient-poor conditions represented by Baex data was reported for high TOC deposition preceding the last deglaciation in an earlier study of the Okhotsk Sea, the main reason for the enhanced TOC deposition in the Bering Sea is an increased terrigenous input from the submerged continental shelves (Beringia) with a sea-level rise; this is further supported by Al enrichment of bulk sediments during the high TOC deposition. 相似文献
115.
Stable Carbon and Nitrogen Isotopic Characterization of Organic Matter in a Mangrove Ecosystem on the Southwestern Coast of Thailand 总被引:1,自引:0,他引:1
Organic matter in a tropical mangrove ecosystem was characterized by stable carbon and nitrogen isotopic analyze, conducted
on various organic samples, including land and mangrove plants, soils, particulate organic matter (POM), and sea and river
sediments along the southwestern coast of Thailand. The δ13C values of land plants and POM in river water can be explained in terms of a greater influence of C3 plants than C4 plants in this area. The POM and sediments from the Trang River and Ko Talibong area showed systematically higher δ15N values than those from Ko Muk and other coastal areas. Organic matter in the Trang River might be influenced by nitrogen
released from agricultural or human waste, which could affect the isotopic composition of POM and sediments in the Trang River
estuary and along the coast near the river mouth. We used a stochastic method to estimate the contributions of four organic
end-members, identifiable by their δ13C and δ15N values. The results implied that seagrasses were a major source of sedimentary organic matter, contributing 42 ± 5% in the
Ko Muk area and 36 ± 5% in the Ko Talibong area. The contribution of coastal POM to sediments was estimated to be only 13%
in Ko Muk and 19% in Ko Talibong. Mangrove plants contributed approximately 23% in both areas. It was concluded that seagrasses
are an important source of sedimentary organic matter in this coastal region of southwestern Thailand.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
116.
Low cyclic fatigue and hysteretic behavior of U‐shaped steel dampers for seismically isolated buildings under dynamic cyclic loadings
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Yu Jiao Shoichi Kishiki Satoshi Yamada Diana Ene Yoshinao Konishi Yuuma Hoashi Masao Terashima 《地震工程与结构动力学》2015,44(10):1523-1538
Energy dissipation devices are necessary for base‐isolated buildings to control the deformation in the isolation system and to dissipate the earthquake‐induced energy. U‐shaped steel dampers (also known as U‐dampers) dissipate energy through plastic deformation of specially designed U‐shaped steel elements. This type of device can be installed at several locations in the isolation system. U‐dampers have been widely used in Japan for different types of isolated structures, such as hospitals, plants and residential buildings, since the 1995 Kobe Earthquake. Previous research has used static tests to estimate the performance of U‐dampers. However, the ultimate plastic deformation capacities and hysteretic behaviors of full‐scale U‐dampers under dynamic excitations still remain unclear. In addition, it is unclear whether the initial temperature has an effect on the hysteretic behavior and plastic deformation capacity of U‐dampers. In this paper, two series of dynamic loading tests of U‐dampers were conducted to evaluate the issues described earlier. The major findings of the study are (i) the loading speed has little effect on the plastic deformation capacity of U‐dampers; (ii) method to evaluate the ultimate plastic deformation capacities of U‐shaped steel dampers of different sizes is established using a Manson–Coffin relation‐based equation that is based on the peak‐to‐peak horizontal shear angle γt, which is defined as the lateral deformation amplitude (peak‐to‐peak amplitude) divided by the height of the dampers; (iii) the loading rate and the initial temperature have a minimal effect on the hysteretic behavior of the U‐dampers; and (iv) a bilinear model is proposed to simulate the force‐deformation relationships of the U‐dampers. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
117.
Eitarou Oka Masao Ishii Toshiya Nakano Toshio Suga Shinya Kouketsu Masatoshi Miyamoto Hideyuki Nakano Bo Qiu Shusaku Sugimoto Yusuke Takatani 《Journal of Oceanography》2018,74(2):115-145
The 137°E repeat hydrographic section of the Japan Meteorological Agency across the western North Pacific was initiated in 1967 as part of the Cooperative Study of the Kuroshio and Adjacent Regions and has been continued biannually in winter and summer. The publicly available data from the section have been widely used to reveal seasonal to decadal variations and long-term changes of currents and water masses, biogeochemical and biological properties, and marine pollutants in relation to climate variability such as the El Niño-Southern Oscillation and the Pacific Decadal Oscillation. In commemoration of the 50th anniversary in 2016, this review summarizes the history and scientific achievements of the 137°E section during 1967–2016. Through the publication of more than 100 papers over this 50-year span, with the frequency and significance of the publication increasing in time, the 137°E section has demonstrated its importance for future investigations of physical–biogeochemical–biological interactions on various spatiotemporal scales, and thereby its utility in enhancing process understanding to aid projections of the impact of future climate change on ocean resources and ecosystems over the twenty-first century. 相似文献
118.
Daisuke Nagaoka Masahito Shigemitsu Masao Minagawa Shinichiro Noriki 《Journal of Oceanography》2010,66(1):117-132
We have investigated Pb concentrations and isotopic compositions in settling particles collected by sediment traps experiments
over a period of two years, from May 2005 to April 2007, at two depths, 770 and 5100 m, at station KNOT in the Northwestern
Pacific Ocean (44°N, 155°E). To the identify provenances of Pb, the samples were separated into two fractions by chemical
leaching techniques, with the leachate expected to contain Pb of anthropogenic origin. Isotopic compositions of Pb and concentrations
of Pb, Sc, Mn, La, Yb, and Th were measured by quadrupole ICP-MS. The isotope ratios of leachable Pb in settling particles
were 207Pb/206Pb = 0.860 ± 0.001; 208Pb/206Pb = 2.116 ± 0.002 (mean ± 95% confidence intervals), which are similar to those of aerosols in China that are greatly affected
by pollution from coal combustion. We estimated the mean contribution from anthropogenic Pb sources to the Pb in settling
particles, using the conventional binary (anthropogenic and natural Pb) mixing equation for Pb isotopes, as 90% in the upper
trap and 78% in the lower trap. Furthermore, we found a significant negative correlation between the isotope ratios of Pb
and concentrations of leachable Mn, normalized to those of leachable Pb, suggesting that manganese oxides play an important
role in transporting Pb from the upper layers of the ocean to the deeper layers. Our results support the speculation published
in a previous study that Pb might be scavenged by Mn oxides in the Northwestern Pacific Ocean. 相似文献
119.
Daiki Nomura Toru Takatsuka Masao Ishikawa Toshiyuki Kawamura Kunio Shirasawa Hisayuki Yoshikawa-Inoue 《Estuarine, Coastal and Shelf Science》2009
Physico-chemical properties in the brine and under-ice water were measured in Saroma-ko Lagoon on the northeastern coast of Hokkaido, Japan, which is connected to the Sea of Okhotsk, during the period from mid-February through mid-March 2006. The brine within brine channels of the sea ice was collected with a new sampling method examined in this study. Salinity, dissolved inorganic carbon (DIC), total alkalinity (TA), dissolved oxygen (DO), nutrients and oxygen isotopic ratio (δ18O) contained in the brine within brine channels of the sea ice and in the under-ice water varied largely in both time and space during the ice melt period, when discharge from Saromabetsu River located on the southeast of the lagoon increased markedly due to the onset of snow melting. The under-ice plume expands as far as 4.5 km from the river mouth at mid-March 2006, transporting chemical components supplied from the river into the lagoon. The under-ice river water was likely transported into the sea ice through well-developed brine channels in the sea ice due to upward flushing of water through brine channels occurred by loading of snowfalls deposited over the sea ice. These results suggest that the river water plume plays an important role in supplying chemical components into the sea ice, which may be a key process influencing the biogeochemical cycle in the seasonally ice-covered Saroma-ko Lagoon. 相似文献
120.