Modeling of spring bloom in the western subarctic Pacific (off Japan) with observed vertical density structure   总被引：1，自引：0，他引：1  

A. Yoshimori  J. Ishizaka  T. Kono  H. Kasai  H. Saito  M. J. Kishi  S. Taguchi 《Journal of Oceanography》1995,51(4):471-488

Effects of vertical stability on spring blooms of phytoplankton were investigated for the western subarctic Pacific ocean using a one-dimensional (depth) ecosystem model. In the model, vertical stability was expressed by diffusion constants calculated from observed density distribution. Dynamics of phytoplankton in blooms was calculated by the model using the vertical diffusion. Then, the calculated results were compared with the Coastal Zone Color Scanner (CZCS) data. The comparison shows that the shallow surface mixed layer causes early start days of spring blooms at inshore (northern) stations. In addition, spring blooms continue long at inshore (northern) stations since a water column has weak stability. This is because weak stability of a water column causes large nutrient supply from a deep layer and large diffusive transport of phytoplankton biomass from the subsurface maximum.  相似文献   

On sedimentation of phosphorus in specified area outside of the Changjiang Estuary     

Zhou Huaiyang  Pan Jianming  Chen Jianfang  Wang Huaizhao  Y. Saito  Y. Kanai 《海洋学报(英文版)》2001,20(1):85-93

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Control of incised-valley fill stacking patterns by accelerated and decelerated sea-level rise: the Changjiang example during the last deglaciation     

K. Hori  Y. Saito  Q. Zhao  P. Wang 《Geo-Marine Letters》2002,22(3):127-132

The evolution of paleo-Changjiang incised-valley fills in relation to step-like, postglacial sea-level rises is presented, based on sedimentary facies analyses and ¹⁴C age dating on three sediment cores. Timing of rapid transgressions deduced from the succession of incised-valley fills correlate well with Barbados's very rapid, sea-level rise periods. By contrast, estuarine deposits aggraded actively, and the coastline did not retreat markedly during the Younger Dryas (YD) cooling event when the rising rate decelerated considerably relative to stages before and after the YD.  相似文献   

Nutrient and Plankton Dynamics in the NE and NW Gyres of the Subarctic Pacific Ocean     

Paul J. Harrison  Frank A. Whitney  Atsushi Tsuda  Hiroaki Saito  Kazuaki Tadokoro 《Journal of Oceanography》2004,60(1):93-117

The western subarctic gyre (WSG) and the eastern Alaska Grye (AG) on each side of the subarctic North Pacific, have many similarities. In both gyres, macronutrients are generally high and chl is low, and hence both gyres are High Nitrate, Low Chlorophyll (HNLC) regions. Despite the general similarities between these two gyres, there are many important differences. The time series station established at Stn KNOT on the southwest edge of the WSG and two in situ mesoscale iron enrichment experiments at each of the gyres has provided more information on iron concentrations, the dual role of iron and silicate limitation and seasonal cycles in the gyres. There is more seasonality in many parameters at Stn KNOT than at Stn P. There is an increase in Chl and primary productivity at Stn KNOT in May followed by increased iron limitation in summer. Low DIC:NO₃ ratios and high Si:NO₃ ratios in the WSG, indicate lower calcification and higher diatom production than at Stn P. The sources of iron for these areas are still not clear, but horizontal transport of iron rich coastal water and vertical transport could be important sources at certain times of the year in addition to dust input. Satellite images show that chl-rich coastal waters occasionally extend to the vicinity of Stn KNOT and therefore Stn KNOT may not always represent conditions in the main part of the WSG. This review focuses mainly on a comparison of Stn KNOT and Stn P, two time series stations on the edge of two very large gyres. At present, we have a limited understanding of the temporal and spatial variability within each of these large gyres. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The earth's palaeomagnetosphere as the third type of planetary magnetosphere     

Takao Saito  Tohru Sakurai  Kiyohumi Yumoto 《Planetary and Space Science》1978,26(5):413-422

From the viewpoint of dynamical topology, planetary magnetospheres are classified into three: Types 1, 2 and 3. When the rotation vector and dipole moment of a planet and the velocity vector of the solar wind are denoted as Ω, M, and V, respectively, the planetary magnetosphere with Ω∥M⊥V is called Type 1. The magnetospheres of the present Earth, Jupiter, and Uranus at its equinoctial points belong to this type. The magnetosphere with Ω∥M∥V is called Type 2, which includes the Uranian magnetosphere at its solstitial points. The magnetosphere with Ω⊥M and Ω⊥V is called Type 3. The Earth's palaeomagnetosphere is considered to have experienced Type 3 during excursions and transition stages of palaeomagnetic polarity reversals. In the Type 3 magnetosphere, drastic diurnal variations are expected in configurations of the dayside cusps, tail axis, neutral sheet, polar caps, and so on. A possible relation between the Type 3 palaeomagnetosphere and palaeoclimate of the Earth during polarity reversals and geomagnetic excursions is suggested. It is also suggested that the heliomagnetosphere during polarity reversals of the general field of the Sun exhibits a drastic configuration change similar to the Type 3 palaeomagnetosphere of the Earth. A relation between the perpendicular condition Ω⊥M and magnetic variable stars and pulsars is briefly discussed.  相似文献   

Measurement of the drift of auroral radar echoes with the radar auroragraph     

R.S. Unwin  T. Saito  K. Yumoto 《Planetary and Space Science》1978,26(6):519-524

The auroragraph is a device for the analysis of any movements of patterns on movie films. Its application to the PPI record from an auroral radar is described, and examples from Syowa Station, Antarctica are given. The radar auroragraph has advantages over other more conventional methods of deriving the speed and direction of movement of auroral radar echoes in space.  相似文献   

MIS11–19 pollen stratigraphy from the 250-m Choshi core, northeast Boso Peninsula, central Japan: Implications for the early/mid-Brunhes (400–780 ka) climate signals     

Masaaki  Okuda  Hiroomi  Nakazato  Norio  Miyoshi  Takeshi  Nakagawa  Hiroko  Okazaki  Saneatsu  Saito  Asahiko  Taira 《Island Arc》2006,15(3):338-354

Abstract   The 250-m Choshi core (CHOSHI-1), drilled from hemipelagic muds of the Inubo Group, has been physically, geochemically and tephrochronologically analyzed back to 1 Ma. We provide pollen results for the 19–169 m section of the core (400–780 ka) bracketed by the marker tephra Ty1 (equivalent to J4) and the Brunhes–Matuyama paleomagnetic boundary. The results show good agreement with the corresponding oxygen isotope (δ¹⁸O) profile, with high δ¹⁸O intervals dominated by boreal conifers Picea , Abies , Pinus (subgen. Haploxylon ) and Tsuga ( diversifolia ), whereas low δ¹⁸O intervals are dominated by temperate conifers Cryptomeria , Taxaceae-Cephalotaxaceae-Cupressaceae and Sciadopitys . In order to confirm pollen-climate relations for the relevant taxa, a modern surface pollen dataset for the Japanese archipelago was consulted. In this analysis, the ratios of Cryptomeria / Picea and temperate/boreal conifers serve as proxies for the 100-kyr glacial/interglacial cycle during the Middle Pleistocene. Distinct signals for marine isotope stages (MIS) 11, 12, 13–15, 16, 17 and 18–19 are recognized in accordance with the tephrochronology and δ¹⁸O of the same core. Application of the criteria to an independent pollen record from Lake Biwa provides an integrated pollen stratigraphy for mid-latitude Japan during the past 800 ky. Some degree of uncertainty remains in the chronology of the MIS13–15 interval, relating to the uncertainty in the eruption age of widespread tephra Ks11.  相似文献   

Sequence-stratigraphic signatures of hemipelagic siltstones in deep-water successions: the Lower Pleistocene Kiwada and Otadai Formations, Boso Peninsula, Japan     

Sotaro Takano  Makoto Ito  Takanori Nakano  Keiji Horikawa  Yuzuru Nakamura  Takahiro Saito 《Sedimentary Geology》2004,170(3-4):189-206

Sequence-stratigraphic signatures of hemipelagic siltstones were investigated using profiles of the magnetic susceptibility and selected chemical composition of the Early Pleistocene deep-water successions of the Kiwada and Otadai Formations on the Boso Peninsula, Japan. In the context of an independently developed sequence-stratigraphic framework for the submarine-fan deposits of the Otadai Formation, the magnetic susceptibility and chemical composition, such as the concentrations of TiO₂, MgO and Fe₂O₃, show that the lowstand systems tract deposits have higher values of these parameters than the transgressive and highstand systems tract deposits. In contrast, the CaO contents have inverse relationships with the magnetic susceptibility and are higher in the transgressive and highstand systems tract deposits. The positions of sequence boundaries largely coincide with the horizons from which the magnetic susceptibility and the contents of mafic component increase abruptly. The sequence-stratigraphic variations in the magnetic susceptibility and chemical composition of the submarine-fan hemipelagic siltstones are due to increases in the input of fine-grained, terrigenous clastic sediments from midwater flow suspension, in addition to the direct fluvial supply of relatively unmodified terrigenous clastic sediments during relative sea-level lowstands, although grain size of hemipelagic siltstones does not exhibit any distinct variation through depositional sequences. The Kiwada Formation is characterized by siltstone-dominated basin-plain deposits and its sequence-stratigraphic classification has been difficult when using just lithofacies features. Nevertheless, the profiles of the magnetic susceptibility and chemical composition of the basin-plain deposits are similar to those of the submarine-fan deposits with duration largely equivalent to the 41,000-years obliquity cycle of the Early Pleistocene oxygen isotope sea-level index. This finding indicates that the profiles of the magnetic susceptibility and chemical composition of hemipelagic siltstones reflect sequence-stratigraphic variation in the input of fine-grained terrigenous clastic sediments to the deep-water environments and are crucial for the recognition of cryptic sequence boundaries in hemipelagic successions.  相似文献   

Physicochemical, mineralogical, and geochemical characteristics of lacustrine sediments of the Konya Basin, Turkey, and their significance in relation to climatic change     

K. Inoue  M. Saito  T. Naruse 《Geomorphology》1998,23(2-4)

Physicochemical, mineralogical, and geochemical characteristics of 279 highly calcareous lacustrine sediment samples obtained from a 30 m drilling core in the western part of the Great Konya Basin, Turkey were studied. The sediments have a predominance of silt and clay fractions with a median diameter of 3–5 μm. Vertical changes of the amounts of water soluble components, gypsum, carbonates, and non-salt minerals such as quartz, feldspars, and layer silicates in the sediments suggest that there were climatic changes in the Konya Basin. The dominant clay mineral is smectite followed by kaolinite, illite, and palygorskite. The oxygen isotopic (δ¹⁸O) ratios of six quartz samples from the Konya sediments, a terra rossa soil beside Lake Bey ehir gölü and paleosols at the foot of Mt. Erciyes Da ranged from +18.1 to +20.6‰. The dominant clay minerals and δ¹⁸O ratios suggest that part of quartz and coexisting layer silicates is of long-range transported and/or local aeolian dust origin from arid and semi-arid regions such as North Africa, Israel, and the surroundings. The relatively high deposition rate might be due to aeolian dust input and/or the sediment input introduced by the rivers such as the Çar amba river from the Toros (Taurus) mountains. The vertical distributions of electro-conductivity, amounts of water soluble and non-salt components, and the gypsum content of the sediments suggest that gypsum-rich layers were formed under shallow, saline waters, possibly associated with warm to hot and dry environments such as the Last Interglacial epoch and the Early Holocene. The sediments characterized by relatively high amounts of non-salt sediments, in which gypsum did not accumulate, could be deeper water phases formed under the cold and/or wet environments such as the Glacial epochs.  相似文献   

Preface     

Nobuaki Niitsuma  Roland von Huene  Isao Motoyama  Saneatsu Saito  Kiyoshi Suyehiro  I. Selwyn Sacks 《Island Arc》2004,13(1):178-179

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