Millennial-scale vegetation changes during the last 40,000 yr based on a pollen record from Lake Biwa, Japan

A high-resolution pollen record covering the last 40,000 yr (BIW95-4) from Lake Biwa, western Japan, shows regional vegetation responses to millennial-scale climate changes. From 40 to 30 ka, Cryptomeria japonica was dominant around the lake among pinaceous conifers and deciduous broad-leaved trees. During this period, fluctuations of C.japonica are correlated with Dansgaard-Oeschger (D-O) cycles recognized from the anhysteretic remanent magnetization (ARM) record. Increases in the abundance of this taxon may have been caused by wetter summer conditions influenced by the East Asian monsoon or increased snowfall on the Sea of Japan side of the Japanese archipelago. Between 29 and 14 ka, pinaceous conifer forests mainly composed of Pinus subgenus Haploxylon, Tsuga, and Picea trees developed. At approximately 23 ka, Picea trees increased in abundance as ARM values decreased. This expansion of Picea trees has been correlated with Heinrich event (HE) 2 in the North Atlantic. At about 14 ka, the distribution of broad-leaved forest (mainly composed of deciduous oaks) began to expand after D-O 1. Evidence of significant vegetation change related to the abrupt Younger Dryas cooling event has not been found.     

Combining microsimulation and spatial interaction models for retail location analysis

Although the disaggregation of consumers is crucial in understanding the fragmented markets that are dominant in many developed countries, it is not always straightforward to carry out such disaggregation within conventional retail modelling frameworks due to the limitations of data. In particular, consumer grouping based on sampled data is not assured to link with the other statistics that are vital in estimating sampling biases and missing variables in the sampling survey. To overcome this difficulty, we propose a useful combination of spatial interaction modelling and microsimulation approaches for the reliable estimation of retail interactions based on a sample survey of consumer behaviour being linked with other areal statistics. We demonstrate this approach by building an operational retail interaction model to estimate expenditure flows from households to retail stores in a local city in Japan, Kusatsu City.      

Effects of large-scale wind on the Kuroshio path south of Japan in a 60-year historical OGCM simulation

The effects of large-scale wind forcing on the bimodality of the Kuroshio path south of Japan, the large meander (LM) and non-large meander (NLM), were studied by using a historical simulation (1948–2007) with a high-resolution Ocean general circulation models (OGCM). The Kuroshio in this simulation spent much time in the NLM state, and reproduced several aspects of its long-term path variability for the first time in historical OGCM simulation, presumably because the eddy kinetic energy was kept at a moderate level. By using the simulated fields, the relationships between wind forcing (or Kuroshio transport) and path variation proposed by past studies were tested, and specific roles of eddies in those variations were investigated. The long-term variation of the simulated net Kuroshio transport south of Japan was largely explained by the linear baroclinic Rossby wave adjustment to wind forcing. In the simulated LM events, a triggering meander originated from the interaction of a wind-induced positive sea surface height (SSH) anomaly with the upstream Kuroshio and was enlarged by cyclonic eddies from the recirculation gyre. The cyclonic eddy of the trigger meander was followed by a sizable anticyclonic eddy on the upstream side. Subsequently, a weak (strong) Kuroshio favored the LM (NLM). The LM tended to be maintained when the Kuroshio transport off southern Japan was small, and increasing Kuroshio transport promoted decay of an existing LM. The supply of disturbances from upstream, which is related to the wind-induced SSH variability at low latitudes, contributed to the maintenance of an existing LM.     

A model of solar flares triggered by interactions between force-free current loops and plasmoids

We present a model of solar flares triggered by collisions between current loops and plasmoids. We investigate a collision process between a force-free current loop and a plasmoid, by using 3-D resistive MHD code. It is shown that a current system can be induced in the front of a plasmoid, when it approaches a force-free current loop. This secondary current produced in the front of the plasmoid separates from the plasmoid and coalesces to the force-free current loop associated with the magnetic reconnection. The core of the plasmoid stays outside the reconnection region, maintaining high density. The core can be confined by the current system produced around the plasmoid. This collison process between a current loop and a plasmoid may explain the triggering of solar flares observed byYohkoh.     

Deformation mechanisms and fluid behavior in a shallow, brittle fault zone during coseismic and interseismic periods: Results from drill core penetrating the Nojima Fault, Japan

Abstract This paper describes the results of petrographical and meso- to microstructural observations of brittle fault rocks in cores obtained by drilling through the Nojima Fault at a drilling depth of 389.52 m. The zonation of deformation and alteration in the central zone of the fault is clearly seen in cores of granite from the hanging wall, in the following order: (i) host rock, which is characterized by some intragranular microcracks and in situ alteration of mafic minerals and feldspars; (ii) weakly deformed and altered rocks, which are characterized by transgranular cracks and the dissolution of mafic minerals, and by the precipitation of zeolites and iron hydroxide materials; (iii) random fabric fault breccia, which is characterized by fragmentation, by anastomosing networks of transgranular cracks, and by the precipitation of zeolites and iron hydroxide materials; and (iv) fault gouge, which is characterized by the precipitation of smectite and localized cataclastic flow. This zonation implies that the fault has been weakened gradually by fluid-related fracturing over time. In the footwall, a gouge layer measuring only 15 mm thick is present just below the surface of the Nojima Fault. These observations are the basis for a model of fluid behavior along the Nojima Fault. The model invokes the percolation of meteoric fluids through cracks in the hanging wall fault zone during interseismic periods, resulting in chemical reactions in the fault gouge layer to form smectite. The low permeability clay-rich gouge layer sealed the footwall. The fault gouge was brecciated during coseismic or postseismic periods, breaking the seal and allowing fluids to readily flow into the footwall, thus causing a slight alteration. Chemical reactions between fluids and the fault breccia and gouge generated new fault gouge, which resealed the footwall, resulting in a low fluid condition in the footwall during interseismic periods.     

Relation Between Coronal Hole Areas and Solar Wind Speeds Derived from Interplanetary Scintillation Measurements

We investigate the relation between coronal hole (CH) areas and solar wind speeds during 1995?–?2011 using the potential field (PF) model analysis of magnetograph observations and interplanetary scintillation (IPS) observations by the Institute for Space-Earth Environmental Research (formerly Solar-Terrestrial Environment Laboratory) of Nagoya University. We obtained a significant positive correlation between the CH areas (\(A\)) derived from the PF model calculations and solar wind speeds (\(V\)) derived from the IPS observations. The correlation coefficients between them are usually high, but they drop significantly in solar maxima. The slopes of the \(A\)?–?\(V\) relation are roughly constant except for the period around solar maximum, when flatter or steeper slopes are observed. The excursion of the correlation coefficients and slopes at solar maxima is ascribed partly to the effect of rapid structural changes in the coronal magnetic field and solar wind, and partly to the predominance of small CHs. It is also demonstrated that \(V\) is inversely related to the flux expansion factor (\(f\)) and that \(f\) is closely related to \(A^{-1/2}\); hence, \(V \propto A^{1/2}\). A better correlation coefficient is obtained from the \(A^{1/2}\)?–?\(V\) relation, and this fact is useful for improving space weather predictions. We compare the CH areas derived from the PF model calculations with He i 1083 nm observations and show that the PF model calculations provide reliable estimates of the CH area, particularly for large \(A\).     

Determination of phase transition pressures of ZnTe under quasihydrostatic conditions

Pressure behavior of ZnTe at room temperature was studied using an X-ray energy dispersive method on a DIA type cubic anvil apparatus (SAM-85) at NSLS-X17B1. By using powdered polyethylene, the sample and NaCl for a pressure scale were held under quasihydrostatic conditions, which were confirmed by X-ray diffraction method. Two high-pressure phase transitions were confirmed using X-ray powder diffraction simultaneously with electrical resistance measurements. The phase transition pressures under quasihydrostatic conditions were determined to be 9.6 GPa, at which the resistance increased, and 12.0 GPa, which was the midpoint of a large resistance decrease. Errors in the pressure determinations were estimated to be less than 0.2 GPa. These pressure values may depend on grain size and anisotropic stress effects on the calibrant. From X-ray observation of ZnTe, the bulk modulus of the zinc blende structure was calculated to beK ₀=51(3) GPa andK ₀ =3.6(0.8), and the first transition at 9.6 GPa was found to have about 9% volume change. It was consistent with an anomaly in the pressure generating curves.     

Holocene environmental changes of the Hwajinpo Lagoon on the eastern coast of Korea

Lithologic and geochemical data of a core from the Hwajinpo Lagoon, located on the eastern coast of Korea, provided the evolutionary history of the lagoon related to Holocene sea-level changes of the East Sea (Sea of Japan). Grain size analysis, water content analysis, and soft X-ray analysis of core samples were used to reconstruct sedimentary environments, as were total organic carbon, C/N, S and C/S chemical records. Assemblages of mollusc and diatom remains also provided paleoenvironmental information. The reconstruction of paleoenvironments from these multi-proxy data allows the establishment of an evolutionary model of the Hwajinpo Lagoon. The environmental changes of the Hwajinpo Lagoon can be divided into seven different depositional facies: (l) Exposed basement rock; (2) Estuarine; (3) Stagnant brackish lagoon (isolated); (4) Oxic condition lagoon (organic activity); (5) Fresh water lake; (6) Oxic brackish lagoon (recent condition); (7) Prograding river delta. These environmental changes can be related to sea-level change during the Holocene. The trends of sea-level change in the Hwajinpo Lagoon from this study can be compared to those of the Japanese coastal areas located on the other side of the East Sea such as Lakes Shinji and Nakaumi.