Gas capture and rare gas retention by accreting planets in the solar nebula

In this paper, the physico-chemical effects of the nebula gas on the planets are reviewed from a standpoint of planetary formation in the solar nebula.The proto-Earth growing in the nebula was surrounded by a primordial atmosphere with a solar chemical composition and solar isotopic composition. When the mass of the proto-Earth was greater than 0.3 times the present Earth mass, the surface was molten because of the blanketing effect of the atmosphere. Therefore, the primordial rare gasses contained in the primordial atmosphere dissolved into the molten Earth material without fractionation and in particular the dissolved neon is expected to be conserved in the present Earth material. Hence, if dissolved neon with a solar isotopic ratio is discovered in the Earth material, it will indicate that the Earth was formed in the nebula and that the dissolved rare gases were one of the sources which degassed to form the present atmosphere.     

A pair of Langmuir cells in two laboratory tanks (II) on generation mechanism

Vertical and cross-wind profiles of mean currents were measured systematically in vertical cross-sections of two wind-wave tanks with aspect ratios of order one to study the secondary flow in the tanks. A pair of Langmuir cells turned out to be driven by a close combination of the pressure gradient along the tank and the side-wall effects. That is, part of the adverse pressure gradient produced a parabolic cross-wind profile with the smallest downwind current at the centerline and the largest current along the two sidewalls. As a result, upwelling occurred in the center zone where the return flow was strongest, probably because of the entrainment action of the wind-driven current. In order to compensate for this upwelling, downwelling occurred along the two side-walls from the flow continuity. The resulting vertical circulation formed a pair of Langmuir circulations across the span and served to maintain the parabolic profile formed by the pressure gradient. A positive feedback mechanism is thus found between the primary and secondary circulations through upwelling of the return flow in the center zone. Vertical shears of the span-averaged downwind current measured in two tanks were found to be systematically different from each other. This difference seems to depend on the magnitude of the advective Reynolds stresses in the two tanks.     

Possible change in distribution of seaweed, Sargassum horneri, in northeast Asia under A2 scenario of global warming and consequent effect on some fish

Global warming effects on seaweed beds are already perceptible. Their geographical distributions greatly depend on water temperatures. To predict future geographical distributions of brown alga, Sargassum horneri, forming large beds in the northwestern Pacific, we referred to future monthly surface water temperatures at about 1.1° of longitude and 0.6° of latitude in February and August in 2050 and 2100 simulated by 12 organizations under an A2 scenario of global warming. The southern limit of S. horneri distribution is expected to keep moving northward such that it may broadly disappear from Honshu Island, the Chinese coast, and Korean Peninsula in 2100, when tropical Sargassum species such as Sargassum tenuifolium may not completely replace S. horneri. Thus, their forests in 2100 do not substitute those of S. horneri in 2000. Fishes using the beds and seaweed rafts consisting of S. horneri in East China Sea suffer these disappearances.     

Projection of future world water resources under SRES scenarios: an integrated assessment

Abstract

Changes in water resources availability, as affected by global climate warming, together with changes in water withdrawal, could influence the world water resources stress situation. In this study, we investigate how the world water resources situation will likely change under the Special Report on Emissions Scenarios (SRES) by integrating water withdrawal projections. First, the potential changes in water resources availability are investigated by a multi-model analysis of the ensemble outputs of six general circulation models (GCMs) from organizations worldwide. The analysis suggests that, while climate warming might increase water resources availability to human society, there is a large discrepancy in the size of the water resource depending on the GCM used. Secondly, the changes in water-stressed basins and the number of people living in them are evaluated by two indices at the basin scale. The numbers were projected to increase in the future and possibly to be doubled in the 2050s for the three SRES scenarios A1b, A2 and B1. Finally, the relative impacts of population growth, water use change and climate warming on world water resources are investigated using the global highly water-stressed population as an overall indicator. The results suggest that population and socio-economic development are the major drivers of growing world water resources stress. Even though water availability was projected to increase under different warming scenarios, the reduction of world water stress is very limited. The principal alternative to sustainable governance of world water resources is to improve water-use efficiency globally by effectively reducing net water withdrawal.

Editor Z.W. Kundzewicz; Associate editor D. Gerten     

Grain abundance in the primordial atmosphere of the Earth

For models of planetary accumulation in the presence of solar nebular gas, the initial surface temperature of the Earth is controlled by the grain opacity of the atmosphere. The surface temperature in turn controls the quantity of neon dissolved and trapped within the interior of the Earth. To compare accumulation theory with observation calculations have been made of the grain opacity expected to be associated with accumulation in a gaseous nebula. There are two parameters that are in principle determined by the theory, but actually are at present uncertain: the mean eccentricity e of the planetesimal swarm, and the fraction ξ of the accretional energy that is expended in the release of grains into the atmosphere by ablation of the incoming planetesimal. It is found that if the eccentricity of swarm is low (10^?3), rather low values of ξ(10^?5) are required to match the observed neon data. In contrast higher values of ξ are required (10^?1) for the most probable case, intermediate eccentricity (10^?2). For the high eccentricity case (e ～ 0.1) ξ must be >10^?2. The results show that avoidance of excess trapped neon of solar composition places restrictive, but not necessarily impossible, conditions on the parameters of the accumulation theory.     

The calibrated map of the HII region S237 in Hα emission

The difference of spatial distributions between the O-type stars, supernovae and red giant stars found by Riekeet al. (1980) in the nuclear region of M82 can be interpreted if the star formation has been triggered by shock waves expanding from the nucleus with velocities of 100 km s^–1 at 300 pc from the centre and if the explosions have recurrently occurred with time interval of about 2×10⁶ yr. The recurrent formation of such giant compressed gas layer makes the formation rate of massive stars efficient.     

A study of rock alteration process based on kinetics of hydrothermal experiment

Experimental investigation was made on hydrothermal alteration of sericite in acid solution. It is found that the sericite is changed to pyrophyllite through kaolinite at 270° C and 260° C, and the alteration is considered to be a consecutive reaction involving two steps, from sericite to kaolinite and from kaolinite to pyrophyllite. On the other hand, pyrophyllite is not formed at 190° C and the sericite is altered to kaolinite. The rate of reaction in each step of this hydrothermal alteration is dependent on reaction temperature and chemical composition of the solution. From the results of the quantitative analyses of the experimental products, kinetic constants and related parameters were obtained.By using these numerical values, an alteration process can be followed in a given model. Computed results for some cases of an alteration of sericite in acid solution are presented. Geological phenomena such as rock alteration or weathering are thought to progress in a disequilibrium state and in an open system. An attempt described in this paper is a physicochemical approach to treat an alteration process accompanied with material transfer occurring in an open system from a kientic viewpoint.     

Short term variability in the Tsugaru warm current and its effect on fisheries

A study on the short term variability of the ocean and its effects on the distribution of fish shoals in the coastal area of NE Japan has been conducted. The efforts have been made to detect the temporal changes of the Tsugaru Warm Current in summer and autumn (i.e. fishing seasons) by using the satellite infrared images (NOAA7-9) and concurrent hydrographic observation data. Also fish shoal (mackerel and sardine) distribution was investigated by echo-sounder and fishing fleets' operation data. The satellite images revealed that the gyre of the Tsugaru Warm Current changed entirely in a short time, and sometimes the gyre was devided into two parts. The time scale of this process was estimated to be 1–2 weeks. Corresponding to this process, the fishing grounds changed rapidly. A part of the Tsugaru Warm Current flows from the gyre southward along the coast. The flow has a temperature front against the Oyasio water intrusion, showing a wave-like perturbation propagating to the S. At the perturbed frontal area, Mackerel fishing grounds formed frequently. The fish shoals distributed in the warmer side of this frontal zone. By revealing the mechanism of the characteristic variability, the movement of fishing rounds may be predicted.     

Horizontal strain and precision of EDM from repeated surveys of the Precise Geodetic Net of Japan

A simple statistical approach has been applied to the repeated electro-optical distance measurements (EDM) of 1,358 lines in the Tohoku district of Japan to obtain knowledge about the precision of EDM and the possible accumulation of strain. The average time interval between measurements is about seven or eight years. It is shown that the whole data of the difference between distance measurements repeated over a given lineD are interpreted in terms of EDM errors comprising distance proportional systematic errors and standard errors expressed by the usual form . The rate of horizontal deformation must therefore be much smaller than the strain rates of about 0.7 0.8 ppm over 7 to 8 years which have been hitherto expected.