Probable effects of CO2-induced climatic warming on the thermal environment of ponded shallow water

A physical model was developed for describing the thermal environment of ponded shallow water as a model for rice fields in relation to climatic conditions. The model was used to assess probable effects of CO₂-induced warming on the thermal conditions of ponded shallow water. It was assumed that an altered equilibrium climate was produced by atmospheric CO₂ which was twice that of present levels. The 1951–80 climatic means of Japan were used as baseline data. Water temperature and energy balance characteristics predicted from the model were compared between both climates. The most notable results were that water temperature under CO₂ doubling rose 2 to 4 °C. These increases in temperature would induce a remarkable northward shift of the 15 °C isotherm which characterizes the isochrone of safe transplanting dates for rice seedlings. CO₂-warming would have a considerable influence on the energy balance characteristics, intensifying the evaporation rate from the water surface. Changes in thermal conditions of rice fields due to CO₂-induced climatic warming are, therefore, expected to bring about significant effects on aquatic environments and the life forms they support.     

Fine structure in photoluminescence spectrum of S<Subscript>2</Subscript><Superscript>−</Superscript> center in sodalite

The photoluminescence and excitation spectra of sodalites from Greenland, Canada and Xinjiang (China) are observed at 300 and 10 K in detail. The features of the emission and excitation spectra of the orange-yellow fluorescence of these sodalites are independent of the locality. The emission spectra at 300 and 10 K consist of a broad band with a series of peaks and a maximum peak at 648 and 645.9 nm, respectively. The excitation spectra obtained by monitoring the orange-yellow fluorescence at 300 and 10 K consist of a main band with a peak at 392 nm. The luminescence efficiency of the heat-treated sodalite from Xinjiang is about seven times as high as that of untreated natural sodalite. The emission spectrum of the S₂ ⁻ center in sodalite at 10 K consists of a band with a clearly resolved structure with a series of maxima spaced about 560 cm⁻¹ (20–25 nm) apart. Each narrow band at 10 K shows a fine structure consisting of a small peak due to the stretching vibration of the isotopic species of ³²S³⁴S⁻, a main peak due to that of the isotopic species of ³²S₂ ⁻ and five peaks due to phonon sidebands of the main peak.     

Direct correlation of radiolarian <Emphasis Type="Italic">Kilinora spiralis</Emphasis> Zone with the Late Jurassic ammonite faunal succession in the Kurisaka Formation,Kurosegawa Terrane,SW Japan

The last appearance datum of the radiolarian Kilinora spiralis is recorded above the first appearance datum of the ammonite Ataxioceras (A.) kurisakense in the Todoro Section of the Kurisaka Formation, Southern Kurosegawa Terrane, Shikoku, SW Japan. The constraint by ammonite age prolongs the range of the Kilinora spiralis Zone, a remarkable Jurassic radiolarian zone in Japan-NW Pacific region, into the lower Kimmeridgian. The direct correlation of the Kilinora spiralis zone with the Late Jurassic ammonite faunal succession in the Kurisaka Formation will provide a clue to the still pending chronological difference between European and North American radiolarian zones.     

Advances in computational morphodynamics using the International River Interface Cooperative (iRIC) software

Results from computational morphodynamics modeling of coupled flow–bed–sediment systems are described for 10 applications as a review of recent advances in the field. Each of these applications is drawn from solvers included in the public-domain International River Interface Cooperative (iRIC) software package. For mesoscale river features such as bars, predictions of alternate and higher mode river bars are shown for flows with equilibrium sediment supply and for a single case of oversupplied sediment. For microscale bed features such as bedforms, computational results are shown for the development and evolution of two-dimensional bedforms using a simple closure-based two-dimensional model, for two- and three-dimensional ripples and dunes using a three-dimensional large-eddy simulation flow model coupled to a physics-based particle transport model, and for the development of bed streaks using a three-dimensional unsteady Reynolds-averaged Navier–Stokes solver with a simple sediment-transport treatment. Finally, macroscale or channel evolution treatments are used to examine the temporal development of meandering channels, a failure model for cantilevered banks, the effect of bank vegetation on channel width, the development of channel networks in tidal systems, and the evolution of bedrock channels. In all examples, computational morphodynamics results from iRIC solvers compare well to observations of natural bed morphology. For each of the three scales investigated here, brief suggestions for future work and potential research directions are offered. © 2019 The Authors Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd     

Pore Creation due to Fault Slip in a Fluid-permeated Fault Zone and its Effect on Seismicity: Generation Mechanism of Earthquake Swarm

—Spatio-temporal variation of rupture activity is modeled assuming fluid migration in a narrow porous fault zone formed along a vertical strike-slip fault in a semi-infinite elastic medium. Pores are assumed to be created in the fault zone by fault slip. The effective stress principle coupled to the Coulomb failure criterion introduces mechanical coupling between fault slip and pore fluid. The fluid is assumed to flow out of a localized high-pressure fluid compartment in the fault with the onset of earthquake rupture. The duration of the earthquake sequence is assumed to be considerably shorter than the recurrence period of characteristic events on the fault. The rupture process is shown to be significantly dependent on the rate of pore creation. If the rate is large enough, a foreshock–mainshock sequence is never observed. When an inhomogeneity is introduced in the spatial distribution of permeability, high complexity is observed in the spatio-temporal variation of rupture activity. For example, frequency-magnitude statistics of intermediate-size events are shown to obey the Gutenberg–Richter relation. Rupture sequences with features of earthquake swarms can be simulated when the rate of pore creation is relatively large. Such sequences generally start and end gradually with no single event dominating in the sequence. In addition, the b values are shown to be unusually large. These are consistent with seismological observations on earthquake swarms.     

Temporal and spatial variations of radiocarbon in Japan Sea bottom water

In 1995 and 2000, the radiocarbon ratio (Δ¹⁴C) of total dissolved inorganic carbon was measured in the Japan Sea where deep and bottom waters are formed within the sea itself. We found that (1) since 1979, the Δ¹⁴C in bottom water below about 2000-m depth in the western Japan Basin (WJB) had increased by about 30‰ by 1995, and (2) the bottom Δ¹⁴C in the WJB did not change between 1995 and 2000. The former finding was due to penetration of surface bomb-produced radiocarbon into the bottom water owing to bottom ventilation, whereas the latter was caused by stagnation of the bottom ventilation there. In the eastern Japan Basin (EJB), the bottom Δ¹⁴C also increased by about 30‰ between 1979 and 2002. Recent stagnation of the bottom ventilation in the EJB is also suggested from analyses of constant bomb-produced tritium between 1984 and 1999. The temporal variations of Δ¹⁴C, tritium, and dissolved oxygen in the bottom waters indicate that: (1) new bottom water is formed south of Vladivostok in the WJB only in severe winters; and (2) the new bottom water then follows the path of a cyclonic abyssal circulation of the Japan Sea, which results in the increases in dissolved oxygen and the transient tracers in the bottom waters in the EJB and Yamato Basin with an approximate 3-to 6-year time lag. This process is consistent with the spatial variations of Δ¹⁴C, bomb-produced ¹³⁷Cs, and chlorofluorocarbon-11 in the bottom waters of the Japan Sea.     

Coupled process-based cyclone surge simulation for the Bay of Bengal

We have developed a wind-wave-surge coupled process-based numerical model for simulating storm surge, consisting of a meso-scale atmospheric model (MM5), a third-generation spectral wave model (WW3) and a coastal ocean model (POM). We introduced an additional sea surface shear stress by wave dissipation into the model to consider the process of energy transfer from winds to currents through whitecap breaking. We demonstrate the importance of this energy transfer path through a hindcast simulation of a cyclone surge in April, 1991 in the Bay of Bengal: it helps generate mean current and has wave effects on wind-induced current fields in extremely shallow water areas.     

Aturoidea (Nautilida) from the Upper Cretaceous Sada limestone in Shimanto City, Kochi Prefecture, Japan

The first specimen of Aturoidea to be recorded in East Asia has been found in the Upper Cretaceous Sada limestone in Shimanto City, Kochi Prefecture, Japan. The specimen is one of the few representatives from the Upper Cretaceous, along with species known from Libya, Angola, and India. The specimen is very similar to A. mathewsonni from the Paleocene deposits in California. However, we describe the specimen as A. cf. mathewsonni, as it slightly differs from A. mathewsonni in the shape of the lateral lobe of the suture. The finding reveals that Aturoidea had already lived in waters around East Asia in the Late Cretaceous.