Fast and slow timescales in the tropical low-cloud response to increasing CO2 in two climate models

To obtain physical insights into the response and feedback of low clouds (C _l ) to global warming, ensemble 4?×?CO₂ experiments were carried out with two climate models, the Model for Interdisciplinary Research on Climate (MIROC) versions 3.2 and 5. For quadrupling CO₂, tropical-mean C _l decreases, and hence, acts as positive feedback in MIROC3, whereas it increases and serves as negative feedback in MIROC5. Three time scales of tropical-mean C _l change were identified—an initial adjustment without change in the global-mean surface air temperature, a slow response emerging after 10–20?years, and a fast response in between. The two models share common features for the former two changes in which C _l decreases. The slow response reflects the variability of C _l associated with the El Ni?o-Southern Oscillation in the control integration, and may therefore be constrained by observations. However, the fast response is opposite in the two models and dominates the total response of C _l . Its sign is determined by a subtle residual of the C _l increase and decrease over the ascending and subsidence regions, respectively. The regional C _l increase is consistent with a more frequent occurrence of a stable condition, and vice versa, as measured by lower-tropospheric stability (LTS). The above frequency change in LTS is similarly found in six other climate models despite a large difference in both the mean and the changes in the low-cloud fraction for a given LTS. This suggests that the response of the thermodynamic constraint for C _l to increasing CO₂ concentrations is a robust part of the climate change.     

Modification to the crystal structure of chlorite during early stages of its dissolution

Early stage processes of Mg-rich chlorite (clinochlore) dissolution were examined, focusing especially on the structural modification at grain edges during dissolution. Focused ion beam transmission electron microscopy sample preparation was applied to crystals dissolved in a flow-through reaction system at pH 3.0 and 25°C for 31 days. The obtained Si and Mg dissolution rates are −11.49 and −11.14 (logR, mol/(m²/s)), respectively, implying dissolution is non-stoichiometric. TEM-EDX analyses of dissolved samples reveal the development of 20–50-nm thick amorphous zone at an outermost rim with a chemical gradient of Mg, lower towards the solid surface, and Si enrichment in this amorphous zone. Crystalline material is partially interwoven with amorphous one at the interface between the amorphous and crystalline regions. These results indicate that the amorphous zone was produced by selective leaching of cations except for Si. Chlorite dissolution may proceed via the formation and thickening of leached layer as a by-product of release to solution of Si at slightly slower rate than Mg.     

An empirical probabilistic approach for constraining the uncertainty of long-term solute transport predictions in fractured rock using in situ tracer experiments

Although radionuclide tracer tests have been carried out for over 30  years, the role of tracer tests in radioactive waste repository performance assessment (PA) has been questioned due to the differences between the time scales for tracer tests and PA. The possibility of using in situ tracer tests to constrain PA time scale (over 10,000  years) solute transport has been demonstrated using a systematic “microstructural model” approach to define advective and retentive materials. A series of simulations were conducted of the “TRUE-1” sorbing solute transport experiments in a well-characterized block of fractured granite. These experiments were then used to constrain the uncertainty of long-term transport on the same pathways, using a gradient several orders of magnitude smaller. The comparison of uncertainty of this long-term transport, with and without this conditioning step, provided a measure of the ability of tracer tests to reduce PA time-scale uncertainty. Although this approach for quantifying uncertainty reduction is somewhat empirical, it does indicate the potential usefulness of tracer experiments in reducing the uncertainty of the key PA time-scale transport parameters such as the flow wetted surface, provided that immobile zone properties such as sorption (Kd), porosity and diffusivity are available.     

Coupling fluvial processes and landslide distribution toward geomorphological hazard assessment: a case study in a transient landscape in Japan

This study quantified the relationship among deep-seated gravitational slope deformations (DGSDs), landslides, and river rejuvenation in the upper reaches of the Kumano River in the Kii Mountains of Japan, an area of frequent bedrock landslides. River profiles and hillslope landforms were examined, and high-resolution digital elevation models (DEMs) were used to identify DGSDs and landslides. Many of the deep-seated landslides were associated with rainstorms in 1889 and 2011. Landslide volumes were related to landslide areas on the basis of 52 deep-seated landslides that failed during the 2011 rainfall, providing basic data for landscape denudation and sediment yield. River rejuvenation occurred stepwise, incising moderate relief paleosurfaces and forming two series of knickpoints and V-shaped inner gorges that are up to 400-m deep. More than 65% of DGSDs and 75% of the landslides were located in association with the incised inner gorges along the peripheries of the paleosurfaces or were entirely contained within the inner gorges. DGSDs and landslides associated with the incised inner valley slopes tended to be larger than those developed within the paleosurfaces and may be long-term transient hillslope responses to river incision. Hillslope undercutting caused by rejuvenated river incision may play an important role in long-term slope stability and distribution of mass movements, and could serve as an indicator of landslide hazard.     

Determination of Abundances of Fifty‐Two Elements in Natural Waters by ICP‐MS with Freeze‐Drying Pre‐concentration

To precisely determine the abundances of fifty‐two elements found within natural water samples, with mass fractions down to fg g^?1 level, we have developed a method which combines freeze‐drying pre‐concentration (FDC) and isotope dilution internal standardisation (ID‐IS). By sublimation of H₂O, the sample solution was reduced to < 1/50 of the original volume. To determine element abundance with accuracy better than 10%, we found that for solutions being analysed by mass spectrometry the HNO₃ concentration should be > 0.3 mol l^?1 to avoid hydrolysis. Matrix‐affected signal suppression was not significant for the solutions with NaCl concentrations lower than 0.2 and 0.1 cg g^?1 for quadrupole ICP‐MS and sector field ICP‐MS, respectively. The recovery yields of elements after FDC were 97–105%. The detection limits for the sample solutions prepared by FDC were ≤ 10 pg g^?1, except for Na, K and Ca. Blanks prepared using FDC were at pg‐levels, except for eleven elements (Na, Mg, Al, P, Ca, Mn, Fe, Co, Ni, Cu and Zn). The abundances of fifty‐two elements in bottled drinking water were determined from five different geological sources with mass fractions ranging from the fg g^?1 to μg g^?1 level with high accuracy.     

Resistivity mapping using the VLF-MT method around surface fault ruptures of the 1995 Hyogo-ken Nanbu earthquake, Japan

Abstract Distinctive fault ruptures, the Nojima Fault and Ogura Fault, appeared along the northwestern coast of Awaji Island at the time of the 1995 Hyogo-ken Nanbu earthquake (Kobe earthquake). In order to delineate the shallow resistivity structures around the faults just after they formed, Very Low Frequency Magnetotelluric (VLF-MT) surveys were made at five sites along the Nojima Fault and at one site along the Ogura Fault. Fourteen transects were made at the one site on the Ogura Fault, and another transect covers the area between the two faults. Changes in apparent resistivity or phase, or both, commonly occur when crossing the surface location of one of the faults, except for the northern transects at OGR-0 on the Ogura Fault. Apparent resistivity values of less than 100 Ωm were observed for Tertiary and Quaternary sediments and values larger than 200 Ωm for granitic rocks. The resistivity structures are related to the morphological characteristics of the fault ruptures. Remarkably conductive zones (less than 10 Ωm in apparent resistivity and 30–40 m in width) were found where the surface displacement is distinct and prominent along a single fault plane. If remarkably conductive zones were formed at the time of the 1995 Hyogo-ken Nanbu earthquake, the results provide a good constraint on the dimensions of a conductive zone near the surface that was made by one earthquake. Alternatively, if characteristic resistivity structures existed prior to the earthquake, the conductive zone was probably formed by some tens of earthquakes in relatively modern times. In this case, this phenomenon is inferred to be a concentration of fracturing in a narrow zone and is associated with the formation of clay minerals, which enhance rock conductivity.     

Development of a Finite Element Simulator for Crustal Deformation with Large Fault Slipping

--In this paper, a finite element model for simulating long-term crustal deformation with large slipping along fault interface is developed, where a rate- and state-dependent frictional law is introduced to represent the faulting processes and frictional behaviors of fault interface. Moreover, viscous and plastic material properties are used to simulate pressure solution creep and cataclasis, respectively. Throughout the simulations on a structural model of fault-bend folds, the distributions of the stress invariants, equivalent viscous plastic strain, and the traction on the fault interface are investigated. The sequence of deformation mechanisms during movement over a ramp is discussed. It is also found that this kind of frictional model is suitable to represent the rate-dependent behavior of fault slipping due to the movement over a ramp and the tractions on fault interface for treating the low frictional problem of fault-bend folds.     

Regional energetics over the North Pacific,South China Sea and the Indonesian seas during winter

The energy equation was applied to four limited regions to investigate the basic mechanisms through which area-averaged eddy kinetic energy is maintained during the northern winter. The regions selected for this study are as follows: extratropical North Pacific (24.2°N–44.6°N, 130°E–150°W), tropical eastern North Pacific (0°–19.6°N, 170°W–110°W), South China Sea and. Bay of Bengal (0°–19.6°N, 80°E–140°E), and Timor Sea and eastern Indian Ocean (0°–19.6°S, 80°E–140°E). The zonally averaged upper flows over the first region were found to be barotropically stable. In contrast, they were barotropically unstable over the second region; namely, eddy motions over the tropical eastern North Pacific are maintained by receiving energy from zonal flows via barotropic interaction. The third and fourth regions are characterized by the importance of the conversion process between eddy available potential and eddy kinetic energy.Contribution No. 77-5, Department of Meteorology, University of Hawaii, USA.     

Partitioning of heavy metals into mineral and organic fractions in a sediment core from Tokyo Bay

Sediment core was collected from Tokyo Bay. The surface enrichment of heavy metals due to human activities is recognized in the sediment. Partitioning of Cu, Zn, Fe and Mn into sulfide, carbonate, organic and silicate fractions has been determined with selective chemical leaching techniques for ²¹⁰Pb-dated sediment core samples. The heavy metal contents of silicate fractions without exchangeable sites are almost constant against depth in sediment core. However, the Cu, Zn and Mn contents of sulfide, carbonate and organic fractions vary with depth. Most Cu and Zn in the polluted sediment layer are associated with the iron sulfide fraction.     

Thermal diffusivity of stishovite

The thermal diffusivity of synthetic polycrystalline stishovite was determined by the Ångstrom method in the temperature range 300–550 K at 1 atm. The calculated thermal conductivity of stishovite at 300 K is 0.086 W cm^?1 K^?1 which is comparable to that for TiO₂-rutile but much lower than for GeO₂ and SnO₂. The observed thermal conductivities of rutile-structure oxides increase systematically with increasing density, in contrast with the expected behavior for isostructural compounds.