Tidal and solar cycle effects on the OI 5577 Å, NaD and OH(8,3) airglow emissions observed at 23°S

The upper mesosphere airglow emissions OI 5577, NaD and OH have been observed at Cachoeira Paulista (22.7°S; 45.0°W) Brazil. Nocturnal variations and their seasonal dependencies in amplitude and phase, and the annual variations of these emissions are presented, analysing the data obtained from 1977 to 1982 during the ascending phase of the last solar cycle. The nocturnal variations of the OI 5577 emission and the OH rotational temperature showed a significant semidiurnal oscillation, with the phase of maximum moving from midnight in January to early morning in June. Semiannual variation of the OI 5577 and NaD emissions with the maximum intensities in April/May and October/November were observed. The OH rotational temperature, however, showed an annual variation, maximum in summer and minimum in winter, while no significant seasonal variation was found in the OH emission intensities. Long-term intensity variations are also presented with the solar sunspot numbers and the 10.7 cm flux.     

A methodology for estimating business interruption loss caused by flood disasters: insights from business surveys after Tokai Heavy Rain in Japan

This study proposes a probabilistic methodology for estimating the business interruption loss of industrial sectors as an extension of current methodology. The functional forms and parameters are selected and calibrated based on survey data obtained from businesses located in the inundated area at the time of the 2000 Tokai Heavy Rain in Japan. The Tokai Heavy Rain was a rare event that hit a densely populated and industrialized area. In the estimation of business interruption losses, functional fragility curves and accelerated failure time models are selected to estimate the extent of damage to production capacity and production recovery time. Significant explanatory variables, such as inundation depth, distinct vulnerability, and the resilience characteristics of each sector, as well as the accuracy of fit of the model, are analyzed in the study. The function obtained and the estimated parameters can be utilized as benchmarks in estimating the probabilistic distribution of business interruption losses, especially in the case of urban flood disasters.

     

Factors regulating the distribution of elements in marine sediments predicted by a simulation model

The contents of oxyanionic elements (V, Se and Mo) and cationic transition metals (Mn, Fe, Co, Ni, Cu and Zn) in sediments from near-shore to deep-sea environments were measured to clarify factors regulating the distribution of these elements in marine sediments. For cationic transition metals of which contents increase from near-shore to deep-sea environments, the chemical composition of pelagic clays is modeled by a mixture of aluminosilicates having the chemical composition of average shale and Fe–Mn oxides having the chemical composition of associated manganese nodules. The content of V is fairly constant in sediments from near-shore to deep-sea areas. The mixture model of average shale and manganese nodules holds also for V, although most of the V is located in the aluminosilicate lattices. The content of Se in the near-shore sediments is higher and that in the deep-sea sediments is lower than that in average shale. The high content in the near-shore sediments is interpreted as the addition of biogenic materials to aluminosilicates with average shale composition and the low content in deep-sea sediments is explained by oxidative release of Se from aluminosilicates. The content of Mo in sediments increases from near-shore to deep-sea environments. The general distribution of Mo in marine sediments is expressed by the mixture model. An anomalously high content of Mo in a near-shore sediment is attributed to adsorption of molybdate on manganese oxides.     

Sedimentary records of multidecadal-scale variability of diatom productivity in the Bungo Channel, Japan, associated with the Pacific Decadal Oscillation

In order to examine the responses of primary productivity in the southern coastal sea of Japan to the Pacific Decadal Oscillation (PDO) in the 20th century, sedimentary records of diatom productivity (diatom valve fluxes) were reconstructed using core samples from the Bungo Channel (BC) in southwest Japan. The record of the Thalassionema spp. flux—the best index of fall primary productivity in the BC—indicated a multidecadal-scale duration with a low flux (1943–1982) and those with a high flux (1913–1943 and 1982–2001); apparent shifts were recognized in 1943 and 1982. The shift in 1982 was also recognized in the flux records of other early summer to fall predominant genera in the BC and, previously, in the biogenic silica records from a broad region of the southeast BC. This indicates that in our records, this shift reflects a general trend in the primary production in the southeast BC. A comparison among the Thalassionema spp. flux records, meteorological data from an observatory adjacent to the core site, and the PDO index showed that the flux records were more similar to the PDO index than the other meteorological records, which suggests that the multidecadal-scale variability of the BC primary productivity may be associated with some marine-derived forcing. The bottom intrusions of nutrient-rich water that upwelled from the shelf slope into the BC, the axis movement or the transport of the Kuroshio Current off the BC, and a basin-scale wind stress in the North Pacific might play an important role in this forcing and mediate between the BC primary productivity and the PDO.     

2-D and 3-D modelling of wide-angle seismic data: an example from the Vøring volcanic passive margin

This study presents the modelling of 2-D and 3-D wide-angle seismic data acquired on the complex, volcanic passive margin of the Vøring Plateau, off Norway. Three wide-angle seismic profiles were shot and recorded simultaneously by 21 Ocean Bottom Seismometers, yielding a comprehensive 3-D data set, in addition to the three in-line profiles. Coincident multi-channel seismic profiles are used to better constrain the modelling, but the Mesozoic and deeper structures are poorly imaged due to the presence of flood basalts and sills. Velocity modelling reveals an unexpectedly large 30 km basement high hidden below the flood basalt. When interpreted as a 2-D structure, this basement high produces a modelled gravity anomaly in disagreement with the observed gravity. However, both the gravity and the seismic data suggest that the structure varies in all three directions. The modelling of the entire 3-D set of travel times leads to a coherent velocity structure that confirms the basement high; it also shows that the abrupt transition to the slower Cretaceous basin coincides in position and orientation with the fault system forming the Rån Ridge. The positive gravity anomaly over the Rån Ridge originates from the focussed and coincident elevation of the high velocity lower crust and pre-Cretaceous basement. Although the Moho is not constrained by the seismic data, the gravity modelled from the 3-D velocity model shows a better fit along the profiles. This study illustrates the interest of a 3-D acquisition of wide-angle seismic over complex structures and the benefit of the subsequent integrated interpretation of the seismic and gravity data.     

Caprella watch: a new approach for monitoring butyltin residues in the ocean

A comparative study on the butyltin levels in various organisms showed that marked bioaccumulation occurs in certain lower trophic levels; i.e. from seawater to phytoplankton and into caprellid amphipods, Caprella spp. Caprella spp., which inhabit algal communities and aquaculture beds in the subtidal zone, are small crustaceans with reduced movement and a life-span of less than 3 months. These characteristics indicate that Caprella spp. may be well-suited for monitoring butyltin residue changes over small spatial and temporal scales. Two groups of organisms, mussels and neogastropods, have been mainly used for monitoring butyltin in shallow water ecosystems. These invertebrates mainly inhabit the intertidal zone where the butyltin levels vary widely depending on the immersion period and exposure to the sea surface microlayer. Monitoring using neogastropods may also over estimate exposures after restrictions on tributyltin, since neogastropods show an irreversible response to residue changes owing to their long life-spans. Thus, we propose usage of Caprella spp. to monitor temporal and spatial changes in baseline concentrations of butyltins.