A Late Winter Hydrography in Hidaka Bay, South of Hokkaido, Japan

Hydrographic observations in Hidaka Bay, south of Hokkaido, Japan were carried out in late winter 1996 and 1997 to examine the spatial distributions and circulation features of two different water masses, i.e., Coastal Oyashio Water (COW) and Tsugaru Warm Water (TWW), and their modifications. It is known that COW is mostly composed of cold and low-salinity water of the melted drift ice coming from the Okhotsk Sea and flows into Hidaka Bay from winter to spring and TWW with high-salinity continuously supplies from the Tsugaru Strait to the North Pacific. Cold surface mixed layers (<26.2σ_θ, 0–100 m depth) were found mainly over the shelf slope, confirming that anti-clockwise flow of COW was formed. TWW was relatively high in salinity and low in potential vorticity, and had some patch-like water masses with a temperature and salinity maximum in the limited area in the further offshore at the deeper density levels of 26.6–26.8σ_θ. The fine structure of vertical temperature and salinity profiles appeared between TWW and COW is an indication of enhanced vertical mixing (double-diffusive mixing), as inferred from the estimated Turner angles. At a mouth of the Tsugaru Strait in late winter 1997, a significant thermohaline front between TWW and the modified COW was formed and a main path of TWW spreaded south along the Sanriku coast, probably as the bottom controlled flow. Hence, the patch-like TWW observed in late winter is isolated from the Tsugaru Warm Current and then rapidly modified due to a diapycnal mixing. This revised version was published online in August 2006 with corrections to the Cover Date.     

Tsunamis from the Arica-Tocopilla source region and their effects on ports of Central Chile

The last great earthquake in northern Chile took place in 1877, and the ensuing tsunami affected not only that region but also Central Chile. For example, the Bay of Concepción, which is located 1,500 km south of the tsunami source, experienced an inundation height of around 3 m. Ports are important in the Chilean economy, due to the fact that a large percentage of Chilean exports (excluding copper) use ports located in Central Chile. With this in mind, the authors investigated the potential effect of an 1877-like tsunami on the main ports of Central Chile. To do this, the dispersive wave model Non-hydrostatic Evolution of Ocean WAVEs was used. In addition, the first tsunami forecast model for Talcahuano, inside the Bay of Concepción, was developed by means of numerical simulation of several events of different moment magnitudes. The results showed that most of the important ports (Valparaiso, San Antonio, San Vicente and Coronel) had inundation heights on the order of just 1 m, while inundation levels in Talcahuano reached up to 3.5 m. The forecast model for Talcahuano uses only earthquake magnitude, focal depth and tide level to determine tsunami inundation heights. In addition, the tsunami arrival time was computed to be 3 h, and the maximum tsunami amplitude takes place at 4 h and 45 min after the earthquake.     

Occurrence of uranium in metasedimentary enclaves within basement granite, near Peddur and Kottur, Karimnagar District, Andhra Pradesh

Several radioactive anomalies due to uranium and thorium, associated with the mesedimentary enclaves (Archaean) within granite (Archaean to Early-Proterozoic) have been recorded in parts of Karimnagar Granulite Terrain, Karimnagar Dist. At Peddur and Kottur, Uraninite has been identified in the samples of metasediments. The metasediment from these two places have been subjected to granulite facies of metamorphism and host high values of uranium with negligible thorium. In Peddur, samples of metasediments have assayed as high as 1.96% U₃O₈ with negligible thorium, and in Kottur up to 0.059% U₃O₈. Leaching studies on these samples have indicated that most of the U₃O₈ present is leachable. This discovery has opened up the possibility of finding uranium mineralisation in Archaean metasediments and thus provides a thrust for uranium exploration in similar geological environs in India. Further, the basement granite along with the metasedimentary enclaves has the potential to act as a provenance for a possible unconformity type or sandstone type U-deposit in the rocks of overlying Pakhal and Gondwana Supergroup, in Pranhita-Godavari Basin, situated to the east of this area.     

The economic impact of future increase in tropical cyclones in Japan

This article estimates the non-first-order economic loss in Japan due to a future increase in tropical cyclones. One possible effect of global warming could be the increase in intensity of tropical cyclones. Using historical storm tracks between the years 1978 and 2007 and altering their intensities due to this potential increase in their intensity, this paper calculates the future potential regional GDP loss in a certain area that is affected by tropical cyclones. Most of the literature is concerned with physical damage and the loss of lives due to tropical cyclones. However, there are additional economic costs when sustained wind speeds are higher than 30 knots (55.56 km/h), a level that generally will lead to a precautionary cessation of many human activities. Using a Monte Carlo simulation, the paper calculates the potential economic costs for the year 2085 under a climate change scenario with a linear one-per cent yearly increase in CO₂. Using a spatial distribution of economic activity in Japan, it is possible to forecast which parts of the country are likely to experience the highest loss risk.     

Spectral speckle interferometry

A method of obtaining an objective prism spectrum of a stellar object with diffraction-limited spatial resolution is described.Paper presented at the Symposium on the JNLT and Related Engineering Developments, Tokyo, November 29–December 2, 1988.     

Origin of sapphirine-bearing garnet-orthopyroxene granulites: possible hydrothermally altered ocean floor

Sapphirine is a metamorphic mineral that forms in the deep crust in rocks with distinctive bulk compositions, in particular high concentrations of Mg and Al. This study investigates a thin, discontinuous layer of sapphirine-bearing garnet-orthopyroxene (SGO) granulite within a Palaeoproterozoic mafic granulite together with metamorphosed mafic and ultramafic rocks, micaceous rocks rich in magnetite and pyrite, and marble. All of these rocks occur within a low-strain zone in the Lewisian complex of South Harris, NW Scotland. Data on mineral compositions and major, trace, and rare earth element (REE) patterns provide evidence for the origin of the precursor of the SGO granulite. The host mafic granulite has a trace element signature and REE pattern comparable with that of E-type MORB. The chemical abundances of Nb, Ta, La, Ce, Nd, Zr, Hf, Ti, and V in the SGO granulite, except for one sample that records total element loss, are similar to those of the host mafic granulite; however, in terms of whole-rock element abundances, the former is relatively enriched in MgO and depleted in CaO, Na₂O, MnO, Sr, and Eu. Elements within the SGO granulite that were apparently unaffected by hydrothermal alteration—V, Y, Zr, and Cr—are within the range of values observed in the host mafic granulite. Sm–Nd whole-rock isotope systematics suggest that both the host mafic granulite and SGO granulite were metamorphosed at 1.9 Ga, and the Nd initial ratio is consistent with a MORB source at that time. There is no significant difference in the Nd values of the two rock types, suggesting that they originally belonged to the same protolith. Chemical trends within a narrow zone between the SGO and host rock granulite suggest that the former was derived from a basaltic precursor of the latter by a process of infiltration metasomatism, comparable with the chemical exchange that takes place when hydrothermal fluids in present-day oceanic crust pass through vents in a “recharge zone.” The geological and chemical relations observed in the South Harris rocks are consistent with the following model: hydrothermally altered oceanic basaltic crust was trapped in an accretionary wedge and subducted, followed by granulite-facies metamorphism in a deep continental environment during arc–continent collision. This is the first report of hydrothermally altered oceanic crust that was converted to sapphirine-bearing granulite deep in the continental crust.     

Modelling a storm surge under future climate scenarios: case study of extratropical cyclone Gudrun (2005)

Weather Research and Forecasting atmosphere model and Finite Volume Community Ocean Model were for the first time used under the pseudo-climate simulation approach, to study the parameters of an extreme storm in the Baltic Sea area. We reconstructed the met-ocean conditions during the historical storm Gudrun (which caused a record-high +275 cm surge in Pärnu Bay on 9 January 2005) and simulated the future equivalent of Gudrun by modifying the background conditions using monthly mean value differences in sea surface temperature (SST), atmospheric air temperature and relative humidity from MIROC5 in accordance with the IPCC scenarios RCP4.5 and RCP8.5 for 2050 and 2100. The simulated storm route and storm surge parameters were in good accordance with the observed ones. Despite expecting the continuation of recently observed intensification of cyclonic activity in winter months, our numerical simulations showed that intensity of the strongest storms and storm surges in the Baltic Sea might not increase by the end of twenty-first century. Unlike tropical cyclones, which derive their energy from the increasing SST, the extratropical cyclones (ETCs) harvest their primary energy from the thermal differences on the sides of the polar front, which may decrease if the Arctic warms up. For climatological generalizations on future ETCs, however, it is necessary to re-calculate a larger number of storms, including those with different tracks and in different thermal conditions.     

Blowout mechanism of Alasehir (Turkey) geothermal field and its effects on groundwater chemistry

Anatolia region is one of the most seismically active regions in the world and has a considerably high level of geothermal energy potential. Some of these geothermal resources have been used for power generation and direct heating. Most of the high enthalpy geothermal systems are located in western part of Turkey. Alasehir is the most important geothermal site in western part of Turkey. Many geothermal wells have been drilled in Alasehir Plain to produce the geothermal fluid from the deep reservoir in the last 10 years. A blowout accident happened during a geothermal well drilling operation in Alasehir Plain, and significant amount of geothermal fluid surfaced out along the fault zone in three locations. When drilling string entered the reservoir rock about 1000 m, blowout occurred. As the well head preventer system was closed because of the blowout, high-pressure fluid surfaced out along the fault zone cutting the Neogene formation. In order to understand the geothermal fluid effects on groundwater chemistry, physical and chemical compositions of local cold groundwater were monitored from May 2012 to September 2014 in the study area. The geothermal fluid was found to be of Na–HCO₃ water type, and especially, arsenic and boron concentrations reached levels as high as 3 and 127 mg/L, respectively. The concentrations of arsenic and boron in the geothermal fluid and groundwater exceeded the maximum allowable limits given in the national and international standards for drinking water quality. According to temporally monitored results, geothermal fluid has extremely high mineral content which influenced the quality of groundwater resources of the area where water resource is commonly used for agricultural irrigation.