Fluctuations of snow accumulation in the Antarctic and sea level pressure in the Southern Hemisphere in the last 100 years

This paper summarizes the long-term fluctuations of snow accumulation in the Antarctic and analyzes its correlation with the sea level pressure (SLP) in the middle latitude (40°–50° S) of the Southern Hemisphere. Stratigraphic data which were compiled from studies on ice cores and snow-pits at eight stations in the Antarctic were used in the present study. It was found that the data concerning fluctuations in snow accumulation for East Antarctica showed correlations, whereas no such correlation was observed for the data from West Antarctica.This study shows possible relationships between snow accumulation in the Antarctic and SLP in the middle latitudes. The fluctuations of accumulation at South Pole, Dome C, Wilkes and South Ice Point show correlations with SLP over a large area in the 40°–50° S latitudinal zone. For the long-term fluctuations of SLP in the 40°–50 ° S latitudinal zone, a zonal fluctuation with wave number zero structure and a longitudinal variation of SLP anomalies due to their out-of-phase-fluctuation between the Pacific and the Indian Oceans were observed. The temporal scales for these fluctuations were found to be in the order of 20–30 years and 40–60 years, respectively. The influences of these two modes on the behaviour of snow accumulation in the Antarctic is also discussed.Now at Kitami Institute of Technology, Kitami, Hokkaido, Japan.     

Radiometric ages of Alpine metamorphic rocks in the western and central Alps

Abstract The chronological characteristics of Alpine metamorphic rocks are described and Alpine metamorphic events are reinterpreted on the basis of chronological data for the western and central Alps from 1960 to 1992. Metamorphic rocks of the Lepontine, Gran San Bernardo, Piemonte, Internal Crystalline Massifs and Sesia-Lanzo mostly date Alpine metamorphic events, but some (along with granitoids and gneisses from the Helvetic and Southern Alps) result from the Variscan, Caledonian or older events and thus predate the Alpine events. Radiometric age data from the Lepontine area show systematic age relations: U-Pb monazite (23-29 Ma), Rb-Sr muscovite (15–40 Ma) and biotite (15–30 Ma), K-Ar biotite (10-30 Ma), muscovite (15–25 Ma) and hornblende (25-35 Ma), and FT zircon (10-20 Ma) and apatite (5-15 Ma), which can be explained by the different closure temperatures of the isotopic systems. A 121 Ma U-Pb zircon age for a coesite-bearing whiteschist (metaquartzite) from the Dora-Maira represents the peak of ultra-high pressure metamorphism. Coesite-free eclogites and blueschists related to ultra-high pressure rocks in the Penninic crystalline massifs yield an ⁴⁰Ar-³⁹Ar plateau age of about 100 Ma for phengites, interpreted as the cooling age. From about 50 Ma, eclogites and glaucophane schists have also been reported from the Piemonte ophiolites and calcschists, suggesting the existence of a second high P/T metamorphic event. Alpine rocks therefore record three major metamorphic events: (i) ultra-high and related high P/T metamorphism in the early Cretaceous, which is well preserved in continental material such as the Sesia-Lanzo and the Penninic Internal Crystalline Massifs; (ii) a second high P/T metamorphic event in the Eocene, which is recognized in the ophiolites and calcschists of the Mesozoic Tethys; and (iii) medium P/T metamorphism, in which both types of high P/T metamorphic rocks were variably reset by Oligocene thermal events. Due to the mixture of minerals formed in the three metamorphic events, there is a possibility that almost all geochronological data reported from the Alpine metamorphic belt show mixed ages. Early Cretaceous subduction of a Tethyan mid-ocean ridge and Eocene continental collision triggered off the exhumation of the high pressure rocks.     

White mica K-Ar ages of blueschist-facies rocks from the Piemonte 'calc-schists' of the western Italian Alps

Abstract Fifty calc-schists have been systematically collected from the Piemonte zone of the western Italian Alps and examined in terms of petrology, X-ray powder diffractometer (XRD) analysis of carbonaceous materials, and K-Ar ages of white mica separates. The petrological study and XRD analysis of carbonaceous materials have shown that calc-schists have suffered blueschist-facies metamorphism in the subduction zone of the convergent margin between the Apulian (African) continental and Tethyan oceanic plates. The metamorphic sequence is divided into three mineral zones based on increasing metamorphic temperature: chlorite (lower than 300°C), chloritoid, and rutile (higher than 450°C). The chlorite zone has dispersed ages of white mica separates, ranging from 115 to 44 Ma, whereas the rutile zone has a comparatively uniform age distribution from 60 to 40 Ma. The chloritoid zone has an intermediate age variation. The large variation in the chlorite zone is attributed to mixing of variable amounts of detrital mica derived from older high temperature metamorphic rocks in the separates, which have not been completely reset during Alpine metamorphism. The uniform age (average ca 50 Ma) in the rutile zone is the cooling age of blueschist-facies calc-schists, which have been episodically exhumed at the collision event of the European and Apulian continents in the Paleocene-Eocene.     

An experimental study of non-equilibrium vapour condensation in a shock-tube

Filmwise non-equilibrium condensation of methanol vapour is investigated on a shock-tube endwall behind a reflected shock wave. The theoretical prediction of a transition phenomenon during the growth of a liquid film is experimentally demonstrated: the film grows approximately in proportion to the time at the early stages after the reflection of the shock wave and, after a transition period, it grows in proportion to the square root of the time. The condensation parameter of the vapour is obtained from the conformity between experiment and theory. It is found that the condensation parameter of the methanol vapour is of the magnitude of one tenth of the value for the complete capture of the molecules on the liquid surface.     

FMC cameras,high resolution films and very large scale mapping

Abstract

Very large scale mapping (1/250) was experimented on the basis of FMC camera, high resolution film and total station surveying.

The future attractive combination of precision photogrammetry and personal computer assisted terrestrial surveying was investigated from the point of view of accuracy, time effectiveness and total procedures control.     

Self-affinities of landforms and folds in the Northeast Honshu Arc, Japan

A method to analyze self-affinities is introduced and applied to the large scale fold geometries of Quaternary and Tertiary sediments or geographical topographies in the inner belt of the Northeast Honshu Arc, Japan. Based on this analysis, their geometries are self-affine and can be differently scaled in different directions. We recognize a crossover from local to global altitude (vertical) variation of the geometries of folds and topographies. The characteristic length for the crossover of topographies (landforms) is about 25 km and is related to the half wavelength of the crustal buckling folds or possible maximum magnitude of inland earthquakes in the Northeast Honshu Arc. Moreover, self-affinity of the folds and topographies can be connected with the b-value in Gutenberg-Richter℉s law. We obtain two average Hurst exponents obtained from the self-affinities of folds in the Northeast Honshu Arc. This indicates that there are two possible seismic modes for the smaller and larger ranges in the focal regions in the Northeast Honshu Arc.     

Latitudinal distribution of soil CO2 efflux and temperature along the Dalton Highway,Alaska

In this paper, we investigate spatial variations in soil CO₂ efflux and carbon dynamics across five sites located between 65.5°N and 69.0°N in tundra and boreal forest biomes of Alaska. Growing and winter mean CO₂ effluxes for the period 2006–2010 were 261 ± 124 (Coefficients of Variation: 48%) and 71 ± 42 (CV: 59%) gCO₂/m², respectively. This indicates that winter CO₂ efflux contributed 24% of the annual CO₂ efflux over the period of measurement. In tundra and boreal biomes, tussock is an important source of carbon efflux to the atmosphere, and contributes 3.4 times more than other vegetation types. To ensure that representativeness of soil CO₂ efflux was determined, 36 sample points were used at each site during the growing season, so that the experimental mean fell within ±20% of the full sample mean at 80% and 90% confidence levels. We found that soil CO₂ efflux was directly proportional to the seasonal mean soil temperature, but inversely proportional to the seasonal mean soil moisture level, rather than to the elevation-corrected July air temperature. This suggests that the seasonal mean soil temperature is the dominant control on the latitudinal distribution of soil CO₂ efflux in the high-latitude ecosystems of Alaska.     

266 E+A galaxies selected from the Sloan Digital Sky Survey Data Release 2: the origin of E+A galaxies

E+A galaxies are characterized as galaxies with strong Balmer absorption lines but without any [O  ii ] or Hα emission lines. The existence of strong Balmer absorption lines indicates that E+A galaxies have experienced starburst within the past one gigayear. However, the lack of [O  ii ] and Hα emission lines indicates that E+A galaxies do not have any on-going star formation. Therefore, E+A galaxies are interpreted as post-starburst galaxies. For many years, however, it has been a mystery why E+A galaxies started starburst and why they quenched star formation abruptly. Using one of the largest samples of 266 E+A galaxies carefully selected from the Sloan Digital Sky Survey Data Release 2, we have investigated the environment of E+A galaxies from 50 kpc to 8 Mpc scale, i.e. from a typical distance to satellite galaxies to the scale of large-scale structures. We found that E+A galaxies have an excess of local galaxy density only at a scale of <100 kpc (with a 2σ significance), but not at the cluster scale (∼1.5 Mpc) nor at the scale of large-scale structure (∼8 Mpc). These results indicate that E+A galaxies are not created by the physical mechanisms associated with galaxy clusters or the large-scale structure, but are likely to be created by dynamical interaction with closely accompanying galaxies at a <100 kpc scale. The claim is also supported by the morphology of E+A galaxies. We have found that almost all E+A galaxies have a bright compact core, and that ∼30 per cent of E+A galaxies have dynamically disturbed signatures or tidal tails, which quite strongly suggest the morphological appearance of merger/interaction remnants.