Isotopic and other geochemical evidence for the origin of the Loch Uisg Granophyre,Isle of Mull,Scotland

Full chemical analyses, including some trace elements and both oxygen and strontium isotope abundance data are presented for samples collected from a traverse across the outcrop of the early Tertiary Loch Uisg Granophyre. Chemically, the body is rhyodacite with very uniform major and trace element composition. In contrast, depleted δ¹⁸O values vary widely from +1.5‰ in the south to ?3.7‰ in the north (a distance of about 21/2 km), a range comparable to that for the intrusive rocks of Mull as a whole. This indicates more extensive groundwater interaction (i.e. higher water/rock ratios and/or higher temperatures of isotope exchange) towards the focus of the central intrusive complex. There is some degree of correlation between δ¹⁸O and iron oxidation ratios but no other evidence that the primary igneous geochemistry of these rocks has been significantly modified by hydrothermal alteration after emplacement of the pluton. Initial⁸⁷Sr/⁸⁶Sr ratios range from 0.71350 ± 9 to 0.71624 ± 6 and correlate with both Rb content and Rb/Sr ratio, the latter correlation yielding a pseudo-isochron of 260 ± 54 Ma at the time of emplacement. These results confirm a major contribution from an old crustal source region, ruling out formation of the granophyre solely from a basic parent magma. However, Rb-Sr data are presented for the Moine schists exposed in Mull and Morvern which also appear to rule out their involvement in the petrogenesis of the granophyre, either as a source region for melting, or as a bulk contaminant for a mantle-derived magma. The only viable hypotheses are assimilation at depth of? Lewisian into a basaltic fractionation sequence or partial melting of a Proterozoic basement such as that involved in the production of Caledonian granites in the Scottish Highlands.     

Ground-based FTIR Measurements with High Temporal Resolution

We outline how ground-based Fourier transform infrared (FTIR) measurements of stratospheric trace species, obtained with high temporal resolution, could be used to detect filaments of polar vortex air at mid-latitudes and therefore test high spatial resolution chemical transport models (CTMs). Vertical column abundances of HCl, ClONO2, HNO3, N2O and HF have been obtained from FTIR solar absorption measurements made throughout the day from Aberdeen, UK (57°N, 2°W) on several days during winter/spring 1993/94 and 1994/95. The short-timescale ( 2 hours) variability observed in the columns is attributed to real atmospheric variations and is often associated with the passage of high latitude air over Aberdeen. This is confirmed by 3D modelling studies which qualitatively reproduce and rationalise the observed changes in the column data on January 19 1994, January 20 1995 and February 26 1995. We describe the viewing geometry of ground-based FTIR measurements and we suggest a measurement strategy which should maximise the information retrieved on horizontal gradients in stratospheric trace species columns from FTIR measurements.     

Effect of snow cover on pan-Arctic permafrost thermal regimes

This study quantitatively evaluated how insulation by snow depth (SND) affected the soil thermal regime and permafrost degradation in the pan-Arctic area, and more generally defined the characteristics of soil temperature (T_SOIL) and SND from 1901 to 2009. This was achieved through experiments performed with the land surface model CHANGE to assess sensitivity to winter precipitation as well as air temperature. Simulated T_SOIL, active layer thickness (ALT), SND, and snow density were generally comparable with in situ or satellite observations at large scales and over long periods. Northernmost regions had snow that remained relatively stable and in a thicker state during the past four decades, generating greater increases in T_SOIL. Changes in snow cover have led to changes in the thermal state of the underlying soil, which is strongly dependent on both the magnitude and the timing of changes in snowfall. Simulations of the period 2001–2009 revealed significant differences in the extent of near-surface permafrost, reflecting differences in the model’s treatment of meteorology and the soil bottom boundary. Permafrost loss was greater when SND increased in autumn rather than in winter, due to insulation of the soil resulting from early cooling. Simulations revealed that T_SOIL tended to increase over most of the pan-Arctic from 1901 to 2009, and that this increase was significant in northern regions, especially in northeastern Siberia where SND is responsible for 50 % or more of the changes in T_SOIL at a depth of 3.6 m. In the same region, ALT also increased at a rate of approximately 2.3 cm per decade. The most sensitive response of ALT to changes in SND appeared in the southern boundary regions of permafrost, in contrast to permafrost temperatures within the 60°N–80°N region, which were more sensitive to changes in snow cover. Finally, our model suggests that snow cover contributes to the warming of permafrost in northern regions and could play a more important role under conditions of future Arctic warming.     

Stability analysis of the martian obliquity during the Noachian era

We performed numerical simulations of the obliquity evolution of Mars during the Noachian era, at which time the giant planets were on drastically different orbits than today. For the preferred primordial configuration of the planets we find that there are two large zones where the martian obliquity is stable and oscillates with an amplitude lower than 20°. These zones occur at obliquities below 30° and above 60°; intermediate values show either resonant or chaotic behaviour depending on the primordial orbits of the terrestrial planets.     

From the Sun to the Earth: The 13 May 2005 Coronal Mass Ejection

We report the results of a multi-instrument, multi-technique, coordinated study of the solar eruptive event of 13 May 2005. We discuss the resultant Earth-directed (halo) coronal mass ejection (CME), and the effects on the terrestrial space environment and upper Earth atmosphere. The interplanetary CME (ICME) impacted the Earth’s magnetosphere and caused the most-intense geomagnetic storm of 2005 with a Disturbed Storm Time (Dst) index reaching ?263 nT at its peak. The terrestrial environment responded to the storm on a global scale. We have combined observations and measurements from coronal and interplanetary remote-sensing instruments, interplanetary and near-Earth in-situ measurements, remote-sensing observations and in-situ measurements of the terrestrial magnetosphere and ionosphere, along with coronal and heliospheric modelling. These analyses are used to trace the origin, development, propagation, terrestrial impact, and subsequent consequences of this event to obtain the most comprehensive view of a geo-effective solar eruption to date. This particular event is also part of a NASA-sponsored Living With a Star (LWS) study and an on-going US NSF-sponsored Solar, Heliospheric, and INterplanetary Environment (SHINE) community investigation.     

A late Holocene paleoenvironmental reconstruction from Agua Caliente,southern Belize,linked to regional climate variability and cultural change at the Maya polity of Uxbenká

We report high-resolution macroscopic charcoal, pollen and sedimentological data for Agua Caliente, a freshwater lagoon located in southern Belize, and infer a late Holocene record of human land-use/climate interactions for the nearby prehistoric Maya center of Uxbenká. Land-use activities spanning the initial clearance of forests for agriculture through the drought-linked Maya collapse and continuing into the historic recolonization of the region are all reflected in the record. Human land alteration in association with swidden agriculture is evident early in the record during the Middle Preclassic starting ca. 2600 cal yr BP. Fire slowly tapered off during the Late and Terminal Classic, consistent with the gradual political demise and depopulation of the Uxbenká polity sometime between ca. 1150 and 950 cal yr BP, during a period of multiple droughts evident in a nearby speleothem record. Fire activity was at its lowest during the Maya Postclassic ca. 950–430 cal yr BP, but rose consistent with increasing recolonization of the region between ca. 430 cal yr BP and present. These data suggest that this environmental record provides both a proxy for 2800 years of cultural change, including colonization, growth, decline, and reorganization of regional populations, and an independent confirmation of recent paleoclimate reconstructions from the same region.     

A classification of the available astrophysical data of particular Hii regions — IX NGC 2264

A classification of the observational data on NGC 2264 is presented. Optical, infrared and radio data for the Hii region are tabulated, and maps of the molecular cloud structure are shown. The observations of the NGC 2264 star cluster are also summarized. The role of star formation in this young region is briefly assessed.     

Detection of transient signals in multipath environments

This research examines methods for detecting unknown transient waveforms that are contaminated by noise. The sensitivity of the performance levels of the energy detector and the lack of knowledge about the structure of the transient waveform motivate the examination of other moment- or spectra-based detection techniques. We examine the performance of a bispectral energy detector and show that its performance will degrade if the bispectra is smoothed and that signals with no bispectral content can be detected if the bispectra is not smoothed. Further, it is shown that the performance levels of the bispectral detector are slightly better, and slightly less sensitive, than those of the energy detector for the multipath linear frequency modulated signal. Finally, the performance levels of narrowband implementations of the energy and bispectral energy detectors are compared. It is shown that for a large enough sample, the performance levels of the bispectral detector are nearly as good as those of the optimal energy detector for the single narrowband signal case. However, when the received waveform contains multiple narrowband components, the narrowband bispectral detector performs slightly better than the energy detector