In the field with Joe: early excursions of the Freelance Geological Society

Fieldwork in the twenty-first century is the subject of health and safety legislation and paperwork, as we don our luminous jackets and protective helmets. Sometimes, the geology can feel like an afterthought. Contrast this with the Freelance Geological Society in the late 1940s and after, in the field most weekends, collecting, climbing and caving, in a post-war world with abundant quarries and mines.     

Spatiotemporal Distribution of Dissolved Heavy Metals in Gyeonggi Bay,Korea

In this study, we investigated the spatial and temporal distribution of heavy metals and nutrients in Gyeonggi Bay, Korea, to determine their present statu     

Sources of CAM3 temperature bias during northern winter from diagnostic study of the temperature bias equation

The Community Atmosphere Model version 3 (CAM3) temperature simulation bias is examined in this paper. We compare CAM3 output with European Centre for Medium-Range Weather Forecasts (ECMWF) 40 year reanalysis (ERA-40) data. We formulate a time mean temperature bias equation then evaluate each term in the equation. Our focus is on the Northern Hemisphere winter time. We group the temperature equation terms into these categories: linear advection terms, nonlinear advection terms, transient eddy terms and diabatic heating, and find that linear advection and diabatic bias are the largest. The nonlinear terms (velocity bias advection of temperature bias) are much smaller than each of the other groups of terms at all levels except near the surface. Linear advection terms have dipolar pattern in the Atlantic (negative NW of positive) which reflects the shift of the CAM3 model North Atlantic storm track (NAST) into Europe, especially in the upper troposphere; opposite sign dipolar structure occurs over Alaska (positive) and the north Pacific storm track (negative). The transient advection terms in middle latitudes are larger in the upper troposphere and generally positive along the Atlantic storm track. Along the north Pacific storm track (NPST), the transient terms are negative in the mid and lower troposphere over much of the NPST (positive in upper troposphere). The diabatic heating bias has large values in the tropics along the Intertropical Convergence Zone (ICZ) and along the midlatitude storm tracks. During this time of year the ICZ is mainly in the Southern Hemisphere, but CAM3 emphasizes an ICZ-like heating in the northern hemisphere of the Atlantic and Pacific Oceans. CAM3 tends to have a weaker ICZ, especially in the Atlantic. In midlatitudes, we find large bias in heating by precipitation and vertically averaged net radiation over the NAST, Europe, and the Middle East.     

A diffuse bubble-like radio-halo source MRC 0116+111: imprint of AGN feedback in a low-mass cluster of galaxies

We present detailed observations of MRC 0116+111, revealing a luminous, miniradio halo of ∼240-kpc diameter located at the centre of a cluster of galaxies at redshift   z = 0.131  . Our optical and multiwavelength Giant Metrewave Radio Telescope and Very Large Array radio observations reveal a highly unusual radio source: showing a pair of giant (∼100-kpc diameter) bubble-like diffuse structures, that are about three times larger than the analogous extended radio emission observed in M87 – the dominant central radio galaxy in the Virgo cluster. However, in MRC 0116+111 we do not detect any ongoing active galactic nucleus (AGN) activity, such as a compact core or active radio jets feeding the plasma bubbles. The radio emitting relativistic particles and magnetic fields were probably seeded in the past by a pair of radio jets originating in the AGN of the central cD galaxy. The extremely steep high-frequency radio spectrum of the north-western bubble, located ∼100 kpc from cluster centre, indicates radiation losses, possibly because having detached, it is rising buoyantly and moving away into the putative hot intracluster medium. The other bubble, closer to the cluster centre, shows signs of ongoing particle re-acceleration. We estimate that the radio jets which inflated these two bubbles might have also fed enough energy into the intracluster medium to create an enormous system of cavities and shock fronts, and to drive a massive outflow from the AGN, which could counter-balance and even quench a cooling flow. Therefore, this source presents an excellent opportunity to understand the energetics and the dynamical evolution of radio jet inflated plasma bubbles in the hot cluster atmosphere.     

Interacting effects of vegetation, soils and management on the sensitivity of Australian savanna rangelands to climate change

There is an increasing need to understand what makes vegetation at some locations more sensitive to climate change than others. For savanna rangelands, this requires building knowledge of how forage production in different land types will respond to climate change, and identifying how location-specific land type characteristics, climate and land management control the magnitude and direction of its responses to change. Here, a simulation analysis is used to explore how forage production in 14 land types of the north-eastern Australian rangelands responds to three climate change scenarios of +3°C, +17% rainfall; +2°C, ?7% rainfall; and +3°C, ?46% rainfall. Our results demonstrate that the controls on forage production responses are complex, with functional characteristics of land types interacting to determine the magnitude and direction of change. Forage production may increase by up to 60% or decrease by up to 90% in response to the extreme scenarios of change. The magnitude of these responses is dependent on whether forage production is water or nitrogen (N) limited, and how climate changes influence these limiting conditions. Forage production responds most to changes in temperature and moisture availability in land types that are water-limited, and shows the least amount of change when growth is restricted by N availability. The fertilisation effects of doubled atmospheric CO₂ were found to offset declines in forage production under 2°C warming and a 7% reduction in rainfall. However, rising tree densities and declining land condition are shown to reduce potential opportunities from increases in forage production and raise the sensitivity of pastures to climate-induced water stress. Knowledge of these interactions can be applied in engaging with stakeholders to identify adaptation options.     

Oxygen and hydrogen isotopes of rainfall and dripwater at DeSoto Caverns (Alabama, USA): Key to understanding past variability of moisture transport from the Gulf of Mexico

The Southeast and the US Gulf Coast in particular are notably lacking isotope data in the water cycle despite the fact that moisture transport from the Gulf of Mexico (GOM) has a considerable influence on both regional and continental rainfall patterns. This study reports time-series of oxygen and hydrogen isotopes acquired over a 3-year period (2005-2008) from GOM-derived rainfall, cave dripwater and shallow groundwaters, and offers valuable insights on the links between factors controlling regional rainfall and the ubiquitous karst hydrology.Amount-weighted mean monthly rainwater δ¹⁸O and δD values in Tuscaloosa, Alabama range from −1.5 to −8.3‰ and −1.2 to −49.5‰, respectively, and show mean seasonal amplitudes of ∼4‰ (δ¹⁸O) and ∼25‰ (δD). In comparison d-excess values display large seasonal amplitudes of 10-20‰ resulting from differences in the degree of evaporation from falling raindrops between summer and winter months, and correlate well with the coeval air temperature (r² = 0.59; p < 0.05). Deviations of the Gulf Coast Meteoric Water Line (GCMWL) slope and d-excess from the global meteoric water line (GMWL) are attributed to different rates of evaporation after condensation, and to humidity contrast between the cloud boundary layer and the surrounding atmosphere in the vapor source region, respectively. Rainfall amounts declined during the study interval from an excessive “wet” year, ascribed to six tropical storms incursions during an unusually active hurricane season in 2005, to an onset of a regional drought during 2007-2008 with monthly rainfall amounts substantially below normal values (30-year monthly means). An interannual trend of ¹⁸O and ²H enrichments is discerned from 2005 to 2008 (1.4‰ and 11.6‰, respectively) coeval with the decline in rainfall amounts.Dripwater samples from nearby DeSoto Caverns show weak δ¹⁸O and δD seasonal variations and record only 20% and 51% of the ¹⁸O and ²H enrichments, respectively, discerned in the rainwater 3-year time-trends. The seasonal and interannual amplitude attenuations in the dripwaters are attributed to a relatively thick overlying bedrock (∼30-40 m) and a relatively large, well-mixed, epikarst-storage reservoir. Residence time of water in the cave’s epikarst is estimated to be 1-3 months based on high-resolution flow-rate data.Our investigation suggests that global atmospheric circulation patterns (ENSO and Bermuda High) likely govern the interannual δ¹⁸O and δD isotope trends discerned in the water cycle compartments but much longer time-series are required to confirm our conjectures. The results of this study form a solid basis for future acquisition and interpretation of climate proxy records from regional speleothems.     

An illustrated guide to the fossil barnacles (Cirripedia) from the Crags (Plio-Pleistocene) of East Anglia

The Plio-Pleistocene Crag deposits of East Anglia include a wealth of shelly remains, including barnacles, preserved variously as complete shells, their disarticulated plates and trace fossils. Herein, we present a field guide to these distinctive fossils, with diagnoses of all known taxa recorded from the Crags of East Anglia, supported by both line drawings and photographs. The known stratigraphic and geographic distribution within the study area are tabulated. Recognised species include the sessile barnacles Armatobalanus bisulcatus (Darwin), A. dolossus (Darwin), Balanus balanus (Linné), B. crenatus Bruguière, B. inclusus Darwin, Concavus concavus (Bronn), Chirona hameri (Ascanius), Megabalanus tintinnabulum (Linné), Conopea calceola (Ellis), Co. spongicola (Brown), Acasta undulata Darwin, Coronula barbara Darwin, Megatrema anglicum (G.B. Sowerby) and Verruca stroemia (Müller) (=14 species); two pedunculate forms, Scalpellum magnum Darwin and Lepas delicatula Withers; and the boring Rogerella isp. The greatest diversity of species is found in the Coralline Crag and Red Crag formations, both yielding 11 species, although only four are common to both. Barnacles are poorly represented in other Crag deposits.     

The physics of particle acceleration by collisionless shocks

Using analytic theory, test-particle simulations, and self-consistent hybrid simulations, we show that quasi-perpendicular shocks—those which propagate nearly perpendicular to the upstream magnetic field—accelerate particles directly out of the incident thermal population to energies much higher than the upstream ram energy of the plasma. It has already been established that quasi-parallel shocks—those which propagate nearly in the same direction as the upstream magnetic field—efficiently accelerate particles directly out of the incident thermal population; however, this has not yet been established for quasi-perpendicular shocks. Our results can be understood within the framework of the diffusive shock acceleration theory. We find that the accelerated-particle spectrum obtained from a more-general self-consistent hybrid plasma simulation are quantitatively consistent with a less-sophisticated test-particle simulation. The implications of this are discussed.