The 2013 hot, dry summer in Western Europe

The European summer of 2013 was marked by hot and dry conditions in Western Europe associated with a northward shifted Atlantic storm track and a positive phase of the SNAO. Model results suggest that, relative to a 1964–93 reference period, changes in SST/SIE explain 63% (±26%) of the area-averaged warming signal over Western Europe, with the remaining 37% (±29%) explained by the direct impact of changes in anthropogenic radiative forcings from GHG and aerosols. The results further suggest that the anomalous atmospheric circulation, and associated low rainfall, were also influenced both by changes in SST/SIE and by the direct impact of changes in radiative forcings; however, the magnitude of the forced signals in these variables is much less, relative to internal variability, than for surface air temperature. Further evidence suggests that changes in North Atlantic SST were likely an important factor in explaining the striking contrast between the European summers of 2013 and that of 2012. A major area for further work is to understand more completely the mechanisms that explain these influences.

New animals, new landscapes and new worldviews: the Iron Age to Roman transition at Fishbourne

Anthropologists and cultural geographers have long accepted that animals play an important role in the creation of human cultures. However, such beliefs are yet to be embraced by archaeologists, who seldom give zooarchaeological data much consideration beyond the occasional economic or environmental reconstruction. In an attempt to highlight animal remains as a source of cultural information, this paper examines the evidence for the changing relationship between people and wild animals in Iron Age and Roman southern England. Special attention is given to ‘exotic’ species — in particular fallow deer, domestic fowl and the hare — whose management increased around AD 43. In Iron Age Britain the concept of wild game reserves was seemingly absent, but the post-Conquest appearance of new landscape features such as vivaria, leporaria and piscinae indicates a change in worldview from a situation where people seemingly negotiated with the ‘wilderness’ and ‘wild things’ to one where people felt they had the right or the responsibility to bring them to order. Using Fishbourne Roman Palace as a case study, we argue that wild and exotic animals represented far more than gastronomic treats or symbols of Roman identity, instead influencing the way in which people engaged with, traversed and experienced their surroundings.

Intercomparison of general circulation models for hot extrasolar planets

We compare five general circulation models (GCMs) which have been recently used to study hot extrasolar planet atmospheres (BOB, CAM, IGCM, MITgcm, and PEQMOD), under three test cases useful for assessing model convergence and accuracy. Such a broad, detailed intercomparison has not been performed thus far for extrasolar planets study. The models considered all solve the traditional primitive equations, but employ di↵erent numerical algorithms or grids (e.g., pseudospectral and finite volume, with the latter separately in longitude-latitude and ‘cubed-sphere’ grids). The test cases are chosen to cleanly address specific aspects of the behaviors typically reported in hot extrasolar planet simulations: 1) steady-state, 2) nonlinearly evolving baroclinic wave, and 3) response to fast timescale thermal relaxation. When initialized with a steady jet, all models maintain the steadiness, as they should—except MITgcm in cubed-sphere grid. A very good agreement is obtained for a baroclinic wave evolving from an initial instability in pseudospectral models (only). However, exact numerical convergence is still not achieved across the pseudospectral models: amplitudes and phases are observably di↵erent. When subject to a typical ‘hot-Jupiter’-like forcing, all five models show quantitatively di↵erent behavior—although qualitatively similar, time-variable, quadrupole-dominated flows are produced. Hence, as have been advocated in several past studies, specific quantitative predictions (such as the location of large vortices and hot regions) by GCMs should be viewed with caution. Overall, in the tests considered here, pseudospectral models in pressure coordinate (PEBOB and PEQMOD) perform the best and MITgcm in cubed-sphere grid performs the worst.

Baroclinic instability on hot extrasolar planets

We investigate baroclinic instability in flow conditions relevant to hot extrasolar planets. The instability is important for transporting and mixing heat, as well as for influencing large-scale variability on the planets. Both linear normal mode analysis and non-linear initial value cal- culations are carried out – focusing on the freely-evolving, adiabatic situation. Using a high- resolution general circulation model (GCM) which solves the traditional primitive equations, we show that large-scale jets similar to those observed in current GCM simulations of hot ex- trasolar giant planets are likely to be baroclinically unstable on a timescale of few to few tens of planetary rotations, generating cyclones and anticyclones that drive weather systems. The growth rate and scale of the most unstable mode obtained in the linear analysis are in qual- itative, good agreement with the full non-linear calculations. In general, unstable jets evolve differently depending on their signs (eastward or westward), due to the change in sign of the jet curvature. For jets located at or near the equator, instability is strong at the flanks – but not at the core. Crucially, the instability is either poorly or not at all captured in simulations with low resolution and/or high artificial viscosity. Hence, the instability has not been observed or emphasized in past circulation studies of hot extrasolar planets.

Methane in the atmosphere of the transiting hot Neptune GJ436b?

We present an analysis of seven primary transit observations of the hot Neptune GJ436b at 3.6, 4.5, and 8 μm obtained with the Infrared Array Camera on the Spitzer Space Telescope. After correcting for systematic effects, we fitted the light curves using the Markov Chain Monte Carlo technique. Combining these new data with the EPOXI, Hubble Space Telescope, and ground-based V, I, H, and Ks published observations, the range 0.5-10 μm can be covered. Due to the low level of activity of GJ436, the effect of starspots on the combination of transits at different epochs is negligible at the accuracy of the data set. Representative climate models were calculated by using a three-dimensional, pseudospectral general circulation model with idealized thermal forcing. Simulated transit spectra of GJ436b were generated using line-by-line radiative transfer models including the opacities of the molecular species expected to be present in such a planetary atmosphere. A new, ab-initio-calculated, line list for hot ammonia has been used for the first time. The photometric data observed at multiple wavelengths can be interpreted with methane being the dominant absorption after molecular hydrogen, possibly with minor contributions from ammonia, water, and other molecules. No clear evidence of carbon monoxide and carbon dioxide is found from transit photometry. We discuss this result in the light of a recent paper where photochemical disequilibrium is hypothesized to interpret secondary transit photometric data. We show that the emission photometric data are not incompatible with the presence of abundant methane, but further spectroscopic data are desirable to confirm this scenario.

Symbols of power: the Silchester bronze eagle and eagles in Roman Britain

Those who study Roman art and religion in Britain will know that there are a relatively small number of pieces in stone and bronze which are regularly used to illustrate arguments on Romanization, provincialism and identity. However, while these objects become familiar through such use, they are, in fact, often little studied as pieces in their own right and the only description of their appearance and context are some fifty or more years old. Re-excavation of the context from which the Silchester eagle was recovered has raised questions about the date of its deposition, as well as its origin and use, and indeed the nature of its deposition at Silchester. This paper examines the figurine in detail, the role of the eagle at Silchester and explores the significance of the eagle more widely in Roman Britain.

Season of birth and sheep husbandry in late Roman and Medieval coastal Flanders: a pilot study using tooth enamel d18O analysis

From the early Roman period, there is archaeological evidence for the exploitation of the Flemish coastal plain (Belgium) for a range of activities, such as sheep herding on the then developing salt-marshes and salt-meadows for the production of wool. During the early Middle Ages, this culminated in the establishment of dedicated ‘sheep estates’. This phase of exploitation was followed by extensive drainage and land reclamation measures in the high Medieval period, transforming areas into grassland, suited for cattle breeding. As part of a larger project investigating the onset, intensification and final decline of sheep management in coastal Flanders in the historical period, this pilot study presents the results of sequential sampling and oxygen isotope analysis of a number of sheep teeth (M2, n = 8) from four late Roman and Medieval sites (dating from 4th to 15th century AD), in order to assess potential variations in season of birth between the different sites and through time. In comparison with published data from herds of known birth season, incremental enamel data from the Flemish sites are consistent with late winter/spring births, with the possibility of some instances of slightly earlier parturition. These findings suggest that manipulation of season of birth was not a feature of the sheep husbandry-based economies of early historic Flanders, further evidencing that wool production was the main purpose of contemporary sheep rearing in the region. Manipulation of season of birth is not likely to have afforded economic advantage in wool-centred economies, unlike in some milk- or meat-based regimes.

People on the move in Roman Britain

Levels of mobility in the Roman Empire have long been assumed to be relatively high, as attested by epigraphy, demography, material culture and, most recently, isotope analysis and the skeletons themselves. Building on recent data from a range of Romano-British sites (Poundbury in Dorset, York, Winchester, Gloucester, Catterick and Scorton), this article explores the significance of the presence of migrants at these sites and the impact they may have had on their host societies. The authors explore the usefulness of diaspora theory, and in particular the concept of imperial and colonial diasporas, to illustrate the complexities of identities in later Roman Britain.