Northern North American Tree-Ring Evidence for Regional Temperature Changes after Major Volcanic Events

Maximum latewood density data from trees at thirteen temperature-sensitive sites along the northern treeline of North America are used to evaluate the spatial patterns of response to four known volcanic events just prior to the period of modern observations: in 1640, 1783, 1815 and 1835. A previously unknown event is also postulated for 1699. This tree-ring density parameter is used because it shows a stronger and more consistent short-term, temperature-related volcanic signal than ring width. Normalized density departures following these events vary in sign and magnitude from region to region, with the coldest summer conditions inferred for the Northwest Territories in 1641, Alaska in 1783, Quebec and Labrador in 1816 and the Northwest Territories in 1836. For these as well as other events, low density values are often among the most extreme on record at their respective locations. We suggest that these regional variations in tree growth reflect cooling induced by volcanism and the distribution of cooling influenced by atmospheric circulation patterns.     

Using Diurnal Temperature Signals to Infer Vertical Groundwater‐Surface Water Exchange

Heat is a powerful tracer to quantify fluid exchange between surface water and groundwater. Temperature time series can be used to estimate pore water fluid flux, and techniques can be employed to extend these estimates to produce detailed plan‐view flux maps. Key advantages of heat tracing include cost‐effective sensors and ease of data collection and interpretation, without the need for expensive and time‐consuming laboratory analyses or induced tracers. While the collection of temperature data in saturated sediments is relatively straightforward, several factors influence the reliability of flux estimates that are based on time series analysis (diurnal signals) of recorded temperatures. Sensor resolution and deployment are particularly important in obtaining robust flux estimates in upwelling conditions. Also, processing temperature time series data involves a sequence of complex steps, including filtering temperature signals, selection of appropriate thermal parameters, and selection of the optimal analytical solution for modeling. This review provides a synthesis of heat tracing using diurnal temperature oscillations, including details on optimal sensor selection and deployment, data processing, model parameterization, and an overview of computing tools available. Recent advances in diurnal temperature methods also provide the opportunity to determine local saturated thermal diffusivity, which can improve the accuracy of fluid flux modeling and sensor spacing, which is related to streambed scour and deposition. These parameters can also be used to determine the reliability of flux estimates from the use of heat as a tracer.     

The glacial and interstadial sediments at the Burn of Benholm,Kincardineshire: evidence for onshore pre‐Devensian ice movement in northeast Scotland

Pebbly clays and diamictons containing marine shell fragments and peat lenses exposed beneath subglacially deposited Late Devensian till at the Burn of Benholm provide new insights into the glacial history of Quaternary sequences in eastern Scotland. The peat yielded pollen of interstadial affinity (including Bruckenthalia spiculifolia) and non‐finite radiocarbon dates. Comparisons with other pre‐Late Devensian pollen records in northern Scotland suggest that the peat lenses are remnants of an Early Devensian interstadial deposit, of Oxygen Isotope Substage 5c or 5a age. Reworked faunal assemblages in the shelly sediments include Quaternary marine molluscs of low boreal aspect, as well as Mesozoic and Palaeozoic microfossils. Amino acid ratios from fragments of Arctica islandica suggest that the shells are of Oxygen Isotope Stage 9 age or older. The fabric and composition of the shelly sediments are consistent with their emplacement as deformation till during the onshore movement of glacially transported rafts of marine sediment. Folded and sheared contacts between the shelly deposits, peat lenses and the overlying Late Devensian till indicate that the fossiliferous sediments were glacitectonised during the main Late Devensian glaciation, when ice moved from Strathmore and overrode the site from the southwest. British Geological Survey. © NERC 2000.     

The Doppler Imaging System: Initial observations of the auroral thermosphere

During December 1982, a novel Fabry-Perot interferometer—a Doppler Imaging System (DIS)— was used at Kiruna Geophysical Institute (KGI), Sweden (67.8°N, 21.2°E) to complement a series of coordinated observations of global thermospheric dynamics utilizing a number of conventional ground-based Fabry-Perot interferometers and the NASA Dynamics Explorer satellite. The DIS is an interferometer with two unique attributes : it has a luminosity or étendue more than one hundred times that of the conventional Fabry-Perot interferometer, and it is also capable of deducing a two-dimensional velocity field of a suitable line-emitting areal source by independently measuring the Doppler shift at a large number of points within the field of view. On 17 December 1982, a very large geomagnetic Storm Sudden Commencement (08.05 U.T.) preceded a major geomagnetic disturbance. During this disturbance, Northern Scandinavia was influenced by a strong eastward auroral electrojet for an extended period (10–19 U.T.). The DIS was able to observe the dynamical response of the upper thermosphere to this event in conjunction with a second Fabry-Perot interferometer (FPI) at KGI. Westward thermospheric winds of about 900 m s^?1 occurred during the disturbance and, at the peak of the disturbance, the combined DIS and FPI observations indicate that the thermospheric flow was quite chaotic. Fluctuations of the order of ± 150 ms^?1, associated with spatial scales of the order of 100 or 200 km occurred within the mean westward flow inside the 800 km diameter region observed from Kiruna.     

Correction of Discretization Errors Simulated at Supply Wells

Many hydrogeology problems require predictions of hydraulic heads in a supply well. In most cases, the regional hydraulic response to groundwater withdrawal is best approximated using a numerical model; however, simulated hydraulic heads at supply wells are subject to errors associated with model discretization and well loss. An approach for correcting the simulated head at a pumping node is described here. The approach corrects for errors associated with model discretization and can incorporate the user's knowledge of well loss. The approach is model independent, can be applied to finite difference or finite element models, and allows the numerical model to remain somewhat coarsely discretized and therefore numerically efficient. Because the correction is implemented external to the numerical model, one important benefit of this approach is that a response matrix, reduced model approach can be supported even when nonlinear well loss is considered.     

A Snapshot of the Sun Near Solar Minimum: The Whole Heliosphere Interval

We present an overview of the data and models collected for the Whole Heliosphere Interval, an international campaign to study the three-dimensional solar?Cheliospheric?Cplanetary connected system near solar minimum. The data and models correspond to solar Carrington Rotation 2068 (20 March??C?16 April 2008) extending from below the solar photosphere, through interplanetary space, and down to Earth??s mesosphere. Nearly 200 people participated in aspects of WHI studies, analyzing and interpreting data from nearly 100 instruments and models in order to elucidate the physics of fundamental heliophysical processes. The solar and inner heliospheric data showed structure consistent with the declining phase of the solar cycle. A closely spaced cluster of low-latitude active regions was responsible for an increased level of magnetic activity, while a highly warped current sheet dominated heliospheric structure. The geospace data revealed an unusually high level of activity, driven primarily by the periodic impingement of high-speed streams. The WHI studies traced the solar activity and structure into the heliosphere and geospace, and provided new insight into the nature of the interconnected heliophysical system near solar minimum.     

A platyctenean ctenophore from New Zealand

Two colour variants of Coeloplana willeyi Abbott are described from northern New Zealand. This is the first record of a representative of the order Platyctenea in New Zealand.     

A Queer Country? A case study of the politics of gay/lesbian belonging in an Australian country town

The present paper examines the complex politics of gay/lesbian belonging through a case study of Daylesford, Victoria, an Australian country town. It contributes to two research bodies: gay/lesbian rural geographies and the politics of belonging. Daylesford hosts ChillOut, Australia's largest rural gay/lesbian festival, which provides a telling context for investigating gay/lesbian belonging in rural Australia. We use qualitative data from the 2006 ChillOut Festival, including interviews with local residents, newspaper commentaries, and visitors’ surveys, to explore how Daylesford has been constructed, imagined, and experienced as a ‘unique’ site of gay/lesbian belonging in rural Australia. We find that ChillOut crucially contributes to its wider reputation as a gay-friendly country town, but also, we argue, to the contested nature of gay/lesbian belonging. This was most powerfully demonstrated by the local council's refusal to fly the gay-identified rainbow flag on the Town Hall during the 2006 Festival and its subsequent banning of the display of all festival flags from that key public building. Because ChillOut was the catalyst for this protocol, the resolution was viewed as homophobic. Indeed, the homophobic and heterosexist rhetoric that ensued in the Letters to the Editor section of the local newspaper revealed some residents’ underlying antagonism towards ChillOut and the local gay/lesbian community. Moreover, appealing to a shared ‘Australian identity’ and associated normative ‘family values’, these letter writers deployed a multi-scalar politics of belonging, where a sense of gay/lesbian belonging to Daylesford at the local scale was contested by the assertion of a ‘more meaningful’ national scale of allegiance fashioned by heteronormativity.     

Cristobalite in a rhyolitic lava dome: evolution of ash hazard

Prolonged and heavy exposure to particles of respirable, crystalline silica-rich volcanic ash could potentially cause chronic, fibrotic disease, such as silicosis, in individuals living in areas of frequent ash fall. Here, we show that the rhyolitic ash erupted from Chaitén volcano, Chile, in its dome-forming phase, contains increased levels of the silica polymorph cristobalite, compared to its initial plinian eruption. Ash erupted during the initial, explosive phase (2–5 May 2008) contained approximately 2 wt.% cristobalite, whereas ash generated after dome growth began (from 21 May 2008) contains 13–19 wt.%. The work suggests that active obsidian domes crystallise substantial quantities of cristobalite on time-scales of days to months, probably through vapour-phase crystallisation on the walls of degassing pathways, rather than through spherulitic growth in glassy obsidian. The ash is fine-grained (9.7–17.7 vol.% <4 μm in diameter, the respirable range) and the particles are mostly angular. Sparse, fibre-like particles were confirmed to be feldspar or glass.     

High Purge Volume Sampling—A New Paradigm for Subslab Soil Gas Monitoring

Subslab soil gas sampling and analysis is a common line of evidence for assessing human health risks associated with subsurface vapor intrusion to indoor air for volatile organic compounds; however, conventional subslab sampling methods have generated data that show substantial spatial and temporal variability, which often makes the interpretation difficult. A new method of monitoring has been developed and tested that is based on a concept of integrating samples over a large volume of soil gas extracted from beneath the floor slab of a building to provide a spatially averaged subslab concentration. Regular field screening is also conducted to assess the trend of concentration as a function of the volume removed to provide insight into the spatial distribution of vapors at progressive distances away from the point of extraction. This approach minimizes the risk of failing to identify the areas of elevated soil vapor concentrations that may exist between discrete sample locations, and can provide information covering large buildings with fewer holes drilled through the floor. The new method also involves monitoring the extraction flow rate and transient vacuum response for mathematical analysis to help interpret the vapor concentration data and to support an optimal design for any subslab venting system that may be needed.