Quasi-periodic fluctuations in the Greenland–Iceland–Norwegian Seas region in a coupled climate model

We report an analysis of the mechanisms responsible for interannual variability in the Greenland–Iceland–Norwegian (GIN) Seas in a control integration of the HadCM3 coupled climate model. Interannual variability in sea surface temperature (SST) and sea surface salinity (SSS) is dominated by a quasi-periodic ∼7-year signal. Analyses show that the mechanism involves a competition between convection and advection. Advection carries cold, fresh, Arctic water over warm, salty, Atlantic water, while convection periodically mixes these two water masses vertically, raising SST. Convection is able to raise SST because of the presence of a subsurface temperature maximum. The GIN Seas convection in HadCM3 is forced by wind stress anomalies related to the North Atlantic Oscillation (NAO). The consequent SST anomalies feedback positively to force the atmosphere, resulting in a weak spectral peak (at ∼7 years) in GIN Seas sea level pressure. Although there is no evidence of a similar oscillation in reality, key aspects of the simulated mechanism may be relevant to understanding variability in the real GIN Seas. In particular, the potential for increases in convection to raise SST offers a possible new explanation for increases in SST that occurred between the 1960s and the late 1980s/early 1990s. These SST increases may have contributed to the observed sea-ice retreat. In addition, a positive feedback between GIN Seas SST and the atmosphere could contribute to the persistence of the NAO, potentially helping to explain its red spectrum or recent northeastward shift.

Chemical and isotopic characterization of hydrocarbon gas traces in porewater of very low permeability rocks: The example of the Callovo-Oxfordian argillites of the eastern part of the Paris Basin

A methodology has been developed to determine chemical and carbon isotopic compositions of trace amounts of hydrocarbon gas compounds (methane, ethane, propane, iso- and normal-butane) present as dissolved compounds in the porewater of the low permeability Callovo-Oxfordian argillites in eastern Paris Basin, France. Results indicate that the studied hydrocarbons contain significant amounts of ethane, butane and propane, in addition to methane. Carbon isotopic compositions reflect primarily thermogenic origin (thermal cracking of organic matter), and lack of any significant biodegradation. Because temperature did not exceed 50 °C in the studied argillites, investigated hydrocarbons must have originated in hotter/deeper organic-bearing formations, possibly Stephanian coals. Data supports the predominance of high maturity thermogenic gas in the upper part of the Callovo-Oxfordian, and low maturity thermogenic gas mixed with minor bacterially produced methane in the lower part of the formation. A mixing between three end-member gases models quite well the data: one thermogenic gas with a low maturity (42% methane, with a δ¹³C of − 53‰), a gas with higher maturity (55% methane, with a δ¹³C of − 47‰) and a bacterial gas (99.45% methane, with a δ¹³C of − 80‰). This study illustrates that migration of hydrocarbon gases can take place in rocks with very low permeability and porosity, such as compacted mudrocks, given enough time. It further suggests that the studied fluid migration and transfer in aquitards would help characterization and understanding of fluid movements in sedimentary basins, as a complement to studies focused on water aquifers and hydrocarbon reservoirs. Chemical and isotopic composition of dissolved hydrocarbons in porewater can be used as natural tracers of fluid circulation in sedimentary basins, in addition to more conventional tracers.     

Polarimetry and BVRI photometry of the potentially hazardous near-Earth Asteroid (23187) 2000 PN9

The results of V-band polarimetric observations of the potentially hazardous near-Earth Asteroid (23187) 2000 PN₉ at large phase angles are presented as well as its photometric observations in BVRI bands. Observations were made in March-April 2006 during its close approach to the Earth using the 1.82-m Asiago telescope (Italy) and the 0.7-m telescope at the Chuguevskaya Observational Station (Ukraine). We obtained polarimetric measurements at the phase angle of 115°, the largest phase angle ever observed in asteroid polarimetry. Our data show that the maximum value of the polarization phase curve reached 7.7% and occurred in the phase angle range of 90-115°. The measured values of linear polarization degree, BVRI colors and magnitude-phase dependence correspond to the S-type composition of this asteroid. Based on our observations the following characteristics of the Asteroid (23187) 2000 PN₉ were obtained: a rotation period of 2.5325±0.0004 h, a lightcurve amplitude of 0.13 mag, an albedo of 0.24±0.06 and a diameter of 1.6±0.3 km.     

Marine pollution control in Europe: Regional approaches, 1972–80

This article evaluates the effectiveness of four regional pollution agreements concluded during the 1970s: The Bonn Agreement, the Oslo Convention, the Paris Convention and the Helsinki Convention. The treaties are described and their implementation to 1980 outlined. The issue of EEC participation in environmental protection in Europe is analysed and problems of overlap with the treaties under discussion are pointed out. A major conclusion of the article is the need for more implementation research to properly assess the effectiveness of such regional agreements.     

Seismic vulnerability and risk assessment: case study of the historic city centre of Coimbra, Portugal

Seismic risk evaluation of built-up areas involves analysis of the level of earthquake hazard of the region, building vulnerability and exposure. Within this approach that defines seismic risk, building vulnerability assessment assumes great importance, not only because of the obvious physical consequences in the eventual occurrence of a seismic event, but also because it is the one of the few potential aspects in which engineering research can intervene. In fact, rigorous vulnerability assessment of existing buildings and the implementation of appropriate retrofitting solutions can help to reduce the levels of physical damage, loss of life and the economic impact of future seismic events. Vulnerability studies of urban centres should be developed with the aim of identifying building fragilities and reducing seismic risk. As part of the rehabilitation of the historic city centre of Coimbra, a complete identification and inspection survey of old masonry buildings has been carried out. The main purpose of this research is to discuss vulnerability assessment methodologies, particularly those of the first level, through the proposal and development of a method previously used to determine the level of vulnerability, in the assessment of physical damage and its relationship with seismic intensity. Also presented and discussed are the strategy and proposed methodology adopted for the vulnerability assessment, damage and loss scenarios for the city centre of Coimbra, Portugal, using a GIS mapping application.     

A multi-disciplinary study of the 2002–03 Etna eruption: insights into a complex plumbing system

The 2002–03 Mt Etna flank eruption began on 26 October 2002 and finished on 28 January 2003, after three months of continuous explosive activity and discontinuous lava flow output. The eruption involved the opening of eruptive fissures on the NE and S flanks of the volcano, with lava flow output and fire fountaining until 5 November. After this date, the eruption continued exclusively on the S flank, with continuous explosive activity and lava flows active between 13 November and 28 January 2003. Multi-disciplinary data collected during the eruption (petrology, analyses of ash components, gas geochemistry, field surveys, thermal mapping and structural surveys) allowed us to analyse the dynamics of the eruption. The eruption was triggered either by (i) accumulation and eventual ascent of magma from depth or (ii) depressurisation of the edifice due to spreading of the eastern flank of the volcano. The extraordinary explosivity makes the 2002–03 eruption a unique event in the last 300 years, comparable only with La Montagnola 1763 and the 2001 Lower Vents eruptions. A notable feature of the eruption was also the simultaneous effusion of lavas with different composition and emplacement features. Magma erupted from the NE fissure represented the partially degassed magma fraction normally residing within the central conduits and the shallow plumbing system. The magma that erupted from the S fissure was the relatively undegassed, volatile-rich, buoyant fraction which drained the deep feeding system, bypassing the central conduits. This is typical of most Etnean eccentric eruptions. We believe that there is a high probability that Mount Etna has entered a new eruptive phase, with magma being supplied to a deep reservoir independent from the central conduit, that could periodically produce sufficient overpressure to propagate a dyke to the surface and generate further flank eruptions.Editorial responsibility: J. Donnelly-Nolan     

Household perceptions of climate change and preferences for mitigation action: the case of the Carbon Pollution Reduction Scheme in Australia

The study aims to reveal Australian households?? perceptions of climate change and their preferences for mitigation action. A web-based survey was conducted in November 2008 in which over 600 households from the state of New South Wales were asked for their willingness to bear extra household expenditure to support the ??Carbon Pollution Reduction Scheme??, an emissions trading scheme proposed by the Australian government. The results of the study can be summarized in four key findings. First, respondents?? willingness to pay for climate change mitigation is significantly influenced by their beliefs of future temperature rise. Support for the policy increased at a decreasing rate as the perceived temperature change rose. Second, perceptions of policy failure have a significant negative impact on respondents?? support for the proposed mitigation measure. The higher the perceived likelihood that the measure would not deliver any outcome, the lower was the likelihood that respondents would support the policy. Third, respondent preferences for the proposed policy are influenced by the possibility of reaching a global agreement on emissions reduction. Sample respondents stated significantly higher values for the policy when the biggest polluting countries implement a similar scheme. Finally, respondents?? willingness to take action against climate change, both at the national and household level, is found to be influenced by their level of mass-media exposure. Particularly, those respondents who watched ??An Inconvenient Truth?? were significantly more likely to act for climate change mitigation than others.     

Archaeological Exploration in Srirangapatna and Its Environ Through Remote Sensing Analysis

This study involves exploration of archaeological structures in Srirangapatana and virtual reconstruction of Srirangapatana fort using geo-spatial techniques. Antiquity of this river island town goes back to ninth century AD which continued till British rule and hence has abundance of archaeological structures on it. Some of these structures are known and well-maintained while others are unprotected, unexcavated, hidden under thick vegetation or forgotten. To identify archaeological features such as buried/dilapidated/vegetation infested structures/features on ground, we used high resolution multispectral remote sensing data (0.5 and 5.6 m), Cartosat 1 stereo pairs (2.5 m), anaglyphs, historical documents, and analysed them on GIS platform. This study enabled us to: trace the concentric moats and fort-wall by using false colour composite image together with anaglyphs generated from Cartosat 1 stereo pair; explore hitherto unexplored and unexcavated archaeological features; identify unknown and abandoned temples/structures smothered with wild vegetation; locate exact location of currently non-existent site mentioned in historical records; identify the location of buried canal. This study also demonstrates how methodic use of various interpretation keys, image processing and analysis (such as NDVI, DEM, anaglyphs) can help in extracting archaeological features and direct archaeologists for further exploration.