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We consider a specific accumulation event that occurred in January 2002 in western Dronning Maud Land, Antarctica. Snow samples were obtained a few days after accumulation. We combine meteorological analyses and isotopic modelling to describe the isotopic composition of moisture during transport. Backward trajectories were calculated, based on European Centre for Medium-Range Weather Forecasts operational archive data so that the history of the air parcels transporting water vapour to the accumulation site could be reconstructed. This trajectory study showed that the air masses were not (super)saturated along most of the transport path, which is in contrast with assumptions in Lagrangian fractionation models and probably true for most precipitation events in Antarctica. The modelled fractionation along the trajectories was too limited to explain the measured isotopic content of the snow. It is shown that the observed isotopic composition of precipitation resulted from fractionation of initially more depleted water. This lower initial isotopic composition of water vapour might result from atmospheric mixing with more depleted air along the trajectory or from earlier condensation cycles, not captured by the trajectories. This is in accordance with isotope fields resulting from general circulation models, indicating a gradient in isotopic composition from the Equator to Antarctica.
Continuous, detailed isotope (δD and δ18O) profiles were obtained from eight snow pits dug in the vicinity of Vostok station, Antarctica, during the period 1984– 2000. In addition, snow samples taken along the 1km long accumulation-stake profile were measured to determine spatial variability in isotope composition of recent snow. the stacked δD time series spanning the last 55 years shows only weak correlation with the mean annual air temperature recorded at Vostok station. Significant oscillations of both snow accumulation and snow isotope composition with the periods 2.5, 5, 20 and, possibly, ~102 years observed at single points are interpreted in terms of drift of snow-accumulation waves of various scales on the surface of the ice sheet.
High-resolution records of isotope composition (δD) and accumulation of snow have been obtained from 10–12m deep snow pits dug in the vicinity of Vostok station during the 1979/80 and 1999/2000 Antarctic field seasons. We employ meteorological, balloon-sounding and snow-stake data to interpret the isotope record in terms of past temperature changes. Our reconstruction suggests that snow accumulation rate and the near-surface air temperature at Vostok have varied during the past 200 years between 15 and 30 kg m–2 a–1, and between –56 and –55˚C, respectively, with a slight general tendency to increase from the past to the present. Both parameters reveal a 50 year periodicity that correlates with the Pacific Decadal Oscillation index, implying a climatic teleconnection between central Antarctica and the tropical Pacific.
Cixiid planthoppers are considered of major economic importance, as they can transmit phytoplasmas responsible for many plant diseases. While thorougly studied in vineyards, the epidemiology of stolbur phytoplasma, transmitted by Hyalesthes obsoletus Signoret, was rarely investigated on minor crops as lavender, where it leads to ‘yellow decline’ disease and large economic losses. The objective of this paper is to understand the effect of the local landscape characteristics on the presence and density of H. obsoletus in the ‘Plateau de Valensole’, southern France. Potential host plants of H. obsoletus were surveyed in three contrasted zones (in terms of crops and disease intensity), by uprooting plants and capturing adults in emergence traps. The localization and potential movements of H. obsoletus from the host plants towards lavandin (infertile hybrid of lavender) were determined using yellow sticky traps. Clary sage plants were found as major hosts of H. obsoletus. Flying insects were also caught in fields of lavandin, although emergence traps and plant uprooting did not confirm this crop as a winter host, i.e., as a reservoir for the insect. Based on one zone, we showed that attractiveness may depend on crop (clary sage or lavandin) and on its age, as well as on the distance to the supposed source field. These results suggest that clary sage could be an important host of H. obsoletus, whose density largely varies between zones. Genetic studies would be required to confirm the role of clary sage in the dissemination of yellow decline of lavandin.
The seasonal deuterium excess signal of fresh snow samples from Neumayer station, coastal Dronning Maud Land, Antarctica, was studied to investigate the relationship between deuterium excess and precipitation origin. An isotope model was combined with a trajectory model to determine the relative influence of different moisture sources on the mean annual course of the deuterium excess, focusing on the phase lag between δ18O and excess d. Whereas the annual course of δ18O always shows an austral summer maximum, which clearly depends on local temperature and the annual course of moisture source-area parameters, the deuterium excess of the fresh snow samples shows maximum values already in spring. There can be many different reasons for the time lag between δ18O and deuterium excess in an ice core, including post-depositional processes and changes in the moisture source of precipitation. The use of fresh snow samples enabled us to exclude post-depositional processes and study solely the influence of precipitation origin. Changes in the moisture source connected to systematic changes in the general atmospheric circulation can have a strong influence on the phase lag between deuterium excess and δ18O, which has to be taken into account for climatic interpretation of stable-isotope profiles from ice cores.
Delmotte and Verplaetse connect the issue of trust to legitimacy: what are the ethical boundaries that citizens can entrust the legislator not to transgress? Moreover, a research-programme aiming to restore the relationship between taxpayers and their governments demands an identification of the limits to governmental taxing proclivities. Indeed, while normative tax theory focuses mainly on how to limit the productivity-loss due to taxation, this contribution scrutinises how to limit rightsviolations due to taxation.
To demonstrate the effect of peoples ‘ rights within fiscal processes, the authors raise the issue of endowment taxation. The concept of an endowment tax, being a levy on the market value of one ‘ s talent, is the showpiece of the dominant, welfare economist approach to taxation. Taxing people on their talents has been celebrated as a theoretic ideal – mainly since it avoids taxpayers ‘ minimising their tax debt by working less, and it thus maximises welfare.
However, both authors protest against the ideal of talent taxation, by showing how such a measure collides with the rights taxpayers have over their own person. From a more abstract notion of autonomy, they deduce the ‘ right to self-usership ‘, that claims that all people have at least the right to control their own body and mind. By analysing how a talent tax would be practically implemented, the authors reveal that such a policy violates this right not once – but thrice: measuring, valorising and effectively taxing talents, all interfere with a different aspect of our general right to self-usership – and signal the illegitimacy of this fiscal measure.
As the right to self-usership demands that taxation ought to stay away from the sphere constructed by our body and mind, both authors explain why an income tax can possibly respect this demand. Since income does not belong to the personal domain itself, but is rather a product of consensual economic interactions, governments are not a priori prohibited from imposing fiscal and other duties on one's realised income, as long as these are detached from the choices people make on how to use their bodies and minds.
The total air content (V) of ice has been measured along the Dome Summit South (DSS) core from Law Dome, East Antarctica. The main features of this record are the very well-preserved sub-annual fluctuations of V (down to at least 900 m depth) and the significant increase of the V values during the last deglaciation. The sub-annual variations reflect changes in close-off porosity, and we interpret the V seasonal peaks as tracers of depth-hoar layers. For the longer time-scale, the large V fluctuations observed are interpreted in terms of elevation and/or close-off porosity changes under different assumptions. We analyze the possible influence of a different global pressure field and/or a change in seasonal temperature and precipitation cycles during the last glacial period. Our estimates of surface elevation changes derived from the V data are then compared with independent reconstructions of past elevations.
Documenting past changes in the East Antarctic surface mass balance is important to improve ice core chronologies and to constrain the ice-sheet contribution to global mean sea-level change. Here we reconstruct past changes in the ratio of surface mass balance (SMB ratio) between the EPICA Dome C (EDC) and Dome Fuji (DF) East Antarctica ice core sites, based on a precise volcanic synchronization of the two ice cores and on corrections for the vertical thinning of layers. During the past 216 000 a, this SMB ratio, denoted SMBEDC/SMBDF, varied between 0.7 and 1.1, being small during cold periods and large during warm periods. Our results therefore reveal larger amplitudes of changes in SMB at EDC compared with DF, consistent with previous results showing larger amplitudes of changes in water stable isotopes and estimated surface temperature at EDC compared with DF. Within the last glacial inception (Marine Isotope Stages, MIS-5c and MIS-5d), the SMB ratio deviates by up to 0.2 from what is expected based on differences in water stable isotope records. Moreover, the SMB ratio is constant throughout the late parts of the current and last interglacial periods, despite contrasting isotopic trends.
At the meeting of the Commission in 1932 under the Presidency of Prof. E. W. Brown, it was resolved that the “Named Lunar Formations” presented in manuscript by Miss Blagg and Dr Müller should be printed and published. It is anticipated that the volume will be distributed before the meeting of the I.A.U. in Paris.
The reference maps prepared by Mr Wesley and Miss Blagg were not recommended for immediate publication. It was thought that they might be incorporated with the series of photographic maps in preparation by the Committee of the Carnegie Institution of Washington on Study of the Surface Features of the Moon. After correspondence with Dr Wright, however, it seemed better that the maps accompanying the “Named Lunar Formations” should be published with them. The Commission again expresses its great indebtedness to Miss Blagg and Dr Müller for their arduous and painstaking labour.
The President reported that the work of the Commission had been achieved and two volumes published and distributed. These are: (1) a volume of named lunar formations and (2) a volume of 14 maps with corresponding names upon them.
After some discussion it was proposed to recommend that the Commission should be continued on a broader basis and called “La Lune”—but divided into three sub-commissions.
(1)Visual and Photographic Observations of the Surface.
We present an update of the ‘key points’ from the Antarctic Climate Change and the Environment (ACCE) report that was published by the Scientific Committee on Antarctic Research (SCAR) in 2009. We summarise subsequent advances in knowledge concerning how the climates of the Antarctic and Southern Ocean have changed in the past, how they might change in the future, and examine the associated impacts on the marine and terrestrial biota. We also incorporate relevant material presented by SCAR to the Antarctic Treaty Consultative Meetings, and make use of emerging results that will form part of the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report.
Where does the strange attraction to the polar regions lie, so powerful, so gripping that on one's return from them one forgets all the weariness of body and soul and dreams only of going back? Where does the incredible charm of these unattended and terrific regions lie?
Jean-Baptiste Charcot, 1908
For many people the word Antarctica is synonymous with cold and with more ice than can be imagined. The Antarctic continent has been continuously covered by a thick layer of ice for the past 15 million years, leaving less than 0.5% of the underlying rock visible. This enormous mass of ice, formed by the progressive accumulation of snowfall, slowly flows back to the ocean. Antarctica is a major actor in our global climate system as well as being a most precious archive of the history of climate evolution over the last 1 million years.
Antarctic ice in the global water cycle
For many millions of years, Antarctica has been the largest reservoir of continental ice on earth. The dimensions of this ‘sleeping giant’ are astonishing. The area permanently covered by continental snow and ice is greater than 13 million km², 30% more than all of Europe. Around Antarctica, the cold Austral Ocean enhances the ice area every winter as the frozen surface waters form sea ice. These ice surfaces reflect sunshine back into space rather than absorbing it, helping to maintain extremely cold conditions at the high southern latitudes.
In this chapter, we describe and explain some of the patterns observed in the behaviour of Earth’s climate system. We explain some of the causes of the climate’s natural variability, setting contemporary climate change in its longer-term context. We describe the various lines of evidence about climate forcing and the feedbacks that determine the responses to perturbations, and the way in which reconstructions of past climates can be used in combination with models and contemporary observations of change.
Human activity is creating a major perturbation to the Earth, directly affecting the composition of the atmosphere, and the nature of the land surface . These direct effects are expected in turn to cause impacts on numerous aspects of the Earth: regional climates , the distribution of ice and vegetation types, and perhaps the circulation of the oceans. Numerous interactions within the Earth system must be understood to enable prediction of the effects of the imposed changes. Models used for prediction are underpinned by a physical understanding of the climate. Aspects of these models are generally tuned to the Earth we experience today, but it is their representation of Earth’s response to change that really interests us.
By observing the Earth, both directly in the present and indirectly in the past, we learn about processes and feedbacks that models need to represent; and we can test whether the real Earth has responded to perturbations with the speed and magnitude that our models display. The ultimate goal is to use such observations to test models quantitatively, and to calibrate some of their less-constrained parameters. This goal cannot be fully realized unless we have knowledge of both the perturbation and the spatial pattern and magnitude of the response. This chapter concentrates on observations of how the Earth’s climate has responded to perturbations in the past.
Microwave processed glass reinforced epoxies or glass reinforced polyesters exhibit mechanical behaviors different from conventionally cured materials, relatively to tensile tests. The faster increases of temperature due to microwaves cause a competition between the matrix flow and the crosslinking reaction which can be estimated by porosity variations. Higher mechanical moduih are also obtained, because of both an effect on chemical kinetics and a more homogenous distribution of temperature in materials. Nevertheless, to provide such specific mechanical behaviors in microwave processed composite materials, a best control of the experimental pressure parameters is requested.
In this paper, we solve an optimal control problem using the
calculus of variation. The system under consideration is a
switched autonomous delay system that undergoes jumps at the
switching times. The control variables are the instants when the
switches occur, and a set of scalars which determine the jump
amplitudes. Optimality conditions involving analytic expressions
for the partial derivatives of a given cost function with respect
to the control variables are derived using the calculus of
variation. A locally optimal impulsive control strategy can then
be found using a numerical gradient descent algorithm.
The fluorine route is thoroughly investigated for the hydrothermal synthesis of montmorillonite in the Na2O-MgO-Al2O3-SiO2-H2O system. Using the optimal conditions suggested by Reinholdt et al. (2001) for the crystallization of pure montmorillonites with the formula Na2x(Al2(1-x)Mg2x☐)Si4O10(OH)2, several parameters (x, Mg content, duration of crystallization, F/Si atomic ratio, pH, nature of counterbalance cation) are varied independently from their ideal values. The products are analysed by various techniques (X-ray diffraction, thermogravimetric analysis-differential thermal analysis, 29Si, 27Al and 19F magic angle spinning-nuclear magnetic resonance). It appears that a pure montmorillonite can only be obtained within a narrow x range (0.10 ≤ x ≤ 0.20). The presence of F in the starting hydrogel and the crystallization time also have significant effects on the purity of the final products. It is shown that a small amount of fluorine is needed for the crystallization of pure montmorillonite phyllosilicates.