RCP2.6: exploring the possibility to keep global mean temperature increase below 2��C     

Detlef P. van Vuuren  Elke Stehfest  Michel G. J. den Elzen  Tom Kram  Jasper van Vliet  Sebastiaan Deetman  Morna Isaac  Kees Klein Goldewijk  Andries Hof  Angelica Mendoza Beltran  Rineke Oostenrijk  Bas van Ruijven 《Climatic change》2011,109(1-2):95-116

The RCP2.6 emission and concentration pathway is representative of the literature on mitigation scenarios aiming to limit the increase of global mean temperature to 2°C. These scenarios form the low end of the scenario literature in terms of emissions and radiative forcing. They often show negative emissions from energy use in the second half of the 21st century. The RCP2.6 scenario is shown to be technically feasible in the IMAGE integrated assessment modeling framework from a medium emission baseline scenario, assuming full participation of all countries. Cumulative emissions of greenhouse gases from 2010 to 2100 need to be reduced by 70% compared to a baseline scenario, requiring substantial changes in energy use and emissions of non-CO₂ gases. These measures (specifically the use of bio-energy and reforestation measures) also have clear consequences for global land use. Based on the RCP2.6 scenario, recommendations for further research on low emission scenarios have been formulated. These include the response of the climate system to a radiative forcing peak, the ability of society to achieve the required emission reduction rates given political and social inertia and the possibilities to further reduce emissions of non-CO₂ gases.  相似文献   

Size-dependent uptake of nitrate and ammonium as a function of light in well-mixed temperate coastal waters     

Jean-François Maguer  Stéphane L'HelguenJulien Caradec  Cécile Klein 《Continental Shelf Research》2011,31(15):1620-1631

The effect of light on nitrate (NO₃⁻) and ammonium (NH₄⁺) uptake by natural communities was investigated in relation to cell size (<10 and >10 μm) in the well-mixed coastal waters of the English Channel. Nitrogen (N) uptake kinetics as a function of irradiance were assessed using ¹⁵N tracer techniques, for a seasonal cycle of populations collected at 50% and 1% light penetration depth. The nitrogen uptake responses to irradiance can be represented by the formulation used to describe the photosynthesis versus irradiance relationships and modified by the addition of a dark uptake parameter. The response curves of two size fractions of phytoplankton collected at 50% and 1% of incident light did not differ significantly, which suggested that the physiological characteristics of N uptake were not affected by the light intensity at which the phytoplankton assemblages were sampled. The kinetics parameters indicated that the NO₃⁻ uptake system was more strongly dependent on light than the NH₄⁺ uptake system. They also showed that N uptake was less limited by the light intensity in the small size fraction than it was in the large size fraction. At the mean light intensity in the water column, kinetics analysis predicted a NH₄⁺ uptake that was on average 1.8 (±0.6) and 2.4 (±1.0) times greater than the NO₃⁻ uptake, for <10 and >10 μm size fractions, respectively. The kinetics also predicted, at the in situ mean light intensity, that the mean ability to take up nitrogen was twice as high (1.8±0.5) for the small than for the large cells when the N substrate was NH₄⁺ and more than twice as high (2.6±1.5) when the substrate was NO₃⁻. These results added to our understanding of the light effect on N uptake processes in well-mixed waters, and can largely explain the phytoplankton production, mainly regenerated and dominated by small cells, that has been observed in these waters.  相似文献   

The electrical conductivity of weight diluted and concentrated standard seawater as a function of salinity and temperature     

Dauphinee  T. Ancsin  J. Klein  H. Phillips  M. 《Oceanic Engineering, IEEE Journal of》1980,5(1):28-41

The ratiosR_{s,t,o}of electrical conductivity of seawater samples of precisely known salinity to standard seawater at the same temperature have been measured over a wide range of salinities from 0 to42permilS and over the full range of oceanic temperatures from -2 to35degC. The samples withS<35permilwere prepared by accurate weight dilution of standard seawater with distilled water. High salinity samples were prepared by fast evaporation of standard seawater and subsequent weight dilution into the already determined <35permilrange. An equation was derived which expresses the S versusR_{s,t,o}relationship very precisely from1-42permiland at all temperatures, i.e.,S = f_{1}(R_{s,t,o}) + f_{2}(R_{s, t,o},t) =Sigma_{n=0}^{5} a_{n}R^{n/2}+ frac{Delta t}{1+kDelta t} Sigma_{n=0}^{5} b_{n}R^{n/2}whereDelta t = t-15degC,R = R_{s, t.o}; only the first termf_{1}is required at15degC. The effeet of temperature on the electrical conductivity of standard seawater was also measured. The ratior_{t}of the conductivity at temperaturetto the conductivity at15degC (C_{35,t, o}/C_{35,15,o}) is very aeenrately expressed by a fourth degree equation int. i.e,r_{t}=Sigma_{n=0}^{4} c_{n}t^{n}These two equations are sufficient for all salinity determinations at normal atmospheric pressure.  相似文献   

Association between gradual hard X-Ray emission and metric continua during large flares     

L. Klein  K. Anderson  M. Pick  G. Trottet  N. Vilmer  S. Kane 《Solar physics》1983,84(1-2):295-310

X-ray radiation is used to study coronal phenomena in conjunction with meter wave observations during some large solar flares. It is found that metric flare continua and moving type IV bursts are associated with gradual and long lasting (a few tens of minutes) microwave and hard X-ray emissions. The detailed temporal analysis reveals that although metric and hard X-ray sources are located at very different heights, both kinds of emission result from a common and continuous/repetitive injection of electrons in the corona. The late part of the metric event (stationary type IV burst) is only associated with soft X-ray radiation. This indicates that the mean energy of the radiating electrons is lower during stationary type IV bursts than during the earlier parts of the event.  相似文献   

The cored distribution of dark matter in spiral galaxies     

G. Gentile  P. Salucci  U. Klein  D. Vergani  P. Kalberla 《Monthly notices of the Royal Astronomical Society》2004,351(3):903-922

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The Purpose and Age of Underwater Walls in the Bay of Elaia of Western Turkey: A Multidisciplinary Approach     

Martin Seeliger  Dominik Brill  Stefan Feuser  Melanie Bartz  Ercan Erkul  Daniel Kelterbaum  Andreas Vtt  Christina Klein  Felix Pirson  Helmut Brückner 《Geoarchaeology》2014,29(2):138-155

Pergamum (modern: Bergama) was operating an important harbour used by military forces and merchants at the city of Elaia during Hellenistic and Roman Imperial times. Harbour‐related facilities such as warehouses, breakwaters and wharfs document the importance of this harbour site not only for the Pergamenians. This paper focuses on the purpose and age of six submerged wall structures situated approximately 1 km south of the ancient closed harbour basin of Elaia. Geoelectric cross‐sections and semi‐aquatic coring near these walls failed to detect any solid basement under the walls which excludes their possible use as breakwaters or wharfs. Instead, the walls were most likely delineating and separating evaporation ponds of salt works, which compares well with similar structures from other periods and places around the Mediterranean. Combined OSL and ¹⁴C‐dating determined the construction age of the installation between the 4th and 6th centuries A.D. Subsequent (re‐)uses are likely and are in agreement with findings from archaeological surveys.  相似文献   

Solar flares at submillimeter wavelengths     

S?m?KruckerEmail author  C.?G.?Giménez de Castro  H.?S.?Hudson  G.?Trottet  T.?S.?Bastian  A.?S.?Hales  J.?Ka?parová  K.-L.?Klein  M.?Kretzschmar  T.?Lüthi  A.?Mackinnon  S.?Pohjolainen  S.?M.?White 《Astronomy and Astrophysics Review》2013,21(1):58

We discuss the implications of the first systematic observations of solar flares at submillimeter wavelengths, defined here as observing wavelengths shorter than 3 mm (frequencies higher than 0.1 THz). The events observed thus far show that this wave band requires a new understanding of high-energy processes in solar flares. Several events, including observations from two different observatories, show during the impulsive phase of the flare a spectral component with a positive (increasing) slope at the highest observable frequencies (up to 405 GHz). To emphasize the increasing spectra and the possibility that these events could be even more prominent in the THz range, we term this spectral feature a “THz component”. Here we review the data and methods, and critically assess the observational evidence for such distinct component(s). This evidence is convincing. We also review the several proposed explanations for these feature(s), which have been reported in three distinct flare phases. These data contain important clues to flare development and particle acceleration as a whole, but many of the theoretical issues remain open. We generally have lacked systematic observations in the millimeter-wave to far-infrared range that are needed to complete our picture of these events, and encourage observations with new facilities.  相似文献   

Interchange Slip-Running Reconnection and Sweeping SEP Beams     

S. Masson  G. Aulanier  E. Pariat  K.-L. Klein 《Solar physics》2012,276(1-2):199-217

We present a new model to explain how particles (solar energetic particles; SEPs), accelerated at a reconnection site that is not magnetically connected to the Earth, could eventually propagate along the well-connected open flux tube. Our model is based on the results of a low-β resistive magnetohydrodynamics simulation of a three-dimensional line-tied and initially current-free bipole, which is embedded in a non-uniform open potential field. The topology of this configuration is that of an asymmetric coronal null point, with a closed fan surface and an open outer spine. When driven by slow photospheric shearing motions, field lines, initially fully anchored below the fan dome, reconnect at the null point, and jump to the open magnetic domain. This is the standard interchange mode as sketched and calculated in 2D. The key result in 3D is that reconnected open field lines located in the vicinity of the outer spine keep reconnecting continuously, across an open quasi-separatrix layer, as previously identified for non-open-null-point reconnection. The apparent slipping motion of these field lines leads to formation of an extended narrow magnetic flux tube at high altitude. Because of the slip-running reconnection, we conjecture that if energetic particles would be traveling through, or be accelerated inside, the diffusion region, they would be successively injected along continuously reconnecting field lines that are connected farther and farther from the spine. At the scale of the full Sun, owing to the super-radial expansion of field lines below 3?R _⊙, such energetic particles could easily be injected in field lines slipping over significant distances, and could eventually reach the distant flux tube that is well-connected to the Earth.  相似文献   

Microstructure characteristics during hydrate formation and dissociation revealed by X-ray tomographic microscopy     

Stephan A. Klapp  Frieder Enzmann  Peter Walz  Thomas Huthwelker  Jürgen Tuckermann  J.-Oliver Schwarz  Thomas Pape  Edward T. Peltzer  Rajmund Mokso  David Wangner  Federica Marone  Michael Kersten  Gerhard Bohrmann  Werner F. Kuhs  Marco Stampanoni  Peter G. Brewer 《Geo-Marine Letters》2012,32(5-6):555-562

Despite much progress over the past years in fundamental gas hydrate research, frontiers to the unknown are the early beginning and early decomposition of gas hydrates in their natural, submarine environment: gas bubbles meeting ocean water and forming hydrate, and gas starting to escape from the surface of a hydrate grain. In this paper we report on both of these topics, and present three-dimensional microstructure results obtained by synchrotron radiation X-ray cryo-tomographic microscopy (SRXCTM). Hydrates can precipitate when hydrate-forming molecules such as methane exceed solubility, and combine with water within the gas hydrate stability zone. Here we show hydrate formation on surfaces of bubbles from different gas mixtures and seawater, based on underwater robotic in situ experiments in the deep Monterey Canyon, offshore California. Hydrate begins to form from the surrounding water on the bubble surfaces, and subsequently grows inward into the bubble, evidenced by distinct edges. Over time, the bubbles become smaller while gas is being incorporated into newly formed hydrate. In contrast, current understanding has been that hydrate decomposition starts on the outer surface of hydrate aggregates and grains. It is shown that in an early stage of decomposition, newly found tube structures connect well-preserved gas hydrate patches to areas that are dissociating, demonstrating how dissociating areas in a hydrate grain are linked through hydrate that is still intact and will likely decompose at a later stage.