Ecosystem history of Mississippi River-influenced continental shelf revealed through preserved phytoplankton pigments     

Rabalais NN  Atilla N  Normandeau C  Turner RE 《Marine pollution bulletin》2004,49(7-8):537-547

Pigments determined by high performance liquid chromatography (HPLC) provide useful information concerning water column and epibenthic plant and microbial communities in both extant communities and accumulated sediments in lakes, estuaries and the ocean. Chlorophyll and its degradation products provide an estimate of overall biomass, and carotenoid pigments provide taxonomic biomarkers of phytoplankton. We examined the pigments preserved in sediment cores from the Louisiana continental shelf adjacent to the outflow of the Mississippi River system to document changes in phytoplankton community composition, phytoplankton abundance, and conditions of hypoxia over time. Carbon accumulated in sediments from water depths of 20-60 m is primarily derived from marine phytoplankton and represents the history of phytoplankton communities in the overlying water. There is a general increase in chlorophyll a, pheopigments, zeaxanthin, fucoxanthin and most carotenoids over time, with the change gradual from 1955 to 1970, followed by a fairly steady increase to 1997. The highest chloropigment concentrations are in cores from areas more likely to be exposed to seasonal hypoxia. These indicate an increase in eutrophication in the form of greater diatom and cyanobacterial production, or a worsening of hypoxia, or both. This trend expanded westward along the Louisiana shelf in the 1990s.  相似文献   

European floods during the winter 1783/1784: scenarios of an extreme event during the ‘Little Ice Age’   总被引：1，自引：0，他引：1  

Rudolf Brázdil  Gaston R. Demarée  Mathias Deutsch  Emmanuel Garnier  Andrea Kiss  Jürg Luterbacher  Neil Macdonald  Christian Rohr  Petr Dobrovolný  Petr Kolář  Kateřina Chromá 《Theoretical and Applied Climatology》2010,100(1-2):163-189

The Lakagígar eruption in Iceland during 1783 was followed by the severe winter of 1783/1784, which was characterised by low temperatures, frozen soils, ice-bound watercourses and high rates of snow accumulation across much of Europe. Sudden warming coupled with rainfall led to rapid snowmelt, resulting in a series of flooding phases across much of Europe. The first phase of flooding occurred in late December 1783–early January 1784 in England, France, the Low Countries and historical Hungary. The second phase at the turn of February–March 1784 was of greater extent, generated by the melting of an unusually large accumulation of snow and river ice, affecting catchments across France and Central Europe (where it is still considered as one of the most disastrous known floods), throughout the Danube catchment and in southeast Central Europe. The third and final phase of flooding occurred mainly in historical Hungary during late March and early April 1784. The different impacts and consequences of the above floods on both local and regional scales were reflected in the economic and societal responses, material damage and human losses. The winter of 1783/1784 can be considered as typical, if severe, for the Little Ice Age period across much of Europe.  相似文献   

Does public policy support or undermine climate change adaptation? Exploring policy interplay across different scales of governance   总被引：4，自引：0，他引：4  

Kate Urwin  Andrew Jordan   《Global Environmental Change》2008,18(1):180-191

Policy makers have now recognised the need to integrate thinking about climate change into all areas of public policy making. However, the discussion of ‘climate policy integration’ has tended to focus on mitigation decisions mostly taken at international and national levels. Clearly, there is also a more locally focused adaptation dimension to climate policy integration, which has not been adequately explored by academics or policy makers. Drawing on a case study of the UK, this paper adopts both a top-down and a bottom-up perspective to explore how far different sub-elements of policies within the agriculture, nature conservation and water sectors support or undermine potential adaptive responses. The top-down approach, which assumes that policies set explicit aims and objectives that are directly translated into action on the ground, combines a content analysis of policy documents with interviews with policy makers. The bottom-up approach recognises the importance of other actors in shaping policy implementation and involves interviews with actors in organisations within the three sectors. This paper reveals that neither approach offers a complete picture of the potentially enabling or constraining effects of different policies on future adaptive planning, but together they offer new perspectives on climate policy integration. These findings inform a discussion on how to implement climate policy integration, including auditing existing policies and ‘climate proofing’ new ones so they support rather than hinder adaptive planning.  相似文献   

The Cepheid impostor HD 18391 and its anonymous parent cluster     

D.G. Turner  V.V. Kovtyukh  D.J. Majaess  D.J. Lane  K.E. Moncrieff 《Astronomische Nachrichten》2009,330(8):807-815

New and existing photometry for the G0 Ia supergiant HD 18391 is analyzed in order to confirm the nature of the variability previously detected in the star, which lies off the hot edge of the Cepheid instability strip. Small‐amplitude variability at a level of δV = 0.016 ± 0.002 is indicated, with a period of P = 123^d.04 ± 0^d.06. A weaker second signal may be present at P = 177^d.84 ± 0^d.18 with δV = 0.007 ± 0.002, likely corresponding to fundamental mode pulsation if the primary signal represents overtone pulsation (123.04/177.84 = 0.69). The star, with a spectroscopic reddening of E_B–V = 1.02 ± 0.003, is associated with heavily‐reddened B‐type stars in its immediate vicinity that appear to be outlying members of an anonymous young cluster centered ∼10′ to the west and 1661 ± 73 pc distant. The cluster has nuclear and coronal radii of r_n = 3.5′ and R_c = 14′, respectively, while the parameters for HD 18391 derived from membership in the cluster with its outlying B stars are consistent with those implied by its Cepheid‐like pulsation, provided that it follows the semi‐period‐luminosity relation expected of such objects. Its inferred luminosity as a cluster member is M_V = –7.76 ± 0.10, its age (9 ± 1) × 10⁶ years, and its evolutionary mass ∼19 M_⊙. HD 18391 is not a classical Cepheid, yet it follows the Cepheid period‐luminosity relation closely, much like another Cepheid impostor, V810 Cen (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

The study of instabilities in the solar wind and magnetosheath and their interaction with the Earth's magnetosphere     

Kate?ina Andréeová 《Planetary and Space Science》2009,57(7):888-890

The thesis concentrates on an analysis of the experimental data as well as numerical simulation of propagation of fast forward (FF) shocks in the solar wind and their evolution through the magnetosheath to the inner magnetosphere. The thesis was defended at the Charles University, Prague, Faculty of Mathematics and Physics, Department of Plasma and Surface Science (V Holesovickach 2, 180 00 Prague 8, Czech Republic) on September 30, 2008 under supervision of Doc. Lubomír P?ech. The thesis is written in English and a resume can be found at http://physics.mff.cuni.cz/kfpp/phd/andreeova.pdf.  相似文献   

Characteristics of the Galaxy according to Cepheids     

D. J. Majaess  D. G. Turner  D. J. Lane 《Monthly notices of the Royal Astronomical Society》2009,398(1):263-270

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Photometric observations of Cepheids from the ASAS-3 catalog: Photoelectric <Emphasis Type="Italic">BV I</Emphasis><Subscript>c</Subscript> observations of 33 classical Cepheids     

L. N. Berdnikov  A. Yu. Kniazev  V. V. Kravtsov  E. N. Pastukhova  D. G. Turner 《Astronomy Letters》2009,35(1):39-44

Cepheids, the principal distance indicators, point to the existence of two inner Galactic spiral arms in the immediate solar neighborhood (within 5 kpc). However, the available Cepheids are clearly insufficient for a detailed study of the structure of these arms. Fortunately, southern-sky monitoring (the ASAS project) has led to the discovery of many new variable stars, more than one thousand of which have been identified as possible Cepheids. To improve the classification and to construct reliable light curves for new Cepheids, we have begun their regular photometric observations. Here, we present the first results: 1192 photoelectricBV I _c observations were performed for 33 classical Cepheidswith the 76-cm telescope of the South-African Astronomical Observatory (SAAO, the South-African Republic) from December 2006 to January 2008. We provide tables of observations and V light and B-V and V-I _c color curves. The new observations together with ASAS-3 data have been used to improve the elements of the light variations.  相似文献   

Excursion to Walton heath and Headley with special reference to the supposed Pliocene deposits: Saturday,June 11th, 1921     

George W. Young  Ernest Arthur Turner 《Proceedings of the Geologists' Association. Geologists' Association》1921,32(4):231-235

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The river Mole: Its physiography and superficial deposits     

A.J. Bull  F. Gossling  J.F.N. Green  H.A. Hayward  E.A. Turner  S.W. Wooldridge 《Proceedings of the Geologists' Association. Geologists' Association》1934,45(1):35-IN2

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Reducing fugitive methane emissions from the North American oil and gas sector: a proposed science-policy framework     

Kate Konschnik  Sarah Marie Jordaan 《Climate Policy》2018,18(9):1133-1151

The shale gas boom in the United States spurred a shift in electricity generation from coal to natural gas. Natural gas combined cycle units emit half of the CO₂ to produce the same energy as a coal unit; therefore, the market trend is credited for a reduction in GHG emissions from the US power sector. However, methane that escapes the natural gas supply chain may undercut these relative climate benefits. In 2016, Canada, the United States and Mexico pledged to reduce methane emissions from the oil and natural gas sector 40–45% from 2012 levels by 2025. This article reviews the science-policy landscape of methane measurement and mitigation relevant for meeting this pledge, including changes in US policy following the 2016 presidential election. Considerable policy incoherence exists in all three countries. Reliable inventories remain elusive; despite government and private sector research efforts, the magnitude of methane emissions remains in dispute. Meanwhile, mitigation efforts vary significantly. A framework that integrates science and policy would enable actors to more effectively inform, leverage and pursue advances in methane measurement and mitigation. The framework is applied to North America, but could apply to other geographic contexts.

Key policy insights

• The oil and gas sector’s contribution to atmospheric methane concentrations is becoming an increasingly prominent issue in climate policy.

• Efforts to measure and control fugitive methane emissions do not presently proceed within a coherent framework that integrates science and policy.

• In 2016, the governments of Canada, Mexico and the United States pledged to reduce methane emissions from the oil and natural gas sector 40–45% from 2012 levels by 2025.

• The 2016 presidential election in the United States has halted American progress at the federal level, suggesting a heavier reliance on industry and subnational efforts in that country.

• Collectively or individually, the countries, individual agencies, or private stakeholders could use the proposed North American Methane Reduction framework to direct research, enhance monitoring and evaluate mitigation efforts, and improve the chances that continental methane reduction targets will be achieved.

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