Predictability of the mid-latitude Atlantic meridional overturning circulation in a multi-model system   总被引：1，自引：1，他引：0  

Holger Pohlmann  Doug M. Smith  Magdalena A. Balmaseda  Noel S. Keenlyside  Simona Masina  Daniela Matei  Wolfgang A. Müller  Philippe Rogel 《Climate Dynamics》2013,41(3-4):775-785

Assessing the skill of the Atlantic meridional overturning circulation (AMOC) in decadal hindcasts (i.e. retrospective predictions) is hampered by a lack of observations for verification. Models are therefore needed to reconstruct the historical AMOC variability. Here we show that ten recent oceanic syntheses provide a common signal of AMOC variability at 45°N, with an increase from the 1960s to the mid-1990s and a decrease thereafter although they disagree on the exact magnitude. This signal correlates with observed key processes such as the North Atlantic Oscillation, sub-polar gyre strength, Atlantic sea surface temperature dipole, and Labrador Sea convection that are thought to be related to the AMOC. Furthermore, we find potential predictability of the mid-latitude AMOC for the first 3–6 year means when we validate decadal hindcasts for the past 50 years against the multi-model signal. However, this predictability is not found in models driven only by external radiative changes, demonstrating the need for initialization of decadal climate predictions.  相似文献   

The potential added value of Regional Climate Models in South America using a multiresolution approach     

Magdalena Falco  Andrea F. Carril  Laurent Z. X. Li  Carlos Cabrelli  Claudio G. Men&#;ndez 《Climate Dynamics》2020,54(3):1553-1569

This paper aims to identify those regions within the South American continent where the Regional Climate Models (RCMs) have the potential to add value (PAV) compared to their coarser-resolution global forcing. For this, we used a spatial-scale filtering method based on the wavelet theory to distinguish the regional climatic signal present in atmospheric surface fields from observed data (CPC and TRMM) and 6 RCM simulations belonging to the CORDEX Project. The wavelet used for filtering was Haar wavelet, but a comparative analysis with Daubechies 4 wavelet indicated that meteorological fields or regional indices were not very sensitive to the wavelet selected. Once the longer wavelengths were filtered, we focused on analyzing the spatial variability of extreme rainfall and the spatiotemporal variability of maximum and minimum surface air temperature on a daily basis. The results obtained suggest essential differences in the spatial distribution of the small-scale signal of extreme precipitation between TRMM and regional models, together with a large dispersion between models. While TRMM and CPC register a large signal throughout the continent, the RCMs place it over the Andes Cordillera and some over tropical South America. PAV signal for surface air temperature was found over the Andes Cordillera and the Brazilian Highlands, which are regions characterized by complex topography, and also on the coasts of the continent. The signal came specially from the small-scale stationary component. The transient part is much smaller than the stationary one, except over la Plata Basin where they are of the same order of magnitude. Also, the RCMs and CPC showed a large spread between them in representing this transient variability. The results confirm that RCMs have the potential to add value in the representation of extreme precipitation and the mean surface temperature in South America. However, this condition is not applicable throughout the whole continent but is particularly relevant in those terrestrial regions where the surface forcing is strong, such as the Andes Cordillera or the coasts of the continent.  相似文献   

Reconstruction of landscape paleohydrology using the sediment archives of three dystrophic lakes in northeastern Poland   总被引：1，自引：0，他引：1  

Danuta Drzymulska  Magdalena Fiłoc  Mirosława Kupryjanowicz 《Journal of Paleolimnology》2014,51(1):45-62

Sediment layers of uniform age within lakes (isochrones) and their patterns reflect accumulation processes which can be correlated with hydrologic conditions in lake basins. The sedimentary archives in three small dystrophic lakes in northeastern Poland are described based on the correlation of local pollen assemblage zones in cores that were collected from the centers and margins of each lake. Past regional groundwater levels could be discerned from the shape of the isochrones, whether plane parallel or concave in configuration in relation to the lake basin shape. The concave configuration of the isochrones in the studied lakes shows that regional groundwater levels remained mostly high and stable throughout their history. The water levels in each lake during the Late Glacial and throughout the Holocene were different and no single, common water-level fluctuation pattern was identified in the three water bodies. The lack of such a finding suggests that the lakes are influenced dominantly by local hydrological factors.  相似文献   

Deep 3D thermal modelling for the city of Berlin (Germany)   总被引：1，自引：1，他引：0  

Judith Sippel  Sven Fuchs  Mauro Cacace  Anna Braatz  Oliver Kastner  Ernst Huenges  Magdalena Scheck-Wenderoth 《Environmental Earth Sciences》2013,70(8):3545-3566

This study predicts the subsurface temperature distribution of Germany’s capital Berlin. For this purpose, a data-based lithosphere-scale 3D structural model is developed incorporating 21 individual geological units. This model shows a horizontal grid resolution of (500 × 500) m and provides the geometric base for two different approaches of 3D thermal simulations: (1) calculations of the steady-state purely conductive thermal field and (2) simulations of coupled fluid flow and heat transport. The results point out fundamentally different structural and thermal configurations for potential geothermal target units. The top of the Triassic Middle Buntsandstein strongly varies in depth (159–2,470 m below sea level) and predicted temperatures (15–95 °C), mostly because of the complex geometry of the underlying Permian Zechstein salt. The top of the sub-salt Sedimentary Rotliegend is rather flat (2,890–3,785 m below sea level) and reveals temperatures of 85–139 °C. The predicted 70 °C-isotherm is located at depths of about 1,500–2,200 m, cutting the Middle Buntsandstein over large parts of Berlin. The 110 °C-isotherm at 2,900–3,700 m depth widely crosscuts the Sedimentary Rotliegend. Groundwater flow results in subsurface cooling the extent of which is strongly controlled by the geometry and the distribution of the Tertiary Rupelian Clay. The cooling effect is strongest where this clay-rich aquitard is thinnest or missing, thus facilitating deep-reaching forced convective flow. The differences between the purely conductive and coupled models highlight the need for investigations of the complex interrelation of flow- and thermal fields to properly predict temperatures in sedimentary systems.  相似文献   

Measuring a charge-coupled device point spread function     

Sami-Matias Niemi  Mark Cropper  Magdalena Szafraniec  Thomas Kitching 《Experimental Astronomy》2015,39(2):207-231

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Kinetics of crystal nucleation in ionic solutions: Electrostatics and hydration forces     

Magdalena Kowacz  Manuel Prieto 《Geochimica et cosmochimica acta》2010,74(2):469-4350

The heat of precipitation, the mean crystal size and the broadness of crystal size distribution of barium sulfate precipitating in aqueous solutions of different background electrolytes (KCl, NaCl, LiCl, NaBr or NaF), was shown to vary at constant thermodynamic driving force (supersaturation) and constant ionic strength depending on the salt present in solution. The relative inversion in the effect of respective background ions on the characteristics of barite precipitate was observed between two studied supersaturation (Ω) and ionic strength (IS) conditions. The crystal size variance (β²) increased in the presence of background electrolytes in the order LiCl < NaCl < KCl at Ω = 10^3.33 and IS = 0.03 M and KCl < NaCl < LiCl at Ω = 10^3.77 and IS = 0.09 M. At a given Ω and IS the respective size of barite crystals decreased with increasing β² in chloride salts of different cations and remained constant in sodium salts of different anions.We suggest that ionic salts affect the kinetics of barite nucleation and growth due to their influence on water of solvation and bulk solvent structure. This idea is consistent with the hypothesis that the kinetic barrier for barium sulfate nucleation depends on the frequency of water exchange around respective building units that can be modified by additives present in solution. In electrolyte solution the relative switchover between long range electrostatic interactions and short range hydration forces, which influence the dynamics of solvent exchange between an ion solvation shell and bulk fluid, results in the observed inversion in the effect of differently hydrated salts on nucleation rates and the resulting precipitate characteristics.  相似文献   

Behaviour of metals and nutrients in soils and groundwater of a karst polje   总被引：2，自引：0，他引：2  

Tamara Markovic  Slobodan Miko  Sanja Kapelj  Renato Buljan  Ozren Larva  Zoran Peh 《Journal of Geochemical Exploration》2006,88(1-3):124

The Croatian south part of the country is mainly composed of strongly krastified carbonate rocks. Also in this south part of Croatia is lacking of large depressions and poljes with thick covers. Some karst poljes and depressions may have thick covers, like for example the Vransko polje. The Vransko polje is characterised by an intensive agricultural activity. At the centre of the polje is located a karst spring (Turanjsko jezero), which is used for the water supply of the town Biograd and its surroundings. Total metals, nutrients (nitrate, ammonia, phosphate), organic matter content and cation exchange capacity (CEC) were measured in soil samples collected from the polje. Metals and nutrients were also measured in the water samples of channel Kotarka (which is passing through the area) and three springs (Turanjsko jezero, Kakma and Tinj). Measured total concentrations of metals of soil samples were treated by R-cluster multivariate statistical analysis. The result of statistical analysis showed grouping of metals with similar behaviour. Content of metals and nutrients were low in the spring samples but high in the water sample of the channel Kotarka, because the channel drains the water from the surroundings. Although agricultural activity in the Vransko polje is high, there is no high anthropogenic influence on groundwater and soil. They are both of good quality.  相似文献   

Magnetic,paleomagnetic and palynologic studies of Paleolithic depositions of the Akhshtyrskaya cave (Russia)     

Genrietta A. Pospelova  Elżbieta Król  Galina M. Levkovskaya  Jadwiga Kruczyk  Magdalena Kądziałko-Hofmokl  Sergey A. Kulakov 《Acta Geophysica》2007,55(4):619-639

The paper presents the results of experimental rock-magnetic, paleomagnetic and palynologic study of Paleolithic sediments sampled along two profiles in the Akhshtyrskaya cave, situated in the vicinity of Black Sea shore. In the upper part of profiles, some magnetite was observed; in the middle and lower parts, strongly oxidized non-stoichiometric magnetite and hematite prevail. Thin maghemite covers on the surface of fine magnetite grains are present in the majority of specimens. Natural remanence has one characteristic component (CHRM), mostly of chemical origin, although in few specimens containing magnetite it may be sedimentary. Directions of CHRM obtained by standard paleomagnetic methods revealed anomalous pattern only in layer 3/2, which is slightly older than the overlying layer 3/1 whose age was established as (35±2)×10³ years BP by the U-Th method. This suggests that this paleomagnetic anomaly (PMA) can be correlated with Kargapolovo excursion dated on about (45−39)×10³ years BP. In the remaining overlying and underlying layers, directions of CHRM are grouped around the present geomagnetic field. Depth distributions of scalar magnetic parameters generally coincide with the lithological division of the profiles. Palynologic study revealed the presence of 22 pollen zones. Five thermomers separated with colder periods were found in the middle and lower parts of profile. The non-magnetite composition of magnetic fraction of the majority of studied sediments — oxidized nonstoichiometric magnetite and hematite — resulted in the lack of correlations between paleoclimatic and scalar magnetic characteristics.  相似文献   

Basin evolution of the northern part of the Northeast German Basin — Insights from a 3D structural model     

Martin Bak Hansen  Magdalena Scheck-Wenderoth  Christian Hübscher  Holger Lykke-Andersen  Ali Dehghani  Benjamin Hell  Dirk Gajewski 《Tectonophysics》2007,437(1-4):1-16

A 3D structural model for the entire southwestern Baltic Sea and the adjacent onshore areas was created with the purpose to analyse the structural framework and the sediment distribution in the area. The model was compiled with information from several geological time-isochore maps and digital depth maps from the area and consists of six post-Rotliegend successions: The Upper Permian Zechstein; Lower Triassic; Middle Triassic; Upper Triassic–Jurassic; Cretaceous and Cenozoic. This structural model was the basis for a 3D backstripping approach, considering salt flow as a consequence of spatially changing overburden load distribution, isostatic rebound and sedimentary compaction for each backstripping step in order to reconstruct the subsidence history in the region. This method allows determination of the amount of tectonic subsidence or uplifting as a consequence of the regional stress field acting on the basin and was followed by a correlation with periods of active salt movement. In general, the successions above the highly deformed Zechstein evaporites reveal a thickening trend towards the Glückstadt Graben, which also experienced the highest amount of tectonic subsidence during the Mesozoic and Cenozoic. Two periods of accelerating salt movement in the area has been correlated with the E–W directed extension during the Late Triassic–Early Jurassic and later by the Late Cretaceous–Early Cenozoic inversion, suggesting that the regional stress field plays a key role in halokinesis. The final part of this work dealt with a neotectonic forward modelling in an attempt to predict the future topography when the system is in a tectonic equilibrium. The result reveals that many of the salt structures in the region are still active and that future coastline will run with a WNW–ESE trend, arguing that the compressional stresses related to the Alpine collision are the prime factor for the present-day landscape evolution.  相似文献   

Book review     

David Gubbins  Emile A. Okal  Roberto Scarpa  R. E. Anderson  Leszek Czechowski  Rodney W. Page  Bernhard Spörli  Magdalena Kądziałko-Hofmokl  J. A. Majorowicz  Gregory Houseman  Donald L. Turcotte  David F. McTigue  Teng-fong Wong  David Lockner  David V. Wiltschko  David M. Fountain  G. P. Glasby  R. J. Angel  S. J. Gibowicz  Jonathan Franzen  Kacper R. Rybicki  Brian Farrell  Anil Suri  Zbigniew W. Kundzewicz  Witold G. Strupczewski 《Pure and Applied Geophysics》1988,127(4):695-752

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