Chrysophyte cyst-inferred variability of warm season lake water chemistry and climate in northern Poland: training set and downcore reconstruction     

I. Hernández-Almeida  M. Grosjean  W. Tylmann  A. Bonk 《Journal of Paleolimnology》2015,53(1):123-138

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Latest Results Found with Ring-Diagram Analysis     

C. S. Baldner  S. Basu  R. S. Bogart  O. Burtseva  I. González Hernández  D. Haber  F. Hill  R. Howe  K. Jain  R. W. Komm  M. C. Rabello-Soares  S. Tripathy 《Solar physics》2013,287(1-2):57-69

Ring-diagram analysis is a helioseismic tool useful for studying the near-surface layers of the Sun. It has been employed to study near-surface shear, meridional circulation, flows around sunspots, and thermal structure beneath active regions. We review recent results obtained using ring-diagram analysis, state some of the more important outstanding difficulties in the technique, and point out several extensions to the technique that are just now beginning to bear fruit.  相似文献   

Subsurface Flows in and Around Active Regions with Rotating and Non-rotating Sunspots     

K. Jain  R. W. Komm  I. González Hernández  S. C. Tripathy  F. Hill 《Solar physics》2012,279(2):349-363

The temporal variation of the horizontal velocity in sub-surface layers beneath three different types of active region is studied using the technique of ring diagrams. In this study, we select active regions (ARs) 10923, 10930, 10935 from three consecutive Carrington rotations: AR 10930 contains a fast-rotating sunspot in a strong emerging active region while other two have non-rotating sunspots with emerging flux in AR 10923 and decaying flux in AR 10935. The depth range covered is from the surface to about 12 Mm. In order to minimize the influence of systematic effects, the selection of active and quiet regions is made so that these were observed at the same heliographic locations on the solar disk. We find a significant variation in both components of the horizontal velocity in active regions as compared to quiet regions. The magnitude is higher in emerging-flux regions than in the decaying-flux region, in agreement with earlier findings. Further, we clearly see a significant temporal variation in depth profiles of both zonal and meridional flow components in AR 10930, with the variation in the zonal component being more pronounced. We also notice a significant influence of the plasma motion in areas closest to the rotating sunspot in AR 10930, while areas surrounding the non-rotating sunspots in all three cases are least affected by the presence of the active region in their neighborhood.  相似文献   

Flare-Shaped Acoustic Anomalies in the Water Column Along the Ecuadorian Margin: Relationship with Active Tectonics and Gas Hydrates     

Francois Michaud  Jean-Noël Proust  Alexandre Dano  Jean-Yves Collot  Grâce Daniella Guiyeligou  María José Hernández Salazar  Gueorgui Ratzov  Carlos Martillo  Hugo Pouderoux  Laure Schenini  Jean-Frederic Lebrun  Glenda Loayza 《Pure and Applied Geophysics》2016,173(10-11):3291-3303

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Field Survey of the 2015 Chile Tsunami with Emphasis on Coastal Wetland and Conservation Areas     

Manuel Contreras-López  Patricio Winckler  Ignacio Sepúlveda  Adolfo Andaur-Álvarez  Fernanda Cortés-Molina  Camila J. Guerrero  Cyntia E. Mizobe  Felipe Igualt  Wolfgang Breuer  José F. Beyá  Hernán Vergara  Rodrigo Figueroa-Sterquel 《Pure and Applied Geophysics》2016,173(2):349-367

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Air masses and aerosols chemical components in the free troposphere at the subtropical northeast atlantic region     

A. M. Díaz  J. P. Díaz  F. J. Expósito  P. A. Hernández-Leal  D. Savoie  X. Querol 《Journal of Atmospheric Chemistry》2006,53(1):63-90

The dynamics and the aerosol chemistry of the air masses reaching the free troposphere of the subtropical Northeast Atlantic region during the period 1995–98 have been studied. Seven days backward trajectories were calculated daily with HYSPLIT-4 model for Izaña Global Atmospheric Watch (GAW) Observatory (28.3^°N 16.5^°W, 2367 m a.s.l.). These back-trajectories were classified by means of a k-means clustering strategy. The daily air masses have been coded using 16 variables to detect the aerosol load of each one of them. Four clusters were found: Cluster 1, representative of Atlantic oceanic middle troposphere air masses, (OMT), has an average frequency of occurrence of 50.6%. Cluster 2, which includes air masses originated in the African continent (AfD), has been recorded in a 19.8% of time. Cluster 3 represents a mixture at least of two of the next sources: Europe, Africa and Ocean, (EAM), with a frequency of 12.7%. Finally, Cluster 4 includes air masses with a high load of maritime aerosols, (MaA), and it has been detected in a 16.9%. An analysis of four aerosol components: NO₃ ^?, NH₄ ⁺, non-sea-salt-SO₄ ^2?, and mineral dust and its relation with the origin and transport of the air masses have been done. The highest quantities of mineral dust and nss-SO₄ ^2? are linked with African air masses with a mean value of 86.5 and 1.9 μg/m³ respectively. Whereas the highest levels of NO₃ ^?, 1.0 μg/m³, and NH₄ ⁺, 0.4 μg/m³, were obtained for AfD and EAM. The lowest levels were associated with OMT and MaA air masses types: 12.7, 0.6, 0.2, and 0.5 μg/m³ for dust, NO₃ ^?, NH₄ ⁺, and nss-SO₄ ^2? in average for the four studied years. However, it is remarkable that the values of the median for dust are 2.2 and 3.5 μg/m³ in clusters MaA and OMT respectively. Using non-parametric statistical tests the distributions of concentrations in each cluster by year have been compared in order to detect similarities. The results show that the aerosol loads of OMT and MaA air masses are quite similar and the same occurs for AfD and EAM air masses. However, the correlation analysis between the levels of anions and ammonium evidenced important differences among the air mass types. In AfD air masses is clear a low correlation between levels of nss-SO₄ ^2? and NH₄ ⁺ (r ² = 0.08) suggesting that the sulfate speciation was dominated by sulfate species others than ammonium sulfate, such as calcium sulfate. CaSO₄ ?2H₂O (gypsum) is mainly present in the coarse mode, where the radiative effects of sulfate are less important that in the accumulative mode. For OMT air masses is noticeable an important increasing on the correlation between the levels of anions and those of NH₄ ⁺ for the two last years of the study period (1997–1998, r ² = 0.61 –0.85%) with respect to the first ones (1995–1996, r ² = 0.25–0.49%), coinciding with the second strongest ENSO (El Niño Southern Oscillation) event recorded. This behavior indicates a change in the speciation of the aerosol component.  相似文献   

“Normal” to adakite-like arc magmatism associated with the El Abra porphyry copper deposit,Central Andes,Northern Chile     

Rabbia  Osvaldo M.  Correa  Karen J.  Hernández  Laura B.  Ulrich  Thomas 《International Journal of Earth Sciences》2017,106(8):2687-2711

International Journal of Earth Sciences - The El Abra porphyry copper deposit belongs to the Late Eocene—Early Oligocene metallogenic belt of northern Chile, which host several world-class...  相似文献   

ENSO and solar activity signals from oxygen isotopes in diatom silica during late glacial-Holocene transition in Central Andes (18°S)     

Armand Hernández  Santiago Giralt  Roberto Bao  Alberto Sáez  Melanie J. Leng  Philip A. Barker 《Journal of Paleolimnology》2010,44(2):413-429

The late glacial-Holocene transition from the Lago Chungará sedimentary record in northern Chilean Altiplano (18°S) is made up of laminated sediments composed of light-white and dark-green pluriannual couplets of diatomaceous ooze. Light-white sediment laminae accumulated during short-term extraordinary diatom blooms whereas dark-green sediment laminae represent the baseline limnological conditions during several years of deposition. Diatom oxygen isotope ratios (δ¹⁸O_diatom) from 40 consecutive dark-green laminae, ranging from 11,990 to 11,450 cal year BP, show that a series of decadal-to-centennial dry–wet oscillations occurred. Dry periods are marked by relatively high isotope values whereas wet episodes are indicated by lower values. This interpretation agrees with the reconstructions of terrigenous inputs and regional effective moisture availability carried out in the lake but there is a systematic temporal disagreement between them owing to the non-linear response of the lacustrine ecosystem to environmental forcings. Furthermore, the δ¹⁸O_diatom record tracks effective moisture changes at a centennial scale. Three major phases have been established (11,990–11,800, 11,800–11,550, and 11,550–11,450 cal year BP). Each phase is defined by an increasing isotope trend followed by a sudden depletion. In addition, several wet and dry events at a decadal scale are superimposed onto these major trends. Spectral analyses of the δ¹⁸O_diatom values suggest that cycles and events could have been triggered by both El Niño-Southern Oscillation (ENSO) and solar activity. Significant ENSO frequencies of 7–9 years and 15–17 years, and periodicities of the solar activity cycles such as 11 years (Schwabe), 23 years (Hale) and 35 years (Brückner) have been recognised in the oxygen isotope time series. Time–frequency analysis shows that although solar and ENSO forcing were present at the onset of the Holocene, they were more intense during the late glacial period. The early Holocene might have been mainly governed by La Niña-like conditions that correspond to wet conditions over the Andean Altiplano.  相似文献   

Changes in the Diffuse CO2 Emission and Relation to Seismic Activity in and around El Hierro, Canary Islands     

Eleazar Padrón  Gladys Melián  Rayco Marrero  Dácil Nolasco  José Barrancos  Germán Padilla  Pedro A. Hernández  Nemesio M. Pérez 《Pure and Applied Geophysics》2008,165(1):95-114

Significant changes in the diffuse emission of carbon dioxide were recorded in a geochemical station located at El Hierro, Canary Islands, before the occurrence of several seismic events during 2004. Two precursory CO₂ efflux increases started thirteen and nine days before two seismic events of magnitude 2.3 and 1.7, which took place near El Hierro Island, Canary Islands, on March 23 and April 15, reaching a maximun value of 51.1 and 46.2 g m⁻² d⁻¹, respectively, five and eight days before the two seismic events. Other similar increases started thirteen and five days before the occurrence of two seismic events of magnitude 1.3 and 1.5 which took place on October 15 and 21 respectively, reaching the maximum values four and one day before the earthquakes. These changes were not related to variations in atmospheric or soil parameters. The Material Failure Forecast Method (FFM), which analyzes the rate of precursory phenomena, was successfully applied to forecast the first seismic event that took place in El Hierro Island in 2004.  相似文献   

Insights of long-term geomorphological evolution of coastal landscapes in hot-spot oceanic islands     

Nicolas Ferrer-Valero  Luis Hernández-Calvento  Antonio I. Hernández-Cordero 《地球表面变化过程与地形》2019,44(2):565-580

The Canary Islands form a volcanic archipelago in which a west–east (W–E) chain of progressively older and less active islands can be observed. In the Canary Islands, unlike most hot-spot archipelagos, certain geodynamic peculiarities have promoted longer periods of island survival, exceeding 20 Myr. This factor makes these islands a suitable context for this work, which aims to analyze extensively the coastal geomorphic structure on islands with different development states. For this, three islands in different volcanic phases were selected: La Palma (1.8 Myr), Gran Canaria (14.5 Myr) and Fuerteventura (22.6 Myr). An ad hoc landform-based hierarchical taxonomy was designed to analyze the coastal geomorphic structure of the three islands. Based on a multi-sourced analysis in geographic information system (GIS) and field recognition, a comprehensive cartographic database was collected using the coastline data-storing (CDS) method as a feature abundance proxy. Three different aspects of the geomorphological structure were compared and related between the islands: (i) composition, (ii) abundance and (iii) diversity. Through their comparison, we attempt to explore geomorphological aspects of coastal evolution over geological spatiotemporal scales. Composition was explored analyzing the distribution of the feature's longshore frequencies (p). Abundance, by metrics of local abundance (N_∩) and whole density (N_U). Diversity, through four indices: normalized richness (S) and Margalef index (M) to estimate richness; Simpson index (D) and Shannon index (H’) to estimate evenness. We identified a systematic transformation in the dominant landform composition and a systematic trend in increasing geomorphological abundance and diversity from younger to older islands. The results show a long-term structural pattern defined by the increase in coastal geomorphic complexity (abundance and diversity) over geological time, as the coasts evolve from predominantly rocky-erosive to increasingly clastic-depositional environments. This long-term geomorphological pattern may be a general aspect of hot-spot island archipelagos, which can bring a new perspective to the knowledge of their coastal evolution. © 2018 John Wiley & Sons, Ltd.  相似文献