Hydrogeomorphic processes of thermokarst lakes with grounded‐ice and floating‐ice regimes on the Arctic coastal plain,Alaska     

Christopher D. Arp  Benjamin M. Jones  Frank E. Urban  Guido Grosse 《水文研究》2011,25(15):2422-2438

Thermokarst lakes cover > 20% of the landscape throughout much of the Alaskan Arctic Coastal Plain (ACP) with shallow lakes freezing solid (grounded ice) and deeper lakes maintaining perennial liquid water (floating ice). Thus, lake depth relative to maximum ice thickness (1·5–2·0 m) represents an important threshold that impacts permafrost, aquatic habitat, and potentially geomorphic and hydrologic behaviour. We studied coupled hydrogeomorphic processes of 13 lakes representing a depth gradient across this threshold of maximum ice thickness by analysing remotely sensed, water quality, and climatic data over a 35‐year period. Shoreline erosion rates due to permafrost degradation ranged from < 0·2 m/year in very shallow lakes (0·4 m) up to 1·8 m/year in the deepest lakes (2·6 m). This pattern of thermokarst expansion masked detection of lake hydrologic change using remotely sensed imagery except for the shallowest lakes with stable shorelines. Changes in the surface area of these shallow lakes tracked interannual variation in precipitation minus evaporation (P ? E_L) with periods of full and nearly dry basins. Shorter‐term (2004–2008) specific conductance data indicated a drying pattern across lakes of all depths consistent with the long‐term record for only shallow lakes. Our analysis suggests that grounded‐ice lakes are ice‐free on average 37 days longer than floating‐ice lakes resulting in a longer period of evaporative loss and more frequent negative P ? E_L. These results suggest divergent hydrogeomorphic responses to a changing Arctic climate depending on the threshold created by water depth relative to maximum ice thickness in ACP lakes. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Climate variability and Alpine glaciers evolution in Northwestern Italy from the Little Ice Age to the 2010s     

Guido Nigrelli  Stefania Lucchesi  Stefania Bertotto  Gianfranco Fioraso  Marta Chiarle 《Theoretical and Applied Climatology》2015,122(3-4):595-608

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Columnar jointing in vapor-phase-altered,non-welded Cerro Galán Ignimbrite,Paycuqui, Argentina     

Heather M. N. Wright  Chiara Lesti  Raymond A. F. Cas  Massimiliano Porreca  José G. Viramonte  Chris B. Folkes  Guido Giordano 《Bulletin of Volcanology》2011,73(10):1567-1582

Columnar jointing is thought to occur primarily in lavas and welded pyroclastic flow deposits. However, the non-welded Cerro Galán Ignimbrite at Paycuqui, Argentina, contains well-developed columnar joints that are instead due to high-temperature vapor-phase alteration of the deposit, where devitrification and vapor-phase crystallization have increased the density and cohesion of the upper half of the section. Thermal remanent magnetization analyses of entrained lithic clasts indicate high emplacement temperatures, above 630°C, but the lack of welding textures indicates temperatures below the glass transition temperature. In order to remain below the glass transition at 630°C, the minimum cooling rate prior to deposition was 3.0 × 10⁻³–8.5 × 10⁻²°C/min (depending on the experimental data used for comparison). Alternatively, if the deposit was emplaced above the glass transition temperature, conductive cooling alone was insufficient to prevent welding. Crack patterns (average, 4.5 sides to each polygon) and column diameters (average, 75 cm) are consistent with relatively rapid cooling, where advective heat loss due to vapor fluxing increases cooling over simple conductive heat transfer. The presence of regularly spaced, complex radiating joint patterns is consistent with fumarolic gas rise, where volatiles originated in the valley-confined drainage system below. Joint spacing is a proxy for cooling rates and is controlled by depositional thickness/valley width. We suggest that the formation of joints in high-temperature, non-welded deposits is aided by the presence of underlying external water, where vapor transfer causes crystallization in pore spaces, densifies the deposit, and helps prevent welding.  相似文献   

A nonlinear programming analysis of unconfined steady-state seepage     

Giancarlo Gioda  Carmelo Gentile 《国际地质力学数值与分析法杂志》1987,11(3):283-305

A finite element, variable mesh analysis of unconfined steady-state seepage problems is presented based on a nonlinear programming algorithm. It is shown that the minimization of an objective function which merely represents a measure of the total flux leaving or entering the mesh at the free surface nodes (except those that belong also to pervious boundaries) does not permit a unique definition of the free surface geometry. This problem, which is apparently related to the numerical instabilities often met when using variable mesh approaches, can be eliminated by adding to the objective function a term representing a sort of overall ‘regularity’ condition for the shape of the free surface. The modified solution procedure turns out to be stable and able to provide meaningful results for practical problems even when rather coarse meshes are adopted.  相似文献   

Horizontally travelling waves in a group of piles taking pile-soil-pile interaction into account     

John P. Wolf  Guido A. von Arx 《地震工程与结构动力学》1982,10(2):225-237

A reactor building founded on a large number of piles situated in a layered site is analysed for an historic earthquake assumed to be propagating horizontally. Pile-soil-pile interaction is properly accounted for, incorporating the frequency-dependent stiffness and radiation damping. Compared to vertical incidence, the pile forces are increased and the piles close to the boundary are loaded more heavily than those in the centre region of the basemat.  相似文献   

Geology and utilization of underground space in metropolitan Kansas City area, USA     

R. J. Gentile 《Environmental Geology》1997,29(1-2):11-16

 Kansas City is the international leader in the commercial development of mined-out areas for warehousing, manufacturing, offices, business, and service-related activities. Over 3000 people work underground at about two dozen sites with a combined floor space of almost 2 sq km. Most of the space was created after mining a 6-m-thick bed of limestone that underlies the city and its environs. The most common usage of the space is for storage. The mined-out area can be converted to warehouse storage at a fraction of the cost of a comparable surface facility. Received: 2 October 1995 · Accepted: 6 November 1995  相似文献   

On the radio properties of the highest redshift quasars     

M. Cirasuolo  M. Magliocchetti  G. Gentile  A. Celotti  S. Cristiani  L. Danese 《Monthly notices of the Royal Astronomical Society》2006,371(2):695-702

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Magnetic fields in the centre of the Perseus cluster     

G. B. Taylor  N. E. Gugliucci  A. C. Fabian  J. S. Sanders  G. Gentile  S. W. Allen 《Monthly notices of the Royal Astronomical Society》2006,368(4):1500-1506

We present Very Long Baseline Array (VLBA) observations of the nucleus of NGC 1275, the central, dominant galaxy in the Perseus cluster of galaxies. These are the first observations to resolve the linearly polarized emission from 3C 84, and from them we determine a Faraday rotation measure (RM) ranging from 6500 to 7500 rad m⁻² across the tip of the bright southern jet component. At 22 GHz some polarization is also detected from the central pc of 3C 84, indicating the presence of even more extreme RMs that depolarize the core at lower frequencies. The nature of the Faraday screen is most consistent with being produced by magnetic fields associated with the optical filaments of ionized gas in the Perseus cluster.  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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Correction to: Benchmarking the software packages to model and assess the seismic response of unreinforced masonry existing buildings through nonlinear static analyses     

Cattari  Serena  Magenes  Guido 《Bulletin of Earthquake Engineering》2022,20(4):1937-1937

Bulletin of Earthquake Engineering - A correction to this paper has been published: https://doi.org/10.1007/s10518-021-01105-0  相似文献