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1
Makar, P. A., J. Zhang, W. Gong, C. Stroud, D. Sills, K. L. Hayden, J. Brook, et al. "Mass tracking for chemical analysis: the causes of ozone formation in southern Ontario during BAQS-Met 2007." Atmospheric Chemistry and Physics 10, no. 22 (November 26, 2010): 11151–73. http://dx.doi.org/10.5194/acp-10-11151-2010.
Повний текст джерелаАнотація:
Abstract. A three-level nested regional air pollution model has been used to study the processes leading to high ozone concentrations in the southern Great Lakes region of North America. The highest resolution simulations show that complex interactions between the lake-breeze circulation and the synoptic flow lead to significant enhancements in the photochemical production and transport of ozone at the local scale. Mass tracking of individual model processes show that Lakes Erie and St. Clair frequently act as photochemical ozone production regions, with average mid-day production rates of up to 3 ppbv per hour. Enhanced ozone levels are evident over these two lakes in 23-day-average surface ozone fields. Analysis of other model fields and aircraft measurements suggests that vertical circulation enhances ozone levels at altitudes up to 1500 m over Lake St. Clair, whereas subsidence enhances ozone over Lake Erie in a shallow layer only 250 m deep. Mass tracking of model transport shows that lake-breeze surface convergence zones combined with the synoptic flow can then carry ozone and its precursors hundreds of kilometers from these source areas, in narrow, elongated features. Comparison with surface mesonet ozone observations confirm the presence, magnitude, and timing of these features, which can create local ozone enhancements on the order of 30 ppbv above the regional ozone levels. Sensitivity analyses of model-predicted ozone and HOx concentrations show that most of the region is VOC-limited, and that the secondary oxidation pathways of aromatic hydrocarbons have a key role in setting the region's ozone and HOx levels.
2
NAGY, BÉLA, and BRIAN R. WATTERS. "Lacustricola margaritatus, a new species of lampeye from the Lake Victoria and Lake Kyoga basins in eastern Africa (Cyprinodontiformes: Procatopodidae)." Zootaxa 5128, no. 1 (April 19, 2022): 44–60. http://dx.doi.org/10.11646/zootaxa.5128.1.2.
Повний текст джерелаАнотація:
Lacustricola margaritatus, a new species inhabiting small streams and swamps in the Lake Victoria basin in north-western Tanzania and southern Uganda, and the Lake Kyoga basin in central Uganda, is described. Lacustricola margaritatus is a small species with a moderately deep body, moderate dimorphism and pronounced dichromatism. It is distinguished from all other Procatopodidae by the following unique combination of characters: live male body colour pattern with vertically-elongated iridescent light blue patches at scale centres, forming a striped appearance of dotted longitudinal lines on the flanks, particularly evident in the two or three series below the mid-longitudinal line; male having deeply coloured unpaired fins with orange-brown in the proximal and median parts and a narrow black distal band; male with a yellow base along the pectoral fin; female with dark grey scale margins and dark grey patches on scales along mid-longitudinal series creating a narrow dark grey stripe; both sexes showing inconspicuous postopercular blotch; and in both sexes, the cephalic sensory system is entirely situated in open grooves at all levels. The new species has previously often been misidentified as L. pumilus, originally described as inhabiting the Lake Tanganyika basin in north-eastern Zambia, or 'L.' centralis, from the Lake Rukwa basin in south-western Tanzania. Lacustricola margaritatus differs from the above two species by morphometric and meristic characters, body and fin colouration, and in arrangement of the cephalic sensory system.
3
Bell, C. M., and M. Suarez. "The depositional environments and tectonic development of a Mesozoic intra-arc basin, Atacama Region, Chile." Geological Magazine 130, no. 4 (July 1993): 417–30. http://dx.doi.org/10.1017/s0016756800020501.
Повний текст джерелаАнотація:
AbstractA thick succession of continental redbeds was deposited in a 50 km wide intra-arc basin on the Andean active continental margin in the Atacama region of northern Chile during early Cretaceous times. Upper Jurassic to early Cretaceous marine limestones were buried by the seaward progradation of a succession of coastal dunes, saline lakes and sandflats. Aeolian dune fields migrating towards the east across these coastal plains became stabilized by the growth of vegetation. Interdune alluvial areas between the sand dunes and dune fields developed into extensive alluvial braid plains which were in turn superimposed by alluvial fans. These fans were inundated by a regionally extensive saline lake produced by tectonic or volcanic damming of the sedimentary basin. This lake dried up leaving a large area of playa-lake mudflats. The climate was warm and semi-arid with a low and seasonal rainfall. Parts of the area supported a substantial vegetation of woody plants, together with a vertebrate fauna of dinosaurs, pterosaurs and crocodiles. The continental redbeds were derived from a volcanic source and were deposited on continental crust in a deep but narrow, north-south elongated, fault-bounded graben. This extensional basin formed in an intra-arc setting within an active andesitic volcanic chain. Upwards-coarsening sedimentary successions were the product of uplift of the fault-bounded margins of the basin.
4
Jawad, L. A., M. M. S. Farrag, and J. M. Park. "Interspecific and intraspecific differences in pectoral-fins spine morphology in Nile River and Lake Nasser catfishes, Siluriformes." Proceedings of the Zoological Institute RAS 325, no. 3 (September 25, 2021): 308–22. http://dx.doi.org/10.31610/trudyzin/2021.325.3.308.
Повний текст джерелаАнотація:
The structure of the pectoral fins spine of 4 catfish species Heterobranchus longifilis, Clarias gariepinus, Chrysichthys auratus, Synodontis schall and Synodontis serratus were described. The fish specimens were collected from Asyut City and Lake Nasser about 319 and 900 Km south of the capital Cairo, Egypt respectively on 10 November 2017 are described. The species examined showed variation in the shape of the spine-shaft tip varies from finely to broadly and rounded pointed; the curvature of the spine-shaft is either straight or curved partially or complete; the anterior serrae varies between is either broad or irregular; the anterior ridge groove is well developed, deep, and curved, with some pores in some species; the anterior dentations varies between short and sometimes are merged together or curved and their number decreased towards the tip; the posterior dentations can vary between absent or long and numerous and sometimes increased in their number towards the tip of the spine; the dorsal, anterior and ventral processes are well developed structures, with rounded, flange-like, and the shape of the basal fossa varies in having narrow, elongated, boat-shape, with high walls at sides; and very wide fossa and lunate in shape. It is usually deep with high walls.
5
Orlić, Mirko, and Martin Lazar. "Cyclonic versus Anticyclonic Circulation in Lakes and Inland Seas." Journal of Physical Oceanography 39, no. 9 (September 1, 2009): 2247–63. http://dx.doi.org/10.1175/2009jpo4068.1.
Повний текст джерелаАнотація:
Abstract A simple diagnostic model, reproducing circulation in lakes and marginal seas in which low-density waters are found close to the coasts while high-density waters dominate the offshore areas, is developed. An explicit solution is obtained for the central transverse section of an elongated basin, assuming that the Boussinesq and hydrostatic approximations are valid and that the alongshore variability vanishes. The model reveals cyclonic circulation that may either extend throughout the vertical (type C) or may top anticyclonic circulation developed in the bottom layer (type C/A). With the amplitude of the imposed density anomaly being fixed, the flow type is controlled by the frictional processes and by the basin dimensions. In a typical basin, type C/A flow is supported by weak bottom and vertical friction and by moderate lateral friction, unlike type C flow, which is supported by moderate bottom and vertical friction and by weak lateral friction. Strong frictional influence, especially in the basin interior, suppresses the flow everywhere. The flow is also suppressed in a basin that is narrow O(1 km) and shallow O(10 m), even without the frictional control being too strong. A basin that is narrow and deep favors type C/A flow, whereas a basin that is wide and shallow tends to support type C flow. The theoretical findings are related to observations, particularly those originating from the Adriatic Sea where type C flow prevails but may occasionally be replaced by type C/A flow, as well as to previous modeling results.
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MANOEL, ALEX, ANDRÉ MORGADO ESTEVES, and PATRÍCIA FERNANDES NERES. "Two new species of Acantholaimus (Nematoda, Chromadoridae) from the deep southeastern Atlantic (Santos Basin)." Zootaxa 5209, no. 2 (November 16, 2022): 238–56. http://dx.doi.org/10.11646/zootaxa.5209.2.5.
Повний текст джерелаАнотація:
Two new species of the genus Acantholaimus (Nematoda, Chromadoridae) are described from the South Atlantic, in the Santos Basin off the slope of southeastern Brazil. Acantholaimus pugious sp. n. is characterized by a narrow and elongated anterior end; teeth that are thin and long stylet-like (two in number), amphidial fovea located far from the anterior end and occupying most of the corresponding body diameter. Acantholaimus bidentatus sp. n. is characterized by a narrow anterior end, cuticle with more evident dots on both body extremities (up to amphidial fovea and tail); two long, protractible thin teeth (similar to stylet), with curved proximal part. The two species are similar in the shape of the teeth. The teeth morphology may be correlated to the process of adaptive convergence of these species. An emended diagnosis of the genus is provided.
7
Thiengo, Silvana Carvalho. "On Pomacea sordida (Swainson, 1823) (Prosobranchia, Ampullariidae)." Memórias do Instituto Oswaldo Cruz 84, no. 3 (September 1989): 351–55. http://dx.doi.org/10.1590/s0074-02761989000300009.
Повний текст джерелаАнотація:
A description of Pomacea sordida (Swainson, 1823) collected in Caxias and Nova Iguaçu, state of Rio de Janeiro, is presented. The shell is globose, heavy, whith greenish or horn-colored periostracum and dark spinal bands; apex subelevated, 4-5 moderately shoudered whorls, increasing rather rapidly and separated by deep suture. Aperture large, moderately round, yellowish or violaceous; lip thick and sometimes dark brown; umbilicus large and deep; operculum corneous and heavy, entirely closing the aperture. Ratios: shell width/shell length = 0.81-0.91 (mean 0.86); aperture length/shell length = 0.66-0.75 (mean 0.70). Testis, spermiduct and penis pouch as in Pomacea lineata (Spix, 1827). Seminal vesicle whitish and bean-shaped. Prostate cylindric and narrow, cream in coloar as the testis. Penis whiplike whith a closed circular spermiduct. Penial sheath elongated and tapered, with its distal tip turned to the right; outer basal gland situated on the left; inner median gland rounded; apical gland elongated and wrinkled. Ovary composed of branched whitish tubules lying superficially on the digestive gland; oviduct and seminal receptacle as in P. lineata; albumen gland yellowish - orange. Vestigial male copulatory apparatus (penis and its sheath) present in all females examined.
8
Sitnikova, Tatiana, and Tatiana Peretolchina. "Description of a new species Gyraulus (Pulmonata: Planorbidae) from the land thermal spring Khakusy of Lake Baikal." ZooKeys 762 (May 30, 2018): 1–12. http://dx.doi.org/10.3897/zookeys.762.23661.
Повний текст джерелаАнотація:
A new species of the family Planorbidae is described from the land thermal spring Khakusy, on the north-eastern shore of Lake Baikal. The description of Gyraulustakhteevi sp. n. includes morphological characters and gene sequences (COI of mtDNA) for the species separation from sister taxon Gyraulusacronicus (A. Férussac, 1807) collected from the small Krestovka River in-flowing into the south-western part of the Lake. The new species differs from G.acronicus in small shell size of adults, having smaller number of prostate folds (maximal up to 26 in G.takhteevi n. sp. vs. 40 in G.acronicus), a short preputium (approximately twice shorter than the phallotheca), and an elongated bursa copulatrix. The population of Gyraulustakhteevi sp. n. consists of two co-existent morphs: one of them has a narrow shell spire and the second is characterized by wide spire similar to the shell of G.acronicus. One of the two revealed haplotypes of the new species includes both morphs, while the second consists of snails with wide spired shells.
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Garita-Alvarado, Carlos A., and Claudia Patricia Ornelas-García. "Parallel Evolution of Allometric Trajectories of Trophic Morphology between Sympatric Morphs of Mesoamerican Astyanax (Characidae)." Applied Sciences 11, no. 17 (August 30, 2021): 8020. http://dx.doi.org/10.3390/app11178020.
Повний текст джерелаАнотація:
Parallel evolution of the body shape and trophic-related traits has been detected between sympatric pairs of lake-dwelling characin fishes in Mesoamerica. Here, we evaluated the variation in and the ontogenetic allometric trajectories of trophic morphology between sympatric Astyanax morphs (elongate and deep-body) in two geographic systems, Lake Catemaco (Mexico) and San Juan River basin (Nicaragua and Costa Rica). Using geometric morphometrics, we determined the shape variation and disparity in the premaxillary bone, and the patterns of allometric trajectories between morphs in each system. We found a higher differentiation and disparity in the premaxilla shape between morphs from San Juan River basin than between the Lake Catemaco ones. We found shared (parallel evolution) patterns of divergence between systems, which included allometric trajectories showing a positive correlation between the premaxilla shape and log centroid size, as well as trajectories being extended in the elongated-body morph (truncated in the deep-body morph). Regarding the unique patterns of divergence, we recovered parallel allometric trajectories between morphs from Lake Catemaco, while the San Juan River basin morphs showed divergent trajectories. Our results are congruent with the hypothesis that divergence in trophic morphology can be considered a triggering factor in the divergence in the genus Astyanax from Mesoamerica.
10
Shaw, J. F. H., and E. E. Prepas. "Temporal and Spatial Patterns of Porewater Phosphorus in Shallow Sediments, and its Potential Transport into Narrow Lake, Alberta." Canadian Journal of Fisheries and Aquatic Sciences 46, no. 6 (June 1, 1989): 981–88. http://dx.doi.org/10.1139/f89-127.
Повний текст джерелаАнотація:
During 1985 and 1986, summer and spatial patterns of porewater soluble reactive phosphorus (SRP) from sediments ≤ 15-m depth were examined at Narrow Lake, a deep, mesoeutrophic Albertan lake. At three sites (different in depth and macrophyte colonization), trends in porewater SRP concentrations ([SRP]) in the top 5 cm of the sediment from May to August varied, possibly due to root uptake of SRP by macrophytes. At a depth of 5 m, mean (in the top 5 cm of the sediment) and variance of porewater [SRP] at one site (<0.15 m2) were the same as over the entire lake. Excluding data from macrophyte sites, porewater [SRP] were positively related to depth of the water column (P < 0.0001). Molecular diffusion of SRP from sediments with and without macrophytes located in the trophogenic zone was calculated. During summer, molecular diffusion from shallow sediments to the trophogenic zone was 0.05 mg∙m−2 d−1, or 29% of atmospheric deposition of phosphorus (P) (the major external source of P to the lake). A sampling strategy is discussed to enable the calculation of whole-lake P transport from shallow sediments to the trophogenic zone in lakes with similar morphometry and trophic status to Narrow Lake.
11
Thiengo, Silvana Carvalho. "Observations on the morphology of Pomacea lineata (Spix, 1827) (Mollusca, Ampullariidae)." Memórias do Instituto Oswaldo Cruz 82, no. 4 (December 1987): 563–70. http://dx.doi.org/10.1590/s0074-02761987000400015.
Повний текст джерелаАнотація:
This paper deals with the morpholgy of Pomacea lineata (Spix, 1827) collected at its type locality. The shell is globose, moderately heavy, horn-colored with brown spiral bands; apex subelevated; 4 - 5 rounded whorls increasing in diameter rather rapidly, separated by deep suture. Aperture large and ovoid; outer lip sharp; umbilicus narrow and deep; operculum concentric, corneous. Ratios: shell width/shell length = 0.74 - 0.83 (mean 0.78); spire length/shell length = 0.10 - 0.18 (mean 0.13); aperture length/shell length = 0.70 - 0.77 (mean 0.73). The animal is longisiphonate. Renal organ brownish with marked invagination at its right edge. Ureter elongated with its long axis transverse to the main axis of the kidney. The radula is taenioglossate (2.1.1.1.2) and has on average 35 transverse rows of teeth. The form and arrangement of the radula teeth are nearly the same as in other Ampullariidae. The testis is cream-colored and lies in the first three whorls of the spire. Spermiduct uniformly narrow, running to the base of the spire. Seminal vesicle whitish, slightly pressed dorsoventrally. Prostate cylindric and thick, similar in color to the testis. Penis whiplike, with a closed circular spermiduct. Penis pouch ovoid completely envelping the penis. Penis sheath elongated, broad prosimally, tapering distally. Its inner surface shows a longitudinal channel along its proximal half and two glands, one on the middle and the other apical. Ovary composed of branched whitish tubules situated on the surface of the digestive gland. Oviduct slender running along the columellar axis toward the base of the spire. Seminal receptalble tubiform, thick-walled and rounded proximally. Albumen gland large, pink, enclosing the receptacle and the spiral capsule gland. Vestigial male copulatory apparatus (penis and its sheath) present in all females examined.
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Chen, Ji, Jun Feng Cui, and Shi Yu Wang. "Depositional System of Aershan Formation in Tanan Sag of Erlian Basin." Advanced Materials Research 962-965 (June 2014): 29–33. http://dx.doi.org/10.4028/www.scientific.net/amr.962-965.29.
Повний текст джерелаАнотація:
Erlian Basin was composed of many small faulted lacustrine basins in early Cretaceous period. Delta systems were developed and were the most important sandstone reservoir in the gentle slope of faulted lacustrine basins. The paper took an example of Tanan sag, which was one of the most representative faulted sags in Erlian Basin. This paper analyzed the depositional characteristics of nearshore subaqueous fan systems and fan deltas systems, based on core data, logging data and grain size probability curve. Fan delta-lacustrine deposition system and near shore turbidite fan-lacustrine deposition system were the most developed deposition system in the study area. The lake basin belonged to “narrow basin deep water” type. Mud stone of Deep lake facies and sand stone of fan delta facies in Aershan formation are the best lithology association which would be explored oil and gas in Tanan sag.
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Makar, P. A., J. Zhang, W. Gong, C. Stroud, D. Sills, K. L. Hayden, J. Brook, et al. "Mass tracking for chemical analysis: the causes of ozone formation in southern Ontario during BAQS-Met 2007." Atmospheric Chemistry and Physics Discussions 10, no. 6 (June 9, 2010): 14241–312. http://dx.doi.org/10.5194/acpd-10-14241-2010.
Повний текст джерелаАнотація:
Abstract. A three-level nested regional air pollution model has been used to study the processes leading to high ozone concentrations in the southern Great Lakes region of North America. The highest resolution simulations show that complex interactions between the lake breeze circulation and the synoptic flow lead to significant enhancements in the photochemical production and transport of ozone at the local scale. Significant improvements in model correlation with ozone observations are achieved in going to the highest spatial resolution. Mass tracking of individual model processes show that Lakes Erie and St. Clair frequently act as photochemical production regions, with average mid-day production rates of 6 to 8 ppbv per hour. Enhanced ozone levels are evident over these two lakes in 23-day-average surface ozone fields. Analysis of other model fields and aircraft measurements suggests that vertical recirculation enhances ozone levels over Lake St. Clair while strong subsidence enhances ozone over Lake Erie. The mass tracking of model transport shows that lake-breeze surface convergence zones combined with the synoptic flow can carry ozone and its precursors hundreds of kilometers from these source areas, in narrow, elongated features. Comparison with surface mesonet ozone observations confirm the presence, magnitude, and timing of these features, which create local ozone enhancements on the order of 20 ppbv above the regional ozone levels. High-resolution modelling is recommended in order to predict these local-scale features in operational air-quality forecasts.
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Samways, Kurt M., Peter R. Leavitt, Pierre Magnan, Marco A. Rodríguez, and Pedro R. Peres-Neto. "Convergent polymorphism between stream and lake habitats: the case of brook char." Canadian Journal of Fisheries and Aquatic Sciences 72, no. 9 (September 2015): 1406–14. http://dx.doi.org/10.1139/cjfas-2015-0116.
Повний текст джерелаАнотація:
Phenotypic variability represents an important factor allowing species to adapt to local environmental conditions, but mechanisms underlying such variation are incompletely understood. This study investigated whether habitat-specific demands on swimming performance or difference in trophic relationships in lakes (pelagic, littoral) and streams (riffle, pool) were significant predictors of phenotypic variation exhibited by brook char (Salvelinus fontinalis), the only fish in the study habitats. Specifically, we hypothesized that pelagic and riffle habitats would impose greater selective pressures associated with swimming, resulting in body morphologies that were dorsoventrally compressed, anterior–posteriorly elongated, and that exhibited a long, narrow caudal peduncle. Geometric morphometrics was applied in a quantitative analysis of body morphology among habitats, whereas stable isotope analysis was used to differentiate between food sources. Analyses revealed that while body morphology differed between lake and stream habitats, there was convergence between the pelagic and riffle habitats, as well as among littoral and riffle and pool environments. The littoral and pool habitats were thought to be more structurally complex, thereby selecting for increased maneuverability but lower sustained swimming and correspondingly deeper bodies with shorter, dorsoventrally expanded caudal peduncles. Carbon source and trophic position did not differ among habitats with a system, suggesting that feeding was not the main influence on morphological plasticity; however, fish in the stream were feeding at a higher trophic position than fish in the lake. These findings suggest that individual species may take advantage of morphological variation to better adapt local surroundings.
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Søe, Niels Emil, Aart Kroon, Bent Vad Odgaard, Holger Lykke-Andersen, and Søren Munch Kristiansen. "Bathymetric control of Holocene spit migration in a lacustrine environment." Holocene 28, no. 8 (May 3, 2018): 1245–54. http://dx.doi.org/10.1177/0959683618771498.
Повний текст джерелаАнотація:
Wave processes are well known for developing spit systems in large or elongated lakes by inducing longshore sediment transport for spit migration, while bathymetric interaction is less studied. In this study, we investigate the combined effects of wave processes, antecedent topography and lake level changes on the development of Holocene spit systems in the Danish lake Mossø. Wave climate prediction and a digital elevation model were used to provide a conceptual model for the development of the spits system, while optically stimulated luminescence (OSL) dating of spit sand and antecedent topography analyzed via boreholes and seismic survey data were used to evaluate effects on spit migration other than wave setting. We found that spit migration stagnated during the Holocene when reaching areas of deeper waters, but continued following shallowing after deep basin infilling with lacustrine sediments. During periods of bathymetrically induced stagnation of prominent spits, less stable or more slowly migrating spits became prominent in the development of the spit system. No clear effects on spit migration caused by lake level fluctuations could be demonstrated. However, such fluctuations may have been important for the stabilization of spits and subsequent development of a major barrier shoreline.
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Bergmaier, Philip T., Bart Geerts, Leah S. Campbell, and W. James Steenburgh. "The OWLeS IOP2b Lake-Effect Snowstorm: Dynamics of the Secondary Circulation." Monthly Weather Review 145, no. 7 (July 2017): 2437–59. http://dx.doi.org/10.1175/mwr-d-16-0462.1.
Повний текст джерелаАнотація:
Intense lake-effect snowfall results from a long-lake-axis-parallel (LLAP) precipitation band that often forms when the flow is parallel to the long axis of an elongated body of water, such as Lake Ontario. The intensity and persistence of the localized precipitation along the downwind shore and farther inland suggests the presence of a secondary circulation that helps organize such a band, and maintain it for some time as the circulation is advected inland. Unique airborne vertical-plane dual-Doppler radar data are used here to document this secondary circulation in a deep, well-organized LLAP band observed during intensive observing period (IOP) 2b of the Ontario Winter Lake-effect Systems (OWLeS) field campaign. The circulation, centered on a convective updraft, intensified toward the downwind shore and only gradually weakened inland. The question arises as to what sustains such a circulation in the vertical plane across the LLAP band. WRF Model simulations indicate that the primary LLAP band and other convergence zones observed over Lake Ontario during this IOP were initiated by relatively shallow airmass boundaries, resulting from a thermal contrast (i.e., land-breeze front) and differential surface roughness across the southern shoreline. Airborne radar data near the downwind shore of the lake indicate that the secondary circulation was much deeper than these shallow boundaries and was sustained primarily by rather symmetric solenoidal forcing, enhanced by latent heat release within the updraft region.
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Hainaut, Olivier R., Jan T. Kleyna, Karen J. Meech, Mark Boslough, Marco Micheli, Richard Wainscoat, Marielle Dela Cruz, Jacqueline V. Keane, Devendra K. Sahu, and Bhuwan C. Bhatt. "Disintegration of active asteroid P/2016 G1 (PANSTARRS)." Astronomy & Astrophysics 628 (August 2019): A48. http://dx.doi.org/10.1051/0004-6361/201935868.
Повний текст джерелаАнотація:
We report on the catastrophic disintegration of P/2016 G1 (PANSTARRS), an active asteroid, in April 2016. Deep images over three months show that the object is made up of a central concentration of fragments surrounded by an elongated coma, and presents previously unreported sharp arc-like and narrow linear features. The morphology and evolution of these characteristics independently point toward a brief event on 2016 March 6. The arc and the linear feature can be reproduced by large particles on a ring, moving at ~2.5 m s−1. The expansion of the ring defines a cone with a ~40° half-opening. We propose that the P/2016 G1 was hit by a small object which caused its (partial or total) disruption, and that the ring corresponds to large fragments ejected during the final stages of the crater formation.
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Miljutina, Maria A., Dmitry M. Miljutin, and Alexei V. Tchesunov. "SevenAcantholaimus(Chromadoridae: Nematoda) species from one deep-sea sediment sample (Angola Basin, south-east Atlantic)." Journal of the Marine Biological Association of the United Kingdom 93, no. 4 (July 19, 2012): 935–53. http://dx.doi.org/10.1017/s0025315412000860.
Повний текст джерелаАнотація:
The genusAcantholaimus(Chromadoridae: Nematoda) is one of the most species-rich deep-sea nematode genera. The descriptions of two new species and supplemental descriptions of five known species from the Angola Basin (south-east Atlantic Ocean) and a depth of about 5500 m are given.Acantholaimus formosussp. nov. is characterized by a spindle-shaped body with narrow elongated anterior end, the position of amphideal fovea on the apical tip of the body and by robust rugae and onchia.Acantholaimus skukinaesp. nov. is characterized by its cylindrical body shape; short outer labial, cephalic, cervical, and somatic setae; large amphideal fovea; the position of its amphideal fovea (situated relatively far from the head end); and relatively small onchia.Acantholaimus angustuswas previously found in the Peru Basin (central-eastern Pacific) and the Clarion–Clipperton Nodule Province (Equatorial Pacific), about 13,000 km apart from the nearest previous location of finding. The type location ofA. verscheldiis the Kenyan coast of the Indian Ocean. New specimens of this species were found about 8000 km apart from the type location.Acantholaimus akvavitus, A. iubilusandA. quintuswere previously found in different parts of the Atlantic and the Pacific.
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He, Cheng, and Quintin Rochfort. "Numerical Modelling Approaches for Assessing Improvements to the Flow Circulation in a Small Lake." Modelling and Simulation in Engineering 2011 (2011): 1–21. http://dx.doi.org/10.1155/2011/897618.
Повний текст джерелаАнотація:
Kamaniskeg Lake is a long, narrow, and deep small lake located in the northern part of Ontario, Canada. The goals of this paper were to examine various options to improve the water quality in the northern part of the lake by altering the local hydraulic flow conditions. Towards this end, a preliminary screening suggested that the flow circulation could be increased around a central island (Mask Island) in the northern part of the lake by opening up an existing causeway connecting the mainland and central island. Three-dimensional (3D) hydraulic and transport models were adopted in this paper to investigate the hydraulic conditions under various wind forces and causeway structures. The modelling results show that opening the causeway in a few places is unlikely to generate a large flow circulation around the central island. Full circulation only appears to be possible if the causeway is fully removed and a strong wind blows in a favourable direction. The possible reasons for existing water quality variations at the intake of a local WTP (water treatment plant) are also explored in the paper.
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Kettle, W. D., M. F. Moffett, and F. deNoyelles Jr. "Vertical Distribution of Zooplankton in an Experimentally Acidified Lake Containing a Metalimnetic Phytoplankton Peak." Canadian Journal of Fisheries and Aquatic Sciences 44, S1 (December 18, 1987): s91—s95. http://dx.doi.org/10.1139/f87-284.
Повний текст джерелаАнотація:
A large biomass of phytoplankton occurred as a narrow band in the metalimnion of a small Canadian Shield lake which had been undergoing experimental acidification. This community represented the maximum concentration of algal biomass in the lake and was composed of small phytoplankton species. The diurnal distribution of crustacean zooplankton was determined in relation to this potential food source. Cyclopoid nauplii, Cyclops bicuspidatus thomasi, and Daphnia catawba remained diurnally associated with the peak while other species were uniformly distributed throughout the water column. Those species which remained diurnally associated with the peak were exposed to the greatest food concentration in the lake and were also exposed to lower acid conditions than those in the upper waters. A deep-dwelling phytoplankton community may offer a refuge for some zooplankton species in acid lakes by providing a large food supply under less acidic conditions. The importance of sampling acid lakes through the entire water column is supported by these observations.
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Wagner, Bernd, Thomas Wilke, Alexander Francke, Christian Albrecht, Henrike Baumgarten, Adele Bertini, Nathalie Combourieu-Nebout, et al. "The environmental and evolutionary history of Lake Ohrid (FYROM/Albania): interim results from the SCOPSCO deep drilling project." Biogeosciences 14, no. 8 (April 20, 2017): 2033–54. http://dx.doi.org/10.5194/bg-14-2033-2017.
Повний текст джерелаАнотація:
Abstract. This study reviews and synthesises existing information generated within the SCOPSCO (Scientific Collaboration on Past Speciation Conditions in Lake Ohrid) deep drilling project. The four main aims of the project are to infer (i) the age and origin of Lake Ohrid (Former Yugoslav Republic of Macedonia/Republic of Albania), (ii) its regional seismotectonic history, (iii) volcanic activity and climate change in the central northern Mediterranean region, and (iv) the influence of major geological events on the evolution of its endemic species. The Ohrid basin formed by transtension during the Miocene, opened during the Pliocene and Pleistocene, and the lake established de novo in the still relatively narrow valley between 1.9 and 1.3 Ma. The lake history is recorded in a 584 m long sediment sequence, which was recovered within the framework of the International Continental Scientific Drilling Program (ICDP) from the central part (DEEP site) of the lake in spring 2013. To date, 54 tephra and cryptotephra horizons have been found in the upper 460 m of this sequence. Tephrochronology and tuning biogeochemical proxy data to orbital parameters revealed that the upper 247.8 m represent the last 637 kyr. The multi-proxy data set covering these 637 kyr indicates long-term variability. Some proxies show a change from generally cooler and wetter to drier and warmer glacial and interglacial periods around 300 ka. Short-term environmental change caused, for example, by tephra deposition or the climatic impact of millennial-scale Dansgaard–Oeschger and Heinrich events are superimposed on the long-term trends. Evolutionary studies on the extant fauna indicate that Lake Ohrid was not a refugial area for regional freshwater animals. This differs from the surrounding catchment, where the mountainous setting with relatively high water availability provided a refuge for temperate and montane trees during the relatively cold and dry glacial periods. Although Lake Ohrid experienced significant environmental change over the last 637 kyr, preliminary molecular data from extant microgastropod species do not indicate significant changes in diversification rate during this period. The reasons for this constant rate remain largely unknown, but a possible lack of environmentally induced extinction events in Lake Ohrid and/or the high resilience of the ecosystems may have played a role.
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Eyles, Nicholas, and John J. Clague. "Glaciolacustrine Sedimentation During Advance and Retreat of the Cordilleran Ice Sheet in Central British Colombia." Géographie physique et Quaternaire 45, no. 3 (December 13, 2007): 317–31. http://dx.doi.org/10.7202/032878ar.
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ABSTRACT Thick (400+ m) and well exposed sediment fills in the Fraser and Chilcotin river valleys of central British Columbia record contrasting glaciolacustrine environments of at least two glaciations. The oldest glaciolacustrine sequence comprises deformed gravel, sand, mud, and diamict fades deposited, in part, on stagnant ice trapped in deep narrow valleys at the end of the penultimate glaciation (Early Wisconsinan or older). Younger glaciolacustrine sequences date from the advance and retreat phases of the Late Wisconsinan Fraser Glaciation {ca. 25-10 ka) and infill a Middle Wisconsinan drainage system cut across older sediments. The Late Wisconsinan advance sequence is dominated by diamict (debris-flow) fades that pass upward into silts. The diamict fades consist largely of reworked older Pleistocene drift and poorly lithified Cretaceous and Tertiary sediments. They record the focusing of large volumes of sediment into one or more glacial lakes occupying deep narrow troughs. Weakly bedded silts in the upper part of the sequence may have been deposited when the lake(s) deepened as glaciers continued to advance and thicken over the study area. It is possible that some advance glaciolacustrine sediments accumulated in subglacial water bodies. Late Wisconsinan deglacial lake sediments form a relatively thin, discontinuous capping in the area and conform to classical notions of gladolacustrine sedimentation involving a seasonal or 'varved' regime. In contrast, no seasonal pattern of sedimentation can be identified in older sequences where the overriding influence on deposition has been the presence of steep subaqueous slopes, buried ice masses, and high sediment fluxes; these, in combination, caused near-continuous downslope movement and resedimentation.
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Chapron, E., P. Albéric, D. Jézéquel, W. Versteeg, J. L. Bourdier, and J. Sitbon. "Multidisciplinary characterisation of sedimentary processes in a recent maar lake (Lake Pavin, French Massif Central) and implication for natural hazards." Natural Hazards and Earth System Sciences 10, no. 9 (September 6, 2010): 1815–27. http://dx.doi.org/10.5194/nhess-10-1815-2010.
Повний текст джерелаАнотація:
Abstract. Sedimentation processes occurring in the most recent maar lake of the French Massif Central (Lake Pavin) are documented for the first time based on high resolution seismic reflection and multibeam bathymetric surveys and by piston coring and radiocarbon dating on a sediment depocentre developed on a narrow sub aquatic plateau. This new data set confirms the mid Holocene age of maar lake Pavin formation at 6970±60 yrs cal BP and highlights a wide range of gravity reworking phenomena affecting the basin. In particular, a slump deposit dated between AD 580–640 remoulded both mid-Holocene lacustrine sediments, terrestrial plant debris and some volcanic material from the northern crater inner walls. Between AD 1200 and AD 1300, a large slide scar mapped at 50 m depth also affected the southern edge of the sub aquatic plateau, suggesting that these gas-rich biogenic sediments (laminated diatomite) are poorly stable. Although several triggering mechanisms can be proposed for these prehistoric sub-aquatic mass wasting deposits in Lake Pavin, we argue that such large remobilisation of gas-rich sediments may affect the gas stability in deep waters of meromictic maar lakes. This study highlights the need to further document mass wasting processes in maar lakes and their impacts on the generation of waves, favouring the development of dangerous (and potentially deadly) limnic eruptions.
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Davidson-Arnott, Robin G. D., and Heather E. Conliffe Reid. "Sedimentary processes and the evolution of the distal bayside of Long Point, Lake Erie." Canadian Journal of Earth Sciences 31, no. 9 (September 1, 1994): 1461–73. http://dx.doi.org/10.1139/e94-129.
Повний текст джерелаАнотація:
Long Point spit, on the north shore of Lake Erie, is >40 km long and presently building into water that is >40 m deep. Annual sediment supply to the spit is estimated to be 1.0 × 106 m3∙a−1 and is derived from the erosion of cohesive bluffs along more than 90 km of shoreline to the west. The shoreline of the distal bayside consists of narrow barriers that connect the ends of dune ridges and enclose interdune ponds and swales. Unlike most barrier spits, the distal end shows little evidence of the formation of dune recurves, and the shoreline of the bayside, rather than fronting a protected bay, is exposed to waves generated by northeast winds blowing over a fetch >100 km. Results of wave refraction analysis indicate that because of the great depth of water at the tip, there is almost no refraction of the dominant westerly and southwesterly waves around the distal end, thus inhibiting the formation of recurves. Net sediment transport on the distal bayside is towards the distal end of the spit. The result is the development of a narrow spit platform extending the spit directly into the deepest part of Lake Erie. All sediment reaching the distal end along the exposed south shore is transported onto this platform and none reaches the distal bayside.The negative sediment budget on the distal bayside results in transgression of the shoreline through truncation of the dune ridges, and overwash and breaching of the small barriers. Historical aerial photographs show that most of the overwash and breaching occurs during periods of long-term high lake levels, with the barriers being rebuilt landward of their former position during the following periods of lower lake levels. Progradation of the south shore at the distal end is thus partly counterbalanced by the transgression of the bayside.
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Ali, A., J. Pfleiderer, and W. Saurer. "Narrow band CCD imaging of four PNe." Symposium - International Astronomical Union 180 (1997): 204. http://dx.doi.org/10.1017/s0074180900130281.
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We present first results of a project to construct and study spatio-kinematical models of selected Planetary Nebulae (PNe). Deep monochromatic CCD images of A8, A4, M2-55, and J-320 were made with the Calar Alto 2.2m telescope and the two interference filters 5005/90 and 6574/104 for the [O III] and Hα+[N II] emission lines. The images were corrected for bias and dark, and flatfielded using MIDAS software, and also corrected for atmospheric extinction to derive the total flux in each emission line. The observed parameters are summarized in Table 1. – A8 (PNG167.0–00.9) has a very symmetric, round appearance with large diameter. The Hα+[N II] image clearly shows a round, limb-brightened ring which is less apparent in the [O III] image. Due to its appearance we can classify it as a late round type according to Balick (1987). −M2-55 (PN G116.2+08.5) has a box-like, quadratic and highly structured inner part (slightly more roundish in [O III]), with four maxima at the corners. The faint outer parts seem to consist of two ovals that are perpendicular to each other. Together, they again resemble a square tilted 45° against the inner one. The Hα+[N II] image is larger than [O III]: The square (distance of maxima) by some 20 percent, the faint ovals by about 10 percent. We can classify this PN as a middle elliptical type. – A4 (PNG144.3–15.5) is a spherical shell, with some definite structure in the brightest parts. This structure forms roughly a ring halfway between the center and the rim. A4 can be classified as an early round type. Both images are quite similar, the Hα+ [N II] maximum lying slightly, about 20 percent, farther from the center. In the very faint outer regions, the [O III]/(Hα+[N II]) ratio seems to increase by a factor of about 5 above the average which is otherwise constant within 10 percent over the whole image. -J-320 (PNG190.3–17.7) is elongated, with one maximum on the main axis, slightly off-center. The Hα+[N II] image has an interesting structure which is not present in [O III]: Two stripes of decreased intensity that are roughly parallel to and on both sides of the main axis. At present, we have no explanation for this feature. J-320 has ansae (small knots found in pairs on opposite sides and at equal distance from the nucleus) usually seen best in the light of low-ionization emission lines. Balick (1987) classified this PN as early type butterfly.
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Eisenback, Jonathan, and João Charchar. "Meloidogyne brasilensis n. sp. (Nematoda: Meloidogynidae), a root-knot nematode parasitising tomato cv. Rossol in Brazil." Nematology 4, no. 5 (2002): 629–43. http://dx.doi.org/10.1163/15685410260438926.
Повний текст джерелаАнотація:
AbstractMeloidogyne brasilensis n. sp., Londrina and Brasilia populations, is described and illustrated from specimens from tomato cv. Rossol and pea cv. Mikado, respectively, in Brazil. Characteristically, the perineal pattern is elongated to ovoid with a flattened to very high, squarish dorsal arch with widely spaced, coarse striae. The lateral fields may have wing-like striae on one or both sides. The female stylet is 14 μm long with narrow and elongated knobs that are distinctly set-off from the shaft. The excretory pore is variable in location, but generally opens near the anterior portion of the median bulb about 50 μm from the head end. The male is 1.89 mm long and has a high head cap that slopes posteriorly. The labial disc is separated from the medial lips by a deep, rounded groove. The delicate stylet of the male is 23 μm long and has small, rounded knobs that are distinctly set-off from the shaft which has numerous small, rounded projections. Mean second-stage juvenile length is 434 μm. The juvenile head cap is highly elevated, the medial lips are crescent-shaped and unequal in size, and the head region is not annulated. The stylet is 11 μm long and has small, rounded, posteriorly sloping knobs. The tail is 53 μm long; it is marked with large, irregular annules and ends in a bluntly rounded tip. The hyaline tail terminus is short (13 μm). Reproduction occurred on NC95 tobacco, tomato, pea, and bean, whereas pepper, watermelon, peanut, cotton, corn, and soybean were not hosts.
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Heslop, J. K., K. M. Walter Anthony, A. Sepulveda-Jauregui, K. Martinez-Cruz, A. Bondurant, G. Grosse, and M. C. Jones. "Thermokarst lake methanogenesis along a complete talik profile." Biogeosciences 12, no. 14 (July 24, 2015): 4317–31. http://dx.doi.org/10.5194/bg-12-4317-2015.
Повний текст джерелаАнотація:
Abstract. Thermokarst (thaw) lakes emit methane (CH4) to the atmosphere formed from thawed permafrost organic matter (OM), but the relative magnitude of CH4 production in surface lake sediments vs. deeper thawed permafrost horizons is not well understood. We assessed anaerobic CH4 production potentials from various depths along a 590 cm long lake sediment core that captured the entire sediment package of the talik (thaw bulb) beneath the center of an interior Alaska thermokarst lake, Vault Lake, and the top 40 cm of thawing permafrost beneath the talik. We also studied the adjacent Vault Creek permafrost tunnel that extends through ice-rich yedoma permafrost soils surrounding the lake and into underlying gravel. Our results showed CH4 production potentials were highest in the organic-rich surface lake sediments, which were 151 cm thick (mean ± SD: 5.95 ± 1.67 μg C–CH4 g dw−1 d−1; 125.9 ± 36.2 μg C–CH4 g C−1org d−1). High CH4 production potentials were also observed in recently thawed permafrost (1.18 ± 0.61 μg C–CH4g dw−1 d−1; 59.60± 51.5 μg C–CH4 g C−1org d−1) at the bottom of the talik, but the narrow thicknesses (43 cm) of this horizon limited its overall contribution to total sediment column CH4 production in the core. Lower rates of CH4 production were observed in sediment horizons representing permafrost that has been thawing in the talik for a longer period of time. No CH4 production was observed in samples obtained from the permafrost tunnel, a non-lake environment. Our findings imply that CH4 production is highly variable in thermokarst lake systems and that both modern OM supplied to surface sediments and ancient OM supplied to both surface and deep lake sediments by in situ thaw and shore erosion of yedoma permafrost are important to lake CH4 production.
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Heslop, J. K., K. M. Walter Anthony, A. Sepulveda-Jauregui, K. Martinez-Cruz, A. Bondurant, G. Grosse, and M. C. Jones. "Thermokarst-lake methanogenesis along a complete talik profile." Biogeosciences Discussions 12, no. 6 (March 24, 2015): 4865–905. http://dx.doi.org/10.5194/bgd-12-4865-2015.
Повний текст джерелаАнотація:
Abstract. Thermokarst (thaw) lakes emit methane (CH4) to the atmosphere formed from thawed permafrost organic matter (OM), but the relative magnitude of CH4 production in surface lake sediments vs. deeper thawed permafrost horizons is not well understood. We assessed anaerobic CH4 production potentials from various depths along a 590 cm long lake sediment core that captured the entire sediment package of the talik (thaw bulb) beneath the center of an interior Alaska thermokarst lake, Vault Lake, and the top 40 cm of thawing permafrost beneath the talik. We also studied the adjacent Vault Creek permafrost tunnel that extends through ice-rich yedoma permafrost soils surrounding the lake and into underlying gravel. Our results showed CH4 production potentials were highest in the organic-rich surface lake sediments, which were 151 cm thick (mean ± SD 5.95 ± 1.67 μg C-CH4 g dw−1 d−1; 125.9± 36.2 μg C-CH4 g C−1org d−1). High CH4 production potentials were also observed in recently-thawed permafrost (1.18± 0.61 μg C-CH4g dw−1 d−1; 59.60± 51.5 μg C-CH4 g C−1org d−1) at the bottom of the talik, but the narrow thicknesses (43 cm) of this horizon limited its overall contribution to total sediment column CH4 production in the core. Lower rates of CH4 production were observed in sediment horizons representing permafrost that has been thawed in the talik for longer periods of time. No CH4 production was observed in samples obtained from the permafrost tunnel, a non-lake environment. Our findings imply that CH4 production is highly variable in thermokarst-lake systems and that both modern OM supplied to surface sediments and ancient OM supplied to both surface and deep lake sediments by in situ thaw as well as shore erosion of yedoma permafrost are important to lake CH4 production.
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Bergmaier, Philip T., and Bart Geerts. "LLAP Band Structure and Intense Lake-Effect Snowfall Downwind of Lake Ontario: Insights from the OWLeS 7–9 January 2014 Event." Journal of Applied Meteorology and Climatology 59, no. 10 (October 1, 2020): 1691–715. http://dx.doi.org/10.1175/jamc-d-19-0288.1.
Повний текст джерелаАнотація:
AbstractModeling and observational studies stemming from the 2013–14 Ontario Winter Lake-Effect Systems (OWLeS) field campaign have yielded much insight into the structure and development of long-lake-axis-parallel (LLAP) lake-effect systems over Lake Ontario. This study uses airborne single- and dual-Doppler radar data obtained during two University of Wyoming King Air flights, as well as a high-resolution numerical model simulation, to examine and contrast two distinctly different LLAP band structures observed within a highly persistent lake-effect system on 7–9 January 2014. On 7 January, a very cold air mass accompanied by strong westerly winds and weak capping aloft resulted in a deep, intense LLAP band that produced heavy snowfall well inland. In contrast, weaker winds, weaker surface heat fluxes, and stronger capping aloft resulted in a weaker LLAP band on 9 January. This band was blocked along the downwind shore and produced only light snowfall closer to the shoreline. Although the two structures examined here represent opposite ends of a spectrum of LLAP bands, both cases reveal a well-organized mesoscale secondary circulation composed of two counterrotating horizontal vortices positioned on either side of a narrow updraft within the band. In both cases, this circulation traces back to a shallow, baroclinic land-breeze front originating along a bulge in the lake’s southern shoreline. As the band extends downstream and the low-level baroclinity weakens, buoyancy increases within the band—driven in part by cloud latent heating—leading to band intensification and a deeper, stronger, and more symmetric secondary circulation over the lake.
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Gelda, Rakesh K., Alexandra T. King, Steven W. Effler, Seth A. Schweitzer, and Edwin A. Cowen. "Testing and application of a two-dimensional hydrothermal/transport model for a long, deep, and narrow lake with moderate Burger number." Inland Waters 5, no. 4 (October 1, 2015): 387–402. http://dx.doi.org/10.5268/iw-5.4.804.
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Brown, Rodger A., Thomas A. Niziol, Norman R. Donaldson, Paul I. Joe, and Vincent T. Wood. "Improved Detection Using Negative Elevation Angles for Mountaintop WSR-88Ds. Part III: Simulations of Shallow Convective Activity over and around Lake Ontario." Weather and Forecasting 22, no. 4 (August 1, 2007): 839–52. http://dx.doi.org/10.1175/waf1019.1.
Повний текст джерелаАнотація:
Abstract During the winter, lake-effect snowstorms that form over Lake Ontario represent a significant weather hazard for the populace around the lake. These storms, which typically are only 2 km deep, frequently can produce narrow swaths (20–50 km wide) of heavy snowfall (2–5 cm h−1 or more) that extend 50–75 km inland over populated areas. Subtle changes in the low-altitude flow direction can mean the difference between accumulations that last for 1–2 h and accumulations that last 24 h or more at a given location. Therefore, it is vital that radars surrounding the lake are able to detect the presence and strength of these shallow storms. Starting in 2002, the Canadian operational radars on the northern side of the lake at King City, Ontario, and Franktown, Ontario, began using elevation angles of as low as −0.1° and 0.0°, respectively, during the winter to more accurately estimate snowfall rates at the surface. Meanwhile, Weather Surveillance Radars-1988 Doppler in New York State on the southern and eastern sides of the lake—Buffalo (KBUF), Binghamton (KBGM), and Montague (KTYX)—all operate at 0.5° and above. KTYX is located on a plateau that overlooks the lake from the east at a height of 0.5 km. With its upward-pointing radar beams, KTYX’s detection of shallow lake-effect snowstorms is limited to the eastern quarter of the lake and surrounding terrain. The purpose of this paper is to show—through simulations—the dramatic increase in snowstorm coverage that would be possible if KTYX were able to scan downward toward the lake’s surface. Furthermore, if KBUF and KBGM were to scan as low as 0.2°, detection of at least the upper portions of lake-effect storms over Lake Ontario and all of the surrounding land area by the five radars would be complete. Overlake coverage in the lower half (0–1 km) of the typical lake-effect snowstorm would increase from about 40% to about 85%, resulting in better estimates of snowfall rates in landfalling snowbands over a much broader area.
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Messyasz, Beata, and Ewa Treska. "Benthic Diatoms as Valuable Indicators of Anthropogenic Eutrophication in Biomonitoring of Ribbon Lake." Ecological Chemistry and Engineering S 26, no. 4 (December 1, 2019): 709–26. http://dx.doi.org/10.1515/eces-2019-0014.
Повний текст джерелаАнотація:
Abstract In Europe the monitoring of lakes with regard to benthic diatoms is still conducted in line with the European Water Framework Directive. Ribbon lakes are a special case as extremely steep slopes of the lake basin cause their littoral zone to be narrow. The Durowskie ribbon lake was chosen as a model for the assessment of the ecological status of waters based on its Diatom Index. Given its use in recreation, it is under heavy anthropogenic pressure. Physicochemical and biological parameters were monitored in the peak of the vegetational season (July, August) between 2010 and 2018 at 12 varied littoral sites across the full length of the shoreline. This long-term analysis of the Diatom Index, despite showing an improvement in the quality of water, demonstrated the ecological state of Lake Durowskie to be weak (southern, deep part) to moderate (north, shallow part). The taxonomic structure of diatoms (referral and indicator taxa) in phytobenthos communities allowed to show the changes in physicochemical parameters of the environment such as pH, oxygen dissolved in water and its trophic status. Research results are shown in relation to the anthropogenic changes to the lake’s direct catchment area and the results of the physicochemical monitoring of waters.
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Migurskiy, F. A. "GEODYNAMICS OF THE CALEDONIAN BAIKAL-PATOM FOLDED REGION AND ITS INFLUENCE ON THE PETROLEUM POTENTIAL OF THE PRE-PATOM PERICRATONIC TROUGH." Geology and mineral resources of Siberia, no. 3 (October 2022): 3–16. http://dx.doi.org/10.20403/2078-0575-2022-3-3-16.
Повний текст джерелаАнотація:
A three-dimensional geodynamical model of the Baikal-Patom folded region and associated Pre-Patom pericratonic trough was developed using materials obtained in recent years from deep seismic observations of the CDPM along the Vitim River, results of several field seasons, involving data on the deep structure of folded belts of the world as well as the results of physical modeling. Its main characteristics are thrust-underthrust character, numerous, to varying degrees reworked duplex pileups, the Caledonian age, a very high degree of denudation in the southern part, which destroyed the upper allochthonous thrust plates in the area of Lake Baikal and exposed narrow, deep, root zones, extensive development of metagenetic processes that formed tectonoclastic strata. Analogues of hydrocarbon deposits in the southern part of the pericratonic area, including such giants as the Kovyktinskoye gas condensate field, can be found further north in autochthonous basal terrigenous Vendian productive horizons under allochthonous plates. Lateral movements of large tectonic plates, fluid migration over a distance of over 200 km allow researchers to confirm the high oil-and-gas prospects of the auto- and allochthonous intervals of the sedimentary cover of the Pre-Patom petroleum area.
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Jiang, Chaowei, Hong Zhang, Chao Wang, Ji Ge, and Fan Wu. "Water Surface Mapping from Sentinel-1 Imagery Based on Attention-UNet3+: A Case Study of Poyang Lake Region." Remote Sensing 14, no. 19 (September 21, 2022): 4708. http://dx.doi.org/10.3390/rs14194708.
Повний текст джерелаАнотація:
The mapping of water surfaces is important for water resource and flood monitoring. Synthetic Aperture Radar (SAR) images can be used to monitor water bodies and detect floods over large areas. To address the problem of low identification accuracy in different time phases and different scales of water area, a water surface mapping method based on Attention-UNet3+ with SAR images is proposed in this paper. In the model, full-scale skip connections are introduced for combining feature maps from different scales and improving the accuracy of narrow water identification; the spatial attention module is used to obtain the importance of each connected feature, which can reduce the number of false alarms caused by speckle noise and water shadows in SAR data; the deep supervision module is used to learn hierarchical representative features from comprehensive aggregated feature maps to provide the periodic output capability of the model and meet the needs of rapid and large-scale water identification. The effectiveness of Attention-UNet3+ is verified by experiments in the Poyang Lake region with Sentinel-1 SAR images. The results show that the proposed Attention-UNet3+ outperforms the conventional threshold segmentation and deep learning models such as UNet, Deepvlabv3+, and SegNet, with an average IOU/Kappa value of 0.9502/0.9698. Multitemporal Sentinel-1 images in 2021 covering Poyang Lake are used for time series water surface mapping with the proposed method, and it is found that the detected water area of Poyang Lake has a good correlation with the corresponding water level values at observation stations. The Pearson coefficients are about 0.96. The above results indicate that the proposed method achieves good water surface mapping performance.
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Vrbanac, Boris, Josipa Velić, and Tomislav Malvić. "Sedimentation of deep-water turbidites in the SW part of the Pannonian Basin." Geologica Carpathica 61, no. 1 (February 1, 2010): 55–69. http://dx.doi.org/10.2478/v10096-010-0001-8.
Повний текст джерелаАнотація:
Sedimentation of deep-water turbidites in the SW part of the Pannonian BasinThe Sava Depression and the Bjelovar Subdepression belong to the SW margin of the Pannonian Basin System, which was part of the Central Paratethys during the Pannonian period. Upper Pannonian deposits of the Ivanic-Grad Formation in the Sava Depression include several lithostratigraphic members such as Iva and Okoli Sandstone Member or their lateral equivalents, the Zagreb Member and Lipovac Marlstone Member. Their total thickness in the deepest part of the Sava Depression reaches up to 800 meters, while it is 100-200 meters in the margins of the depression. Deposits in the depression are composed of 4 facies. In the period of turbiditic activities these facies are primarily sedimented as different sandstone bodies. In the Bjelovar Subdepression, two lithostratigraphic members (lateral equivalent) were analysed, the Zagreb Member and Okoli Sandstone Member. The thickness of the Bjelovar Subdepression ranges from 50 meters along the S and SE margins to more than 350 meters along the E margin. Generally, detritus in the north-west part of the analysed area originated from a single source, the Eastern Alps, as demonstrated by sedimentological and physical properties, the geometry of the sandstone body and the fossil content. This clastic material was found to be dispersed throughout the elongated and relatively narrow Sava Depression and in the smaller Bjelovar Subdepression. Sedimentation primarily occurred in up to 200 meters water depth and was strongly influenced by the sub-aqueous paleorelief, which determined the direction of the flow of turbidity currents and sandstone body geometries. The main stream with medium- and fine-grained material was separated by two independent turbiditic flows from N-NW to the SE-E. Variability in the thickness of sandstone bodies is the result of differences in subsidence and cycles of progradation and retrogradation of turbidite fans.
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Hanson, John Mark, William C. Mackay, and E. E. Prepas. "Population size, growth, and production of a unionid clam, Anodonta grandis simpsoniana, in a small, deep Boreal Forest lake in central Alberta." Canadian Journal of Zoology 66, no. 1 (January 1, 1988): 247–53. http://dx.doi.org/10.1139/z88-035.
Повний текст джерелаАнотація:
Unionid clams were sampled quantitatively by divers searching quadrats and by dredging in Narrow Lake, central Alberta. The mean density and biomass of Anodonta grandis simpsoniana Lea (aged ≥2 years) on the area of the littoral zone available to clams (80%) were 15/m2 and 132 g/m2 (live weight), respectively. The mean length at 5 years of age was 49 mm and only increased to 69 mm by 11 years of age. Variation in length at annulus was high. Years of small growth increments (1982 and 1983) coincided with years of poor juvenile recruitment. Production/biomass ratios were highest for clams of 2 and 3 years of age, but the amount of biomass produced was greatest for clams of 5–8 years of age. The overall production/biomass ratio (live weight) was 0.25 and varied with annual differences in growth.
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Liu, Honghan, Zhen Wang, Weiwei Wu, Chenhong Li, Jiawei Zhang, Yahui Gao, Xuesong Li, et al. "A new marine epipsammic diatom species, Ambo dajingensis sp. nov. (Bacillariophyceae), from the coast of Southeast China." PhytoKeys 210 (September 28, 2022): 23–34. http://dx.doi.org/10.3897/phytokeys.210.90876.
Повний текст джерелаАнотація:
Ambo dajingensis HH Liu, Z Wang, YH Gao & CP Chen, sp. nov. is described as a new species in samples collected from sand grains at Dajing Beach, Ningde City, Fujian Province, China. Morphological details of the new species with respect to valve shape, size and valve ultrastructure are presented based on light microscopy (LM) and scanning electron microscopy (SEM). The main features of Ambo dajingensis under a light microscope are elongated elliptic valves with rounded apices, two internal costae on the valve and rectangular in girdle views. SEM observation showed that externally, the frustules are comprised of two valves with a relatively deep mantle and a transition between the valve faces. Small, flabelliform spines are present along the valve margin. Internally, the valves are divided into three sectors by robust costae, which penetrate the whole valve lumen and are thickest at the mantle interior and thinner toward the center. The sternum is narrow and linear, visible only in the valve apex, set off by costae. The striae are comprised of small, round areolae and they are parallel in the middle to slightly radiate at the apices. The new species is compared with other species in the genus Ambo.
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Djerić, D., and D. Savić. "Anatomical characteristics of the fossula fenestrae vestibuli." Journal of Laryngology & Otology 101, no. 5 (May 1987): 426–31. http://dx.doi.org/10.1017/s002221510010194x.
Повний текст джерелаАнотація:
AbstractAnatomical characteristics of the fossula fenestrae vestibuli were tested and analysed precisely on 200 samples of temporal bones. The fossula is usually ovoid and shallow but can be, exceptionally, elongated, narrow and deep. It is surrounded by four walls. In 45.5 per cent of cases the upper wall is formed only by the facial canal and in 54.5 per cent of cases a bony lamella is found beneath the facial canal; the promontory forms the lower wall; the front wall is formed by the bony lamella and part of the processus cochleariformis; the back wall is clearly defined in only 22.8 per cent of cases and is formed by the bony lamella of the medial wall of the tympanic cavity. In 13.2 per cent of cases the floor of the fossula partially covers the prominence of the facial canal and in two per cent the eminentia pyramidalis. Bony recesses in this region occur fairly frequently: sinus subfacialis in 60 per cent, sinus retrofenestralis in 77.2 per cent, and sinus subrostralis in 25 per cent of the cases. These anatomical variations can influence the result of surgical intervention.
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Ma, Kun, Xiaolan Tang, Yujie Ren, and Yiwen Wang. "Research on the Spatial Pattern Characteristics of the Taihu Lake “Dock Village” Based on Microclimate: A Case Study of Tangli Village." Sustainability 11, no. 2 (January 12, 2019): 368. http://dx.doi.org/10.3390/su11020368.
Повний текст джерелаАнотація:
“Dock Village” terrain is, as its name implies, a region that contains settlements reminiscent of docks, in terms of their elongated shape, their outward upward tilt, and their location in the center of low, wide valleys. Dock village terrain features deep, fertile soil suitable for farming. Taihu Lake contains a number of classic examples of dock villages. Dock villages are relatively independent and hidden, characteristics that not only play a role in security and defense, but also, more importantly, are associated with enhanced climate adaptability, a relative lack of cold weather, and equable levels of heat and humidity. The dock village reflects the wisdom and distillation of traditional Chinese ecological practices and is highly valued as a research topic. Based on microclimate theory and ENVI-met software, four microclimate indices, namely, air temperature, wind speed, wind direction, and relative humidity, were simulated and analyzed in this study. The correlation between spatial characteristics and microclimate was studied from four perspectives: plane space, cross-section space, vertical section space, and linear development space. This research summarizes the historical context and evolution of the dock village spatial form in the construction of contemporary human settlements. It also provides scientific suggestions for the protection and sustainable development of ancient villages.
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Simon, Thomas P., and Joe T. Vondruska. "Larval identification of the ruffe, Gymnocephalus cernuus (Linnaeus) (Percidae: Percini), in the St. Louis River Estuary, Lake Superior drainage basin, Minnesota." Canadian Journal of Zoology 69, no. 2 (February 1, 1991): 436–42. http://dx.doi.org/10.1139/z91-068.
Повний текст джерелаАнотація:
A reproducing population of the Eurasian percid Gymnocephalus cernuus was discovered in the St. Louis River, Lake Superior basin, near Duluth, Minnesota. This study is the first documented evidence of the species occurrence and reproduction in North America. Larvae resemble typical percids and are described with emphasis on meristic, morphometric, and pigmentary characters. Ruffe are distinguished from all native North American percids by the presence of a slightly concave head becoming attenuated at larger length intervals, a pointed snout with teeth on the maxillary and premaxillary by the time a length of 11 mm is reached, a large dorsally pigmented swim bladder, a serrated preopercle, and few postanal myomeres (usually 18–22). In particular, ruffe superficially resemble johnny darters as yolk-sac larvae, and walleye, yellow perch, and logperch at lengths greater than 10 mm, but can be distinguished by the previously mentioned characteristics and a deep shoulder depth and a narrow caudal peduncle.
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Kazmin, Sergey P. "REMOTE SENSING OF TAPE BORES IN THE ALTAI KRAI UNDER ANTHROPOGENIC-TECHNOGENIC IMPACT." Interexpo GEO-Siberia 4, no. 2 (May 21, 2021): 75–79. http://dx.doi.org/10.33764/2618-981x-2021-4-2-75-79.
Повний текст джерелаАнотація:
The relief and its geological formations are the primary prerequisite for the study of the biological component of the natural environment and rational use of natural resources. The geological and geomorphological conditions of the territory have a very deep and diverse influence on the structure of other components of the landscape. In the south-east of Western Siberia, in the Ob-Irtysh interfluve, there are ribbon forests-narrow, strongly elongated strips of light coniferous forest with a width of 5 to 10 km. The forest-forming breed of hog is scots pine. In the conditions of increasing anthropogenic pressure in the region, the natural environment is deteriorating. The main provisions that are justified in the article are based on the author's long-term research and materials of remote sensing of ribbon bores of the Altai Territory. Real estimates of the state and forecast of changes in the natural environment, including anthropogenic influence, can be obtained only on the basis of strictly scientific data and conclusions about the formation of the landscape of the studied region and the components of the environment. The digital model of the Ecological and Geomorphological map of the belt forests and the annual use of the latest satellite images will allow monitoring the changes in the main contours of the terrain.
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Couvelard, Xavier, Patrick Marchesiello, Lionel Gourdeau, and Jerome Lefèvre. "Barotropic Zonal Jets Induced by Islands in the Southwest Pacific." Journal of Physical Oceanography 38, no. 10 (October 1, 2008): 2185–204. http://dx.doi.org/10.1175/2008jpo3903.1.
Повний текст джерелаАнотація:
Abstract The oceanic circulation entering the tropical southwest Pacific (SWP) is dominated by the broad westward flow of the South Equatorial Current (SEC), which is forced by the trade winds. It has been argued that the numerous islands of the SWP are able to restructure the SEC into a series of deep and narrow zonal jets, which control important pathways connecting equatorial and extraequatorial signals. The primary objective of this paper is to improve the understanding of the structure and dynamics of SWP zonal jets, giving special attention to topographic effects. This study is based on the use of a high-resolution regional oceanic model, whose solution is compared with observations, as well as with solutions from global models and the Sverdrup relation. The model used here indicates that the regional topography drives a general equatorward shift of the SEC, which is beneficial to the North Fiji, North Vanuatu, and North Caledonian jets. A depth-integrated vorticity budget shows that this topographic effect is considerably attenuated by baroclinicity and advection processes, but not to the point of total compensation as often admitted for the interior ocean. The effect of nonlinear advection is to allow flow rectification of the jets fluctuations, taking the form of zonally elongated dipole circulations in the leeward side of the islands.
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Brandon, Mark, Richard Hodgkins, Helgi Björnsson, and Jón Ólafsson. "Multiple melt plumes observed at the Breiðamerkurjökull ice face in the upper waters of Jökulsárlón lagoon, Iceland." Annals of Glaciology 58, no. 74 (April 2017): 131–43. http://dx.doi.org/10.1017/aog.2017.10.
Повний текст джерелаАнотація:
ABSTRACT Breiðamerkurjökull flows from the Vatnajökull ice cap and calves into the Jökulsárlón proglacial lagoon. The lagoon is connected to the North Atlantic Ocean through a 6 m deep narrow channel. Four hydrographic surveys in spring 2012, and a 2011 4-month long temperature and salinity time series of lagoon inflow show that the lake has significantly changed since 1976. Warm saline ocean water enters each tidal cycle and descends below the maximum sampled depths. The lagoon has a surface layer of ice melt, freshwater and Atlantic derived water. Beneath 10 m depth an advective/diffusive balance is responsible for determining the temperature and salinity of the lagoon waters down to ~90 m. To maintain the observed hydrographic structure, we calculate an upwelling of deep water of ~0.2 m d−1. A survey within 30 m of Breiðamerkurjökull showed that the warmest and most saline waters sampled within the lagoon below 10 m depth were adjacent to the glacier face, along with multiple interleaved warm and cold layers. A heat and salt balance model shows that submarine melting along the ice face generates multiple meltwater plumes that are mixed and diluted within 200 m of the ice face.
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Chen, Fang. "Comparing Methods for Segmenting Supra-Glacial Lakes and Surface Features in the Mount Everest Region of the Himalayas Using Chinese GaoFen-3 SAR Images." Remote Sensing 13, no. 13 (June 22, 2021): 2429. http://dx.doi.org/10.3390/rs13132429.
Повний текст джерелаАнотація:
Glaciers and numerous glacial lakes that are produced by glacier melting are key indicators of climate change. Often overlooked, supra-glacial lakes develop in the melting area in the low-lying part of a glacier and appear to be highly variable in their size, shape, and location. The lifespan of these lakes is thought to be quite transient, since the lakes may be completely filled by water and burst out within several weeks. Changes in supra-glacial lake outlines and other surface features such as supra-glacial rivers and crevasses on the glaciers are useful indicators for the direct monitoring of glacier changes. Synthetic aperture radar (SAR) is not affected by weather and climate, and is an effective tool for study of glaciated areas. The development of the Chinese GaoFen-3 (GF-3) SAR, which has high spatial and temporal resolution and high-precision observation performance, has made it possible to obtain dynamic information about glaciers in more detail. In this paper, the classical Canny operator, the variational B-spline level-set method, and U-Net-based deep-learning model were applied and compared to extract glacial lake outlines and other surface features using different modes and Chinese GF-3 SAR imagery in the Mount Everest Region of the Himalayas. Particularly, the U-Net-based deep-learning method, which was independent of auxiliary data and had a high degree of automation, was used for the first time in this context. The experimental results showed that the U-Net-based deep-learning model worked best in the segmentation of supra-glacial lakes in terms of accuracy (Precision = 98.45% and Recall = 95.82%) and segmentation efficiency, and was good at detecting small, elongated, and ice-covered supra-glacial lakes. We also found that it was useful for accurately identifying the location of supra-glacial streams and ice crevasses on glaciers, and quantifying their width. Finally, based on the time series of the mapping results, the spatial characteristics and temporal evolution of these features over the glaciers were comprehensively analyzed. Overall, this study presents a novel approach to improve the detection accuracy of glacier elements that could be leveraged for dynamic monitoring in future research.
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FALTÝNKOVÁ, A., E. T. VALTONEN, and A. KARVONEN. "Spatial and temporal structure of the trematode component community inValvata macrostoma(Gastropoda, Prosobranchia)." Parasitology 135, no. 14 (November 10, 2008): 1691–99. http://dx.doi.org/10.1017/s0031182008005027.
Повний текст джерелаАнотація:
SUMMARYWe conducted the first comprehensive study on the spatiotemporal structure of trematode communities in the large-mouthed valve snail,Valvata macrostoma. A total of 1103 snails were examined monthly between May and October 2007 from Lake Konnevesi, Central Finland, from a shallow (1–2 m deep) and an offshore site (5–6 m deep), located ca. 50–70 m apart. Snails were infected by 10 trematode species. The species composition and prevalence were strikingly different between the sites with high species diversity in the shallow site (all 10 species; total prevalence of sporocysts/rediae 12·1%, metacercariae 55·4%) compared to the deeper site (3 species; prevalence 15·0% and 1·9%, respectively). This difference persisted throughout our study and is probably related to the spatial distribution of bird definitive hosts, whereas the seasonal parasite dynamics are likely to be affected by changes in the age-structure of the snail population. The probability of sporocyst infections increased with snail size, but no such trend was observed in redial or metacercarial infections which decreased with host size. Our results show that generally well-described spatiotemporal differences in trematode infection of molluscs can emerge in very narrow spatial and temporal scales, which emphasizes the importance of these factors in community studies.
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Doda, Tomy, Cintia L. Ramón, Hugo N. Ulloa, Alfred Wüest, and Damien Bouffard. "Seasonality of density currents induced by differential cooling." Hydrology and Earth System Sciences 26, no. 2 (January 24, 2022): 331–53. http://dx.doi.org/10.5194/hess-26-331-2022.
Повний текст джерелаАнотація:
Abstract. When lakes experience surface cooling, the shallow littoral region cools faster than the deep pelagic waters. The lateral density gradient resulting from this differential cooling can trigger a cold downslope density current that intrudes at the base of the mixed layer during stratified conditions. This process is known as a thermal siphon (TS). TSs flush the littoral region and increase water exchange between nearshore and pelagic zones; thus, they may potentially impact the lake ecosystem. Past observations of TSs in lakes are limited to specific cooling events. Here, we focus on the seasonality of TS-induced lateral transport and investigate how seasonally varying forcing conditions control the occurrence and intensity of TSs. This research interprets 1-year-long TS observations from Rotsee (Switzerland), a small wind-sheltered temperate lake with an elongated shallow region. We demonstrate that TSs occur for more than 50 % of the days from late summer to winter and efficiently flush the littoral region within ∼10 h. We further quantify the occurrence, intensity, and timing of TSs over seasonal timescales. The conditions for TS formation become optimal in autumn when the duration of the cooling phase is longer than the time necessary to initiate a TS. The decrease in surface cooling by 1 order of magnitude from summer to winter reduces the lateral transport by a factor of 2. We interpret this transport seasonality with scaling relationships relating the daily averaged cross-shore velocity, unit-width discharge, and flushing timescale to the surface buoyancy flux, mixed-layer depth, and lake bathymetry. The timing and duration of diurnal flushing by TSs relate to daily heating and cooling phases. The longer cooling phase in autumn increases the flushing duration and delays the time of maximal flushing relative to the summer diurnal cycle. Given their scalability, the results reported here can be used to assess the relevance of TSs in other lakes and reservoirs.
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Young, Kathy L. "Role of snow in the hydrology of a High Arctic riparian wetland." Hydrology Research 39, no. 4 (August 1, 2008): 277–86. http://dx.doi.org/10.2166/nh.2008.004.
Повний текст джерелаАнотація:
Riparian wetlands are narrow strips of saturated and vegetated ground forming critical links between dry ground and waterways. The hydrology of a riparian wetland situated within a polar oasis landscape near Eastwind Lake, Ellesmere Island, Nunavut (80°80′N, 85°35′W) was investigated in 2006 using a combination of fieldwork and modelling. Supplemental information from 2005 was also employed. This study showed that deep snow in the nearby stream channel does not promote a period of extended over-bank flooding but instead initially serves as a dam blocking most streamwater from entering and flooding the wetland. It was not until the snow dam melts and disintegrates in response to favourable weather conditions that the wetland becomes flooded and fully recharged. This was a delay of three weeks from the previous year. For the remainder of the 2006 growing season, contributions of meltwater from late-lying snow beds located within and adjacent to the stream channel and near the headwaters were essential for maintaining saturated conditions in the wetland.
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Johnston, Robin R., Andrew G. Fountain, and Thomas H. Nylen. "The origin of channels on lower Taylor Glacier, McMurdo Dry Valleys, Antarctica, and their implication for water runoff." Annals of Glaciology 40 (2005): 1–7. http://dx.doi.org/10.3189/172756405781813708.
Повний текст джерелаАнотація:
AbstractWell-developed surface channels on Taylor Glacier, McMurdo Dry Valleys, Antarctica, begin as medial moraines incised as shallow, narrow surface depressions, and retain this geometry for tens of km. Over a distance of 1100 m, the channel geometry dramatically changes, reaching depths >20m and widths >100 m. After rapidly enlarging, the channels appear to evolve toward a new equilibrium geometry. Compared to the glacier surface, the air temperature in the channels is warmer by ∼1.7˚C, wind speed is reduced by ∼2.4ms–1 and net shortwave radiation is greater by ∼14Wm–2. The microclimate in the channel shifts the energy balance towards enhanced melt. Field evidence and energy-balance modeling indicate ablation in the deep channels is ∼4.5 times greater than the local horizontal glacier surface and that melt accounts for ∼99% of the summer ablation, compared to ∼75% on the adjacent horizontal glacier surface. Melt in these channels supplies 65% of the unaccounted water discharge into the neighboring lake. In large part, the channels generate the water they carry, rather than merely route water generated elsewhere.
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Scholz, Christopher A., Donna J. Shillington, Lachlan J. M. Wright, Natalie Accardo, James B. Gaherty, and Patrick Chindandali. "Intrarift fault fabric, segmentation, and basin evolution of the Lake Malawi (Nyasa) Rift, East Africa." Geosphere 16, no. 5 (July 10, 2020): 1293–311. http://dx.doi.org/10.1130/ges02228.1.
Повний текст джерелаАнотація:
Abstract The Lake Malawi (Nyasa) Rift, in the East African Rift System (EARS), is an ideal modern analogue for the study of extensional tectonic systems in low strain rate settings. The seismically active rift contains the 700-m-deep Lake Malawi, one of the world’s oldest and largest freshwater lakes with one of the most diverse endemic faunal assemblages on Earth. Modern and reprocessed legacy multichannel seismic-reflection data are constrained by velocity information from a wide-angle seismic experiment to evaluate variability in extension, segmentation, and timing of fault development along the 550-km-long rift zone. Fault geometries and patterns of synrift sediment fills show that the Lake Malawi Rift is composed of three asymmetric rift segments, with intervening accommodation zone morphologies controlled by the degree of overlap between segment border faults. Most extension occurs on the basin border faults, and broadly distributed extension is only observed at one accommodation zone, where no border fault overlap is observed. Structural restorations indicate a weakly extended rift system (∼7 km), with diminishing values of extension and thinner rift fill from north to south, suggesting a progressively younger rift to the south. There is no evidence of diking, sill injection, or extrusives within the synrift fill of the Lake Malawi Rift, although the volcanic load of the Rungwe magmatic system north of the lake and related subsidence may explain the presence of anomalously thick synrift fill in the northernmost part of the lake. The thickest synrift depocenters (∼5.5 km) are confined to narrow 10- to 20-km-wide zones adjacent to each rift segment border fault, indicating concentration of strain on border faults rather than intrarift faults. Intrarift structures control axial sediment delivery in the North and Central rift segments, focusing sediment into confined areas resulting in localized overpressure and shale diapirs. The asymmetric, basement-controlled relief was established early in rift development. When overprinted with frequent high-amplitude hydroclimate fluctuations, which are well documented for this basin, the resulting highly variable landscape and lake morphometry through time likely impacted the diverse endemic faunas that evolved within the basin. New seismic-reflection data, augmented by wide-angle seismic data and age constraints from drill core, offer the most highly resolved 3D view to date of latest Cenozoic extensional deformation in East Africa and provide a foundation for hazards analysis, resource assessments, and constraining deformation in a low strain rate, magma-poor active rift.
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QUIROGA-CARMONA, MARCIAL, and JESÚS MOLINARI. "Description of a new shrew of the genus Cryptotis (Mammalia: Soricomorpha: Soricidae) from the Sierra de Aroa, an isolated mountain range in northwestern Venezuela, with remarks on biogeography and conservation." Zootaxa 3441, no. 1 (August 28, 2012): 1. http://dx.doi.org/10.11646/zootaxa.3441.1.1.
Повний текст джерелаАнотація:
In South America, shrews of the genus Cryptotis have a primarily Andean distribution. Based on specimens from the non-Andean Sierra de Aroa in Venezuela, we name Cryptotis aroensis sp. nov., which we assign to the C. thomasi group of thegenus owing to its possession of characters that include a relatively large body size, luxuriant fur, moderately enlargedforefeet with elongated and narrow claws, unicuspid teeth relatively narrow and concave on the posteroventral margin,ectoloph of first upper molar with the anterior element reduced relatively to the posterior element, and mandible with thearticular process not robust, high, and broad, and with the coronoid process joining the ramus at a low angle. The newspecies can be differentiated from other members of the C. thomasi group on the basis of its possession of a uniquecombination of characters, that include a rich grayish brown pelage, a narrow palate at the level of the second upper molars(no overlap in this measurement observed with 146 specimens of 10 other species of the group), nasal cavity and ethmo-turbinals partially visible in occlusal view of palate, lacrimal foramina wide and deep, tympanic process of petromastoidsshowing a minute foramen, unicuspid teeth with posterolingual cuspules, fourth unicuspid tooth labially placed, thirdupper molar complex and nearly as wide as the second upper molar, and bicuspulate lower incisors. The new species isknown from only 3 specimens obtained at the type locality, which is in a pristine patch of cloud forest at elevation 1730m, and represents the first mammalian taxon known to be endemic to the Sierra de Aroa, a small and isolated mountainrange that was previously reported to possess numerous biotic elements that are either exclusive, or shared with the muchlarger Cordillera de la Costa to the east. The clear morphological differentiation of the new species with respect to itsAndean relatives suggests that its ancestors colonized the Sierra de Aroa several glacial maxima ago, when montanevegetation belts were lower than today. The presumably optimal habitat of the new species (cloud forests of the Sierra deAroa above 1500 m) covers less than 40 km2 , and is threatened by deforestation and global climate change. Therefore, thenew species can be categorized as endangered by application of criteria B2a and E of the current “Red List Categories and Criteria” of the International Union for Conservation of Nature.