Flood‐plain responses to contemporary climate change in small High‐Arctic basins (Svalbard,Norway)     

Piotr Owczarek  Adam Nawrot  Krzysztof Migała  Ireneusz Malik  Bartosz Korabiewski 《Boreas: An International Journal of Quaternary Research》2014,43(2):384-402

Changes in the supply of water and sediment to high‐latitude rivers related to contemporary climate change and glacier fluctuations largely determine the activity of fluvial processes. This study reconstructs fluvial dynamics since the end of the Little Ice Age (LIA) in two small, partially glaciated basins in the southern part of Spitsbergen, Svalbard Archipelago. We use a combination of aerial photograph interpretation, field mapping and dendrochronological analysis. Sequences of abandoned channels and glacifluvial terraces are distinctly visible in middle and lower parts of the Brattegg and Arie basins in this area. The advance of glaciers during the LIA in the upper part of the basins led to the development of a braiding pattern and to channel aggradation corresponding to the highest glacifluvial levels. The decreasing activity of these braidplains occurred at the turn of the 19th and 20th centuries, immediately prior to a significant incision period. A second generation of braided channels developed during the first half of the 20th century. Ice‐marginal lake development, less input of fine‐grained sediment to the river channel, and fast incision began from the second half of the 20th century onward. During the last two decades, the main fluvial response to the climatic warming has been contraction of flow within a narrower channel and the abandonment of braidplains. The increased lateral erosion and rate of downcutting and the formation of the most downstream reaches of the modern valley bottom occurred in the 1980s and 1990s. This process was intensified under flood conditions generated by extreme rainfall events. These micro‐scale (small partially glaciated basins) observations concerning the changes of the activity of fluvial processes since the end of LIA may be helpful for the reconstruction of past fluvial changes over longer time scales.  相似文献   

High‐precision U–Pb age and duration of the latest Devonian (Famennian) Hangenberg event,and its implications     

Paul M. Myrow  Jahandar Ramezani  Anne E. Hanson  Samuel A. Bowring  Grzegorz Racki  Michał Rakociński 《地学学报》2014,26(3):222-229

Precise U–Pb zircon dates from three volcanic ash beds that bracket the Hangenberg Shale in the Holy Cross Mountains, Poland, constrain the age and duration of one of the most significant palaeobiological events of the Palaeozoic Era, the Hangenberg Event. It is linked to a terminal Devonian global shift from greenhouse to icehouse climate conditions, a global transgression, and widespread black shale deposition. Our results constrain the Hangenberg Event to between 358.97 ± 0.11 Ma and 358.89 ± 0.20 Ma, with a calculated duration of 0.05 +0.14/?0.05 Ma. A third, underlying ash bed yielded a distinctly older age of 359.97 ± 0.46 Ma. The duration of ~50–100 ka. for the event is comparable to those of Quaternary glaciations, and is consistent with both a glacio‐eustatic origin for the eustatic fluctuations and changes in ocean chemistry that led to this major reorganization of the biosphere.  相似文献   

Correlation between the energy supplied by reconnection and the magnetospheric energy consumption     

I.M. Stanisławska  G.W. Prölss 《Planetary and Space Science》1985,33(9):1091-1093

This study investigates the statistical correlation between the power input into the magnetosphere due to reconnection and the subsequent dissipation of this energy in the magnetosphere as measured by the U_T parameter (Perreault and Akasofu, 1978). It is found that of the three expressions for this energy input P_W, P_K (Gonzalez and Gonzalez, 1984) and ε (Perreault and Akasofu, 1975; Kan et al.,1980), P_W yields the highest correlation with the energy consumption of the magnetosphere.  相似文献   

The perseids 1995 in Poland     

Arkadiusz Olech  Przemysław Woźniak 《Earth, Moon, and Planets》1996,73(2):157-164

Visual observations of 1995 Perseid meteor stream made by Polish astronomy amateurs are reported. Using this material we obtained new accurate points in the activity profile during maximum. The Zenithal Hourly Rates (ZHRs) for the whole period of activity are presented. We also discuss the magnitude, the colour and the velocity distributions of Perseids.  相似文献   

Sunshine duration and its variability in the main ridge of the Karkonosze Mountains in relation to with atmospheric circulation     

Urban  Grzegorz  Migała  Krzysztof  Pawliczek  Piotr 《Theoretical and Applied Climatology》2018,131(3-4):1173-1189

Theoretical and Applied Climatology - Sunshine duration analysis was based on a series of measurements spanning the period from 1901 to 2014 for Śnieżka (1603 m a.s.l.)...  相似文献   

Influence of the atmospheric conditions on PM<Subscript>10</Subscript> concentrations in Poznań, Poland     

Bartosz Czernecki  Marek Półrolniczak  Leszek Kolendowicz  Michał Marosz  Sebastian Kendzierski  Natalia Pilguj 《Journal of Atmospheric Chemistry》2017,74(1):115-139

This study investigates atmospheric conditions’ influence on the mean and extreme characteristics of PM₁₀ concentrations in Poznań during the period 2006–2013. A correlation analysis was carried out to identify the most important meteorological variables influencing the seasonal dynamics of PM₁₀ concentrations. The highest absolute correlation values were obtained for planetary boundary layer height (r = ?0.57), thermal (daily minimum air temperature: r = ?0.51), anemological (average daily wind speed: r = ?0.37), and pluvial (precipitation occurrence: r = ?0.36) conditions, however the highest correlations were observed for temporal autocorrelations (1 day lag: r = 0.70). As regulated by law, extreme events were identified on the basis of daily threshold value i.e. 50 μg m^?3. On average, annually there are approximately 71.3 days anywhere in the city when the threshold value is exceeded, 46.6 % of those occur in winter. Additionally, 83.7 % of these cases have been found to be continuous episodes of a few days, with the longest one persisting for 22 days. The analysis of the macro-scale circulation patterns led to the identification of an easy-to-perceive seasonal relations between atmospheric fields that favour the occurrence of high PM₁₀ concentration, as well as synoptic situations contributing to the rapid air quality improvement. The highest PM₁₀ concentrations are a clear reaction to a decrease in air temperature by over 3 °C, with simultaneous lowering of PBL height, mean wind speed (by around 1 m s^?1) and changing dominant wind directions from western to eastern sectors. In most cases, such a situation is related to the expansion of a high pressure system over eastern Europe and weakening of the Icelandic Low. Usually, air quality conditions improve along with an intensification of westerlies associated with the occurrence of low pressure systems over western and central Europe. Opposite relations are distinguishable in summer, when air quality deterioration is related to the inflow of tropical air masses originating over the Sahara desert.  相似文献   

Projections of changes of areal evapotranspiration for different land-use units in the Wielkopolska Region (Poland)     

Szwed  Małgorzata 《Theoretical and Applied Climatology》2017,130(1-2):291-304

Theoretical and Applied Climatology - Strong global warming has been observed in the last three decades. Central Europe, including Poland, is not an exception. Moreover, climate projections for...  相似文献   

Paleomagnetism of Carboniferous sediments from the West Sudetes (SW Poland)     

Kądziałko-Hofmokl  Magdalena  El-Hemaly  Ibrahim Aly 《Geologie en Mijnbouw》1997,76(1-2):97-104

The studied Carboniferous flysch and molasse sediments from the Intra-Sudetic Basin correspond to the period from Middle Visean to Early Autunian. Main magnetic minerals carrying the natural remanent magnetization (NRM) are goethite, magnetite, maghemite and hematite, all usually secondarily formed and/or remagnetized due to several tectonometamorphic events. In most samples several NRM components were isolated. One of them is usually a Jurassic-Triassic overprint. Some others define the Westphalian-Early Permian segment of the declination and inclination trajectory for the Sudetes calculated according to the reference apparent polar wander path for the Baltica plate. The Sudetic path is slightly shifted to the east compared to the reference path, suggesting the possibility of independent movements of the Sudetes during this time. The majority of isolated NRM components are secondary and related to the Sudetic orogenic phase and later tectonometamorphic activity.  相似文献   

Book review     

Andrea Borgia  Michael Bevis  Carl W. Gable  Hua-Wei Zhou  Richard Barakat  Gerardo G. Tango  Gerardo G. Tango  Jan Błecki 《Pure and Applied Geophysics》1991,135(4):639-655

  相似文献   

[WR] nuclei of planetary nebulae: Inferences from statistical studies of the nebulae     

Sławomir K. Górny  Grazyna Stasińska 《Astrophysics and Space Science》1996,238(1):105-105

There are about 50 galactic planetary nebulae know to have [WR] type nuclei. We have compared their nebular properties with those of the other planetary nebulae in the Galaxy. We have found that the nebular morphological types are similarly distributed in the two groups. Bipolar nebulae constitute only 20% of the total in each group. The distribution of the nebular electron densities and abundance ratios N/O, He/H and C/O are the same in the two groups. The only marked difference is that nebular expansion velocities are larger in the group of planetary nebulae with [WR] central stars. We argue that the WR phenomenon does not preferentially occur in more massive central stars of planetary nebulae, contrary to what has been suggested in some former studies. We demonstrate that, for most of the observed [WR] type objects, the WR phenomenon cannot be triggered by a late helium shell flash event.The results of our investigation are published inAstronomy & Astrophysics 303, 893 (1995) and in the proceedings of the 2nd International Colloquium on Hydrogen-deficient Stars, C.S. Jeffery & U. Heber (eds), Astronomical Society of the Pacific Conference Series, Vol. 96, p. 209 (1996).  相似文献