Frost peat mounds on Hermansenøya (Oscar II Land,NW Svalbard) – their genesis,age and terminology     

Tomasz Jaworski  Władysław Niewiarowski 《Boreas: An International Journal of Quaternary Research》2012,41(4):660-672

Here we present research on previously uninvestigated frost peat mounds occurring on a peat bog in the southern part of Hermansenøya, NW Svalbard. Detailed characteristics are given of the environmental conditions of the peat bog and of the morphological features and surface structure of the frost peat mounds, as well as an analysis of the internal structure of one mound. Three types of frost peat mounds have been distinguished: disc‐shaped mounds (low), mid‐sized mounds with gentle sides, and high mounds with steep sides. Radiocarbon dating of the peat within the frost peat mound performed for the first time on Svalbard and a detailed analysis of the deposits demonstrated that in the high mound (1.3 m) there is an ice‐peat core and peat cover without ice. There are three layers of peat of different ages separated by at least two hiatuses. A generalized history of the development of the peat bog from about 8 ka BP is established. The studied mound displays two development cycles unknown elsewhere. The older relict part of the peat mound was formed during a climatic cooling about 3.0–2.5 ka BP, while the younger part originated during the Little Ice Age (c. AD 1550–1850). Despite certain similarities of these mounds to some palsas, this term should not be applied to the mounds because they are smaller and their cores consist mostly of layers of massive injection ice, the presence of which indicates a pressurized system in their genesis.  相似文献   

What can we learn from the projections of changes of flow patterns? Results from Polish case studies   总被引：1，自引：1，他引：0  

Mikołaj Piniewski  Hadush Kidane Meresa  Renata Romanowicz  Marzena Osuch  Mateusz Szcześniak  Ignacy Kardel  Tomasz Okruszko  Abdelkader Mezghani  Zbigniew W. Kundzewicz 《Acta Geophysica》2017,65(4):809-827

River flow projections for two future time horizons and RCP 8.5 scenario, generated by two projects (CHASE-PL and CHIHE) in the Polish-Norwegian Research Programme, were compared. The projects employed different hydrological models over different spatial domains. The semi-distributed, process-based, SWAT model was used in the CHASE-PL project for the entire Vistula and Odra basins area, whilst the lumped, conceptual, HBV model was used in the CHIHE project for eight Polish catchments, for which the comparison study was made. Climate projections in both studies originated from the common EURO-CORDEX dataset, but they were different, e.g. due to different bias correction approaches. Increases in mean annual and seasonal flows were projected in both studies, yet the magnitudes of changes were largely different, in particular for the lowland catchments in the far future. The HBV-based increases were significantly higher in the latter case than the SWAT-based increases in all seasons except winter. Uncertainty in projections is high and creates a problem for practitioners.  相似文献   

An experimental model for the tektite fluvial transport based on the most distal Polish moldavite occurrences     

Tomasz Brachaniec 《Meteoritics & planetary science》2018,53(3):505-513

Reworking and redeposition of tektites is a highly complex and multistage geological process including many factors. A tumbling experiment was therefore undertaken with the aim of estimating a distance of transport that such moldavites can withstand. Though the experiment probably did not accurately mimic natural conditions, our results proved that moldavites can withstand considerable transport only over a distance of a few kilometers. Observed abrasion of tektites was significant in the early stage of experimental transport; the rate of abrasion decreased correlatively with increasing distance of transport as usual. Overall, given the results obtained from this experimental study and their state of preservation described in the literature, it is very likely that Polish tektites were reworked and redeposited by rivers from the Sudetes Mountains. Based on the paleoreconstruction of river flows, it can be assumed that the Polish tektites originated from two independent sediment supply areas.  相似文献   

Distribution of compact object mergers around galaxies     

Tomasz Bulik  Krzysztof Belczy&#;ski  Wojciech Zbijewski 《Monthly notices of the Royal Astronomical Society》1999,309(3):629-635

Compact object mergers are one of the currently favoured models for the origin of gamma-ray bursts (GRBs). The discovery of optical afterglows and identification of the nearest, presumably host, galaxies allow the analysis of the distribution of burst sites with respect to these galaxies. Using a model of stellar binary evolution we synthesize a population of compact binary systems which merge within the Hubble time. We include the kicks in the supernovae explosions and calculate orbits of these binaries in galactic gravitational potentials. We present the resulting distribution of merger sites and discuss the results in the framework of the observed GRB afterglows.  相似文献   

A late Cenozoic Earth's crust and climate dynamics record from Lake Baikal     

Tomasz Sapota  Ala Aldahan  Göran Possnert  John Peck  John King  Alexander Prokopenko  Mikhail Kuzmin 《Journal of Paleolimnology》2004,32(4):341-349

The sedimentary record from Lake Baikal (Siberia, Russia) has been an important source of information about paleoclimatic variability in the northern hemisphere and dynamics of continental rift development. A lack of reliable chronology has, however, been a major obstacle to fully utilizing the Baikal archive for time scales beyond about 4-5 Myr. In this paper we use the distribution of ¹⁰Be to establish a new chronology for the longest core drilled in Lake Baikal so far. The ¹⁰Be-based chronology spans the last 8 Myr and provides better constraints on sedimentation rates and consequently on an east-west tectonic extension in the lake, which has been apparently coeval with other rifts in Asia that are related to the Tibetan plateau uplift. Our data also show higher ¹⁰Be flux in the sediment section older then 5 Myr compared with the younger period. This can be explained partly by warm and humid climatic conditions of the Miocene and partly by a high cosmic ray flux to the Earth resulting from possible low geomagnetic field intensity during that time.  相似文献   

The Role of Dissolved Organic Carbon in a Shallow Lowland Reservoir Ecosystem — A Long‐term Study     

Andrzej Grniak  Piotr Zieli&#x;ski  Elbieta Jekatierynczuk‐Rudczyk  Magdalena Grabowska  Tomasz Suchowolec 《洁净——土壤、空气、水》2002,30(4):179-189

Long‐term studies were conducted on the polymictic Siemianówka reservoir (SR), situated in a seminatural forest‐peat catchment in NE Poland. The studies were started on the second year of the reservoir's existence. The records showed dissolved organic carbon (DOC) concentrations gradually increasing up to 25…30 mg/L. The largest DOC pool in the reservoir comes from the spring load input, supplemented by the excessive development of phytoplankton with cyanobacteria dominance. The DOC limited the range of the photic zone, eliminated the occurrence of aquatic plants, and was a significant carrier of nutrients, which were gradually released to water, bringing about the “humoeutrophication” of the reservoir.  相似文献   

Studies of aerosol optical depth with the use of Microtops II sun photometers and MODIS detectors in coastal areas of the Baltic Sea     

Olga Zawadzka  Przemysław Makuch  Krzysztof M. Markowicz  Tymon Zieliński  Tomasz Petelski  Vidmantas Ulevičius  Agata Strzałkowska  Anna Rozwadowska  Dorota Gutowska 《Acta Geophysica》2014,62(2):400-422

In this paper we describe the results of a research campaign dedicated to the studies of aerosol optical properties in different regions of both the open Baltic Sea and its coastal areas. During the campaign we carried out simultaneous measurements of aerosol optical depth at 4 stations with the use of the hand-held Microtops II sun photometers. The studies were complemented with aerosol data provided by the MODIS. In order to obtain the full picture of aerosol situation over the study area, we added to our analyses the air mass back-trajectories at various altitudes as well as wind fields. Such complex information facilitated proper conclusions regarding aerosol optical depth and Ångström exponent for the four locations and discussion of the changes of aerosol properties with distance and with changes of meteorological factors. We also show that the Microtops II sun photometers are reliable instruments for field campaigns. They are easy to operate and provide good quality results.  相似文献   

Rupture of an evaporating liquid bridge between two grains     

Boleslaw Mielniczuk  Moulay Said El Youssoufi  Laurent Sabatier  Tomasz Hueckel 《Acta Geophysica》2014,62(5):1087-1108

The study examines rupture of evaporating liquid bridges between two glass spheres. Evolution of the bridge profile has been recorded with the use of high-speed camera. Geometrical characteristics of the bridge were then used to calculate evolution of the variables during the process: Laplace pressure, capillary force, and surface tension force. For the purpose of reference, the bridge evolution is followed also during kinematic extension. During both processes the diameter of the neck decreases, with an acceleration of about 1–2 ms before the rupture. Two distinct rupture modes are observed, depending on the bridge aspect ratio. After the rupture, the mass of liquid splits, forming two separate oscillating drops attached to the spheres, and a suspended satellite droplet. Just before the rupture, an increasing repulsive Laplace pressure, and decreasing negative surface tension force develop. Capillary force follows the trend of the surface tension force, with an accelerating decline. Duration of the whole process and liquid mass stabilization is from 10 to 60 ms.  相似文献   

Crustal Architecture of the Inverted Central Lapland Rift Along the HUKKA 2007 Profile     

Timo Tiira  Tomasz Janik  Elena Kozlovskaya  Marek Grad  Annakaisa Korja  Kari Komminaho  Endre HegedŰs  Csaba Attila Kovács  Hanna Silvennoinen  Ewald BrŰckl 《Pure and Applied Geophysics》2014,171(7):1129-1152

We have studied the lateral velocity variations along a partly buried inverted paleo–rift in Central Lapland, Northern Europe with a 2D wide-angle reflection and refraction experiment, HUKKA 2007. The experiment was designed to use seven chemical explosions from commercial and military sites as sources of seismic energy. The shots were recorded by 102 stations with an average spacing of 3.45 km. Two-dimensional crustal models of variations in P-wave velocity and Vp/Vs-ratio were calculated using the ray tracing forward modeling technique. The HUKKA 2007 experiment comprises a 455 km long profile that runs NNW–SSE parallel to the Kittilä Shear Zone, a major deformation zone hosting gold deposits in the area. The profile crosses Paleoproterozoic and reactivated Archean terranes of Central Lapland. The velocity model shows a significant difference in crustal velocity structure between the northern (distances 0–120 km) and southern parts of the profile. The difference in P-wave velocities and Vp/Vs ratio can be followed through the whole crust down to the Moho boundary indicating major tectonic boundaries. Upper crustal velocities seem to vary with the terranes/compositional differences mapped at the surface. The lower layer of the upper crust displays velocities of 6.0–6.1 km/s. Both Paleoproterozoic and Archean terranes are associated with high velocity bodies (6.30–6.35 km/s) at 100 and 200–350 km distances. The Central Lapland greenstone belt and Central Lapland Granitoid complex are associated with a 4 km-thick zone of unusually low velocities (<6.0 km/s) at distances between 120 and 220 km. We interpret the HUKKA 2007 profile to image an old, partly buried, inverted continental rift zone that has been closed and modified by younger tectonic events. It has structural features typical of rifts: inward dipping rift shoulders, undulating thickness of the middle crust, high velocity lower crust and a rather uniform crustal thickness of 48 km.  相似文献   

Various Approaches to Forward and Inverse Wide-Angle Seismic Modelling Tested on Data from DOBRE-4 Experiment     

Tomasz Janik  Piotr Środa  Wojciech Czuba  Dmytro Lysynchuk 《Acta Geophysica》2016,64(6):1989-2019

The interpretation of seismic refraction and wide angle reflection data usually involves the creation of a velocity model based on an inverse or forward modelling of the travel times of crustal and mantle phases using the ray theory approach. The modelling codes differ in terms of model parameterization, data used for modelling, regularization of the result, etc. It is helpful to know the capabilities, advantages and limitations of the code used compared to others.This work compares some popular 2D seismic modelling codes using the dataset collected along the seismic wide-angle profile DOBRE-4, where quite peculiar/uncommon reflected phases were observed in the wavefield.The ~505 km long profile was realized in southern Ukraine in 2009, using 13 shot points and 230 recording stations. Double P_MP phases with a different reduced time (7.5–11 s) and a different apparent velocity, intersecting each other, are observed in the seismic wavefield. This is the most striking feature of the data. They are interpreted as reflections from strongly dipping Moho segments with an opposite dip. Two steps were used for the modelling. In the previous work by Starostenko et al. (2013), the trial-and-error forward model based on refracted and reflected phases (SEIS83 code) was published. The interesting feature is the high-amplitude (8–17 km) variability of the Moho depth in the form of downward and upward bends. This model is compared with results from other seismic inversion methods: the first arrivals tomography package FAST based on first arrivals; the JIVE3D code, which can also use later refracted arrivals and reflections; and the forward and inversion code RAYINVR using both refracted and reflected phases. Modelling with all the codes tested showed substantial variability of the Moho depth along the DOBRE-4 profile. However, SEIS83 and RAYINVR packages seem to give the most coincident results.  相似文献