Science and earth science

Polish Polar Research

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Polish Polar Research | 2013 | No 2

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Abstract

This paper presents a study of the seismic P−wave velocity and density structure of the lithosphere−asthenosphere system along a 800 km long transect extending from the actively spreading Knipovich Ridge, across southern Spitsbergen to the Kong Karls Land Volcanic Province. The 2D seismic and density model documents 6–8 km thick oceanic crust formed at the Knipovich Ridge, a distinct continent−ocean−boundary (COB), the eastern boundary of the dominantly sheared Hornsund Fault Zone, and the eastern boundary of the Early Cenozoic West Spitsbergen Fold−and−Thrust Belt. The crustal continent−ocean transitional zone has significant excess of density (more than 0.1 g/cm 3 in average), characteristic for mafic/ultramafic and high−grade metamorphic rocks. The main Caledonian suture zone between Laurentia and Barentsia is interpreted based on variations in crustal thickness, velocities and densities. A high velocity body in the lower crust is preferably interpreted in terms of Early Cretaceous magmatism channelled from an Arctic source southwards along the proto−Hornsund zone of weakness. The continental upper mantle expresses high velocities (8.24 km/s) and densities (3.2 g/cm 3 ), which may be interpreted in terms of low heat−flow and composition dominated by dunites. The lower velocities (7.85 km/s) and densities (3.1 g/cm 3 ) observed in the oceanic lithosphere suggest composition dominated by primitive peridotites. The model of mantle allows for successful direct description of subcrustal masses distribution compensating isostatically uneven crustal load. The estimated low value of correlation between density and velocity in the mantle 0.12 kg × s × m −4 suggests that horizontal density differences between oceanic and continental mantle would be dominated by compositional changes.
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Authors and Affiliations

Lech Krysiński
Marek Grad
Rolf Mjelde
Wojciech Czuba
Aleksander Guterch
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Abstract

An early Permian (late Artinskian–Roadian) cladid crinoid (Catacrinidae gen. et sp. indet.) is reported for the first time from the V ø ringen Member of the Kapp Starostin Formation of Spitsbergen. The specimen is partly articulated and preserves a considerable part of its stalk and a complete cup, but only the proximal portions of its arms. Thus, it cannot be identified with any degree of certainty at the generic level. Despite this, our finding is important as it constitutes one of the youngest records of catacrinid crinoids to date and considerably extends the palaeogeographic distribution of this group.
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Authors and Affiliations

Przemysław Gorzelak
Alfred Uchman
Nils−Martin Hanken
Błażej Błażejowski
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Abstract

This paper describes in detail the phe notypic traits of the newly discovered Leptolyngbya sieminskae sp. n. (Cyanobacteria). The species was found at two islands of the Svalbard archipelago (Spitsbergen and Nordaustlandet) in habitats which differed in humidity, water sources and altitude. The research was conducted at two fjords: on the southern side of Spitsbergen – Hornsund (77 ° N, 015 ° E) and the north−west side of Nordaustlandet – Murchisonfjord (80 ° N, 018 ° E). Although Leptolyngbya sieminskae was found in different latitudes no significant morphological differences were found between the specimens from both sites. The only visible difference is in the thickness of filaments and sheaths.
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Authors and Affiliations

Dorota Richter
Jan Matuła
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Abstract

Twenty one core tops from the central part of Pine Island Bay and nearby Ferrero Bay were collected in early 2010. They originate from a poorly studied area of the Amundsen Sea influenced at greater depths by relatively warm Circumpolar Deep Water. Almost all samples came from water−depths between 550 and 900 m and yield benthic foraminiferal assemblages of moderate variability with a significant decrease in calcareous forms with increasing water−depth. In total, 93 benthic taxa, belonging to 71 genera, are identified at the species level. They share a greater percentage of common species with the Ross Sea than with South Shetland Islands, most likely due to stronger climatic dissimilarity with the latter. Interestingly, the assemblages from Pine Island Bay, share the greatest numbers of taxa with assemblages described from Lützow−Holm Bay in East Antarctica, where the influence of Circumpolar Deep Water has been also recognized.
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Authors and Affiliations

Wojciech Majewski
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Abstract

There are hardly any data concerning the vertical micro−distribution of protozoa in water column in cryoconite holes on the glacier surface. Such comparisons can provide insights into the ecology of protozoa. The present research was made on Ecology Glacier (South Shetland Islands, Antarctic); vertical microzonation of c iliates in relation to physical and chemical parameters in cryoconite holes was studied. The density and biomass of protozoans significantly differed between the studied stations (cryoconite holes), with the lowest numbers in the surface water and the highest in the bottom water. The surface waters were dominated by mixotrophic and omnivorous taxa, whe reas the deepest sampling level has shown the increase of the proportion of bacterivore species . Ordination analysis indicated that TN and P−PO 4 can strongly regulate the abundance and species composition of protozoa. The redundancy analyses (RDA) showed that the ciliate communities can be separated into two groups. The first group included species associated with surface water: Halteria grandinella and Codonella sp. The second group included species that are associated with bottom water: Prorodon sp. , Holosticha pullaster , Stylonychia mytilus −complex and small scuticociliates.
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Authors and Affiliations

Tomasz Mieczan
Monika Tarkowska-Kukuryk
Dorota Górniak
Aleksander Świątecki
Marek Zdanowski
Małgorzata Adamczuk
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Abstract

The climatic change on King George Island (KGI) in the South Shetland Islands, Antarctica, in the years of 1948–2011 are presented. In the reference period, a statistically significant increase in the air temperature (0.19 ° C/10 years, 1.2 ° C in the analysed period) occurred along with a decrease in atmospheric pressure (−0.36 hPa/10 years, 2.3 hPa). In winter time, the warming up is more than twice as large as in summer. This leads to decrease in the amplitude of the annual cycle of air temperature. On KGI, there is also a warming trend of daily maximum and daily minimum air temperature. The evidently faster increase in daily minimum results in a decrease of the diurnal temperature range. The largest changes of air pressure took place in the summertime (−0.58 hPa/10 years) and winter (−0.34 hPa/10 years). The Semiannual Oscillation pattern of air pressure was disturbed. Climate changes on KGI are correlated with changing surface temperatures of the ocean and the concentration of sea ice. The precipitation on KGI is characterised by substantial variability year to year. In the analysed period, no statistically significant trend in atmospheric precipitation can be observed. The climate change on KGI results in substantial and rapid changes in the environment, which poses a great threat to the local ecosystem.
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Authors and Affiliations

Marek Kejna
Andrzej Araźny
Ireneusz Sobota

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