«Changing Polar Regions 25th International Congress on Polar Research March 17-22, 2013, Hamburg, Germany German Society for Polar Research Edited by ...»
Interferometric radar data (InSAR) offer the capability for precise, spatially detailed measurement of the surface topography of glaciers and ice sheets. Repeat observations in different years deliver changes of glacier volume which can be converted into changes of glacier mass by estimating the mean density of the depleted or gained volume. The application of single-pass InSAR systems is of particular interest for mapping glacier surface topography because these measurements are not affected by temporal decorrelation and atmospheric phase delay. First spaceborne single-pass InSAR systems operated on the Space Shuttle in February 2000, the Shuttle Radar Topography Mission (SRTM) with C-band and Xband dual antenna SAR systems, mapping the topography of land masses between 60°N and 56°S. The German TanDEM-X satellite mission, launched in June 2010 and operating in bi-static interferometric configuration with the TerraSAR-X satellite, offers improved capabilities for mapping the topography of global land surfaces. The DEMs have a spatial resolution of about 12 metres and 2 metre vertical point-to-point error. For determining the elevation of glacier surfaces it is necessary to correct for the penetration of the radar signal into snow and ice. This is of particular importance if different sensors types, such as optical stereo sensors and InSAR, are used for estimating topographic change.
"Changing Polar Regions" - 25th International Congress on Polar Research 2013 PALEO SOILS AS DOCUMENTS OF LOCAL CLIMATE CHANGES
DURING THE PLEISTOCENE
Paleo soils are useful documents of earth history. Properly interpreted, they allow conclusions about site specific paleoenvironmental conditions. In a sand pit next to Jahrsdorf in Schleswig-Holstein (N 54,048°,E 009,620°), an Eemian aged (127 - 115 ky bp) paleo soil above Saalian sands has been exposed during excavation activities (Grube, 2012).
Photography of soil-morphological features and in situ analysis of hydromorphic properties and soil colours, as well as laboratory analysis of Fe-, C and N- content, C/N ratio and granulometric distribution has been conducted. With the acquired set of data, the pedological past of the sediments and paleoenvironmental conditions that governed the region from the latest Saalian periods to the Holocene, were concluded. The paleo soil is suggested to be of podzolic nature and represent a period during the Pleistocene in which the local climate was temperate and humid (Precipitation exceeded Evapotransporation) and during which the geomorphology of the landscape was stable (no erosion potential at this site, no sedimentation from other sites). Subsequently, the soil was covered by sediments and overprinted by cryogenic processes – this implies arctic-like conditions during the Weichselian glacial period. In the Holocene, on the modern surface, a cambisol formation took place. Later during the Holocene, the soil was transformed into arable land. Soil data delivered information that allowed the reconstruction of the site-specific paleoenvironmental conditions.
"Changing Polar Regions" - 25th International Congress on Polar Research 2013 FLUXES OF DISSOLVED ORGANIC CARBON FROM POLYGONAL
TUNDRA ON SAMOYLOV ISLAND, LENA RIVER DELTA, SIBERIA
Arctic landscapes often contain carbon-rich wetland features overlying permafrost.
These wetlands drain towards the Arctic Ocean in complex channel pathways and carry a nutrient load that includes dissolved organic carbon (DOC). This important part of the carbon cycle is linked to changes in the permafrost landscape expected from climate change, including thermokarst development and shifts in the timing and magnitude of precipitation and temperature.
In this study, we present the results of a measurement campaign in the summer of 2012, in a patterned polygonal landscape in the low tundra of Siberia’s Lena River Delta. The geographical structure of this landscape contains an interconnected ice wedge network slowly draining the wet, low-lying polygon centers. We installed and calibrated three weirs to measure hydrological discharge from a polygon network on Samoylov Island. Water samples were taken weekly to calibrate an in-stream UVVisible light absorption instrument used to estimate the dissolved organic carbon concentrations in these streams. Through analysis of the absorption characteristics, qualitative indicators of the carbon content are also derived, yielding insight about the aromaticity and molecular structure of the carbon. We found that this drainage is punctuated by storm events overlain across a slow-draining hydrology governed by summer permafrost thaw. The lateral outflux of DOC is substantially less in carbon terms than the landscape’s carbon sink function (driven primarily by plant photosynthesis in the summer). We will present a preliminary estimate of the DOC outflux from this polygon landscape during the summer growing season, and analyze how qualitative characteristics of this DOC change during the season. We conclude by investigating the utility of the qualitative characteristics for flow source partitioning.
"Changing Polar Regions" - 25th International Congress on Polar Research 2013 NEW CONSTRAINTS ON THE STRUCTURAL EVOPLUTION OF
EAST ANTARCTICA: THE MAIN SHEAR ZONE OF SØR RONDANE,
EASTERN DRONNING MAUD LANDRuppel, A1,2, Läufer, A.2, 1 Fachbereich Geowissenschaften, Lisker, F.1, Jacobs, J.3, Elburg, Universität Bremen, Germany M.4, Damaske, D.2, Lucka, N.1 2 Bundesantalt für Geowissenschaften und Rohstoffe, Hannover, Germany Department of Earth Science, University of Bergen, Bergen, Norway, SAEES, University of KwaZulu-Natal, Durban, South Africa Structural investigations were carried out along the Main Shear Zone (MSZ) of western Sør Rondane (22°–25°E, 71.5°–72.5°S) to gain new information about the position of the East-/West-Gondwana suture and the ancient plate tectonic configuration during Gondwana amalgamation. These studies are part of the longerterm GEA (Geodynamic Evolution of East Antarctica) project of BGR, jointly carried out in cooperation with AWI.
The WSW-ENE striking MSZ divides south-western Sør Rondane in a northern amphibolite-facies terrane and a southern tonalite–trondhjemite–granodiorite (TTG) terrane. The structure can be traced over a distance of ca. 100 km and reaches several hundred meters in width. It is characterized by a right-lateral sense of movement and marked by a transpressional and also transtensional regime.
Ductilely deformed granitoids (ca. 560 Ma: SHRIMP U-Pb of zircon) and ductile – brittle structures, which evolved in a transitional ductile to brittle regime in an undeformed syenite (ca. 499–459 Ma, Ar-Ar mica), provide a late Proterozoic/ early Paleozoic time limit for the activity of the shear zone (Shiraishi et al., 2008; Shiraishi et al., 1997).
Documentation of ductile and brittle deformation allows reconstructing up to eight deformation stages. Cross-cutting relationships of structural features mapped in the field complemented by published kinematic data reveal the following relative age succession: [i] Dn+1 - formation of the main foliation during peak metamorphism, [ii] Dn+2 - isoclinal, intrafolial folding of the main foliation, mostly foliation-parallel mylonitic shear zones (1-2 meter thick), [iii] Dn+3 - formation of tight to closed folds, [iv] Dn+4 - formation of relatively upright, large-scale open folds, [v] Dn+5 - granitoid intrusion (e.g. Vengen granite), [vi] Dn+6 - dextral shearing between amphibolite and TTG terranes, formation of the MSZ, [vii] Dn+7 - intrusion of late- to post-tectonic granitoids, first stage of brittle deformation (late shearing along MSZ), intrusion of post-kinematic mafic dykes, [viii] Dn+8 - second stage of brittle deformation including formation of conjugate fault systems. The latter point to a WNW-ESE respectively NW-SE oriented maximum paleostress direction and indicate the latest deformation event; they are possibly related to the break-up and fragmentation of Gondwana.
"Changing Polar Regions" - 25th International Congress on Polar Research 2013 DIVERSITY AND RICHNESS OF MYCO- AND PHOTOBIONTS IN
Lichens as a symbiosis between a fungus (mycobiont) and a photosynthetic partner (photobiont) are the most successful vegetation forming organism in the arid and cold desserts of the southern Polar regions. Although Antarctica’s ecosystems represent some of the simplest in the world, it is increasingly becoming clear that their biodiversity is far greater than previously thought and that spatial variations in species diversity are complex, possibly reflecting regional to local variations in climate.
As part of a comprehensive study on a crustose lecideoid lichen group in Antarctica, not only the mycobiont- but also the photobiont diversity and abundance were investigated. Considering the climatic factors a phylogeny of the photobiont sequences (ITS) in combination with samples from Arctic and Alpine and other temperate regions reveals the presence of five, possibly even six major Trebouxia clades in twelve different species of Antarctic lecideoid lichens. Two clades are formed by members of the cosmopolitan T. jamesii and T. impressa aggregates but for all other clades no close match of any known Trebouxia species could be found in the sequence databases. One genetically uniform and well supported Trebouxia clade was only found in the climatically unique cold desert regions of Antarctica (preliminarily named Trebouxiasp. URa1). This clade may represent an endemic photobiont species since it seems to be restricted to the Antarctic cold deserts, a habitat that has no ecological counterpart elsewhere in the world.
Trebouxia sp. URa2 and URa3 are widely distributed and abundant in the investigated areas. The Antarctic lichens studied here are predominantly not specific for a single photobiont species or lineage except for Lecidella greenii and L. siplei.
These two species are preferably associated with Trebouxia sp. URa2, although in the sampling areas of both species, a pool of several other photobionts is available.
On the other hand, Lecidea cancriformis, the most widespread lichen in Antarctica associates with the highest diversity of the available photobiont clades.
"Changing Polar Regions" - 25th International Congress on Polar Research 2013 THE ROLE OF PHOTOBIONTS IN ANTARCTIC LICHENS: STRESS
PHYSIOLOGY AND PHOTOBIOLOGY
The flora of continental Antarctica is dominated by lichens. These symbiotic associations consist of a fungus (the mycobiont) and a green alga or cyanobacterium (the photobiont) essential for carbon nutrition of the symbiotic organisms. Lichen thalli occur in crustose and more complex growth forms. In non-crustose species (macrolichens) of continental Antarctic habitats, green algal photobionts of the genusTrebouxia clade S are the most widespread. In the study presented, the role of the photobionts concerning stress tolerance was examined byphysiological experiments with isolated photobionts and entire lichen thalli. The study has been performed in situ and under laboratory conditions with lichens from North Victoria Land, continental Antarctica. Photobionts were isolated from lichens collected at North Victoria Land, Coal Nunatak (Alexander Island) and Rothera Point (Antarctic Peninsula), as well as from a European site (Gotland, South Sweden) for comparison. The physiological response of the various isolated Trebouxia photobionts to desiccation/rehydration, freezing/thawing and high light intensities indicates a habitat-specific stress physiology. The photobionts of endemic Antarctic lichens showed peculiar resistance towards the applied stressors. While desiccation and high light intensities caused long-term reduction of the studied photobionts’ vitality, freezing could easily be tolerated. The results will improveknowledge on a) the role of adaptations on the photobiont level in the physiology of lichen thalli, and b) the physiological prerequisites of lichens for the successful colonization of the terrestrial Antarctic biome.
The novel comparative approach of the study presented will give fundamental information on the physiology of lichens, additionally providing a baseline for the recognition and interpretation of the consequences of environmental change in future decades.
"Changing Polar Regions" - 25th International Congress on Polar Research 2013 NITROGEN AVAILABILITY AND NITRIFICATION IN PERMAFROST
AFFECTED SOILS OF SAMOYLOV ISLAND IN THE LENA RIVERDELTA
Permafrost soils (Gelisols) cover about a quarter of the northern hemisphere surface.
Gelisols are in subsoils continuously frozen throughout the year and only the active layers thaw during the short vegetation period. The main characteristic of these soils covered by polygonal carex-sedge tundra vegetation is the extreme soil moisture and temperature regime, which ranges from -30°C to +18°C. Element cycles of carbon (C) and nitrogen (N), which are mostly driven by microorganisms, are influenced by these extreme environmental parameters. In this study, nitrification as one important part of the microbial controlled N-cycle was investigated in typical wet arctic tundra sites of the Lena river delta, Northeast Siberia, Russia. During nitrification ammonia is oxidized in two steps via nitrite to nitrate.