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«Changing Polar Regions 25th International Congress on Polar Research March 17-22, 2013, Hamburg, Germany German Society for Polar Research Edited by ...»

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ANTARCTICA

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The Pan-African (650-500 Ma) collision of East- and West Gondwana affected a major part of the Dronning Maud Land. The western front of this collision zone is exposed at the nunataks of the HeimefrontFjella, where a major shear zone separates Pan-African metamorphic overprinted rocks in the east from nonoverprinted rocks in the west. The shear zone causes an elongated magnetic anomaly, which allows tracing the shear zone into the ice-covered areas NE and SW of the HeimefrontFjella.A similar elongated magnetic anomaly has been detected 300 km farther east close to the Kohnen Station, named Kohnen lineament. The anomaly stretches out from NE to SW over a distance of about 100 km. In the NE it links to the Forster Magnetic Anomaly, whereas it passes into another narrow and stretched anomaly in the SE, indicating a possible continuation. However the causing geological structures are inaccessible for direct geological sampling, as the area is completely covered by ~3 km thick ice, but the aeromagnetic data indicate that the Kohnen Lineament could represent the eastern front of the East-West Gondwana collision zone in this region.

"Changing Polar Regions" - 25th International Congress on Polar Research 2013 SIMULATING THE EFFECT ANTHROPOGENIC CLIMATE CHANGE

ON THE GREENLAND ICE SHEET

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In the standard simulations of CMIP5 the coupling with the ice sheets is not included.

Only few groups have been able to perform CMIP5 simulations with interactively coupled ice sheets. Beside its importance for the future development of global mean sea level, the Greenland ice sheet has also the potential to strongly affect deep water formation especially in the Labrador Sea but also in the Nordic Seas. Here simulations are presented with interactively coupled ice sheet models which allows to assess the uncertainty arising from ice sheet model and coupling technique.

The climate model ECHAM5/MPIOM is coupled interactively to two different ice sheet models using two different coupling strategies. The ice sheet models are a Greenland set-up of SICOPOLIS (10km), and Greenland (10km) and northern hemisphere (20km) set-ups of PISM. The coupling is done either with a simple positive degree days approach or a mass-balance scheme calculating the surface melting with an energy-balance scheme. The models are run without flux correction of anomaly coupling.

The resulting net mass loss rates for the Greenland ice sheet in a 1 percent scenario capped at 4x preindustrial atmospheric CO2 concentrations showed a considerable dependence on both ice sheet model and coupling technique. The resulting differences in atmospheric climate, however, are small within the first centuries and restricted to the immediate vicinity of Greenland.

The feedbacks between atmosphere, ocean and the Greenland ice sheet are studied in a series of sensitivity experiments. It turns out that the future development of the Atlantic overturning and its associated heat transport are quite important for the future development of the mass of the Greenland ice sheet: The stronger the Atlantic overturning remains, the stronger the mass loss of the Greenland ice sheet.

"Changing Polar Regions" - 25th International Congress on Polar Research 2013 DIE POLARREGIONEN IM KLIMAWANDEL

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Im globalen Klimasystem spielen die Polarregionen eine herausragende Rolle weil sie mit ihren großen von Eis und Schnee bedeckten, weißen Gebieten den Strahlungs- und damit den Energiehaushalt der Erde entscheiden beeinflussen.

Gleichzeitig aber reagieren sie in besonderer Weise auf Veränderungen des globalen Klimas, die es uns ermöglichen sie als Frühwarnsysteme künftiger Veränderlichkeit zu nutzen.

Auch wenn die polaren Regionen weit von uns entfernt sind so beeinflussen sie – und hier insbesondere die Arktis – doch auch unser tägliches Leben, z.B. über ihre Fernwirkung auf unser Wettergeschehen oder über die Veränderungen des Meeresspiegels.

Nach einem einführenden Teil über den gegenwärtigen Zustand dieser Regionen wird anhand einzelner Fallbeispiele gezeigt, wie unser Wissen über die Veränderlichkeit zustande kommt und auch welchen Aufwand es bedeutet in diesen Regionen zu forschen. Aus diesem Wissen lassen sich dann Prognosen für künftige Veränderungen ableiten. Allerdings sind diese Prognosen noch mit großen Unsicherheiten behaftet, weil wir noch zu wenig wissen über verschiedene Prozesse, die zu Veränderungen führen.

Daraus lässt sich künftiger Forschungsbedarf ableiten, der im Ausblick exemplarisch dargestellt wird.

"Changing Polar Regions" - 25th International Congress on Polar Research 2013 ACCUMULATION AND STABLE-ISOTOPE STUDIES AT KOHNEN STATION, DRONNING MAUD LAND, ANTARCTICA, FROM 1999 THROUGH 2011.

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The area of the later Kohnen station (75°00’06”S, 0°04’04”E) in Dronning Maud Land, Antarctica, was visited the first time during the EPICA-pre site survey in the austral summer 1997/98. In 1999/2000 the construction of the base started. At the same time a glaciological programme was initiated to study snow accumulation and stable isotope in the surroundings of the base and the site of the EDML ice core, respectively. The data of 20 snow pits cover the period 1986-2010. The pits had been sampled with a depth resolution between 1.5cm and 5cm. Linear fits through the time series do not show a significant trend neither for accumulation nor δ18O content. However, for the year 2008 an outstanding high accumulation rate was found in all 6 snow pits which were digged in January 2011. The average δ18O content and mean accumulation rate for the period 1259-1816 from 4 nearby firn cores (B32, B34, B37 and EDML) is -45.01 ‰-SMOW and 62.3 kg m-2 a-1, respectively. Both the mean annual isotope content and the mean annual accumulation rate during the past 25 years are above the long term average. They display values of -44.00 ±1.07 ‰-SMOW and 72.5 ±11.2 kg m-2 a-1 respectively.





Thus, the results of the snow pit studies fit into the general pattern of increasing accumulation rates and increasing stable-isotope contents of snow during the 20th century.

"Changing Polar Regions" - 25th International Congress on Polar Research 2013 LATE QUATERNARY PALEOCLIMATE INFORMATION FROM

STABLE WATER ISOTOPES IN ICE WEDGES AT THE DMITRY

LAPTEV STRAIT, NORTHEAST SIBERIAN ARCTIC

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Ice wedges are the most abundant type of ground ice in the ice-rich permafrost deposits of the Northeast Siberian Arctic. They are formed by the periodic repetition of frost cracking and subsequent crack filling in spring, mostly by melt water of winter snow. Ices wedges can be studied by means of stable-water isotopes. Their isotopic composition is directly linked to atmospheric precipitation (i.e. winter snow) and, therefore, indicative of past winter climate conditions even though also genetic aspects, i.e. sublimation, melting and refreezing in the snowpack and the frost crack, have to be taken into account.

Here we present stable-water isotope data of ice wedges at the Oyogos Yar coast of the Dmitry Laptev Strait (72.7°N, 143.5°E). The ice wedges from different stratigraphic units comprising pre-Eemian sediments, Middle Weichselian Ice Complex (Yedoma) sediments and Holocene themokarst (Alas) sediments were studied and sampled in 2002 and 2007. Stable-water isotopes were measured in the stable-isotope lab of the Alfred Wegener Institute in Potsdam, Germany.

Ice wedge stable-water isotope data indicate substantial variations in Northeast Siberian Arctic winter climate conditions (δ18O) as well as shifts in the moisture generation and transport patterns (d excess) during the Late Quaternary, in particular between Glacial and Interglacial but also during the last centuries.

Ice wedges of the pre-Eemian Kuchchugui and Bychchaguy Suites exhibit mean δ18O values of about -30‰ and -34‰, respectively, indicating cold to extreme cold winter temperatures. The latter represents the coldest conditions found in ice wedges at the Oyogos Yar coast. Mean d-excess values are about 3‰ and 6‰, respectively.

Small ice wedges in Eemian sediments show distinctly warmer mean δ18O values of about -24‰ and mean d-excess values of about 4‰. However, probably they represent younger epigenetically grown ice wedges with an isotopic composition that might be influenced by sediment-ice interaction. Huge syngenetic ice wedges of the Weichselian Yedoma Suite are characterized by mean δ18O values of -29‰ to -33‰ and mean d-excess values around 6‰ in different altitude levels, reflecting cold to extreme cold winter temperatures. On top of the Ice Complex as well as in a thermokarst depression, formed during the Late Glacial, Holocene ice wedges could be found. They have been grown predominantly in the Middle and Late Holocene and "Changing Polar Regions" - 25th International Congress on Polar Research 2013 exhibit mean δ18O values of about -25‰ and mean d-excess values of 8‰, mirroring distinctly warmer winter temperatures in the Holocene. Recent ice wedges grown in the last decades are characterized by mean δ18O values of about -22‰ and mean-d excess values of 8‰, testifying the recent winter warming in the Arctic.

"Changing Polar Regions" - 25th International Congress on Polar Research 2013 COMPARATIVE ANALYSIS OF DIFFERENT PARAMETERS OF

DESCHAMPSIA ANTARCTICA POPULATION SUCCESS IN ONE

POLAR SEASON

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A number of measures can be designated to monitor plant population fitness in Antarctica, however any of these indices will only be reliable if the information retrieved from such measurements is consistent across different approaches. Thus, finding correlated indices would provide a more robust system of population success assessment, which in turn would allow developing appropriate parameters for plant population monitoring. To address this question, in the present paper we analyze correlation between biometric parameters, relative nuclear DNA content in leaf parenchyma cells, and finally individual projective cover of D. antarctica in the vicinity of Admiralty Bay during one polar season.

Specifically, we carried out a complex study of different populations of Deschampsia antarctica from the Admiralty Bay area (King George Island). The field survey and sampling was conducted in the austral summer season 2005/06. During the fieldwork, a network of different, relatively homogenous vegetation stands was established and surveyed, the sites being located in the ice-free areas of Point

Thomas and Keller Peninsula. The following population parameters were estimated:

percentage cover, generative stem height, leaf length, inflorescence length, flower length, number of flowers in an inflorescence and relative content of DNA.

To examine differences in biometric and cytological parameters of D. antarctica, distribution curves were plotted for each parameter over all sampling sites.

Differences in the distribution curves were tested by nonparametric median test.

Extreme grouping of pairwise plant comparisons was applied to data from six populations of D. antarctica in respect to the following parameters of population success: biometric traits (ΔPh) – percentage cover (⏐ΔS⏐), relative nuclear DNA content (ΔrcD) – percentage cover (⏐ΔS⏐), and biometric traits (ΔPh) – relative nuclear DNA content (ΔrcD).

Analysis of data has allowed to cluster populations with significant positive correlations between traits and with negative correlations. In the case of positive correlation, population success by one parameter correlated with success by other "Changing Polar Regions" - 25th International Congress on Polar Research 2013 parameters. In the cases of negative correlation, the populations appeared to have chosen a strategy when a high value of one parameter was accompanied by decrease in other parameters (perhaps due to compensatory effects). We separated out populations which, based on success by all the studied parameters, had formed clusters of peculiar complex population success.

Monitoring of population status of D. antarctica can be carried out based on a greater number of parameters, while the search for optimal conditions can be done by looking for correlations among currently investigated parameters. However, population success should not be estimated based on a single parameter.

We express our gratitude to the National Antarctic Scientific Center of the State Agency for Science, Innovation, and Informatization of Ukraine. This study was done under the contract between the National Antarctic Scientific Center and the Institute of Molecular Biology and Genetics NAS of Ukraine # H/3-2011 “Development of a bioindicator system of climate change in coastal Antarctica based on the dynamics of terrestrial plant cenoses” (2011-12), as well as a joint project between the NAS of Ukraine and Polish Academy of Sciences: “Ecological and genetic basis of plants adaptation to extreme environments” (2012-14).

"Changing Polar Regions" - 25th International Congress on Polar Research 2013 LONG-TERM STATISTICS OF POLYNYAS IN THE WEDDELL-SEA

AREA USING SATELLITE-BASED THIN ICE RETRIEVALS

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An algorithm for the retrieval of thin ice thicknesses (TIT) from infrared satellite data is applied for the Antarctic Weddell Sea in order to determine long-term statistics of polynyas. The algorithm uses MODIS Terra/Aqua data (1km resolution) in combination with an energy balance model and ECMWF ERA-Interim reanalyses as atmospheric forcing for the period 2002-2011. From this TIT dataset, quantities like polynya area (POLA), polynya days (PD), thin ice thickness distribution and ice production rates were derived and compared to recent studies using passive microwave derived data and reference sea ice concentration data from AMSR-E. The higher spatial resolution of MODIS compared to SSM/I or AMSR-E allows for the detection of very narrow polynyas. Although the method is restricted to cloud-free conditions, the spatial coverage is good because of the large number of overpasses at polar latitudes.



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