Description: Results from a detailed sedimentological investigation of surface sediments from the eastern Arctic Ocean indicate that the distribution of different types of sediment facies is controlled by different environmental processes such as sea-ice distribution, terrigenous sediment supply, oceanic currents, and surface-water productivity.In comparison to other open-ocean environments, total organic carbon contents are high, with maximum values in some deep-basin areas as well as west and north of Svalbard. In general, the organic carbon fraction is dominated by terrigenous material as indicated by low hydrogen index values and high C/N ratios, probably transported by currents and/or sea ice from the Eurasian Shelf areas. The amount of marine organic carbon is of secondary importance reflecting the low-productivity environment described for the modern ice-covered Arctic Ocean. In the area north of Svalbard, some higher amounts of marine organic matter may indicate increased surface-water productivity controlled by the inflow of the warm Westspitsbergen Current (WSC) into the Arctic Ocean and reduced sea-ice cover. This influence of the WSC is also supported by the high content of biogenic carbonate recorded in the Yermak Plateau area.The clay mineral distribution gives information about different source areas and transport mechanisms. Illite, the dominant clay mineral in the eastern central Arctic Ocean sediments, reaches maximum values in the Morris-Jesup-Rise area and around Svalbard, indicating North Greenland and Svalbard to be most probable source areas. Kaolinite reaches maximum values in the Nansen Basin, east of Svalbard, and in the Barents Sea. Possible source areas are Mesozoic sediments in the Barents Sea (and Franz-Josef-Land). In contrast to the high smectite values determined in sea-ice samples, smectite contents are generally very low in the underlying surface sediments suggesting that the supply by sea ice is not the dominant mechanism for clay accumulation in the studied area of the modern central Arctic Ocean.

Description: To reveal the late Quaternary paleoenvironmental changes at the Antarctic continental margin, we test a lithostratigraphy, adjusted to a stable isotope record from the eastern Weddell Sea. The stratigraphy is used to produce a stacked sedimentological data set of eleven sediment cores. We derive a general model of glacio marine sedimentation and paleoenvironmental changes at the East Antarctic continental margin during the last two climatic cycles (300 kyr).The sedimentary processes considered include biological productivity, ice-rafting, current transport, and gravitational downslope transport. These processes are controlled by a complex interaction of sea-level changes and paleoceanographic and paleoglacial conditions in response to changes of global climate and local insolation. Sedimentation rates are mainly controlled by ice-rafting which reflects mass balance and behaviour of the Antarctic ice sheet. The sedimentation rates decrease with distance from the continent and from interglacial to glacial. Highest rates occur at the very beginning of interglacials, i.e. of oxygen isotope events 7.5, 5.5, and 1.1, these being up to five times higher than during glacials.The sediments can be classified into five distinct facies and correlated to different paleoenvironments: at glacial terminations (isotope events 8.0, 6.0, and 2.0), the Antarctic cryosphere adjusts to new climatic conditions. The sedimentary processes are controlled by the rise of sea level, the destruction of ice shelves, the retreat of sea-ice and the recommenced feeding of warm North Atlantic Deep Water (NADW) to the Circumpolar Deep Water (CDW). During peak warm interglacial periods (at isotope events 7.5, 7.3, 5.5., and 1.1), the CDW promotes warmer surface waters and thus the retreat of sea-ice which in turn controls the availability of light in surface waters. At distinct climatic thresholds local insolation might also influence sea-ice distribution. Primary productivity and bioturbation increase, the CCD rises and carbonate dissolution occurs in slope sediments also in shallow depth. Ice shelves and coastal polynyas favour the formation of very cold and saline Ice Shelf Water (ISW) which contributes to bottom water formation. During the transition from a peak warm time to a glacial (isotope stages 7.2-7.0, and 5.4-5.0) the superimposition of both intense ice-rafting and reduced bottom currents produces a typical facies which occurs with a distinct lag in the time of response of specific sedimentary processes to climatic change. With the onset of a glacial (at isotope events 7.0 and 5.0) the Antarctic ice sheet expands due to the lowering of sea-level with the extensive glaciations in the northern Hemisphere. Gravitational sediment transport becomes the most active process, and sediment transfer to the deep sea is provided by turbidity currents through canyon systems. During Antarctic glacial maxima (isotope stages between 7.0-6.0, and 5.0-2.0) the strongly reduced input of NADW into the Southern Ocean favours further advances of the ice shelves far beyond the shelf break and the continous formation of sea ice. Below ice shelves and/or closed sea ice coverage contourites are deposited on the slope.

Description: Pressemitteilung: Seit Beginn der achtziger Jahre ist die Bundesrepublik verstärkt in der Polar- und Klimaforschung tätig. Koordinierendes Forschungszentrum ist das Alfred-Wegener-Institut für Polar- und Meeresforschung in Bremerhaven. Die vom Minister für Forschung und Technologie finanzierte Großforschungseinrichtung hat in den letzten Jahren international an Rang und Namen gewonnen. Hierzu hat nicht zuletzt das modernste und leistungsfähigste Polarforschungsschiff der Welt, die Polarstern, beigetragen.Besonders die Erforschung von Arktis und Antarktis wird als eines der letzten großen Abenteuer auf unserem Planeten angesehen. Sowohl für die Entstehung der Ozeane und Kontinente in ihrer heutigen Anordnung, als auch für das globale Klimageschehen kommt den Polargebieten eine Schlüsselrolle zu.Die Klimaforschung gewinnt durch die aktuellen Umweltprobleme unserer Zeit zunehmend an Bedeutung. Mit der Verbrennung von Öl, Kohle und Gas, ergänzt durch die Produktion noch weiterer klimarelevanter Treibhausgase, hat die Menschheit unfreiwillig ein globales Klimaexperiment begonnen, dessen Tragweite bis heute nur schwer abzuschätzen ist. Das Verständnis der wichtigsten Prozesse, Zusammenhänge und Auswirkungen innerhalb des ungemein komplexen globalen Klimasystems ist Voraussetzung für ein neues Umweltbewußtsein, das die Menschheit gezwungener Maßen in den nächsten Jahrzehnten wird entwickeln müssen.Ergänzt durch Farbgrafiken und ungewöhnliche Aufnahmen aus den Polargebieten, werden die Aufgaben und Ziele der deutschen Polar- und Klimaforschung in einem Vortrag von Dr. Hannes Grobe, Geologe am Alfred-Wegener-Institut, am 6. Dezember 1994 um 19:00 Uhr in der Fachhochschule Wilhelmshaven vorgestellt.