The Canyon System off Fimbulisen

In der vorliegenden Arbeit werden Daten einer systematischen Vermessung in der Lazarev Sea nahe des Fimbul-Ice-Shelfs (Fimbulisen) genutzt, die während der Expedition ANT XIX-2 mit dem Fächersonarsystem Hydrosweep DS-2 und dem Sedimentecholot Parasound erhoben wurden. Nach kurzer Darstellung der Hintergründe dieser durchgeführten Untersuchungen in dem Messgebiet wird allgemein auf wesentliche Aspekte der Hydroakustik hinsichtlich der Anwendung von Echolotsystemen eingegangen. Schwerpunktmäßig soll dabei der parametrischen Effekt, das Messprinzip parametrischer Sedimentecholote, behandelt werden. Nach anschließender Anführung zweier praktischer Anwendungen hydroakustischer Messverfahren anhand des Hydrosweep DS-2 und des Parasound-Systems wird eingehend deren Positionierung auf FS 'Polarstern' dargestellt, da sich bei der Aufbereitung der Messungen zeigte, dass sich das größte Problem der Daten beider Systeme in der minderwertigen Qualität der Navigationsdaten abzeichnete. Aus den bereinigten Tiefendaten der Fächersonarmessung wird ein digitales Geländemodell (DGM) mit einer Rasterweite von 100 m generiert. Dieses Modell liegt für die weitere Bearbeitung digital und in Form einer bathymetrischen Karte im Maßstab 1:250,000 vor, bei der die Topographie des Canyon-Systems nahe dem Fimbulisen durch Isolinien mit einer Aquidistanz von 50 m dargestellt wird. Die als Ergebnis der prozessierten Parasound-Daten erhaltenen Seismogramme, die gefiltert im digitalen Bildformat mit bekannter Start- und Endposition für einen definierten Tiefenbereich vorliegen, können zusammen mit dem DGM in einem dreidimensionalen Modell dargestellt werden. Dieses in digitaler Form vorliegende Modell kann durch den Nutzer interaktiv durchschritten und die darin enthaltenen Messergebnisse in ihrer Gesamtheit sowie in Detailansichten aus verschiedenen Perspektiven betrachtet werden, was das gegenseitige Verständnis und Einschätzung der Ergebnisse aus den beiden Messverfahren fördert. Diese gemeinsame Darstellungsweise eines digitalen Geländemodells in Kombination mit den Seismogramm-Bildern des Sedimentecholotes Parasound bietet sich auch hinsichtlich einer geologischen Klassifizierung der verschiedenen Echotypen und einer anschließenden Interpretation der Sedimentationsvorgänge in einem flächenhaft vermessenen Gebiet an.

Isotopic composition of water in fog, rain, throughfall and stemflow in the Monte Verde, Costa Rica

Fog deposition, precipitation, throughfall and stemflow were measured in a windward tropical montane cloud forest near Monteverde, Costa Rica, for a 65-day period during the dry season of 2003. Net fog deposition was measured directly using the eddy covariance (EC) method and it amounted to 1.2 ± 0.1 mm/day (mean ± standard error). Fog water deposition was 5-9% of incident rainfall for the entire period, which is at the low end of previously reported values. Stable isotope concentrations (d18O and d2H) were determined in a large number of samples of each water component. Mass balance-based estimates of fog deposition were 1.0 ± 0.3 and 5.0 ± 2.7 mm/day (mean ± SE) when d18O and d2H were used as tracer, respectively. Comparisons between direct fog deposition measurements and the results of the mass balance model using d18O as a tracer indicated that the latter might be a good tool to estimate fog deposition in the absence of direct measurement under many (but not all) conditions. At 506 mm, measured water inputs over the 65 days (fog plus rain) fell short by 46 mm compared to the canopy output of 552 mm (throughfall, stemflow and interception evaporation). This discrepancy is attributed to the underestimation of rainfall during conditions of high wind.

Quaternary radiolarian counts from Site 181-1123

In the present work Quaternary radiolarian assemblages from the Southwest Pacific were investigated due to their importance for correlation and identification of climatic changes. The studied Ocean Drilling Program (ODP) Site 1123 (Leg 181) is situated on the northern flanks of the Chatham Rise, 1100 kilometres offshore eastern New Zealand and in a water depth o f 3290 metres. It is situated just north of the Subtropical Convergence (STC) in temperate climatic conditions, influenced by the cold deep Deep Western Boundary Current (DWBC) and by the subtropical East Cape Current (ECC) in shallow water depths. A continuous record of 79 sediment samples from this site with a temporal resolution of ~15,000 years provided a medium-resolution record of radiolarian assemblages through the Quaternary. This allowed investigations on how radiolarian assemblages are influenced by climatic variations at obliquity and eccentricity bandwidth, with periodic variations of 40,000, 100,000 and 400,000 years, respectively. Emphasis was given to changes in radiolarian assemblages through the Mid-Pleistocene climate transition (MPT) that marks a fundamental reorganisation in Earth's climate system by change from 40,000 to 100,000 year cycles. Glacial and interglacial variations in oceanography were investigated. Especially the influence of the DWBC was examined due to its input of deep and cold waters to the Pacific Ocean, which plays an important role in Earth's climate system. 167 radiolarian counting groups were examined concerning variations in radiolarian abundance, preservation, diversity, the relative abundance of orders, families, and selected species in order to detect influences of past climatic variations in the Southwest Pacific. No significant changes in radiolarian assemblages were found in coincidence with the onset of the MPT. Investigations led to the recognition of four characteristic phases within the last 1.2 million years. Within one of these phases (Phase Ill), about 160,000 years after the onset of the MPT, fundamental changes in radiolarian assemblages occurred. Investigations yielded highest diversity and highest numbers of nassellarians in abundant samples, whereas sparse samples were mostly poorly preserved and were dominated by spumellarians. Abundance of certain radiolarian families in interglacials or glacials indicated their usefulness as indicators for climatic conditions at Site 1123. Trends o f selected taxa within these families supported the significance of warm- or cool-water preference of these families. Use of 67 radiolarian species as climate indicators showed abundance of warm-water assemblages within interglacials, whereas abundance of cool-water species was increased within glacials. Depth distributional patterns of 52 radiolarian species indicated a strong influence of shallow waters, possibly the EEC, within interglacials and increased influence of deep and intermediate waters, possibly of southern-sourced character and the DWBC in glacial stages.