Estimating Deep Seafloor Interface and Volume Roughness Parameters Using the Multibeam-Hydrosweep System

Utilizing a hull-mounted, multinarrow beam echosounder onboard RV Polarstern, we measured variation of acoustic backscatter with incidence angles at two different sites in the Southern Oceans (Agulhas Plateau and the Riiser Larsen Sea). We modeled the data, using a composite roughness model, including water-sediment interface roughness and sediment volume roughness parameters. The model effectively uses the near normal incidence angle backscatter to determine the seafloor interface roughness parameters employing Helmholtz-Kirchhoff theory. Beyond 20° incidence angles, an application of Rayleigh-Rice theory is made by using a necessary splicing technique (combining both of the theories at 20° incidence angle). The estimated interface and volume roughness parameters are found to be in accordance with the known area geology.     

The effect of tidal inlets on open coast storm surge hydrographs

Bridge scour modeling requires storm surge hydrographs as open ocean boundary conditions for coastal waters surrounding tidal inlets. These open coast storm surge hydrographs are used to accurately determine both horizontal and vertical circulation patterns, and thus scour, within the inlet and bay for an extreme event. At present, very little information is available on the effect that tidal inlets have on these open coast storm surge hydrographs. Furthermore, current modeling practice enforces a single design hydrograph along the open coast boundary for bridge scour models. This study expands on these concepts and provides a more fundamental understanding on both of these modeling areas.     

Energy spectra of cosmic ray nuclei: 4≤Z≤26 and 0.3≤E≤2 GeV amu−1

Energy spectra of cosmic ray nuclei in the charge range 5Z26 have been derived from the response of an acrylic plastic erenkov detector. Data were obtained using a balloon-borne detector and cover the energy range 320E2200 MeV amu^–1. Spectra are derived from a formal deconvolution using the method of Lezniak (1975). Relative spectra of different elements are compared by observing the charge ratios. Secondary-primary ratios are observed to decrease with increasing energy, consistent with the effect previously observed at higher energy. Primary-to-primary ratios are constant for 6Z10 and 14Z26 but vary for 10Z14. This data is found to be consistent with existing data, where comparable, and lends strong support to the idea of two separate source populations contributing to the cosmic ray composition.Work supported by University of Maryland Grant NGR 21-002-316.     

A multidisciplinary multi-scale framework for assessing vulnerabilities to global change

Terrestrial ecosystems provide a number of vital services for people and society, such as food, fibre, water resources, carbon sequestration, and recreation. The future capability of ecosystems to provide these services is determined by changes in socio-economic factors, land use, atmospheric composition, and climate. Most impact assessments do not quantify the vulnerability of ecosystems and ecosystem services under such environmental change. They cannot answer important policy-relevant questions such as 'Which are the main regions or sectors that are most vulnerable to global change?’ 'How do the vulnerabilities of two regions compare?’ 'Which scenario is the least harmful for a sector?’This paper describes a new approach to vulnerability assessment developed by the Advanced Terrestrial Ecosystem Analysis and Modelling (ATEAM) project. Different ecosystem models, covering biodiversity, agriculture, forestry, hydrology, and carbon sequestration are fed with the same Intergovernmental Panel on Climate Change (IPCC) scenarios based on the Special Report on Emissions Scenarios (SRES). Each model gives insights into specific ecosystems, as in traditional impact assessments. Moreover, by integrating the results in a vulnerability assessment, the policy-relevant questions listed above can also be addressed. A statistically derived European environmental stratification forms a key element in the vulnerability assessment. By linking it to other quantitative environmental stratifications, comparisons can be made using data from different assessments and spatial scales.     

Variability and propagation of Labrador Sea Water in the southern subpolar North Atlantic

The variability of two modes of Labrador Sea Water (LSW) (upper and deep Labrador Sea Water) and their respective spreading in the interior North Atlantic Ocean are investigated by means of repeated ship surveys carried out along the zonal WOCE line A2/AR19 located at 43–48°N (1993–2007) and along the GOOS line at about 48–51°N (1997–2002). Hydrographic section data are complemented by temperature, salinity, and velocity time series recorded by two moorings. They have been deployed at the western flank of the Mid-Atlantic Ridge (MAR) in the Newfoundland Basin during 1996–2004. The analysis of hydrographic anomalies at various longitudes points to a gradual eastward propagation of LSW-related signals, which happens on time scales of 3–6 years from the formation region towards the MAR. Interactions of the North Atlantic Current (NAC) with the Deep Western Boundary Current (DWBC) close to Flemish Cap point to the NAC being the main distributor of the different types of LSW into the interior of the Newfoundland Basin. Comparisons between the ship data and the mooring records revealed that the mooring sites are located in a region affected by highly variable flow. The mooring time series demonstrate an elevated level of variability with eddy activity and variability associated with the NAC considerably influencing the LSW signals in this region. Hydrographic data taken from Argo profiles from the vicinity of the mooring sites turned out to mimic quite well the temporal evolution captured by the moorings. There is some indication of occasional southward flow in the LSW layer near the MAR. If this can be considered as a hint to an interior LSW-route, it is at least of minor importance in comparison to the DWBC. It acts as an important supplier for the interior North Atlantic, distributing older and recently formed LSW modes southward along the MAR.     

Platinum-group minerals in quaternary gold placers in the upper Chindwin area of northern Burma

In the Chindwin Basin in northern Burma, there is a system of five Pleistocene terraces in which gold placers with low concentrations of platinum-group minerals (PGM) occur. Samples were taken from four sites in the Chindwin Basin and one from near an ophiolite occurrence on the northeast side of the Chindwin Basin; they were studied under the microscope, with a scanning electron microscope, and an electron microprobe. The main minerals were Pt-Fe and Os-Ir-Ru alloys, usually in a ratio between 2 and 5. In most cases, the shape of the grains allowed a quick distinction between the two types. Sperrylite, laurite, irarsite, cooperite, tulameenite, and isomertieite occur infrequently as individual mineral grains and sometimes as inclusions in the alloy grains. Braggite, platarsite, hollingworthite, bowieite, keithconnite, cuproiridsite, malanite, stibiopalladinite, geversite, kashinite, several unnamed PGM, and Fe, Ni, and Cu sulfides were observed as inclusions, mainly in the Pt-Fe alloys and also to a lesser extent in the Os-Ir-Ru alloys. Lamellar and myrmekite-like intergrowths, oriented exsolution lamellae, and idiomorphic inclusions of sulfides in the alloys indicate a magmatic origin of the PGM. The origin of the PGM is assumed to be ophiolites in northern Burma. A continual decrease in mean grain size occurred during transport.

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Platingruppenminerale in quartären Goldseifen im oberen Chindwingebiet in Nord-Burma

Zusammenfassung Im Gebiet des Chindwin Basin in Nordburma ist ein System von fünf pleistozänen Terrassen ausgebildet, in denen Goldseifen mit geringen Anteilen an PGM auftreten.PGM-Konzentrate von vier Vorkommen des Chindwin Basin und eine weitere Probe aus der Nähe eines Ophiolithvorkommens im Nordosten des Chindwin Basin wurden mit optischer Mikroskopie, Rasterelektronenmikroskopie und Mikrosonde untersucht.Hauptmineralien sind Pt-Fe-Legierungen und Os-Ir-Ru-Legierungen in einem Verhältnis von 2: 1 bis 5: 1. Ihre Morphologie kugeliger oder plattiger, teilweise idiomorpher Körner erlaubt in den meisten Fällen eine rasche Identifizierung der beiden Typen. Sehr selten treten als Einzelminerale, aber auch als Einschlüsse in Legierungen, Sperrylith, Laurit, Irarsit, Cooperit, Tulameenit und Isomertieit auf. Braggit, Platarsit, Hollingworthit, Bowieit, Keithconnit, Cuproiridsit, Malanit, Stibiopalladinit, Geversit, Kaschinit, einige unbekannte PGM und Fe-, Ni- und Cu-Sulfide wurden nr als Einschlüsse, hauptsächlich in Pt-Fe-Legierungen, weniger in Os-Ir-Ru-Legierungen, beobachtet.Lamellare und myrmekitische Verwachsungen, orientierte Entmischungen und idiomorphe Einschlüsse von Sulfiden in Legierungen weisen auf eine magmatische Entstehung der PGM hin. Die Herkunft der PGM wird in Ophiolithen Nordburmas vermutet. Beim Transport hat eine kontinuierliche Abnahme der mittleren Korngrösse stattgefunden.

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With 8 Figures     

The atmospheric mean energetic level and external forcing

Summary The atmospheric mean energetic level and corresponding flow pattern are studied theoretically in terms of the prescribed divergence of the horizontal wind vector. The divergence field may reflect the diabatic effect due to particles of extraterrestrial origin.