Unit pockmarks associated with Lophelia coral reefs off mid-Norway: more evidence of control by ‘fertilizing’ bottom currents

High-resolution topographic mapping of Norwegian deep-water Lophelia coral reefs and their immediate surrounding seafloor has disclosed striking associations with small (<5?m diameter) ‘unit’ pockmarks. A total of four study areas with Lophelia reefs and unit pockmarks are here described and discussed. At the large Fauna reef, which spans 500?m in length and 100?m in width (25?m in height), there is a field of 184 unit pockmarks occurring on its suspected upstream side. Three other, intermediate-sized Morvin reefs are associated with small fields of unit pockmarks situated upstream of live Lophelia colonies. For two of the latter locations, published data exist for geochemical and microbial analyses of sediment and water samples. Results indicate that these unit pockmarks are sources of light dissolved hydrocarbons for the local water mass, together with nutrient-rich pore waters. It is suggested that the ‘fertilized’ seawater flows with the prevailing bottom current and feeds directly into the live portion of the Lophelia reefs. With an estimated growth rate of ~1?cm per year for the Morvin Lophelia corals, it would take between 1,000 and 2,000?years for the reefs to colonize the closest unit pockmarks, currently occurring 10–20?m from their leading (live) edges.     

Petroleum-related hydrocarbons in deep and subsurface sediments from South-Western Barents Sea

Subsurface sediments from a pockmark area in South-Western Barents Sea have been earlier found to contain elevated levels of petroleum-related polycyclic aromatic hydrocarbons. This work describes a comprehensive analysis of various biomarkers, including the highly source-specific hopanes, in a 4.5?m long gravity core from the same area, together with subsurface sediment samples from other areas in the region without pockmarks present ("background samples"). A clear difference between the pockmark gravity core and the background sediment cores was found, both with regard to genesis and the level of transformation of organic matter. A number of indicator parameters, such as methylphenanthrene index (MPI-1), point towards a significantly higher maturity of hydrocarbons in the pockmark core throughout its length as compared to the other sampled locations. Higher contents of microbial hopanoids (hopenes) may indicate the former presence of petroleum. These findings confirm the hypothesis of a natural hydrocarbon source in the deeper strata present in the studied location with pockmarks.     

Exposure of phytoplankton to ekofisk crude oil

Solutions of Ekofisk crude oil in sea water were prepared by slow stirring for 21h in a closed system. Headspace and GC/MS techniques were applied to establish dose composition and levels. The standardized test medium produced in a closed system contained approximately 14 mg oil per litre and was dominated by low molecular weight aromatic hydrocarbons and phenols.The toxicity of the standarized oil-containing medium to three marine diatoms was studied in a cage culture turbidostat and by conventional batch culture technique. The three algal species differed in sensitivity to the oil compounds, but showed identical ranking in both test systems.Standardized test medium diluted to 50% with respect to oil content stopped the growth of the most sensitive alga, Skeletonema costatum. For comparison naphthalene was applied and gave 50 % growth reduction at a concentration of 400 μg litre^?1. The growth of Chaetoceros ceratosporum was only slighty affected by the full strength standard test medium, which had no influence on the growth of Phaeodactylum tricornutum, the least sensitive organism. The presence of an oil layer on the surface of the standard test medium during the growth test greatly increased its toxicity and blocked completely the photosynthesis even of P. tricornutum after 4 days.     

Late Pleistocene stratigraphy and sedimentary environments of the Severnaya Dvina‐Vychegda region in northwestern Russia

The Late Pleistocene stratigraphy from the Severnaya Dvina‐Vychegda region of northwestern Russia is revised based on investigations of new localities, revisiting earlier localities, introduction of about 110 new OSL dates and burial depth corrections of earlier published OSL dates, in addition to six new radiocarbon dates. Most of the OSL samples studied here are from fluvial and subaquaeous sediments, which we found to be well bleached. Six chronostratigraphical units and their sedimentary environment are described, with the oldest unit consisting of pre‐Eemian glacial beds. For the first time, Early Weichselian sediments are documented from the region and a fluvial environment with some vegetation and permafrost conditions is suggested to have persisted from the end of the Eemian until at least about 92 ka ago. The period in which a Middle Weichselian White Sea Lake could have existed is constrained to 67?62 ka, but as the lake level never reached the thresholds of the drainage basin, the lake probably existed only for a short interval within this time‐span. Blocking and reversal of fluvial drainage started again around 21?20 ka ago when the Fennoscandian Ice Sheet advanced into the area, reaching its maximum 17?15 ka ago. At that time, an ice‐dammed lake reached its maximum water level, which was around 135 m above present sea level. Drainage of the lake started shortly after 15 ka ago, and the lake was emptied within 700 years. Severe periglacial conditions, with permafrost and aeolian activity, prevailed in the area until about 10.7 ka.     

Reionization and the Cosmic Dawn with the Square Kilometre Array

The Square Kilometre Array (SKA) will have a low frequency component (SKA-low) which has as one of its main science goals the study of the redshifted 21 cm line from the earliest phases of star and galaxy formation in the Universe. This 21 cm signal provides a new and unique window both on the time of the formation of the first stars and accreting black holes and the subsequent period of substantial ionization of the intergalactic medium. The signal will teach us fundamental new things about the earliest phases of structure formation, cosmology and even has the potential to lead to the discovery of new physical phenomena. Here we present a white paper with an overview of the science questions that SKA-low can address, how we plan to tackle these questions and what this implies for the basic design of the telescope.     

Small D-Spacing WC/SiC Multilayers for Future Hard X-Ray Telescope Designs

Multilayer coatings for reflecting hard X-rays up to 80 keV, like W/Si and Pt/C, have been studied for several years. To go to higher energies, in the range of 100 keV to 250 keV, one needs coatings with smaller d-spacings than can currently be made with these material combinations, and a lower interfacial roughness. With the new material combinations of WC/SiC the interface roughness can be reduced down to between 0.23 nm and 0.25 nm enabling bi-layer thicknesses down to 1.0 nm to reflect efficiently. The production of thinner period coatings thus enables the possibility for focusing optic designs with reasonable focal lengths and throughput up to 250 keV.     

Sensitivity Kernels for Time-Distance Inversion

Inversion of local-area helioseismic time-distance data has so far only been done in the ray approximation (Kosovichev, 1996). Since this is a high-frequency approximation its applicability can be questioned for the solar case. Bogdan (1997) showed that for a simple solar model the localized wave packets do follow, but are not confined to, the ray path. We use an approximation based on the first Fresnel zone that has been developed in geophysics by Snieder and Lomax (1996) to go beyond the ray approximation in the inversions. We have calculated sensitivity kernels using both approximations. To test them we use a finite-difference forward modeling of the whole wave field in an acoustic medium reminiscent of the Sun. We use the finite-difference modeling to calculate sensitivity kernels for the full wave field and compare this with the other kernels. The results show that the Fresnel-zone-based kernels are in good agreement with the sensitivity obtained from the modeling. Thus these new kernels represent a significant step forward in the inversion of time-distance data.     

High-frequency Faraday rotation observations of the solar corona

This thesis, presented on January 31, 2007 under the supervision of Professor Christopher T. Russell, discusses the solar coronal magnetic field observations that can be obtained using the phenomenon of Faraday rotation. It was defended in the Department of Earth and Space Sciences at the University of California, Los Angeles (595 Charles E. Young, Dr. East, Los Angeles, CA 90095). A resume can be found at http://acs-consulting.com/.