The Arctic is no longer put on ice: Evaluation of Polar cod (Boreogadussaida) as a monitoring species of oil pollution in cold waters

The withdrawing Arctic ice edge will facilitate future sea transport and exploration activities in the area, which calls for the establishment of relevant cold water monitoring species. The present study presents first results of field baseline levels for core oil pollution biomarkers in Polar cod (Boreogadussaida) sampled from pristine, Arctic waters. Furthermore, biomarker response levels were characterized in controlled laboratory exposure experiments running over 2 weeks. Fish exposed to a simulated petrogenic spill (1 ppm dispersed, crude oil) exhibited elevated hepatic EROD activity, bile PAH-metabolites, and hepatic DNA-adducts, whereas male individuals exposed to simulated produced water (30 ppb nonylphenol) exhibited a strong induction of plasma vitellogenin. In conclusion, the results demonstrated low and robust biomarker baseline levels that were clearly different from exposure responses. In combination with its high abundance and circumpolar distribution, the Polar cod seems well qualified for oil pollution monitoring in Arctic waters.     

Urban green commons: Insights on urban common property systems

The aim of this paper is to shed new light on urban common property systems. We deal with urban commons in relation to urban green-space management, referring to them as urban green commons. Applying a property-rights analytic perspective, we synthesize information on urban green commons from three case-study regions in Sweden, Germany, and South Africa, and elaborate on their role for biodiversity conservation in urban settings, with a focus on business sites. Cases cover both formally established types of urban green commons and bottom-up emerged community-managed habitats. As our review demonstrates, the right to actively manage urban green space is a key characteristic of urban green commons whether ownership to land is in the private, public, the club realm domain, or constitutes a hybrid of these. We discuss the important linkages among urban common property systems, social–ecological learning, and management of ecosystem services and biodiversity. Several benefits can be associated with urban green commons, such as a reduction of costs for ecosystem management and as designs for reconnecting city-inhabitants to the biosphere. The emergence of urban green commons appears closely linked to dealing with societal crises and for reorganizing cities; hence, they play a key role in transforming cities toward more socially and ecologically benign environments. While a range of political questions circumscribe the feasibility of urban green commons, we discuss their usefulness in management of different types of urban habitats, their political justification and limitation, their potential for improved biodiversity conservation, and conditions for their emergence. We conclude by postulating some general policy advice.     

Techniques for the Eduction of Coherent Structures from Flow Measurements in the Atmospheric Boundary Layer

Two empirical methods to detect coherent motions embedded in the flow field have been compared, namely the variable interval time average (VITA) method and a wavelet-based technique, both with artificial signals as well as velocity measurements from the atmospheric boundary layer over a forest canopy. It has been found that the wavelet method is slightly better than the VITA approach in coherent structure eduction, even if the results of both techniques are comparable. Also the application of the present approach to simultaneous conditionally sampled wind data has highlighted some important features of coherent structures and gust generation in canopy flows.     

Proterozoic fluvial styles: response to changes in accommodation space (Rivieradal sandstones, eastern North Greenland)

Fluvial styles recorded by the uppermost part of the Neoproterozoic ‘Rivieradal sandstones' succession of eastern North Greenland reflect variations in rate of generated accommodation space and possibly climatic changes. Three facies associations, arranged in two genetic sequences, are recognised within the succession. The lower sequence initially records little available accommodation space. A high degree of reworking results in sheet-like, high-energy, bed-load-dominated, braided river deposits lacking recurrent facies patterns. As accommodation space increases upwards through the sequence, reduction in reworking is recorded by the development of fining- and thickening-upward muddy fluvial cycles. Evidence of desiccation or prolonged periods of drought are absent within the deposits and climate was probably relatively humid. Channel deposits in the lower sequence reflect mixed-load, braided fluvial systems with stable channel banks and floodplains, and the gradient appears to have been low to moderate. These features are generally considered favourable for the establishment of meandering river systems, but channels, nevertheless, retained an overall braided character and their deposits show no evidence of meandering. Despite indications of a climatic setting without significant periods of drought sediments indicate that large fluctuations in discharge occurred within the mixed-load streams and this is suggested to be the main cause for the absence of meandering. The swift and rather dramatic response of the fluvial systems to changes in precipitation, probably resulted from rapid runoff rates caused by the absence of vegetation. The upper sequence shows an initial return to shallow, sandy braided river deposition recording little available accommodation space. A subsequent increase in the rate of generated accommodation space is indicated by the presence of alternating sheet sandstones and sand-streaked mudstones with abundant desiccation cracks. The sheet sandstones show evidence of high-energy, unconfined ephemeral fluvial flash-flood deposition, while the mudstones are interpreted to represent muddy floodplain deposits. The change in fluvial style, combined with the widespread evidence of desiccation, suggest an evolution towards a more semi-arid climate in the upper sequence. This climatic change could account for the reduced clastic input seen in the overlying marine succession which culminated in carbonate platform deposition. The present study suggests that even under conditions considered favourable for the formation of meandering streams, these will rarely occur in Proterozoic deposits due to the lacking influence of vegetation. Although meandering deposits cannot be ruled out as having formed in pre-vegetational times, the conditions for their formation appear to have been even more restricted than previously realised.     

On the global structure of self-gravitating discs for softened gravity

The effects of gravitational softening on the global structure of self-gravitating discs in centrifugal equilibrium are examined in relation to hydrodynamical/gravitational simulations. The one-parameter spline softening proposed by Hernquist & Katz is used.
It is found that if the characteristic size of a disc, r , is comparable to or less than the gravitational softening length, ε, then the cross-section of the simulated disc is significantly larger than that of a no-softening (Newtonian) disc with the same mass and angular momentum.
We demonstrate, furthermore, that if r ≲ε/2 then the scaling relation r ∝ε^3/4 holds for a given mass and specific angular momentum distribution with mass. Finally, we compare some of the theoretical results obtained in this paper and a previous one with the results of numerical Tree-SPH simulations and find qualitative agreement.     

False drainage anomalies (?) in a granite area, Kvalöya in Troms, Norway — a case study

An anomalous area (100 km²) revealed by a previous regional overbank sediment sampling survey by the Geological Survey of Norway was followed-up for Ti, Nb, Y, Zr, La and Ce by drainage and lithogeochemical sampling and analyses. The drainage samples were anomalous in the same elements as in the overbank samples and contained similar concentrations. The lithogeochemical results did not indicate mineralization and showed only a small enhancement of Ti, Zr, La and Ce in mylonitic rocks.Mineralogical studies of the drainage samples revealed, apart from proportions of quartz and feldspars, that stream sediments and heavy mineral concentrates are similar in mineralogy, with epidote predomination and several vol% of fine-grained titanite and zircon. Drainage samples contained amounts of Nb, Y, and Zr up to ten times larger than average contents of rock samples. Enhanced light REE (La and Ce) and Nb reflect host minerals, titanite, and enhanced Y possibly zircon and/or allanite.Anomalies in both media do not relate to mineralization. The overbank samples and the drainage samples provide comparable geochemical data.     

Preservation of pre-vegetational mixed fluvio–aeolian deposits in a humid climatic setting: an example from the Middle Proterozoic Eriksfjord Formation, Southwest Greenland

Sedimentological studies of a 30 m thick coastal cliff section within the Middle Proterozoic Eriksfjord Formation in western South Greenland reveals three distinct types of fluvial sand sheet deposits that reflect perennial streams (Type I), semi-perennial streams (Type II), and ephemeral flash floods (Type III). Perennial river sand sheets are characterised by co-sets of medium-scale trough cross-beds, interbedded with isolated medium- and large-scale, high-angle, tabular cross-beds. Indications of desiccation or subaerial exposure are absent. Semi-perennial fluvial sand sheets consist predominantly of low-angle cross-beds, interbedded with isolated sets of high-angle tabular cross-beds with common reactivation surfaces. Horizontal lamination and climbing ripple lamination form subordinate structures. Associated with the sand sheets are adhesion structures and 0.05–0.4 m thick sets of wind ripple-lamination indicating periods of subaerial exposure and aeolian reworking. High-energy ephemeral flash flood sand sheets consist almost exclusively of planar-parallel lamination and climbing ripple lamination with some isolated sets of low-angle cross-bedding. Scouring and internal truncation surfaces are common. The three types of sand sheets are considered to reflect deposition under changing climatic conditions, varying from humid to arid or semi-arid. Aeolian deposits are preserved within the sand sheets showing characteristics of dominantly perennial flow punctuated by shorter periods of desiccation (Type II), while sand sheets showing features typical of arid and or semi-arid flow conditions (Type III) contain no preserved aeolian deposits. This selective preservation is interpreted to be a result of the combined effect of groundwater table level and fluvial style which in turn are inferred to have been controlled by the climatic regime. The deposits show that during pre-vegetational times the preservation of aeolian deposits, under certain conditions, may be more optimal in fluvial systems formed in a humid climate than in fluvial systems formed under semi-arid or arid circumstances. The occurrence of aeolian deposits within a Precambrian succession of fluvial deposits therefore, need not be an indication of the most arid environmental conditions.