Spatial characteristics of ocean surface waves

The spatial variability of open ocean wave fields on scales of O (10km) is assessed from four different data sources: TerraSAR-X SAR imagery, four drifting SWIFT buoys, a moored waverider buoy, and WAVEWATCH III^? model runs. Two examples from the open north-east Pacific, comprising of a pure wind sea and a mixed sea with swell, are given. Wave parameters attained from observations have a natural variability, which decreases with increasing record length or acquisition area. The retrieval of dominant wave scales from point observations and model output are inherently different to dominant scales retrieved from spatial observations. This can lead to significant differences in the dominant steepness associated with a given wave field. These uncertainties have to be taken into account when models are assessed against observations or when new wave retrieval algorithms from spatial or temporal data are tested. However, there is evidence of abrupt changes in wave field characteristics that are larger than the expected methodological uncertainties.     

Holocene peatland development and hydrological variability inferred from bog‐pine dendrochronology and peat stratigraphy – a case study from southern Sweden

Dendrochronological analysis was applied to subfossil remains of Scots pine (Pinus sylvestris L.) buried in a South Swedish peat deposit. In combination with peat stratigraphy, this approach was explored for its potential to provide information on the local hydrological and depositional history at the site, forming the basis for a regional palaeohydrological analysis. A 726‐year ring‐width chronology was developed and assigned an absolute age of 7233–6508 cal a BP (5284–4559 BC) through cross‐dating with German bog‐pine chronologies, whereas two short additional records of older ages were radiocarbon dated. Registration of growth positions of individual trees allowed assessment of the spatial dynamics of the pine population in response to hydrological changes and peatland ontogeny. Annually resolved growth variability patterns in the pine population reveal several establishment and degeneration phases, probably reflecting fluctuations in bog‐surface wetness. A major establishment phase at 7200–6900 cal a BP reflects the onset of a period of lowered groundwater level, also indicated by increased peat humification, and a development consistent with regional temperature and lake level reconstructions revealed from other proxies. This study demonstrates that subfossil bog‐pine populations may provide annually to decadally resolved reconstructions of local groundwater variability, which are highly relevant in a long‐term palaeoclimatic context. Copyright © 2012 John Wiley & Sons, Ltd.     

Ternary feldspars: Kinetics and possible equilibria at 800° C

The ternary feldspar system KAlSi₃O₈ - NaAlSi₃O₈ - CaAl₂Si₂O₈ was reinvestigated at 650 ° C and 800 ° C (P _H2O = 1 kb) using mixtures of crystalline plagioclases and alkali feldspars as starting materials. The compositions of plagioclases and alkali feldspars of the run products were determined by X-ray means. The Or-content of the feldspar phases was determined by measuring the position of the (201) X-ray peak of the unexchanged feldspars, whereas the An-content was determined by measuring the same X-ray peak of the K-exchanged feldspars. The reaction rate of a reaction leading to a more An-rich plagioclase (type II reaction) is much faster than a reaction producing a more Ab-rich plagioclase (type I). In a type II reaction run times of approximately 20 days are needed to reach new constant plagioclase and alkali feldspar compositions at 650 ° C, and 10 days are needed to reach constant compositions at 800 ° C. In a reaction of type I only the outer zone of the plagioclases reacts to more Abrich compositions. A diffuse zone with a wide range of compositions was observed in 650 ° C runs. Equilibrium could not be reached in these experiments within 45 days. At 800 ° C a new zone having a specific composition develops in 42 days. This new zone is believed to be in equilibrium with the coexisting alkali feldspar. The depth of reaction is calculated as 0.03 μm after 42 days (800 ° C, P _f= 1 kb). The reaction between the two feldspar phases could be reversed at 800 ° C. The following compositions are considered to represent equilibrium data at 800 ° C and P _t = 1 kb:

An 43 Ab 51 Or 6 coexisting with Or 79 Ab 20 An 1, and

An 40 Ab 54 Or 6 coexisting with Or 75 Ab 24 An 1.

Recent data obtained with gels of ternary feldspar composition as starting materials do not agree with the results presented in this paper. Gels obviously crystallize spontaneously forming coexisting feldspars of non - equilibrium composition - alkali feldspars too rich in Ab and plagioclases too rich in An.     

Oil prices and energy technology innovation: An empirical analysis

To achieve environmental sustainability and reduce their vulnerability to oil shocks, countries can develop new energy technologies. Technological advances reduce the cost of structural changes in the energy economy, and thus also increase the political feasibility of such changes. But what explains international variation in the form and quality of energy technology innovation? We build on previous theories and offer an integrated account: increasing oil prices reinforce existing sectoral innovation systems, both politically and economically, thus allowing public policymakers and private entrepreneurs to profitably invest in new energy technologies. We test this theoretical argument against data on public R&D expenditures and patents in the domain of renewable energy technology for industrialized countries from 1989 to 2007. We find strong support for the interactive hypothesis. Thus, we contribute to literatures on (i) domestic responses to international shocks, (ii) environmental sustainability and energy security, and (iii) the political economy of technology innovation.     

Tracing variability of run‐off generation in mountainous permafrost of semi‐arid north‐eastern Mongolia

The headwaters of mountainous, discontinuous permafrost regions in north‐eastern Mongolia are important water resources for the semi‐arid country, but little is known about hydrological processes there. Run‐off generation on south‐facing slopes, which are devoid of permafrost, has so far been neglected and is totally unknown for areas that have been affected by recent forest fires. To fill this knowledge gap, the present study applied artificial tracers on a steppe‐vegetated south‐facing and on two north‐facing slopes, burned and unburned. Combined sprinkling and dye tracer experiments were used to visualize processes of infiltration and water fluxes in the unsaturated zone. On the unburned north‐facing slope, rapid and widespread infiltration through a wet organic layer was observed down to the permafrost. On the burned profile, rapid infiltration occurred through a combusted organic and underlying mineral layer. Stained water seeped out at the bottom of both profiles suggesting a general tendency to subsurface stormflow (SSF). Ongoing SSF could directly be studied 24 h after a high‐intensity rainfall event on a 55‐m hillslope section in the burned forest. Measurements of water temperature proved the role of the permafrost layer as a base horizon for SSF. Repeated tracer injections allowed direct insights into SSF dynamics: A first injection suggested rather slow dispersive subsurface flow paths; whereas 18 h later, a second injection traced a more preferential flow system with 20 times quicker flow velocities. We speculate that these pronounced SSF dynamics are limited to burned slopes where a thermally insulating organic layer is absent. On three south‐facing soil profiles, the applied tracer remained in the uppermost 5 cm of a silt‐rich mineral soil horizon. No signs of preferential infiltration could be found, which suggested reduced biological activity under a harsh, dry and cold climate. Instead, direct observations, distributed tracers and charcoal samples provided evidence for the occurrence of overland flow. Copyright © 2014 John Wiley & Sons, Ltd.     

Debating clean energy: Frames,counter frames,and audiences

In the United States, both scholars and practitioners have repeatedly emphasized the importance of “issue framing” for garnering public support for climate change policy. However, the debate frequently overlooks the importance of counter frames. For every framing attempt by advocates of climate policy, there will be a counter frame by the opponents of climate policy. How do counter frames influence the effectiveness of issue framing as a communication strategy? To answer this question, we report results from a survey experiment on a nationally representative sample of 1000 Americans on clean energy policy, a key policy issue in the public debate on climate change in the United States. Overall, we find that different combinations of positive and negative frames have remarkably little effect on support for clean energy policy. A follow-up on-line survey experiment with a convenience sample of 2000 Americans suggests that the counter frames are responsible for undermining the effects of the original frames.     

Troposphere gradients from the ECMWF in VLBI analysis

Modeling path delays in the neutral atmosphere for the analysis of Very Long Baseline Interferometry (VLBI) observations has been improved significantly in recent years by the use of elevation-dependent mapping functions based on data from numerical weather models. In this paper, we present a fast way of extracting both, hydrostatic and wet, linear horizontal gradients for the troposphere from data of the European Centre for Medium-range Weather Forecasts (ECMWF) model, as it is realized at the Vienna University of Technology on a routine basis for all stations of the International GNSS (Global Navigation Satellite Systems) Service (IGS) and International VLBI Service for Geodesy and Astrometry (IVS) stations. This approach only uses information about the refractivity gradients at the site vertical, but no information from the line-of-sight. VLBI analysis of the CONT02 and CONT05 campaigns, as well as all IVS-R1 and IVS-R4 sessions in the first half of 2006, shows that fixing these a priori gradients improves the repeatability for 74% (40 out of 54) of the VLBI baseline lengths compared to fixing zero or constant a priori gradients, and improves the repeatability for the majority of baselines compared to estimating 24-h offsets for the gradients. Only if 6-h offsets are estimated, the baseline length repeatabilities significantly improve, no matter which a priori gradients are used.     

Nitrogen isotopes in the solar system

Measurements of the isotopic composition of nitrogen in the solar system are summarized. We show that the 30% change, during the last 3 to 4 billion years, of ${}^{15}\text{N}{}^{14}\text{N}$ in solar-wind-bearing lunar soils and breccias probably does not reflect changes in this ratio at the solar surface. Such changes, whether by spallation or thermonuclear reactions are ruled out by comparing the yields of ¹⁵N with those of other rare isotopes such as ⁹Be, ¹¹B, ³He or ¹³C, even if an arbitrary degree of solar mixing is introduced. Moreover, we calculate that the solar activity required for producing significant amounts of ¹⁵N by spallation at the solar surface should have resulted in a particle bombardment of the Moon of an intensity that would have produced amounts of spallation isotopes (e.g.¹⁵N, ²¹Ne, ³⁸Ar, ¹³¹Xe) several orders of magnitude in excess of what is actually found in the whole regolith.We argue that accretion of interstellar matter also does not work as a cause for a significant change of the photospheric ${}^{15}\text{N}{}^{14}\text{N}$ ratio. Evidence is presented that the mixing depth at the solar surface on a time scale of ?10⁹ years is (10^?2 ?10^?1) M_⊙ Mixing to this depth renders accretion of interstellar matter as a source of compositional changes at the solar surface inefficient, even if allowance is made for the expected large difference in the accretion rates of condensed and gaseous matter. A quantitative treatment of several alternatives of solar accretion leads to serious contradictions (e.g. with the low Ne abundances in planetary atmospheres or with the amounts of nitrogen that should have been directly accreted by the Moon), and we conclude that accretion during the main sequence life of the Sun is an unlikely source of changes in ${}^{15}\text{N}{}^{14}\text{N}$ at the solar surface.A ratio of ${}^{15}\text{N}{}^{14}\text{N}\text{= (4.0 ± 0.3) × 10}{}^{\mathrm{?3}}$ is our best estimate for average solar system material and for the Sun. We propose that a rare, very light nitrogen component (called LPN) is admixed in varying amounts to planetary matter. Undiluted LPN has not been found in meteorites or planetary atmospheres, but we show that the combined effects of LPN admixture and isotope fractionation can in principle account for the variability of ${}^{15}\text{N}{}^{14}\text{N}$ observed in the planetary system. Determination of the Jovian ${}^{15}\text{N}{}^{14}\text{N}$ ratio with an accuracy of ~10% would crucially test our interpretation of the nitrogen isotope observations.     

An Eocene/Oligocene blueschist‐/greenschist facies P–T loop from the Cycladic Blueschist Unit on Naxos Island,Greece: Deformation‐related re‐equilibration vs. thermal relaxation

Geothermobarometric and geochronological work indicates a complete Eocene/early Oligocene blueschist/greenschist facies metamorphic cycle of the Cycladic Blueschist Unit on Naxos Island in the Aegean Sea region. Using the average pressure–temperature (P–T) method of thermocalc coupled with detailed textural work, we separate an early blueschist facies event at 576 ± 16 to 619 ± 32°C and 15.5 ± 0.5 to 16.3 ± 0.9 kbar from a subsequent greenschist facies overprint at 384 ± 30°C and 3.8 ± 1.1 kbar. Multi‐mineral Rb–Sr isochron dating yields crystallization ages for near peak‐pressure blueschist facies assemblages between 40.5 ± 1.0 and 38.3 ± 0.5 Ma. The greenschist facies overprint commonly did not result in complete resetting of age signatures. Maximum ages for the end of greenschist facies reworking, obtained from disequilibrium patterns, cluster near c. 32 Ma, with one sample showing rejuvenation at c. 27 Ma. We conclude that the high‐P rocks from south Naxos were exhumed to upper mid‐crustal levels in the late Eocene and early Oligocene at rates of 7.4 ± 4.6 km/Ma, completing a full blueschist‐/greenschist facies metamorphic cycle soon after subduction within c. 8 Ma. The greenschist facies overprint of the blueschist facies rocks from south Naxos resulted from rapid exhumation and associated deformation/fluid‐controlled metamorphic re‐equilibration, and is unrelated to the strong high‐T metamorphism associated with the Miocene formation of the Naxos migmatite dome. It follows that the Miocene thermal overprint had no impact on rock textures or Sr isotopic signatures, and that the rocks of south Naxos underwent three metamorphic events, one more than hitherto envisaged.