Mass transport in rotatory tidal currents

Summary A perturbation method is used to calculate steady non-linear effects in rotatory tidal currents. The inclusion of the Coriolis acceleration leads to a uniquely determined second order current system in the tidal stream. This is shown to be absent in high frequency gravity waves. It is found that particle drift, or mass transport, is critically dependent on this mean current, and consequently on the value off/,f being the Coriolis parameter, and the angular frequency of the oscillation.     

Azimuth determination without circle readings

The technical aspects of azimuth determination in the vertical plane of the reference object are given. The programme preparation, field operations and computations of field data are described. The paper includes the results of experimental work close to the local meridian and near the prime vertical. Field operations and results are discussed.     

Gaschromatographisehe Untersuchung einiger Systeme aus Tonmineralien und organischen Stoffen

Gas chromatographic studies of simple organic -montmorillonite systems were carried out over the temperature range 40–90° C. Experimentally derived heats of absorption and relative activity coefficients indicate that the polar group of compounds studied exhibits organic-silicate interaction over the entire temperature range. The chromatographic separation of a group of non-polar hydrocarbons is most effective over the temperature range 40–70° C, when a layer of adsorbed water is present between silicate sheets. In this case organic-water interactions are important and the chromatographic separation is largely dependent upon relative solubility of hydrocarbons in the adsorbed water. Over the temperature range 70–90° C chromatographic separation of the hydrocarbons is effected by organic-silicate interactions in the absence of adsorbed water. It is suggested that these processes are in principle effective in natural sedimentary columns.

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Herrn Prof. Dr.Carl W. Correns zum 70. Geburtstag gewidmet.     

The impact of natural and anthropogenic forcings on climate and hydrology since 1550

A climate simulation of an ocean/atmosphere general circulation model driven with natural forcings alone (constant “pre-industrial” land-cover and well-mixed greenhouse gases, changing orbital, solar and volcanic forcing) has been carried out from 1492 to 2000. Another simulation driven with natural and anthropogenic forcings (changes in greenhouse gases, ozone, the direct and first indirect effect of anthropogenic sulphate aerosol and land-cover) from 1750 to 2000 has also been carried out. These simulations suggest that since 1550, in the absence of anthropogenic forcings, climate would have warmed by about 0.1 K. Simulated response is not in equilibrium with the external forcings suggesting that both climate sensitivity and the rate at which the ocean takes up heat determine the magnitude of the response to forcings since 1550. In the simulation with natural forcings climate sensitivity is similar to other simulations of HadCM3 driven with CO₂ alone. Climate sensitivity increases when anthropogenic forcings are included. The natural forcing used in our experiment increases decadal–centennial time-scale and large spatial scale climate variability, relative to internal variability, as diagnosed from a control simulation. Mean conditions in the natural simulation are cooler than in our control simulation reflecting the reduction in forcing. However, over certain regions there is significant warming, relative to control, due to an increase in forest cover. Comparing the simulation driven by anthropogenic and natural forcings with the natural-only simulation suggests that anthropogenic forcings have had a significant impact on, particularly tropical, climate since the early nineteenth century. Thus the entire instrumental temperature record may be “contaminated” by anthropogenic influences. Both the hydrological cycle and cryosphere are also affected by anthropogenic forcings. Changes in tree-cover appear to be responsible for some of the local and hydrological changes as well as an increase in northern hemisphere spring snow cover.

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Using moisture conservation to evaluate oceanic surface freshwater fluxes in climate models

We apply a diagnostic based on moisture conservation in the atmosphere, integrated over planetary-scale ocean basins and drainage areas to evaluate freshwater fluxes over the ocean surface to three generations of the Hadley Centre climate model (HadCM3, HadGEM1 and HadGEM2-AO). The coherent inclusion of runoff by the diagnostic enables model surface freshwater fluxes to be compared directly with observational estimates of precipitation, evaporation and river discharge. We also introduce a normalised metric, based on model-observation RMS differences, to assess the representation of the fluxes by the model. This methodology could be a powerful tool for evaluating model performance during future model development and model intercomparison exercises. Using this diagnostic, and defining the drainage areas from the global river routing model TRIP, we obtain large-scale surface oceanic fluxes from ERA40 and NCAR-NCEP reanalysis data, which we compare with analogous budgets computed from a set of individual observational estimates of evaporation, precipitation and river discharge. The sum of errors in the Hadley Centre climate model in all ocean basins suggests a steady improvement over the three generations of the model. However, an analysis of sources and sinks of water vapour shows common errors in the models, like an excess of evaporation in the tropical-subtropical Atlantic, and a surplus of water vapour export from tropical-subtropical areas to the mid-latitude regions, making the oceanic surface fluxes too fresh at mid latitudes. Errors in the models are consistent with an excessively strong hydrological cycle.     

Climate change under aggressive mitigation: the ENSEMBLES multi-model experiment

We present results from multiple comprehensive models used to simulate an aggressive mitigation scenario based on detailed results of an Integrated Assessment Model. The experiment employs ten global climate and Earth System models (GCMs and ESMs) and pioneers elements of the long-term experimental design for the forthcoming 5th Intergovernmental Panel on Climate Change assessment. Atmospheric carbon-dioxide concentrations pathways rather than carbon emissions are specified in all models, including five ESMs that contain interactive carbon cycles. Specified forcings also include minor greenhouse gas concentration pathways, ozone concentration, aerosols (via concentrations or precursor emissions) and land use change (in five models). The new aggressive mitigation scenario (E1), constructed using an integrated assessment model (IMAGE?2.4) with reduced fossil fuel use for energy production aimed at stabilizing global warming below 2?K, is studied alongside the medium-high non-mitigation scenario SRES A1B. Resulting twenty-first century global mean warming and precipitation changes for A1B are broadly consistent with previous studies. In E1 twenty-first century global warming remains below 2?K in most models, but global mean precipitation changes are higher than in A1B up to 2065 and consistently higher per degree of warming. The spread in global temperature and precipitation responses is partly attributable to inter-model variations in aerosol loading and representations of aerosol-related radiative forcing effects. Our study illustrates that the benefits of mitigation will not be realised in temperature terms until several decades after emissions reductions begin, and may vary considerably between regions. A subset of the models containing integrated carbon cycles agree that land and ocean sinks remove roughly half of present day anthropogenic carbon emissions from the atmosphere, and that anthropogenic carbon emissions must decrease by at least 50% by 2050 relative to 1990, with further large reductions needed beyond that to achieve the E1 concentrations pathway. Negative allowable anthropogenic carbon emissions at and beyond 2100 cannot be ruled out for the E1 scenario. There is self-consistency between the multi-model ensemble of allowable anthropogenic carbon emissions and the E1 scenario emissions from IMAGE?2.4.     

The Equatorial Undercurrent in the central Atlantic and its relation to tropical Atlantic variability

Seasonal to interannual variations of the Equatorial Undercurrent (EUC) in the central Atlantic at 23°W are studied using shipboard observation taken during the period 1999–2011 as well as moored velocity time series covering the period May 2005–June 2011. The seasonal variations are dominated by an annual harmonic of the EUC transport and the EUC core depth (both at maximum during September), and a semiannual harmonic of the EUC core velocity (maximum during April and September). Substantial interannual variability during the period of moored observation included anomalous cold/warm equatorial Atlantic cold tongue events during 2005/2008. The easterly winds in the western equatorial Atlantic during boreal spring that represent the preconditioning of cold/warm events were strong/weak during 2005/2008 and associated with strong/weak boreal summer EUC transport. The anomalous year 2009 was instead associated with weak preconditioning and smallest EUC transport on record from January to July, but during August coldest SST anomalies in the eastern equatorial Atlantic were observed. The interannual variations of the EUC are discussed with respect to recently described variability of the tropical Atlantic Ocean.     

Illite diagenesis in the Vienna Basin,Austria

Summary The fine clay fractions less than 0.2 micron isolated from Tertiary shales of the Vienna Basin, Austria, were characterized mineralogically and chemically (including c.e.c.). Over the depth (885–2802 m) and temperature (45–120 °C) intervals represented mixed layer smectite-illites change from 74/26 to 20/80, the deeper samples showing IM ordering. Inhibition of illitization at about 2700 m is attributed to unusually high Mg content of pore solutions at this depth.Utilizing a chemical-statistical approach, the illite component of each smectite-illite mixed-layer phase has been characterized as to magnitude of interlayer charge, and octahedral and tetrahedral substitutions. The illite compositions fall neatly within the normal illite field defined by Köster.During the initial stage of illitization, smectite to illite transformation proceeds toward phengitic compositions. As illitization continues (greater depth and T), the illite component progressively changes composition with loss of Mg toward that of ideal 50/50 allevardite.

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Illit-Diagenese im Wiener Becken

Zusammenfassung Feintonproben (kleiner 0,2 Mikron) aus neogenen pelitischen Sedimenten aus dem Wiener Becken wurden mineralogisch und chemisch (einschließlich Ionenaustauschkapazität charakterisiert. Die im Teufenbereich zwischen 885–2802 m und Temperature zwischen 45–120 °C angetroffenen Smektit-Illit Mischphasen haben eine Zusammensetuzung von 74/26 bis 20/80, wobei im untersten Teufenbereich IM-Entwicklung vorliegt. Eine verzögerte Illitisierung bei ca. 2700 m wird lokal ungewöhnlich hohen Mg-Konzentrationen der Porenwässer zugeschrieben.Durch Anwendung eines chemisch-statistischen Näherungsverfahrens konnte die illitische Komponente der Smektit-Illit Mischphasen hinsichtlich Zwischenschichtladung sowie oktaedrischen und tetraedrischen Substitutionen charakterisiert werden. Die Zusammensetzungen der Illite liegen innerhald des Illitfeldes nach Köster.Die Umformung Smektit zu Illit zeigt außerdem zu Beginn des Illitisierungsprozesses phengitische Zusammensetzungen der Phasen. Mit zunehmender Tiefe und Temperatur ist weiterhin eine Neubildung von Allevardit zu beobachten.

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With 12 Figures