Effects of CO2 on benthic biota: An in situ benthic chamber experiment in Storfjorden (Norway)

Carbon capture and storage (CCS) methods, either sub-seabed or in ocean depths, introduces risk of CO₂ leakage and subsequent interaction with the ecosystem. It is therefore important to obtain information on possible effects of CO₂. In situ CO₂ exposure experiments were carried out twice for 10 days during 2005 using a Benthic Chamber system at 400 m depth in Storfjorden, Norway. pCO₂ in the water above the sediment in the chambers was controlled at approximately 500, 5000 and 20,000 μatm, respectively. This article describes the experiment and the results from measured the biological responses within the chamber sediments. The results show effects of elevated CO₂ concentrations on biological processes such as increased nanobenthos density. Methane production and sulphate reduction was enhanced in the approximately 5000 μatm chamber.     

Validation of a soil water balance model using soil water content and pressure head data

The validation of soil water balance models and the evaluation of the quality of the model predictions at field‐scale require time‐series of in situ measured model outputs. In our study, we have validated such a model using a 6‐year period with time‐series of automatically recorded, daily volumetric soil water contents measured with the time‐domain reflectometry with intelligent microelements (TRIME) method and daily pressure heads measured with tensiometers. The comparisons of simulated with measured soil water contents and pressure heads were analysed using the modelling efficiency index (IA) and the square root of the mean square error (RMSE) in order to evaluate the prediction quality of the model. In our study, IA and RMSE, obtained either from the comparison of simulated with measured soil water contents or the comparison of calculated with observed pressure heads, in some cases lead to different results regarding the evaluation of the simulation quality of the soil water balance model. For example, a good fit between simulated and observed soil water contents does not necessarily result in a comparably good fit between the corresponding calculated and measured pressure heads. Therefore, a combined use of both measurement techniques, which takes into account their respective advantages and disadvantages, gives a more complete overview on the simulation quality of the soil water balance model than the single use of one of those techniques. Copyright © 2004 John Wiley & Sons, Ltd.     

Das Kuriosum eines scheinbaren “Tidewindes” im Revier Außenelbe

Zusammenfassung Bei einer Auswertung der Windmessungen deutscher Feuerschiffe für die Sturmflut-Periode Mitte Februar 1962 fiel es auf, daß die Differenzen der Windgeschwindigkeit zwischen den Feuerschiffen Elbe 1 und Elbe 2 offenbar einem bestimmten Rhythmus unterlagen. Da der Abstand der meisten Maxima der Winddifferenz (Elbe 1 minus Elbe 2) etwa 12 Std. betrug, tauchte die Vermutung auf, daß dieser Rhythmus gezeitenbedingt war. Die Mittelbildung über 13 nach den Gezeiten geordnete Fälle ergab denn auch den Tidewind in ausgeprägter Form, wobei das relative Windmaximum von Elbe 1 bei Mitte Ebbstromzeit lag^** und der mittlere Schwankungsbetrag (Maximum — Minimum) 3.6 kn betrug. Eine auf die Gezeiten bezogenen Auswertung von Fällen quasikonstanter Windrichtung ergab noch größere Schwankungsbeträge und vor allem eine gegenläufige Schwingung des Tidewindes bei westlichen und östlichen Winden. Da dies Verhalten des Windes — nach Vorzeichen und Betrag — recht genau den differentiellen Schwankungen des Gezeitenstromes bei Elbe 1 und Elbe 2 entsprach, so hätte man an einen Mitführungseffekt des strömenden Wassers auf die Luft denken können, wäre nicht die ungeschwächte Übertragung von Bewegungsgröße bis in Anemometerhöhe von 18 m allzu unwahrscheinlich gewesen. Tatsächlich erlischt, wie E. R. Reiter [1955] zeigen konnte, der Mitführungseffekt bei einem Flusse ähnlicher Geschwindigkeit wie die Außenelbe in etwa 3 m Höhe über Wasser.Des Rätsels Lösung liegt in der kombinierten Wirkung des Gezeitenstroms und des Windes auf die Lage (Kielrichtung) der vor Anker schwojenden Feuerschiffe. Damit verändert sich im Verlauf einer Tide — bei konstanter Windrichtung — die Anblasrichtung der Schiffe, und diese Änderungen des Anströmungswinkels ergeben systematische Änderungen der gemessenen. Windgeschwindigkeit in Abhängigkeit von der Strömmungsstörung am Schiffshindernis. Die mit dem Gezeitenstrom schwojenden Feuerschiffe erscheinen so als ein geeignetes Versuchsobjekt zur besseren Feststellung des quantitativen störenden Schiffseinflusses auf den Wind.

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The strange phenomenon of an apparent tidal wind in the Estuary of the Outer Elbe (Außenelbe)

Summary When the wind measured by the German lightvessels for the storm surge period mid February 1962 was studied, it became obvious that the differences of wind velocities observed on the lightvessels Elbe 1 and Elbe 2 showed a certain rhythm. As most maxima of these wind differences (Elbe 1 minus Elbe 2) followed one another within about 12 hours, it was supposed that this rhythm was connected with the tide. The average of a series of 13 tides showed very remarkably the tidal wind, the maxima of the wind differences being at the centre of the ebbstream interval at Elbe 1 and the mean range of maximum-minimum being 3.6 kn. Cases of wind with quasi-constant directions showed even greater values of deviation when referred to the tide and, above all, deviations in opposite directions at easterly and westerly winds. As this phenomenon, in sign and quantity, very nearly corresponded to the differences of the tidal currents at Elbe 1 and Elbe 2, one could have thought of an effect by which air is carried along by the streaming water, if not, up to the height of the anemometer of 18 m, the unweakened transfer of momentum would have been too unlikely. In fact, as E. R. Reiter [1955] demonstrated, the effect of air being carried along by the streaming water fades out at about 3 m above the water level of a river at similar velocities as the Outer Elbe.The explanation of this phenomenon is the combined effect of the tidal current and the wind on the course of the lightvessels swinging round their anchors. At a constant direction of the wind, during one tide, the angle between wind and course varies and this variation of the angle leads to a systematic variation of the measured wind speed according to the disturbance caused by the ship as an obstacle. Therefore, lightvessels swinging round with the tidal current seem to be a suitable test to study how much the ship herself disturbs the wind.

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Aspect curieux d'un «vent de marée» apparent dans la zone de l'Elbe extérieure

Résumé A l'occasion d'une étude des vitesses du vent mesurées aux bateaux-feu au cours des ondes de tempête de mi-février 1962, on fit la remarque que les différences de vitesse du vent entre les bateaux-feu «Elbe 1» et «Elbe 2» paraissaient obéir à un certain rythme. Comme l'écart de la plupart des maxima de différence («Elbe 1» moins «Elbe 2») était d'environ 12 heures, il vint d'abord à l'esprit, que ce rythme était subordonné à la marée. La moyenne obtenue dans 13 cas pris dans l'ordre suivant la marée, faisait d'ailleurs apparaître nettement le «vent de marée» pour lequel le maximum relatif de «Elbe 1» correspondait au «milieu de la période de jusant» et la variation moyenne (maximum-minimum) se chiffrait à 3.6 noeuds. Une étude, rapportée à la marée, de cas de direction de vent quasi-constante, fit apparaître des variations encore plus grandes et surtout une oscillation en sens contraire du «vent de marée» par vents d'Ouest-d'Est. Comme ce comportement du vent-selon prévision et grandeur correspondait très exactement aux variations différentielles du courant de marée à «Elbe 1» et «Elbe 2», on aurait pu penser à un effet d'entraînement exercé sur l'air par le courant d'eau, si cet entraînement n'avait gardé la même force jusqu'à la hauteur de 18 m de l'anémomètre, ce qui était invraisemblable. En fait, comme l'a montré E. R. Reiter [1955] l'effet d'entraînement pour un fleuve d'une vitesse analogue à l'Elbe extérieure, cesse de se faire sentir à environ 3 m au-dessus de l'eau.Cette énigme trouve son explication dans l'action combinée du courant de marée et du vent sur la situation (direction de la quille) des bateaux-feu évitant sur leur ancre. C'est ainsi qu'au cours d'une marée-le vent gardant la même direction-le navire reçoit le vent sous des angles variables. Il en résulte des modifications systématiques de la vitesse de vent mesurée qui dépend de l'obstacle que le navire présente au courant d'air. Ainsi les bateaux-feu s'évitant au courant de marée semblent fournir un élément d'expérience approprié pour une meilleure détermination quantitative de l'influence perturbatrice du navire sur le vent.

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Herrn Prof. Dr. H. U. Roll zum 60. Geburtstag gewidmet.     

U.S. Mussel Watch: 1977–1978 results on trace metals and radionuclides

The results of the U.S. Mussel Watch Monitoring Program for the period 1976–1978 for trace metals and artificial radionuclides in bivalves are presented. The substances analysed included Ag, Cu, Zn, Cd, Ni, Pb, ²³⁸Pu, ^239+240Pu and ²⁴¹Am. The analyses of organic substances will be presented elsewhere. The concentrations of these substances in the bivalves may reflect upwelling processes, anthropogenic inputs or natural levels. Off the California coast, mussels show markedly elevated Pu and Cd concentrations in coastal areas adjacent to the most intensive upwelling zones. Elevated levels of Pb, for example, are found in organisms living adjacent to highly urbanized places. The general patterns of distribution repeat themselves year after year at a given site. Thus, it is concluded that annual monitoring activities may not be necessary and that a frequency of sampling of several or so years may be more appropriate to identify pollution problems. Finally, national or regional baselines for metal concentrations in bivalves from unpolluted waters are proposed. National baselines for Pb in the west coast mussels of 1·0 parts 10^?6 and for Ag in east coast mussels of 0·05 parts 10^?6 are suggested.     

Anisotropy of magnetic susceptibility variations in a single icelandic columnar basalt

Measurements of the anosotropy of magnetic susceptibility in 34 specimens drilled from a single Icelandic columnar basalt segment reveal a preferred, long-axis alignment of magnetic minerals normal to the long axis of the column and well grouped. Maximum elongation of these minerals occurs in regions which crystallized late, as independently indicated by relative samarium concentrations. We propose that the variations in magnetic mineral elongation are controlled by variations in thermal stress in the cooling column, before complete solidification. An upper limit of 75–100 bars is suggested for these stresses.     

Where Am I? Investigating Map Matching During Self‐Localization With Mobile Eye Tracking in an Urban Environment

Self‐localization is the process of identifying one's current position on a map, and it is a crucial part of any wayfinding process. During self‐localization the wayfinder matches visually perceptible features of the environment, such as landmarks, with map symbols to constrain potential locations on the map. The success of this visual matching process constitutes an important factor for the success of self‐localization. In this research we aim at observing the visual matching process between environment and map during self‐localization with real‐world mobile eye tracking. We report on one orientation and one self‐localization experiment, both in an outdoor urban environment. The gaze data collected during the experiments show that successful participants put significantly more visual attention to those symbols on the map that were helpful in the given situation than unsuccessful participants. A sequence analysis revealed that they also had significantly more switches of visual attention between map symbols and their corresponding landmarks in the environment, which suggests they were following a more effective self‐localization strategy.