Distribution of chlorophyll a and diatom in the sea ice of the Weddell Sea, Antarctica

Diatoms are major primary producers of microbial biomass in the Antarctica. They are found in the water and sea ice. The distribution, abundance of the ice diatoms and their relation to the environmental factors inside and outside the ice have been studied for its special role in the Antarctic Ocean ecology. In this paper we describe the abundance, distribution and composition of diatom assemblages in     

Distribution and temporal variation of mega‐fauna at the Regab pockmark (Northern Congo Fan), based on a comparison of videomosaics and geographic information systems analyses

The Regab pockmark is a large cold seep area located 10 km north of the Congo deep sea channel at about 3160 m water depth. The associated ecosystem hosts abundant fauna, dominated by chemosynthetic species such as the mussel Bathymodiolus aff. boomerang, vestimentiferan tubeworm Escarpia southwardae, and vesicomyid clams Laubiericoncha chuni and Christineconcha regab. The pockmark was visited during the West African Cold Seeps (WACS) cruise with RV Pourquoi Pas? in February 2011, and a 14,000‐m² high‐resolution videomosaic was constructed to map the most populated area and to describe the distribution of the dominant megafauna (mussels, tubeworms and clams). The results are compared with previous published works, which also included a videomosaic in the same area of the pockmark, based on images of the BIOZAIRE cruise in 2001. The 10‐year variation of the faunal distribution is described and reveals that the visible abundance and distribution of the dominant megafaunal populations at Regab have not changed significantly, suggesting that the overall methane and sulfide fluxes that reach the faunal communities have been stable. Nevertheless, small and localized distribution changes in the clam community indicate that it is exposed to more transient fluxes than the other communities. Observations suggest that the main megafaunal aggregations at Regab are distributed around focused zones of high flux of methane‐enriched fluids likely related to distinct smaller pockmark structures that compose the larger Regab pockmark. Although most results are consistent with the existing successional models for seep communities, some observations in the distribution of the Regab mussel population do not entirely fit into these models. This is likely due to the high heterogeneity of this site formed by the coalescence of several pockmarks. We hypothesize that the mussel distribution at Regab could also be controlled by the occurrence of zones of both intense methane fluxes and reduced efficiency of the anaerobic oxidation of methane possibly limiting tubeworm colonization.     

Methane exchange between coal-bearing basins and the atmosphere: the Ruhr Basin and the Lower Rhine Embayment, Germany

A precise knowledge of methane exchange processes is required to fully understand the recent rise of atmospheric methane concentration. Three of these processes take place at the lithosphere/atmosphere boundary: bacterial consumption of methane and emission of bacterial or thermogenic methane. This study was initiated to quantify these processes on a regional scale in the Ruhr Basin and the Lower Rhine Embayment. Since these areas are subject to bituminous coal and lignite mining, natural and anthropogenically-induced methane exchange processes could be studied. The methane emission and consumption rates and their carbon isotope signal were measured at the lithosphere/atmosphere boundary using flux chambers. On most of the soils studied, methane consumption by bacteria was identified. Thermogenic methane was released only at some of the natural faults examined. In active and abandoned bituminous coal mining areas methane emissions were restricted to small areas, where high emission rates were measured. The carbon isotope composition of methane at natural faults and in mining subsidence troughs was typical of thermogenic methane (−45 to −32 ‰ δ¹³C). Methane exchange balancing revealed that natural methane emissions from these two basins represent no source of atmospheric importance. However, methane release by upcast mining shafts dominates the methane exchange processes and is by about two orders of magnitude greater than methane consumption by bacterial oxidation in the soils.     

Über die komplexe Natur des Seeganges

Zusammenfassung Unter der Annahme, daß der Seegang nacheinander drei Hauptentwicklungsstufen durchläuft, bis er voll ausgereift ist, lassen sich Beziehungen zwischen den charakteristischen Wellengrößen, der Windgeschwindigkeit, der Wellenlaufstrecke und der Zeitdauer der Windeinwirkung ableiten. Diese Beziehungen sind in graphischer Form für die praktische Seegangsvorhersage dargestellt. Sie gestatten u. a. die Vorausbestimmung der mittleren Periode, d. h. des Mittelwertes der Zeitintervalle zwischen aufeinanderfolgenden Wellenkämmen an einem festen Ort, der häufigsten Periode, der Breite des Periodenspektrums sowie der mittleren und maximalen Wellenhöhe.

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On the complexity of wind waves — 2^nd part: The growth of waves under the wind's influence

Summary Proceeding from the supposition that wind generated waves have to pass through three principal stages before they will be fully developed, one may establish relations between wind velocity, fetch, duration of wind action, and the characteristic wave dimensions. Graphical representations of these relations are given for the practice of wave forecasting. Among others, they allow to predict the mean period, i. e. the mean value of the time intervals between the passage of successive wave crests at a given point, the most frequent period and the width of the spectrum of periods as well as the mean and maximum wave heights.

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La nature complexe des vagues de vent- 2^ième partie: Accroissement des vagues sous l'effect du vent

Résumé En supposant que les vagues de vent doivent parcourir trois phases principales pour atteindre les maxima de leurs dimensions et de leur force on peut établir des relations entre la vitesse du vent, le fetsch, la durée de l'action du vent et les dimensions caractéristiques des vagues. Pour les besoins de la prévision pratique des vagues de vent on a établi des représentations graphiques de ces relations qui permettent entre autres de prévoir la période moyenne, c'est à dire de prévoir la moyenne des intervalles de temps entre le passage par un point donné des crêtes des vagues consécutives, la période la plus fréquence, la largeur du spectre de la période et les moyennes et maxima des hauteurs des vagues.

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Aus den Arbeiten des Department of Meteorology and Oceanography an der New York University für das Office of Naval Research, Washington, D. C., unter Contract No. Nonr — 285(05).     

Der Einfluß der Küstengestalt und des vorgelagerten Meeresbodens auf den windbedingten Anstau des Wassers,betrachtet am Beispiel der Westküste Schleswig-Holsteins

Zusammenfassung Die Einwirkung des Windes auf den Wasserstand bei Hochwasser entlang der deutschen Nordseeküste ist im allgemeinen verschieden. Die Gründe hierfür sind der ungleichmäßige Küstenverlauf und das von zahlreichen Prielen durchzogene flache Küstenvorland. Ausführliche Methoden zur Vorausberechnung des Windstaus unter Beachtung dieser morphologischen Bedingungen liegen noch nicht vor. Es wird deshalb ein Verfahren vorgeschlagen, den Windstau entlang der Küste im Anschluß an den Windstau eines geeigneten Bezugsortes zu bestimmen. Am Beispiel von acht Häfen der schleswig-holsteinischen Westküste wird gezeigt, daß dies mit gutem Erfolg möglich ist. Es wird eine Tabelle vorgelegt, die nach diesem Vorschlag beim Deutschen Hydrographischen Institut berechnet wurde und seit einiger Zeit für die Wasserstandsvorhersagen im Windstau- und Sturmflutwarndienst dieses Institutes verwendet wird. Die Tabelle enthält den Windstauunterschied der acht Orte gegen Cuxhaven in Abhängigkeit von Windrichtung und -stärke. Der Einfluß des Windes auf den Wasserstand wird für die Häfen einzeln besprochen. Die Untersuchung des Verhaltens der Häfen untereinander führt zur Aufstellung von sogenannten Normalgefällen. Abschließend werden Betrachtungen über die Genauigkeit des Verfahrens, die sich als befriedigend ergibt, angestellt.

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The influence exercised by the coast's shape and the topography of the tidal flats on the piling up of water due to stress of wind, exemplified by the conditions on the coast of Schleswig-Holstein

Summary The influences exercised by the wind on the water level at high water along the German North Sea coast show, in general, great differences which are due to the irregular coast line and the tidal flats with their numerous transversal tideways. Detailed methods of forecasting the piling up of water which take into consideration this sort of morphological conditions are so far not developed. Therefore, a method is proposed which permits to determine the piling up of water along the coast by relating it to the piling up at a suitable port of reference. Eight ports on the coast of Schleswig-Holstein are chosen as examples; they show that good results will be obtained from this method. A table is submitted which has been calculated by the German Hydrographic Institute in accordance with this proposal and which is used for the prediction of water level by the Storm Surge Warning Service of this institute. The table includes the difference in height of the piling up phenomenon at the eight places as compared with the data obtained at the port of Cuxhaven as a function of direction and strength of wind. The wind's influence on the water level at the different ports is discussed in detail. The behaviour of the eight ports is studied and a list of normal gradients is drawn up. In conclusion, the accuracy of the method is considered and is found to be satisfactory.

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L'influence de la configuration de la côte et des bas-fonds sur la montée du niveau due à la pression du vent, phénomène étudié à l'exemple de la côte du Schleswig-Holstein

Résumé La montée du niveau de la mer à l'époque de la pleine mer qui est causée par le vent subit, en général, des variations tout le long de la côte allemande de la mer du Nord. Les causes en sont le contour irrégulier de la côte et les bas-fonds traversés par beaucoup de petits chenaux de marée. Il n'existe pas encore de méthodes précises qui permettent à la fois de prédire la montée du niveau en tenant compte de ces conditions morphologiques. Donc, pour déterminer la montée du niveau le long de la côte, l'auteur propose un procédé qui se base sur la montée de niveau dans un port de référence convenable. A l'exemple de huit ports sur la côte d'ouest du Schleswig-Holstein, il montre que ce procédé donne de bons résultats. Une table est présentée qui fut calculée à l'Institut Hydrographique Allemand en conformité de cette proposition et qui y est employée depuis quelque temps pour les prévisions quotidiennes du niveau de la mer. La table contient les différences en montée du niveau entre les huit ports et le port de Cuxhaven en fonction de la direction et de la force du vent. L'influence du vent sur le niveau d'eau de chacun de ces huit ports est discutée. Le comportement des huit ports est étudie et il en résulte une table de gradients normaux. Enfin, l'auteur considère la précision du procédé qu'il trouve satisfaisante.

     

A forced response to twentieth century climate conditions of two Spanish forests inferred from widths and stable isotopes of tree rings

This dendroclimatological research is based on two close pine forests (Pinus sylvestris and Pinus uncinata) located at the Northern Iberian System (Spain), and three tree-ring variables (ring widths, δ ¹³C and δ ¹⁸O). The climate-tree growth system was assessed at local and regional scales using three climate datasets. Calibration of tree-ring records with climate showed a diversity of information recorded in the different variables, such as a general response to temperature and precipitation of current growing period, and an important contribution of previous year conditions understood as the use of food reserves. The analysis of the stability of climate-tree growth relationships throughout the twentieth century showed a shift of those climatic variables to which trees responded and results suggested an enhancement of reserve use on current tree growth. The results obtained in this research made clear a physiological adaptation of trees to changing climate. The results provided hints that the recent warming coupled to slight precipitation decay are forcing growth of studied trees to a higher stress status and to a higher climate-growth synchronisation. These instabilities also have implications on future dendroclimatic reconstructions performed with trees growing under changing environments.