Die Anomalie der Wassertemperatur und der Zirkulation im Nordpazifischen Ozean und an der Küste Perus im Jahre 1955

Zusammenfassung Die Anomalien der Wassertemperatur des Nordpazifik im Jahre 1955 stehen offensichtlich in Verbindung mit einer ausgeprägten Anomalie der atmosphärischen Zirkulation. Als Beleg dafür wird die Karte der mittleren Luftdruckabweichung 1955 gebracht. Anschließend werden die Verhältnisse an der peruanischen Küste besonders behandelt. Das Kaltwasser-Jahr 1955 war hier besonders ausgeprägt, war allerdings nur das Zentraljahr einer dreijährigen kalten Periode. Übernormale Windstärke (im Südostpassat) deutet auch hier auf eine Anomalie der atmosphärischen Zirkulation als Ursache der Erscheinung. Abschließend wird die langjährige Wassertemperatur-Reihe von Puerto Chicama (Peru) mitgeteilt.

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Some notes on the anomalies of sea surface temperatures and of atmospheric circulation observed in the north pacific ocean and on the coast of peru in 1955

Summary The anomalies of sea surface temperature observed in the North Pacific Ocean during the year of 1955 are, evidently associated with a pronounced anomaly of atmospheric circulation. A map showing the mean deviation of atmospheric pressure gives evidence of these correlations. The conditions on the coast of Peru is given special consideration. The cold-water-year 1955 is strongly marked, though being only the coldest year in a three years' period of low sea surface temperatures. Above-normal windforces associated with the south-east trade wind indicate that also here the cause of the phenomenon is to be sought in an anomaly of atmospheric circulation. At the end of the paper, a some thirty years' series of sea surface temperature observations from Puerto Chicama (Peru) is given.

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Notes sur les anomalies de la température des eaux superficielles et de la circulation atmosphérique dans l'océan Pacifique Nord et sur la côte du Pérou en 1955

Résumé Les anomalies de la température des eaux superficielles se sont évidemment trouvées être associées à des anomalies prononcées de la circulation atmosphérique. La carte de l'écart moyen de la pression atmosphérique en 1955, ci-inclus, en fait preuve. Les conditions rencontrées sur la côte du Pérou font l'objet d'une étude spéciale. L'année de 1955 qui montra des températures particulièrement basses n'était, cependant, que l'année la plus froide de trois années successives aux températures basses. La force anormale par excès du vent (associée aux alizés du sud-est) y indique, elle aussi, que l'anomalie de la circulation atmosphérique est la cause de ce phénomène. Une série d'observations de la température des eaux effectuée à Puerto Chicama (Pérou) pendant la période de 1925 à 1957 se trouve dans le tableau 12 à la fin de ce travail.

     

Dynamics of stationary wave anomalies during the 1986/87 El Niño

The dynamics of the wintertime atmospheric response to the 1986/87 El Niño SST anomalies is studied. A GCM used for this purpose simulates a wave train over the Pacific/North American (PNA) region that agrees closely in amplitude with that observed, but phase shifted 30° to the east. Linear baroclinic model experiments are performed in order to determine the origin of the GCM and observed stationary wave anomalies, with particular focus on the cause for GCM failure. Diagnostics with the linear model reveal that the GCM and observed wave train anomalies are maintained by very different processes. In the GCM, the forcing due to tropical diabatic heating and transient vorticity fluxes are equally important over the PNA region. In the observations, the transient vorticity fluxes assume the primary role. The cause for these discrepancies is traced to the different dynamic influences of suppressed rainfall near Indonesia. The associated diabatic cooling is found to excite a large amplitude wave train over the PNA region in the GCM, while no significant extratropical response to cooling is found in the observations. The combined effects of the diabatic cooling and the reorganization of the storm track transients by the remotely forced wave train acts to shift the GCM's wave train well to the cast of that observed. Due to uncertainties in the observed diabatic forcing, however, it is not clear to what extent the GCM's failure is due to errors in the simulated anomalous forcing and/or to the GCM's mean climate error.This paper was presented at the Second International Conference of Modelling on Global Climate Variability, held in Hamburg 7–11 September 1992 under the auspices of the Max Planck Institute for Meteorology. Guest Editor for these papers is L. Dümenil Correspondence to: M Ting     

AMS radiocarbon dating and varve chronology of Lake Soppensee: 6000 to 12000 14C years BP

For the extension of the radiocarbon calibration curve beyond 10000 ¹⁴C y BP, laminated sediment from Lake Soppensee (central Switzerland) was dated. The radiocarbon time scale was obtained using accelerator mass spectrometry (AMS) dating of terrestrial macrofossils selected from the Soppensee sediment. Because of an unlaminated sediment section during the Younger Dryas (10000–11000 ¹⁴C y BP), the absolute time scale, based on counting annual layers (varves), had to be corrected for missing varves. The Soppensee radiocarbon-verve chronology covers the time period from 6000 to 12000 ¹⁴C y BP on the radiocarbon time scale and 7000 to 13000 calendar y BP on the absolute time scale. The good agreement with the tree ring curve in the interval from 7000 to 11450 cal y BP (cal y indicates calendar year) proves the annual character of the laminations. The ash layer of the Vasset/Killian Tephra (Massif Central, France) is dated at 8230±140 ¹⁴C y BP and 9407±44 cal y BP. The boundaries of the Younger Dryas biozone are placed at 10986±69 cal y BP (Younger Dryas/Preboreal) and 1212±86 cal y BP (Alleröd/Younger Dryas) on the absolute time scale. The absolute age of the Laacher See Tephra layer, dated with the radiocarbon method at 10 800 to 11200 ¹⁴C y BP, is estimated at 12350 ± 135 cal y BP. The oldest radiocarbon age of 14190±120 ¹⁴C y BP was obtained on macrofossils of pioneer vegetation which were found in the lowermost part of the sediment profile. For the late Glacial, the offset between the radiocarbon (10000–12000 ^14C y BP) and the absolute time scale (11400–13000 cal y BP) in the Soppensee chronology is not greater than 1000 years, which differs from the trend of the U/Th-radiocarbon curve derived from corals.     

The transition from subduction to continental collision: crustal structure in the North Canterbury region, New Zealand

The North Canterbury region marks the transition from Pacific plate subduction to continental collision in the South Island of New Zealand. Details of the seismicity, structure and tectonics of this region have been revealed by an 11-week microearthquake survey using 24 portable digital seismographs. Arrival time data from a well-recorded subset of microearthquakes have been combined with those from three explosions at the corners of the microearthquake network in a simultaneous inversion for both hypocentres and velocity structure. The velocity structure is consistent with the crust in North Canterbury being an extension of the converging Chatham Rise. The crust is about 27 km thick, and consists of an 11 km thick seismic upper crust and 7 km thick seismic lower crust, with the middle part of the crust being relatively aseismic. Seismic velocities are consistent with the upper and middle crust being composed of greywacke and schist respectively, while several lines of evidence suggest that the lower crust is the lower part of the old oceanic crust on which the overlying rocks were originally deposited.
The distribution of relocated earthquakes deeper than 15 km indicates that the seismic lower crust changes dip markedly near 43S. To the south-west it is subhorizontal, while to the north-east it dips north-west at about 10. Fault-plane solutions for these earthquakes also change near 43S. For events to the south, P -axes trend approximately normal to the plate boundary (reflecting continental collision), while for events to the north, T -axes are aligned down the dip of the subducted plate (reflecting slab pull). While lithospheric subduction is continuous across the transition, it is not clear whether the lower crust near 43S is flexed or torn.     

A computer simulation study of Al/Si ordering in gehlenite and the paradox of the low transition temperature

The ordering of Al and Si in gehlenite is considered using computer simulation. The enthalpy of ordering ΔH per 2Al+2Si atoms is found to be 0.52 eV. It is dominated by the nearest neighbour interaction, but the analysis is carried out to fifth neighbours. The nearest neighbour interaction differs significantly from that for other materials. The structure does not have a connected network of ordering sites, which mainly accounts for the unobservably low transition temperature for Al/Si ordering. Two alternatives are given for the likely ordering pattern.     

The need for international co-operation in the management of coastal environments

The coastal zones are areas of high biological productivity and intense human pressure. Environmental challenges arise from pollution and from urban and industrial development. Administrative, social and legal challenges centre upon the need for sound management of coastal zone resources, as an important component of national strategies for sustainability. A number of specific actions have been set out in Agenda 21, the principal product of the Earth Summit held in Rio de Janeiro in 1992. But these need to be carried forward within cross-sectoral, integrated coastal area management procedures. International action is also needed because marine ecosystems rarely coincide with national boundaries, and are affected by international economic, social and legal decisions.

International scientific co-operation on marine issues is already well established, and many regional action plans and Conventions have been adopted. Technological co-operation is less advanced. Such efforts need to be intensified, and continuously adapted. Sound plans for the future must be based on good science, critical economic evaluation of resources, sensitive evaluation of social and cultural factors and of the needs of local communities, evaluation of the risks of climate change, sea-level rise and other changes, and monitoring as a basis for continuing adaptation.     

Distribution of attached algae in estuaries

Preliminary studies on distributions of attached algae in British estuaries suggest that the estuaries might be classified on the basis of the flora in the upper reaches. This could contribute to biological assessment of water quality in estuaries.     

The late Palaeozoic Gondwana glaciation

The glacial deposits of Gondwana are today spread over one whole hemisphere. On the re-assembled Gondwana continents they still occupy an area exceeding that of the Pleistocene glaciation. The onset of the glaciation in the different areas has not yet been dated satisfactorily. The earliest lower and middle Carboniferous glacial beds occur in the Andean belt and in eastern Australia, where high mountains may have existed at that time. During Stephanian-Sakmarian time, when the pole wandered over Antarctica, large ice sheets reached sealevel in all the major depositories. Palaeotopographical reconstructions allow the conclusion that some of the ice centres were supported by uplands which reached altitudes of up to 1,500 m above sealevel. Depending on their palaeotopographical positions the glacigenic sediments exhibit the full facies range to be expected between glaciated uplands and glaciomarine environments. There are indications that ice may have flowed from Africa into the Paraná Basin, and from Antarctica into the Great Karoo-Basin and into Australia. At least 12 advances and retreats have been recognized in the Paraná Basin. Closer to the ice centres the record is less complete. The retreats were probably more of an interstadial than an interglacial nature. There is some evidence that the final deglaciation proceeded in stages from South America over Africa to Antarctica. The ice centres were fed by moist air from the Pacific Ocean and the Tethys.

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Zusammenfassung Die glazialen Ablagerungen von Gondwana sind heute über eine ganze Hemisphäre verteilt. Auch auf dem rekonstruierten Gondwana nehmen sie noch ein Gebiet ein, welches das der pleistozänen Vereisung übertrifft. Die frühesten, unter- und mittelkarbonen Vereisungsspuren finden sich im Anden-Gürtel und im Tasman-Belt in Ostaustralien, wo zu dieser Zeit hohe Gebirgsketten existiert haben können. Während des Stephan und Sakmar, als der Pol sich auf der Antarktis befand, erreichten große Inlandeis-Decken den Seespiegel in allen größeren Ablagerungsbecken. Paläotopographische Rekonstruktionen erlauben die Schlußfolgerung, daß einige der Eiszentren sich auf Hochländern mit Höhen von bis zu 1500 m befanden. Die glazialen Sedimente zeigen, abhängig von ihrer paläotopographischen Position, alle zu erwartenden Faziestypen. Es gibt Hinweise, daß Eis von Afrika in das Paraná-Becken und von Antarktika in das Große Karoo-Becken und nach Australien geflossen sein könnte, Wenigstens 12 Vorstöße und Rückzüge sind im Paraná-Becken erkannt worden. In der Nähe der Eiszentren ist die Zahl geringer. Die Rückzüge hatten wahrscheinlich mehr die Natur von Interstadialen als von Interglazialen. Es gibt Hinweise, daß das finale Abschmelzen im unteren Perm in mehreren Phasen von Südamerika über Afrika nach Antarktika fortgeschritten sein könnte. Die Eiszentren wurden durch feuchte Luftmassen vom Pazifischen Ozean und der Tethys genährt.

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Résumé Les dépôts glaciaires de Gondwana sont répartis actuellement sur une hémisphère entière. Même sur le Gondwana reconstitué, ils occupent encore une surface qui dépasse celle de la glaciation pleistocène. Les traces de glaciation les plus précoces, èo- et mésocarbonifères se trouvent dans la ceinture andine et dans la ceinture tasmanienne d'Australie orientale, où des chaînes de montagnes élevées ont pu exister à cette époque. Pendant le Stéphanien et le Sakmarien, lorsque le pôle s'est trouvé dans l'Antarctique, de grandes nappes continentales de glace ont atteint le niveau de la mer dans tous les grands bassins sédimentaires. Des reconstitutions paléotopographiques permettent de conclure que quelques-uns des centres de glaciation se trouvaient dans des zones de montagnes ayant des altitudes atteignant 1500 m. Les sédiments glaciaires montrent, en fonction de leur position paléotopographique, tous les types de faciès que l'on peut attendre. D'après certaines indications, la glace aurait pu couler d'Afrique dans le bassin du Paraná et de l'Antarctique dans le grand bassin du Karoo et vers l'Australie. Au moins douze avancées et retraits ont été reconnus dans le bassins du Paraná. A proximité des centres de glaciation leur nombre est moindre. Les retraits avaient sans doute un caractère plus interstadiaire qu'interglaciaire. Certaines indications permettent de penser que la fusion finale pouvrait avoir progressé, au cours du Permien inférieur, d'Amérique du Sud vers l'Afrique puis vers l'Antarctique, en plusieurs phases. Les centres de glaciation ont été nourris par des masses d'air humides venant de l'Ocean Pacifique et de la Téthys.

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