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81.
Eberhard Hagen 《Journal of Oceanography》2005,61(6):1039-1046
Using hydrographic data of three extended zonal sections, which cover the upper 1000 dbar layer along 10°, 21°, and 32°N in
the North-East Atlantic between 20° and 45°W, observational evidence is presented for zonal wavelengths of resonantly excited,
first mode, long, baroclinic Rossby waves. The amplitudes of associated anomalies in the mass field decrease with increasing
offshore distance. The associated zonal wavelengths reach several hundred kilometres and decrease with increasing latitude.
Due to the Rossby dispersion, the detected wave patterns slowly propagate westward, somewhat faster in the south than in the
north. The results obtained confirm the data sets remotely sensed by satellites, as well as the outcomes of analytical and
numerical models. 相似文献
82.
83.
关于中美洲的上新世历史 ,最有趣的问题是中美洲航道最终关闭所起的作用以及其改变大洋循环和影响全球气候的可能性。航道关闭是引起地球气候史上北半球从显著温暖期变为冰盖生长期的主要因素。然而 ,关于上新世气候历史的几个基本问题仍然存在争议。中美洲地区的构造历史极其复杂 ,有人曾运用各种方法来重建陆桥的隆起历史。Duque_Caro(1990)鉴定的底栖有孔虫显示出各种动物群存在了约12.9~11.8Ma ,即那时存在一个深海循环障碍。6.8Ma和4.6Ma连续的隆起引起了浮游有孔虫组合发生变化。加勒比海沉积物… 相似文献
84.
R. B. Johns T. Belsky E. D. McCarthy A. L. Burlingame Pat Haug H. K. Schnoes W. Richter M. Calvin 《Geochimica et cosmochimica acta》1966,30(12):1191-1222
Several shales and oils ranging in age from 3 million to 2·7 billion years have been investigated for their hydrocarbon content using gas chromatography and mass spectrometry as primary analytical tools. From the Soudan Shale from Minnesota (2·7 × 109yr) the C18, C19, C20 and C21 isoprenoid-alkanes were obtained. The Antrim shale from Michigan (about 265 × 106 yr) yielded the C16, C18, C19, C20 and C21 isoprenoids, as well as a C16 iso-alkane and the C18 and C19 cyclohexyl n-alkanes. The San Joaquin Oil (30 × 106 yr) and the Abbott Rock Oil (3 × 106 yr) contained the C16, C18, C19, C20 and the C18, C19, C20 and C21 isoprenoids respectively. In addition, a series of iso-alkanes (C16−C18), anteiso-alkanes (C16−C18) and n-alkylcyclohexanes (C16−C19) as well as a C21 isoprenoid were obtained from the Nonesuch Seep Oil (1 × 109 yr). This analysis provides a comprehensive picture of the types of biogenic hydrocarbons found in oils and shales of widely differing ages, and in particular, the finding of isoprenoid alkanes in the Soudan Shale furnishes evidence for life processes at that period of geological time. 相似文献
85.
Oliver Sachs Eberhard J. Sauter Michael Schlüter Michiel M. Rutgers van der Loeff Kerstin Jerosch Ola Holby 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(8):1319-1335
For the investigation of organic carbon fluxes reaching the seafloor, oxygen microprofiles were measured at 145 sites in different sub-regions of the Southern Ocean. At 11 sites, an in situ oxygen microprofiler was deployed for the measurement of oxygen profiles and the calculation of organic carbon fluxes. At four sites, both in situ and ex situ data were determined for high latitudes. Based on this data set as well as on previous published data, a relationship was established for the estimation of fluxes derived by ex situ measured O2 profiles. The fluxes of labile organic matter range from 0.5 to 37.1 mg C m?2 d?1. The high values determined by in situ measurements were observed in the Polar Front region (water depth of more than 4290 m) and are comparable to organic matter fluxes observed for high-productivity, upwelling areas like off West Africa. The oxygen penetration depth, which reflects the long-term organic matter flux to the sediment, was correlated with assemblages of key diatom species. In the Scotia Sea (~3000 m water depth), oxygen penetration depths of less than 15 cm were observed, indicating high benthic organic carbon fluxes. In contrast, the oxic zone extends down to several decimeters in abyssal sediments of the Weddell Sea and the southeastern South Atlantic. The regional pattern of organic carbon fluxes derived from microsensor data suggests that episodic and seasonal sedimentation pulses are important for the carbon supply to the seafloor of the deep Southern Ocean. 相似文献
86.
Solar prominences have been simultaneously observed in the integrated light of the He D3 and the Hβ emissions on two successive days, using the SST on La Palma with its tip-tilt mirror locked on a nearby white-light
limb facular grain. The spatial and the temporal variation of the integrated line intensities and their ratio shows mainly
two characteristics: (A) Constant emission ratio (even) in regions with substantial intensity variations and (B) varying emission
ratio (often) tightly related to intensity structures of the prominence. (A) May be explained by a different number of superposing
threads along the line of sight having very similar physical state. (B) Indicates threads with different intrinsic physical
states; these may depend on the gas pressure or the inner structure of each thread, i.e., the “packing density,” affecting the penetration of ionizing EUV radiation, which affects the He i level populations and thus the rate of the triplet excitation. 相似文献
87.
88.
Kerstin Fieg Rüdiger Gerdes Eberhard Fahrbach Agnieszka Beszczynska-Möller Ursula Schauer 《Ocean Dynamics》2010,60(3):491-502
We discuss the model representation of volume transports through one of the most climate-relevant ocean passages, the Fram
Strait. We compare results from a coupled ocean–sea ice model with different resolutions (∼1/12° and ∼1/4°) and measurements
from a mooring array along 79° N. The 1/4° model delivers a realistic mean climate state and realistic net volume transports.
However, this model fails to reproduce the observed intense barotropic recirculation that reaches far north in Fram Strait.
This recirculation is captured in the higher resolution version of the model. Other differences exist in the circulation over
the East Greenland Shelf and in the temperature of Atlantic waters in the Fram Strait region as well as in surface heat fluxes.
We find that a combination of high-resolution model results and long-term measurements can improve the interpretation of measured
and simulated processes and reduce the uncertainties in exchange rates between Arctic and the North Atlantic. 相似文献
89.
North Atlantic control on precipitation pattern in the eastern Mediterranean/Black Sea region during the last glacial 总被引:1,自引:0,他引:1
Olga Kwiecien Helge W. Arz Frank Lamy Birgit Plessen Andr Bahr Gerald H. Haug 《Quaternary Research》2009,71(3):375-384
Based on proxy records from western Black Sea cores, we provide a comprehensive study of climate change during the last glacial maximum and late-glacial period in the Black Sea region. For the first time we present a record of relative changes in precipitation for NW Anatolia based on variations in the terrigenous supply expressed as detrital carbonate concentration. The good correspondence between reconstructed rainfall intensity in NW Anatolia and past western Mediterranean sea surface temperatures (SSTs) implies that during the glacial period the precipitation variability was controlled, like today, by Mediterranean cyclonic disturbances. Periods of reduced precipitation correlate well with low SSTs in the Mediterranean related to Heinrich events H1 and H2. Stable oxygen isotopes and lithological and mineralogical data point to a significant modification in the dominant freshwater/sediment source concomitant to the meltwater inflow after 16.4 cal ka BP. This change implies intensification of the northern sediment source and, with other records from the Mediterranean region, consistently suggests a reorganization of the atmospheric circulation pattern affecting the hydrology of the European continent. The early deglacial northward retreat of both atmospheric and oceanic polar fronts was responsible for the warming in the Mediterranean region, leading simultaneously to more humid conditions in central and northern Europe. 相似文献
90.
Valentina Marzia Rossi Niall William Paterson William Helland‐Hansen Tore Grane Klausen Christian Haug Eide 《Sedimentology》2019,66(6):2234-2267
In recent years it has become clear that many shallow‐marine heterolithic and mudstone‐dominated successions are deposited as mud belts forming part of subaqueous deltas that are related to major fluvial sources either upstream or along shore. Here the Havert Formation is presented as an ancient example of this kind of system. The Havert Formation in the south‐western Barents Sea represents shelf margin clinoforms consisting predominantly of heterolithic deposits. Sediments were mainly derived from the east (Ural Mountains), but a smaller system prograded northward from Fennoscandia. The Havert Formation holds a lot of interest due to: (i) its stratigraphic position, directly above the Permo–Triassic boundary and contemporaneous to the emplacement of the Siberian Traps; (ii) the fact that it represents the first siliciclastic input in the south‐western Barents Sea and it shows interaction between Uralian‐derived and Fennoscandian‐derived sediments; and (iii) its hydrocarbon potential. This study is focused on a detailed sedimentological analysis of cored intervals of the (Ural‐derived) Havert Formation, in combination with seismic interpretation, well‐log correlations and palynological analysis of the Havert and overlying Klappmyss formations. The cored intervals belong to the shelf environment of the Havert shelf‐margin clinoforms (300 to 500 m thick). This sedimentological analysis distinguishes six facies associations, spanning from tidally‐influenced channels at the shoreline to mud‐rich subaqueous platform and foresets of the subaqueous delta. Seismic lines and well‐log correlations show the larger‐scale evolution of the Ural‐derived Havert Formation, characterized by episodes of low‐accommodation and high‐accommodation. The palynological analyses provide the first detailed study of the Havert Formation in the Nordkapp Basin, revising its depositional age in the region as Induan to early Olenekian (Smithian). Furthermore, they strengthen the environmental interpretation; palynofacies present on the shelf record flora of tidally‐influenced coastal plains, whereas the palynofacies in the deep‐water slope contain only amorphous organic matter. 相似文献