Sekundäre Umlagerung Pflanzlicher Mikrofossilien in klastischen Sedimenten

Ohne Zusammenfassung     

Overview of GIS Applications in Estuarine Monitoring and Assessment Research

Geographic information systems (GIS) tools are now considered integral in estuarine monitoring and assessment research. A synopsis is presented of our estuarine applications of GIS in the Northeast region of the U.S. The applications discussed cover sample site selection, support for field sampling activities, quality assurance of data, spatial display of geographic referenced information, quantitative spatial analysis of data, and communication of results.     

Predator-Prey Interaction between two Competing Sea Star Species of the Genus Astropecten

Abstract. The predator-prey interaction between two sea star species of the genus Astropecten known to be competitors was investigated at Costa Colostrai, Sardinia, Italy by means of SCUBA-Diving. It was estimated that predation of A. aranciacus would eliminate about 1 % of the prey population of A. bispinosus daily. Because densities of A. bispinosus were observed to be unaltered during the summer months, a considerable immigration of A. bispinosus into the area has to be postulated. A. bispinosus represents 40% of the dry organic matter consumed by A. aranciacus , and is one of the most important food items of this species.
A. aranciacus is not more efficient in preying upon A. bispinosus than in preying upon other food items; but efficiency is greater upon buried sea stars than upon walking ones.
Consequences for stability of the local ecosystem are discussed.     

Comparison of Ocean Surface Wind Stress Computed with Different Parameterization Functions of the Drag Coefficient

Depending on the choice of reference wind speed, the quantitative and qualitative properties of the drag coefficient may vary. On the ocean surface, surface waves are the physical roughness at the air-sea interface, and they play an important role in controlling the air-sea exchange processes. The degree of dynamic influence of surface waves scales with wavelength. Drag coefficient computed with the reference wind speed at an elevation proportional to the wavelength (for example, U _λ/2) is fundamentally different from the drag coefficient computed with the wind speed at fixed 10 m elevation (U ₁₀). A comparison has been carried out to quantify the difference in wind stress computation using several different parameterization functions of the drag coefficient. The result indicates that the wind stress computed from U ₁₀ input using a drag coefficient referenced to U _λ/2 is more accurate than that computed with drag coefficient functions referenced to U ₁₀.     

Bowers Swell: Evidence for a zone of compressive deformation concentric with Bowers Ridge, Bering Sea

Bowers Swell is a newly discovered bathymetric feature which is up to 90 m high, between 12 and 20 km wide, and which extends arcuately about 400 km along the northern and eastern sides of Bowers Ridge. The swell was first revealed on GLORIA sonographs and subsequently mapped on seismic reflection and 3.5 kHz bathymetric profiles. These geophysical data show that the swell caps an arcuate anticlinal ridge, which is composed of deformed strata in an ancient trench on the northern and eastern sides of Bowers Ridge. The trench fill beneath the swell is actively deforming, as shown by faulting of the sea floor and by thinning of the strata across the crest of the swell. Thinning and faulting of the trench strata preclude an origin for the swell by simple sediment draping over an older basement high. We considered several models for the origin of Bowers Swell, including folding and uplift of the underlying trench sediment during the interaction between the Pacific plate beneath the Aleutian Ridge and a remnant oceanic slab beneath Bowers Ridge. However, such plate motions should generate extensive seismicity beneath Bowers Ridge, which is aseismic, and refraction data do not show any remnant slab beneath Bowers Ridge. Another origin considered for Bowers Swell invokes sediment deformation resulting from differential loading and diapirism in the trench fill. However, diapirism is not evident on seismic reflection profiles across the swell. We favour a model in which sediment deformation and swell formation resulted from a few tens of kilometers of low seismicity motion by intraplate crustal blocks beneath the Aleutian Basin. This motion may result from the translation of blocks in western Alaska to the south-west, forcing the movement of the Bering Sea margin west of Alaska into the abyssal Aleutian Basin.     

大洋表层水中火山灰的富集状况

自从２０世纪５０年代在夏威夷对大气ＣＯ２进行监测以来 ,ＣＯ２ 浓度持续上升 ,只有两个时期例外。在１９６３～１９６５年 ,ＣＯ２ 最大年浓度连续３年保持不变 ,在１９９１～１９９３年也保持不变 ,与２０世纪发生在菲律宾Ａｇｕｎｇ、Ｂａｌｉ和Ｐｉｎａｔｕｂｏ两次最大的火山气体微粒冲击相吻合。因为这些事件中火山ＣＯ２ 排放量很大 ,势必会影响全球碳循环 ,使大气ＣＯ２ 短期稳定性增强。Ｓａｒｍｉｅｎｔｏ(１９９３)提出 ,１９９１年Ｐｉｎａｔｕｂｏ喷发之后大洋表层水的富化引起了大量浮游生物繁衍 ,这可能是大气ＣＯ２ 短期…     

Transport timescales for identifying seasonal variation in Bass Strait, south-eastern Australia

A three-dimensional σ-coordinate ocean model with realistic forcing is used to derive and compare flushing time, residence time and water age distributions in Bass Strait, a broad shallow shelf sea in south-eastern Australia which exhibits seasonal variation in water mass properties and circulation. Results illustrate flushing out of most old water occurs each winter–spring period and the circulation in summer increases age of remnant older water in the Strait. A correlation between water age and salinity is found in winter which is the result of advective “erosion” of the interior water mass. The presence of an area in the south-eastern part of the interior with low flushing is suggested to result from a number of physical factors including the presence of quasi-stationary eddies which entrain age, leading to relatively older water residing there.