A map series of the Southern East Pacific Rise and its flanks, 15° S to 19° S     

Daniel S. Scheirer  Ken C. Macdonald  Donald W. Forsyth  Stephen P. Miller  Dawn J. Wright  Marie-Hélène Cormier  Charles M. Weiland 《Marine Geophysical Researches》1996,18(1):1-12

Four large-scale bathymetric maps of the Southern East Pacific Rise and its flanks between 15° S and 19° S display many of the unique features of this superfast spreading environment including abundant seamounts (the Rano Rahi Field), axial discontinuities, discontinuity migration, and abyssal hill variation. Along with a summary of the regional geology, these maps will provide a valuable reference for other sea-going programs on-and off-axis in this area, including the Mantle ELectromagnetic and Tomography (MELT) experiment.  相似文献   

Processes Causing the Temporal Changes in Si/N Ratios of Nutrient Consumptions and Export Flux during the Spring Diatom Bloom     

Naoki?YoshieEmail author  Yasuhiro?Yamanaka 《Journal of Oceanography》2005,61(6):1059-1073

Two processes are generally explained as causes of temporal changes in the stoichiometric silicon/nitrogen (Si/N) ratios of sinking particles and of nutrient consumption in the surface water during the spring diatom bloom: (1) physiological changes of diatom under the stress of photosynthesis of diatom and (2) differences of regeneration between silicon and nitrogen. We investigated which process plays an important role in these changes using a one-dimensional ecosystem model that explicitly represents diatom and the other non-silicious phytoplankton. The model was applied to station A7 (41°30′ N, 145°30′ E) in the western North Pacific, where diatom regularly blooms in spring. Model simulations show that the Si/N ratios of the flux exported by the sinking particles at 100 m depth and of nutrient consumptions in the upper 100 m surface water have their maxima at the end of the spring diatom bloom, the values and timings of which are significantly different from each other. Analyses of the model results show that the differences of regeneration between silicon and nitrogen mainly cause the temporal changes of the Si/N ratios. On the other hand, the physiological changes of diatoms under stress can hardly cause these temporal changes, because the effect of the change in the diatom's uptake ratio of silicon to nitrogen is cancelled by that in its sinking rate.  相似文献   

A Zonal Pathway for NADW in the South Atlantic     

Nelson?G.?HoggEmail author  Andreas?M.?Thurnherr 《Journal of Oceanography》2005,61(3):493-507

Several large deployments of neutrally buoyant floats took place within the Antarctic Intermediate (AAIW), North Atlantic Deep Water (NADW), and the Antarctic Bottom Water (AABW) of the South Atlantic in the 1990s and a number of hydrographic sections were occupied as well. Here we use the spatially and temporally averaged velocities measured by these floats, combined with the hydrographic section data and various estimates of regional current transports from moored current meter arrays, to determine the circulation of the three major subthermocline water masses in a zonal strip across the South Atlantic between the latitudes of 19°S and 30°S. We concentrate on this region because the historical literature suggests that it is where the Deep Western Boundary Current containing NADW bifurcates. In support of this notion, we find that a net of about 5 Sv. of the 15–20 Sv that crosses 19°S does continue zonally eastward at least as far as the Mid-Atlantic Ridge. Once across the ridge it takes a circuit to the north along the ridge flanks before returning to the south in the eastern half of the Angola Basin. The data suggest that the NADW then continues on into the Indian Ocean. This scheme is discussed in the context of distributions of dissolved oxygen, silicate and salinity. In spite of the many float-years of data that were collected in the region a surprising result is that their impact on the computed solutions is quite modest. Although the focus is on the NADW we also discuss the circulation for the AAIW and AABW layers.  相似文献   

Storminess and vulnerability along the Atlantic coastlines of Europe: analysis of storm records and of a greenhouse gases induced climate scenario     

I. Lozano  R. J. N. Devoy  W. May  U. Andersen 《Marine Geology》2004,210(1-4):205-225

Identification of the distinctive circulation patterns of storminess on the Atlantic margin of Europe forms the main objective of this study; dealing with storm frequency, intensity and tracking. The climatology of the extratropical cyclones that affect this region has been examined for the period 1940–1998. Coastal meteorological data from Ireland to Spain have been linked to the cyclone history for the North Atlantic in the analysis of storm records for European coasts. The study examines the evolution in the occurrence of storms since the 1940s and also their relationship with the North Atlantic Oscillation (NAO). Results indicate a seasonal shift in the wind climate, with regionally more severe winters and calmer summers established. This pattern appears to be linked to a northward displacement in the main North Atlantic cyclone track.

An experiment with the ECHAM4 A-GCM at high resolution (T106) has also been used to model the effect of a greenhouse gases induced warming climate on the climatology of coastal storms in the region. The experiment consists of (1), a 30-year control time-slice representing present-day equivalent CO₂ concentrations and (2), a 30-year perturbed period corresponding to a time when the radiative forcing has doubled in terms of equivalent CO₂ concentrations. The boundary conditions have been obtained from an atmosphere-ocean coupled OA-GCM simulation at low horizontal resolution. An algorithm was developed to allow the identification of individual cyclone movements in selected coastal zones. For most of the northern part of the study region, covering Ireland and Scotland, results describe the establishment by ca. 2060 of a tendency for fewer but more intense storms.

The impacts of these changes in storminess for the vulnerability of European Atlantic coasts are considered. For low-lying, exposed and ‘soft’ sedimentary coasts, as in Ireland, these changes in storminess are likely to result in significant localised increases in coastal erosion.  相似文献   

North Pacific Synthesis of the Joint Global Ocean Flux Study: Overview     

Toshiro Saino  Alexander Bychkov  Chen-Tung Arthur Chen  Paul J. Harrison 《Journal of Oceanography》2004,60(1):1-4

This special issue is comprised of 13 papers, including this overview, and focuses on the synthesis of the Joint Global Ocean Flux Study (JGOFS) in the North Pacific which took place from 1997 through 2003. The effort was led by the JGOFS North Pacific Synthesis Group, with the aim of quantifying CO₂ drawdown by physical and biological pumps in the North Pacific by identifying and studying the regional, seasonal to inter-annual variations in the key processes, and understanding their regulating mechanisms. Emphasis was placed on the similarities and differences of the biogeochemical regimes in the eastern and western subarctic Pacific. Effort was also made to address the future research directions which arose from the scientific findings during the North Pacific JGOFS process study. A brief overview of the papers from view points of CO₂ drawdown by physical and biological pumps, spatial variability, and temporal variability from seasonal to decadal scales is made, followed by suggestions for the directions of future research. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Relationships Between Community Structure of the Intertidal Macroinfauna and Sandy Beach Characteristics Along the Chilean Coast   总被引：2，自引：0，他引：2  

Eduardo Jaramillo  Heraldo Contreras  Cristian Duarte  & Pedro Quijón 《Marine Ecology》2001,22(4):323-342

Abstract. Eight sandy beaches were seasonally sampled along the coast of Chile, from ca. 21 to 42° S (about 3000 km) to study the relationship between community structure of the intertidal macroinfauna and beach characteristics. Sediment samples (0.1 m², 30 cm deep) were collected (July – September 1998 and December 1998 – January 1999) with plastic cylinders at 15 equally spaced levels along three replicated transects extending from above the drift line to the swash zone. The sediment was sieved through a 1 mm mesh and the organisms collected stored in 5 % formalin. To define beach types, Dean's parameter (Ω) was calculated from wave heights and periods, and fall velocity of sand particles from the swash zone. Crustaceans (mainly peracarids) were the most diverse group with 14 species, followed by polychaetes with 5 species. The talitrid amphipod Orchestoidea tuberculata , the cirolanid isopods Excirolana braziliensis and E. hirsuticauda and the anomuran decapod Emerita analoga were the most widely distributed and common species. Regression analyses between species richness, abundance and biomass of the whole macroinfauna versus sediment characteristics, beach face slopes and morphodynamic beach states showed no significant relationships. Thus, macroinfaunal community characteristics did not increase linearly from lower intermediate to higher intermediate or dissipative beach states as had been found before in Chile or in other coasts. A comparative analysis with data from sandy beaches of other world regions showed that the number of species inhabiting Chilean sandy beaches was generally lower, whereas total population abundances were generally higher compared with values reported elsewhere.  相似文献   

Gravity Anomaly and Tectonics in the Northern Part of the North Fiji Basin - Preliminary Result of the 1994 NOFI Cruise under the NEW STARMER Programme     

Matsumoto  Takeshi  Goslin  Jean  Lagabrielle  Yves  Ruellan  Etienne  Tanahashi  Manabu 《Marine Geophysical Researches》1997,19(1):37-53

A surface ship gravity survey was carried out in the northern part of the North Fiji Basin during the NOFI cruise by the R/V l'Atalante in August-September, 1994. The two ridges inside the study area, the South Pandora Ridge and the Tripartite Ridge, present different structures and states of isostatic equilibrium in terms of gravity anomaly and its tectonic implications. The former is supported by a restoring force of an imaginary elastic plate in the crust and the latter by the Airy type isostasy. These characteristics can be derived from the difference in magmatic activity, as influenced by the difference in lithospheric structure. The latter is characterised by greater active magmatism and hydrothermalism underneath the ridge than the former. Such a difference in the magmatic activity and the horizontal scale of the shallow subsurface structure is derived from the difference in the stiffness or viscosity of the lithosphere beneath the two ridges.  相似文献   

热带西太平洋海洋上层热含量的分布特征及其年际变化的分析   总被引：1，自引：0，他引：1  

白虹  丁宗信  李永祥 《海洋与湖沼》1995,26(2):154-160

选用海面至20℃等温线所处深度水层的平均温度来表征研究海域海洋上层热含量。利用这一特征值，分析1986—1990年期间热带西太平洋边缘海域海洋上层热含量在秋季的分布特征和年际变化。结果表明：（1）热含量呈南高北低分布，在7．5－22．1°N范围内。以130°E断面为代表，热含量的平均递减率为0．179（℃／纬度）；（2）热含量的分布主要取决于环流系统，其等值线因受黑潮和棉兰老海流的影响而由纬向分布转向经向分布。某些区域因受暖涡及冷涡的影响而呈封闭状分布；（3）热含量的年际变化与E1Nino事件存在着很好的相关性，在E1Nino事件发生期间，热含量变得很低，高热含量（大于26．5℃）海区的分布范围明显缩小。  相似文献   

Differences in ratios of stable isotopes of nitrogen in long-finned pilot whales (Globicephala melas) in the western and eastern North Atlantic   总被引：1，自引：0，他引：1  

Abend  Alan G.; Smith  Tim D. 《ICES Journal of Marine Science》1995,52(5):837-841

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Swath mapping of the seafloor and its application to deep-bottom fisheries in New Caledonia     

Patrick Lehodey  René Grandperrin 《Marine Geophysical Researches》1996,18(2-4):449-458

A bottom longline fishery operated in the EEZ of New Caledonia from 1988 to 1991. Fishing focused on five seamounts with summits at depths ranging from 500 to 750 m. The target species was alfonsino, Beryx splendens. As the soundings available from marine charts were not detailed enough, the fishing masters had to make their own charts in order to set the gear in the right location. A series of 11 scientific cruises devoted to a research program on alfonsino was launched in late 1991. During the first scientific cruises, several days were spent mapping the seabed to improve the existing knowledge of the topography of three seamounts by coupling the EDO echosounder depth measurements to the GPS positions. As this procedure is slow, it is applicable to limited areas or, if a wider grid is used, to large zones to locate major structures such as ridges and seamounts. The emergence of the multibeam echosounder has greatly improved seabed mapping performance. This tool seems to fit the requirement of exploratory deep-bottom fishing particularly well, as it covers large areas while providing details of the bottom. The EM 12 was used to obtain bathymetry and imagery of the SE portion of the EEZ of New Caledonia, covering an approximate area of 70,000 km² in two weeks. For depths ranging from 500 to 4,500 m, the results were impressive. They confirmed the known major features and provided greater topographical detail, revealing fine unknown structures. They also provided information on the type of substratum, information which might influence the fishing strategy. Finally, they made it possible to obtain an accurate estimate of the exploitable area which in turn led to new stock estimates.  相似文献