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11.
B. von Bodungen A. Antia E. Bauerfeind O. Haupt W. Koeve E. Machado I. Peeken R. Peinert S. Reitmeier C. Thomsen M. Voss M. Wunsch U. Zeller B. Zeitzschel 《International Journal of Earth Sciences》1995,84(1):11-27
Pelagic processes and their relation to vertical flux have been studied in the Norwegian and Greenland Seas since 1986. Results of long-term sediment trap deployments and adjoining process studies are presented, and the underlying methodological and conceptional background is discussed. Recent extension of these investigations at the Barents Sea continental slope are also presented. With similar conditions of input irradiation and nutrient conditions, the Norwegian and Greenland Seas exhibit comparable mean annual rates of new and total production. Major differences can be found between these regions, however, in the hydrographic conditions constraining primary production and in the composition and seasonal development of the plankton. This is reflected in differences in the temporal patterns of vertical particle flux in relation to new production in the euphotic zone, the composition of particles exported and in different processes leading to their modification in the mid-water layers.In the Norwegian Sea heavy grazing pressure during early spring retards the accumulation of phytoplankton stocks and thus a mass sedimentation of diatoms that is often associated with spring blooms. This, in conjunction with the further seasonal development of zooplankton populations, serves to delay the annual peak in sedimentation to summer or autumn. Carbonate sedimentation in the Norwegian Sea, however, is significantly higher than in the Greenland Sea, where physical factors exert a greater control on phytoplankton development and the sedimentation of opal is of greater importance. In addition to these comparative long-term studies a case study has been carried out at the continental slope of the Barents Sea, where an emphasis was laid on the influence of resuspension and across-slope lateral transport with an analysis of suspended and sedimented material. 相似文献
12.
B. J. Haupt C. Schäfer-Neth K. Stattegger 《International Journal of Earth Sciences》1995,84(1):137-150
Modelling of Late Quaternary paleoceanography and sedimentation in the northern North Atlantic (NNA) is achieved by coupling the ocean general circulation model SCINNA (Sensitivity and Circulation In the NNA) to the sedimentation models SENNA (Sedimentation In the NNA) and PATRINNA (PArticle Tracing In the NNA).SCINNA is based on the primitive equations with conservation of mass, momentum, energy, heat and salt. SENNA and PATRINNA are driven by temperature, salinity and velocity fields derived from SCINNA. The modelling includes three-dimensional circulation of the ocean, sediment transport in the water column and two-dimensional sedimentary processes in a thin bottom layer. SENNA calculates the erosion, transport and deposition of sediments, resulting in sedimentation patterns for specific time intervals. PATRINNA models the transport paths of single sediment grains corresponding to the ocean circulation.The NNA reacts in a highly sensitive manner to small forcing changes, as shown by our sensitivity experiments. From these experiments it is possible to model specific circulation regimes for glacial and interglacial periods, for melt water events and for the onset of glaciation. The different climatic stages in the circulation model produce different sediment patterns in the sedimentation models, which correspond closely to the sedimentary record. 相似文献
13.
Dissolved organic matter dynamics during the spring snowmelt at a boreal river valley mire complex in Northwest Russia 
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下载免费PDF全文 Armine Avagyan Benjamin R. K. Runkle Nina Hennings Hannes Haupt Tarmo Virtanen Lars Kutzbach 《水文研究》2016,30(11):1727-1741
Boreal mire landscapes are rich in soil carbon and significantly contribute to the carbon input of aquatic ecosystems. They are composed of different mesoscale ecohydrological subunits, whose individual contributions to the water and carbon export of mire catchments are not well understood. The spring snowmelt period is the major hydrological event in the annual water cycle of the boreal regions and strongly influences the carbon flux between the terrestrial and aquatic systems. The aim of this study was (1) to provide a conceptual understanding of the spatial and temporal dynamics of the surface water chemistry along a swamp forest‐fen‐bog gradient during the snowmelt period, (2) to quantify the exported dissolved organic carbon (DOC) content in the runoff and (3) to identify the ecohydrological landscape unit that contributes most to DOC export during the snowmelt period in a heterogeneous mire complex in Northwest Russia. The highest DOC concentrations were detected in the swamp forest, and the lowest concentrations were observed at the treeless bog by the end of the snowmelt period (swamp forest: 37–43 mg l?1, bog: 13–17 mg l?1). During the spring snowmelt period, a significant amount (~1.7 g C m?2) of DOC was transferred by the ~74 mm of runoff from the catchment into the river. Variability in the thawing periods led to differences in the relative contributions of each ecohydrological zone to the carbon export measured at a stream channel draining the studied part of the mire complex. An increased understanding of the variation in DOC concentrations and contributions from the mesoscale ecohydrological subunits to carbon export can help to predict the potential regional loss of DOC based on land cover type under climate change. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
14.
According to the current paradigm of modern climatology and oceanography, the global ocean thermohaline circulation works as the so-called “global ocean salinity conveyor belt” – a system of currents connecting different ocean basins and most notably – the northern North Atlantic and northern North Pacific Oceans – the most distant regions of the world ocean. It is shown here that a slight disparity in freshwater redistribution between the Atlantic and Pacific oceans can be sufficient for building up and maintaining a global conveyor-type ocean thermohaline circulation. On the other hand, relatively small changes in this disparity leading to change in sea surface salinity contrasts between and in the north-south within the northern parts of these two oceans can easily change the conveyor. 相似文献
15.
D. L. Mason D. W. Folger R. S. Haupt R. R. McGirr W. H. Hoyt 《Environmental Geology》1977,1(6):341-347
From November of 1973 to May of 1974, 15 arrays of sediment traps were placed along 33 km of southern Lake Champlain to sample
the distribution of effluent from a large paper plant located on the western shore which had commenced operation in 1971.
In the arrays located near the effluent diffuser pipeline as much as 2.3 cm of sediment accumulated, whereas elsewhere in
the lake less than 1 cm accumulated. In the area of accelerated accumulation, sediments contained high concentrations of several
components used in or derived from paper manufacturing. Values for kaolinite, expressed as the ratio of kaolinite to chlorite,
for example, were as high as 1.4, anatase (TiO2) concentrations were as high as 0.8%, organic carbon 8.7%, and phosphorus 254 μg/g; all were more abundant than in sediments
collected in traps to the south or north. In surficial bottom sediments collected near each array organic carbon and phosphorus
were also higher (4.2% and 127 μg/g respectively) near the diffuser than elsewhere. Thus, the new plant after three years
of production measurably affected the composition of suspended sediment and surficial bottom sediment despite the construction
and use of extensive facilities to reduce the flow of pollutants to the lake. 相似文献
16.
This paper presents the method to develop response surface diagrams (RSD) suitable to evaluate the impacts of climate change on potential crop production and crop area. The diagrams depict the response of different agricultural crops to average long-term changes in ambient temperature and precipitation on a country basis. They take into account the spatial and seasonal variability of climate, and differences in the climate response of important crops. RSDs for Germany and the Democratic Republic of Congo illustrate that countries and crop types differ greatly in their sensitivity to unit changes in long-term average climate. In comparing the area-weighted RSDs for Germany and Democratic Republic of Congo, it was found that the potential production in Germany of a weighted aggregation of crops is mainly sensitive to changes in temperature, whereas the potential crop production in the Democratic Republic of Congo mainly responds to changes in precipitation (over the specified ranges of climate variables). The RSDs can provide a visual overview of these varying sensitivities, and are a convenient and simple-to-understand method to summarize crop responses to climate change in a particular country. 相似文献
17.
The sensitivity of the ocean circulation to changes in North Atlantic surface fluxes has become a major factor in explaining climate variability. The role of the Antarctic Bottom Water in modulating this variability has received much less attention, limiting the development of a complete understanding of decadal to millennial time-scale climate change. New analyses indicate that the southern deepwater source may change dramatically (e.g., experience a decrease of as much as two thirds during last 800 years). Such change can substantially alter the ocean circulation patterns of the last millennium. Additional analyses indicate that the Southern Hemisphere led the Northern Hemisphere changes in some of the glacial cycles of Pleistocene, implying a seesaw-type oscillation of the global ocean conveyor. The potential for melting of sea ice and ice sheets in the Antarctica associated with global warming can cause a further slowdown of the southern deepwater source. These results demand an assessment of the role of the Southern Ocean in driving changes of the global ocean circulation and climate. Systematic model simulation targeting the ocean circulation response to changes in surface salinity in the high latitudes of both Northern and Southern Hemispheres demonstrate that meltwater impacts in one hemisphere may lead to a strengthening of the thermohaline conveyor driven by the source in the opposite hemisphere. This, in turn, leads to significant changes in poleward heat transport. Further, meltwater events can lead to deep-sea warming and thermal expansion of abyssal water, that in turn cause a substantial sea-level change even without a major ice sheet melting. 相似文献
18.
Photoelectric, photographic, and visual observations of second and third contacts of the total solar eclipses of 12 November, 1966 and 7 March, 1970 are analyzed. The observations indicate a difference in the reference system of Newcomb's Tables of the Sun as compared to the reference system of the Improved Lunar Ephemeris (J = 2) of 0s.911 ± 0s.034 m.e. The correction is to be applied in the sense of reducing the value of T as tabulated in the American Ephemeris when interpolating the position of the Moon. 相似文献