Climate variability and physical forcing of the food webs and the carbon budget on panarctic shelves     

Eddy Carmack  David Barber  Jens Christensen  Robie Macdonald  Bert Rudels  Egil Sakshaug   《Progress in Oceanography》2006,71(2-4):145

Brief overviews of the Arctic’s atmosphere, ice cover, circulation, primary production and sediment regime are given to provide a conceptual framework for considering panarctic shelves under scenarios of climate variability. We draw on past ‘regional’ studies to scale-up to the panarctic perspective. Within each discipline a synthesis of salient distributions and processes is given, and then functions are noted that are critically poised and/or near transition and thereby sensitive to climate variability and change. The various shelf regions are described and distinguished among three types: inflow shelves, interior shelves and outflow shelves. Emphasis is on projected climate changes that will likely have the greatest impact on shelf-basin exchange, productivity and sediment processes including (a) changes in wind fields (e.g. currents, ice drift, upwelling and downwelling); (b) changes in sea ice distribution (e.g. radiation and wind regimes, enhanced upwelling and mixing, ice transport and scour resuspension, primary production); and (c) changes in hydrology (e.g. sediment and organic carbon delivery, nutrient supplies). A discussion is given of the key rate-controlling processes, which differ for different properties and shelf types, as do the likely responses; that is, the distributions of nutrients, organic carbon, freshwater, sediments, and trace minerals will all respond differently to climate forcing.A fundamental conclusion is that the changes associated with light, nutrients, productivity and ice cover likely will be greatest at the shelf-break and margins, and that this forms a natural focus for a coordinated international effort. Recognizing that the real value of climate research is to prepare society for possible futures, and that such research must be based both on an understanding of the past (e.g. the palaeo-record) as well as an ability to reliably predict future scenarios (e.g. validated models), two recommendations emerge: firstly, a comprehensive survey of circumpolar shelf-break and slope sediments would provide long-term synchronous records of shelf-interior ocean exchange and primary production at the shelf edge; secondly, a synoptic panarctic ice and ocean survey using heavy icebreakers, aircraft, moorings and satellites would provide the validation data and knowledge required to properly model key forcing processes at the margins.  相似文献   

Current estimates of freshwater flux through Arctic and subarctic seas   总被引：2，自引：0，他引：2  

Robert Dickson  Bert Rudels  Stephen Dye  Michael Karcher  Jens Meincke  Igor Yashayaev 《Progress in Oceanography》2007,73(3-4):210

As the world warms, the expectation is that the freshwater outflows from the Arctic Ocean to the North Atlantic will strengthen and may act to suppress the rate of the climatically-important Atlantic meridional overturning circulation. Hitherto, however, we have lacked the system of measurements required to estimate the totality of the freshwater flux through subarctic seas. Though observations remain patchy and rudimentary in places, we piece-together the results from recent large-scale observational programmes together with associated modelling, to establish preliminary maps of the rates and pathways of freshwater flux through subarctic seas. These fluxes are calculated according to two reference salinities, S = 34.8 to conform with the majority of estimates reported in the literature, and S = 35.2, the salinity of the inflowing Atlantic water, to calculate the freshwater balance of the ‘Arctic Mediterranean’. We find that 148 mSv of freshwater enters the Nordic Seas across its northern boundary. There it is supplemented by around 54 mSv of freshwater from Baltic runoff, Norwegian runoff, P − E and Greenland ice melt, so that the total freshwater contribution to the Nordic Seas from all sources is 202 mSv. Of this, around 51 mSv of freshwater is estimated to pass south to the deep Atlantic in the dense water overflows leaving an assumed balance of 151 mSv to leave the Nordic Seas in the upper water export through Denmark Strait. The corresponding estimate for the freshwater outflow west of Greenland is 103 mSv relative to 35.2 so that the total freshwater flux reaching the North Atlantic through subarctic seas is around 300 mSv.  相似文献   

In-situ reflectance spectroscopy – analysing techniques for high-resolution pigment logging in sediment cores     

Bert Rein  Frank Sirocko 《International Journal of Earth Sciences》2002,91(5):950-954

The temporal resolution of marine proxy data is limited by analytically required sample size. We present in-situ reflectance spectroscopy techniques (usually applied in remote sensing) to analyse the organic fraction of marine and terrestrial sediment. From absorption band depths, photosynthesis pigment variations are derived for sediments from the upwelling region off Peru, where productivity is related to the annual variability of El Niño strength. Quantitative estimations of diagenetic photosynthesis pigments derived from absorption band analysis in reflectance spectra are highly correlated to organic carbon content. The ratio of pigment fractions is related to chlorine concentration and reflects organic matter preservation and deep-water ventilation changes. The import of terrigenous mineroclastics (TM) by local rivers is semi-quantitatively documented in the spectrum continuum. TM is inversely varying with organic matter preservation and chlorine concentration.  相似文献   

Твердый налет в зимнее время на милешовке     

František Rein 《Studia Geophysica et Geodaetica》1961,5(3):256-263

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Besonderheiten der Windstruktur auf Einem Kegelgipfel     

František Rein 《Studia Geophysica et Geodaetica》1962,6(3):309-311

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Relating variation in species composition to environmental variables: a multi-taxon study in an Indonesian coral reef complex     

Daniel F. R. Cleary  Lyndon De Vantier  Giyanto  Lyle Vail  Philip Manto  Nicole J. de Voogd  Paola G. Rachello-Dolmen  Yosephine Tuti  Agus Budiyanto  Jackie Wolstenholme  Bert W. Hoeksema  Suharsono 《Aquatic Sciences - Research Across Boundaries》2008,70(4):419-431

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Composition and properties of the iron hydroxides-cemented lenses in Estonian sandstone of Middle Devonian age     

Alla Shogenova  Anne Kleesment  Ann Hirt  Enn Pirrus  Toivo Kallaste  Kazbulat Shogenov  Rein Vaher 《Studia Geophysica et Geodaetica》2009,53(1):111-131

The formation of hematite and goethite concretions in different sedimentary rocks including sandstones is an important diagenetic process in the geologic history of the Earth. Its interpretation can also contribute to understanding the diagenetic history of Martian iron hydroxide concretions. A case study of iron-rich concretions from Estonian Middle Devonian sandstones exposed in ancient river valleys in southeastern Estonia was carried out based on the results of mineralogical, petrographical, geochemical, petrophysical and magnetic analyses. It was found that the high Fe₂O₃(total) content (25.0–39.5%), high magnetic susceptibility, bulk and grain density, very low porosity, corrosion and fracturing of the quartz grains of the platy iron concretions are in contrast with properties of the Devonian host sandstones. However the ferrous iron content (measured as FeO) of iron-rich concretions was as low as in the other Devonian rocks, suggesting an oxidizing environment and arid climate during the cementation by iron-hydroxides. The fracturing of quartz grains cemented by iron hydroxides could take place at near-surface conditions including vadose and phreatic zones in arid climate with high evaporation rates. Such climatic conditions have been reported for the Baltic region during Devonian, Upper Permian and Triassic times. We have found that goethite is prevalent in the cement, replacing clay and carbonate minerals. We assume that this iron-rich cement is originated from the mobilization of iron in host sandstones by groundwater, associated with tectonic activity at the end of the Middle Devonian, evidenced by fracturing in Devonian outcrops and caves. Although this mobilization could occur under reducing conditions, precipitation of goethite and hematite for the cementation could take place in oxidizing environment along bedding planes close to the surface during short sedimentation breaks. Another possible time for the formation of iron concretions could be Permian, under the condition of both arid climate and tectonic activity.  相似文献   

Decline of the Jakarta Bay molluscan fauna linked to human impact     

Sancia E.T. van der Meij  Robert G. Moolenbeek  Bert W. Hoeksema 《Marine pollution bulletin》2009,59(4-7):101

In 1937/38 representative mollusc collections were made in Jakarta Bay (West Java, Indonesia). New data from here and the adjacent offshore Thousand Islands archipelago (Kepulauan Seribu) became available in 2005. Although collecting efforts and sampling methods differed, a comparison of the molluscan fauna of Jakarta Bay between 1937/38 and 2005 reveals a distinct deterioration. From 1937 to 2005, Jakarta Bay received increasing amounts of sewage from the greater Jakarta area, as well as increased sediment input from the deforested West Java hinterland. Predatory gastropods and numerous mollusc species associated with carbonate (reef) substrate have vanished from Jakarta Bay, among which many edible species.  相似文献   

Thunderstorm days,thunderstorm duration and the number of lightning flashes in Czechoslovakia and in Finland     

František Popolanský  Leila Laitinen  Reviewer F. Rein 《Studia Geophysica et Geodaetica》1972,16(1):103-106

Zusammenfassung In dem Artikel werden die Gleichungen zwischen der Anzahl von Gewittertagen, der Gewitterdauer und der Anzahl von Blitzentladungen abgeleitet, die durch den CIGRE-Blitzzähler in 13 Stationen in der SSR und 6 Stationen in Finnland während einer 4-jährigen ununterbrochenen Beobachtungspheriode registriert wurden. Es wurde festgestellt, dass die die Beziehungen zwischen der Anzahl von Gewittertagen und der Anzahl von Blitzentladungen und zwischen der Gewitterdauer und der Anzahl von Blitzentladungen nichtlinear sind. Die Nichtlinearität zwischen den Jahressummen ist höher als die Nichtlinearität zwischen den Monatssummen einzelner Parameter.  相似文献   

Transient response of a thick beam of bimodular material     

C. W. Bert  A. D. Tran 《地震工程与结构动力学》1982,10(4):551-560

Certain materials have different elastic behaviour when they are loaded in tension as compared to compression. As an engineering approximation, they are usually modelled as a bimodular material, i.e. a bilinear material having different Young's moduli in tension and in compression. All of the previous analyses of bimodular beams known to the present investigators have been concerned with either static loading or harmonic vibration. Thus, the present work is believed to be the first to consider transient response of such beams. The transfer-matrix method is used to discretize spatially, while the timewise discretization is accomplished by use of the Newmark beta method.  相似文献