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Katarzyna Blachowiak-Samolyk Slawek Kwasniewski Katarzyna Dmoch Haakon Hop Stig Falk-Petersen 《Deep Sea Research Part II: Topical Studies in Oceanography》2007,54(23-26):2716
The trophic structure of zooplankton was investigated in Fram Strait (north western Svalbard) in spring and autumn of 2003. Depth-stratified zooplankton samples were collected at 12 stations on the shelf (200 m), across the shelf-slope (500 m) and over deep water (>750 m), using a Multiple Plankton Sampler equipped with 0.180-mm mesh size nets.Higher zooplankton abundance and estimated biomass were found in the shelf area. Abundance and biomass were two times higher in August, when sea-surface temperature was higher than in May. Herbivores dominated numerically in May, and omnivores in August, suggesting a seasonal sequence of domination by different trophic groups. Cirripedia nauplii and Fritillaria borealis prevailed in spring, whereas copepod nauplii and Calanus finmarchicus were numerically the most important herbivores in autumn. Small copepods, Oithona similis and Triconia borealis, were the most numerous omnivorous species in both seasons, but their abundances increased in autumn. Chaetognatha (mainly Eukrohnia hamata) accounted for the highest abundance and biomass among predatory taxa at all deep-water stations and during both seasons. Regarding vertical distribution, herbivores dominated numerically in the surface layer (0–20 m), and omnivores were concentrated somewhat deeper (20–50 m) during both seasons. Maximum abundance of predators was found in the surface layer (0–20 m) in spring, and generally in the 20–50 m layer in autumn. This paper presents the first comprehensive summary of the zooplankton trophic structure in the Fram Strait area. Our goals are to improve understanding of energy transfer through this ecosystem, and of potential climate-induced changes in Arctic marine food webs. 相似文献
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Bioavailable iron in the Southern Ocean: the significance of the iceberg conveyor belt 总被引：1，自引：0，他引：1
Productivity in the Southern Oceans is iron-limited, and the supply of iron dissolved from aeolian dust is believed to be the main source from outside the marine reservoir. Glacial sediment sources of iron have rarely been considered, as the iron has been assumed to be inert and non-bioavailable. This study demonstrates the presence of potentially bioavailable Fe as ferrihydrite and goethite in nanoparticulate clusters, in sediments collected from icebergs in the Southern Ocean and glaciers on the Antarctic landmass. Nanoparticles in ice can be transported by icebergs away from coastal regions in the Southern Ocean, enabling melting to release bioavailable Fe to the open ocean. The abundance of nanoparticulate iron has been measured by an ascorbate extraction. This data indicates that the fluxes of bioavailable iron supplied to the Southern Ocean from aeolian dust (0.01–0.13 Tg yr-1) and icebergs (0.06–0.12 Tg yr-1) are comparable. Increases in iceberg production thus have the capacity to increase productivity and this newly identified negative feedback may help to mitigate fossil fuel emissions. 相似文献
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Physical and biological characteristics of the pelagic system across Fram Strait to Kongsfjorden 总被引：1，自引：1，他引：1
Haakon Hop Stig Falk-Petersen Harald Svendsen Slawek Kwasniewski Vladimir Pavlov Olga Pavlova Janne E. Sreide 《Progress in Oceanography》2006,71(2-4):182
The Fram Strait is very important with regard to heat and mass exchange in the Arctic Ocean, and the large quantities of heat carried north by the West Spitsbergen Current (WSC) influence the climate in the Arctic region as a whole. A large volume of water and ice is transported through Fram Strait, with net water transport of 1.7–3.2 Sv southward in the East Greenland Current and a volume ice flux in the range of 0.06–0.11 Sv. The mean annual ice flux is about 866,000 km2 yr−1. The Kongsfjorden–Krossfjorden fjord system on the coast of Spitsbergen, or at the eastern extreme of Fram Strait, is mainly affected by the northbound transport of water in the WSC. Mixing processes on the shelf result in Transformed Atlantic Water in the fjords, and the advection of Atlantic water also carries boreal fauna into the fjords. The phytoplankton production is about 80 g C m−2 yr−1 in Fram Strait, and has been estimated both below and above this for Kongsfjorden. The zooplankton fauna is diverse, but dominated in terms of biomass by calanoid copepods, particularly Calanus glacialis and C. finmarchicus. Other important copepods include C. hyperboreus, Metridia longa and the smaller, more numerous Pseudocalanus (P. minutus and P. acuspes), Microcalanus (M. pusillus and M. pygmaeus) and Oithona similis. The most important species of other taxa appear to be the amphipods Themisto libellula and T. abyssorum, the euphausiids Thysanoessa inermis and T. longicaudata and the chaetognaths Sagitta elegans and Eukrohnia hamata. A comparison between the open ocean of Fram Strait and the restricted fjord system of Kongsfjorden–Krossfjorden can be made within limitations. The same species tend to dominate, but the Fram Strait zooplankton fauna differs by the presence of meso- and bathypelagic copepods. The seasonal and inter-annual variation in zooplankton is described for Kongsfjorden based on the record during July 1996–2002. The ice macrofauna is much less diverse, consisting of a handful of amphipod species and the polar cod. The ice-associated biomass transport of ice-amphipods was calculated, based on the ice area transport, at about 3.55 × 106 ton wet weight per year or about 4.2 × 105 t C yr−1. This represents a large energy input to the Greenland Sea, but also a drain on the core population residing in the multi-year pack ice (MYI) in the Arctic Ocean. A continuous habitat loss of MYI due to climate warming will likely reduce dramatically the sympagic food source. The pelagic and sympagic food web structures were revealed by stable isotopes. The carbon sources of particulate organic matter (POM), being Ice-POM and Pelagic-POM, revealed different isotopic signals in the organisms of the food web, and also provided information about the sympagic–pelagic and pelagic–benthic couplings. The marine food web and energy pathways were further determined by fatty acid trophic markers, which to a large extent supported the stable isotope picture of the marine food web, although some discrepancies were noted, particularly with regard to predator–prey relationships of ctenophores and pteropods. 相似文献
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Wojciech Walkusz Slawek Kwasniewski Stig Falk-Petersen Haakon Hop Vigdis Tverberg Piotr Wieczorek & Jan Marcin Weslawski 《Polar research》2009,28(2):254-281
Seasonal changes in the zooplankton composition of the glacially influenced Kongsfjorden, Svalbard (79°N, 12°E), and its adjacent shelf were studied in 2002. Samples were collected in the spring, summer and autumn in stratified hauls (according to hydrographic characteristics), by means of a 0.180-mm Multi Plankton Sampler. A strong front between the open sea and the fjord waters was observed during the spring, preventing water mass exchange, but was not observed later in the season. The considerable seasonal changes in zooplankton abundance were related to the seasonal variation in hydrographical regime. The total zooplankton abundance during the spring (40–2010 individuals m−3 ) was much lower than in the summer and autumn (410–10 560 individuals m−3 ). The main factors shaping the zooplankton community in the fjord include: the presence of a local front, advection, the flow pattern and the decreasing depth of the basin in the inner fjord. Presumably these factors regulate the gross pattern of zooplankton density and distribution, and override the importance of biological processes. This study increased our understanding of seasonal processes in fjords, particularly with regard to the strong seasonal variability in the Arctic. 相似文献
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Analysis of till micromorphology represents a relatively new technique that has been used most frequently to infer the importance of subglacial shear in till genesis. This study aims to calibrate the technique by comparing Pleistocene tills from United Kingdom with a modern till (the UpB till) from beneath Ice Stream B, West Antarctica. Despite the fact that all of the tills examined have been interpreted as deforming‐bed deposits, the modern till has significantly less abundant and diverse microstructures than those found in the Pleistocene tills. Seventeen examined thin‐sections of the UpB till contain recognisable microstructures over only 0–30% of individual thin‐section area. The most common microstructures are: (i) birefringent clay patterns that are interpreted as shear zones and (ii) adherent matrix structures, which we interpret as uncomminuted remnants of the parent glacial/glaciomarine diamictons. Fourteen thin‐sections of the Pleistocene tills were covered by microstructures in 10–95% of their area. The Pleistocene microstructures include birefringent clays and adherent matrix structures, as in the UpB till, but also laminations and deformed pods made of chalk and sorted sediments. We conclude that the same till‐forming process, i.e. subglacial deformation, may result in distinctly different till micromorphology. This is a consequence of the fact that microstructural characteristics are strongly influenced by factors other than shear deformation. We identify three controls that may be important for forming contrasting microstructural assemblages: (i) strain magnitude, (ii) the degree of heterogeneity of parent material, and (iii) relative importance of sediment sorting by flowing water in the subglacial environment. Thus till micromorphology is sensitive to multiple factors, which with proper calibration may enhance the existing capability to interpret past subglacial conditions from microstructures. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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Ian M. Howat Slawek Tulaczyk Philip Rhodes Kevin Israel Mark Snyder 《Climate Dynamics》2007,28(1):85-98
Temperature is often seen as the dominant control on inter-decadal glacier volume changes. However, despite regional warming over the past half-century, the glaciers of Mount Shasta have continued to expand following a contraction during a prolonged drought in the early twentieth century, indicating a greater sensitivity to precipitation than temperature. We use the 110 year record of fluctuations in Mount Shasta’s glaciers and climate to calibrate numerical glacier models of the two largest glaciers. The reconstructed balance and volume histories show a much greater correlation to precipitation than temperature and significant correlation to oscillatory modes of Pacific Ocean climate. An approximately 20% increase in precipitation is needed for every 1°C increase in temperature to maintain stability. Under continued historical trends, oscillations in climate modes and random variability will dominate inter-decadal variability in ice volume. Under the strong warming trend predicted by a regional climate model, the temperature trend will be the dominant forcing resulting in near total loss of Mount Shasta’s glaciers by the end of the twenty-first century.Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at . 相似文献
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岩体节理表面形貌的各向异性研究 总被引：5，自引：0，他引：5
本文根据激光表面仪测量的节理表面形貌数据,通过将高度分布转化为斜率分布、并对斜率分布采用频谱分析的方法,研究了节理表面形貌的各向异性特征。一般的统计参数只能给出节理表面剖线某种性质的平均测度,很难捕捉节理表面的各向异性性质。而功率谱密度全面反映了节理表面形貌中大尺度上的起伏和小尺度上的涨落,具有一般统计参数不可比拟的优越性,通过定义累计功率谱密度指数psd*的方法,定量地表征了岩体节理表面的各向异性。 相似文献
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