Deglaciation of the western margin of the Barents Sea Ice Sheet — A swath bathymetric and sub-bottom seismic study from the Kveithola Trough     

Michele Rebesco  Yanguang Liu  Angelo Camerlenghi  Monica Winsborrow  Jan Sverre Laberg  Andrea Caburlotto  Paolo Diviacco  Daniela Accettella  Chiara Sauli  Nigel Wardell  Isabella Tomini 《Marine Geology》2011,279(1-4):141-147

Kveithola Trough, an E–W trending glacial trough in the NW Barents Sea, was surveyed for the first time during the EGLACOM cruise of R/V OGS-Explora in summer 2008. Swath bathymetry shows that the seafloor is characterized by E–W trending mega-scale glacial lineations (MSGL) that record a fast flowing ice stream draining the Svalbard/Barents Sea Ice Sheet (SBIS) during the Last Glacial Maximum (LGM). MSGL are overprinted by transverse sediment ridges about 15 km apart which give rise to a staircase axial profile of the trough. Such transverse ridges are interpreted to be grounding-zone wedges (GZWs) formed by deposition of subglacial till during episodic ice stream retreat. Sub-bottom (CHIRP) and multi-channel reflection seismic data show that the present-day morphology is largely inherited from the palaeo-seafloor topography at the time of deposition of the transverse ridges, overlain by a draping glaciomarine unit which in places is over 15 m thick. Our data allow the reconstruction of depositional processes which accompanied deglaciation of the Spitsbergen Bank area. The sedimentary drape deposited on top of the GZWs is suggested to have accumulated at a very high rate, (on average in the order of 1–1.5 m ka^?1) and therefore may potentially preserve a high-resolution palaeoclimatic record of deglaciation and post-glacial conditions in this sector of the Barents Sea.  相似文献   

Spatial pattern of coastal fish assemblages in different habitats in North‐western Mediterranean     

Gabriele La Mesa  Andrea Molinari  Silvia Gambaccini  Leonardo Tunesi 《Marine Ecology》2011,32(1):104-114

Variability of fish assemblages across habitat structures can depend on spatial scales. A hierarchical sampling design was used to assess the spatial variability of temperate fish assemblages in different habitats and at multiple scales. Underwater visual censuses were carried out along the coasts of Elba Island (NW Mediterranean) on Posidonia oceanica beds, rocky algal reefs and sandy habitat at three spatial scales, namely tens of metres (individual replicates), hundreds of metres (sites) and tens of kilometres (locations). At the assemblage level, there was a clear relationship between fish and habitat type and the observed habitat‐related differences were largely dependent on species identity. Fish assemblages on P. oceanica beds and rocky reefs shared a high number of species, whereas overlap with sandy assemblages was negligible. Multivariate analyses revealed significant differences in fish assemblages among habitats, although there was also a significant habitat × site interaction. These differences relied mainly upon assemblage composition and species richness. Assemblages on rocky reefs and P. oceanica meadows usually harboured a higher number of species and individuals compared with sandy assemblages. Nevertheless, the patterns of habitat‐related differences in species richness and, especially, in the total number of fish, changed significantly from site to site. Eight species showed significant differences over habitats, but they were not consistent due to the interaction of habitat with site. Predictability of fish at both assemblage and population levels decreased with the scale of observation, and the spatial pattern of fish observed at the smallest scale was likely dependent on factors other than habitat type.  相似文献   

Lagrangian model of zooplankton dispersion: numerical schemes comparisons and parameter sensitivity tests     

丘仲锋  何宜军 《中国海洋湖沼学报》2011,29(2):438-445

This paper presents two comparisons or tests for a Lagrangian model of zooplankton dispersion:numerical schemes and time steps.Firstly,we compared three numerical schemes using idealized circulations.Results show that the precisions of the advanced Adams-Bashfold-Moulton(ABM) method and the Runge-Kutta(RK) method were in the same order and both were much higher than that of the Euler method.Furthermore,the advanced ABM method is more efficient than the RK method in computational memory requirements and time consumption.We therefore chose the advanced ABM method as the Lagrangian particle-tracking algorithm.Secondly,we performed a sensitivity test for time steps,using outputs of the hydrodynamic model,Symphonie.Results show that the time step choices depend on the fluid response time that is related to the spatial resolution of velocity fields.The method introduced by Oliveira et al.in 2002 is suitable for choosing time steps of Lagrangian particle-tracking models,at least when only considering advection.  相似文献   

Preface     

Nadine Chaumerliac  Andrea Flossmann 《Atmospheric Research》2001,58(4):229

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Spectral mapping of rock weathering degrees on granite using hyperspectral DAIS 7915 spectrometer data   总被引：1，自引：0，他引：1  

Asuncin Riaza  Peter Strobl  Ulrich Beisl  Andrea Hausold  Andreas Müller 《International Journal of Applied Earth Observation and Geoinformation》2001,3(4):345

Rocks are weathered by chemical and physical processes into a mixture of loose material that produces soil. Mineralogical and textural changes are involved, which can be detected by imagery through digital image processing based on rock spectral behaviour as recorded by ground and laboratory spectrometers. Different densities of vegetation cover can be mapped qualifying further evolution of the area in terms of erosion, transport and sedimentation. Hyperspectral imagery helps to map the weathering front and different degrees of weathering on granite rock through mineralogical and textural associations related to the geomorphological processes in the area on various granitic facies. Abundance of feldspar and porfidic texture on the fresh rock are the critical parameters conditioning intensity of weathering in the area. Maps spectrally elaborated gather information on lithologies, mineralogical changes produced by geomorphological processes associated to landforms, topography and climate. Such maps contribute to estimating the spatial controls of erosion, suggesting soil particle size distribution, soil aggregation, soil depth, and consequently, helping to elaborate soil loss and soil conservation maps.  相似文献   

Problems in automated recognition of valley features from digital elevation models and a new method toward their resolution     

Andrea Tribe 《地球表面变化过程与地形》1992,17(5):437-454

Valley recognition methods given in the literature fail to produce valley networks suitable for locating valley heads for one of two main reasons: (a) they are based on the concept of [higher than] or (b) they are based on contributing area thresholds. In this paper a new method for recognizing valley bottoms is presented. This is based on two improvements of Carroll's (1983) method, and produces a network that reflects the topography well. The network is used to locate valley heads. Once located, the valley heads are delineated using criteria suggested by geomorphologists and hydrologists. The resultant valley heads are generally well recognized although two problems are evident: (a) there are a number of commission errors; and (b) the valley heads recognized by the method are too small.  相似文献   

Automated recognition of valley heads from digital elevation models     

Andrea Tribe 《地球表面变化过程与地形》1991,16(1):33-49

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Book review     

Richard Barakat  Petr Vanicek  Randall L. Mackie  Jacek A. Majorowicz  Ley Truskinovsky  Andrea Borgia  Steven Carey  Ursula B. Marvin 《Pure and Applied Geophysics》1990,134(3):485-507

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Connections and Collaborations of Local Water Management Organizations of Utah     

Andrea Armstrong  Douglas Jackson-Smith 《社会与自然资源》2017,30(11):1343-1357

Fragmented water governance arrangements complicate sustainable water management in the western U.S. where local water management organizations (LWMOs), including municipalities and irrigation groups, directly manage water conveyance systems. LWMOs make critical decisions that determine water delivery and management, but have traditionally not collaborated with one another. Our research examines the ways in which LWMOs are increasingly interconnected within a context of widespread urbanization. We draw on three years of qualitative research on LWMOs in Utah, including interviews and in-depth qualitative case studies, to analyze the conditions under which collaborations between LWMOs emerge, or have not yet occurred. Our findings indicate that historically fragmented LWMOs are engaging in cooperative efforts based on their extensive water infrastructure connections. LWMOs did not transform cooperative efforts into collaborations unless such a collaboration protected internal interests. LWMOs engaged in collaborations primarily to reduce their liabilities in the instance of infrastructure failure.  相似文献   

Geological structure and kinematics of normal faults in the Otway Basin,Australia, based on quantitative analysis of 3‐D seismic reflection data          下载免费PDF全文

Jennifer Ziesch  Chiara M. Aruffo  David C. Tanner  Thies Beilecke  Tess Dance  Andreas Henk  Bastian Weber  Eric Tenthorey  Andrea Lippmann  Charlotte M. Krawczyk 《Basin Research》2017,29(2):129-148

The Otway Basin in the south of Victoria, Australia underwent three phases of deformation during breakup of the southern Australian margin. We assess the geometry and kinematics of faulting in the basin by analysing a 3‐D reflection seismic volume. Eight stratigraphic horizons and 24 SW‐dipping normal faults as well as subordinate antithetic faults were interpreted. This resulted in a high‐resolution geological 3‐D model (ca. 8 km × 7 km × 4 km depth) that we present as a supplementary 3‐D PDF (Data S1). We identified hard‐ and soft‐linking fault connections over the entire area, such as antithetic faults and relay ramps, respectively. Most major faults were continuously active from Early to Late Cretaceous, with two faults in the northern part of the study area active until at least the Oligocene. Allan maps of faults show tectonic activity continuously waned over this time period. Isopach maps of stratigraphic volumes quantify the amount of syn‐sedimentary movement that is characteristic of passive margins, such as the Otway Basin. We show that the faults possess strong corrugations (with amplitudes above the seismic resolution), which we illustrated by novel techniques, such as cylindricity and curvature. We argue that the corrugations are produced by sutures between sub‐vertical fault segments and this morphology was maintained during fault growth. Thus, they can be used to indicate the kinematics vector of the fault movement. This evidences, together with left‐stepping relay ramps, that 40% of the faults had a small component (up to 25°) of dextral oblique slip as well as normal (dip‐slip) movement.  相似文献