The age as a diagnostic of the dynamics of marine ecosystem models     

éric J.M.?DelhezEmail author  Geneviève?Lacroix  éric?Deleersnijder 《Ocean Dynamics》2004,54(2):221-231

The constituent-oriented age theory (CAT) worked out by Delhez et al. (1999) is a flexible tool that can be applied to diagnose complex models. It is shown here how this can be used to quantify the pace at which an ecosystem model works. At the cost of the introduction of one additional evolution equation for each compartment of the ecosystem model, the mean age of the biological material forming these compartments can be computed. The information obtained in this way complements the information provided by the concentration data; while the latter measures the standing stocks, the former provides an integrated assessment of the interaction rates and matter fluxes. The benefits of the method are demonstrated with a simple Lotka–Volterra system and a one-dimensional vertical model of the nitrogen cycle in the Ligurian Sea. The theory can be used to study the biological compartments individually or the ecosystem as a whole. In particular, the age is a valuable tool to quantify the overall cycling rate of nitrogen in the food web.Responsible Editor: Phil Dyke  相似文献   

Mediterranean fin whales at risk from fatal ship strikes     

Panigada S  Pesante G  Zanardelli M  Capoulade F  Gannier A  Weinrich MT 《Marine pollution bulletin》2006,52(10):1287-1298

This paper reviews and analyzes ship collision records for the relatively isolated population of fin whales in the Mediterranean Sea from 1972 to 2001. Out of 287 carcasses, 46 individuals (16.0%) were certainly killed by boats. The minimum mean annual fatal collision rate increased from 1 to 1.7 whales/year from the 1970s to the 1990s. Fatal strike events (82.2%) were reported in or adjacent to the Pelagos Sanctuary, characterized by high levels of traffic and whale concentrations. Among 383 photo-identified whales, 9 (2.4%) had marks that were attributed to a ship impact. The reported rates are unusually high for baleen whales. The high likelihood of unreported fatal strikes combined with other anthropogenic threats suggests an urgent need for a comprehensive, basin-wide conservation strategy, including ship strike mitigation requirements, like real-time monitoring of whale presence and distribution to re-locate ferry routes to areas of lower cetacean density, and reducing ship speed in high cetacean density areas.  相似文献   

SPATIAL AND THERMAL CHARACTERISTICS OF MOUNTAIN PERMAFROST,NORTHWEST CANADA     

ANTONI G. LEWKOWICZ  PHILIP P. BONNAVENTURE  SHARON L. SMITH  ZOÉ KUNTZ 《Geografiska Annaler: Series A, Physical Geography》2012,94(2):195-213

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Analysis of the Devonian (Frasnian) platform from Belgium: a multi‐faceted approach for basin evolution reconstruction     

Anne‐Christine Da Silva  Frédéric Boulvain 《Basin Research》2012,24(3):338-356

This study undertakes a multi‐disciplinary approach (sedimentology, carbon isotopes, magnetic susceptibility and thickness distribution) to improve understanding of a major Palaeozoic carbonate platform, the Frasnian platform of Belgium. These combined techniques are used to reconstruct the platform history, which evolved in two main steps. During the first phase, the basin was strongly influenced by faulting, producing notable thickness and facies variations, with open ocean conditions, with good water circulation and no/or limited barrier reef. The second phase of platform development was less influenced by differential subsidence, as indicated by homogeneous facies distribution. However, this platform developed under restricted waters, with low circulation which is likely related to the development of a barrier reef.  相似文献   

Current state and trends in Canadian Arctic marine ecosystems: II. Heterotrophic food web, pelagic-benthic coupling, and biodiversity     

Gérald Darnis  Dominique Robert  Corinne Pomerleau  Heike Link  Philippe Archambault  R. John Nelson  Maxime Geoffroy  Jean-éric Tremblay  Connie Lovejoy  Steve H. Ferguson  Brian P. V. Hunt  Louis Fortier 《Climatic change》2012,115(1):179-205

As part of the Canadian contribution to the International Polar Year (IPY), several major international research programs have focused on offshore arctic marine ecosystems. The general goal of these projects was to improve our understanding of how the response of arctic marine ecosystems to climate warming will alter food web structure and ecosystem services provided to Northerners. At least four key findings from these projects relating to arctic heterotrophic food web, pelagic-benthic coupling and biodiversity have emerged: (1) Contrary to a long-standing paradigm of dormant ecosystems during the long arctic winter, major food web components showed relatively high level of winter activity, well before the spring release of ice algae and subsequent phytoplankton bloom. Such phenological plasticity among key secondary producers like zooplankton may thus narrow the risks of extreme mismatch between primary production and secondary production in an increasingly variable arctic environment. (2) Tight pelagic-benthic coupling and consequent recycling of nutrients at the seafloor characterize specific regions of the Canadian Arctic, such as the North Water polynya and Lancaster Sound. The latter constitute hot spots of benthic ecosystem functioning compared to regions where zooplankton-mediated processes weaken the pelagic-benthic coupling. (3) In contrast with another widely shared assumption of lower biodiversity, arctic marine biodiversity is comparable to that reported off Atlantic and Pacific coasts of Canada, albeit threatened by the potential colonization of subarctic species. (4) The rapid decrease of summer sea-ice cover allows increasing numbers of killer whales to use the Canadian High Arctic as a hunting ground. The stronger presence of this species, bound to become a new apex predator of arctic seas, will likely affect populations of endemic arctic marine mammals such as the narwhal, bowhead, and beluga whales.  相似文献   

Dynamics of sea-surface temperature anomalies in the Southern Ocean diagnosed from a 2D mixed-layer model     

Frédéric Vivier  Daniele Iudicone  Fabiano Busdraghi  Young-Hyang Park 《Climate Dynamics》2010,34(2-3):153-184

We analyze the processes responsible for the generation and evolution of sea-surface temperature anomalies observed in the Southern Ocean during a decade based on a 2D diagnostic mixed-layer model in which geostrophic advection is prescribed from altimetry. Anomalous air–sea heat flux is the dominant term of the heat budget over most of the domain, while anomalous Ekman heat fluxes account for 20–40% of the variance in the latitude band 40°?60°S. In the ACC pathway, lateral fluxes of heat associated with anomalous geostrophic currents are a major contributor, dominating downstream of several topographic features, reflecting the influence of eddies and frontal migrations. A significant fraction of the variability of large-scale SST anomalies is correlated with either ENSO or the SAM, each mode contributing roughly equally. The relation between the heat budget terms and these climate modes is investigated, showing in particular that anomalous Ekman and air–sea heat fluxes have a co-operating effect (with regional exceptions), hence the large SST response associated with each mode. It is further shown that ENSO- or SAM-locked anomalous geostrophic currents generate substantial heat fluxes in all three basins with magnitude comparable with that of atmospheric forcings for ENSO, and smaller for the SAM except for limited areas. ENSO-locked forcings generate SST anomalies along the ACC pathway, and advection by mean flows is found to be a non-negligible contribution to the heat budget, exhibiting a wavenumber two zonal structure, characteristic of the Antarctic Circumpolar Wave. By contrast SAM-related forcings are predominantly zonally uniform along the ACC, hence smaller zonal SST gradients and a lesser role of mean advection, except in the SouthWest Atlantic. While modeled SST anomalies are significantly correlated with observations over most of the Southern Ocean, the analysis of the data-model discrepancies suggests that vertical ocean physics may play a significant role in the nonseasonal heat budget, especially in some key regions for mode water formation.  相似文献   

Nuclear modification factor for quarkonium production in high energy proton-nucleus collisions within the parton saturation approach     

Érison S. Rocha  Magno V. T. Machado 《Astronomische Nachrichten》2024,345(2-3):e230165

In this work, we analyze nuclear effects in the inclusive production of quarkonium in proton-nucleus collisions at high energy regime. A theoretical framework that includes initial state effects like nuclear shadowing and gluon density saturation is considered. Numerical results for nuclear modification factor, $R_{pA}(y)$, as a function of meson rapidity in proton-nucleus collisions are presented. The parameter-free predictions are compared to the available data from the Large Hadron Collider. Discussion on the main theoretical uncertainties is made, with emphasis on the phenomenological models for the nuclear saturation scale.  相似文献   

A parametric study of stability and resonances around L 4 in the elliptic restricted three-body problem     

Bálint Érdi  Emese Forgács-Dajka  Imre Nagy  Renáta Rajnai 《Celestial Mechanics and Dynamical Astronomy》2009,104(1-2):145-158

The size of the stable region around the Lagrangian point L ₄ in the elliptic restricted three-body problem is determined by numerical integration as a function of the mass parameter and eccentricity of the primaries. The size distribution of the stable regions in the mass parameter-eccentricity plane shows minima at certain places that are identified with resonances between the librational frequencies of motions around L ₄. These are computed from an approximate analytical equation of Rabe relating the frequency, mass parameter and eccentricity. Solutions of this equation are determined numerically and the global behaviour of the frequencies depending on the mass parameter and eccentricity is shown and discussed. The minimum sizes of the stable regions around L ₄ change along the resonances and the relative strength of the resonances is analysed. Applications to possible Trojan exoplanets are indicated. Escape from L ₄ is also investigated.  相似文献   

Modelling of sediment supply from torrent catchments in the Western Alps using the sediment contributing area (SCA) approach     

Moritz Altmann  Florian Haas  Tobias Heckmann  Frédéric Liébault  Michael Becht 《地球表面变化过程与地形》2021,46(5):889-906

The production of coarse sediment in mountain landscapes depends mainly on the type and activity of geomorphic processes and topographic and natural conditions (e.g. vegetation cover) of these catchments. The supply of sediment from these slopes to mountain streams and its subsequent transport lead to sediment connectivity, which describes the integrated coupled state of these systems. Studies from the Northern Calcareous Alps show that the size of the sediment contributing area (SCA), a subset of the drainage area that effectively delivers sediment to the channel network, can be used as a predictor of sediment delivery to mountain streams. The SCA concept is delineated on a digital elevation model (DEM) using a set of rules related to the steepness and length of slopes directly adjacent to the channel network, the gradient of the latter and the vegetation cover. The present study investigates the applicability of this concept to the Western Alps to identify geomorphologically active areas and to estimate mean annual sediment yield (SY) in mainly debris-flow-prone catchments. We use a statistical approach that shows a parameter optimisation and a linear regression of SY on SCA extent. We use a dataset of ~25 years of assessed coarse sediment accumulation in 35 sediment retention basins. In the investigated catchments, sediment transport is governed by several factors, mainly by the extent of vegetation-free areas with a minimum slope of 23° that is coupled to the channel network with a very low gradient of the latter. With our improved framework, we can show that the SCA approach can be applied to catchments that are widely distributed, in a large spatial scale (hectare area) and very heterogeneous in their properties. In general, the investigated catchments show high connectivity, resulting in significant correlations between long-term average yield and the size of the SCA.  相似文献   

‘Box‐Profile’ Ion Implants as Geochemical Reference Materials for Electron Probe Microanalysis and Secondary Ion Mass Spectrometry     

Haosheng Wu  Roman Bttger  Frdric Couffignal  Jens Gutzmer  Joachim Krause  Frans Munnik  Axel D. Renno  Ren Hübner  Michael Wiedenbeck  Ren Ziegenrücker 《Geostandards and Geoanalytical Research》2019,43(4):531-541

Although electron probe microanalysis and secondary ion mass spectrometry are widely used analytical techniques for geochemical and mineralogical applications, metrologically rigorous quantification remains a major challenge for these methods. Secondary ion mass spectrometry (SIMS) in particular is a matrix‐sensitive method, and the use of matrix‐matched reference materials (RMs) is essential to avoid significant analytical bias. A major problem is that the number of available RMs for SIMS is extremely small compared with the needs of analysts. One approach for the production of matrix‐specific RMs is the use of high‐energy ion implantation that introduces a known amount of a selected isotope into a material. We chose the more elaborate way of implanting a so‐called ‘box‐profile’ to generate a quasi‐homogeneous concentration of the implanted isotope in three dimensions, which allows RMs not only to be used for ion beam analysis but also makes them suitable for EPMA. For proof of concept, we used the thoroughly studied mineralogically and chemically ‘simple’ SiO₂ system. We implanted either ⁴⁷Ti or ⁴⁸Ti into synthetic, ultra‐high‐purity silica glass. Several ‘box‐profiles’ with mass fractions between 10 and 1000 μg g^?1 Ti and maximum depths of homogeneous Ti distribution between 200 nm and 3 μm were produced at the Institute of Ion Beam Physics and Materials Research of Helmholtz‐Zentrum Dresden‐Rossendorf. Multiple implantation steps using varying ion energies and ion doses were simulated with Stopping and Range of Ions in Matter (SRIM) software, optimising for the target concentrations, implantation depths and technical limits of the implanter. We characterised several implant test samples having different concentrations and maximum implantation depths by means of SIMS and other analytical techniques. The results show that the implant samples are suitable for use as reference materials for SIMS measurements. The multi‐energy ion implantation technique also appears to be a promising procedure for the production of EPMA‐suitable reference materials.  相似文献