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1.
The coupling of physics and biology was examined along a 160 km long transect running out from the north coast of South Georgia Island and crossing the Southern Antarctic Circumpolar Current Front (SACCF) during late December 2000. Surface and near surface potential TS properties indicated the presence of three water types: a near-shore group of stations characterised by water which became progressively warmer and fresher closer to South Georgia, an offshore grouping in which sea surface temperatures and those at the winter water level were relatively warm (1.8°C and 0.5°C, respectively), and a third in which surface and winter water temperatures were cooler and reflected the presence of the SACCF. The transect bisected the SACCF twice, revealing that it was flowing in opposite directions, north-westward closest to South Georgia and south-eastwards at its furthest point from the island. The innermost limb was a narrow intense feature located just off the shelf break in 2000–3500 m of water and in which rapid surface baroclinic velocities (up to 35 cm s−1) were encountered. Offshore in the outermost limb, shown subsequently to be a mesoscale eddy that had meandered south from the retroflected limb of the SACCF, flow was broader and slower with peak velocities around 20 cm s−1. Chlorophyll a biomass was generally low (<1 mg m−3) over much of the transect but increased dramatically in the region of the innermost limb of the SACCF, where a deepening of the surface mixed layer was coincident with a subsurface chlorophyll maximum (7.4 mg m−3) and elevated concentrations down to 100 m. The bloom was coincident with depleted nutrient concentrations, particularly silicate, nitrate and phosphate, and although ammonium concentrations were locally depleted the bloom lay within an elevated band (up to 1.5 mmol m−3) associated with the frontal jet. Increased zooplankton abundance, higher copepod body carbon mass and egg production rates all showed a strong spatial integrity with the front. The population structure of the copepods Calanoides acutus and Rhincalanus gigas at stations within the front suggested that rather than simply resulting from entrainment and concentration within the jet, increased copepod abundance was the result of development in situ. Estimates of bloom duration, based on silicate and carbon budget calculations, set the likely duration between 82 and 122 d, a figure supported by the development schedule of the two copepod species. Given this timescale, model outputs from FRAM and OCCAM indicated that particles that occurred on the north side of South Georgia in December would have been in the central-southern Scotia Sea 2–3 months earlier, probably in sea ice affected regions.  相似文献   
2.
We developed a spatially explicit, individual-based model to analyze how hypoxia effects on reproduction, growth, and mortality of Atlantic croaker in the northwestern Gulf of Mexico lead to population-level responses. The model follows the hourly growth, mortality, reproduction, and movement of individuals on a 300 × 800 spatial grid of 1-km2 cells for 140 years. Chlorophyll-a concentration, water temperature, and dissolved oxygen (DO) were specified daily for each grid cell and repeated for each year of the simulation. A bioenergetics model was used to represent growth, mortality was assumed stage- and age-dependent, and the movement behavior of juveniles and adults was modeled based on temperature and avoidance of low DO. Hypoxia effects were imposed using exposure effect submodels that converted time-varying exposures to low DO to reduced hourly growth, increased hourly mortality, and reduced annual fecundity. Results showed that 100 years of either mild or intermediate hypoxia produced small reductions in population abundance, while repeated severe hypoxia caused a 19% reduction in long-term population abundance. Relatively few individuals were exposed to low DO each hour, but many individuals experienced some exposure. The response was dominated by a 5% average reduction in annual fecundity of individuals. Under conditions of random sequences of mild, intermediate, and severe hypoxia years occurring in proportion to their historical frequency, the model predicted a 10% decrease in the long-term population abundance of croaker. A companion paper substitutes hourly DO values from a three-dimensional water quality model for the idealized hypoxia and results in a more realistic population reduction of about 25%.  相似文献   
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4.
This paper discusses social network interactions among individuals who have been hospitalized with mental illness and who currently reside in different types of community housing programmes. First, a conceptualisation of social networks that focuses on network interactions, both supportive and non-supportive, between network interactions may be more important influences on successful or unsuccessful adaptation of current and former psychiatric patients to community life than the structural dimensions of social networks more commonly analysed in the literature. The design of a current longitudinal study of social network interactions is presented. The results of two pilot studies that examine social network interactions is presented. The results of two pilot studies that examine social network interactions with data from several community housing programmes in southern Ontario, Canada are reviewed and an agenda is stated for further data collection and analysis.  相似文献   
5.
The inclination of M31 is too close to edge-on for a bar component to be easily recognized and is not sufficiently edge-on for a boxy/peanut bulge to protrude clearly out of the equatorial plane. Nevertheless, a sufficient number of clues allow us to argue that this galaxy is barred. We use fully self-consistent N -body simulations of barred galaxies and compare them with both photometric and kinematic observational data for M31. In particular, we rely on the near-infrared photometry presented in a companion paper. We compare isodensity contours to isophotal contours and the light profile along cuts parallel to the galaxy major axis and offset towards the north, or the south, to mass profiles along similar cuts on the model. All these comparisons, as well as position–velocity diagrams for the gaseous component, give us strong arguments that M31 is barred. We compare four fiducial N -body models to the data and thus set constraints on the parameters of the M31 bar, as its strength, length and orientation. Our 'best' models, although not meant to be exact models of M31, reproduce in a very satisfactory way the main relevant observations. We present arguments that M31 has both a classical and a boxy/peanut bulge. Its pseudo-ring-like structure at roughly 50 arcmin is near the outer Lindblad resonance of the bar and could thus be an outer ring, as often observed in barred galaxies. The shape of the isophotes also argues that the vertically thin part of the M31 bar extends considerably further out than its boxy bulge, that is, that the boxy bulge is only part of the bar, thus confirming predictions from orbital structure studies and from previous N -body simulations. It seems very likely that the backbone of M31's boxy bulge is families of periodic orbits, members of the x1-tree and bifurcating from the x1 family at its higher order vertical resonances, such as the x1v3 or x1v4 families.  相似文献   
6.
Few assessments of species vulnerability to climate change used to inform conservation management consider the intrinsic traits that shape species’ capacity to respond to climate change. This omission is problematic as it may result in management actions that are not optimised for the long-term persistence of species as climates shift. We present a tool for explicitly linking data on plant species’ life history traits and range characteristics to appropriate management actions that maximise their capacity to respond to climate change. We deliberately target data on easily measured and widely available traits (e.g. dispersal syndrome, height, longevity) and range characteristics (e.g. range size, climatic/soil niche breadth), to allow for rapid comparison across many species. We test this framework on 1237 plants, categorising species on the basis of their potential climate change risk as related to four factors affecting their response capacity: reproduction, movement capability, abiotic niche specialisation and spatial coverage. Based on these four factors, species were allocated risk scores, and these were used to test the hypothesis that the current protection status under national legislation and related management actions capture species response capacity to climate change. Our results indicate that 20% of the plant species analysed (242 species) are likely to have a low capacity to respond to climate change based on the traits assessed, and are therefore at high risk. Of the 242 high risk species, only 10% (24 species) are currently listed for protection under conservation legislation. Importantly, many management plans for these listed species fail to address the capacity of species to respond to climate change with appropriate actions: 70% of approved management plans do not include crucial actions which may improve species’ ability to adapt to climate change. We illustrate how the use of easily attainable traits associated with ecological and evolutionary responses to changing environmental conditions can inform conservation actions for plant species globally.  相似文献   
7.
The Holocene evolution of the Canning Coast of Western Australia has largely been overlooked so far mainly due to its remoteness and low population density. We report on new data from a sequence of foredunes inside the macro‐tidal Admiral Bay, 110 km southwest of Broome. Based on sediment cores, differential global positioning system (dGPS)‐based elevation transects, and stratigraphical analyses on outcrops of the relict foredunes, we aim at reconstructing Holocene coastal changes and relative sea levels (RSLs), as well as identifying and dating imprints of extreme‐wave events. Sedimentary analyses comprise the documentation of bedding structures, foraminiferal content and macrofaunal remains, grain size distribution, and organic matter. The chronological framework is based on 26 carbon‐14 accelerator mass spectrometry (14C‐AMS) datings. Marine flooding of the pre‐Holocene surface landward of the 2.5 km‐wide foredune barriers occurred 7400–7200 cal bp , when mangroves colonized the area. After only 200–400 years, a high‐energy inter‐tidal environment established and prevailed until c. 4000 cal bp , before turning into the present supralittoral mudflat. During that time, coastal regression led to beach progradation and the formation of aligned foredunes. Drivers of progradation were a stable RSL or gradual RSL fall after the mid‐Holocene and a positive sand budget. The foredunes overlie upper beach deposits located up to >2 m above the present upper beach level and provide evidence for a higher mid‐Holocene RSL. Discontinuous layers of coarse shells and sand are intercalated in the foredunes, indicating massive coastal flooding events. One such layer was traced over three dune ridges and dated to c. 1700–1550 cal bp . However, it seems that most tropical cyclones induce net erosion rather than deposition at aligned foredunes and thus, they are only suitable for reconstructing temporal variability if erosional features or sedimentation reliably tied to these events can be identified and dated accurately. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
8.
The Antarctic climate system involves many complex interactions between the atmosphere, oceans and ice and is sensitive to variations in these components. Ice shelves represent the ice–ocean–atmosphere interface of the Antarctic continent and are therefore very important indicators of climate change in the region. The Amery Ice Shelf is the largest ice shelf in East Antarctica and has been the focus of many scientific research projects over the past 50 years. This paper presents a history of the use of spatial science techniques from basic survey equipment to satellite systems in Australian research projects based on the Amery Ice Shelf (and surrounding glaciers) since 1955. The application of these spatial data to projects based primarily in the fields of geodesy, glaciology, climatology, and oceanography has allowed the measurement and monitoring of the physical, dynamic and environmental characteristics of this large and remote region. This new information provides scientists with a better understanding of the ice shelf/ocean/atmosphere system allowing future monitoring to observe the effects of global climate change.  相似文献   
9.
This paper presents the first attempt to use environmental magnetism to quantify sediment provenance on a managed realignment (MR) site. MR is one technique for creating/restoring intertidal habitats and improving the standard of coastal flood protection. Monitoring of MR sites is essential for determining how successful they are at achieving these aims, and normally includes measurement of sedimentation rates through the use of accretion plates and sediment erosion tables (SETs). One limitation of this technique is that the provenance of sediment accreting on realigned surfaces cannot readily be quantified. Our results demonstrate that magnetics-based fingerprinting can successfully apportion sediment source contributions to created/restored coastal saltmarshes with an efficiency similar to that of existing un-mixing models applied to other habitats (82.87%). Analysis of mineral magnetic properties (χFD, IRMsoft and SIRM) demonstrated that the majority of sediment accreting on the Freiston Shore MR Site (Lincolnshire, UK) is derived from established saltmarshes seaward of the breached embankment. This indicates that the MR site may be growing at the expense of neighbouring saltmarshes—thereby undermining the habitat-creation objectives used to justify MR. It is recommended that future MR monitoring programmes consider the provenance of post-breach deposits to help identify any adverse impacts that wetland creation/restoration may have on existing habitats. Further testing of environmental magnetism in coastal saltmarshes and MR sites is necessary to validate wider use of the technique.  相似文献   
10.
Improving conveyance of uncertainties in the findings of the IPCC   总被引:1,自引:0,他引:1  
Authors of the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) received guidance on reporting understanding, certainty and/or confidence in findings using a common language, to better communicate with decision makers. However, a review of the IPCC conducted by the InterAcademy Council (2010) found that “the guidance was not consistently followed in AR4, leading to unnecessary errors . . . the guidance was often applied to statements that are so vague they cannot be falsified. In these cases the impression was often left, quite incorrectly, that a substantive finding was being presented.” Our comprehensive and quantitative analysis of findings and associated uncertainty in the AR4 supports the IAC findings and suggests opportunities for improvement in future assessments.  相似文献   
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