Risks of shifting baselines highlighted by anecdotal accounts of New Zealand's snapper (Pagrus auratus) fishery     

Darren M. Parsons  Mark A. Morrison  Alison B. MacDiarmid  Bruce Stirling  Phillip Cleaver  Ian W.G. Smith 《新西兰海洋与淡水研究杂志》2013,47(4):965-983

Anecdotal data sources may constitute an important component of the information available about an exploited species, as record keeping may not have occurred until after exploitation began. Here, we aimed to fill any gaps in the exploitative history of the sparid snapper (Pagrus auratus), using social and historical research methods. Social research consisted of interviews with recreational fishers, focusing on the most and largest snapper they had caught. In addition, the diary‐logs of two recreational fishers were analysed. Historical research consisted of investigation of old books, photos, archives and unpublished sources unconventional to fishery science. Interviews with fishers demonstrated no or weak trends in snapper abundance or size, and were likely impeded by a lack of ability to detect change in a fish stock that may still be considered abundant. The fishers’ perception of change, however, largely reflected recent experiences (last c. 10 years), when biomass is understood to have increased, and mostly did not consider experiences before the 1980s. Alternatively, diary‐logs of fisher catch rates produced a pattern that matched formal stock assessments of snapper biomass, suggesting declines in abundance up until the 1990s and an increase in biomass after that time. Historical research, although more qualitative, had the ability to investigate periods where formal records were not kept and described a fishery vastly different from the current one. Snapper were easily caught, in great abundance and in unusual locations. Localised depletion of snapper was first noticed in the early 20th century, despite spectacular catches of snapper occurring after that time. Snapper behaviour was also likely different, with visual sightings of snapper by onlookers a common occurrence. Although predictions from stock assessment models are consistent with that of the anecdotes listed here (i.e., high biomass in the past), these anecdotes are valuable as they explain lost biomass in a perspective meaningful to all. This perspective may be valuable for managers trying to consider the non‐financial value of a shared fishery but, if unrecognised, represents a shifting baseline.  相似文献   

Pediment response to drainage basin evolution in south-central Arizona     

Phillip H. Larson  Ronald I. Dorn  R. Evan Palmer  Zack Bowles  Emma Harrison  Scott Kelley 《自然地理学》2014,35(5):369-389

The Sonoran Desert portion of the Basin and Range physiographic province contains a number of streams that now flow across once-closed basins. We explore here the research questions of if and how granitic rock pediments respond to the transition from rimming endorheic basins to bordering through-flowing streams. Granitic rock pediments of the northern Usery and eastern McDowell Mountains once graded to the closed Miocene–Pliocene Pemberton basin that occupied the present-day location of the confluence of the Salt and Verde Rivers. The process of lake overflow, which integrated these rivers, first aggraded fill terraces that, in turn, caused aggradation of a mantle of transported grus on bedrock pediments. Subsequent episodic incision of the Salt and Verde rivers lowered the base level; this led to the development of erosional features such as rolling topography of a degrading pediment mantle; exposure of the former piedmont angle and its associated zones of enhanced bedrock decay and regolith carbonate; and exposure of spheroidally weathered bedrock and emerging tors, some of which experienced 20^th century erosion. The granitic pediments of the former Pemberton Basin, which now transport grus to the Salt and Verde rivers, have actively adjusted to aggradational and degradational events associated with drainage integration and do not appear to be inherited from an ancient wet climatic interval.  相似文献   

Comparing seven candidate mission configurations for temporal gravity field retrieval through full-scale numerical simulation   总被引：3，自引：2，他引：1  

Basem Elsaka  Jean-Claude Raimondo  Phillip Brieden  Tilo Reubelt  Jürgen Kusche  Frank Flechtner  Siavash Iran Pour  Nico Sneeuw  Jürgen Müller 《Journal of Geodesy》2014,88(1):31-43

The goal of this contribution is to focus on improving the quality of gravity field models in the form of spherical harmonic representation via alternative configuration scenarios applied in future gravimetric satellite missions. We performed full-scale simulations of various mission scenarios within the frame work of the German joint research project “Concepts for future gravity field satellite missions” as part of the Geotechnologies Program, funded by the German Federal Ministry of Education and Research and the German Research Foundation. In contrast to most previous simulation studies including our own previous work, we extended the simulated time span from one to three consecutive months to improve the robustness of the assessed performance. New is that we performed simulations for seven dedicated satellite configurations in addition to the GRACE scenario, serving as a reference baseline. These scenarios include a “GRACE Follow-on” mission (with some modifications to the currently implemented GRACE-FO mission), and an in-line “Bender” mission, in addition to five mission scenarios that include additional cross-track and radial information. Our results clearly confirm the benefit of radial and cross-track measurement information compared to the GRACE along-track observable: the gravity fields recovered from the related alternative mission scenarios are superior in terms of error level and error isotropy. In fact, one of our main findings is that although the noise levels achievable with the particular configurations do vary between the simulated months, their order of performance remains the same. Our findings show also that the advanced pendulums provide the best performance of the investigated single formations, however an accuracy reduced by about 2–4 times in the important long-wavelength part of the spectrum (for spherical harmonic degrees ${<}50$ ), compared to the Bender mission, can be observed. Concerning state-of-the-art mission constraints, in particular the severe restriction of heterodyne lasers on maximum range-rates, only the moderate Pendulum and the Bender-mission are beneficial options, of course in addition to GRACE and GRACE-FO. Furthermore, a Bender-type constellation would result in the most accurate gravity field solution by a factor of about 12 at long wavelengths (up to degree/order 40) and by a factor of about 200 at short wavelengths (up to degree/order 120) compared to the present GRACE solution. Finally, we suggest the Pendulum and the Bender missions as candidate mission configurations depending on the available budget and technological progress.  相似文献   

Plants on stand by: the textiles and clothing industry in non‐metropolitan areas of New South Wales and Victoria     

Phillip M. O'Neill 《The Australian geographer》1991,22(2):108-112

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The effect of terrace geology on ground‐water movement and on the interaction of ground water and surface water on a mountainside near Mirror Lake,New Hampshire,USA     

Thomas C. Winter  Donald C. Buso  Patricia C. Shattuck  Phillip T. Harte  Donald A. Vroblesky  Daniel J. Goode 《水文研究》2008,22(1):21-32

The west watershed of Mirror Lake in the White Mountains of New Hampshire contains several terraces that are at different altitudes and have different geologic compositions. The lowest terrace (FSE) has 5 m of sand overlying 9 m of till. The two next successively higher terraces (FS2 and FS1) consist entirely of sand and have maximum thicknesses of about 7 m. A fourth, and highest, terrace (FS3) lies in the north‐west watershed directly adjacent to the west watershed. This highest terrace has 2 m of sand overlying 8 m of till. All terraces overlie fractured crystalline bedrock. Numerical models of hypothetical settings simulating ground‐water flow in a mountainside indicated that the presence of a terrace can cause local ground‐water flow cells to develop, and that the flow patterns differ based on the geologic composition of the terrace. For example, more ground water moves from the bedrock to the glacial deposits beneath terraces consisting completely of sand than beneath terraces that have sand underlain by till. Field data from Mirror Lake watersheds corroborate the numerical experiments. The geology of the terraces also affects how the stream draining the west watershed interacts with ground water. The stream turns part way down the mountainside and passes between the two sand terraces, essentially transecting the movement of ground water down the valley side. Transects of water‐table wells were installed across the stream's riparian zone above, between, and below the sand terraces. Head data from these wells indicated that the stream gains ground water on both sides above and below the sand terraces. However, where it flows between the sand terraces the stream gains ground water on its uphill side and loses water on its downhill side. Biogeochemical processes in the riparian zone of the flow‐through reach have resulted in anoxic ground water beneath the lower sand terrace. Results of this study indicate that it is useful to understand patterns of ground‐water flow in order to fully understand the flow and chemical characteristics of both ground water and surface water in mountainous terrain. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

ATLAS OF THE SOUTH PACIFIC     

Phillip L. Barton 《New Zealand geographer》1980,36(2):94-95

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Estimating nutrient budgets in tropical estuaries subject to episodic flows     

Webster IT  Ford PW  Tillman P 《Marine pollution bulletin》2005,51(1-4):165-173

Most Australian estuaries are subject to riverine discharge regimes that are highly episodic. This characteristic poses difficulties for estimating nutrient budgets of such systems based on sampling regimes that do not resolve the discharge variation and the changes in nutrient distributions that they cause. This paper presents a method for calculating nutrient budgets in estuaries having episodic hydrology. The method utilises a simple hydrodynamic transport model that is calibrated using measured salinities and which is used to describe the transport properties of the estuary as they respond to river discharge. Using this transport model, the temporal variation in nutrient concentrations within the estuary can be resolved between sampling surveys even when the discharge events are of short duration. An inverse method is then applied to calculate internal fluxes of nutrients from measurements obtained on successive sampling surveys. The approach is demonstrated through an application to the Fitzroy Estuary in Queensland, Australia.  相似文献   

A review of pollutants in the sea-surface microlayer (SML): a unique habitat for marine organisms     

Wurl O  Obbard JP 《Marine pollution bulletin》2004,48(11-12):1016-1030

Boundary layers between different environmental compartments represent critical interfaces for biological, chemical and physical processes. The sea-surface microlayer (uppermost 1-1000 microm layer) forms the boundary layer interface between the atmosphere and ocean. Environmental processes are controlled by the SML, and it is known to play a key role in the global distribution of anthropogenic pollutants. Due to its unique chemical composition, the upper organic film of the SML represents both a sink and a source for a range of pollutants including chlorinated hydrocarbons, organotin compounds, petroleum hydrocarbons, polycyclic aromatic hydrocarbons (PAH) and heavy metals. These pollutants can be enriched in the SML by up to 500 times relative to concentrations occurring in the underlying bulk water column. The SML is also a unique ecosystem, serving as an important habitat for fish eggs and larvae. Concentration ranges and enrichment factors of pollutants in the SML in different areas of the world's oceans have been critically reviewed, together with available toxicity data for marine biota found within the SML. Overall, the SML is highly contaminated in many urban and industrialized areas of the world, resulting in severe ecotoxicological impacts. Such impacts may lead to drastic effects on the marine food web and to fishery recruitment in coastal waters. Studies of the toxicity of fish eggs and larvae exposed to the SML contaminants have shown that the SML in polluted areas leads to significantly higher rates of mortality and abnormality of fish embryos and larvae.  相似文献   

The effect of horizontal resolution on simulation of very extreme US precipitation events in a global atmosphere model   总被引：1，自引：0，他引：1  

Michael F. Wehner  Richard L. Smith  G. Bala  Phillip Duffy 《Climate Dynamics》2010,34(2-3):241-247

We investigate the ability of a global atmospheric general circulation model (AGCM) to reproduce observed 20 year return values of the annual maximum daily precipitation totals over the continental United States as a function of horizontal resolution. We find that at the high resolutions enabled by contemporary supercomputers, the AGCM can produce values of comparable magnitude to high quality observations. However, at the resolutions typical of the coupled general circulation models used in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, the precipitation return values are severely underestimated.  相似文献   

Scaling of tropical rainfall as observed by TRMM precipitation radar     

Mekonnen Gebremichael  Witold F. Krajewski  Thomas M. Over  Yukari N. Takayabu  Phillip Arkin  M. Katayama 《Atmospheric Research》2008,88(3-4):337-354

We used a three-year (1998–2000) dataset of TRMM Precipitation Radar observations to investigate the scaling properties of spatial rainfall fields. This dataset allows consideration of spatial scales ranging from about 4.3 km to 138 km and short temporal scales corresponding to the sensor overpasses. The focus is on the marginal spatial moment scaling, which allows estimation of the scaling parameters from a single scene of data. Here we present a global perspective of the scaling properties of tropical rainfall in terms of its spatial variability, atmospheric forcing, predictability, and applicability. Our results reveal the following: 1) the scaling parameters exhibit strong variability associated with land/ocean contrast and mean precipitation at the synoptic scale; 2) there exists a one-to-one relationship between the scaling parameters and the large-scale spatial average rain rate of a universal functional form; 3) the majority of the scenes are consistent with the hypothesis of scale invariance at the moment orders of 0 and 2; 4) relatively there are more scale-invariant rain scenes over land than over ocean; and 5) for the scenes that are non-scale-invariant, deviation from scale-invariance mainly arises from the increasingly intermittent behavior of rainfall as spatial scale decreases. These results have important implications for the development and calibration of downscaling procedures designed to reproduce rainfall properties at different spatial scales and lead to a better understanding of the nature of tropical rainfall at various spatial resolutions.  相似文献