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961.
O'Leary BC Smart JC Neale FC Hawkins JP Newman S Milman AC Roberts CM 《Marine pollution bulletin》2011,62(12):2642-2648
We analysed the extent to which European politicians have adhered to scientific recommendations on annual total allowable catches (TACs) from 1987 to 2011, covering most of the period of the Common Fisheries Policy (CFP). For the 11 stocks examined, TACs were set higher than scientific recommendations in 68% of decisions. Politically-adjusted TACs averaged 33% above scientifically recommended levels. There was no evidence that the 2002 reform of the CFP improved decision-making, as was claimed at the time. We modelled the effects of such politically-driven decision-making on stock sustainability. Our results suggest that political adjustment of scientific recommendations dramatically increases the probability of a stock collapsing within 40 years.In 2012 European fisheries policy will undergo a once-a-decade reform. Ten years ago radical reforms were promised but the changes failed to improve sustainability. It is likely that the 2012 reform will be similarly ineffective unless decision-making is changed so that catch allocations are based on science rather than politics. 相似文献
962.
Andrew Moore James Goff Brian G. McAdoo Hermann M. Fritz Aditya Gusman Nikos Kalligeris Kenia Kalsum Arif Susanto Debora Suteja Costas E. Synolakis 《Pure and Applied Geophysics》2011,168(11):1951-1961
The 2006 western Java tsunami deposited a discontinuous sheet of sand up to 20 cm thick, flooded coastal southern Java to
a depth of at least 8 m and inundated up to 1 km inland. In most places the primarily heavy mineral sand sheet is normally
graded, and in some it contains complex internal stratigraphy. Structures within the sand sheet probably record the passage
of up to two individual waves, a point noted in eyewitness accounts. We studied the 2006 tsunami deposits in detail along
a flow parallel transect about 750 m long, 15 km east of Cilacap. The tsunami deposit first becomes discernable from the underlying
sediment 70 m from the shoreline. From 75 to 300 m inland the deposit has been laid down in rice paddies, and maintains a
thickness of 10–20 cm. Landward of 300 m the deposit thins dramatically, reaching 1 mm by 450 m inland. From 450 m to the
edge of deposition (around 700 m inland) the deposit remains <1 mm thick. Deposition generally attended inundation—along the
transect, the tsunami deposited sand to within about 40 m of the inundation limit. The thicker part of the deposit contains
primarily sand indistinguishable from that found on the beach 3 weeks after the event, but after about 450 m (and roughly
coinciding with the decrease in thickness) the tsunami sediment shifts to become more like the underlying paddy soil than
the beach sand. Grain sizes within the deposit tend to fine upward and landward, although overall upward fining takes place
in two discrete pulses, with an initial section of inverse grading followed by a section of normal grading. The two inversely
graded sections are also density graded, with denser grains at the base, and less dense grains at the top. The two normally
graded sections show no trends in density. The inversely graded sections show high density sediment to the base and become
less dense upward and represents traction carpet flows at the base of the tsunami. These are suggestive of high shear rates
in the flow. Because of the grain sorting in the traction carpet, the landward-fining trends usually seen in tsunami deposits
are masked, although lateral changes of mean sediment grain size along the transect do show overall landward fining, with
more variation as the deposit tapers off. The deposit is also thicker in the more seaward portions than would be produced
by tsunamis lacking traction carpets. 相似文献
963.
A management proposal aims to partly remove a WWII military causeway at Palmyra Atoll to improve lagoon water circulation and alleviate sedimentation stress on the southeast backreef, an area of high coral cover and diversity. This action could result in a shift in sedimentation across reef sites. To provide management advice, we quantified the proximate environmental factors driving scleractinian coral cover and community patterns at Palmyra. The proportion of fine sedimentation was the optimal predictor of coral cover and changes in community structure, explaining 23.7% and 24.7% of the variation between sites, respectively. Scleractinian coral cover was negatively correlated with increases in fine sedimentation. Removing the causeway could negatively affect the Montipora corals that dominate the western reef terrace, as this genus was negatively correlated with levels of fine sedimentation. The tolerance limits of corals, and sediment re-distribution patterns, should be determined prior to complete removal of the causeway. 相似文献
964.
965.
Conduits serve as major pathways for groundwater flow in karst aquifers. Locating them from the surface, however, is one of the most challenging tasks in karst research. Geophysical methods are often deployed to help locate voids by mapping variations of physical properties of the subsurface. Conduits can cause significant contrasts of some physical properties that can be detected; other subsurface features such as water-bearing fractures often yield similar contrasts, which are difficult to distinguish from the effects of the conduits. This study used electrical resistivity method to search for an unmapped karst conduit that recharges Royal Spring in the Inner Bluegrass karst region, Kentucky, USA. Three types of resistivity techniques (surface 2D survey, quasi-3D survey, and time-lapse survey) were used to map and characterize resistivity anomalies. Some of the major anomalies were selected as drilling targets to verify the existence of the conduits. Drilling near an anomaly identified by an electrical resistivity profile resulted in successful penetration of a major water-filled conduit. The drilling results also suggest that, in this study area, low resistivity anomalies in general are associated with water-bearing features. However, differences in the anomaly signals between the water-filled conduit and other water-bearing features such as water-filled fracture zones were undistinguishable. The electrical resistivity method is useful in conduit detection by providing potential drilling targets. Knowledge of geology and hydrogeology about the site and professional judgment also played important roles in locating the major conduit. 相似文献
966.
June K. Yeung James A. SmithGabriele Villarini Alexandros A. NtelekosMary Lynn Baeck Witold F. Krajewski 《Advances in water resources》2011,34(2):184-204
We examine the warm season (April-September) rainfall climatology of the northeastern US through analyses of high-resolution radar rainfall fields from the Hydro-NEXRAD system and regional climate model simulations using the weather research and forecasting (WRF) model. Analyses center on the 5-year period from 2003 to 2007 and the study area includes the New York-New Jersey metropolitan region covered by radar rainfall fields from the Fort Dix, NJ WSR-88D. The objective of this study is to develop and test tools for examining rainfall climatology, with a special focus on heavy rainfall. An additional emphasis is on rainfall climatology in regions of complex terrain, like the northeastern US, which is characterized by land-water boundaries, large heterogeneity in land use and cover, and mountainous terrain in the western portion of the region. We develop a 5-year record of warm season radar rainfall fields for the study region using the Hydro-NEXRAD system. We perform regional downscaling simulations for the 5-year study period using the WRF model. Radar rainfall fields are used to characterize the interannual, seasonal and diurnal variation of rainfall over the study region and to examine spatial heterogeneity of rainfall. Regional climate model simulations are characterized by a wet bias in the rainfall fields, with the largest bias in the high-elevation regions of the model domain. We show that model simulations capture broad features of the interannual, seasonal, and diurnal variation of rainfall. Model simulations do not capture spatial gradients in radar rainfall fields around the New York metropolitan region and land-water boundaries to the east. The model climatology of convective available potential energy (CAPE) is used to interpret the regional distribution of warm season rainfall and the seasonal and diurnal variability of rainfall. We use hydrologic and meteorological observations from July 2007 to examine the interactions of land surface processes and rainfall from a regional perspective. 相似文献
967.
There are currently no industry‐wide standards for the calibration and specification of water‐level monitoring pressure transducers. Consequently, specifications from different manufacturers are currently not directly comparable, and different branded sensors may not perform similarly under the same environmental conditions. This has been highlighted by the varied performance of 14 leading brands of pressure transducers under test conditions. In laboratory tests, transducers generally met product accuracy specifications, although temperature compensation was substandard in five absolute sensors. In a 99‐day field test, accuracy was typically within around ±10 mm for lower range pressure sensors, which exceeded some product specifications. Furthermore, there was evidence for linear and curved forms of instrument drift. As a result of the diverse performance of the transducers, it is recommended that an industry‐wide standard for calibration and specification is introduced. This would eliminate any uncertainty surrounding the current procedures and lead to more informed procurement by the user who would have a greater understanding of comparative instrument performance. Any new standard should also address sensor drift which is currently rarely cited in product specifications. 相似文献
968.
Between a.d. 2006 and 2008, we completed annual surveys of two mercury‐contaminated eroding banks, one forested and the other grass covered, along the gravel‐bed, bedrock South River in Virginia. Gridded digital terrain models with a resolution of 0·05 m were created from bank topography data collected using a terrestrial laser scanner. Model comparisons indicate that the forested bank retreated nearly 1 m around two leaning trees, while elsewhere the extent of bank retreat was negligible. On the grassy bank, retreat was controlled by the creation of small overhanging clumps of turf at the top of the bank, their occasional failure, and the ultimate removal of failed debris from the bank toe. Partial autocorrelation analysis of vertically integrated bank retreat demonstrates that bank profile erosion is virtually uncorrelated at horizontal distances greater than about 1 m on both banks, a length scale of approximately half the bank height. This extensive streamwise variability suggests that widely spaced profile data cannot adequately represent bank erosion at these sites. Additional analysis of our comprehensive spatial data also indicates that traditional bank profile surveys with any spacing greater than 1 m would result in measurement errors exceeding 10%, an important conclusion for assessing annual rates of mercury loading into the South River from bank erosion. Our results suggest that three‐dimensional gridded bare‐earth models of bank topography may be required to accurately measure annual bank retreat in similar river systems. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
969.
Jörg Geldmacher Kaj Hoernle Barry B. Hanan Janne Blichert-Toft F. Hauff James B. Gill Hans-Ulrich Schmincke 《Contributions to Mineralogy and Petrology》2011,162(1):21-36
The broad belt of intraplate volcanism in the East Atlantic between 25° and 37° N is proposed to have formed by two adjacent
hotspot tracks (the Madeira and Canary tracks) that possess systematically different isotopic signatures reflecting different
mantle source compositions. To test this model, Hf isotope ratios from volcanic rocks from all individual islands and all
major seamounts are presented in this study. In comparison with published Nd isotope variations (6 εNd units), 176Hf/177Hf ratios span a much larger range (14 εHf units). Samples from the proposed Madeira hotspot track have the most radiogenic
Hf isotopic compositions (176Hf/177Hfm up to 0.283335), extending across the entire field for central Atlantic MORB. They form a relatively narrow, elongated trend
on the Nd vs. Hf isotope diagram (stretching over > 10 εHf units) between a depleted N-MORB-like endmember and a moderately
enriched composition located on, or slightly below, the Nd–Hf mantle array, which overlaps the proposed “C” mantle component
of Hanan and Graham (1996). In contrast, all samples from the Canary hotspot track plot below the mantle array (176Hf/177Hfm = 0.282943–0.283067) and form a much denser cluster with less compositional variation (~4 εHf units). The cluster falls between
(1) a low Hf isotope HIMU-like endmember, (2) a more depleted composition, and (3) the moderately enriched end of the Madeira
trend. The new Hf isotope data confirm the general geochemical distinction of the Canary and Madeira domains in the East Atlantic.
Both domains, however, seem to share a common, moderately enriched endmember that has “C”-like isotope compositions and is
believed to represent subducted, <1-Ga-old oceanic lithosphere (oceanic crust and possibly minor sediment addition). The lower
176Hf/177Hf ratio of the enriched, HIMU-like Canary domain endmember indicates the contribution of oceanic lithosphere with somewhat
older recycling ages of ≥1 Ga. 相似文献
970.
Heleen Vanneste Boris A. Kelly-Gerreyn Rachael H. James Rebecca E. Fisher Rachel A. Mills 《Geochimica et cosmochimica acta》2011,75(4):1124-1144
Submarine mud volcanism is an important pathway for transfer of deep-sourced fluids enriched in hydrocarbons and other elements into the ocean. Numerous mud volcanoes (MVs) have been discovered along oceanic plate margins, and integrated elemental fluxes are potentially significant for oceanic chemical budgets. Here, we present the first detailed study of the spatial variation in fluid and chemical fluxes at the Carlos Ribeiro MV in the Gulf of Cadiz. To this end, we combine analyses of the chemical composition of pore fluids with a 1-D transport-reaction model to quantify fluid fluxes, and fluxes of boron, lithium and methane, across the sediment-seawater interface. The pore fluids are significantly depleted in chloride, but enriched in lithium, boron and hydrocarbons, relative to seawater. Pore water profiles of sulphate, hydrogen sulphide and total alkalinity indicate that anaerobic oxidation of methane occurs at 34-180 cm depth below seafloor. Clay mineral dehydration, and in particular the transformation of smectite to illite, produces pore fluids that are depleted in chloride and potassium. Profiles of boron, lithium and potassium are closely related, which suggests that lithium and boron are released from the sediments during this transformation. Pore fluids are expelled into the water column by advection; fluid flow velocities are 4 cm yr−1 at the apex of the MV but they rapidly decrease to 0.4 cm yr−1 at the periphery. The associated fluxes of boron, lithium and methane vary between 7-301, 0.5-6 and 0-806 mmol m−2 yr−1, respectively. We demonstrate that fluxes of Li and B due to mud volcanism may be important on a global scale, however, release of methane into the overlying water column is suppressed by microbial methanotrophy. 相似文献