Improved estimation of f-ratio in natural phytoplankton assemblages     

《Deep Sea Research Part I: Oceanographic Research Papers》1999,46(10):1793-1808

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South Atlantic and benthic foraminifer δ13C deviations: implications for reconstructing the Late Quaternary deep-water circulation     

《Deep Sea Research Part II: Topical Studies in Oceanography》1999,46(1-2):437-452

Benthic foraminifer species Cibicidoides wuellerstorfi and related genera are assumed to secrete calcite very close to the carbon isotope values of the ambient bottom-water ΣCO₂. Recently, attention has been focused on substantial productivity-linked δ¹³C depletions. To examine further the productivity effect on benthic δ¹³C deviations, we present data from the South Atlantic between 15 and 35°S, including water samples from 10 hydrographic stations and related surface-sediment measurements on C. wuellerstorfi. We compare open-ocean data with observations in the Namibia Upwelling area. As a result, δ¹³C_ΣCO2 values as well as phosphate concentrations in water samples of the upwelling realm differ significantly from those of the open-ocean realm at least in the upper and mid-depth water masses (SACW, AAIW, UCDW). However, deviations from the Redfield fractionation, caused by air–sea fractionation, remain constant within each water mass, which means that the carbon isotope changes toward upwelling areas are exclusively determined by biological cycling. In addition to lower δ¹³C_ΣCO2 values in upwelling areas, a depletion in the δ¹³C of epibenthic foraminifer calcite is observed, which is most likely explained by the decay of organic matter, reducing the ¹³C/¹²C ratio in the pore water and influencing the carbon isotopic composition of the C. wuellerstorfi shells of highly productive areas. The paleoceanographic implication of this effect for reconstructing the Late Quaternary deep-water circulation is discussed using carbon isotope records of several sediment cores within and outside the Namibia upwelling area.  相似文献   

Advancements and best practices for analysis and correlation of tephra and cryptotephra in ice     

《Quaternary Geochronology》2017

Geochemical analysis of fine grained (<20 μm) tephra found in ice cores is inherently difficult, due to the typically low number and small size of available particles. Ice core tephra samples require specialized sample preparation techniques to maximize the amount of information that can be gained from these logistically limited samples that may provide important chronology to an ice record, as well as linking glacial, marine and terrestrial sediments. We have developed a flexible workflow for preparation of tephra and cryptotephra samples to allow accurate and robust geochemical fingerprinting, which is fundamental to tephrochronology. The samples can be prepared so that secondary electron imagery can be obtained for morphological characterization of the samples to ensure that the sample is tephra-bearing and then the sample can be further prepared for quantitative electron microprobe analysis using wavelength dispersive techniques (EMP-WDS), scanning electron microscopy with energy dispersive spectrometry (SEM-EDS), laser ablation inductively coupled mass spectrometry (LA-ICP-MS) or secondary ion mass spectrometry (SIMS). Some samples may be too small for typical instrumentation conditions to be used (i.e. 20 μm beam on the EMP) to analyze for geochemistry and we present other techniques that can be employed to obtain accurate, although less precise, geochemistry. Methods include analyzing unpolished tephra shards less than 5 μm in diameter with a 1 μm beam on an SEM; using the “broad beam overlap” EMP method on irregular particles less than 20 μm in diameter, and analyzing microlitic shards as well as aphyric shards using EMP to increase the number of analyzed shards in low abundance tephra layers. The methods presented are flexible enough to be employed in other geological environments (terrestrial, marine and glacial) which will help maximize and integrate multiple environments into the overall tephra framework.  相似文献   

Highly nonlinear wind waves in Currituck Sound: dense breather turbulence in random ocean waves     

Osborne  Alfred R.  Resio  Donald T.  Costa  Andrea  Ponce de León  Sonia  Chirivì  Elisabetta 《Ocean Dynamics》2019,69(2):187-219

Ocean Dynamics - We analyze surface wave data taken in Currituck Sound, North Carolina, during a storm on 4 February 2002. Our focus is on the application of nonlinear Fourier analysis (NLFA)...  相似文献   

The Adaptive Marine Policy (AMP) toolbox: Supporting policy-makers developing adaptive policies in the Mediterranean and Black Sea     

《Marine Policy》2017

Adaptive management is essential to the practical application of the Ecosystem-Based Approach (EBA). Despite there are frequent assertions that adaptive management is being used, evidence on its success is still limited. Indeed, it is difficult to bring the different elements of adaptive management together in a robust way and to choose the appropriate tools to do it. Therefore, it is necessary to provide a practical framework for adaptive policy action, consistent with the EBA. Accordingly, to operationalize the design and implementation of adaptive policies on the basis of the EBA, the Adaptive Marine Policy toolbox has been developed. The objective of the toolbox is to provide policy-makers a practical framework to design and implement adaptive policies. To show the functionality of the toolbox, the guidelines and resources provided within the toolbox have been applied to the marine litter issue in the Mediterranean and Black Sea as an example. The example application has shown that the toolbox is a useful and operational framework to build a science-policy interface according to the EBA. Despite some resources could be missing from the toolbox, they provide a practical and useful starting point to support the application of the different steps and key activities.  相似文献   

Management priorities for seawater desalination plants in a marine protected area: A multi-criteria analysis     

《Marine Policy》2017

The development of seawater desalination plants to increase water reliability in coastal areas poses a threat to the health of near shore marine ecosystems and may affect the effectiveness of marine protected areas (MPAs) that have been established to meet international conservation targets. This paper applies a multi-criteria analysis approach to quantify stakeholder groups’ priorities for seawater desalination plants that have been proposed in communities adjacent to a National Marine Sanctuary. All groups placed the highest importance on minimizing environmental impacts on protected areas and endangered species that could be affected by water intake and brine discharge emphasizing the need for integrated land and sea conservation. Minimizing socio-economic impacts on coastal communities was much less important. Stakeholders also weighted reducing pressure on water levels in rivers, streams, and aquifers as more important than increasing water for residential consumption, which may foster coastal growth rather than replacing water taken from other sources. The study further revealed differences in the importance of multiple management objectives among stakeholder groups, which highlights the need to elicit distinct priorities of all groups to understand concerns and potential conflicts of desalination with existing marine users. The analysis of consistency ratios revealed that around half of all surveyed stakeholders had high inconsistencies in their responses, which suggests either a lack of understanding of desalination, or reflects the complexity of establishing desalination plants in coastal areas adjacent to a marine protected area.  相似文献   

GGR Biennial Critical Review: Analytical Developments Since 2014          下载免费PDF全文

Kathryn L. Linge  L. Paul Bédard  Roxana Bugoi  Jacinta Enzweiler  Klaus Peter Jochum  Rüdiger Kilian  Jingao Liu  Johanna Marin‐Carbonne  Silke Merchel  Frans Munnik  Luiz F.G. Morales  Claire Rollion‐Bard  A. Kate Souders  Paul J. Sylvester  Ulrike Weis 《Geostandards and Geoanalytical Research》2017,41(4):493-562

This GGR biennial critical review covers developments and innovations in key analytical methods published since January 2014, relevant to the chemical, isotopic and crystallographic characterisation of geological and environmental materials. In nine selected analytical fields, publications considered to be of wide significance are summarised, background information is provided and their importance evaluated. In addition to instrumental technologies, this review also presents a summary of new developments in the preparation and characterisation of rock, microanalytical and isotopic reference materials, including a précis of recent changes and revisions to ISO guidelines for reference material characterisation and reporting. Selected reports are provided of isotope ratio determinations by both solution nebulisation MC‐ICP‐MS and laser ablation‐ICP‐MS, as well as of radioactive isotope geochronology by LA‐ICP‐MS. Most of the analytical techniques elaborated continue to provide new applications for geochemical analysis; however, it is noted that instrumental neutron activation analysis has become less popular in recent years, mostly due to the reduced availability of nuclear reactors to act as a neutron source. Many of the newer applications reported here provide analysis at increasingly finer resolution. Examples include atom probe tomography, a very sensitive method providing atomic scale information, nanoscale SIMS, for isotopic imaging of geological and biological samples, and micro‐XRF, which has a spatial resolution many orders of magnitude smaller than conventional XRF.  相似文献   

Field spectroscopy and radiative transfer modelling to assess impacts of petroleum pollution on biophysical and biochemical parameters of the Amazon rainforest     

Paul Arellano  Kevin Tansey  Heiko Balzter  Doreen S. Boyd 《Environmental Earth Sciences》2017,76(5):217

Biophysical and biochemical plant foliage parameters play a key role in assessing vegetation health. Those plant parameters determine the spectral reflectance and transmittance properties of vegetation; therefore, hyperspectral remote sensing, particularly imaging spectroscopy, can provide estimates of leaf and canopy chemical properties. Based on the relationship between spectral response and biochemical/biophysical properties of the leaves and canopies, the PROSPECT radiative transfer model simulates the interaction of light with leaves. In this study, more than 1100 leaf samples from the Amazon forest of Ecuador were collected at several study sites, some of which are affected by petroleum pollution, and across the vertical profile of the forest. For every sample, field spectroscopy at leaf level was conducted with a spectroradiometer. The goal of this study was to assess leaf optical properties of polluted and unpolluted rainforest canopies across the vertical profile and identify vegetation stress expressed in changes of biophysical and biochemical properties of vegetation. An ANOVA followed by Holme’s multiple comparisons of means and a principal component analysis showed that photosynthetic pigments, chlorophyll and carotenoids have significantly lower levels across the vertical profile of the forest, particularly in sites affected by petroleum pollution. On the other hand, foliar water content showed significantly higher levels in the polluted site. Those findings are symptoms of vegetation stress caused by reduced photosynthetic activity and consequently decreased transpiration and water-use efficiency of the plants. Cross-comparison between SPAD-502 chlorophyll content meter index and chlorophyll content showed strong positive correlation coefficients (r = 0.71 and r ² = 0.51) which suggests that using the SPAD-502 chlorophyll index itself is sensitive enough to detect vegetation stress in a multispecies tropical forest. Therefore, the SPAD-502 can be used to assess chlorophyll content of vegetation across polluted and non-polluted sites at different canopy layers. The results presented in this paper contribute to the very limited literature on field spectroscopy and radiative transfer models applied to the vertical profile of the Amazon forest.  相似文献   

Using meteorological observer data to compare wind erosion during two great droughts in eastern Australia; the World War II Drought (1937–1946) and the Millennium Drought (2001–2010)          下载免费PDF全文

Tadhg O'Loingsigh  Grant H. McTainsh  Katherine Parsons  Craig L. Strong  Phil Shinkfield  Nigel J. Tapper 《地球表面变化过程与地形》2015,40(1):123-130

Australian meteorological observers started using the World Meteorological Organization (WMO) weather coding system in the 1950s. This system is still in use around the world today. However, observing and recording the weather in an organized and systematic manner had been ongoing for over 100 years prior to the adoption of this coding system, and much like Australia, most countries will have historical meteorological records. In this paper we compare the wind erosion of two of the greatest droughts in Australian recorded history; the World War II (WWII) Drought (1937–1945) and the Millennium Drought (2001–2009). To do this we analysed previously unavailable meteorological observer records from the Australian Bureau of Meteorology (ABM). Wind erosion records, mostly in long‐hand written form, were translated to the modern WMO coding system for the WWII Drought and compared with the wind erosion of Australia's recently‐ended Millennium Drought, one of the longest and harshest on record. We quantify wind erosion using Dust Event Days (DED) and a modified version of a published Dust Storm Index (DSI) to show that wind erosion during the WWII Drought was up to 4.6 times higher than during the Millennium Drought. This study has international significance because it demonstrates a methodology for tracking changes in wind erosion over the past 75 years based on observer records available in every country with a history of organized weather observation. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Dynamical downscaling approach for wintertime seasonal-scale simulation over the Western Himalayas     

Pushp R. Tiwari  Sarat C. Kar  Uma C. Mohanty  Sagnik Dey  Palash Sinha  P. V. S. Raju  M. S. Shekhar 《Acta Geophysica》2014,62(4):930-952

The performance of RegCM4 for seasonal-scale simulation of winter circulation and associated precipitation over the Western Himalayas (WH) is examined. The model simulates the circulation features and precipitation in three distinct precipitation years reasonably well. It is found that the RMSE decreases and correlation coefficient increases in the precipitation simulations with the increase of model horizontal resolutions. The ETS and POD for the simulated precipitation also indicate that the performance of model is better at 30 km resolution than at 60 and 90 km resolutions. This improvement comes due to better representation of orography in the high-resolution model in which sharp orography gradient in the domain plays an important role in wintertime precipitation processes. A comparison of model-simulated precipitation with observed precipitation at 17 station locations has been carried out. Overall, the results suggest that 30 km model produced better skill in simulating the precipitation over the WH and this model is a useful tool for further regional downscaling studies.  相似文献