Can ocean iron fertilization mitigate ocean acidification?     

Long Cao  Ken Caldeira 《Climatic change》2010,99(1-2):303-311

Ocean iron fertilization has been proposed as a method to mitigate anthropogenic climate change, and there is continued commercial interest in using iron fertilization to generate carbon credits. It has been further speculated that ocean iron fertilization could help mitigate ocean acidification. Here, using a global ocean carbon cycle model, we performed idealized ocean iron fertilization simulations to place an upper bound on the effect of iron fertilization on atmospheric CO₂ and ocean acidification. Under the IPCC A2 CO₂ emission scenario, at year 2100 the model simulates an atmospheric CO₂ concentration of 965 ppm with the mean surface ocean pH 0.44 units less than its pre-industrial value of 8.18. A globally sustained ocean iron fertilization could not diminish CO₂ concentrations below 833 ppm or reduce the mean surface ocean pH change to less than 0.38 units. This maximum of 0.06 unit mitigation in surface pH change by the end of this century is achieved at the cost of storing more anthropogenic CO₂ in the ocean interior, furthering acidifying the deep-ocean. If the amount of net carbon storage in the deep ocean by iron fertilization produces an equivalent amount of emission credits, ocean iron fertilization further acidifies the deep ocean without conferring any chemical benefit to the surface ocean.  相似文献   

Modelling Near-Surface Low Winds over Land under Stable Conditions: Sensitivity Tests,Flux-Gradient Relationships,and Stability Parameters   总被引：1，自引：1，他引：0  

Ashok K. Luhar  Peter J. Hurley  Ken N. Rayner 《Boundary-Layer Meteorology》2009,130(2):249-274

Low or weak wind-speed conditions, roughly defined as the periods when the mean wind speed at 10 m above the ground is 2 ms⁻¹ or less, are of considerable practical interest. However, they are not readily amenable to treatment within prognostic meteorological models and, consequently, difficult to predict, especially when the ambient stability is strong. In this paper, we apply an E − ε prognostic meteorological model to simulate near-surface meteorology and, focusing on low wind speeds, compare the predictions with measurements from two independent datasets. A sensitivity analysis is performed to investigate the possible reasons for the relatively inferior model performance for low winds when the atmosphere is stably stratified. A comprehensive data analysis is carried out to study low wind stable conditions, concentrating on the validity of various forms of flux–gradient relationships for momentum and heat within the framework of the Monin-Obukhov similarity theory, which models employ for calculating surface fluxes. The observed behaviour of various stability parameters, such as the Richardson number, is investigated. The results point to inadequacies of the current flux–gradient relationships, especially regarding momentum, under strongly stable conditions as being a dominant reason for the poor low wind predictions. The modelling issues identified are not just restricted to the present model, but are general in nature. The use of an alternative stability function for momentum under strongly stable conditions is explored. It results in improved model performance for low winds; however, further research is needed to better understand strongly stable flows in the lower atmosphere and to develop methods that can translate that understanding to operational meteorological modelling.  相似文献   

The nature and fate of natural resins in the geosphere. XII. Investigation of C-ring aromatic diterpenoids in Raritan amber by pyrolysis-GC-matrix isolation FTIR-MS     

Anderson KB 《Geochemical transactions》2006,7(1):2-9

Upper Cretaceous amber from the Raritan Formation (Sayerville, New Jersey) has been investigated by Pyrolysis-GC-MS and Pyrolysis-GC-matrix isolation FTIR-MS. Results establish the existence of two distinct forms of amber in this deposit. Both forms are Class Ib ambers, but they are unambiguously differentiated on the basis of their (intact) diterpenoid composition. The presence of callitrisate in both forms, and cupraene in samples designated form 1, strongly suggest that both derive from related-but-distinct species within the Cupressaceae.  相似文献   

Continuous measurement of methane flux over a larch forest using a relaxed eddy accumulation method   总被引：1，自引：0，他引：1  

Masahito Ueyama  Ken Hamotani  Wataru Nishimura  Yoshiyuki Takahashi  Nobuko Saigusa  Reiko Ide 《Theoretical and Applied Climatology》2012,109(3-4):461-472

We measured the methane flux of a forest canopy throughout a year using a relaxed eddy accumulation (REA) method. This sampling system was carefully validated against heat and CO₂ fluxes measured by the eddy covariance method. Although the sampling system was robust, there were large uncertainties in the measured methane fluxes because of the limited precision of the methane gas analyzer. Based on the spectral characteristics of signals from the methane analyzer and the diurnal variations in the standard deviation of the vertical wind velocity, we found the daytime and nighttime precision of half-hourly methane flux measurements to be approximately 1.2 and 0.7?μg?CH₄?m^?2?s^?1, respectively. Additional uncertainties caused by the dilution effect were estimated to affect the accuracy by as much as 0.21?μg?CH₄?m^?2?s^?1 on a half-hourly basis. Diurnal and seasonal variations were observed in the measured fluxes. The biological emission from plant leaves was not observed in our studies, and thus could be negligible at the canopy-scale exchange. The annual methane sink was 835?±?175?mg?CH₄?m^?2?year^?1 (8.35?kg?CH₄?ha^?1?year^?1), which was comparable to the flux range of 379–2,478?mg?CH₄?m^?2?year^?1 previously measured in other Japanese forest soils. This study indicated that the REA method could be a promising technique to measure canopy scale methane fluxes over forests, but further improvement of precision of the analyzer will be required.  相似文献   

Mixed land use and obesity: an empirical comparison of alternative land use measures and geographic scales   总被引：1，自引：0，他引：1  

Yamada I  Brown BB  Smith KR  Zick CD  Kowaleski-Jones L  Fan JX 《The Professional geographer》2012,64(2):157-177

Obesity is a growing epidemic in the United States. Walkable neighborhoods, characterized as having the 3Ds of walkability (population Density, land use Diversity, and pedestrian-friendly Design), have been identified as a potentially promising factor to prevent obesity for their residents. Past studies examining the relationship between obesity and walkability vary in geographic scales of neighborhood definitions and methods of measuring the 3Ds. To better understand potential influences of these sometimes arbitrary choices, we test how four types of alternative measures of land use diversity measured at three geographic scales relate to body mass index for 4960 Salt Lake County adults. Generalized estimation equation models demonstrate that optimal diversity measures differed by gender and geographic scale and that integrating walkability measures at different scales improved the overall performance of models.  相似文献   

Assessing stand water use in four coastal wetland forests using sapflow techniques: annual estimates,errors and associated uncertainties          下载免费PDF全文

Ken W. Krauss  Jamie A. Duberstein  William H. Conner 《水文研究》2015,29(1):112-127

Forests comprise approximately 37% of the terrestrial land surface and influence global water cycling. However, very little attention has been directed towards understanding environmental impacts on stand water use (S) or in identifying rates of S from specific forested wetlands. Here, we use sapflow techniques to address two separate but linked objectives: (1) determine S in four, hydrologically distinctive South Carolina (USA) wetland forests from 2009–2010 and (2) describe potential error, uncertainty and stand‐level variation associated with these assessments. Sapflow measurements were made from a number of tree species for approximately 2–8 months over 2 years to initiate the model, which was applied to canopy trees (DBH > 10–20 cm). We determined that S in three healthy forested wetlands varied from 1.97–3.97 mm day^?1 or 355–687 mm year^?1 when scaled. In contrast, saltwater intrusion impacted individual tree physiology and size class distributions on a fourth site, which decreased S to 0.61–1.13 mm day^?1 or 110–196 mm year^?1. The primary sources of error in estimations using sapflow probes would relate to calibration of probes and standardization relative to no flow periods and accounting for accurate sapflow attenuation with radial depth into the sapwood by species and site. Such inherent variation in water use among wetland forest stands makes small differences in S (<200 mm year^?1) difficult to detect statistically through modelling, even though small differences may be important to local water cycling. These data also represent some of the first assessments of S from temperate, coastal forested wetlands along the Atlantic coast of the USA. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Incorporating climate change into water resources planning for the town of Polokwane,South Africa   总被引：2，自引：0，他引：2  

James Cullis  Ken Strzepek  Mark Tadross  Karim Sami  Beyers Havenga  Burgert Gildenhuys  Joel Smith 《Climatic change》2011,108(3):437-456

Incorporating climate change into water resource planning is crucial to ensuring sustainable growth and development. The aim of this study was to investigate how the proposed steps to incorporating climate change into project planning developed by USAID could be applied in practice using the town of Polokwane in northeastern South Africa as a case study. Two Regional Circulation Models (RCMs) and statistical downscaling from a range of General Circulation Models (GCMs) were used to produce a set of monthly climate scenarios for 2025 and 2050. These scenarios were used to estimate the impact on surface water runoff in the Olifants River catchment and the Letaba River catchment, and groundwater recharge in the Sand River Aquifer. The impact on the potential yields from the existing Flag Bashielo Dam and other proposed dams in the Olifants River catchment were determined using the Water Resources Yield Model (WRYM). The results of the analysis were discussed at a regional stakeholders workshop. The workshop participants concluded that the higher priority for now should be on water conservation and demand management (WCDM) and to consider a phased approach to developing additional storage capacity. The results of this study show that the six-stage process for incorporating climate change into resource planning can be applied in practice and that the potential threat of climate change can give emphasis to existing win–win approaches such as WCDM and phased implementation that should form part of any sustainable water resource planning approach.  相似文献   

Options for monitoring and estimating historical carbon emissions from forest degradation in the context of REDD+     

Herold M  Román-Cuesta RM  Mollicone D  Hirata Y  Van Laake P  Asner GP  Souza C  Skutsch M  Avitabile V  Macdicken K 《Carbon balance and management》2011,6(1):13

Measuring forest degradation and related forest carbon stock changes is more challenging than measuring deforestation since degradation implies changes in the structure of the forest and does not entail a change in land use, making it less easily detectable through remote sensing. Although we anticipate the use of the IPCC guidance under the United Framework Convention on Climate Change (UNFCCC), there is no one single method for monitoring forest degradation for the case of REDD+ policy. In this review paper we highlight that the choice depends upon a number of factors including the type of degradation, available historical data, capacities and resources, and the potentials and limitations of various measurement and monitoring approaches. Current degradation rates can be measured through field data (i.e. multi-date national forest inventories and permanent sample plot data, commercial forestry data sets, proxy data from domestic markets) and/or remote sensing data (i.e. direct mapping of canopy and forest structural changes or indirect mapping through modelling approaches), with the combination of techniques providing the best options. Developing countries frequently lack consistent historical field data for assessing past forest degradation, and so must rely more on remote sensing approaches mixed with current field assessments of carbon stock changes. Historical degradation estimates will have larger uncertainties as it will be difficult to determine their accuracy. However improving monitoring capacities for systematic forest degradation estimates today will help reduce uncertainties even for historical estimates.  相似文献   

新疆苏普特背斜花岗岩和变安山质凝灰岩LA-ICP-MS锆石U-Pb年代学特征及意义     

于淑艳  许英霞  郭正林  申茂德  杰肯  黄承科  郭旭吉 《西北地质》2011,44(2):15-24

阿尔泰南缘古生代康布铁堡组火山岩系是许多铁矿、铜锌矿以及铅锌矿的赋矿围岩,但该赋矿地层目前还缺乏精确的同位素年代学资料。通过对变安山质凝灰岩和花岗岩LA-ICP-MS锆石U-Pb定年,获得阿尔泰南缘苏普特背斜花岗岩的年龄为412.7±0.78 Ma,安山质凝灰岩的年龄为411.2±3.4 Ma,表明阿尔泰南缘苏普特背斜内泥盆纪早期存在着强烈的火山活动,与区内广泛发育的火山岩属于同一事件的产物,具有相同的动力学背景。为研究阿尔泰南缘古生代构造演化及苏普特背斜异常区提供了重要的理论依据。  相似文献   

Modeling the Effects of Future Outflow on the Abiotic Habitat of an Imperiled Estuarine Fish     

Frederick Feyrer  Ken Newman  Matthew Nobriga  Ted Sommer 《Estuaries and Coasts》2011,34(1):120-128

Future development and climate change pose potentially serious threats to estuarine fish populations around the world. We examined how habitat suitability for delta smelt (Hypomesus transpacificus), a state and federally protected species, might be affected by changes in outflow in the San Francisco Estuary due to future development and climate change. Forty years of sampling data collected during fall from 1967 to 2008 were examined to define abiotic habitat suitability for delta smelt as a function of salinity and water transparency, and to describe long-term trends in habitat conditions. The annual habitat index we developed, which incorporated both quantity and quality of habitat, decreased by 78% over the study period. Future habitat index values under seven different development and climate change scenarios, representing a range of drier and wetter possibilities, were predicted using a model which related estuarine outflow to the habitat index. The results suggested that each of the scenarios would generally lead to further declines in delta smelt habitat across all water year types. Recovery targets for delta smelt will be difficult to attain if the modeled habitat conditions are realized.  相似文献