Export and mesopelagic particle flux during a North Atlantic spring diatom bloom   总被引：2，自引：0，他引：2  

Patrick Martin  Richard S. LampittMary Jane Perry  Richard SandersCraig Lee  Eric D'Asaro 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(4):338-349

Spring diatom blooms are important for sequestering atmospheric CO₂ below the permanent thermocline in the form of particulate organic carbon (POC). We measured downward POC flux during a sub-polar North Atlantic spring bloom at 100 m using thorium-234 (²³⁴Th) disequilibria, and below 100 m using neutrally buoyant drifting sediment traps. The cruise followed a Lagrangian float, and a pronounced diatom bloom occurred in a 600 km² area around the float. Particle flux was low during the first three weeks of the bloom, between 10 and 30 mg POC m⁻² d⁻¹. Then, nearly 20 days after the bloom had started, export as diagnosed from ²³⁴Th rose to 360-620 mg POC m⁻² d⁻¹, co-incident with silicate depletion in the surface mixed layer. Sediment traps at 600 and 750 m depth collected 160 and 150 mg POC m⁻² d⁻¹, with a settled volume of particles of 1000-1500 mL m⁻² d⁻¹. This implies that 25-43% of the 100 m POC export sank below 750 m. The sinking particles were ungrazed diatom aggregates that contained transparent exopolymer particles (TEP). We conclude that diatom blooms can lead to substantial particle export that is transferred efficiently through the mesopelagic. We also present an improved method of calibrating the Alcian Blue solution against Gum Xanthan for TEP measurements.  相似文献   

A lightweight vertical rosette for deployment in ice-covered waters     

William M. Smethie Jr.  Dale ChayesRichard Perry  Peter Schlosser 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(4):460-467

A lightweight modular rosette system has been developed that can be launched and recovered from aircraft in ice-covered waters through a 12 in. diameter hole in the ice. The small diameter is achieved by the modular design, in which a CTD module is attached to the end of a conducting cable and water bottle modules (four 4-L bottles per module) are positioned vertically above it. A novel tripping mechanism based on melting a link of monofilament line is used to close the water bottles at the desired depths. After launching the rosette, the cast proceeds like a normal rosette cast with the traces of temperature, salinity, oxygen and other desired sensors being displayed on a computer screen during the down and up casts and tripping the bottles electronically at the desired depths on the up cast. A Seabird 19+ CTD and Seabird 43 oxygen sensor are mounted in the CTD module and data acquisition and bottle tripping are controlled using a Seabird 33 deck unit and Seabird's SeaSave software run on a laptop computer. Deployment and recovery are done in a heated tent attached to the aircraft to prevent the water from freezing. After recovery the bottle modules are placed in coolers with bags of snow to stabilize the cooler temperature close to 0 °C, which is within ±1.8 °C of the in situ temperature, and the modules are transported back to a base camp for subsampling and sample processing. This system has been used to collect over 250 water samples in the ice-covered Lincoln Sea and the quality of the samples for dissolved gases and other constituents has been excellent.  相似文献   

New insights into the heterogeneity of the Tagish Lake meteorite: Soluble organic compositions of variously altered specimens     

Danielle N. Simkus  Jos C. Aponte  Jamie E. Elsila  Robert W. Hilts  Hannah L. McLain  Christopher D. K. Herd 《Meteoritics & planetary science》2019,54(6):1283-1302

The Tagish Lake carbonaceous chondrite exhibits a unique compositional heterogeneity that may be attributed to varying degrees of aqueous alteration within the parent body asteroid. Previous analyses of soluble organic compounds from four Tagish Lake meteorite specimens (TL5b, TL11h, TL11i, TL11v) identified distinct distributions and isotopic compositions that appeared to be linked to their degree of parent body processing (Herd et al. 2011; Glavin et al. 2012; Hilts et al. 2014). In the present study, we build upon these initial observations and evaluate the molecular distribution of amino acids, aldehydes and ketones, monocarboxylic acids, and aliphatic and aromatic hydrocarbons, including compound‐specific δ¹³C compositions, for three additional Tagish Lake specimens: TL1, TL4, and TL10a. TL1 contains relatively high abundances of soluble organics and appears to be a moderately altered specimen, similar to the previously analyzed TL5b and TL11h lithologies. In contrast, specimens TL4 and TL10a both contain relatively low abundances of all of the soluble organic compound classes measured, similar to TL11i and TL11v. The organic‐depleted composition of TL4 appears to have resulted from a relatively low degree of parent body aqueous alteration. In the case of TL10a, some unusual properties (e.g., the lack of detection of intrinsic monocarboxylic acids and aliphatic and aromatic hydrocarbons) suggest that it has experienced extensive alteration and/or a distinct organic‐depleted alteration history. Collectively, these varying compositions provide valuable new insights into the relationships between asteroidal aqueous alteration and the synthesis and preservation of soluble organic compounds.  相似文献   

A Patch‐based Cellular Automaton for Simulating Land‐use Changes at Fine Spatial Resolution     

Fang Wang  Danielle J. Marceau 《Transactions in GIS》2013,17(6):828-846

While cellular automata have become popular tools for modeling land‐use changes, there is a lack of studies reporting their application at very fine spatial resolutions (e.g. 5 m resolution). Traditional cell‐based CA do not generate reliable results at such resolutions because single cells might only represent components of land‐use entities (i.e. houses or parks in urban residential areas), while recently proposed entity‐based CA models usually ignore the internal heterogeneity of the entities. This article describes a patch‐based CA model designed to deal with this problem by integrating cell and object concepts. A patch is defined as a collection of adjacent cells that might have different attributes, but that represent a single land‐use entity. In this model, a transition probability map was calculated at each cell location for each land‐use transition using a weight of evidence method; then, land‐use changes were simulated by employing a patch‐based procedure based on the probability maps. This CA model, along with a traditional cell‐based model were tested in the eastern part of the Elbow River watershed in southern Alberta, Canada, an area that is under considerable pressure for land development due to its proximity to the fast growing city of Calgary. The simulation results for the two models were compared to historical data using visual comparison, K_simulation indices, and landscape metrics. The results reveal that the patch‐based CA model generates more compact and realistic land‐use patterns than the traditional cell‐based CA. The K_simulation values indicate that the land‐use maps obtained with the patch‐based CA are in higher agreement with the historical data than those created by the cell‐based model, particularly regarding the location of change. The landscape metrics reveal that the patch‐based model is able to adequately capture the land‐use dynamics as observed in the historical data, while the cell‐based CA is not able to provide a similar interpretation. The patch‐based approach proposed in this study appears to be a simple and valuable solution to take into account the internal heterogeneity of land‐use classes at fine spatial resolutions and simulate their transitions over time.  相似文献   

Gender Differences in Chronic Exposure to Traffic-Related Air Pollution—A Simulation Study of Working Females and Males     

Eleanor Setton  C. Peter Keller  Denise Cloutier-Fisher  Perry W. Hystad 《The Professional geographer》2013,65(1):66-83

The objective of this study was to identify spatial variability in exposure to outdoor traffic-related air pollution with specific emphasis on comparing exposure estimates for working females and males across a metropolitan area. A spatial exposure simulation model was used to estimate annual average exposure to traffic-related nitrogen dioxide for males and females reporting regular work in census tracts other than that of their residence, in Vancouver, British Columbia. The model produced estimates of annual average exposure in six microenvironments (home indoor, work indoor, other indoor, outdoor, in-vehicle to work, and in-vehicle other) using time-activity patterns and work flow data, for males and females in each of 382 census tracts. This allowed for the identification of spatial variations in exposure estimates for each gender, due to mobility within the study region. Indoor sources of nitrogen dioxide were not included in the simulation. No significant differences in estimated total exposure were found between working females and males in general. Small but observable spatial differences, however, were found between working females and males at the 90th percentile of the exposure distributions associated specifically with the work indoor microenvironment. These were highest in suburban areas (+3 μ g/m³ for females, relative to total exposures in the range of 26 to 37 μ g/m³ annual average hourly nitrogen dioxide). These results identify specific geographic locations in the study area where personal monitoring studies might be warranted and suggest that the inclusion of workplace locations in multivariate modeling could be useful to further understand differences in estimated exposures.  相似文献   

Geography,Race, and Quantification   总被引：1，自引：0，他引：1  

Perry L. Carter 《The Professional geographer》2013,65(4):465-480

This article reviews how race, quantification, and raced quantification have been used and written about in geography. Its two primary arguments are that race should be more central in the discipline and that a reluctance to address ontological and epistemological issues has left quantitative geography methodologically impoverished. These two issues merge in an examination of two cases where race is employed as a variable in quantitative models. The critique of these cases is not meant as a condemnation of quantitative geography but as an instructive example on which to construct a critical quantitative geography. The article ends by stressing the importance of quantification in geography and by presenting exemplars of race-critical quantification.  相似文献   

Our gun: a Wanganui Krupp gun story by Geoff Lawson,privately published by the author, 3 Wilkie Street,Wanganui, 2012. 96 pp. ISBN 978‐0‐473‐20742‐2.     

Peter Perry 《New Zealand geographer》2013,69(1):78-79

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A Middle Devensian woolly rhinoceros (Coelodonta antiquitatis) from Whitemoor Haye Quarry,Staffordshire (UK): palaeoenvironmental context and significance     

Danielle Schreve  Andy Howard  Andrew Currant  Stephen Brooks  Simon Buteux  Russell Coope  Barnaby Crocker  Michael Field  Malcolm Greenwood  James Greig  Phillip Toms 《第四纪科学杂志》2013,28(2):118-130

This paper reports the discovery of a rare partial skeleton of a woolly rhinoceros (Coelodonta antiquitatis Blumenbach, 1799) and associated fauna from a low Pleistocene terrace of the River Tame at Whitemoor Haye, Staffordshire, UK. A study of the sedimentary deposits around the rhino skeleton and associated organic‐rich clasts containing pollen, plant and arthropod remains suggests that the animal was rapidly buried on a braided river floodplain surrounded by a predominantly treeless, herb‐rich grassland. Highlights of the study include the oldest British chironomid record published to date and novel analysis of the palaeoflow regime using caddisfly remains. For the first time, comparative calculations of coleopteran and chironomid palaeotemperatures have been made on the same samples, suggesting a mean July temperature of 8–11 °C and a mean December temperature of between ?22 and ?16 °C. Radiocarbon age estimates on skeletal material, supported by optically stimulated luminescence ages from surrounding sediments, indicate that the rhino lived around 41–43 k cal a BP. The combined geochronological, stratigraphic and palaeoenvironmental evidence places the assemblage firmly within the Middle Devensian (Marine Oxygen Isotope Stage 3). This would agree with other regional evidence for the timing of aggradation for the lowest terrace of the Trent and its tributary systems. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Snow rollers ‐ Lakeburn,N.B. April 5, 1972     

M.J. Perry 《大气与海洋》2013,51(4):138-139

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First Imaging of Coronal Mass Ejections in the Heliosphere Viewed from Outside the Sun – Earth Line     

Richard A. Harrison  Christopher J. Davis  Christopher J. Eyles  Danielle Bewsher  Steve R. Crothers  Jackie A. Davies  Russell A. Howard  Daniel J. Moses  Dennis G. Socker  Jeffrey S. Newmark  Jean-Philippe Halain  Jean-Marc Defise  Emmanuel Mazy  Pierre Rochus  David F. Webb  George M. Simnett 《Solar physics》2008,247(1):171-193

We show for the first time images of solar coronal mass ejections (CMEs) viewed using the Heliospheric Imager (HI) instrument aboard the NASA STEREO spacecraft. The HI instruments are wide-angle imaging systems designed to detect CMEs in the heliosphere, in particular, for the first time, observing the propagation of such events along the Sun – Earth line, that is, those directed towards Earth. At the time of writing the STEREO spacecraft are still close to the Earth and the full advantage of the HI dual-imaging has yet to be realised. However, even these early results show that despite severe technical challenges in their design and implementation, the HI instruments can successfully detect CMEs in the heliosphere, and this is an extremely important milestone for CME research. For the principal event being analysed here we demonstrate an ability to track a CME from the corona to over 40 degrees. The time – altitude history shows a constant speed of ascent over at least the first 50 solar radii and some evidence for deceleration at distances of over 20 degrees. Comparisons of associated coronagraph data and the HI images show that the basic structure of the CME remains clearly intact as it propagates from the corona into the heliosphere. Extracting the CME signal requires a consideration of the F-coronal intensity distribution, which can be identified from the HI data. Thus we present the preliminary results on this measured F-coronal intensity and compare these to the modelled F-corona of Koutchmy and Lamy (IAU Colloq. 85, 63, 1985). This analysis demonstrates that CME material some two orders of magnitude weaker than the F-corona can be detected; a specific example at 40 solar radii revealed CME intensities as low as 1.7×10⁻¹⁴ of the solar brightness. These observations herald a new era in CME research as we extend our capability for tracking, in particular, Earth-directed CMEs into the heliosphere.  相似文献