Statistically downscaled projections of snow/rain partitioning for Alaska          下载免费PDF全文

Stephanie A. McAfee  John Walsh  T. Scott Rupp 《水文研究》2014,28(12):3930-3946

Adaptation planning in Alaska, as in other snowy parts of the world, will require snow projections, yet snow is a challenging variable to measure, simulate and downscale. Here we describe the construction and evaluation of 771‐m‐resolution gridded historical and statistically downscaled projections of snow/rain partitioning for the state of Alaska at decadal temporal resolution. The method developed here uses observational data to describe the relationship between average monthly temperature and the fraction of wet days in that month receiving snow, the snow‐day fraction. Regionally and seasonally specific equations were developed to accommodate variability in synoptic scale climatology of rain and snow events. These equations were then applied to gridded decadal temperature data and projections. The gridded products provide a reasonable characterization of snow‐day fraction throughout the state. However, there are local deviations from the regional relationships, particularly in the topographically complex areas ringing the Gulf of Alaska and Cook Inlet. When applied to questions about changing precipitation regimes in northern, western and south‐eastern Alaska, these data demonstrate the potential for marked changes from snow‐dominated to mixed precipitation regimes and also exhibit a wide range of potential future conditions. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Quantifying annual groundwater recharge and storage in the central Sierra Nevada using naturally occurring 35S          下载免费PDF全文

Stephanie H. Urióstegui  Richard K. Bibby  Bradley K. Esser  Jordan F. Clark 《水文研究》2017,31(6):1382-1397

Identifying aquifer vulnerability to climate change is of vital importance in the Sierra Nevada and other snow‐dominated basins where groundwater systems are essential to water supply and ecosystem health. Quantifying the component of new (current year's) snowmelt in groundwater and surface water is useful in evaluating aquifer vulnerability because significant annual recharge may indicate that streamflow will respond rapidly to annual variability in precipitation, followed by more gradual decreases in recharge as recharge declines over decades. Hydrologic models and field‐based studies have indicated that young (<1 year) water is an important component of streamflow. The goal of this study was to utilize the short‐lived, naturally occurring cosmogenic isotope sulfur‐35 (³⁵S) to quantify new snowmelt contribution to groundwater and surface waters in Sagehen Creek Basin (SCB) and Martis Valley Groundwater Basin (MVGB) located within the Tertiary volcanics of the central Sierra Nevada, CA. Activities of ³⁵S were measured in dissolved sulfate (³⁵SO₄^2?) in SCB and MVGB snowpack, groundwater, springs, and streamflow. The percent of new snowmelt (PNS) in SCB streamflow ranged from 0.2 ± 6.6% during baseflow conditions to 14.0 ± 3.4% during high‐flow periods of snowmelt. Similar to SCB, the PNS in MVGB groundwater and streamflow was typically <30% with the largest fractions occurring in late spring or early summer following peak streamflow. The consistently low PNS suggests that a significant fraction of annual snowmelt in SCB and MVGB recharges groundwater, and groundwater contributions to streamflow in these systems have the potential to mitigate climate change impacts on runoff.  相似文献   

The planet formation imager     

John D. Monnier  Stefan Kraus  Michael J. Ireland  Fabien Baron  Amelia Bayo  Jean-Philippe Berger  Michelle Creech-Eakman  Ruobing Dong  Gaspard Duchêne  Catherine Espaillat  Chris Haniff  Sebastian Hönig  Andrea Isella  Attila Juhasz  Lucas Labadie  Sylvestre Lacour  Stephanie Leifer  Antoine Merand  Ernest Michael  Stefano Minardi  Christoph Mordasini  David Mozurkewich  Johan Olofsson  Claudia Paladini  Romain Petrov  Jörg-Uwe Pott  Stephen Ridgway  Stephen Rinehart  Keivan Stassun  Jean Surdej  Theo ten Brummelaar  Neal Turner  Peter Tuthill  Kerry Vahala  Gerard van Belle  Gautam Vasisht  Ed Wishnow  John Young  Zhaohuan Zhu 《Experimental Astronomy》2018,46(3):517-529

The Planet Formation Imager (PFI, www.planetformationimager.org) is a next-generation infrared interferometer array with the primary goal of imaging the active phases of planet formation in nearby star forming regions. PFI will be sensitive to warm dust emission using mid-infrared capabilities made possible by precise fringe tracking in the near-infrared. An L/M band combiner will be especially sensitive to thermal emission from young exoplanets (and their disks) with a high spectral resolution mode to probe the kinematics of CO and H₂O gas. In this paper, we give an overview of the main science goals of PFI, define a baseline PFI architecture that can achieve those goals, point at remaining technical challenges, and suggest activities today that will help make the Planet Formation Imager facility a reality.  相似文献   

Deriving snow‐cover depletion curves for different spatial scales from remote sensing and snow telemetry data          下载免费PDF全文

Steven R. Fassnacht  Graham A. Sexstone  Amir H. Kashipazha  Juan Ignacio López‐Moreno  Michael F. Jasinski  Stephanie K. Kampf  Benjamin C. Von Thaden 《水文研究》2016,30(11):1708-1717

During the melting of a snowpack, snow water equivalent (SWE) can be correlated to snow‐covered area (SCA) once snow‐free areas appear, which is when SCA begins to decrease below 100%. This amount of SWE is called the threshold SWE. Daily SWE data from snow telemetry stations were related to SCA derived from moderate‐resolution imaging spectroradiometer images to produce snow‐cover depletion curves. The snow depletion curves were created for an 80 000 km² domain across southern Wyoming and northern Colorado encompassing 54 snow telemetry stations. Eight yearly snow depletion curves were compared, and it is shown that the slope of each is a function of the amount of snow received. Snow‐cover depletion curves were also derived for all the individual stations, for which the threshold SWE could be estimated from peak SWE and the topography around each station. A station's peak SWE was much more important than the main topographic variables that included location, elevation, slope, and modelled clear sky solar radiation. The threshold SWE mostly illustrated inter‐annual consistency. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Political ecology and habitat conservation for endangered species planning in Southern California: Region, places, and ecological governance     

Stephanie Pincetl  A.E. Jonas 《Geoforum》2011,42(4):427-438

The county of Riverside California has a long history of land conservation. In this comparative case study between Western Riverside County and the Coachella Valley area in the county we show how governance institutions that encompass regions that have very different ecologies, are governed by rules and regulations that are undifferentiated relative to those differences. The study argues, however, that what may differ are the workings of the local urban regimes and the metabolic appropriation of ecosystems for economic growth. In this close investigation of the sprawling county of Riverside we find very different approaches to habitat preservation and the enrollment of nature for wealth production by the local urban regimes.  相似文献   

Influence of hardpan layers on arsenic mobility in historical gold mine tailings     

Stephanie L. DeSisto  Heather E. Jamieson  Michael B. Parsons 《Applied Geochemistry》2011,26(12):2004-2018

Hardpans, or cemented layers, form by precipitation and cementation of secondary minerals in mine tailings and may act as both physical and chemical barriers. Precipitation of secondary minerals during weathering of tailings can sequester metal(loid)s, thereby limiting their release to the environment. At Montague Gold Mines in Nova Scotia, tailings are partially cemented by the Fe arsenate mineral scorodite (FeAsO₄·2H₂O). Previous studies have shown that the formation of scorodite can effectively limit aqueous As concentrations due to its relatively low solubility (<1 mg/L at pH 3–4) and high As content (43–52 wt.% As₂O₅, this study). Co-existing waters and solids were sampled at Montague Gold Mines to identify present-day field conditions influencing scorodite precipitation and dissolution, and to better understand the mineralogical and chemical relationship between hardpan and tailings. In addition to scorodite, hardpan cements were found to include amorphous Fe arsenate and Fe oxyhydroxide. Nearly all hardpan is associated with historical arsenopyrite-bearing concentrate which provides a source of acidity, As⁵⁺ and Fe³⁺ for secondary mineral precipitation. Pore waters sampled from the hardpan have pH values ranging from 2.43 to 7.06. Waters with the lowest pH values also have the highest As concentrations (up to 35.8 mg/L) and are associated with the most extensive hardpan and greatest amount of weathered sulfide. Samples from areas with discontinuous hardpan and less sulfide have near-neutral pH and lower As concentrations. Detailed petrographic observations indicate that the identity and stability of As-bearing secondary minerals depends on the continued availability of sulfide concentrate. The results of this study are being used to develop remediation strategies for highly weathered, hardpan-bearing tailings that consider the stability of both primary and secondary minerals under various cover scenarios.  相似文献   

Sources of elevated salinity in the Mississippi River Alluvial Aquifer, south-central Louisiana, USA     

Stephanie E. WelchJeffrey S. Hanor 《Applied Geochemistry》2011,26(8):1446-1451

Salinization is a process impacting groundwater quality and availability across much of southern Louisiana, USA. However, a broad divergence of opinion exists regarding the causes of this elevated salinity: updip-migrating marine waters from the Gulf of Mexico, saline fluids migrating up fault planes, movement of water from salt domes, and/or remnant seawater from the last major marine transgression. The Mississippi River Alluvial Aquifer (MRAA) in south-central Louisiana is recharged by the Mississippi River, and there are discharge zones to the west and east. Recharge waters from the Mississippi River are fresh, but Cl⁻ levels in the western portions of the aquifer are as high as 1000 mg/L. The aquifer is an important source of water for several municipalities and industries, but prior to this study the source(s) of the elevated salinity or whether the salinization can be remediated had not been determined.The low Br/Cl ratios in the groundwaters are consistent with a saline endmember produced by subsurface dissolution of salt domes, not a marine source. The H and O isotopic systematics of the aquifer waters indicate meteoric sources for the H₂O, not marine waters or diagenetically-altered deep brines. The westward salinization of aquifer water represents a broad regional process, instead of contamination by point sources. Mapping of spatial variations in salinity has permitted the identification of specific salt domes whose subsurface dissolution is producing waters of elevated salinity in the aquifer. These include the Bayou Choctaw and St. Gabriel domes, and possibly the Bayou Blue dome. Salinization is a natural, on-going process, and the potential for remediation or control is slight, if not non-existent.  相似文献   

The relative importance of buffering and brine inputs in controlling the abundance of Na and Ca in sedimentary formation waters   总被引：1，自引：0，他引：1  

Stephanie Houston  Craig SmalleyAdam Laycock  Bruce W.D. Yardley 《Marine and Petroleum Geology》2011,28(6):1242-1251

The concentration of Ca in the formation waters of petroleum reservoirs can play a major role in influencing the outcome of a number of processes that are of great significance to the oil industry. For example, formation water Ca concentration affects the risk of carbonate scale formation during production. In order to better understand the concentrations of Ca in formation waters, we have investigated the chemistries of formation waters from a range of onshore and offshore basins worldwide, using published sources, as well as unpublished data held by BP. Although calcium and sodium are the principal cations in almost all formation waters they vary enormously in their relative proportions. We have identified three distinct trends on a plot of X_Ca (Ca/(Na + Ca)) against Cl. Most data lie on a high-Ca trend, here termed Trend 1, and show an increase in X_Ca with salinity. We interpret this as tracking equilibration with Ca and Na-bearing minerals, with the ratio (mol Ca/mol Na²) remaining approximately constant irrespective of salinity for chloride-dominated fluids. At very high salinities, Br-enriched bittern brines that have taken part in dolomitisation lie at the Cl-rich end of this trend. Some brines remain Na-dominated up to very high salinities and define a distinct low-Ca trend, Trend 2. These are associated with dissolution of halite beds and are interpreted to arise when the amount of Na in the pore fluid greatly exceeds the amount of Ca available in minerals. We refer to such brines as mass-limited; the sparsity of Ca in the rock-fluid system constrains X_Ca to a low value. Remarkably few brines lie between these trends. Finally, dilute formation waters show very large variations in X_Ca and may have bicarbonate as the dominant anion. They define a distinct low-Cl trend, Trend 3. We conclude that the behaviour of Na and Ca in most formation waters reflects equilibration with minerals, and concentrations of Ca in solution are sensitive to pH and P_CO2 as well as to chloride concentration. For some brines however, the amount of salts in solution is sufficient to overwhelm the buffering capacity of the wallrocks.  相似文献   

The Kuroshio Extension and its recirculation gyres     

Steven R. Jayne  Nelson G. Hogg  Stephanie N. Waterman  Luc Rainville  Kathleen A. Donohue  D. Randolph Watts  Karen L. Tracey  Julie L. McClean  Mathew E. Maltrud  Bo Qiu  Shuiming Chen  Peter Hacker 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(12):2088-2099

This paper reports on the strength and structure of the Kuroshio Extension and its recirculation gyres. In the time average, quasi-permanent recirculation gyres are found to the north and south of the Kuroshio Extension jet. The characteristics of these recirculations gyres are determined from the combined observations from the Kuroshio Extension System Study (KESS) field program (June 2004–June 2006) and include current meters, pressure and current recording inverted echo sounders, and subsurface floats. The position and strength of the recirculation gyres simulated by a high-resolution numerical model are found to be consistent with the observations. The circulation pattern that is revealed is of a complex system of multiple recirculation gyres that are embedded in the crests and troughs of the quasi-permanent meanders of the Kuroshio Extension. At the location of the KESS array, the Kuroshio Extension jet and its recirculation gyres transport of about 114 Sv. This represents a 2.7-fold increase in the transport of the current compared to the Kuroshio's transport at Cape Ashizuri before it separates from the coast and flows eastward into the open ocean. This enhancement in the current's transport comes from the development of the flanking recirculation gyres. Estimates from an array of inverted echo sounders and a high-resolution ocean general circulation model are of similar magnitude.  相似文献   

Upper Jurassic stratigraphy and sedimentary facies in the Central Outer Moray Firth Basin,North Sea     

Colin C. Turner  Philip C. Richards  John L. Swallow  Stephanie P. Grimshaw 《Marine and Petroleum Geology》1984,1(2):105-117

The Upper Jurassic of the Outer Moray Firth Basin can be divided into two main stratigraphic units — the Piper and Kimmeridge Clay Formations. In each of these formations five major sedimentary facies can be recognized. The Piper Formation, of late Oxfordian to early Kimmeridgian age, comprises very fine to coarse-grained sandstones and minor mudstone of clastic shelf to shoreline origin. Large scale upward-coarsening sequences are well developed in some areas, particularly in the reservoir sands of the Tartan oilfield, and are interpreted as regressive, possibly deltaic deposits. The unconformably overlying Kimmeridge Clay Formation ranges in age from late Oxfordian through Volgian to Ryazanian. The formation is predominantly argillaceous, but also contains locally thick accumulations of sandstone deposited by gravity flow processes. The Claymore Sandstone Member is proposed as a new name for these sandstones in the region of the Claymore oilfield, where they form the major reservoir. Sands of the Piper Formation were derived mainly from the south-west, although some input from the north may also have occurred. Deposition may have extended further eastwards than the present erosional limit of the sands. Thick sand sequences in the Kimmeridge Clay Formation are probably restricted to the margins of the Witch Ground Graben, where contemporaneous faulting occurred.  相似文献