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  • Blackwell Publishing Ltd  (65,655)
  • Periodicals Archive Online (PAO)  (41,766)
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  • 1
    Publication Date: 2022-04-01
    Description: We present a workflow to estimate geostatistical aquifer parameters from pumping test data using the Python package welltestpy. The procedure of pumping test analysis is exemplified for two data sets from the Horkheimer Insel site and from the Lauswiesen site, Germany. The analysis is based on a semi‐analytical drawdown solution from the upscaling approach Radial Coarse Graining, which enables to infer log‐transmissivity variance and horizontal correlation length, beside mean transmissivity, and storativity, from pumping test data. We estimate these parameters of aquifer heterogeneity from type‐curve analysis and determine their sensitivity. This procedure, implemented in welltestpy, is a template for analyzing any pumping test. It goes beyond the possibilities of standard methods, for example, based on Theis' equation, which are limited to mean transmissivity and storativity. A sensitivity study showed the impact of observation well positions on the parameter estimation quality. The insights of this study help to optimize future test setups for geostatistical aquifer analysis and provides guidance for investigating pumping tests with regard to aquifer statistics using the open‐source software package welltestpy.
    Description: Article impact statement: We present a workflow to infer parameters of subsurface heterogeneity from pumping test data exemplified at two sites using welltestpy.
    Description: German Federal Environmental Foundation (DBU) http://dx.doi.org/10.13039/100007636
    Keywords: ddc:551.49
    Language: English
    Type: doc-type:article
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  • 2
    Publication Date: 2022-04-01
    Description: In designed experiments, different sources of variability and an adequate scale of measurement need to be considered, but not all approaches in common usage are equally valid. In order to elucidate the importance of sources of variability and choice of scale, we conducted an experiment where the effects of biochar and slurry applications on soil properties related to soil fertility were studied for different designs: (a) for a field‐scale sampling design with either a model soil (without natural variability) as an internal control or with composited soils, (b) for a design with a focus on amendment variabilities, and (c) for three individual field‐scale designs with true field replication and a combined analysis representative of the population of loess‐derived soils. Three silty loam sites in Germany were sampled and the soil macroaggregates were crushed. For each design, six treatments (0, 0.15 and 0.30 g slurry‐N kg−1 with and without 30 g biochar kg−1) were applied before incubating the units under constant soil moisture conditions for 78 days. CO2 fluxes were monitored and soils were analysed for macroaggregate yields and associated organic carbon (C). Mixed‐effects models were used to describe the effects. For all soil properties, results for the loess sites differed with respect to significant contributions of fixed effects for at least one site, suggesting the need for a general inclusion of different sites. Analysis using a multilevel model allowed generalizations for loess soils to be made and showed that site:slurry:biochar and site:slurry interactions were not negligible for macroaggregate yields. The use of a model soil as an internal control enabled observation of variabilities other than those related to soils or amendments. Experiments incorporating natural variability in soils or amendments resulted in partially different outcomes, indicating the need to include all important sources of variability. Highlights Effects of biochar and slurry applications were studied for different designs and mixed‐effects models were used to describe the effects. Including an internal control allowed observation of, e.g., methodological and analytical variabilities. The results suggested the need for a general inclusion of different sites. Analysis using a multilevel model allowed generalizations for loess soils. The results indicated the need to include all important sources of variability.
    Keywords: ddc:631.4
    Language: English
    Type: doc-type:article
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  • 3
    Publication Date: 2022-04-01
    Description: Temperate forest soils are often considered as an important sink for atmospheric carbon (C), thereby buffering anthropogenic CO2 emissions. However, the effect of tree species composition on the magnitude of this sink is unclear. We resampled a tree species common garden experiment (six sites) a decade after initial sampling to evaluate whether forest floor (FF) and topsoil organic carbon (Corg) and total nitrogen (Nt) stocks changed in dependence of tree species (Norway spruce—Picea abies L., European beech—Fagus sylvatica L., pedunculate oak—Quercus robur L., sycamore maple—Acer pseudoplatanus L., European ash—Fraxinus excelsior L. and small‐leaved lime—Tilia cordata L.). Two groups of species were identified in terms of Corg and Nt distribution: (1) Spruce with high Corg and Nt stocks in the FF developed as a mor humus layer which tended to have smaller Corg and Nt stocks and a wider Corg:Nt ratio in the mineral topsoil, and (2) the broadleaved species, of which ash and maple distinguished most clearly from spruce by very low Corg and Nt stocks in the FF developed as mull humus layer, had greater Corg and Nt stocks, and narrow Corg:Nt ratios in the mineral topsoil. Over 11 years, FF Corg and Nt stocks increased most under spruce, while small decreases in bulk mineral soil (esp. in 0–15 cm and 0–30 cm depth) Corg and Nt stocks dominated irrespective of species. Observed decadal changes were associated with site‐related and tree species‐mediated soil properties in a way that hinted towards short‐term accumulation and mineralisation dynamics of easily available organic substances. We found no indication for Corg stabilisation. However, results indicated increasing Nt stabilisation with increasing biomass of burrowing earthworms, which were highest under ash, lime and maple and lowest under spruce. Highlights We studied if tree species differences in topsoil Corg and Nt stocks substantiate after a decade. The study is unique in its repeated soil sampling in a multisite common garden experiment. Forest floors increased under spruce, but topsoil stocks decreased irrespective of species. Changes were of short‐term nature. Nitrogen was most stable under arbuscular mycorrhizal species.
    Description: Deutsche Forschungsgemeinschaff (DFG)
    Keywords: ddc:551.9 ; ddc:631.41
    Language: English
    Type: doc-type:article
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  • 4
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    Cambridge University Press
    In:  EPIC3Antarctic Science, Cambridge University Press, 33(6), pp. 575-595, ISSN: 0954-1020
    Publication Date: 2022-01-13
    Description: The waters along the West Antarctic Peninsula (WAP) have experienced warming and increased freshwater inputs from melting sea ice and glaciers in recent decades. Challenges exist in understanding the consequences of these changes on the inorganic carbon system in this ecologically important and highly productive ecosystem. Distributions of dissolved inorganic carbon (CT), total alkalinity (AT) and nutrients revealed key physical, biological and biogeochemical controls of the calcium carbonate saturation state (Ωaragonite) in different water masses across the WAP shelf during the summer. Biological production in spring and summer dominated changes in surface water Ωaragonite (ΔΩaragonite up to +1.39; ∼90%) relative to underlying Winter Water. Sea-ice and glacial meltwater constituted a minor source of AT that increased surface water Ωaragonite (ΔΩaragonite up to +0.07; ∼13%). Remineralization of organic matter and an influx of carbon-rich brines led to cross-shelf decreases in Ωaragonite in Winter Water and Circumpolar Deep Water. A strong biological carbon pump over the shelf created Ωaragonite oversaturation in surface waters and suppression of Ωaragonite in subsurface waters. Undersaturation of aragonite occurred at 〈 ∼1000 m. Ongoing changes along the WAP will impact the biologically driven and meltwater-driven processes that influence the vulnerability of shelf waters to calcium carbonate undersaturation in the future.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
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  • 5
    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in [Schiller, C. M., Whitlock, C., Elder, K. L., Iverson, N. A., & Abbott, M. B. Erroneously old radiocarbon ages from terrestrial pollen concentrates in Yellowstone Lake, Wyoming, USA. Radiocarbon, 63(1), (2021): 321-342, https://doi.org/10.1017/RDC.2020.118.
    Description: Accelerator mass spectrometry (AMS) dating of pollen concentrates is often used in lake sediment records where large, terrestrial plant remains are unavailable. Ages produced from chemically concentrated pollen as well as manually picked Pinaceae grains in Yellowstone Lake (Wyoming) sediments were consistently 1700–4300 cal years older than ages established by terrestrial plant remains, tephrochronology, and the age of the sediment-water interface. Previous studies have successfully utilized the same laboratory space and methods, suggesting the source of old-carbon contamination is specific to these samples. Manually picking pollen grains precludes admixture of non-pollen materials. Furthermore, no clear source of old pollen grains occurs on the deglaciated landscape, making reworking of old pollen grains unlikely. High volumes of CO2 are degassed in the Yellowstone Caldera, potentially introducing old carbon to pollen. While uptake of old CO2 through photosynthesis is minor (F14C approximately 0.99), old-carbon contamination may still take place in the water column or in surficial lake sediments. It remains unclear, however, what mechanism allows for the erroneous ages of highly refractory pollen grains while terrestrial plant remains were unaffected. In the absence of a satisfactory explanation for erroneously old radiocarbon ages from pollen concentrates, we propose steps for further study.
    Description: This research was supported by NSF Grant No. 1515353 to C. Whitlock and sampling in Yellowstone National Park was conducted under permits YELL-SCI-0009 and YELL-SCI-5054.
    Keywords: AMS dating ; Chronology ; Contamination ; Paleoecology ; Pine
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 6
    Publication Date: 2022-10-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Roberts, Mark L., Elder, Kathryn L., Jenkins, William J., Gagnon, Alan R., Xu, Li, Hlavenka, Joshua D., & Longworth, Brett E. C-14 Blank Corrections for 25-100 mu G samples at the National Ocean Sciences AMS Laboratory. Radiocarbon, 61(5), (2019): 1403-1411, Doi: 10.1017/RDC.2019.74.
    Description: Replicate radiocarbon (14C) measurements of organic and inorganic control samples, with known Fraction Modern values in the range Fm = 0–1.5 and mass range 6 μg–2 mg carbon, are used to determine both the mass and radiocarbon content of the blank carbon introduced during sample processing and measurement in our laboratory. These data are used to model, separately for organic and inorganic samples, the blank contribution and subsequently “blank correct” measured unknowns in the mass range 25–100 μg. Data, formulas, and an assessment of the precision and accuracy of the blank correction are presented.
    Description: This work is supported by a Cooperative Agreement (OCE-1755125) with the U.S. National Science Foundation.
    Keywords: AMS ; AMS dating ; Blank corrections
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 7
    Publication Date: 2022-10-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Baker, M. G., Aster, R. C., Anthony, R. E., Chaput, J., Wiens, D. A., Nyblade, A., Bromirski, P. D., Gerstoft, P., & Stephen, R. A. Seasonal and spatial variations in the ocean-coupled ambient wavefield of the Ross Ice Shelf. Journal of Glaciology, 65(254), (2019): 912-925, doi:10.1017/jog.2019.64.
    Description: The Ross Ice Shelf (RIS) is host to a broadband, multimode seismic wavefield that is excited in response to atmospheric, oceanic and solid Earth source processes. A 34-station broadband seismographic network installed on the RIS from late 2014 through early 2017 produced continuous vibrational observations of Earth's largest ice shelf at both floating and grounded locations. We characterize temporal and spatial variations in broadband ambient wavefield power, with a focus on period bands associated with primary (10–20 s) and secondary (5–10 s) microseism signals, and an oceanic source process near the ice front (0.4–4.0 s). Horizontal component signals on floating stations overwhelmingly reflect oceanic excitations year-round due to near-complete isolation from solid Earth shear waves. The spectrum at all periods is shown to be strongly modulated by the concentration of sea ice near the ice shelf front. Contiguous and extensive sea ice damps ocean wave coupling sufficiently so that wintertime background levels can approach or surpass those of land-sited stations in Antarctica.
    Description: This research was supported by NSF grants PLR-1142518, 1141916, 1142126, 1246151 and 1246416. JC was additionally supported by Yates funds in the Colorado State University Department of Mathematics. PDB also received support from the California Department of Parks and Recreation, Division of Boating and Waterways under contract 11-106-107. We thank Reinhard Flick and Patrick Shore for their support during field work, Tom Bolmer in locating stations and preparing maps, and the US Antarctic Program for logistical support. The seismic instruments were provided by the Incorporated Research Institutions for Seismology (IRIS) through the PASSCAL Instrument Center at New Mexico Tech. Data collected are available through the IRIS Data Management Center under RIS and DRIS network code XH. The PSD-PDFs presented in this study were processed with the IRIS Noise Tool Kit (Bahavar and others, 2013). The facilities of the IRIS Consortium are supported by the National Science Foundation under Cooperative Agreement EAR-1261681 and the DOE National Nuclear Security Administration. The authors appreciate the support of the University of Wisconsin-Madison Automatic Weather Station Program for the data set, data display and information; funded under NSF grant number ANT-1543305. The Ross Ice Shelf profiles were generated using the Antarctic Mapping Tools (Greene and others, 2017). Regional maps were generated with the Generic Mapping Tools (Wessel and Smith, 1998). Topography and bathymetry data for all maps in this study were sourced from the National Geophysical Data Center ETOPO1 Global Relief Model (doi:10.7289/V5C8276M). We thank two anonymous reviewers for suggestions on the scope and organization of this paper.
    Keywords: Antarctic glaciology ; Ice shelves ; Seismology
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 8
    Publication Date: 2022-10-26
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Xu, L., Roberts, M., Elder, K., Hansman, R., Gagnon, A., & Kurz, M. Radiocarbon in dissolved organic carbon by UV oxidation: an update of procedures and blank characterization at NOSAMS. Radiocarbon, 64(1), (2022): 195-199, https://doi.org/10.1017/rdc.2022.4.
    Description: This note describes improvements of UV oxidation method that is used to measure carbon isotopes of dissolved organic carbon (DOC) at the National Ocean Sciences Accelerator Mass Spectrometry Facility (NOSAMS). The procedural blank is reduced to 2.6 ± 0.6 μg C, with Fm of 0.42 ± 0.10 and δ13C of –28.43 ± 1.19‰. The throughput is improved from one sample per day to two samples per day.
    Description: We gratefully acknowledge support from the U.S. National Science Foundation, via NSF-OCE-1755125.
    Keywords: Blank ; Dissolved organic carbon ; Radiocarbon ; UV-oxidation
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 9
    Publication Date: 2022-10-21
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ackley, S. F., Stammerjohn, S., Maksym, T., Smith, M., Cassano, J., Guest, P., Tison, J., Delille, B., Loose, B., Sedwick, P., DePace, L., Roach, L., & Parno, J. Sea-ice production and air/ice/ocean/biogeochemistry interactions in the Ross Sea during the PIPERS 2017 autumn field campaign. Annals of Glaciology, 61(82), (2020): 181-195, doi:10.1017/aog.2020.31.
    Description: The Ross Sea is known for showing the greatest sea-ice increase, as observed globally, particularly from 1979 to 2015. However, corresponding changes in sea-ice thickness and production in the Ross Sea are not known, nor how these changes have impacted water masses, carbon fluxes, biogeochemical processes and availability of micronutrients. The PIPERS project sought to address these questions during an autumn ship campaign in 2017 and two spring airborne campaigns in 2016 and 2017. PIPERS used a multidisciplinary approach of manned and autonomous platforms to study the coupled air/ice/ocean/biogeochemical interactions during autumn and related those to spring conditions. Unexpectedly, the Ross Sea experienced record low sea ice in spring 2016 and autumn 2017. The delayed ice advance in 2017 contributed to (1) increased ice production and export in coastal polynyas, (2) thinner snow and ice cover in the central pack, (3) lower sea-ice Chl-a burdens and differences in sympagic communities, (4) sustained ocean heat flux delaying ice thickening and (5) a melting, anomalously southward ice edge persisting into winter. Despite these impacts, airborne observations in spring 2017 suggest that winter ice production over the continental shelf was likely not anomalous.
    Description: NSF supported PIPERS award numbers: ANT-1341717 (S.F. Ackley, UTSA); ANT-1341513 (E. Maksym, WHOI); ANT-1341606 (S. Stammerjohn and J. Cassano, U Colorado); ANT-1341725 (P. Guest, NPS). P. Sedwick was supported by NSF ANT-1543483. S.F. Ackley was also supported by NASA Grant 80NSSC19M0194 to the Center for Advanced Measurements in Extreme Environments at UTSA. S. Stammerjohn was also supported by the LTER Program under NFS award number ANT-0823101 (H. Ducklow, LDEO/Columbia University). Additional support was by the Belgian F.R.S-FNRS (project ISOGGAP and IODIne, contract T.0268.16 and J.0262.17, respectively). Bruno Delille is a research associate of the F.R.S.-FNRS. Terra-Sar-X quicklook imagery was coordinated by Kathrin Hoeppner at DLR, and Andy Archer (with the Antarctic Support Contractor) provided selected (cloud-free) MODIS scenes and daily maps of AMSR2 sea-ice concentration.
    Keywords: Atmosphere/ice/ocean interactions ; Ice/ocean interactions ; Sea ice ; Sea-ice growth and decay
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 10
    Publication Date: 2022-06-22
    Description: Pliocene–Quaternary faults are relevant structures with which to constrain the seismotectonic context and contribute to the evaluation of the seismic hazard of a region. Many of these faults, however, do not show clear surface evidence even when releasing earthquakes. For these reasons they can be extremely dangerous as they receive relatively little attention and can be difficult to identify. From among the various surface geology studies and/or palaeoseismological investigations, we focus our attention on the integration of different datasets such as seismic reflection profiles, surface kinematic data and the relocation of seismological data, which make it possible to identify and characterize active faults whose dimension and earthquake potential would otherwise not be large enough to make them identifiable. We take as an example the Montespertoli NE-trending fault in southern Tuscany (central Italy) with which we associate the 2016 M=3.9 Castelfiorentino earthquake. This structure is part of a wider (in the order of 15–20 km) crustal-scale shear zone, which may be responsible for strong historical earthquakes in the area.
    Description: Published
    Description: 853 - 872
    Description: 4T. Sismicità dell'Italia
    Description: JCR Journal
    Keywords: active faults ; seismic faults ; Earthquakes ; strike-slip faults ; inner Northern Apennines ; solid earth
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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