Evaluation of Noble Gas Recharge Temperatures in a Shallow Unconfined Aquifer   总被引：1，自引：0，他引：1  

by Bradley D. Cey  G. Bryant Hudson  Jean E. Moran  Bridget R. Scanlon 《Ground water》2009,47(5):646-659

Water table temperatures inferred from dissolved noble gas concentrations (noble gas temperatures, NGT) are useful as a quantitative proxy for air temperature change since the last glacial maximum. Despite their importance in paleoclimate research, few studies have investigated the relationship between NGT and actual recharge temperatures in field settings. This study presents dissolved noble gas data from a shallow unconfined aquifer heavily impacted by agriculture. Considering samples unaffected by degassing, NGT calculated from common physically based interpretive gas dissolution models that correct measured noble gas concentrations for "excess air" agreed with measured water table temperatures (WTT). The ability to fit data to multiple interpretive models indicates that model goodness-of-fit does not necessarily mean that the model reflects actual gas dissolution processes. Although NGT are useful in that they reflect WTT, caution is recommended when using these interpretive models. There was no measurable difference in excess air characteristics (amount and degree of fractionation) between two recharge regimes studied (higher flux recharge primarily during spring and summer vs. continuous, low flux recharge). Approximately 20% of samples had dissolved gas concentrations below equilibrium concentration with respect to atmospheric pressure, indicating degassing. Geochemical and dissolved gas data indicate that saturated zone denitrification caused degassing by gas stripping. Modeling indicates that minor degassing (<10% ΔNe) may cause underestimation of ground water recharge temperature by up to 2°C. Such errors are problematic because degassing may not be apparent and degassed samples may be fit by a model with a high degree of certainty.  相似文献   

A Motion-Stabilized W-Band Radar for Shipboard Observations of Marine Boundary-Layer Clouds     

Ken Moran  Sergio Pezoa  Chris Fairall  Chris Williams  Tom Ayers  Alan Brewer  Simon P. de Szoeke  Virendra Ghate 《Boundary-Layer Meteorology》2012,143(1):3-24

Cloud radars at X, Ka and W-bands have been used in the past for ocean studies of clouds, but the lack of suitable stabilization has limited their usefulness in obtaining accurate measurements of the velocity structure of cloud particles and the heights of cloud features. A 94 GHz (W-band) radar suitable for use on shipboard studies of clouds has been developed that is small and lightweight and can maintain the radar’s beam pointing in the vertical to reduce the affects of the pitch and roll of the ship. A vertical velocity sensor on the platform allows the effects of the ship’s heave to be removed from the measured cloud particle motions. Results from the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-Rex) field program on the NOAA vessel Ronald H. Brown demonstrate the improvements to the cloud measurements after the ship’s motion effects are removed. The compact design of the radar also makes it suitable for use in aircraft studies. The radar is being repackaged to fit in an aft bay of a NOAA P3 aircraft to observe sea-spray profiles during ocean storms.  相似文献   

Coping with Complexity: Adaptive Governance in Desert Australia   总被引：1，自引：0，他引：1  

Mark Moran  Ruth Elvin 《GeoJournal》2009,74(5):415-428

Governance in Aboriginal settlements in desert Australia is changing at an unprecedented rate. Aboriginal leaders and community managers describe the change as bewildering, with ever-revolving agents and agencies and increasing quantities of administration. Governments are preoccupied with finding linear ‘solutions’ to new conceptualisations of the ‘problem’ and packaging these for top-down implementation. However, governance in practice involves multi-dimensional interactions of a complex system, which are difficult to predict, let alone to control for outcomes. Through the lens of complex adaptive systems (CAS) theory, this paper argues that there is potential to improve governance as an adaptive system through three principles that enhance local feedback: (1) application of the subsidiarity principle to different levels in the governance system would realise a better match between decentralised functions and local capacity; (2) connectivity would improve information flows and relationships between agents in the system, as a necessary precursor for informed decision-making; and (3) accountability, when taken beyond simplistic notions of financial reporting, would identify power relationships across the system and indicate where agents may exercise greater influence in the system. Consideration of these principles will help promote a shift from the perspective that assumes the system to be linear and manageable from the top-down to a perspective that embraces the notion of adaptive governance as a means of recognising the capacity of agents to influence the system that they inhabit.  相似文献   

Towards ground truthing exploration in the central Arctic Ocean: a Cenozoic compaction history from the Lomonosov Ridge     

M. O'Regan  K. Moran  C. D. P. Baxter  J. Cartwright  C. Vogt  M. Kölling 《Basin Research》2010,22(2):215-235

The Integrated Ocean Drilling Program's Expedition 302, the Arctic Coring Expedition (ACEX), recovered the first Cenozoic sedimentary sequence from the central Arctic Ocean. ACEX provided ground truth for basin scale geophysical interpretations and for guiding future exploration targets in this largely unexplored ocean basin. Here, we present results from a series of consolidation tests used to characterize sediment compressibility and permeability and integrate these with high‐resolution measurements of bulk density, porosity and shear strength to investigate the stress history and the nature of prominent lithostratigraphic and seismostratigraphic boundaries in the ACEX record. Despite moderate sedimentation rates (10–30 m Myr^?1) and high permeability values (10^?15–10^?18 m²), consolidation and shear strength measurements both suggest an overall state of underconsolidation or overpressure. One‐dimensional compaction modelling shows that to maintain such excess pore pressures, an in situ fluid source is required that exceeds the rate of fluid expulsion generated by mechanical compaction alone. Geochemical and sedimentological evidence is presented that identifies the Opal A–C/T transformation of biosiliceous rich sediments as a potential additional in situ fluid source. However, the combined rate of chemical and mechanical compaction remain too low to fully account for the observed pore pressure gradients, implying an additional diagenetic fluid source from within or below the recovered Cenozoic sediments from ACEX. Recognition of the Opal A–C/T reaction front in the ACEX record has broad reaching regional implications on slope stability and subsurface pressure evolution, and provides an important consideration for interpreting and correlating the spatially limited seismic data from the Arctic Ocean.  相似文献   

Hydrogen in the atmosphere of the evolved WN3 Wolf–Rayet star WR 3: defying an evolutionary paradigm?     

S. V. Marchenko  A. F. J. Moffat  P. A. Crowther  A.-N. Chené  M. De Serres  P. R. J. Eenens  G. M. Hill  J. Moran  T. Morel 《Monthly notices of the Royal Astronomical Society》2004,353(1):153-161

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Limb observations of the 12.32-micron Mg I emission line during the 1994 annular eclipse     

Deming  Drake  Jennings  Donald E.  McCabe  George  Moran  Thomas  Loewenstein  Robert 《Solar physics》1998,182(2):283-291

We determined the limb profile of the extremely Zeeman-sensitive emission line of Mg i at 12.32 m (811.58 cm–1) during the May 1994 annular eclipse, using the 3.5-m ARC telescope at the Apache Point site on Sacramento Peak, New Mexico. Spectra were recorded at 0.1 cm–1 spectral resolution and 1 s time resolution using a cryogenic grating spectrometer. The time derivatives of the observed line energy and continuum intensity were used to infer high-resolution profiles of the solar limb. Data were obtained at second contact only, since clouds prevented observations at third contact. We find that the emission line energy peaks very close to the 12 m continuum limb. This agrees with our result from the 1991 total eclipse over Mauna Kea, and also with non-LTE radiative transfer theory for this line, which predicts an upper-photospheric origin. However, in 1991, line emission remained observable as high as 2000 km above the continuum limb, whereas the 1994 data show observable emission to only 500 km. This difference greatly exceeds any applicable errors, or sensitivity differences in either data set, and must be attributed to spatial and/or temporal inhomogeneities in the solar limb emission of this line. We discuss possible causes of these inhomogeneities, and implications for observations at far-IR and submillimeter wavelengths.  相似文献   

Lake Winnipeg sediment physical properties: interpretation, composite stratigraphic sections and calibration of acoustic reflection profiles     

Kathryn Moran  Catherine A. Jarrett 《Journal of Paleolimnology》1998,19(3):245-253

High resolution sediment physical properties, measured on gravity and piston cores collected during cruises to Lake Winnipeg, include bulk density, acoustic velocity, magnetic susceptibility, shear strength and colour reflectance. The high resolution data are used here to construct complete stratigraphic (composite) sections of Lake Winnipeg sediments from a series of individual, discontinuous cores for the North and South Basins. These composite sections are used to evaluate basin-wide glacial and post-glacial depositional histories and to compare the northern and southern basin histories. In addition, these sections provide a baseline depth reference for interpretation of the biostratigraphy, paleomagnetic record and rock magnetic stratigraphy. Some of the data (density and shear strength) are also be used to estimate sediment stress history for the two major lithostratigraphic units and their variations across the basin.  相似文献   

Comparison of biomass and size spectra derived from optical plankton counter data and net samples: application to the assessment of mesoplankton distribution along the Northwest and North Iberian Shelf   总被引：1，自引：0，他引：1  

Nogueira  Enrique; Gonzalez-Nuevo  Gonzalo; Bode  Antonio; Varela  Manuel; Moran  Xose Anxelu G; Valdes  Luis 《ICES Journal of Marine Science》2004,61(4):508-517

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Creep deformation of slope sediments in the Canadian Beaufort Sea   总被引：1，自引：0，他引：1  

P. R. Hill  K. M. Moran  S. M. Blasco 《Geo-Marine Letters》1982,2(3-4):163-170

High resolution seismic profiles from the Canadian Beaufort Sea continental slope characteristically show a surficial 50 m thick conformably stratified unit overlying an irregular erosion surface. This stratified unit appears to be compressionally folded and associated with minor faults. At the shelf break, there are numerous indicators of a tensional regime, such as a large, slope-parallel graben and numerous mud diapirs. Although a large-scale slide-scar was mapped in one area, most of the slope is interpreted to be deforming by a creep mechanism. Preliminary calculations can provide reasonable values for the fold wave length and rate of deformation, supporting the suggestion that time dependent creep deformation has occurred in this area.  相似文献   

Detection of rapid deposition of sea ice-rafted material to the Arctic Ocean benthos using the cosmogenic tracer Be     

Lee W. Cooper  Ingvar L. Larsen  Jacqueline M. Grebmeier  S. Bradley Moran 《Deep Sea Research Part II: Topical Studies in Oceanography》2005,52(24-26):3452

During three icebreaker cruises in the Arctic Ocean under different sea-ice conditions in 2002, undisturbed benthic surface sediments were collected and assayed for the presence of a short-lived (t_1/2=53 d), particle-reactive cosmogenic radionuclide, ⁷Be, that is solely derived from atmospheric deposition. Under largely ice-covered conditions in May–June 2002, we did not detect this radionuclide in benthic surface sediments, despite significant inventories present in ice-rafted snow on the overlying sea ice (mean=86.8 Bq m⁻²±32.0 SD; n=9). During the July–August 2002 Shelf–Basin Interactions (SBI) cruise aboard the USCGC Healy and during a simultaneous cruise of the CCGS Sir Wilfrid Laurier on the Bering and Chukchi Shelf, which occupied the same general region following retreat and dissolution of Arctic ice cover, the ⁷Be present in this snow as well as surface deposition on to the sea ice-free water surface was detected in many benthic surface sediments, including some as deep as 945 m in Barrow Canyon. Inventories of ⁷Be in sediments were as high (60 Bq m⁻²) as the entire decay-corrected inventory present earlier in some snow samples collected on the sea-ice cover. Other deposition indicators such as the inventories of sediment chlorophyll, sediment oxygen respiration rates and ²³⁴Th-derived export fluxes also showed post-ice melt particle deposition and vertical transport, but in most cases the ⁷Be deposition was not tightly correlated with these other indicators, suggesting that ⁷Be sedimentation may not be controlled by the same processes. Our observations indicate that materials in sea ice, including contaminants, particulate organic, and mineral matter originating from atmospheric deposition or entrained in continental shelf sediments and rafted onto sea ice, can be rapidly transported to depth. The re-distribution of these materials as sea-ice drifts and eventually melts has the potential for impacting Arctic Ocean biogeochemical cycles and contaminant concentrations in areas of the Arctic remote from the original point of deposition.  相似文献