The efficacy of riparian tree cover as a climate change adaptation tool is affected by hydromorphological alterations     

Rossa O'Briain  Samuel Shephard  Ronan Matson  Paul Gordon  Fiona L. Kelly 《水文研究》2020,34(11):2433-2449

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Interannual variability of Pacific Winter Water inflow through Barrow Canyon from 2000 to 2006   总被引：2，自引：0，他引：2  

Motoyo Itoh  Koji Shimada  Takashi Kamoshida  Fiona McLaughlin  Eddy Carmack  Shigeto Nishino 《Journal of Oceanography》2012,68(4):575-592

We examined the interannual variability of Pacific Winter Water (PWW), both upstream in the northeastern Chukchi Sea and Barrow Canyon using mooring observations from 2000 to 2006, and downstream in the Canada Basin using hydrographic data acquired in 2002–2006. The interannual variation of PWW salinity is governed by two factors: (1) variability in the salinity of Pacific Water that flows northward through Bering Strait in winter; and (2) the input of salt associated with sea ice formation during winter in an intermittent coastal polynya located along the Alaskan coast between Cape Lisburne and Point Barrow. During the winters of 2000/2001 and 2001/2002 an increased transport of cold and saline PWW (S?>?33.5) to the basin via Barrow Canyon was observed. In 2000/2001 enhanced ice formation in the polynya contributed to the increased salinity of PWW, whereas in 2001/2002 the salinity of water entering through the Bering Strait was higher, and this resulted in more saline PWW being delivered to the basin. In the following four winters (2002/2003, 2003/2004, 2004/2005 and 2005/2006) the transport of cold and saline PWW in winter to the basin was less than that in the two preceding winters. In three of these four winters (2003/2004 being the exception) the coastal polynya was less active, thus reducing the input of salt due to brine enrichment. In the winter of 2003/2004, however, warmer water within the polynya region constrained ice formation and thus less cold and saline PWW was produced, despite the fact that the coastal polynya was active and frequently open.  相似文献   

Sources of Error Model and Progress Metrics for Acoustic/Infrasonic Analysis: Location Estimation     

Stephen Arrowsmith  David Norris  Rod Whitaker  Dale Anderson 《Pure and Applied Geophysics》2014,171(3-5):587-597

How well can we locate events using infrasound? This question has obvious implications for the use of infrasound within the context of nuclear explosion monitoring, and can be used to inform decision makers on the capability and limitations of infrasound as a sensing modality. This paper attempts to answer this question in the context of regional networks by quantifying current capability and estimating future capability using an example regional network in Utah. This example is contrasted with a sparse network over a large geographical region (representative of the IMS network). As a metric, we utilize the location precision, a measure of the total geographic area in which an event may occur at a 95 % confidence level. Our results highlight the relative importance of backazimuth and arrival time constraints under different scenarios (dense vs. sparse networks), and quantify the precision capability of the Utah network under different scenarios. The final section of this paper outlines the research and development required to achieve the estimated future location precision capability.  相似文献   

Origin of light volatile hydrocarbon gases in mud volcano fluids, Gulf of Cadiz — Evidence for multiple sources and transport mechanisms in active sedimentary wedges     

Marianne Nuzzo  Edward R.C. Hornibrook  Fiona Gill  Christian Hensen  Richard D. Pancost  Matthias Haeckel  Anja Reitz  Florian Scholz  Vitor H. Magalhes  Warner Brückmann  Luis M. Pinheiro 《Chemical Geology》2009,266(3-4):359-372

Widespread mud volcanism across the thick (≤ 14 km) seismically active sedimentary prism of the Gulf of Cadiz is driven by tectonic activity along extensive strike–slip faults and thrusts associated with the accommodation of the Africa–Eurasia convergence and building of the Arc of Gibraltar, respectively. An investigation of eleven active sites located on the Moroccan Margin and in deeper waters across the wedge showed that light volatile hydrocarbon gases vented at the mud volcanoes (MVs) have distinct, mainly thermogenic, origins. Gases of higher and lower thermal maturities are mixed at Ginsburg and Mercator MVs on the Moroccan Margin, probably because high maturity gases that are trapped beneath evaporite deposits are transported upwards at the MVs and mixed with shallower, less mature, thermogenic gases during migration. At all other sites except for the westernmost Porto MV, δ¹³C–CH₄ and δ²H–CH₄ values of ~ − 50‰ and − 200‰, respectively, suggest a common origin for methane; however, the ratio of CH₄/(C₂H₆ + C₃H₈) varies from ~ 10 to > 7000 between sites. Mixing of shallow biogenic and deep thermogenic gases cannot account for the observed compositions which instead result mainly from extensive migration of thermogenic gases in the deeply-buried sediments, possibly associated with biodegradation of C₂₊ homologues and secondary methane production at Captain Arutyunov and Carlos Ribeiro MVs. At the deep-water Bonjardim, Olenin and Carlos Ribeiro MVs, generation of C₂₊-enriched gases is probably promoted by high heat flux anomalies which have been measured in the western area of the wedge. At Porto MV, gases are highly enriched in CH₄ having δ¹³C–CH₄ ~ − 50‰, as at most sites, but markedly lower δ²H–CH₄ values < − 250‰, suggesting that it is not generated by thermal cracking of n-alkanes but rather that it has a deep Archaeal origin. The presence of petroleum-type hydrocarbons is consistent with a thermogenic origin, and at sites where CH₄ is predominant support the suggestion that gases have experienced extensive transport during which they mobilized oil from sediments ~ 2–4 km deep. These fluids then migrate into shallower, thermally immature muds, driving their mobilization and extrusion at the seafloor. At Porto MV, the limited presence of petroleum in mud breccia sediments further supports the hypothesis of a predominantly deep microbial origin of CH₄.  相似文献   

A late Pleistocene steppe bison (Bison priscus) partial carcass from Tsiigehtchic, Northwest Territories, Canada     

Grant D. Zazula  Glen MacKay  Thomas D. Andrews  Beth Shapiro  Brandon Letts  Fiona Brock 《Quaternary Science Reviews》2009,28(25-26):2734-2742

A partial steppe bison (Bison priscus) carcass was recovered at Tsiigehtchic, near the confluence of the Arctic Red and Mackenzie Rivers, Northwest Territories, Canada in September of 2007. The carcass includes a complete cranium with horn cores and sheaths, several complete post-cranial elements (many of which have some mummified soft tissue), intestines and a large piece of hide. A piece of metacarpal bone was subsampled and yielded an AMS radiocarbon age of 11,830 ± 45 ¹⁴C yr BP (OxA-18549). Mitochondrial DNA sequenced from a hair sample confirms that Tsiigehtchic steppe bison (Bison priscus) did not belong to the lineage that eventually gave rise to modern bison (Bison bison). This is the first radiocarbon dated Bison priscus in the Mackenzie River valley, and to our knowledge, the first reported Pleistocene mammal soft tissue remains from the glaciated regions of northern Canada. Investigation of the recovery site indicates that the steppe bison was released from the permafrost during a landslide within unconsolidated glacial outwash gravel. These data indicate that the lower Mackenzie River valley was ice free and inhabited by steppe bison by 11,800 ¹⁴C years ago. This date is important for the deglacial chronology of the Laurentide Ice Sheet and the opening of the northern portal to the Ice Free Corridor. The presence of steppe bison raises further potential for the discovery of more late Pleistocene fauna, and possibly archaeological evidence, in the region.  相似文献   

Square Kilometre Array: The radio telescope of the XXI century     

K. Grainge  B. Alachkar  Shaun Amy  D. Barbosa  M. Bommineni  P. Boven  R. Braddock  J. Davis  P. Diwakar  V. Francis  R. Gabrielczyk  R. Gamatham  S. Garrington  T. Gibbon  D. Gozzard  S. Gregory  Y. Guo  Y. Gupta  J. Hammond  D. Hindley  U. Horn  R. Hughes-Jones  M. Hussey  S. Lloyd  S. Mammen  S. Miteff  V. Mohile  J. Muller  S. Natarajan  J. Nicholls  R. Oberland  M. Pearson  T. Rayner  S. Schediwy  R. Schilizzi  S. Sharma  S. Stobie  M. Tearle  B. Wang  B. Wallace  L. Wang  R. Warange  R. Whitaker  A. Wilkinson  N. Wingfield 《Astronomy Reports》2017,61(4):288-296

The Square Kilometre Array (SKA) will be the world’s largest and most sensitive radio telescope. It will address fundamental unanswered questions about our Universe including how the first stars and galaxies formed after the Big Bang, how dark energy is accelerating the expansion of theUniverse, the role of magnetism in the cosmos, the nature of gravity, and the search for life beyond Earth. This project envisages the construction of 133 15-m antennas in South Africa and 131072 log-periodic antennas in Australia, together with the associated infrastructure in the two desert sites. In addition, the SKA is an exemplar Big Data project, with data rates of over 10 Tbps being transported from the telescope to HPC/HTC facilities.  相似文献   

Past major tsunamis and the level of tsunami risk on the Aitape coast of Papua New Guinea     

Davies  Hugh L.  Simeon  Oliver B.  Hope  Geoffrey  Petchey  Fiona  Davies  Jocelyn M. 《Natural Hazards》2019,96(3):1019-1040

Natural Hazards - This paper reports the results of an investigation into past major tsunamis on the Aitape coast of Papua New Guinea. The investigation was mounted to gather information to help...  相似文献   

Intensity and direction of lattice-preferred orientation of olivine: are electrical and seismic anisotropies of the Australian mantle reconcilable?     

Fiona Simpson 《Earth and Planetary Science Letters》2002,203(1):535-547

It has been hypothesised that seismic and electrical anisotropy at the base of the lithosphere are caused by strain-induced lattice-preferred orientation (LPO) of olivine [100] axes parallel to present-day plate motion. This would imply that seismic and electrical anisotropy observations can provide geodynamicists with fundamental information for characterising mantle flow. The qualitative agreement between the fast direction of SV-waves and direction of maximum electrical conductance modelled deeper than 150 km below the North Central craton of Australia appear to support a common alignment mechanism, and the observed, anisotropic electrical conductances can be generated by hydrogen diffusivity in a water-poor (<1000 ppm H/Si) olivine mantle. A quantitative test is proposed for the hypothesis that electrical anisotropy is generated by anisotropic hydrogen diffusion rates (D) in olivine. Electrical anisotropy factors are computed using random resistor network models assuming that D[100]≈20×D[010]≈40×D[001]. Electrical and seismic anisotropies calculated from olivine LPO angular distribution functions modelled for a range of shear strains under a simple shear deformation demonstrate that the intensity of olivine [100] alignments (and associated shear strains) that would be required to explain the electrical anisotropy in the mantle below central Australia are significantly greater than predicted by Rayleigh wave anisotropies. The poor agreement between the observed electrical anisotropies and the electrical anisotropies that would be predicted from the Rayleigh wave anisotropies indicates that either (i) electrical anisotropy in the upper mantle below central Australia is not generated by hydrogen diffusivity alone or (ii) the seismic anisotropy is underestimated. The orientation of the olivine [100] axes maxima is inferred to be ∼30° rotated relative to the direction of present-day absolute plate motion (APM) that is determined relative to the hotspot reference frame (HS2-NUVEL1). Both the APM direction that is determined relative to a reference frame defined by requiring no-net rotation of the lithosphere (NNR-NUVEL1) and GPS-derived plate motion vectors fit the geophysical observations of upper mantle anisotropy better. This may support the contention that hotspots are not stationary relative to the deep mantle.  相似文献   

Petrology and provenance of late silurian fluviatile sandstones from the ringerike group of Norway     

P. Turner  J.H.McD. Whitaker 《Sedimentary Geology》1976,16(1):45-68

The Ringerike Group, a late Silurian fluviatile sequence in the Oslo Graben of Norway was deposited in two distinct sedimentary provinces. In the northern part of the area the Sundvollen Formation (meandering-stream sediments) and the overlying Stubdal Formation (braided) contain antiperthitic feldspars and drop perthites characteristics of the jotunites of the Jotunheim area of central Norway. Other textural, mineralogical and palaeocurrent evidence supports the conclusion that these two formations were derived from a relatively distant source area, which included the Jotunheim, part of the newly raised Caledonian orogen.To the south, the sandstones of the Holmestrand area are much coarser grained and show a distinctive mineralogy, composition and texture. This evidence, supported by palaeocurrent studies, is consistent with a proximal source area on the eastern flank of the Oslo Graben. Source rocks consisted predominantly of high-grade metamorphic and igneous rocks of the Precambrian basement and the overlying Eocambrian sedimentary rocks.  相似文献   

The Role of non-timber forest products as safety-nets: A review of evidence with a focus on South Africa     

Fiona Paumgarten 《GeoJournal》2005,64(3):189-197

Poor, rural communities are vulnerable to adversity. To secure their livelihoods, people adopt multiple livelihood strategies, including using non-timber forest products (NTFPs). NTFPs have been identified as important to rural livelihoods, as an alternative land-use option as well as in fulfilling an important safety-net function although empirical evidence on the latter’s strength is limited. Whilst NTFPs may contribute towards alleviating poverty, this safety-net function needs more critical and quantitative investigation. This includes the establishment of an applicable definition so this function can be communicated to policy makers and taken into account in national poverty alleviation strategies and, in attempts to promote resource-conserving behaviour by highlighting the value of natural resources (including NTFPs) compared to alternative land-use options. Poverty in rural households is complex and households are vulnerable to a range of shocks. During adversity households can turn to a range of possible safety-nets. What determines the use of NTFPs as a safety-net, how this safety-net function manifests and the strength of this function is poorly understood and there is need for further investigation.  相似文献