Stable AMOC off state in an eddy-permitting coupled climate model     

J. V. Mecking  S. S. Drijfhout  L. C. Jackson  T. Graham 《Climate Dynamics》2016,47(7-8):2455-2470

  相似文献   

Assessment of the accuracy of global geodetic satellite laser ranging observations and estimated impact on ITRF scale: estimation of systematic errors in LAGEOS observations 1993–2014     

Graham Appleby  José Rodríguez  Zuheir Altamimi 《Journal of Geodesy》2016,90(12):1371-1388

  相似文献   

Defining the Potential of Nanoscale Re‐Os Isotope Systematics Using Atom Probe Microscopy          下载免费PDF全文

Luke Daly  Phil A. Bland  Svetlana Tessalina  David W. Saxey  Steven M. Reddy  Denis Fougerouse  William D.A. Rickard  Lucy V. Forman  Alexandre La Fontaine  Julie M. Cairney  Simon P. Ringer  Bruce F. Schaefer  Daniel Schwander 《Geostandards and Geoanalytical Research》2018,42(3):279-299

Atom probe microscopy (APM) is a relatively new in situ tool for measuring isotope fractions from nanoscale volumes (< 0.01 μm³). We calculate the theoretical detectable difference of an isotope ratio measurement result from APM using counting statistics of a hypothetical data set to be ± 4δ or 0.4% (2s). However, challenges associated with APM measurements (e.g., peak ranging, hydride formation and isobaric interferences), result in larger uncertainties if not properly accounted for. We evaluate these factors for Re‐Os isotope ratio measurements by comparing APM and negative thermal ionisation mass spectrometry (N‐TIMS) measurement results of pure Os, pure Re, and two synthetic Re‐Os‐bearing alloys from Schwander et al. (2015, Meteoritics and Planetary Science, 50, 893) [the original metal alloy (HSE) and alloys produced by heating HSE within silicate liquid (SYN)]. From this, we propose a current best practice for APM Re‐Os isotope ratio measurements. Using this refined approach, mean APM and N‐TIMS ¹⁸⁷Os/¹⁸⁹Os measurement results agree within 0.05% and 2s (pure Os), 0.6–2% and 2s (SYN) and 5–10% (HSE). The good agreement of N‐TIMS and APM ¹⁸⁷Os/¹⁸⁹Os measurements confirms that APM can extract robust isotope ratios. Therefore, this approach permits nanoscale isotope measurements of Os‐bearing alloys using the Re‐Os geochronometer that could not be measured by conventional measurement principles.  相似文献   

Punctuated,long-lived emplacement history of the Renard 2 kimberlite,Canada, revealed by new high precision U-Pb groundmass perovskite dating     

Ranger  Ilona M.  Heaman  Larry M.  Pearson  D. Graham  Muntener  Colleen  Zhuk  Volodymyr 《Mineralogy and Petrology》2018,112(2):639-651

Kimberlites are rare volatile-rich ultramafic magmas thought to erupt in short periods of time (<1 Myr) but there is a growing body of evidence that the emplacement history of a kimberlite can be significantly more protracted. In this study we report a detailed geochronology investigation of a single kimberlite pipe from the Renard cluster in north-central Québec. Ten new high precision ID-TIMS (isotope dilution – thermal ionization mass spectrometry) U-Pb groundmass perovskite dates from the main pipe-infilling kimberlites and several small hypabyssal kimberlites from the Renard 2 pipe indicate kimberlite magmatism lasted at least ~20 Myr. Two samples of the main pipe-infilling kimberlites yield identical weighted mean ²⁰⁶Pb/²³⁸U perovskite dates with a composite date of 643.8 ± 1.0 Myr, interpreted to be the best estimate for main pipe emplacement. In contrast, six hypabyssal kimberlite samples yielded a range of weighted mean ²⁰⁶Pb/²³⁸U perovskite dates between ~652-632 Myr. Multiple dates determined from these early-, syn- and late-stage small hypabyssal kimberlites in the Renard 2 pipe demonstrate this rock type (commonly used to date kimberlites) help to constrain the duration of kimberlite intrusion history within a pipe but do not necessarily reliably record the emplacement age of the main diatreme in the Renard cluster. Our results provide the first robust geochronological data on a single kimberlite that confirms the field relationships initially observed by Wagner (1914) and Clement (1982); the presence of antecedent (diatreme precursor) intrusions, contemporaneous (syn-diatreme) intrusions, and consequent (post-diatreme) cross-cutting intrusions. The results of this detailed U-Pb geochronology study indicate a single kimberlite pipe can record millions of years of magmatism, much longer than previously thought from the classical viewpoint of a rapid and short-duration emplacement history.

  相似文献   

Lost and abandoned nets in deep-water gillnet fisheries in the Northeast Atlantic: retrieval exercises and outcomes     

Large  Philip A.; Graham  Norman G.; Hareide  Nils-Roar; Misund  Robert; Rihan  Dominic J.; Mulligan  Myles C.; Randall  Peter J.; Peach  David J.; McMullen  Philip H.; Harlay  Xavier 《ICES Journal of Marine Science》2009,66(2):323-333

  相似文献   

Seasonality and duration in extreme value distributions of significant wave height     

Fernando J. Mndez  Melisa Menndez  Alberto Luceo  Raúl Medina  Nicholas E. Graham 《Ocean Engineering》2008,35(1):131-138

This paper presents a statistical model to characterize the long-term extreme value distribution of significant wave height, conditioning to the duration of the storm and accounting for seasonality. A time-dependent version of the peak over threshold (POT) approach is used to build the model, which is then applied to specific reanalysis time series and NOAA buoy records. The model considers the annual and semiannual cycles which are parameterized in terms of harmonic functions. The inclusion of seasonal variabilities substantially reduces the residuals of the fitted model. The information obtained in this study can be useful to design maritime works, because (a) the model improves the understanding of the variability of extreme wave climate along a year and (b) the model accounts for the duration of the storm, which is a key parameter in several formulations for rubble mound breakwater design.  相似文献   

The oxygen isotope composition of water masses within the North Sea     

Andrew J.P. Harwood  Paul F. Dennis  Alina D. Marca  Graham M. Pilling  Richard S. Millner 《Estuarine, Coastal and Shelf Science》2008

Based on measurements of the ¹⁸O isotope composition of 247 samples collected over a 3-year period we have assessed the oxygen isotope composition of water masses in the North Sea. This is the first δ¹⁸O data set that covers the entire North Sea basin. The waters lie on a mixing line: δ¹⁸O (‰_VSMOW) = −9.300 + 0.274(S) with North Atlantic sub-polar mode water (SPMW) and surface waters, and Baltic Sea water representing the saline and freshwater end members respectively. Patterns exhibited in surface and bottom water δ¹⁸O distributions are representative of the general circulation of the North Sea. Oxygen-18 enriched waters from the North Atlantic enter the North Sea between Scotland and Norway and to a lesser extent through the English Channel. In contrast, oxygen-18 depleted waters mainly inflow from the Baltic Sea, the rivers Rhine and Elbe, and to a lesser degree, the Norwegian Fjords and other river sources. Locally the δ¹⁸O–salinity relationship will be controlled by the isotopic composition of the freshwater inputs. However, the range of local freshwater compositions around the North Sea basin is too narrow to characterise the relative contributions of individual sources to the overall seawater composition. This dataset provides important information for a number of related disciplines including biogeochemical research and oceanographic studies.  相似文献   

Seasonal changes in community composition and trophic structure of fish populations of five salt marshes along the Essex coastline, United Kingdom     

Benjamin C. Green  David J. Smith  Sarah E. Earley  Leanne J. Hepburn  Graham J.C. Underwood 《Estuarine, Coastal and Shelf Science》2009,85(2):247-256

European intertidal salt marshes are important nursery sites for juvenile fish and crustaceans. Due to the increasing threat of habitat loss, the seasonal changes of salt marsh fish communities need to be understood in order to appreciate the ecological and economic importance of the saltmarsh habitat. This study was the first in Great Britain to investigate the seasonal changes of salt marsh fish communities and the variation in community structure between closely located marsh habitats. Between February 2007 and March 2008, five marshes on three estuaries of the Essex coastline were sampled using flume nets to block off intertidal creeks at high tide. Fourteen fish species were caught. The community overall was dominated by three species that made up 91.6% of the total catch: the common goby Pomatoschistus microps (46.2% of the total catch), juvenile herring Clupea harengus (24.3%), and juvenile and larval sea bass Dicentrarchus labrax (21.2%). Cluster analysis demonstrated clear seasonal patterns, with some community structures unique to specific marshes or estuaries. The marsh fish community shifts from a highly diverse community during spring, to a community dominated by D. labrax and P. microps in autumn, and low diversity during winter months. Gravimetric stomach content analysis of fish community identified three main trophic guilds; macroinvertivores, planktivores and omnivores. The macroinvertivore feeding guild contained D. labrax and P. microps, the two most frequently occurring species. This investigation demonstrates the importance of British salt marshes as nursery habitats for commercial fish species.  相似文献   

An iterative method for boundary element solution of large offshore structures using the GMRES solver   总被引：1，自引：0，他引：1  

Y. Zhao  J.M.R. Graham 《Ocean Engineering》1996,23(6):483-495

The GMRES approach is used to solve complex matrix solution arising from boundary element analysis of large offshore structures. This makes it possible to solve problems with large numbers of panels on a workstation with a much smaller memory than typical high performance computers. The speed of the solver is compatible with direct solvers when the enough RAM is available. Otherwise, an iteration procedure can be used. By using an out-of-core treatment, typical RAM requirement is reduced to a size approximately linearly proportional to the panel number n instead of being proportional to n². The code is first verified with direct solver for cases with small number of panels. The applicability to large offshore structure of the model is demonstrated for a TLP case.  相似文献   

Approaches to knowledge sharing and capacity building: The role of local information systems in marine and coastal management     

Tim Stojanovic  David R. Green  Graham Lymbery 《Ocean & Coastal Management》2010,53(12):805-815

This paper explores how coastal data and information can be mobilised in information systems and applied in coastal management. The concept of an Information System is defined and described, and the potential role of Local Information System (LIS) in integrated coastal management (ICM) is considered. Three examples, from the Severn Estuary, UK the coast of the North West of England and North Wales, and the Fal and Helford estuaries, are used to demonstrate the requirements of a LIS for coastal areas. The role of GIS as part of the solution is considered in detail. The paper demonstrates how ideas from the disciplines of information systems and information science can be practically applied in coastal areas. The findings promote a holistic approach for those involved in the development of technologies and dealing with data and information about coasts and oceans.  相似文献