Trends in marine climate change research in the Nordic region since the first IPCC report     

M. W. Pedersen  A. Kokkalis  H. Bardarson  S. Bonanomi  W. J. Boonstra  W. E. Butler  F. K. Diekert  N. Fouzai  M. Holma  R. E. Holt  K. Ø. Kvile  E. Nieminen  K. M. Ottosen  A. Richter  L. A. Rogers  G. Romagnoni  M. Snickars  A. Törnroos  B. Weigel  J. D. Whittington  P. Woods  J. Yletyinen  A. S. A. Ferreira 《Climatic change》2016,134(1-2):147-161

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Assessment of interpolated ERA-40 reanalysis temperature and precipitation against observations of the Balkan Peninsula   总被引：1，自引：1，他引：0  

Effie Kostopoulou  Christos Giannakopoulos  Tom Holt  Philippe Le Sager 《Theoretical and Applied Climatology》2010,102(1-2):115-124

Due to their ready availability and temporal and spatial consistency, reanalysis data are widely used within the climate community. Nevertheless, higher spatial resolutions are often required and statistical interpolation techniques are applied to increase the data resolution. This work aims to derive a set of high spatial resolution data through three-dimensional interpolation of daily temperature and precipitation. Thin plate spline interpolation has been chosen and used to interpolate ERA-40 temperature and precipitation from a coarse grid (110 km) into a finer one of 1-km spatial resolution. The study evaluates the method by comparing the simulated variables with available in situ meteorological measurements. The chosen stations are distributed over the study region and, most importantly, contain information from a range of altitudes. The results indicate that accounting for the topography in the interpolation process improves the comparisons, with the biggest improvements being evident in the most mountainous areas. The method is found to be better in estimating temperature than precipitation fields. Moreover, the method performs better for maximum temperature in high altitudes and for minimum temperature in low altitudes.  相似文献   

18O/16O studies of fossil fissure fumaroles from the Valley of Ten Thousand Smokes, Alaska     

Elizabeth Warner Holt  Hugh P. Taylor 《Bulletin of Volcanology》2001,63(2-3):151-163

At three sample sites where there are good exposures of the upper 15 m of the 1912 ash-flow sheet in the Valley of Ten Thousand Smokes (VTTS), Alaska, ¹⁸O/¹⁶O studies indicate that fumarolic activity produced a very wide range of δ¹⁸O values (?0.1 to +12.6; n=32) in the groundmass adjacent to fossil fissure fumaroles. This contrasts sharply with the uniformity of δ¹⁸O in the groundmass away from fumarolic conduits (δ¹⁸O=+5.9 to +7.1; n=7) and in all of the feldspar phenocrysts (δ¹⁸O=+6.11 to +7.5 1 for 11 samples from this study and Hildreth 1987), independent of whether these were collected from fossil fumaroles or from unaltered tuff. Only one sample contained feldspars that were even slightly ¹⁸O-enriched relative to the others (cloudy plagioclase δ¹⁸O=+8.45). and this sample also contained the most ¹⁸0-enriched groundmass of any of those analyzed (δ¹⁸O=+12.6). This preservation of primary magmatic δ¹⁸O values in the VTTS feldspar phenocrysts is clearly a consequence of the extremely short time span (i.e., 1912 to ≈1923) of vigorous, high-temperature, fumarolic activity in the 1912 ash-flow sheet. These ¹⁸O/^l6O systematica are strikingly similar to those discovered in the 2.8-Ma intracaldera Chegem Tuff (Gazis et al. 1996) and in the fossil fumaroles in the outflow sheet of the 0.76 Ma Bishop Tuff (Holt and Taylor 1998), thus confirming that a similar type of fumarolic meteoric-hydro-thermal activity occurred above the zone of intense welding in all three of these ash-flow tuffs. This is particularly important, because it provides a direct linkage between the older tuffs and the actual observations at the VTTS of steam chemistry, water/rock interaction, circulation geometry, flow velocities, and fumarolic temperatures (up to 645°C). The ¹⁸O/^l6O effects in the VTTS can all be explained in terms of a two-stage history: (a) an early, 10- to 15-year-long, high-temperature (τ;450°C), fumarolic ¹⁸O-depletion event (groundmass δ¹⁸O=?0.1 to +4.8); and (b) a subsequent, much longer-lived, low-temperature (<150°C), ¹⁸O-enrichment episode (groundmass as high as δ¹⁸O=+12.6). Steam in these low-temperature fumaroles probably passed through various parts of the same hydrothermal system associated with the earlier, higher-temperature, fumarolic activity, and a weakened form of this low-temperature hydrothermal circulation continues to the present day (Keith et al. 1992; Lowell and Keith 1991). This low-temperature ¹⁸O/¹⁶O exchange probably occurred in combination with mineralogical alteration of both the groundmass and the calcium-rich portions of feldspar phenocrysts during the waning (<150°C) stages of fumarolic activity (Spilde et al. 1993). The slight ¹⁸O enrichment of apparently pristine, transparent feldspar phenocrysts (δ¹⁸O=+7.51) in one of the ¹⁸O-depleted, meteoric-hydrothermally altered fumarolic samples (whole-rock δ¹⁸O=+4.8) probably indicates that this sample was incipiently altered at low temperatures as fumarolic activity waned, and thus may have had a whole-rock δ¹⁸O value much lower than +4.87‰ prior to 1923.  相似文献   

Water Resources Planning - by Andrew A Dzurik     

Christopher  Holt 《The Geographical journal》2007,173(1):93-93

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Distributed deformation in the subducting lithosphere at Tonga     

Sarah Nothard  John Haines  James Jackson  Bill Holt 《Geophysical Journal International》1996,127(2):328-338

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Linking teaching and research in undergraduate physical geography papers: The role of fieldwork     

Ian Fuller  Martin Brook  Kat Holt 《New Zealand geographer》2010,66(3):196-202

Undergraduate teaching should be informed by research. The extent to which this is the case and how this is best practised is the subject of this paper. Learning strategies that seek to embed research within the undergraduate programme from an introductory level are discussed. The degree of success in these strategies is informed by input from postgraduate students who have ‘come through the ranks’. Their views, obtained via a focus group, suggest that research is rigorously embedded at every level of the programme and is most clearly linked to teaching in research-based third-year papers with a strong fieldwork component.  相似文献   

Modelling the tidal mixing fronts and seasonal stratification of the Northwest European Continental shelf     

Jason Holt  Lars Umlauf 《Continental Shelf Research》2008

We investigate mixing processes under stratified conditions on the Northwest European Continental shelf using a numerical model (POLCOMS). Our results indicate that convection induced by vertical shearing of horizontal density gradients (‘shear-induced convection’) is a regularly occurring feature in the bottom and surface boundary layers in this open shelf-sea situation. Two types of turbulence models are investigated to study their capability for reproducing the observed location of tidal mixing fronts, and the physical processes occurring in seasonally stratified waters. The first model is a one-equation variant of the Mellor–Yamada model, whereas the second model combines a more recent second-momentum closure with a two-equation model. It is found that generally mean frontal positions (as estimated from ICES data) are predicted more accurately by the two-equation model. The one-equation model reproduces the mean frontal locations to 18.1 km (<3 grid spacings) and the two-equation model to 17.1 km; although in the Celtic Sea the accuracy is ∼33 and ∼12 km, respectively. Comparison with historical tide gauges, current metres, CTD stations, and thermistor chain data from the North Sea Project all show an improvement in accuracy when the two-equation model is used. This is particularly apparent in the model's ability to reproduce the spring–neap variability during stratification. We find that in the presence of shear-induced convection the routinely applied clipping of the turbulent length-scale, previously thought to be a minor ingredient in a turbulence model, has a dramatic effect on the results: if the length-scale clipping is not applied, substantial over-mixing is observed to occur. The causes and possible remedies of this effect are investigated. Overall our results demonstrate a sensitivity to the details of the turbulence model that is significantly greater than previously thought.  相似文献   

Diverse young stellar populations in the intermediate-redshift radio galaxies 3C 213.1 and 3C 459: implications for the evolution of the host galaxies     

K. A. Wills  C. Tadhunter  J. Holt  R. González Delgado  K. J. Inskip  J. Rodríguez Zaurín  R. Morganti 《Monthly notices of the Royal Astronomical Society》2008,385(1):136-146

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A sample of radio-loud QSOs at redshift ∼ 4     

J. Holt  C. R. Benn  M. Vigotti  M. Pedani  R. Carballo  J. I. González-Serrano  K.-H. Mack  B. García 《Monthly notices of the Royal Astronomical Society》2004,348(3):857-865

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Community structure of macrozooplankton in Trinity and Upper Galveston Bays     

Joan Holt  Kirk Strawn 《Estuaries and Coasts》1983,6(1):66-75

Macrozooplankton were sampled bi-weekly from October 1969 through May 1973 at 16 stations. Hydrological measurements, including water temperature and conductivity, accompanied each biological sample. Sampling sites and species were grouped by cluster analysis using Camberra-Metric measure of dissimilarity and flexible sorting. Two major seasons, based on taxon composition and abundance, were identified: A warm season (average water temperature above 22°C) dominated by larval and juvenile crustaceans, and a cool season with an abundance of larval fishes. Sites were more similar to each other within a year than they were between years. Differences between years correlated with variations in salinity and temperature. Community structure indices (Shannon-Weaver diversity, species richness and “evenness”) were applied to the seasonal data. Shannon diversity and “evenness” were positively correlated with each other, but richness values were often negatively correlated with the other two indices.  相似文献