The role of forcing and internal dynamics in explaining the “Medieval Climate Anomaly”     

Hugues Goosse  Elisabeth Crespin  Svetlana Dubinkina  Marie-France Loutre  Michael E. Mann  Hans Renssen  Yoann Sallaz-Damaz  Drew Shindell 《Climate Dynamics》2012,39(12):2847-2866

Proxy reconstructions suggest that peak global temperature during the past warm interval known as the Medieval Climate Anomaly (MCA, roughly 950–1250 AD) has been exceeded only during the most recent decades. To better understand the origin of this warm period, we use model simulations constrained by data assimilation establishing the spatial pattern of temperature changes that is most consistent with forcing estimates, model physics and the empirical information contained in paleoclimate proxy records. These numerical experiments demonstrate that the reconstructed spatial temperature pattern of the MCA can be explained by a simple thermodynamical response of the climate system to relatively weak changes in radiative forcing combined with a modification of the atmospheric circulation, displaying some similarities with the positive phase of the so-called Arctic Oscillation, and with northward shifts in the position of the Gulf Stream and Kuroshio currents. The mechanisms underlying the MCA are thus quite different from anthropogenic mechanisms responsible for modern global warming.  相似文献   

Mobility and exile at 2nd century A.D. khirbet edh‐dharih: Strontium isotope analysis of human migration in western Jordan     

Megan A. Perry  Drew Coleman  Nathalie Delhopital 《Geoarchaeology》2008,23(4):528-549

The 2nd century A.D. Roman annexation of the Nabataean Kingdom may have resulted in significant settlement disruption. Here we investigate the possibility that political refugees occupied Khirbet edh‐Dharih after Roman takeover, using strontium isotope analysis of archaeological human dental enamel. We additionally discuss regional patterning of 87Sr/86Sr in western Jordan based on archaeological faunal dental enamel samples to understand strontium isotope spatial heterogeneity and to facilitate interpretation of the Dharih results. Strontium isotope analysis of small mammal dentition varied as expected based on bedrock geology, but small faunal sample sizes did not accurately reflect the broad range of biologically available strontium at Dharih. Only one person at Khirbet edh‐Dharh appears to be non‐local based on isotopic data. The status of the remaining individuals is unclear, as they could have originated from Dharih or the Nabataean capital city of Petra. Incorporating modern fauna and soil samples to establish the local value may assist in characterizing the local strontium in a geologically complex area such as Dharih. Futhermore, future analysis of elemental strontium to assess dietary composition and diagenetic contamination would facilitate interpretation of the strontium sources in the Dharih individuals. © 2008 Wiley Periodicals, Inc.  相似文献   

Approaches to large-scale assessments     

Lawrence J. Drew 《Natural Resources Research》1996,5(2):81-84

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Initial yield to depth relation for water wells drilled into crystalline bedrock--Pinardville quadrangle, New Hampshire     

Drew LJ  Schuenemeyer JH  Armstrong TR  Sutphin DM 《Ground water》2001,39(5):676-684

A model is proposed to explain the statistical relations between the mean initial water well yields from eight time increments from 1984 to 1998 for wells drilled into the crystalline bedrock aquifer system in the Pinardville area of southern New Hampshire and the type of bedrock, mean well depth, and mean well elevation. Statistical analyses show that the mean total yield of drilling increments is positively correlated with mean total well depth and mean well elevation. In addition, the mean total well yield varies with rock type from a minimum of 46.9 L/min (12.4 gpm) in the Damon Pond granite to a maximum of 74.5 L/min (19.7 gpm) in the Permian pegmatite and granite unit. Across the eight drilling increments that comprise 211 wells each, the percentages of very low-yield wells (1.9 L/min [0.5 gpm] or less) and high-yield wells (151.4 L/min [40 gpm] or more) increased, and those of intermediate-yield wells decreased. As housing development progressed during the 1984 to 1998 interval, the mean depth of the wells and their elevations increased, and the mix of percentages of the bedrock types drilled changed markedly. The proposed model uses a feed-forward mechanism to explain the interaction between the increasing mean elevation, mean well depth, and percentages of very low-yielding wells and the mean well yield. The increasing percentages of very low-yielding wells through time and the economics of the housing market may control the system that forces the mean well depths, percentages of high-yield wells, and mean well yields to increase. The reason for the increasing percentages of very low-yield wells is uncertain, but the explanation is believed to involve the complex structural geology and tectonic history of the Pinardville quadrangle.  相似文献   

Lisdoonvarna springs and spa wells,County Clare,Ireland     

D. Drew 《Environmental Geology》1996,27(2):97-98

Lisdoonvarna is a small town with a resident population of ca. 700, which is seasonally increased several-fold by tourists. It is located in the northwest of County Clare, western Ireland about 10 km from the Atlantic seaboard and adjacent to the karstic Burren plateau. Lisdoonvarna has two claims to fame: it is the only currently operative spa in Ireland, and it is the center for a long-established match-making festival held each September (postharvest) at which bachelor farmers are found partners by skilled match-makers. These two features of Lisdoonvarna are not wholly unconnected even though the September festival now attracts many young people from outside of the area who may not patronize the spa waters.  相似文献   

Book review     

Lawrence J. Drew 《Mathematical Geology》1992,24(2):221-223

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The topographically forced component of the atmospheric motion     

Donald A. Drew 《Pure and Applied Geophysics》1976,114(3):333-344

Summary The zonally asymmetric stationary component of the general circulation is studied for small Rossby number without the beta-plane approximation. The equations for this component are linearized about a mean flow. An analytic solution for the meridional wind is found when the zonal wind and static stability of the mean flow are independent of the vertical coordinate. The solution is used to compute the transports of angular momentum and heat. The angular momentum transports give rise to a net convergence of the order of Rossby number and are balanced by the zonal mean Coriolis torque. However, the heat transports vanish at this order of magnitude.  相似文献   

A Raman spectroscopic study of arsenite and thioarsenite species in aqueous solution at 25°C     

Scott A Wood  C Drew Tait  David R Janecky 《Geochemical transactions》2002,3(1):31-9

The Raman spectra of thioarsenite and arsenite species in aqueous solution were obtained at room temperature. Solutions at constant ΣAs + ΣS of 0.1 and 0.5 mol kg^-1 were prepared with various ΣS/ΣAs ratios (0.1–9.0) and pH values (~7–13.2). Our data suggest that the speciation of As under the conditions investigated is more complicated than previously thought. The Raman measurements offer evidence for at least six separate S-bearing As species whose principal bands are centered near 365, 385, 390, 400, 415 and 420 cm^-1. The data suggest that at least two different species may give rise to bands at 385 cm^-1, bringing the probable minimum number of species to seven. Several additional species are possible but could not be resolved definitively. In general, the relative proportions of these species are dependent on total As concentration, ΣS/ΣAs ratio and pH. At very low ΣS/ΣAs ratios we also observe Raman bands attributable to the dissociation products of H₃AsO₃(aq). Although we were unable to assign precise stoichiometries for the various thioarsenite species, we were able to map out general pH and ΣS/ΣAs conditions under which the various thioarsenite and arsenite species are predominant. This study provides a basis for more detailed Raman spectroscopic and other types of investigations of the nature of thioarsenite species.  相似文献   

Experimental study of neptunyl adsorption onto Bacillus subtilis     

D. Gorman-Lewis  J.B. Fein  M.P. Jensen 《Geochimica et cosmochimica acta》2005,69(20):4837-4844

The subsurface mobility of Np is difficult to predict in part due to uncertainties associated with its sorption behavior in geologic systems. In this study, we measured Np adsorption onto a common gram-positive soil bacterium, Bacillus subtilis. We performed batch adsorption experiments with Np(V) solutions as a function of pH, from 2.5 to 8, as a function of total Np concentration from 1.29 × 10⁻⁵ M to 2.57 × 10⁻⁴ M, and as a function of ionic strength from 0.001 to 0.5 M NaClO₄. Under most pH conditions, Np adsorption is reversible and exhibits an inverse relationship with ionic strength, with adsorption increasing with increasing pH. At low pH in the 0.1 M ionic strength systems, we observed irreversible adsorption, which is consistent with reduction of Np(V) to Np(IV). We model the adsorption reaction using a nonelectrostatic surface complexation approach to yield ionic strength dependent NpO₂⁺-bacterial surface stability constants. The data require two bacterial surface complexation reactions to account for the observed adsorption behavior: R-L₁⁻ + NpO₂⁺ ↔ R-L₁-NpO₂^° and R-L₂⁻ + NpO₂⁺ ↔ R-L₂-NpO₂^°, where R represents the bacterium to which each functional group is attached, and L₁ and L₂ represent the first and second of four discrete site types on the bacterial surface. Stability constants (log K values) for the L₁ and L₂ reactions in the 0.001 M system are 2.3 ± 0.3 and 2.3 ± 0.2, and in the 0.1 M system the values are 1.7 ± 0.2 and 1.6 ± 0.2, respectively. The calculated neptunyl-bacterial surface stability constants are not consistent with values predicted using the linear free energy correlation approach from Fein et al. (2001), suggesting that possible unfavorable steric interactions and the low charge of NpO₂⁺ affects Np-bacterial adsorption.  相似文献   

Memorial to John C. Griffiths 1912–1992     

Lawrence J. Drew 《Mathematical Geosciences》1993,25(3):421-424

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