Climate Change Impacts for the Conterminous USA: An Integrated Assessment

Here we simulate dryland agriculture in the United States in order to assess potential future agricultural production under a set of general circulation model (GCM)-based climate change scenarios. The total national production of three major grain crops—corn, soybeans, and winter wheat—and two forage crops—alfalfa and clover hay—is calculated for the actual present day core production area (CPA) of each of these crops. In general, higher global mean temperature (GMT) reduces production and higher atmospheric carbon dioxide concentration ([CO₂]) increases production. Depending on the climatic change scenarios employed overall national production of the crops studied changes by up to plus or minus 25% from present-day levels. Impacts are more significant regionally, with crop production varying by greater than ±50% from baseline levels. Analysis of currently possible production areas (CPPAs) for each crop indicates that the regions most likely to be affected by climate change are those on the margins of the areas in which they are currently grown. Crop yield variability was found to be primarily influenced by local weather and geographic features rather than by large-scale changes in climate patterns and atmospheric composition. Future US agronomic potential will be significantly affected by the changes in climate projected here. The nature of the crop response will depend primarily on to what extent precipitation patterns change and also on the degree of warming experienced.     

Climate Change Impacts on the Potential Productivity of Corn and Winter Wheat in Their Primary United States Growing Regions

We calculate the impacts of climate effects inferred from three atmospheric general circulation models (GCMs) at three levels of climate change severity associated with change in global mean temperature (GMT) of 1.0, 2.5 and 5.0 °C and three levels of atmospheric CO2 concentration ([CO2]) – 365 (no CO2 fertilization effect), 560 and 750 ppm – on the potential production of dryland winter wheat (Triticum aestivum L.) and corn (Zea mays L.) for the primary (current) U.S. growing regions of each crop. This analysis is a subset of the Global Change Assessment Model (GCAM) which has the goal of integrating the linkages and feedbacks among human activities and resulting greenhouse gas emissions, changes in atmospheric composition and resulting climate change, and impacts on terrestrial systems. A set of representative farms was designed for each of the primary production regions studied and the Erosion Productivity Impact Calculator (EPIC) was used to simulate crop response to climate change. The GCMs applied were the Goddard Institute of Space Studies (GISS), the United Kingdom Meteorological Transient (UKTR) and the Australian Bureau of Meteorological Research Center (BMRC), each regionalized by means of a scenario generator (SCENGEN). The GISS scenarios have the least impact on corn and wheat production, reducing national potential production for corn by 6% and wheat by 7% at a GMT of 2.5 °C and no CO2 fertilization effect; the UKTR scenario had the most severe impact on wheat, reducing production by 18% under the same conditions; BMRC had the greatest negative impact on corn, reducing production by 20%. A GMT increase of 1.0°C marginally decreased corn and wheat production. Increasing GMT had a detrimental impact on both corn and wheat production, with wheat production suffering the greatest losses. Decreases for wheat production at GMT 5.0 and [CO2] = 365 ppm range from 36% for the GISS to 76% for the UKTR scenario. Increases in atmospheric [CO2] had a positive impact on both corn and wheat production. AT GMT 1.0, an increase in [CO2] to 560 ppm resulted in a net increase in corn and wheat production above baseline levels (from 18 to 29% for wheat and 2 to 5% for corn). Increases in [CO2] help to offset yield reductions at higher GMT levels; in most cases, however, these increases are not sufficient to return crop production to baseline levels.     

An Analytic Model For A Mantle Plume Fed By A Boundary Layer

Summary. An approximate analytical solution for flow in a mantle plume of constant radius, viscosity, and density contrast is obtained in cylindrical coordinates. the differential equations for vertical velocity of the mantle surrounding the plume and for topography are homologous to the equation for flexure of an elastic plate. Although the model is too simple to be fully applicable to the Earth, one can conclude that the vertical velocity in the mantle changes significantly away from plumes, that the viscosity of the plume is important for controlling flow rate, and that the long-wavelength geoid anomalies are sensitive to the viscosity of the surrounding mantle. the first induced upwelling away from a plume is quite weak and unlikely to control the spacing of plumes.     

Quantifying chemical changes in hydrothermally altered volcanic sequences — silica enrichment as a guide to the crandon massive sulfide deposit,Wisconsin, U.S.A.

A multi-element geochemical study of the wallrocks which host the large Precambrian Crandon deposit (≈ 70 million tons of zinc, copper ore) in Wisconsin, U.S.A. was carried out to identify pathfinder elements which significantly enlarge the size of the deposit as an exploration target. The Crandon deposit occurs in what appears to be a “normal”, subalkaline, intermediate to felsic volcanic sequence. The silica concentration of the wallrocks shows neither a systematic relationship to volcanic stratigraphy nor a distinctive pattern around ore.To determine if silica has been added to the host rocks, a regression analysis was performed on published data from 496 unaltered, subalkaline volcanic rocks from the Abitibi Subprovince of Canada, with silica as the dependent variable and the ratio of “immobile” elements Zr/TiO₂ as the independent variable. Based on the second degree regression curve and the associated standard error of estimate, predicted and residual silica values were calculated and plotted for the Crandon host rocks.The results show that massive sulfide ore was deposited in andesitic rocks with an original SiO₂ content of 52–62%, and that more than 7.4% SiO₂ was added to the rocks stratigraphically beneath the deposit and on strike with the deposit. Silica was added to the hanging wall rocks also, which confirms that hydrothermal activity at Crandon continued after cessation of massive sulfide ore deposition. In contrast to the pattern of silica enrichment at Crandon which significantly enlarges the size of the exploration target, two noneconomic prospects within ten miles of Crandon contain low to moderate levels of silica enrichment and corresponding low base metal values.Silica enrichment occurs in some systems unassociated with mineralization and is therefore not a specific signature of ore-forming processes. However, from the data presented on the Crandon deposit, if silica enrichment does exist in an exploration search area, the chances of finding a massive sulfide ore deposit are improved.     

The mass of the star formed in a cloud core

The forming star grows by mass inflow from the parent cloud core, mainly through the accretion disk. However, the core matter which has not yet contracted much is seriously disturbed by the activities of the forming star. We consider mass outflow and emission of ultraviolet radiation as such activities and determine the stellar mass as a function of the physical quantities of the parent cloud core.     

The Cretaceous-Tertiary fireball layer,ejecta layer and coal seam: Platinum-group element content and mineralogy of size fractions

Abstract— Grain size separates of the Cretaceous-Tertiary (K-T) fireball layer at marine sites and the entire K-T boundary interval at nonmarine sites (fireball layer, ejecta layer, coal seam) were analysed for platinum-group elements (PGE: Ru, Ir, Ft, Pd, Rh) and Au using inductively coupled plasma mass-spectrometry. X-ray diffractometry and scanning electron microscopy were performed on each fraction to establish the mineralogy. It was determined that the most abundant minerals in the finest fraction were a smectite-group mineral at marine K-T sites and illite-smectite mixed layer clay at nonmarine K-T sites. Positive correlation of PGE content and mineralogy indicates that the PGE are presently associated with these clay minerals which were likely formed by alteration of a condensed mafic phase (e.g., olivine or pyroxene). The correlation of clay mineral abundance with PGE content is imperfect because not all of the clay minerals in the fireball layer are derived by alteration of the original condensed ejecta. In addition, undetected PGE host(s), present in trace amounts, are likely also present.     

An Overview of Surface-Based Precipitation Observations at Environment and Climate Change Canada

The objective of this paper is to provide an overview of the present status and procedures related to surface precipitation observations at Environment and Climate Change Canada (ECCC). This work was done to support the ongoing renewal of observation systems and networks at the Meteorological Service of Canada. The paper focusses on selected parameters, namely, accumulated precipitation, precipitation intensity, precipitation type, rainfall, snowfall, and radar reflectivity. Application-specific user needs and requirements are defined and captured by World Meteorological Organization (WMO) Expert Teams at the international level by Observing Systems Capability Analysis and Review (OSCAR) and WMO Integrated Global Observing System (WIGOS), and by ECCC user engagement initiatives within the Canadian context. The precipitation-related networks of ECCC are separated into those containing automatic instruments, those with human (manual) observers, and the radar network. The unique characteristics and data flow for each of these networks, the instrument and installation characteristics, processing steps, and limitations from observation to data distribution and storage are provided. A summary of precipitation instrument-dependent algorithms that are used in ECCC's Data Management System is provided. One outcome of the analysis is the identification of gaps in spatial coverage and data quality that are required to meet user needs. Increased availability of data, including from long-serving manual sites, and an increase in the availability of precipitation type and snowfall amount are identified as improvements that would benefit many users. Other recognized improvements for in situ networks include standardized network procedures, instrument performance adjustments, and improved and sustained access to data and metadata from internal and external networks. Specific to radar, a number of items are recognized that can improve quantitative precipitation estimates. Increased coverage for the radar network and improved methods for assessing and portraying radar data quality would benefit precipitation users.     

Seawater-like trace element signatures (REE + Y) of Eoarchaean chemical sedimentary rocks from southern West Greenland,and their corruption during high-grade metamorphism

Modern chemical sediments display a distinctive rare earth element + yttrium (REE + Y) pattern involving depleted LREE, positive La/La*_SN, Eu/Eu*_SN, and Y_SN anomalies (SN = shale normalised) that is related to precipitation from circumneutral to high pH waters with solution complexation of the REEs dominated by carbonate ions. This is often interpreted as reflecting precipitation from surface waters (usually marine). The oldest broadly accepted chemical sediments are c. 3,700 Ma amphibolite facies banded iron-formation (BIF) units in the Isua supracrustal belt, Greenland. Isua BIFs, including the BIF international reference material IF-G are generally considered to be seawater precipitates, and display these REE + Y patterns (Bolhar et al. in Earth Planet Sci Lett 222:43–60, 2004). Greenland Eoarchaean BIF metamorphosed up to granulite facies from several localities in the vicinity of Akilia (island), display REE + Y patterns identical to Isua BIF, consistent with an origin by chemical sedimentation from seawater and a paucity of clastic input. Furthermore, the much-debated magnetite-bearing siliceous unit of “earliest life” rocks (sample G91/26) from Akilia has the same REE + Y pattern. This suggests that sample G91/26 is also a chemical sediment, contrary to previous assertions (Bolhar et al. in Earth Planet Sci Lett 222:43–60, 2004), and including suggestions that the Akilia unit containing G91/26 consists entirely of silica-penetrated, metasomatised, mafic rock (Fedo and Whitehouse 2002a). Integration of our trace element data with those of Bolhar et al. (Earth Planet Sci Lett 222:43–60, 2004) demonstrates that Eoarchaean siliceous rocks in Greenland, with ages from 3.6 to 3.85 Ga, have diverse trace element signatures. There are now geographically-dispersed, widespread examples with Isua BIF-like REE + Y signatures, that are interpreted as chemically unaltered, albeit metamorphosed, chemical sediments. Other samples retain remnants of LREE depletion but are beginning to lose the distinct La, Eu and Y positive anomalies and are interpreted as metasomatised chemical sediments. Finally there are some siliceous samples with completely different trace element patterns that are interpreted as rocks of non-sedimentary origin, and include metasomatised mafic rocks. The positive La/La*_SN, Eu/Eu*_SN and Y_SN anomalies found in Isua BIFs and other Eoarchaean Greenland samples, such as G91/26 from Akilia, suggests that the processes of carbonate ion complexation controlling the REE − Y patterns were already established in the hydrosphere at the start of the sedimentary record 3,600–3,850 Ma ago. This is in accord with the presence of Eoarchaean siderite-bearing marbles of sedimentary origin, and suggests that CO₂ may have been a significant greenhouse gas at that time.     

Atmospheric Corrections Using MODTRAN for TOA and Surface BRDF Characteristics from High Resolution Spectroradiometric/ Angular Measurements from a Helicopter Platform

l. IntroductionThe cIassicaI definition of bi--directional reflectance--distribution function (BRDF) is aderivative, distribution function, relatlng the irradiance incident from one given direction tolts contribution to the radiance renected in another direct1on (N1codemus et al., l977).f r (0,, rp,; 0,, rp, )= dL, (0,, P,; 0,, 9,; E, )/ dE, (0,, 9,) [sr-- 1 ], (l)where 0 (zenith angle) and 9 (azimuth angle) together indicate a direction, the subscr1pt i indi-cates quantities associated wi…