Spring temperatures in the Sagehen Basin, Sierra Nevada, CA: implications for heat flow and groundwater circulation

Heat flow in the Sierra Nevada, CA, is low despite its young geologic age. We investigate the possibility that advective heat transport by groundwater flow leads to an underestimate of heat flow in the Sierras based purely on borehole measurements. Using temperature and discharge measurements at springs in Sagehen Basin, we find that groundwater removes the equivalent of approximately 20–40 mW m⁻² of geothermal heat from the basin. This is comparable with other heat flow measurements in the region and indicates that, in this basin, at least, groundwater does transport a significant amount of geothermal heat within the basin. Additionally, we use estimates of the mean residence time of water discharged at the springs along with hourly temperature records in springs to provide constraints on groundwater flow depths within the basin. An analytical model based on these constraints indicates that the heat removed by groundwater may represent 20% to >90% of the total heat flow in the basin. Without better constraints on the regional hydrogeology and the depth of circulation, we cannot determine whether the heat discharged at the springs represents a change in the mode of heat transfer, i.e. from conduction to advection at shallow depths (<100 m) or whether this is a component of heat transfer that should be added to measured conductive values. If the latter is true, and Sagehen Basin is representative of the Sierras, basal heat flow in the Sierra Nevada may be higher than previously thought.     

The interplay of permeability and fluid properties as a first order control of heat transport, venting temperatures and venting salinities at mid-ocean ridge hydrothermal systems

While the fundamental influence of fluid properties on venting temperatures in mid-ocean ridge (MOR) hydrothermal systems is now well established, the potential interplay of fluid properties with permeability in controlling heat transfer, venting temperatures, and venting salinities has so far received little attention. A series of numerical simulations of fully transient fluid flow in a generic, across-axis model of a MOR with a heat input equivalent to magmatic supply at a spreading rate of 10 cm year⁻¹ shows a strong dependence of venting temperature and salinity on the system's permeability. At high permeability, venting temperatures are low because fluid fluxes are so high that the basal conductive heating cannot warm the large fluid masses rapidly enough. The highest venting temperature around 400°C as well as sub-seafloor fluid phase separation occur when the permeability is just high enough that the fluid flux can still accommodate all heat input for advection, or for lower permeabilities where advection is no longer capable to transfer all incoming magmatic heat. In the latter case, additional mechanisms such as eruptions of basaltic magma may become relevant in balancing heat flow in MOR settings. The results can quantitatively be explained by the 'fluxibility' hypothesis of Jupp & Schultz (Nature, 403 , 2000, 880), which is used to derive diagrams for the relations between basal heat input, permeability and venting temperatures. Its predictive capabilities are tested against additional simulations. Potential implications of this work are that permeability in high-temperature MOR hydrothermal systems may be lower than previously thought and that low-temperature systems at high permeability may be an efficient way of removing heat at MOR.     

Evaluation of recoverable energy potential from enhanced geothermal systems: a sensitivity analysis in a poro‐thermo‐elastic framework

This study presents application of an efficient approach to simulate fluid flow and heat transfer in naturally fractured geothermal reservoirs. Fluid flow is simulated by combining single continuum and discrete fracture approaches. The local thermal nonequilibrium approach is used to simulate heat transfer by conduction in the rock matrix and convection (including conduction) in the fluid. Fluid flow and heat transfer models are integrated within a coupled poro‐thermo‐elastic framework. The developed model is used to evaluate the long‐term response of a geothermal reservoir with specific boundary conditions and injection/production schedule. A comparative study and a sensitivity analysis are carried out to evaluate the capability of the integrated approach and understand the degree by which different reservoir parameters affect thermal depletion of Soultz geothermal reservoir, respectively. Also observed, there exists an optimum fracture permeability after which the reservoir stimulation does not change the recovery factor significantly. Estimation of fluid temperature by the assumption of local thermal nonequilibrium heat transfer between the fracture fluid and the rock matrix gives fluid temperature of about 3°C less than that of estimated by thermal equilibrium heat transfer at early stage of hot water production.     

Experimental insights into alternative strategies of lithic heat treatment

Conditions in which thermal fractures occur are explored experimentally, and the results are used to assess heat treatment strategies. We conclude that no single ‘critical temperature’ for thermal fracturing or heat treatment can be specified for any particular raw material, as has so often been attempted, because threshold temperatures exist in relationship to specimen sizes. Our experiments show that smaller specimens are resilient to greater ranges of temperature fluctuations than larger ones, and that by manufacturing/selecting specimens of smaller sizes there is more potential to heat them rapidly and to higher temperatures without producing thermal fractures. We hypothesize a continuum of heat treating strategies between a ‘slow and steady’ strategy, which has overwhelmingly dominated past experimental designs, and a ‘fast’ strategy, which has received much less attention. The paper discusses the economic and technological contexts to which different heat treating strategies might be suited.     

The Role of Fire in the Life of an Adhesive

The use of fire is essential for the preparation of hafting adhesives; both are suggested to be a proxy for distinguishing the technological expertise and complex cognition among Palaeolithic populations. While use of fire has been argued to exist from about 1.0 Ma onwards, evidence for adhesives in the Palaeolithic record is rare and fragmented. In spite of the close link between fire places and adhesives, no study has ever focussed on examining the impact of heat on adhesive deposition and preservation. This paper discusses the results of a combustion experiment that was undertaken to understand the impact of heat exposure on hafting adhesives. The results have significant implications for archaeological interpretations. Deposition in or near a fire proves to severely impact the types of residues that preserve on a stone tool. The vertically transferred heat is responsible for the loss of adhesives but also for the incidental production of adhesives and their deposition on stone tools. It can be hypothesised that the rare survival of adhesives on archaeological stone tools might not only be the result of direct contact with the fire but also the result of degradation due to heat from overlying fireplaces. If we are to improve our understanding of the preservation of adhesives, it is important to unstand the taphonomic processes that affect these adhesives, in particular heat alteration.     

The Experimental Study of Palaeolithic Heat‐Treatment Technology: A Case from the Shuidonggou Rock Resources,North‐West China

The application of heat‐treatment technology on lithic raw materials is an important feature of early modern human behaviour. The evidence of heat‐treated stone artefacts discovered at Localities 2 and 12 of the Shuidonggou Late Palaeolithic site, North‐West China, provides an important example for studying this technology among ancient humans in Asia during the Late Palaeolithic. The mechanism and effects of heat treatment on raw materials and the role of this technology in producing stone tools were studied by means of a simulation experiment and related analytical methods. These facilitated an in‐depth analysis of the heat‐treatment activities of the Shuidonggou occupants and their implications for cognitive ability and survival strategies of human populations at that time.     

The ‘Sand-Bath’ and Lithic Heat Treatment in the South African Middle Stone Age: Myth or Reality?

When heat treatment of silcrete for stone knapping was first discovered in the South African Middle Stone Age (MSA), the procedure used for it was suggested to be similar to the one used for heat treatment of finer rocks in other parts of the world: slow sand-bath heating. This comparison may have been based on published data from the fields of ethnography, experimentation and archaeology, describing sand-bath like structures and processes. In this review, I discuss whether the available data from these three fields indeed justify the suggestions that sand-bath heating was used in the context of MSA silcrete heat treatment. A careful revaluation of the available data shows that, although sand-bath heating is a widely accepted procedure that is documented in other parts of the world, understanding the earliest known cases of heat treatment in the MSA calls for another technical procedure.     

The Impact of Economic Activity on Climate

The effect of human activity on climate is examined against the background of a rapid increase in the production of man-made heat, which is likely to reach a magnitude of the order of the natural radiation balance on the earth's surface. The microclimate of cities is particularly affected by the production of industrial heat and by the heating of buildings in winter. Deforestation of large areas in conjunction with the expansion of agriculture has an impact on climate. The impact of shelterbelts is analyzed in detail, together with the effect of irrigation, swamp drainage and the creation of large reservoirs.     

An Evaluation of the Territory of Moscow Oblast in Terms of Physiologic-Climatic Parameters

A regionalization of Moscow Oblast is derived from a physiologic-climatic evaluation for purposes of settlement and recreation. The evaluation is based on the frequency of occurrence of particular classes of weather through the year. The most common classes in Moscow Oblast are the 1C class (light negative heat balance), which is determined by global macrofactors and produces an undifferentiated background in the oblast, and the N class (comfortable condition of heat equilibrium) and 2C class (moderately negative heat balance), which reflect more localized factors and can be used for a differentiated evaluation of physiologic-climatic conditions. Eleven physiologic-climatic regions are delimited on the basis of the difference between the number of days with comfortable conditions (N class) and the number of moderately cold days (2C class). Optimal conditions for settlement and recreation are found south and southeast of Moscow; the most unfavorable in the low-lying swampy Dubna area, where the Moscow-Volga canal meets the Volga River.     

DETECTING AND QUANTIFYING HEAT TREATMENT OF FLINT AND OTHER SILICA ROCKS: A NEW NON‐DESTRUCTIVE METHOD APPLIED TO HEAT‐TREATED FLINT FROM THE NEOLITHIC CHASSEY CULTURE,SOUTHERN FRANCE

Heat treatment of lithic raw material is known from the Middle Stone Age to the Neolithic. These findings require archaeometric techniques and methods for detecting the heat‐induced effects within lithic artefacts. However, the existing methods are often cost‐intensive and time‐consuming, and most of them are destructive. Here, we present a new method using the infrared spectroscopic measurement of the strength of H‐bonds formed between surface silanole groups (SiOH) and H₂O molecules held in open pores of the samples. The reduction of H‐bond strength in chalcedony is shown to be strongly correlated with the loss of open pores induced by heat treatment. Hence, the method is based on measuring one of the transformations aimed for by the instigators of the heat treatment: the reduction of porosity that modifies the rock's mechanical properties. A first application to heat‐treated material from the Neolithic Chassey culture (southern France) shows that flint was heated to temperatures between 200°C and 250°C in this period. This has important implications for the study of the procedures used and the heating environments. Our new method is non‐destructive, rapid, cost‐effective and allows for detection of the used annealing temperatures.     

Computation of the zonally-averaged circulation driven by heating due to radiation and turbulence

In a zonally-averaged dynamic model the steady state circulation of the middle atmosphere between 10 and 110 km altitude has been calculated for solstice. To investigate the combined effect of turbulent heat conduction and dissipation of eddy kinetic energy on the mean circulation, the dissipative heating has been parameterized in terms of the buoyancy term modified by a residual Richardson number. It is shown that turbulence will result in net heating of the mesopause region to be consistent with a zero mass flux through a pressure surface. It is also demonstrated that the combined effect of turbulent heat conduction and dissipation can modify the mean circulation remarkably if the Richardson number is made latitude-dependent.     

Contributions of gravity waves to the momentum,heat and turbulent energy budget of the upper mesosphere and lower thermosphere

The role of gravity waves for the momentum and heat budget of the atmosphere between approximately 70 and 110 km height is considered. Parameterization schemes for vertical gravity wave diffusivity, generalized Rayleigh friction, viscous force, heat conduction and kinetic energy dissipation are reviewed. Eddy diffusion parameterization and its relation to the gravity wave approach is also discussed and it is shown that principal similarities exist in both concepts, especially when irregular (stochastic) contributions to the perturbations are modeled. Special attention is paid to the dissipation of perturbation kinetic energy and its contribution to the heat budget of the mesopause region. It is concluded that the amount of energy which can be attributed to the part of the gravity wave spectrum contributing to generalized Rayleigh friction above the mesopause is of the order of 10% of the total perturbation energy.     

The Latest Approaches and Concepts in Geography

The article discusses the present state of knowledge of the basic components of the heat balance of the earth's surface (radiation balance, loss of heat to evaporation, turbulent heat exchange) and the distribution of these components in time and space. Soviet research is concerned with applying heat-balance data to the study of physical-geographical processes (hydrologic regime, plant and soil cover), to the study of integrated geographic problems (geographic zonality) and practical problems (weather and hydrologic forecasting, the use of solar energy for productive purposes, and the use of heat-balance data for planning reclamation projects and other nature-transforming measures.)     

Testing for the presence of thermal pretreatment of flint in the mesolithic and neolithic of Sweden

Through ethnographic accounts, the method of heat treatment of silica materials to improve the flaking qualities is shown to have been known almost worldwide. Some mesolithic and neolithic flint artifacts from southern Sweden were examined in order to determine if they too were heat treated. From several methods proving or indicating thermal alteration of flint, analysis using scanning electron microscopy was chosen. Two samples were taken from each artifact, one being examined unaltered, the other being heat treated. No two samples from the same artifact had the same kind of surface appearance. Thus these analyses prove that the artifacts examined had not been heat treated.     

Spatial Analysis of the Factors Contributing to the Relationship between the Transient,Meridional Eddy Sensible,and Latent Heat Flux in the Southern Hemisphere

In this paper principal component analysis (PCA) and singular value decomposition (SVD) are used to define the importance of the variables contributing to the relationship between the transient latent and sensible heat fluxes and to show their temporal and spatial variation. SVD is offered as an alternative means of isolating spatial and temporal structures in data with the advantage that it can depict simultaneous space‐time variations that are aggregates of the results produced by PCA. Both methods of analysis produced two very important uncorrelated modes of variability in January and July, indicating that the transient heat fluxes are influenced by few controlling factors. We suggest that these modes of variability represent the influences of the meridional temperature gradient, atmospheric moisture, and activity within the source and sink regions of the transient heat fluxes. The physical relationships between the heat fluxes that appear to represented by the statistical modes of variability are discussed.     

Influence of meteorological conditions on the intensity and form of the urban heat island effect in Regina

This study investigates the influence of meteorological conditions on the intensity and spatial configuration of the urban heat island effect in Regina, Saskatchewan. A sample of 31 nocturnal heat island intensities measured via automobile surveys averages 3°C, with a maximum intensity reaching 7.5°C. On nights with clear skies and light winds, heat island morphology in Regina is characterized by a clearly defined cliff, plateau, and peak. Regression analysis reveals that heat island intensities are highly sensitive to changes in wind conditions, and relatively insensitive to changes in humidity and atmospheric pressure. However, when antecedent weather conditions preceding each heat island event are included in the analysis, cloud cover supersedes wind speed as a more important control on heat island intensity. Daytime and post‐sunset cloud cover explain 20 percent more variance in the ensuing nocturnal heat island intensities than do daytime and post‐sunset wind speeds. This result challenges the widely‐held notion that wind speed is a more important heat island control than sky cover. Cette étude se penche sur l'influence des conditions météorologiques sur l'intensité et la configuration spatiale de l'effet d'îlot thermique urbain à Régina, Saskatchewan. Un échantillon de 31 intensités d'îlots thermiques nocturnes prélevées par automobile atteint une moyenne de 3°C, avec une intensité maximale de 7,5°C. Par nuit claire et vent léger, la morphologie des îlots thermiques à Régina est nettement caractérisée par un courant ascentionnel, un palier et une crête. L'analyse de régression révèle que les intensités d'îlots thermiques sont très sensibles aux changements de vents coincidents, et relativement insensibles aux changements d'humidité et de pression atmosphérique. Cependant, quand les conditions atmosphériques précédant chaque effet d'îlot thermique sont prises en considération, la couverture nuageuse supplante la vitesse du vent comme contrôle majeur de l'intensité. Quand on compare couverture nuageuse et vitesse du vent pendant la journée et après le coucher du soleil, la valeur explicative de la première est de 20 pour cent supérieure à celle de la dernière en ce qui concerne la variation d'intensité dans les îlots thermiques nocturnes qui s'ensuivent. Ce résultat remet en question la ‘conviction’ que dans le contrôle des îlots thermiques, la vitesse du vent est plus importante que la couverture nuageuse.     

Impact of transition zones, variable fluid viscosity and anthropogenic activities on coupled fluid-transport processes in a shallow salt-dome environment

In the Schleswig–Holstein region (S–H) of Germany, most observed near-surface saline ground waters originate from dissolution of shallow salt domes. Previous numerical simulations of thermohaline flow clarified the major mechanisms controlling large-scale density-driven flow. It has been found that, in addition to topographically driven flow, gravitational and thermohaline convection are the primary mechanisms for extensive solute exchange between shallow and deep aquifers. Geological features such as glacial channels control recharge/discharge processes at the surface. Here we address several previously unresolved issues: (i) the impact of a permeable unit (transition zone) between the salt and adjacent units; (ii) the role of variable brine viscosity in affecting regional- (i.e. km-) scale heat and mass patterns; and (iii) the influence of anthropogenic activities such as pumping stations on density-driven flow. We found that geophysical factors play a major role in determining the dynamics of fluid processes. The transition zone significantly influences the flow field and the distribution of heat, slowing the formation of highly concentrated salty plumes. The impact of variable fluid viscosity on the coupled heat and brine flow is twofold. In a colder and highly concentrated environment, such as a shallow salt-dome crest, it retards brine flow. In a less saline environment, variable fluid viscosity enhances thermally induced upward fluid flow. Groundwater extraction from production wells only affects brine and heat flow locally within the upper aquifers.     

The Heat Balance and Radiation Regime of Corn Crops

The authors derive the components of the radiation balance of a corn crop either by direct observation or by computational methods. These components include the heat circulating in the soil and in the corn plant cover, and the turbulent heat exchange between the corn crop and the atmosphere.     

The Enlightenment,Pyropolitics, and the Problem of Evil

Abstract

In this article I argue that the ideal of rationality espoused by the European Enlightenment hinges on the separation of the light of reason from heat, with which it had been conjoined in the classical element of fire at least since the Greek antiquity. As a result, evil, from the standpoint of the Enlightenment is tantamount to heat without light, while evil, critically viewed outside this tradition, inheres in the absolute separation between the two aspects of the life-giving, albeit ineluctably dangerous, fire.     

The Interaction of Elements in the System “Ocean—Atmosphere—Continents”

A Soviet geophysicist, who has been specializing in physics of the sea, reviews his own recent work on the Atlantic sources of heat that reach the Soviet Union, particularly its European part. One-fourth of the total amount of heat is found to originate in an area of the northeast Atlantic, off Scandinavia, where temperature isanomals are at a maximum. Three-fourths are said to originate in an area of cyclic currents coinciding roughly with the North American Basin of the West Atlantic. The author also uses simple algebraic equations to calculate the parameters of a tropical hurricane, and finds a relationship between the surface-water temperature and the power of the hurricane.