Amplitude Of Temperature Change Research Articles

Temporal and spatial structure of multi-millennial temperature changes at high latitudes during the Last Interglacial

The Last Interglacial (LIG, 129–116 thousand of years BP, ka) represents a test bed for climate model feedbacks in warmer-than-present high latitude regions. However, mainly because aligning different palaeoclimatic archives and from different parts of the world is not trivial, a spatio-temporal picture of LIG temperature changes is difficult to obtain.Here, we have selected 47 polar ice core and sub-polar marine sediment records and developed a strategy to align them onto the recent AICC2012 ice core chronology. We provide the first compilation of high-latitude temperature changes across the LIG associated with a coherent temporal framework built between ice core and marine sediment records. Our new data synthesis highlights non-synchronous maximum temperature changes between the two hemispheres with the Southern Ocean and Antarctica records showing an early warming compared to North Atlantic records. We also observe warmer than present-day conditions that occur for a longer time period in southern high latitudes than in northern high latitudes. Finally, the amplitude of temperature changes at high northern latitudes is larger compared to high southern latitude temperature changes recorded at the onset and the demise of the LIG.We have also compiled four data-based time slices with temperature anomalies (compared to present-day conditions) at 115 ka, 120 ka, 125 ka and 130 ka and quantitatively estimated temperature uncertainties that include relative dating errors. This provides an improved benchmark for performing more robust model-data comparison. The surface temperature simulated by two General Circulation Models (CCSM3 and HadCM3) for 130 ka and 125 ka is compared to the corresponding time slice data synthesis. This comparison shows that the models predict warmer than present conditions earlier than documented in the North Atlantic, while neither model is able to produce the reconstructed early Southern Ocean and Antarctic warming. Our results highlight the importance of producing a sequence of time slices rather than one single time slice averaging the LIG climate conditions.

European climate change at the end of the last glaciation: chironomid–based temperature reconstruction on a conti-nental scale

In Europe climatic conditions at the end of the last ice age were affected by a number of abrupt temperatures shifts, including the rapid transitions to warmer climate at the beginning of the Lateglacial Interstadial and the Holocene, and the cooling at the start of the Younger Dryas cold period. The amplitude and spatial pattern of Lateglacial changes in temperature can provide information about the forcing factors of these climate shifts and about processes affecting the European climate system during a transition to warmer climate. However, spatially resolved datasets describing temperature change across the European continent during the Lateglacial period at centennial or higher time resolution and based on the same standardized approach are presently not available. We aim to develop such a standardized dataset based on records of past summer temperature reconstructed from fossil chironomid assemblages in lake sediments. A combination of regional calibration datasets provided the basis for a chironomidbased inference model for July air temperature that covers the range of temperatures and chironomid assemblages expected for Europe during the Lateglacial. This model, which is based on modern chironomid assemblages from 274 lakes in Norway and Switzerland and associated observed values of mean July air temperature, was then used to produce temperature records from Estonia, Denmark, Ireland, the UK, Norway, the Netherlands, southeastern France, Western Spain, Northern Italy, Switzerland, and southern Romania. Preliminary results indicate distinct variations in the amplitude of temperature changes across Europe during the Lateglacial, with stronger shifts in July air temperature reconstructed in northern parts than at localities more to the south of the continent. Future work will expand this dataset to include additional sites in the British Isles, Italy, Bulgaria and Scandinavia in order to confirm the observed spatial pattern of Lateglacial temperature changes.

Revised calibration of the MBT–CBT paleotemperature proxy based on branched tetraether membrane lipids in surface soils

The MBT–CBT proxy for the reconstruction of paleotemperatures and past soil pH is based on the distribution of branched glycerol dialkyl glycerol tetraether (brGDGT) membrane lipids. The Methylation of Branched Tetraether (MBT) and the Cyclisation of Branched Tetraether (CBT) indices were developed to quantify these distributions, and significant empirical relations between these indices and annual mean air temperature (MAT) and/or soil pH were found in a large data set of soils. In this study, we extended this soil dataset to 278 globally distributed surface soils. Of these soils, 26% contains all nine brGDGTs, while in 63% of the soils the seven most common brGDGTs were detected, and the latter were selected for calibration purposes. This resulted in new transfer functions for the reconstruction of pH based on the CBT index: pH=7.90–1.97×CBT (r2=0.70; RMSE=0.8; n=176), as well as for MAT based on the CBT index and methylation index based on the seven most abundant GDGTs (defined as MBT′): MAT=0.81–5.67×CBT+31.0×MBT′ (r2=0.59; RMSE=5.0°C; n=176). The new transfer function for MAT has a substantially lower correlation coefficient than the original equation (r2=0.77). To investigate possible improvement of the correlation, we used our extended global surface soil dataset to statistically derive the indices that best describe the relations of brGDGT composition with MAT and soil pH. These new indices, however, resulted in only a relatively minor increase in correlation coefficients, while they cannot be explained straightforwardly by physiological mechanisms. The large scatter in the calibration cannot be fully explained by local factors or by seasonality, but MAT for soils from arid regions are generally substantially (up to 20°C) underestimated, suggesting that absolute brGDGT-based temperature records for these areas should be interpreted with caution.The applicability of the new MBT′–CBT calibration function was tested using previously published MBT–CBT-derived paleotemperature records covering the last deglaciation in Central Africa and East Asia, the Eocene–Oligocene boundary and the Paleocene–Eocene thermal maximum. The results show that trends remain similar in all records, but that absolute temperature estimates and the amplitude of temperature changes are lower for most records, and generally in better agreement with independent proxy data.

Variations of the Specimen Temperature Depending on the Pattern of the Multiaxial Load – Preliminary Research

This paper provides the results of research on temperature changes of cylindrical specimens depending on the pattern of the multiaxial load. The research were made by using passive infrared thermography. It was found out that the average temperature value is significantly dependent on the plastic strain energy and that the temperature change amplitude depends on the nominal normal stress (except for torsion).

Heat and moisture transfer in fibrous thermal insulation with tight boundaries and a dynamical boundary temperature

Prefabricated, lightweight building elements are widely used in the building construction sector. Such elements consist of fibrous thermal insulation encapsulated between two metal sheets. Under various circumstances, moisture can appear in the insulation matrix. Since the temperature of the boundary metal sheets changes dynamically with meteorological conditions, heat and mass transfer between boundaries appear in this case. This paper presents a transient model of the heat and mass transfer, including the sorption and condensation processes. A numerical model considers the dynamical changing of the boundary temperatures. A parametric study considering different amplitudes of temperature change, different moisture masses and different thicknesses of the insulation matrix was made. It was found that a relatively small mass of water in the insulation matrix can result in a significantly increased average heat flux during a periodic cycle. The numerical code was verified with experiments, which showed good agreement with the numerics.

Reconstructing temperature at Egelsee, Switzerland, using North American and Swedish chironomid transfer functions: potential and pitfalls

The temperature reconstruction obtained from chironomids preserved in the sediment of Egelsee, Switzerland, was partially flawed by the low percentages of fossil taxa represented in the Swiss calibration set (Larocque-Tobler et al. 2009a). Transfer functions (TFs) from other regions, which allow a good representation of the fossil taxa (>80%), could be applied to the fossil assemblages of Egelsee. First, the validity of using two (a Swedish and a North American (NA)) TFs was tested by comparing the chironomid-inferred temperatures with instrumental data. Since good relationships (rPearson = 0.71 and 0.61, p = 0.001 for the NA and Swedish TFs, respectively) were obtained, these two models were used to reconstruct the Late Glacial and early Holocene periods at Egelsee. Reconstructions using both models showed clear cold periods during the Younger Dryas and the so-called 8,200 calibrated years BP event. However, the amplitude of changes during these periods was higher when the NA transfer function was used, probably due to the fact that 37% of the taxa in the core had temperature optima colder in the NA than in the Swedish and Swiss models. The results indicate that TFs from other regions can be applied when they are based on samples with good modern analogues, however, caution should be taken when the amplitude of temperature changes is considered.

Late Glacial and Holocene temperature changes at Egelsee, Switzerland, reconstructed using subfossil chironomids

A temperature reconstruction using chironomids was attempted at Egelsee, Switzerland, a site where pollen and macrofossil records showed a correspondence between vegetation and climatic changes inferred by other proxies in Europe. The general pattern of temperature changes inferred from chironomids during the Late Glacial [i.e. cold temperatures between ca. 16,500 and 14,800 cal BP, close to present-day temperature between 15,000 and 13,000 cal BP and colder temperatures during the Younger Dryas (YD)], and the major temperature changes of the Holocene (i.e. the Younger Dryas–Holocene transition and the Late Holocene cooling trend) at Egelsee, were mirrored in other European climate reconstructions using various proxies. However, the amplitude of temperature changes during the YD was smaller than reconstructed by other proxies at various sites, and the 8,200 years BP event was not apparent. These differences between records were probably due to the dominance of Corynocera ambigua, with percentages reaching 60% in parts of the Egelsee sequence. This taxon was not present in any of the 103 lakes used for the transfer function and its absence may have yielded less accurate inferences. Its presence in samples only associated with cold inferences at Egelsee suggests that this taxon is a cold indicator. However, it was also found in warm Danish lakes and the factors that determine the presence of C. ambigua remain unexplained. Most samples had a poor fit to temperature and instead, dissolved organic carbon seemed to be a factor influencing the chironomid assemblages during the Holocene. These results illustrate the need to better understand the ecology of chironomids and to disentangle the various factors that affect chironomid communities through time. Ultimately, such information will lead to more accurate temperature reconstructions.

Experimental investigation of cryogenic oscillating heat pipes

A novel cryogenic heat pipe, oscillating heat pipe (OHP), which consists of an 4 × 18.5 cm evaporator, a 6 × 18.5 cm condenser, and 10 cm length of adiabatic section, has been developed and experimental characterization conducted. Experimental results show that the maximum heat transport capability of the OHP reached 380 W with average temperature difference of 49 °C between the evaporator and condenser when the cryogenic OHP was charged with liquid nitrogen at 48% (v/v) and operated in a horizontal direction. The thermal resistance decreased from 0.256 to 0.112 while the heat load increased from 22.5 to 321.8 W. When the OHP was operated at a steady state and an incremental heat load was added to it, the OHP operation changed from a steady state to an unsteady state until a new steady state was reached. This process can be divided into three regions: (I) unsteady state; (II) transient state; and (III) new steady state. In the steady state, the amplitude of temperature change in the evaporator is smaller than that of the condenser while the temperature response keeps the same frequency both in the evaporator and the condenser. The experimental results also showed that the amplitude of temperature difference between the evaporator and the condenser decreased when the heat load increased.

Influence of Thermo-Dynamic Properties and Thermal Inertia of the Building Envelope on Building Cooling Load

Influence of Thermo-Dynamic Properties and Thermal Inertia of the Building Envelope on Building Cooling Load Buildings are responsible for about 30 % of the total energy consumption of Latvia. Specific heat consumption is 200-225 kWh/m2 per annum, for its part the average consumption of one household is about 1000-1200 kWh per annum. Due to increasing needs for comfort, an increase in the total area of buildings covered by glass, as well as intensified interest in establishing a good microclimate in buildings, there is also increasingly more attention paid on to the cooling load of buildings and the related heat transfer and exchange processes. Thermal inertia and the thermal mass of building envelope are main factors, which substantially influence the amplitude of changes in temperature and the period during which the internal temperature is dependant on the external temperature.

Interlaminar fatigue crack growth of cross-ply composites under thermal cycles

Abstract The fatigue growth of a fiber reinforced composite laminate was characterized under thermal cycling using a combined experimental and computational investigation. Twenty-four ply composite laminates ( [ 0 ° 12 / 90 ° 12 ] ) are fabricated with a pre-existing delamination, and subjected to thermal cycling in an environmental chamber. The large mismatch in the coefficients of thermal expansion is used to grow an interlaminar crack at the interface of the 0° and 90° laminae. This thermal fatigue crack growth behavior is investigated for different amplitudes of temperature change (ΔT = 30–140 °C). The inspection of fracture surfaces, after completion of the fatigue tests, reveals an angled or kinked crack front growth with greater propagation distances near the free-surfaces/edges. Due to the non-uniform crack growth across the specimen thickness, three-dimensional finite element analyses are performed to investigate the fatigue growth mechanisms under thermal load. From the analysis, the energy release rate as well as the mixed-mode stress intensity factors is calculated and the variations of these fracture parameters are found to be consistent with the observed crack front configuration. Using the computed results, the experimentally measured crack growth rates are also correlated with the amplitude of energy release rate, and a power law form of the fatigue law is established. The relevant coefficients as well as the threshold energy release rate are also determined. The present analysis is useful for not only understanding the fatigue delamination mechanisms under thermal cycling but also for estimating the threshold temperature variation that is needed to drive crack growth.

Spatial distribution of Pleistocene/Holocene warming amplitudes in Northern Eurasia inferred from geothermal data

Abstract. We analyze 48 geothermal estimates of Pleistocene/Holocene warming amplitudes from various locations in Greenland, Europe, Arctic regions of Western Siberia, and Yakutia. The spatial distribution of these estimates exhibits two remarkable features. (i) In Europe and part of Asia the amplitude of warming increases toward the northwest and displays clear asymmetry with respect to the North Pole. The region of maximal warming is close to the North Atlantic. A simple parametric dependence of the warming amplitudes on the distance to the warming center explains 91% of the amplitude variation. The Pleistocene/Holocene warming center is located northeast of Iceland. We claim that the Holocene warming is primarily related to the formation (or resumption) of the modern system of currents in the North Atlantic. (ii) In Arctic Asia, north of the 68-th parallel, the amplitude of temperature change sharply decreases from South to North, reaching zero and even negative values. These small or negative amplitudes could be attributed partially to a joint influence of Late Pleistocene ice sheets. Using a simple model of the temperature regime underneath the ice sheet we show that, depending on the relationship between the heat flow and the vertical ice advection velocity, the base of the glacier can either warm up or cool down. Nevertheless, we speculate that the more likely explanation of these observations are warm-water lakes thought of have formed in the Late Pleistocene by the damming of the Ob, Yenisei and Lena Rivers.

Determination of the position of a localized heat source within a chirped fibre Bragg grating using a Fourier transform technique

The ability to determine the centre position of a localized temperature change within a chirped fibre Bragg grating (CFBG) has been investigated as a function of grating strength. The intragrating sensor is based on the analysis of reflected power spectra arising from a CFBG. The technique uses a discrete Fourier transform (FFT) in which the measured spectrum of the CFBG due to a localized temperature change (heat source) was simulated using a FFT grating design model. The model operated on the reference spectrum and hypothesis temperature distributions, T(z), to generate a spectrum of a CFBG subjected to a hypothesis temperature disturbance. The simulated spectrum was fitted to the measured spectrum using a three-parameter automatic disturbance function fitting algorithm operating on position, width and amplitude of temperature change. RMS deviations to within 0.03 mm of applied values of position have been obtained.

Climatic and environmental changes at southeastern coast of Lake Biwa over past 3000 years, inferred from borehole temperature data

In order to infer past climatic change in central Japan, we measured temperatures in a borehole at the Karasuma site, on the southeastern coast of Lake Biwa, and reconstructed sediment surface temperature history during the last 3000 years. The reconstructed temperature history shows apparent Medieval Warm Period, Little Ice Age, and contemporary temperature warming. However, the large amplitude of the temperature changes up to 4–5 K cannot be explained by past climatic change only, suggesting that there was some other cause of the larger amplitude temperature changes. The onsets of temperature decrease in the late 12th century a. d. and temperature increase in the mid 17th century a. d. appear to coincide with occurrences of two destructive earthquakes (1185 and 1662 a. d.) that caused water level changes of Lake Biwa. It suggests that the reconstructed sediment surface temperature history reflects the environmental change due to tectonically induced water level changes of the lake. If the annual mean of the ground surface temperature was higher than that of the bottom water temperature in a shallow part of the lake, which is consistent with the present-day data, the large amplitude of the sediment surface temperature change may be attributed to a combined effect of past climatic and environmental changes. Thus, we suggest that the borehole temperature at the Karasuma site preserves information not only on past climate changes but also on environmental changes due to tectonically induced water level changes.

SomeConsiderations on the Rayleigh–Lamb Wave Propagation in Visco-thermoelastic Plates

The aim of present paper is to study the thermoelastic interaction in an infinite Kelvin–Voigt-type viscoelastic, thermally conducting plate. The upper and lower surfaces of the plate are subjected to stress-free/rigidly fixed, thermally insulated or isothermal boundary conditions. Coupled dynamical thermoelasticity is employed to study the problem. We derive complex secular equations for the plate in closed from and isolated mathematical conditions for symmetric and skew-symmetric wave mode propagation in completely separate terms. The results for coupled and uncoupled theories of thermoelasticity have been obtained as particular cases from the derived secular equations. In general, the obtained secular equations are complex each of these on separating real and imaginary parts leads to two real frequency equations. These equations contain complete information regarding wavenumber, phase velocity, group velocity and attenuation coefficients of different propagating modes. The regions and the corresponding forms of Rayleigh–Lamb-type secular equations have been obtained and discussed in addition to Lame modes, decoupled shear horizontal modes and thin plate results. At short wavelength limits, the secular equations for symmetric and skew-symmetric waves in stress-free insulated and stress-free isothermal plate reduce to Rayleigh surface wave frequency equations. The amplitudes of temperature and displacement components during symmetric and skew-symmetric motion of the plate have been computed and discussed. In order to illustrate and compare the theoretical results, the numerical solution is carried out for copper material by using the functional iteration method. The dispersion curves, attenuation coefficients, amplitudes of temperature change, and displacements in case of symmetric and skew-symmetric wave modes are presented graphically.

Quantification of rapid temperature change during DO event 12 and phasing with methane inferred from air isotopic measurements

The description of rapid climatic changes during the last glacial period at high northern latitudes has been largely documented through Greenland ice cores that are unique climatic and environmental records. However, Greenland ice isotopic records are biased temperature proxies and it is still a matter of debate whether changes in the high latitudes lead or lag rapid changes elsewhere. We focus here on the study of the mid-glacial Dansgaard Oeschger event 12 (45 ky BP) associated to a large δ 18O ice change in the GRIP (GReenland Ice core Project) ice core. We use combined measurements of CH 4, δ 15N and δ 40Ar in entrapped air associated with a recently developed firn densification and heat diffusion model to infer (i) the phasing between methane and temperature increases and (ii) the amplitude of the temperature change. Our method enables us to overcome the difficulty linked with rapid accumulation change in quantifying the temperature change. We obtain a 12±2.5 °C temperature increase at the beginning of DO event 12 thus confirming that the conventional use of water isotopes in the Greenland ice cores largely underestimates the actual amplitude of rapid temperature change in central Greenland. In agreement with previous studies, methane and temperature increase are in phase at the sampling resolution of that part of our profile (90 years).

PROPAGATION OF GENERALIZED VISCOTHERMOELASTIC RAYLEIGH–LAMB WAVES IN HOMOGENEOUS ISOTROPIC PLATES

The present paper is aimed at studying the thermoelastic interaction in an infinite Kelvin–Voigt-type viscoelastic, thermally conducting plate. The upper and lower surfaces of the plate are subjected to stress-free, thermally insulated or isothermal conditions. The coupled dynamic thermoelasticity and generalized theories of thermoelasticity, namely, Lord and Shulman's, Green and Lindsay's, and Green and Nagdhi's are employed to understand the thermomechanical coupling and thermal and mechanical relaxation effects. Secular equations for the plate in closed from and isolated mathematical conditions for symmetric and skew-symmetric wave mode propagation in completely separate terms are derived. In the absence of mechanical relaxations (viscous effect), the results for generalized and coupled theories of thermoelasticity have been obtained as particular cases from the derived secular equations. In the absence of thermomechanical coupling, the analysis for a viscoelastic plate can be deduced from the present one. The various forms and regions of Rayleigh–Lamb-type secular equation have been obtained and discussed in addition to Lame modes, decoupled shear horizontal (SH) modes, and thin-plate results. At short-wavelength limits, the secular equations for symmetric and skew-symmetric waves in a stress-free insulated and stress-free isothermal plate reduce to the Rayleigh surface wave frequency equation. The amplitudes of temperature and displacement components during symmetric and skew-symmetric motion of the plate have been computed and discussed. Finally, the numerical solution is carried out for copper material. The dispersion curves, and amplitudes of temperature change and displacements for symmetric and skew-symmetric wave modes are presented to illustrate and compare the theoretical results.

Impacts of climate warming on plants phenophases in China for the last 40 years

Based on plant phenology data from 26 stations of the Chinese Phenology Observation Network of the Chinese Academy of Sciences and the climate data, the change of plant phenophase in spring and the impact of climate warming on the plant phenophase in China for the last 40 years are analyzed. Furthermore, the geographical distribution models of phenophase in every decade are reconstructed, and the impact of climate warming on geographical distribution model of phenophase is studied as well. The results show that (i) the response of phenophase advance or delay to temperature change is nonlinear. Since the 1980s, at the same amplitude of temperature change, phenophase delay amplitude caused by temperature decrease is greater than phenophase advance amplitude caused by temperature increase; the rate of phenophase advance days decreases with temperature increase amplitude, and the rate of phenophase delay days increases with temperature decrease amplitude. (ii) The geographical distribution model between phenophase and geographical location is unstable. Since the 1980s, with the spring temperature increasing in the most of China and decreasing in the south of Qinling Mountains, phenophases have advanced in northeastern China, North China and the lower reaches of the Changjiang River, and have delayed in the eastern part of southwestern China and the middle reaches of the Changjiang River; while the rate of the phenophase difference with latitude becomes smaller.

Amplitude of climatic changes in Qinghai-Tibetan Plateau

On the basis of ice core and meteorological data from the Qinghai-Tibetan (Q-T) Plateau, this article focuses on the discussion of the problems related to the sensitivity of temporal and spatial changes of the climate in high-altitude regions, particularly in the Q-T Plateau. The features of abrupt climatic changes of the past 100 ka, 2 000 a and recent years indicate that the amplitude of these changes in the Q-T Plateau was obviously larger than that in low-altitude regions. The scope of temperature change above 6 000 m in the Q-T Plateau between glacial and interglacial stages could reach over 10°C, but only about 4°C in low-elevation regions close to sea level. During the last 2 000 a, the amplitude of temperature changes at Guliya (over 6 000 m a.s.l.) in the Q-T Plateau reached 7°C, in comparison with 2°C in eastern China at low altitude. In the present age, apparent differences of climatic warming have been observed in the Q-T Plateau, indicating that the warming in high-elevation regions is much higher than that in low-elevation regions. The temperature in over 3 500 m regions of the Q-T Plateau have been increasing at a rate of 0.25×101/a in recent 30 years, but almost no change has taken place in the regions below 500 m. Thus, we concluded that high-altitude regions are more sensitive to climatic changes than the low-altitude regions.

Environmental factors influencing head density and diameter of crisp lettuce cv. Saladin

Crops of the crisp lettuce cv. Saladin were grown in 1988 and 1989 on four sites with up to four transplantings each year. After hearting the weight and size of heads were recorded weekly throughout growth, enabling head density to be calculated. Head density reached a minimum value during the mid-period of head growth and then increased to the value recorded at maturity. Denser heads were associated with low temperatures during the period up to and around hearting while less dense heads were primarily associated with higher temperatures in the period up to hearting and high levels of solar radiation in periods well after hearting. Larger heads were associated with low temperatures up to and around hearting, with very high temperatures in the immediate post-hearting period and with large amplitudes of temperature change and high levels of solar radiation around hearting. Smaller heads were primarily associated with high temperatures before hearting. The results demonstrate the sensitivity of the lettuce crop to environmental variables at specific stages of growth and our analysis of them may provide some explanation of the variation in head density and size observed between crops.

Thermal Deformation of Machining Center due to Temperature Change in the Environment.

The effect of environmental temperature change on the thermal deformation of machine tools is analyzed for the case of a machining center, both by experiments and by unsteady three-dimensional finite-element analyses. It is clarified that the air temperature surrounding the machining center varies depending on the altitude and the air flow condition, etc., and the amplitude of daily periodic variation also changes from one place to the other. The surface temperature of the machining center follows the ambient temperature with a time delay of 2 to 3 hours, but the amplitude of temperature change is slightly smaller than that of the ambience. The unsteady variations in the relative displacement and inclination between the main spindle and the work table of the machining center due to the ambient temperature variation are clarified quantitatively by the experiments and the finite element analyses.