Affect Heat Loss Research Articles

Ruthenium red attenuates brown adipose tissue thermogenesis in rats.

Ruthenium red (RR) is a non-selective antagonist of the temperature-sensitive Transient Receptor Potential (TRP) channels and it is an important pharmacological tool in thermoregulatory research. However, the effect of RR on thermoeffector activity is not well established. Here we evaluated the effect of RR on cold-defense thermoeffectors induced by menthol, an agonist of the cold-sensitive TRPM8 channel. Adult male Wistar rats were used. Epidermal treatment with menthol raised deep body temperature due to an increase in oxygen consumption (an index of thermogenesis), a reduction in heat loss index (an index of cutaneous vasoconstriction), and an induction in warmth-seeking behavior in a two-temperature choice apparatus. Pretreatment with RR attenuated the menthol-induced increase in deep body temperature and oxygen consumption, but it did not affect heat loss index and warmth-seeking behavior. To stimulate brown adipose tissue thermogenesis, rats were treated with CL 316,243, a potent and selective β3-adrenoceptor agonist. CL 316,243 increased deep body temperature, which was attenuated by RR pretreatment. We conclude that RR reduces brown adipose tissue thermogenesis induced by menthol and CL 316,243, independent of effects at the thermal sensor level (i.e., TRPM8).

Thermal properties of wooden based flask from tropical hardwood species

Abstract. Ogunsanwo OY, Onakpoma I, Korede M. 2020. Thermal properties of wooden based flask from tropical hardwood species. Asian J For 4: 61-64. Most materials used for production of conventional thermos flask (metals and plastics) are not environment friendly with particular concerns about plastic which are not biodegradable. Wood waste management is important in producing environmentally friendly materials and achieving sustainable development in forestry through wood waste utilization as thermos flask. This study was therefore conducted to investigate the thermal properties of wooden thermos flask (WTF) using tropical hardwood species with a view to promoting the use of greener technology. Offcuts of Tectona grandis and Albizia saman were used to produce 12 WTF of two thicknesses (11 mm and 12 mm), with a height of 10.5'' using bamboo as inner lining. The heat loss and heat gain by the wooden flasks and conventional flask were collected using a thermometer which was inserted into the cap of the flasks through a hole drilled in it, the hole was covered at intervals to prevent heat loss and heat gain from the opening. Data was collected every two hours for twelve hours. The study was laid out in a 2×2 factorial experimental in a completely randomized design. Data were analyzed using ANOVA at p=0.05. The highest heat loss (64.00ºC) after 12 hours was observed in Tectona grandis WTF with 11 mm and 12 mm while Albizia saman thermos flask with 12 mm thickness had the least heat loss (62.00ºC). Metallic flask lost only about 30.00 ºC of its heat content after 12 hours. The highest heat gain (28ºC) after 12 hours was observed in Tectona grandis WTF with 11mm and 12mm while Albizia saman WTF with 11 mm thickness had the least heat gain (25.67ºC). Heat gained by WTF was 28.00ºC and 25.83ºC for Tectona grandis and Albizia saman respectively after 12 hours while heat gain by the metallic flask after 12 hours was 18.00ºC. Species and thickness did not significantly affect heat loss and gain of thermos flask. Significant difference was however observed between the heat lost and gained by WTF and metallic flask. Wooden thermos flask still retained heat and prevented loss to a certain degree but technological improvement would perform better.

Effects of isomaltulose ingestion on postexercise hydration state and heat loss responses in young men.

What is the central question of this study? What are the effects of isomaltulose, an ingredient in carbohydrate-electrolyte beverages to maintain glycaemia and attenuate the risk of dehydration during exercise heat stress, on postexercise rehydration and physiological heat loss responses? What is the main finding and its importance? Consumption of a 6.5% isomaltulose-electrolyte beverage following exercise heat stress restored hydration following a 2h recovery as compared to a 2% solution or water only. While the 6.5% isomaltulose-electrolytes increased plasma volume and plasma osmolality, which are known to modulate postexercise heat loss, sweating and cutaneous vascular responses did not differ between conditions. Consequently, ingestion beverages containing 6.5% isomaltulose-electrolytes enhanced postexercise rehydration without affecting heat loss responses. Isomaltulose is a disaccharide carbohydrate widely used during exercise to maintain glycaemia and hydration. We investigated the effects of ingesting a beverage containing isomaltulose and electrolytes on postexercise hydration state and physiological heat loss responses. In a randomized, single-blind cross-over design, 10 young healthy men were hypohydrated by performing up to three 30min successive moderate-intensity (50% heart rate reserve) bouts of cycling, each separated by 10min, while wearing a water-perfusion suit heated to 45°C. The protocol continued until a 2% reduction in body mass was achieved. Thereafter, participants performed a final 15min moderate-intensity exercise bout followed by a 2h recovery. Following cessation of exercise, participants ingested a beverage consisting of (i) water only (Water), (ii) 2% isomaltulose (CHO-2%), or (iii) 6.5% isomaltulose (CHO-6.5%) equal to the volume of 2% body mass loss within the first 30min of the recovery. Changes in plasma volume (ΔPV) after fluid ingestion were greater for CHO-6.5% compared with CHO-2% (120min postexercise) and Water (90 and 120min) (all P≤0.040). Plasma osmolality remained elevated with CHO-6.5% compared with consumption of the other beverages at 30 and 90min postexercise (all P≤0.050). Urine output tended to be reduced with CHO-6.5% compared to other fluid conditions (main effect, P=0.069). Rectal and mean skin temperatures, chest sweat rate and cutaneous perfusion did not differ between conditions (all P>0.05). In conclusion, compared with CHO-2% and Water, consuming a beverage consisting of CHO-6.5% and electrolytes during recovery under heat stress enhances PV recovery without modulating physiological heat loss responses.

Leads and ridges in Arctic sea ice from RGPS data and a new tracking algorithm

Abstract. Leads and pressure ridges are dominant features of the Arctic sea ice cover. Not only do they affect heat loss and surface drag, but they also provide insight into the underlying physics of sea ice deformation. Due to their elongated shape they are referred to as linear kinematic features (LKFs). This paper introduces two methods that detect and track LKFs in sea ice deformation data and establish an LKF data set for the entire observing period of the RADARSAT Geophysical Processor System (RGPS). Both algorithms are available as open-source code and applicable to any gridded sea ice drift and deformation data. The LKF detection algorithm classifies pixels with higher deformation rates compared to the immediate environment as LKF pixels, divides the binary LKF map into small segments, and reconnects multiple segments into individual LKFs based on their distance and orientation relative to each other. The tracking algorithm uses sea ice drift information to estimate a first guess of LKF distribution and identifies tracked features by the degree of overlap between detected features and the first guess. An optimization of the parameters of both algorithms, as well as an extensive evaluation of both algorithms against handpicked features in a reference data set, is presented. A LKF data set is derived from RGPS deformation data for the years from 1996 to 2008 that enables a comprehensive description of LKFs. LKF densities and LKF intersection angles derived from this data set agree well with previous estimates. Further, a stretched exponential distribution of LKF length, an exponential tail in the distribution of LKF lifetimes, and a strong link to atmospheric drivers, here Arctic cyclones, are derived from the data set. Both algorithms are applied to output of a numerical sea ice model to compare the LKF intersection angles in a high-resolution Arctic sea ice simulation with the LKF data set.

Evaluation of energy efficiency of external stud partitions with use of numerical analysis

The need to save energy necessitates the search for solutions that would enable us to reduce heat losses. Currently the majority of investments are financed with use of mortgages, that is why the investors search for optimal technological solutions i.e. guarantee high energy savings. One of those solutions is construction in frame technology. This technology allows to achieve the heat transfer characteristics of a passive house with partitions that are ca. 40% thinner than their counterparts in traditional brick technology. According to different sources detached houses use ca. 70 ÷ 80% of the energy for heating. The subject of the article was the analysis of total heat loss through vertical wall of detached home made of wooden stud structure and for two types of steel stud structure – made of fully enclosed and THERMO profiles. On the basis of the literature recommendations and normative documents dependency calculated heat loss by transfer while computer simulation shows how thermal bridges of adopted solutions affect heat loss. For the purpose of analyzed external partitions heat loss was compared for heating season in buildings in each of the climate zones of Poland. What was also analyzed was the cost of heating for different fuels. The analysis showed significant differences in the adopted solutions. For example in case of gas central heating the difference in annual bills for different climatic zones can be ca. 20%, and the difference in costs of heat loss between the wooden stud framing and the steel stud framing is over 30%. The results show that use of appropriate technology can minimize those losses, thus securing significant lowering of heating bills. In turn, thanks to MES-e-based calculations, it is possible at the design stage to analyze the technological and construction solutions which are extremely important during the operation of the facility.

The thermoregulatory function of the human hand: How do palm and digit proportions affect heat loss?

The current study assessed whether ecogeographical patterns seen in hand proportions correlate with heat loss directly. Using a brief severe cold immersion experiment on the hand, the influence of hand and digit dimensions on heat loss was evaluated. A sample of 113 living individuals were tested. Two-dimensional and three-dimensional scanning techniques were used to assess hand and digit dimensions. Thermal imaging analysis was used to quantify heat loss during a 3-min ice-water immersion of the hands. When body size was accounted for, hand width and digit length relative to total hand length were significant predictors of heat loss from the hand. The current study provides empirical evidence to support the link between thermodynamic principles relating to surface area-to-volume ratio, and ecogeographical patterns associated with temperature.

A self-learning algorithm for estimating solar heat gain and temperature changes in a single-Family residence

To develop effective control optimization strategies for managing residential electricity consumption in a smart grid environment, predictive algorithms are needed that are simple to implement, minimize custom configuration, and provide sufficient accuracy to enable meaningful control decisions. This paper presents a self‐learning algorithm for predicting indoor temperature in a single-family residence using a first-order lumped capacitance (1R1C) model that can be used to evaluate the consequences of energy saving or load shifting strategies on thermal comfort. The algorithm is formulated in such a way that key design details such as window size/configuration, thermal insulation, and airtightness (all major factors that affect heat loss and solar heat gain) are combined into effective parameters that can be learned from observation. This approach eliminates the need for a custom configuration for each residence.The model was validated using experimental data from the National Institute of Standards and Technology (NIST) Net-Zero Energy Residential Test Facility. It was found that with a simple temperature decay test to determine a thermal time constant and a seven-day sliding window of training data to account for seasonal variations in other parameters, the algorithm can reliably predict indoor temperatures for a 24h period using a solar irradiance forecast, an outdoor air temperature forecast, and heat pump output. The average root mean square temperature prediction error was found to be 2.2%.

Thermo-physiological comfort of soft-shell back protectors under controlled environmental conditions

The aim of the study was to investigate thermo-physiological comfort of three back protectors identifying design features affecting heat loss and moisture management. Five volunteers tested the back protectors in a climatic chamber during an intermittent physical activity. Heart rate, average skin temperature, sweat production, microclimate temperature and humidity have been monitored during the test. The sources of heat losses have been identified using infrared thermography and the participants answered a questionnaire to express their subjective sensations associated with their thermo-physiological condition. The results have shown that locally torso skin temperature and microclimate depended on the type of back protector, whose design allowed different extent of perspiration and thermal insulation. Coupling physiological measurements with the questionnaire, it was found that overall comfort was dependent more on skin wetness than skin temperature: the participants preferred the back protector with the highest level of ventilation through the shell and the lowest level of microclimate humidity.

Thermoregulatory Scope Associated with Underwater Exercise in a Polar Seal

A weakness in predicting habitat change impacts in polar regions is that little is known about thermoregulatory energetics in high‐latitude seals. To better understand thermoregulatory range associated with the partitioned air‐water habitat of ice seals, we collected skin surface heat flux data from 42 free‐ranging Weddell seals over 1‐13 day deployments. We modeled total body heat dissipation from heat flux data to address the thresholds of basal versus activity‐derived heat loss over a range of swim speeds. As body size/condition affect heat loss and may manifest as altered thresholds for thermal homeostasis, we compared 4 life history categories—pups, juveniles, non‐reproductive adult females and post‐weaning females. Preliminary evidence indicates obligate heat dissipation, reflecting thermoregulatory costs, is elevated in water versus air, and locomotory heat generation offsets these costs. Dive activity‐heat loss relationships were compared among the 4 life history stages to detect differences in baseline obligate heat loss and threshold swim speeds for thermal substitution. Group differences were apparent under non‐steady state conditions such as transition from haul‐out to water, where post‐weaning females lost more heat than good condition skip breeder females (+40% W/m2 heat loss). Juveniles, with limited blubber insulation, also lost more heat than pups on initial water entry. Continued efforts to quantify and model thermoregulatory thresholds will provide important insights into the ability of polar pinnipeds to respond to changing ice conditions.

Research on the Impact of Wind Angles on the Residential Building Energy Consumption

Wind angles affect building’s natural ventilation and also energy consumption of the building. In winter, the wind direction in the outdoor environment will affect heat loss of the building, while in summer the change of wind direction and speed in the outdoor environment will affect the building’s ventilation and indoor air circulation. So, making a good deal with the issue of the angle between local buildings and the dominant wind direction can effectively solve the winter and summer ventilation problems. Thereby, it can enhance the comfort of residential person, improve indoor air quality, solve heat gain and heat loss problems in winter and summer in the severely cold and cold regions, and reduce building energy consumption. The simulation software CFD and energy simulation software are used in the paper. South direction of the building is the prototype of the simulation. The angle between the direction of the building and the outdoor environment wind is changed sequentially. Energy consumption under different wind angle conditions is compared with each other. Combined with natural ventilation under various wind angles, the paper gives the best recommended solution of building direction in Shenyang.

Profiling heat loss in an extreme polar mammal, the Weddell seal

A major weakness in predicting habitat change impacts in polar regions is that little is actually known about energetic costs of basic thermoregulation in high‐latitude seals and other apex predators. Characteristics of body size and condition (surface area: volume ratios, insulation) are likely to affect heat loss and manifest as altered thresholds for thermal homeostasis. We monitored the thermal interface between animal‐environment directly via skin surface heat flux sensors (HFS) and indirectly with infrared thermography (IRT) in Weddell seals (n=42) over 2–7d. Utilizing 4 life history categories—pups, juveniles, non‐reproductive adult females (skip breeders) and post‐weaning females—we tested for effect of body size and known insulation patterns (blubber depth via imaging ultrasound). IRT surface temperature maxima and range suggested 4 sites of interest for HFS placement and continued monitoring: axilla (variable hot), head (hot), flank (variable cold) and neck (cold). IRT‐generated surface temperature distribution histograms further permitted the partitioning of body surface area such that an integrated thermal profile could be modeled from HFS data collected at these 4 sites. With this tool we can for the first time examine thermal homeostasis in free‐ranging seals over a range of potentially changing environments. Funded by NSF Polar Programs.

Supplemental ascorbic acid does not affect inferred heat loss in broiler chickens exposed to elevated temperature

The provision of supplemental ascorbic acid has been reported to lower the body temperature of chickens maintained at elevated environmental temperatures. Since body temperature is the net effect of heat production and heat loss, it is not known if the reductions in body temperature were due to a lower heat production or an increase in heat loss. The purpose of this work was to determine if supplemental ascorbic acid facilitates heat loss in chickens exposed to an elevated temperature. On day 12 post-hatch broiler chickens were implanted intra-abdominally with a thermo-sensitive radio transmitter. The following day, birds were placed inside an indirect calorimeter maintained at 34C for 24h and provided water containing 0 or 400ppm ascorbic acid. Oxygen consumption, carbon dioxide production, heat production, respiratory exchange ratio, and body core temperature were measured for 3h; beginning 21h after the birds were placed inside the calorimeter. No differences were observed in heat production or body core temperature between birds provided or not and 400ppm ascorbic acid. This suggests that ascorbic acid has no effect on heat loss. Birds provided ascorbic acid did exhibit a significantly lower respiratory exchange ratio suggesting a greater utilization of lipid for energy production. Although lipid has a lower heat increment compared with protein and carbohydrate, the significance of this finding to birds exposed to elevated temperature is not known. In conclusion, under the conditions of this study the provision of supplemental ascorbic acid to broiler chickens maintained at an elevated temperature did not affect heat loss as inferred from measured heat production and body core temperature.

Modification of water masses in the Barents Sea and its coupling to ice dynamics: a model study

The physical and biological environment of the Barents Sea is characterised by large variability on a wide range of scales. Results from a numerical ocean model, SINMOD, are presented showing that the physical variability is partly forced by changes in annual net ice import. The mean contribution from ice import in the simulation period (1979–2007) is about 40% of the total amount of ice melted each year. The annual ice import into the Barents Sea varies between 143 and 1,236 km3, and this causes a substantial variability in the amount of annual ice melt in the Barents Sea. This in turn impacts the freshwater content. The simulated freshwater contribution from ice is 0.02 Sv on average and 0.04 Sv at maximum. When mixed into a mean net Atlantic Water (AW) inflow of 1.1 Sv with a salinity of 35.1, this freshwater addition decreases the salinity of the modified AW to 34.4 and 33.9 for the mean and maximum freshwater fluxes, respectively. Ice import may thus be important for the Barents Sea production of Arctic Ocean halocline water which has salinity of about 34.5. The changes in the ice melt the following summer due to ice import also affect the formation of dense water in the Barents Sea by changing stratification, altering the vertical mixing rates and affecting heat loss from the warm AW. The model results thus indicate that ice import from the Arctic has a great impact on water mass modification in the Barents Sea which in turn impacts the ventilation of the Arctic Ocean.

Thermoregulation in elite athletes

Exercise causes body temperature to rise and the resulting heat stored becomes a factor limiting exercise performance in hot conditions. Loss of heat by evaporative processes leads to hypohydration which itself can eventually impair performance. This review focuses on thermoregulatory and behavioural processes during sustained exercise in the heat. Several studies have implicated cerebral mechanisms in eschewing fatigue due to heat stress. Acclimatization improves performance by affecting heat loss mechanisms, implicating peripheral and central processes. Pharmacological methods of increasing heat tolerance are unacceptable strategies for the athlete, but appropriate precooling measures are effective. This review highlights the combination of physiological processes that converge in heat stress during extended exercise. Pharmacological ergogenic aids are discouraged due to likely side effects in cerebral function whereas behavioural measures, including precooling the body, have practical support.

Role of L-glutamate in systemic AVP-induced hypothermia.

It has been reported that systemic injection of arginine vasopressin (AVP) induces a drop in body core temperature (T(c)), but little is known about the mechanisms involved. Because glutamate is an important excitatory neurotransmitter involved in a number of thermoregulatory actions, in the present study, we tested the hypothesis that glutamate plays a role in systemic AVP-induced hypothermia. Wistar rats were pretreated intracerebroventricularly (icv) with kynurenic acid, an antagonist of l-glutamate ionotropic receptors, alpha-methyl-(4-carboxyphenyl)glycine (MCPG), an antagonist of l-glutamate metabotropic receptors, or saline 15 min before intravenous injection of AVP (2 microg/kg) or saline. T(c), brown adipose tissue (BAT) temperature, blood pressure, heart rate, and tail skin temperature were measured continuously. Administration of saline icv followed by intravenous AVP caused a significant drop in T(c) brought about by a reduction in BAT thermogenesis and an increase in heat loss through the tail. MCPG treatment (icv) did not affect the fall in T(c) induced by AVP. Treatment with kynurenic acid (icv) abolished AVP-induced hypothermia but did not affect the AVP-evoked rise in blood pressure or drop in heart rate and BAT temperature. Heat loss through the tail was significantly reduced in animals injected with AVP and pretrated with kynurenic acid. These data indicate that ionotropic receptors of l-glutamate in the central nervous system participate in peripheral AVP-induced hypothermia by affecting heat loss through the tail.

Systemic hemodynamic changes raising brain temperature in REM sleep

The present research studied the mechanisms underlying the increase in brain temperature during REM sleep in the unrestrained rabbit carrying chronically implanted electrodes, thermistors and common carotid artery occluders. During the ultradian wake–sleep cycle at constant ambient temperature (25±2 °C), we recorded: (i) the ear pinna temperature as an indirect indicator of blood flow affecting heat loss from the systemic heat exchangers of the head, (ii) the temperature of the pons and hypothalamus as indirect indicators of the temperature of vertebral artery blood (systemic cooling only) and carotid artery blood (both systemic and selective cooling), respectively, and (iii) the changes induced in these temperatures by short-lasting bilateral common carotid artery occlusion. The results show that during REM sleep both systemic and selective brain cooling are depressed by a spontaneous decrease in the common carotid artery blood flow and the associated autoregulatory increase in the vertebral artery share of the cerebral blood supply.

Morphometric and Biochemical Factors Affecting Heat Loss in a Small Temperate Cetacean (Phocoena phocoena) and a Small Tropical Cetacean (Stenella attenuata)

Harborporpoises (Phocoena phocoena) and spotted dolphins (Stenella attenuata) must cope with very different thermal situations. Harbor porpoises live in cold coastal waters where water temperatures average 10° - 15° C; spotted dolphins live in the Eastern Tropical Pacific Ocean ecosystem where water temperatures average 27° C. There are few options available to cetaceans for thermoregulation. Thepurpose of the present study was to investigate factors that affect heat loss in small Cetacea and to compare these factors in harbor porpoises and spotted dolphins. Phocoena had a smaller surface area, for a given mass, than did Stenella. This suggests possible selection for a decreased surface area/body mass ratio in harbor porpoises. Conductivity of harbor porpoise blubber (0.10 ± 0.01 W m⁻¹ °C⁻¹, n = 29) was significantly lower (P < 0.05) than that of spotted dolphins (0.20±0.02 W m⁻¹ °C⁻¹, n = 16), signifying a higher insulative quality for Phocoena. In addition to being a superior insulator, Phocoena blubber depth (1.5 ± 0.3 cm, n = 59) was double that of Stenella (0.8 ± 0.1 cm, n = 16). Blubber conductivity varied inversely with lipid content. Harbor porpoise blubber was 81.6% ± 3.6% (n = 29) lipid, whereas spotted dolphin blubber was 54.9% ± 2.8% (n = 16) lipid. Conductivity values measured for Phocoena are the lowest recorded for any cetacean species. Measures of conductivity for Stenella are similar to those of other cetaceans. The morphometric and biochemical differences found in the blubber of these two species implies that small cetaceans can use a combination of surface area and insulative quality and quantity to thermoregulate. These responses are dictated by ambient temperature but are constrained by body size and, possibly, hydrodynamic considerations.

Electric versus Steam Energy for Pipe-Line Tracing

Under no-flow conditions, the energy required to maintain a given temperature on a pipe line is directly proportional to the product of the line temperature above ambient and the time that the temperature is maintained. Since outside ambient temperature varies as a sine curve about the average temperature, the amount of heat required is also continuously changing. On a line traced to prevent freezing manually, controlled, or uncontrolled, steam will expend over 700 percent more energy to maintain the temperature than will electric tracing. With flow in the pipe, the heat wasted by steam can be even greater since the flowing material acts as a heat sink. Since the flow conditions affecting heat loss vary greatly, each installation must be calculated separately. It is quite possible that a steam tracer will expend energy at its maximum rate under conditions that would not require any heat. Steam tracing is more efficiently used on lines requiring a temperature approaching that of the tracing steam.

Variability of Lake Ice Growth and Quality in the Schefferville Region, Central Labrador—Ungava

Abstract An examination of rates of ice growth, actual ice thickness and the quality of the lake ice profile on Knob Lake, central Labrador—Ungava, showed that all these factors were extremely variable. Three sites were established on Knob Lake from 1957 to 1961, and a similar sequence of sites was established on a neighbouring lake, Maryjo Lake, from 1959 to 1961. Significant variations occurred within a single lake body from site to site, though it was noted that certain patterns of ice growth and quality did occur throughout most years and could be directly related to patterns of snow accumulation on the lake. Variations from lake to lake were found to be least at the centre lake sites, probably because snow cover was always least at these sites and would not affect heat loss so greatly as at the marginal sites. It is suggested that the majority of empirical formulae proposed for lake ice growth are unrealistic for short-term forecasting of ice thickness and growth, and even long-term forecasting, using accumulated degree-days of frost, only gives average values. The only answer is repeated samplings on any lake, until such time that sufficient data are gathered for a full statistical approach based on probability analysis.

Variability of Lake Ice Growth and Quality in the Schefferville Region, Central Labrador—Ungava

AbstractAn examination of rates of ice growth, actual ice thickness and the quality of the lake ice profile on Knob Lake, central Labrador—Ungava, showed that all these factors were extremely variable. Three sites were established on Knob Lake from 1957 to 1961, and a similar sequence of sites was established on a neighbouring lake, Maryjo Lake, from 1959 to 1961. Significant variations occurred within a single lake body from site to site, though it was noted that certain patterns of ice growth and quality did occur throughout most years and could be directly related to patterns of snow accumulation on the lake. Variations from lake to lake were found to be least at the centre lake sites, probably because snow cover was always least at these sites and would not affect heat loss so greatly as at the marginal sites. It is suggested that the majority of empirical formulae proposed for lake ice growth are unrealistic for short-term forecasting of ice thickness and growth, and even long-term forecasting, using accumulated degree-days of frost, only gives average values. The only answer is repeated samplings on any lake, until such time that sufficient data are gathered for a full statistical approach based on probability analysis.