Mean Ground Temperature Research Articles

Climate model sensitivity to changes in Miocene paleotopography

The Middle Miocene Climatic Optimum (MMCO), which occurred between 17 and 15 Ma, was the last of a series of warming events to have punctuated the Cenozoic and is the warmest the planet has been since 35 Ma (∼6°C warmer than present at middle latitudes). Paradoxically, CO2 concentrations during the MMCO are reported at present-day values or less and an explanation for warming has yet to be established. We test the sensitivity of version three of the Community Atmosphere Model (CAM) and Community Land Model (CLM) to changes in Middle Miocene paleotopography using prescribed sea-surface temperatures. We create four separate global paleotopography datasets based on altered Andean and Tibetan Plateau elevations as well as changes to global sea-level. We find that the largest warming is achieved with a lowering of the Tibetan Plateau from 4700 to 2600 m, resulting in a local temperature increase of up to 9°C—consistent with the modern-day lapse rate measured in China—and a global mean ground temperature increase of 0.5°C. An additional effect of this lowering is to weaken the summer and winter monsoons, and we discuss implications such changes may have for coupled ocean–atmosphere simulations. We conclude that while changes to topography significantly affect local temperatures, they do little to reconcile the disagreement between temperature and CO2 measurements derived from the geological record.

Influence of Photoperiod and Temperature on the Larval Behavioral Diapause ofAmblyomma cajennense(Acari: Ixodidae)

Larval behavioral diapause was shown to be the major factor controlling the 1-yr generation pattern of Amblyomma cajennense (F.) (Acari: Ixodidae) in Brazil. During fieldwork, this behavior was shown to coincide with long daylength (>12 h) and high mean ground temperature (approximately =25 degrees C), which prevail during spring-summer in Brazil. The current study evaluated biological parameters of engorged females, their eggs, and the resultant larvae inside plastic pots planted with the grass Brachiaria decumbens Stapf. held in incubators set with different combinations of temperature and photoperiod. Both the long daylength (photoperiod 14:10 [L:D] h) and high temperature (25 degrees C) during larval hatching induced larval behavioral diapause, characterized by the confinement of hatched larvae on the ground below the vegetation for many weeks. When long daylength was present during hatching, but temperature was low (15 degrees C), larvae did not enter diapause. Similarly, when short daylength (10:14 or 12:12) was present during larval hatching, larvae did not enter diapause regardless whether temperature was high (25 degrees C). Termination of diapause was induced by shifting photoperiod from 14:10 to 12:12 or the temperature from 25 to 15 degrees C. When applied to field conditions, the present results indicate that both high ground mean temperature (approximately =25 degrees C) and long daylength (>12 h) during spring-summer (October-March) are responsible for the induction and maintenance of A. cajennense larval behavioral diapause in the field. Furthermore, both the low ground mean temperature (approximately 20 degrees C) and the short daylength (<12 h) during autumn (April-May) are responsible for termination of larval behavioral diapause in the field.

Recent extreme near‐surface permafrost temperatures on Svalbard in relation to future climate scenarios

Here we report extreme near‐surface permafrost warming resulting from a remarkable temperature anomaly during winter and spring 2005–2006 on Svalbard. We demonstrate that this atmospheric temperature anomaly fell well within the range of predicted warming scenarios for the late 21st Century. The mean December to May air temperature on Svalbard was as high as −4.8°C, some 8.2°C above the 1961–1990 average. The 2006 mean ground temperature at the permafrost table in a monitored borehole in bedrock was 1.8°C higher than the mean for the previous six years, and this corresponded to a 40% reduction in accumulated annual negative degree‐days at that depth. The thermal response was detectable to a depth of at least 15 m. In future, a greater frequency of high‐temperature anomalies such as this, superimposed on a warming trend, is likely to cause potentially hazardous irregular acceleration in near‐surface permafrost thawing.

First in situ determination of the thermal performance of a U-pipe borehole heat exchanger, in Cyprus

A ground heat exchanger can be used for the injection or extraction of thermal energy into/from the ground. The line source model is an easy method of evaluating the characteristics of the borehole and does not need expensive equipment. This method is presented and a test is performed in order to determine a borehole’s characteristics in layers consisting of clay, silt and sand at various analogies. For the borehole under test the ground thermal conductivity ( λ) was found to be 1.605 W/(m K) and the effective borehole thermal resistance ( R b) to be 0.257 K/(W/m). The accuracy of the collected data could be affected mainly by two factors. The first factor is the daily flux penetration through the ground which gradually increases the temperature of the top layers and the second factor is a variation of the heating coil injection rate per active length of borehole. As it was observed this combined effect has a negligible result on the mean fluid temperature during the test hours of 280–400, when the system was operating at steady state. The steady state conditions yield values of borehole thermal resistance which deviates about 25% from the values given by the line source method. The ground thermal conductivity deviates only about 5%. This method however is not suitable for estimating the above values because of the uncertainty that exists in the estimation of the mean ground temperature, which is not constant throughout the borehole length nor is it constant at different points in a cross section of the grout. Also this method takes a lot of time until the steady state is reached.

Reply to comment by Klump et al. on “Noble gases and stable isotopes in a shallow aquifer in southern Michigan: Implications for noble gas paleotemperature reconstructions for cool climates”

[1] In their comment, Klump et al. [2006], hereinafter referred to as KBK, make three main points concerning Hall et al. [2005]: (1) that the model of excess air that accounts for fractionation via the mechanism of diffusive loss should have produced significant changes from normal isotopic ratios; (2) the suggestion that the presence of excess He in the gas phase in the unsaturated zone is incorrect; and (3) the observed offset in noble gas temperatures (NGTs) from measured ground temperature can be explained by locking in noble gas concentrations during the annual snow melt. Point 3, which is by far the most relevant portion of the comment, deserves most of our attention in this reply. It is important to note up front that the model, as suggested in KBK is completely unworkable for the site studied in the work of Hall et al. [2005]. KBK note that more data would resolve some of the unresolved issues from Hall et al. [2005], but this is true for any preliminary study.

Comment on “A projection of severe near‐surface permafrost degradation during the 21st century” by David M. Lawrence and Andrew G. Slater

Comment on “A projection of severe near‐surface permafrost degradation during the 21st century” by David M. Lawrence and Andrew G. Slater

Spring Emergence Biology of the Cabbage Seedpod Weevil (Coleoptera: Curculionidae)

The spring emergence biology of Ceutorhynchus obstrictus (Marsham) was investigated in 2003 and 2004 in relation to habitat type, vegetative cover, and soil temperature in the Mixed Grassland Ecoregion of western Canada. Although total emergence extended over 10–12 wk, emergence patterns were very similar in both years with limited emergence occurring for several weeks before and after a large emergence peak of comparatively short duration. In 2003, peak emergence occurred during a 3-wk period from 28 May to 13 June when 97.6% of C. obstrictus were collected; and in 2004, emergence of 55.6% of weevils occurred during the 1-wk period before 4 June. Peak emergence occurred as mean ground temperature (5 cm in depth) reached 15°C. The greatest number of weevils recorded from a single 1-m2 emergence trap was 956. Significantly more weevils emerged from sheltered and intermediately sheltered locations than from open grassy habitats; sheltered areas were predominantly shelterbelts and yard sites of caragana and poplar trees. No weevils emerged from 14 of 106 cages, and all cages were in open grassy habitat. Spring emergence of weevils in open grassy areas occurred slightly before those in sheltered and intermediately sheltered areas. Cages in open grassy habitat had the highest mean temperature as well as the highest maximum and lowest minimum temperatures in each sampling period. Significantly more males than females emerged early in the season, although during peak emergence there was no difference in sex ratio; and after peak emergence, significantly more females than males emerged.

Treatment of Undercanopy Turbulence in Land Models

Abstract In arid and semiarid regions most of the solar radiation penetrates through the canopy and reaches the ground, and hence the turbulent exchange coefficient under canopy Cs becomes important. The use of a constant Cs that is only appropriate for thick canopies is found to be primarily responsible for the excessive warm bias of around 10 K in monthly mean ground temperature over these regions in version 2 of the Community Climate System Model (CCSM2). New Cs formulations are developed for the consistent treatment of undercanopy turbulence for both thick and thin canopies in land models, and provide a preliminary solution of this problem.

Emergence of overwintered and new generation adults of the crucifer flea beetle, Phyllotreta cruciferae (Goeze) (Coleoptera: Chrysomelidae)

Spring emergence of the crucifer flea beetle, Phyllotreta cruciferae (Goeze), was investigated in 2003 and 2004 in relation to habitat type, vegetative cover, and soil temperature in the Mixed Grassland Ecoregion of western Canada. Although total emergence extended over 10–12 weeks, emergence patterns were quite similar in both years with limited emergence for several weeks before and after a large emergence peak of comparatively short duration. In each year, peak emergence occurred near the end of May as mean ground temperature reached 15 °C. Approximately 45,000 flea beetles were collected with the greatest number of flea beetles recorded from a single 1 m 2 emergence cage being 3736. Significantly more flea beetles emerged from sheltered locations than from open habitats; sheltered areas were predominantly shelterbelts and yard sites of Caragana and poplar trees. In each year, highest numbers of flea beetles emerged in cages placed in Caragana while the fewest emerged from cages in grassy areas. Consistently more females than males emerged throughout the spring with a sex ratio of approximately 1.5 females: 1 male. Emergence of new generation adults occurred from the middle of August until the end of September; this emergence was delayed and extended in late-seeded canola. Seeding date and rate did not significantly affect the abundance of new generation flea beetles. The sex ratio of new generation adults was approximately 1.2 females: 1 male. Emergence cages could be a useful tool for researchers monitoring year-to-year populations of P. cruciferae but the narrow time frame between spring emergence and crop infestation may restrict the usefulness of this tool for producers.

In Situ Test on Cooling Effectiveness of Air Convection Embankment with Crushed Rock Slope Protection in Permafrost Regions

An experimental air convection embankment (ACE) was constructed in Beiluhe on the Qinghai-Tibet Plateau during 2001–2003, using coarse (5–8 and 40–50 cm), poorly graded crushed rock fill material on the slope of embankment with thick ground ice permafrost foundation, which should be called the air convection embankment with crushed rock slope protection (ACE–CRSP). The highly permeable ACE–CRSP installation was designed to test the cooling effectiveness of ACE–CRSP concept in an actual railway project. Ground temperature data were collected from test sections on the railway with thermistor sensor strings. The results showed that the mean ground temperature under the layer of the crushed rock with coarse particle diameter of 40–50 cm was lower than that under one with finer particle diameter of 5–8 cm, and the fluctuating range of temperature under the former was bigger than that under the latter. It was obvious that the maximum thaw depth was raised under the layer of crushed rock with coarse particle diameter of 40–50 cm, which resulted from the stronger cooling effectiveness of air convection during the winter. The amount of heat exchange also showed that the absorbed cooling energy of the foundation, under the layer of the crushed rock with coarse diameter, was larger than that with finer diameter.So, we believe that the cooling effectiveness of the crushed rock layer with coarse diameter was stronger than that one with finer diameter.

Frost-cracking conditions, Bylot Island, eastern Canadian Arctic archipelago

The meteorological and ground temperature conditions under which frost cracking takes place in an ice-wedge polygon site were inferred from electric cables that were probably severed by ground thermal contraction. Between 1997 and 2002, the severing of cables in the active layer occurred mostly in January. The daily mean air temperature when the cables broke ranged from −25 to −40°C, with a mean of −34.3°C. They generally broke after a drop in air temperature of about 7.9°C over a mean period of 18 h, at a mean atmospheric cooling rate of −0.5°C/h. The breaks occurred a few hours to a few days after the arrival of persistently cold temperatures, the daily mean ground temperature being −22.9°C at 2 cm under the surface (1997–2002) and −18.6°C at the permafrost table (2000–2002). The mean thermal gradient in the active layer at the time of breakage was −10.9°C/m. Maximum ground cooling rates during breaking episodes were located in the active layer or at the top of permafrost. Copyright © 2005 John Wiley & Sons, Ltd.

A world‐wide study of high altitude treeline temperatures

AbstractAim At a coarse scale, the treelines of the world's mountains seem to follow a common isotherm, but the evidence for this has been indirect so far. Here we aim at underpinning this with facts.Location We present the results of a data‐logging campaign at 46 treeline sites between 68° N and 42° S.Methods We measured root‐zone temperatures with an hourly resolution over 1–3 years per site between 1996 and 2003.Results Disregarding taxon‐, landuse‐ or fire‐driven tree limits, high altitude climatic treelines are associated with a seasonal mean ground temperature of 6.7 °C (±0.8 SD; 2.2 K amplitude of means for different climatic zones), a surprisingly narrow range. Temperatures are higher (7–8 °C) in the temperate and Mediterranean zone treelines, and are lower in equatorial treelines (5–6 °C) and in the subarctic and boreal zone (6–7 °C). While air temperatures are higher than soil temperatures in warm periods, and are lower than soil temperatures in cold periods, daily means of air and soil temperature are almost the same at 6–7 °C, a physics driven coincidence with the global mean temperature at treeline. The length of the growing season, thermal extremes or thermal sums have no predictive value for treeline altitude on a global scale. Some Mediterranean (Fagus spp.) and temperate South Hemisphere treelines (Nothofagus spp.) and the native treeline in Hawaii (Metrosideros) are located at substantially higher isotherms and represent genus‐specific boundaries rather than boundaries of the life‐form tree. In seasonal climates, ground temperatures in winter (absolute minima) reflect local snow pack and seem uncritical.Main conclusions The data support the hypothesis of a common thermal threshold for forest growth at high elevation, but also reflect a moderate region and substantial taxonomic influence.

Geothermal evidence of very low glacial temperatures on a rim of the Fennoscandian ice sheet

The mean ground temperature as low as −10°C and the existence of more than 500 m thick permafrost during the last glacial are apparent from the analysis of deep borehole temperature profiles in north‐eastern Poland. The largest thickness of the permafrost and its survival deep into the Holocene was restricted to a region known for its low terrestrial heat flow, where the negative temperature gradient is observed in the uppermost 400 m. We have shown that the profiles are consistent with warming from the glacial mean of −10°C to the Holocene mean of +7°C 14 ka ago and to +8°C in the last 150 years.

Experimental Research on Vegetation Response to Artificial Warming on a Mid-Latitude High Mountain, Central Japan

In order to investigate the vegetation response to global warming, experimental research was carried out on a high mountain of Japan for three years from 1997 to 1999. The experimental site was in the alpine zone at 2, 780m above sea level, near the peak of Mt. Norikura (3, 026m) in central Japan. Vegetation growing period is about 4 months without snow cover from early June to early October. Five open top chambers with a diameter of 80cm and a height of 30cm were used for temperature enhancement, and another five places were selected as controls outside the chambers. The main objectives were to clarify the differences in vegetation growth, phenology, biomass and coverage of plant between temperature-enhanced chambers and controls. To prove temperature enhancement, air temperature at vegetation height of 5cm high above ground and ground temperature at root layer of 3cm depth were recorded every hour in each chamber and at each control. Vegetation growth and phenology of several alpine species were measured at about four-week intervals, and biomass and coverage were measured on the last experimental day every year. The mean air temperature at vegetation height and mean ground temperature at root layer in chambers were about 0.65°C and 0.25°C higher than in the controls, respectively. Vegetation growth was significantly accelerated, and phenology was surely affected by the extension of growth period due to temperature enhancement for most of the plants observed. Vegetation growth and phenology, however, varied with species, indicating that species vary in response to warming. Differences in biomass between chambers and controls were not significant for all years, suggesting that the total growth of plants in the unit area is controlled by nutrient conditions of the soil. Through three years of experiment, coverage of Loiseleuria procumbens (Ericaceae) recognizably increased, overcoming other species in chambers, while there were no conspicuous changes in controls. It suggests that L. procumbens whose canopy expands horizontally over the other forbs might be more physiologically active than others under warming conditions, although vegetation growth showed positive response to temperature enhancement for most species.

Thermal regime in the embankment of Qinghai–Tibetan Highway in permafrost regions

Based on the data of two groups of ground temperature along Qinghai–Tibetan Highway in permafrost regions in recent five years, this paper analyzes the thermal regime in the embankment in higher and lower temperature permafrost regions, respectively. The results show that the annual mean ground temperature in the embankment is evidently higher than that in the natural ground and the thawing period in the embankment is longer than that in the natural ground, too. In the embankment of higher temperature permafrost regions, talik has formed between the active layer and below permafrost, and the heat flux entering the active layer is in an accumulative state. In both higher and lower temperature permafrost regions, the input of heat into the permafrost below the embankment is greater than the output. The causes of the continual thaw of permafrost in higher temperature permafrost regions are attributed to the ground temperature near 0 °C and the continuous accumulation of heat in the embankment. In lower temperature permafrost regions, the heat entering the permafrost below embankment is mainly to raise the temperature of permafrost for the moment. With the rise of ground temperature, the permafrost below embankment in lower temperature permafrost regions may also be thawed violently.

The thermal regime of a retrogressive thaw slump near Mayo, Yukon Territory

The development of a retrogressive thaw slump near Mayo, Yukon Territory, has been traced from initiation by bank erosion (~1949) of the Stewart River to stabilization in 1993-1994. The stabilized headwall of the slump is 450 m from the river, and the slope of the slump floor is 3°. A transect of the slump from the river to the stabilized headwall was drilled in July 1995, to determine the extent and rate of permafrost degradation in the slump floor. Thermistors were placed in access tubes to 12 m depth at five sites, four near the transect and one in undisturbed terrain, to determine the magnitude of thermal disturbance due to slump development. Data loggers at the sites recorded the ground temperature at 1 m depth for two years from August 1995. The annual mean ground temperatures measured by the data loggers varied between 1.2° and 1.8°C in the slump, compared with -2.4°C in undisturbed ground, indicating a disturbance of about 4°C due to slumping. The depth of thaw in the slump floor is consistent with the Stefan solution for thawing of permafrost. Conduction is the dominant mode of heat transfer in the slump, where the soil is fine grained and there is almost no organic horizon. Winter ground temperatures at 1 m depth were nearly 6°C warmer in the slump than in the surrounding forest, even though snow depths were similar, due to the release of latent heat during prolonged frost penetration. These data demonstrate the importance of subsurface conditions on near-surface ground temperatures in winter.

Ants as bioindicators of habitat disturbance: validation of the functional group model for Australia's humid tropics

A functional group model of ant community composition has been widely used in Australia to analyse biogeographical patterns of ant community structure and the responses of ant communities to disturbance. The model has provided valuable support to the widespread use of ant communities as bioindicators of ecological change. However, the model was developed from studies of arid-zone faunas, and its applicability to the World Heritage rainforests of Queensland's humid tropics has not yet been validated. Here we test predictions based on the functional group model for ant communities in Queensland's humid rainforests, by documenting ant community composition and its responses to disturbance on the Atherton Tablelands. Five sites were studied, comprising two relatively undisturbed reference sites representing contrasting rainforest types, and three previously cleared sites, two of which were undergoing revegetation. A variety of sampling techniques were employed, including pitfall trapping, litter extractions, baiting, and general searching. A total of 50 ant species from 29 genera were collected. Site species richness was highest at the reference sites, and lowest at the unvegetated disturbed site, and overall was negatively related to mean ground temperature. As predicted by the functional group model, behaviorally dominant dolichoderines were uncommon or absent at the reference sites, and the most common ants were Generalized myrmicines and Opportunists. Also as predicted, habitat disturbance favored Opportunists, and, as the disturbance involved canopy clearance, this led to colonization by Iridomyrmex and other Dominant dolichoderines. Opportunists represented about 40% of total ants in traps at the reference sites, compared with 80–95% at the disturbed sites. Except one species, Tropical Climate Specialists and Specialist Predators were absent from disturbed sites. In conclusion, patterns of ant composition in relation to disturbance on the Atherton Tablelands conform to the functional group model that has been widely applied to ant faunas elsewhere in Australia. The model may therefore play an important role in the use of ants as bioindicators of ecological change in the World Heritage rainforests of this region.

Nature and dynamics of an active block stream, kunlun pass, qinghai province, people's republic of china

Active block streams are common on the slopes of mountains on the northern, drier portion of the Qinghai‐Xizang (Tibetan) Plateau. Between 1990 and 1995, the authors studied a block stream northeast of the crest of the Kunlun Pass at latitude 35°50’N, longitude 94°05’ E. It occurs on a 31° slope facing southwest at 4800 m altitude and consists of a 15 cm layer of blocks moving downslope over a sandy loam of lacustrine origin. The blocks are derived from both frost shattering of exposed bedrock and by ejection of blocks from the till capping the hill. No water flows in the block stream and its surface is level with the surrounding slope. Mean annual air temperature is –6°C and mean annual precipitation is about 320 mm. The few plants growing between the blocks exhibit elongated stems and/or roots, indicating movement of the upper layers of blocks relative to the underlying materials. Average mean annual downslope movement of the surface blocks ranges up to 95 cm but varies both across the block stream and also along its long axis. The blocks are gradually extending further downslope. Comparison of movement of lines painted on stones in summer and winter shows that most of the movement occurs in winter. The stones usually rotate randomly as they move, probably by sliding on ice. There is no obvious sorting or rounding of the blocks during movement downslope. The deposits produced differ from talus/scree sediments as they have a dip of less than the maximum angle of rest of dry sediment (c. 33°) and also show no sorting downslope. The movement of material takes place predominantly in winter, rather than in summer and the deposits occur in areas of negligible snow cover. Ground temperatures suggest exceptionally rapid temperature changes under the blocks, indicating air exchange in the voids. Mean ground temperatures in the loams beneath the blocks are about 7°C colder than in the adjacent soils. Winter snow covers are noticeably absent, and summer precipitation is often in the form of snow, which soon melts. Permafrost is present beneath the block stream but is absent in the sandy loam soils. The ground is also moister beneath the blocks. It appears that the surface blocks tend to slide downslope on the icy surface of the underlying blocks, perhaps aided by water from melting snow. This and the lack of sorting by clast size clearly differentiates them from talus slopes or avalanche deposits.

スピッツベルゲン，ニューオールスンにおける地温の観測

Ground temperature was continuously measured during 1994-1996 on a debris-mantled slope near Ny Alesund, Spitsbergen. Measurements were taken at one-hour intervals using a digital data logger connected to four platinum thermistor sensors, which were inserted at 0, 10, 40, 80 cm in depth.Diurnal freeze-thaw cycles occurred only five times during the 1994 freezing period and 14 times during the 1995 freezing period. The average frost depth during these diurnal cycles was 4.7 cm. Small daily temperature ranges at the ground surface indicate that the slope was covered with snow from middle September to June or July. The late-lying snow cover was responsible for the absence of diurnal freeze-thaw cycles during the thawing period. Seasonal freezing began in middle to late September, and the freezing front penetrated to a depth of 80cm during these weeks. The seasonal frost began to melt in mid-June, and the thawing front reached a depth of 80 cm in two weeks. The thickness of the active layer was estimated to be about 110 cm on the basis of the distribution of the mean ground temperature profile in July. Seasonal freeze-thaw cycles are considered to be much more selective in producing periglacial landforms in this region than diurnal cycles.

Ground temperature history in central Europe from borehole temperature data

SUMMARY Ground temperature histories (GTH) are inferred from temperature measurements in several boreholes of south-eastern Germany and western Bohemia (Czech Republic). The GTHs that can be extracted from these boreholes, ranging in depth between 150 and 700m, cover the past 250yr. Both data sets were inverted separately and yield consistent GTHs. They were also inverted jointly to yield a regional GTH of the past 250yr for this part of Europe. The results indicate two main episodes in the mean ground temperature with (1) a cooling period from 1750-1800 to 1930-1950, followed by (2) short colder and warmer periods until now. The same trends are found in the meteorological records at four nearby weather stations (Bayreuth, Jena, Munchen and Praha), but the meteorological record in Berlin is clearly distinct. The GTH for this part of Europe is also markedly different from one obtained in central France. These differences are consistent with the spatial variability of climatic trends.