Fluid inclusions as constraints in a three‐dimensional hydro‐thermo‐mechanical model of the Paris basin,France

Fluid inclusion homogenization temperatures and three‐dimensional hydro‐thermo‐mechanical modelling were combined to constrain fluid flow, solute and heat transport in the Paris basin, France, focusing on the two main petroleum reservoirs i.e. the Dogger and the Triassic (Keuper) formations. The average homogenization temperatures of two‐phase aqueous inclusions in different samples range from 66 °C to 88 °C in the Dogger calcite cement, from 106 °C to 118 °C in the Keuper dolomite cement and from 89 °C to 126 °C in the Keuper quartz and K‐feldspar cements. The maximum homogenization temperatures for inclusions in the Keuper quartz and K‐feldspar cements were 17–47 °C higher than present‐day temperatures in the boreholes at similar depths. Processes that might explain higher temperatures in the past were examined through numerical simulations and sensitivity tests. A warmer climate in the Late Cretaceous–Early Tertiary resulted in a temperature rise of only 8 °C. Late Cretaceous chalk had a thermal blanketing effect that resulted in simulated temperatures as high as 15–20 °C above the present day ones. An additional 300 m deposition and subsequent erosion of chalk, not taken into account so far, has to be considered to simulate the high palaeo‐temperatures recorded by fluid inclusions in both reservoirs. In view of the simulated thermal history of the basin, in the Keuper, an age of about 85 Ma is consistent with quartz/K‐feldspar temperatures and an age of about 65 Ma is in agreement with the precipitation temperature of the dolomite cement. Our models suggest an age of about 50 Ma for the Dogger calcite cementation.     

Thermal state of the Roer Valley Graben,part of the European Cenozoic Rift System

We performed a detailed analysis of the thermal state of the Cenozoic Roer Valley Graben, the north–western branch of the European Cenozoic Rift System, based on a new set of temperature data. We developed a numerical technique for correcting bottom hole temperatures, including an evaluation of the uncertainty of thermal parameters. Comparison with drill stem test temperatures indicated that the uncertainty in corrected bottom hole temperatures using a two‐component numerical model is approximately ± 4 °C, which is much more accurate than the up to 15 °C errors encountered in often‐used line‐source or Horner correction methods. The subsurface temperatures and the derived regional heat flow estimates of 53 ± 6 to 63 ± 6 mW m^?2 show no significant difference between the central rift and the adjacent structural highs. The absence of an elevated heat flow is attributed to the low amount of lithospheric thinning during the Cenozoic rifting phase (β=1.06–1.15). A local thermal anomaly exceeding +10 °C was found in five wells in the north–western part of the rift basin at depths of 1000–1500 m, and is most likely caused by the upward flow of fluids along faults, whereas lower temperatures in the upper 1500 m in the southern part of the rift basin could indicate cooling by topography‐driven groundwater flow. Conflicting ideas exist on the active or passive rifting mechanisms responsible for the formation of the different rift basins of European Cenozoic Rift System. The low spatial variation in heat flow found in this study suggests that the mechanism responsible for forming the Roer Valley Graben is passive rifting.     

Fossil chironomid assemblages and inferred summer temperatures for the past 14,000 years from a low-elevation lake in Pacific Canada

Fossil midge remains in a sediment core from Lake Stowell, a low-elevation lake in coastal British Columbia, Canada, were used to assess temporal changes in chironomid communities and to produce quantitative estimates of mean July air temperature (MJAT) for the past 14,000 years based on two different transfer functions. Chironomid assemblages are diverse throughout much of the record, with most taxa present at low relative abundances. The basal portion of the sediment record is characterized by low head capsule concentrations, taxonomic diversity and organic matter content, all of which increase towards the early Holocene. Inferred temperatures suggest a cool late-glacial interval with a minimum MJAT of 12.5 °C, ~2 °C cooler than the inferred modern temperature. Summer temperatures gradually increased from this minimum until a brief cooling of as much as ~3 °C relative to modern that coincides with the Younger Dryas chronozone. An interval of warmer summers with MJAT of ~16 to 18 °C (2–3 °C warmer than modern) is inferred between ~10,500 and 8000 cal year BP. This early Holocene warm period was followed by generally cooler inferred temperatures in the middle and late Holocene. The midge-inferred temperature record from Lake Stowell is generally consistent with other temperature reconstructions from the region based on chironomid remains and other climate proxies. This research underscores the potential of low-elevation, mid-latitude sites for chironomid-based temperature reconstructions. In order to maximize the availability of modern analogues for robust temperature reconstructions from similar sites, calibration datasets should be expanded to include more sites from the warm end of the temperature gradient.     

Influence of temperature variations during a cold period on the conditions of life of the population in East Siberia

On the territory of East Siberia, the positive deviations of mean monthly air temperatures from long-term annual mean air temperatures for the past 30 years (1981–2010) were caused by the shortening of the low-temperature periods. The largest decrease of the number of days with a daily mean temperature below ?25 °C is recorded in the southern and middle parts of the macroregion under conditions of a moderate, strong and very strong discomfort. On the other hand, the resulting range of variation in the number of days with a mean daily temperature below ?25 °C and the duration of the heating period remain within the long-term values. A slight rise in mean temperature for the heating period entails a marked reduction in degree-days.     

Photo-thermal regulation of seed germination in natural populations of Eruca sativa Miller (Brassicaceae)

Populations of the winter annual Eruca sativa in Israel are distributed along a climatic gradient, from Mediterranean mesic habitats in the north to semi-arid and arid habitats in the south. Seed cohorts of five populations sampled across the gradient were produced in a common-garden experiment, and their germination was tested under continuous light or darkness at 5–35 °C, as well as with alternating 30/20 and 25/15 °C temperatures under a 12/12 h photoperiod. Germination was enhanced by light and by increasing temperature. Under constant temperatures maximal germination of arid and semi-arid populations was lower than in the mesic populations, suggesting on higher levels of primary dormancy with increasing aridity. Seeds that did not germinate in darkness or at low temperatures in light, germinated almost fully when exposed to GA₃ at 25 °C, indicating that imbibition under less favorable conditions induces secondary dormancy in E. sativa. Daily alternating temperatures did not affect or even reduced seed germination compared to constant 25 and 30 °C in continuous light. Exposure of dry seeds to 30 °C before imbibition increased germination to ≥80% in seed cohorts of all populations. These responses to light and temperature indicate that adaptation of E. sativa to the Mediterranean environment is associated with the ability to germinate under the relatively warm autumn temperatures, and is enhanced by exposure to high temperature during the dry summer.     

Five thousand years of sediment transfer in a high arctic watershed recorded in annually laminated sediments from Lower Murray Lake,Ellesmere Island,Nunavut, Canada

Sediments in Lower Murray Lake, northern Ellesmere Island, Nunavut Canada (81°21′ N, 69°32′ W) contain annual laminations (varves) that provide a record of sediment accumulation through the past 5000+ years. Annual mass accumulation was estimated based on measurements of varve thickness and sediment bulk density. Comparison of Lower Murray Lake mass accumulation with instrumental climate data, long-term records of climatic forcing mechanisms and other regional paleoclimate records suggests that lake sedimentation is positively correlated with regional melt season temperatures driven by radiative forcing. The temperature reconstruction suggests that recent temperatures are ~2.6°C higher than minimum temperatures observed during the Little Ice Age, maximum temperatures during the past 5200 years exceeded modern values by ~0.6°C, and that minimum temperatures observed approximately 2900 varve years BC were ~3.5°C colder than recent conditions. Recent temperatures were the warmest since the fourteenth century, but similar conditions existed intermittently during the period spanning ~4000–1000 varve years ago. A highly stable pattern of sedimentation throughout the period of record supports the use of annual mass accumulation in Lower Murray Lake as a reliable proxy indicator of local climatic conditions in the past.

Classification of climates and climatic regionalization of the West-Siberian plain

We examine some issues related to a classification of climates. A climatic regionalization has been carried out, and a brief characteristic given to the identified types of climate. It has been found that the relationship of the sums of mean daily ground air temperatures above 10 °C and the dryness index show a clearly pronounced zonal distribution. The combination of sums of mean daily air temperatures below ?10 °C and the depth of snow in the northern part of the plain is characterized by a horizontal distribution, and only in the middle and southern parts of the plain do these indices acquire zonal regularities. An analysis is made of the long-term dynamics of air temperature to reveal that some climate warming during 1981–2010 was mainly caused by a rise in winter air temperature.     

基于Modis地表温度的青藏高原东部及其邻近地区气温估算(英文)

Climatic conditions are difficult to obtain in high mountain regions due to few meteorological stations and, if any, their poorly representative location designed for convenient operation. Fortunately, it has been shown that remote sensing data could be used to estimate near-surface air temperature (Ta) and other climatic conditions. This paper makes use of recorded meteorological data and MODIS data on land surface temperature (Ts) to estimate monthly mean air temperatures in the southeastern Tibetan Plateau and its neighboring areas. A total of 72 weather stations and 84 MODIS images for seven years (2001 to 2007) are used for analysis. Regression analysis and spatio-temporal analysis of monthly mean Ts vs. monthly mean Ta are carried out, showing that recorded Ta is closely related to MODIS Ts in the study region. The regression analysis of monthly mean Ts vs. Ta for every month of all stations shows that monthly mean Ts can be rather accurately used to estimate monthly mean Ta (R2 ranging from 0.62 to 0.90 and standard error between 2.25℃ and 3.23℃). Thirdly, the retrieved monthly mean Ta for the whole study area varies between 1.62℃ (in January, the coldest month) and 17.29℃ (in July, the warmest month), and for the warm season (May-September), it is from 13.1℃ to 17.29℃. Finally, the elevation of isotherms is higher in the central mountain ranges than in the outer margins; the 0℃ isotherm occurs at elevation of about 4500±500 m in October, dropping to 3500±500 m in January, and ascending back to 4500±500 m in May next year. This clearly shows that MODIS Ts data combining with observed data could be used to rather accurately estimate air temperature in mountain regions.     

The cooling effect of crushed rock structures on permafrost under an embankment

Based on the analysis and comparison of soil temperature, thermal regime and permafrost table under the experimental embankment of crushed rock structures in Beiluhe, results show that crushed rock structures provide an extensive cooling effect, which produces a rising permafrost table and decreasing soil temperatures. The rise of the permafrost table under the embankment ranges from an increase of 1.08 m to 1.67 m, with an average of 1.27 m from 2004 to 2007. Mean annual soil temperatures under the crushed rock layer embankment decreased significantly from 2005 to 2007, with average decreases of ?1.03 °C at the depth of 0.5 m, ?1.14 °C at the depth of 1.5 m, and ?0.5 °C at the depth of 5 m. During this period, mean annual soil temperatures under the crushed rock cover embankment showed a slight decrease at shallow depths, with an average decrease of ?0.2 °C at the depth of 0.5 m and 1.5 m, but a slight rise at the depth of 5 m. After the crushed rock structures were closed or crammed with sand, the cooling effect of the crushed rock layer embankment was greatly reduced and that of the crushed rock cover embankment was just slightly reduced.     

Investigation of the thermal history of the Delaware Basin (West Texas,USA) using carbonate clumped isotope thermometry

We utilized carbonate clumped isotope thermometry to explore the thermal history of the Delaware Basin, West Texas, USA. Carbonate wellbore cuttings from five oil/gas wells across the basin yielded clumped isotope temperatures (T(Δ₄₇)) ranging from 27°C to 307°C, interpreted to reflect a combination of initial precipitation/recrystallization temperature and solid-state C-O bond reordering during burial. Dolomite samples generally record lower apparent T(Δ₄₇)s than calcite, reflecting greater resistance to reordering in dolomite. In all five wells, clumped isotope temperatures exceed modern downhole temperature measurements, indicating higher heat flow in the past. Using modelled burial curves based on sedimentological history, we created unique time-temperature histories by linearly applying a geothermal gradient. Applying two different thermal history reordering models, we modelled the extent of solid-state C–O bond reordering to iteratively find the time-averaged best-fit geothermal gradients for each of the five wells. Results of this modelling suggest that the shallower, southwestern portion of the study area experienced higher geothermal gradients throughout the sediment history (~45°C/km) than did the deeper, southeastern portion (~32°C/km), with the northern portion experiencing intermediate geothermal gradients (~35–38°C/km). This trend is in agreement with the observed gas/oil ratios of the Delaware Basin, increasing from east to west. Furthermore, our clumped isotope temperatures agree well with previously published vitrinite reflectance data, confirming previous observations and demonstrating the utility of carbonate clumped isotope thermometry to reconstruct basin thermal histories.     

VARIATION OF AN URBAN HEAT ISLAND IN PHOENIX

Long-term minimum temperature records at climatic stations in the metropolitan Phoenix area present evidence of changes attributed to the urbanization process. The winter mean minimum temperature near the city's center has increased by 2° C from the agricultural period (1901–1920) to the modern period (1961–1977) and the difference of winter mean minimum temperatures between the center of the metropolitan region and the suburban area has increased from 3° C to 4° C during the same periods.     

Imbibition temperatures affect bitterbrush seed dormancy and seedling vigor

Bitterbrush first-year seedling survival is low. To determine whether imbibition temperatures affected seedling vigor, I compared post-imbibition seed weight, germination, and early growth among untreated, thiourea-treated, and cool-moist-treated seeds from three collections. Seedling axial lengths from untreated seeds averaged 28 mm among all imbibition temperatures. This compared to 31 mm from thiourea-treated seeds, 68 mm from seed held at 5°C for 14 days, and 118 mm from seeds held at 2°C for 28 days. There was no imbibition temperature for untreated or thiourea-treated seeds that compensated for the lack of a cool-moist treatment. Seed treatments or seedbed conditions which fully remove dormancy and reduce dormant-seed respiration appear likely to increase seedling survival during the first growing season.     

Impacts of future climate change on agroclimatic resources in Northeast China

In this study, the spatial distribution and changing trends of agricultural heat and precipitation resources in Northeast China were analyzed to explore the impacts of future climate changes on agroclimatic resources in the region. This research is based on the output meteorological data from the regional climate model system for Northeast China from 2005 to 2099, under low and high radiative forcing scenarios RCP4.5 (low emission scenario) and RCP8.5 (high emission scenario) as proposed in IPCC AR5. Model outputs under the baseline scenario, and RCP4.5 and RCP8.5 scenarios were assimilated with observed data from 91 meteorological stations in Northeast China from 1961 to 2010 to perform the analyses. The results indicate that: (1) The spatial distribution of temperature decreases from south to north, and the temperature is projected to increase in all regions, especially under a high emission scenario. The average annual temperature under the baseline scenario is 7.70°C, and the average annual temperatures under RCP4.5 and RCP8.5 are 9.67°C and 10.66°C, respectively. Other agricultural heat resources change in accordance with temperature changes. Specifically, the first day with temperatures ≥10°C arrives 3 to 4 d earlier, the first frost date is delayed by 2 to 6 d, and the duration of the growing season is lengthened by 4 to 10 d, and the accumulated temperature increases by 400 to 700°C·d. Water resources exhibit slight but not significant increases. (2) While the historical temperature increase rate is 0.35°C/10a, the rate of future temperature increase is the highest under the RCP8.5 scenario at 0.48°C/10a, compared to 0.19°C/10a under the RCP4.5 scenario. In the later part of this century, the trend of temperature increase is significantly faster under the RCP8.5 scenario than under the RCP4.5 scenario, with faster increases in the northern region. Other agricultural heat resources exhibit similar trends as temperature, but with different specific spatial distributions. Precipitation in the growing season generally shows an increasing but insignificant trend in the future, with relatively large yearly fluctuations. Precipitation in the eastern region is projected to increase, while a decrease is expected in the western region. The future climate in Northeast China will change towards higher temperature and humidity. The heat resource will increase globally, however its disparity with the change in precipitation may negatively affect agricultural activities.     

A 2000 year varve-based climate record from the central Brooks Range,Alaska

Varved minerogenic sediments from glacial-fed Blue Lake, northern Alaska, are used to investigate late Holocene climate variability. Varve-thickness measurements track summer temperature recorded at Atigun Pass, located 41 km east at a similar elevation (r ² = 0.31, P = 0.08). Results indicate that climate in the Brooks Range from 10 to 730 AD (varve year) was warm with precipitation inferred to be higher than during the twentieth century. The varve-temperature relationship for this period was likely compromised and not used in our temperature reconstruction because the glacier was greatly reduced, or absent, exposing sub-glacial sediments to erosion from enhanced precipitation. Varve-inferred summer temperatures and precipitation decreased after 730 AD, averaging 0.4°C above the last millennial average (LMA = 4.2°C) from 730 to 850 AD, and 0.1°C above the LMA from 850 to 980 AD. Cooling culminated between 980 and 1030 AD with temperatures 0.7°C below the LMA. Varve-inferred summer temperatures increased between 1030 and 1620 AD to the LMA, though the period between 1260 and 1350 AD was 0.2°C below the LMA. Although there is no equivalent to the European Medieval Warm Period in the Blue Lake record, two warm intervals occurred from 1350 to 1450 AD and 1500 to 1620 AD (0.4 and 0.3°C above the LMA, respectively). During the Little Ice Age (LIA; 1620 to 1880 AD), inferred summer temperature averaged 0.2°C below the LMA. After 1880 AD, inferred summer temperature increased to 0.8°C above the LMA, glaciers retreated, but aridity persisted based on a number of regional paleoclimate records. Despite warming and glacial retreat, varve thicknesses have not achieved pre-730 AD levels. This reflects limited sediment availability and transport due to a less extensive retreat compared to the first millennium, and continued relative aridity. Overall, the Blue Lake record is similar to varve records from the eastern Canadian Arctic that document a cool LIA and twentieth century warming. However, the occurrence and timing of events, such as the LIA and Medieval Warm Period, varies considerably among records, suggesting heterogeneous climatic patterns across the North American Arctic.

Midge-inferred temperature reconstructions and vegetation change over the last ~15,000?years from Trout Lake, northern Yukon Territory, eastern Beringia

Two cores from Trout Lake, northern Yukon, yielded quantitative estimates of summer air temperatures using fossil midge larvae. Warming began around 14,400?cal?yr BP, with inferred mean July air temperatures reaching values warmer than present by 12,800?cal?yr BP. A 1?°C cooling from 12,200 to 11,200?cal?yr BP closely corresponds with the Younger Dryas chronozone. A broad temperature maximum occurred between 10,800 and 9,800?cal?yr BP, with mean July air temperature about 2.2?°C warmer than present. This represents an early Holocene thermal maximum and coincides with increased organic content of the sediment. Both the shallow- and deep-water cores show similar temperature trends for their overlapping periods. The inferred rise in mean July air temperature at 14,200?cal?yr BP coincides with a shift in vegetation from an herb- to shrub-dominated landscape. In contrast, the increase in Alnus pollen at 6,400?cal?yr BP does not coincide with a change in temperature, but may be a response to a rise in precipitation.     

Surface temperature inversion in the palsa and pounu fields of northern Finland

A very large surface inversion, which would not have been detected at the official recording height of 2 m above the mire surface, was recorded at the snow surface of an earth hummock in Lapland. The maximum inversion was 35 °C, and the monthly temperature departure was 7.8 °C in December 1992. The characteristics of the surface inversion are compared with conditions during another winter when no long inversion periods occurred. The presence of this surface inversion may explain the formation of new permafrost in pounus, even when official records showed no unusually low temperatures.     

Avalanche prediction in Scotland: II. Development of a predictive model

The paper presents a method for predicting avalanche activity from meteorological data which is suitable for Scottish snow conditions. Two main types of avalanche are distinguished. Direct-action avalanches are the result of fresh snow accumulation and may release after approximately 200 mm of fresh snow has fallen over a period of a few days. They become extremely likely if a further 100 mm falls in a single day. Climax avalanches are the result of strength loss in the snow cover, due either to thawing or persistent cold. Thaws may produce an avalanche after only three or four days with maximum temperatures around 2°C. Alternatively, if maximum temperatures remain below ?4°C for over a week, and especially if cold weather persists for two weeks, slab avalanches of dry snow are likely to occur. Between these two types are several possible avalanche situations in which fresh snow accumulation is combined with high or low temperatures. Topography plays a passive role, and determines where avalanche activity is most likely. Free faces, smooth surfaces and slopes in the lee of major storms respond most rapidly to the onset of avalanche conditions.     

The first permafrost cycle in Færdesmyra,eastern Finnmark,Norway?

The author studied the causal relationships between palsa formation, the maintenance of palsas, their final thawing, and climate. His main approach was to compare his observations with other researchers’ observations of recent palsa formation and degradation, and the use of relevant palaeoclimatic data. A more than 10 km² large palsa mire complex in Sør-Varanger Municipality, northern Norway, was studied in terms of vegetation and stratigraphy 50 years ago, and then observed between 2005 and 2015, when the final palsa thawing occurred. The decisive climatic factor for the maintenance of existing palsas – annual mean temperatures below -1 °C, stated earlier by researchers – seemed to be valid also in the studied case. However, the results showed that new palsa formation may require a series of consecutive years with temperatures between -1 and -2 °C in annual mean temperatures. There is a possibility of detecting former palsas (i.e. since thawed) by stratigraphic investigations in cases of lateral erosion of palsas. Stratigraphic corings and field observations in the selected study area did not indicate earlier periods of palsa thawing prior to the modern one. The author concludes that the present thawing thus reflects a reversal of the final cooling stage of the present interstadial (Holocene).     

Germination responses of Medicago ruthenica seeds to salinity,alkalinity, and temperature

To determine the effects of and the interactions between salinity and temperature, and alkalinity and temperature, we conducted three germination tests of Medicago ruthenica (L.) Sojak cv. ‘Zhilixing’ seeds in growth chambers. In experiment 1, the seeds were placed at a range of temperatures (5, 10, 15, 20, 25, 30, 35, or 40 °C), and in experiments 2 and 3, we varied the salinity (0, 50, 100, 150, 200, or 250 mM NaCl) and alkalinity (1, 5, 10, 15, 20, or 25 mM Na₂CO₃), respectively, within three ranges of alternating temperatures (10–20, 15–25, and 20–30 °C). The seeds of M. ruthenica (L.) Sojak cv. ‘Zhilixing’ showed high percentage germination at all temperatures, except for 5 °C. Seeds germinated well at low NaCl and Na₂CO₃ concentrations under all three alternating temperature regimes. Approximately half the seeds germinated at high salinity and alkalinity at 15–25 °C, whereas the ungerminated seeds germinated when the high-saline and alkaline stresses were removed. These results suggest that M. ruthenica (L.) Sojak cv. ‘Zhilixing’ has potential utility as a forage legume in saline and alkaline environments.     

Deep vs. shallow controlling factors of the crustal thermal field – insights from 3D modelling of the Beaufort‐Mackenzie Basin (Arctic Canada)

Significant lateral variations in observed temperatures in the Beaufort‐Mackenzie Basin raise the question on the temperature‐controlling factors. Based on the structural configuration of the sediments and underlying crust in the area, we calculate the steady‐state 3D conductive thermal field. Integrated data include the base of the relic permafrost layer representing the 0 °C‐isotherm, public‐domain temperature data (from 227 wells) and thermal conductivity data. For >75% of the wells the predicted temperatures deviate by <10 K from the observed temperatures, which validates the overall model setup and adopted thermal properties. One important trend reproduced by the model is a decrease in temperatures from the western to the eastern basin. While in the west, a maximum temperature of 185 °C is reached at 5000 m below sea level, in the east the maximum temperature is 138 °C. The main cause for this pattern lies in lateral variations in thermal conductivity indicating differences in the shale and sand contents of the different juxtaposed sedimentary units. North‐to‐south temperature trends reveal the superposition of deep and shallow effects. At the southern margin, where the insulating effect of the low‐conductive sediments is missing, temperatures are lowest. Farther north, where the sub‐sedimentary continental crust is thick enough to produce considerable heat and a thick pile of sediments efficiently stores heat, temperatures tend to be highest. Temperatures decrease again towards the northernmost distal parts of the basin, where thinned continental and oceanic crust produce less radiogenic heat. Wells with larger deviations of the purely conductive model from the temperature observations (>15 K at 10% of the wells) and their basin‐wide pattern of misfit tendency (too cold vs. too warm temperature predictions) point to a locally restricted coupling of heat transport to groundwater flow.