Gain of heat and temperature in the shallow subsurface over the last decades/century has been impacted by the industrial period climatic surface air temperature (SAT) increase. Detailed study of the available temperature-depth data based on 43 wells with single and repeated temperature logs done by the first author has been combined with data base information (Jessop et al 2005) to create temperature maps at depth. Based on these 43 logs it is shown that the heat flux increases with depth in most cases for the available depth data range from surface to some 200m. Model of heat flow versus depth based on the surface air temperature changes through the industrial epoque climatic warming explains the data. Spatial and depth distribution of available temperature and heat gain through the provinces of the Western Canadian Sedimentary Basin WCSB shows that drilling closer to surface is more economic than deeper to 50-100m.

This paper presents a review of geophysical studies of the crust and the lithosphere-asthenosphere boundary (LAB) in the ocean-continent transition in the area of Spitsbergen (Svalbard Archipelago) in high Arctic. Over last decades many investigations were performed during Polish geophysical expeditions, as well as in the framework of international cooperation with scientists from Germany, Japan. Norway and USA. We compiled here existing seismic, gravity and thermal models down to LAB depth along the 800 km long transect extending from the actively spreading Knipovich Ridge, across southern Spitsbergen to the Kong Karls Land Volcanic Province. The results of all methods are very consistent, although they are sensitive to different physical parameters: seismic wave velocities, densities and thermal. The thinnest lithosphere of only 12 km is found beneath the Knipovich Ridge. Only 50 km to the west and 50 km to the east of the ridge the LAB depth increases to about 30 km, and this value corresponds to the oceanic structure of the North Atlantic Ocean. Beneath southern Spitsbergen the LAB depth is about 55 km and increases to 90-100 km beneath continental structure of the Barents Sea. The uplift of the LAB close to distance of 700 km along transect could be correlated with Kong Karls Land Volcanic Province.

Heat flow patterns variability related to the age of the consolidated, and differences in, sedimentary thickness of the sedimentary succession are important constraints upon the thermal state of the sedimentary fill and its geothermal energy potential. Heat flow in the Permian basin of central Europe varies from a low of 40 mWm−2 in the Precambrian Platform to 80 mWm−2 in the Paleozoic basement platform influencing temperature for geothermal potential drilling depth. Continuity of thermal patterns and compatibility of heat flow Q across the Permian basin across the Polish–German basin was known from heat flow data ever since the first heat flow map of Europe in 1979. Both Polish and German heat flow determinations used lab-measured thermal conductivity on cores. This is not the case for the recent heat flow map of Poland published in 2009 widely referenced in Polish geological literature. Significant differences in heat flow magnitude exist between many historical heat flow maps of Poland over the 1970s–1990s and recent 21st century patterns. We find that the differences in heat flow values of some 20–30 mWm−2 in Western Poland exist between heat flow maps using thermal conductivity models using well log interpreted mineral and porosity content and assigned world averages of rock and fluid thermal conductivity versus those measured on cores. These differences in heat flow are discussed in the context of resulting mantle heat flow and the Lithosphere-Asthenosphere Boundary depth modelled differences and possible overestimates of deep thermal conditions for enhanced geothermal energy prospects in Poland.

We summarize the feasibility of using geothermal energy from the Western Canada Sedimentary Basin (WCSB) to support communities with populations >3000 people, including those in northeastern British Columbia, southwestern part of Northwest Territories (NWT), southern Saskatchewan, and southeastern Manitoba, along with previously studied communities in Alberta. The geothermal energy potential of the WCSB is largely determined by the basin’s geometry; the sediments start at 0 m thickness adjacent to the Canadian shield in the east and thicken to >6 km to the west, and over 3 km in the Williston sub-basin to the south. Direct heat use is most promising in the western and southern parts of the WCSB where sediment thickness exceeds 2–3 km. Geothermal potential is also dependent on the local geothermal gradient. Aquifers suitable for heating systems occur in western-northwestern Alberta, northeastern British Columbia, and southwestern Saskatchewan. Electrical power production is limited to the deepest parts of the WCSB, where aquifers >120 °C and fluid production rates >80 kg/s occur (southwestern Northwest Territories, northwestern Alberta, northeastern British Columbia, and southeastern Saskatchewan. For the western regions with the thickest sediments, the foreland basin east of the Rocky Mountains, estimates indicate that geothermal power up to 2 MWel. (electrical), and up to 10 times higher for heating in MWth. (thermal), are possible.

Functional space inversions (FSI) of precise temperature logs from 43 wells, located in low conductivity clastic sediments of the Western Canadian Sedimentary Basin, (WCSB), reveal evidence of extensive, recent ground surface temperature (GST) warming. Simultaneous inversion of log data acquired during the period of 1987-2005, as well as averaging of the individual site reconstructions of subsurface temperature signals, indicate evidence of high magnitude of warming of about 2°C (with standard deviations of 0.7°C). Magnitudes of such warning events exceeds 3-4 times that of globally averaged continental GST’s for the 20th century and is significantly higher than that of changes in surface air temperatures (SAT) based on instrumental records in the WCSB. Within this region, GST warming in the 20th century could have been at least partially caused by changes in vegetation cover. The temporary or permanent removal of vegetation, through deforestation, forest fires, and grassland conversion for agriculture occurred in the relatively young provinces of WCSB, during centennial long settlement and development programs. This might have significantly changed the surface properties of the area, since changes in surface albedo affects the radiation budget, while changes in the thermal, moisture and aerodynamic characteristics affect the energy balance. The results of our modelling for typical range of bedrock thermal diffusivities and assumed surface warming history for studied areas in WCSB show that a possible jump in ground surface temperature can easily be interpreted in the FSI results as a gradual warming event of large amplitude and attributed to SAT.

We examined the potential of geothermal energy to supply power and heat for larger communities (population > 10,000) located over the Alberta Basin in the Western Canadian Sedimentary Basin (WCSB). The major cities and seven towns in Alberta examined, with a combined total population of > 2,500,000 people, were scrutinized for their geothermal potential. Depending on T (degrees C) and production rate (kg/s) the range of households that are feasible to be heated is in the 100's to 1000's for produced water > 70 degrees C and flow rates of 30-80 kg/s. These are available in most of the deep foreland basin in western Alberta and in most of the larger population centers, outside the shallow and 'cold' parts of the basin in the east. As space heating is the dominant energy demand in Canada, with single households representing similar to 80% of energy usage, the geothermal heating transition in Alberta would be the best option for municipalities. Power production is feasible in just a few Alberta communities located over the deeper parts of the basin, still requiring > 140 degrees C temperatures and high production rates (> 80 kg/s) due to low efficiency of power plants (some 10%) and economics of the system. The range of the feasible net power production is assessed between single decimals of MW electrical and up to maximum of 2.7 MW in deep hot high production systems.

Poland is situated in a place of contacts between three continental scale geologic structural units: the Precambrian East European Craton (EEC) to the northeast, the Variscan West European Platform (WEP) terranes to the southwest, and the younger Carpathian Alpine arc in the south. The Trans-European suture zone (TESZ) between the EEC and WEP is a deep-seated discontinuity zone reaching down to a depth of about 200 km. The conjunction of all these continental scale geologic units is reflected in the complex tectonic structure of this area. Apart from the complex seismic structure, this area is also associated with pronounced gravity, magnetic and heat flow anomalies. Significant differences exist between heat flow maps of Poland published in recent works, with values reaching 20 to 30 mWm-2. Examples are differences in heat flow based on models that use well log interpreted mineral and porosity content and assigned world averages of rock and fluid thermal conductivities versus ones based on averaging thermal conductivity values measured using borehole cores only. These differences in heat flow between the methods are discussed in the context of their relationship with tectonic age. Also considered are depth differences between lithosphere – asthenosphere boundary (LAB) derived from thermal model vs those that obey seismological constraints. Higher heat flow estimates reaching up to or more than 100 mWm-2, based on conductivity values derived from well-logs, are found to be quite improbable. This likely reason for overestimate of heat flow is discussed.

The relation between heat flow, topography and Moho depth for recent maps of Europe is presented. Newest heat flow map of Europe is based on updated database of uncorrected heat flow values to which paleoclimatic correction is applied across the continental Europe (Majorowicz and Wybraniec 2010). Correction is depth dependent due to a diffusive thermal transfer of the surface temperature forcing, of which glacial–interglacial history has the largest impact. This explains some very low uncorrected heat flow values of 20–30 mW/m2in shallow boreholes in the shields, shallow basin areas of the cratons, and in other areas including orogenic belts where heat flow was likely underestimated due to small depth of the temperature logs. New integrated map of the European Moho depth (Grad et al 2009) is the first high resolution digital map for European plate, which is understood as an area from Ural Mountains in the east to mid-Atlantic ridge in the west, and Mediterranean Sea in the south to Spitsbergen and Barents Sea in Arctic, in the north. For correlation we used the following: onshore heat flow density data with palaeoclimatic correction (5318 locations), topography map (30x30 arc seconds, by Danielson and Gesch 2011) and Moho map by Grad et al (2009), providing longitude, latitude and Moho depth (with resolution of 0.1 degree). Analysis was limited to locations for which datasets were available. The area of continental Europe has been divided into two large domains: Precambrian East European craton and Palaeozoic Platform of the West Europe. In addition, two smaller areas were considered, corresponding to Scandinavian Caledonides and Anatolia. The results obtained reveal significantly different correlations between Moho depth, elevation and heat flow for these regions. For each region detailed analysis of these relations in different elevation ranges are presented. In general, it is observed that Moho depth is more significant for heat flow than elevation. Depending on the region and elevation range, heat flow value is up to two times larger than Moho depth, while relation of heat flow to elevation has much more variability.

Geotherms of four crustal profiles across the Variscan orogen in SW Poland have been constructed to better understand the variation in thermal state of the region. Seismic and drilling data as well as rock sequences in exposed parts of the orogen were used for Wilcza Góra (Sudetic Block), Polkowice–Rudna (Middle Odra Horst), Święciechowa (Wolsztyn–Leszno Horst) and Września (Szczecin–Miechów Synclinorium within TESZ) profiles. The palaeoclimate-corrected surface heat flow map and the heat-production calculations based on literature data enabled the construction of geotherms and estimation of Moho heat flow. Exception is the Polkowice–Rudna profile, where the surface heat flow was calculated using temperature measurements in underground copper mines, and K, U and Th contents and density/heat conductivity measurements in rocks drilled in the Middle Odra Horst were used to calculate geotherm. The basaltic lava migration through the lithospheric mantle and its effect on crustal geotherm in Wilcza Góra (area of Cenozoic alkaline volcanism at ca. 30–18 Ma) was shown to increase slightly both current surface and current Moho heat flow (by ca. 4 mW/m 2 ). The presented approach couples geological and geophysical information and thus differs from standard purely geophysical assessment of lithosphere thermal state. It shows that surface heat flow is enlarged to 84 mW/m 2 by granitic plutons in the upper crust in the Lubin–Polkowice site. Heat flow on the Moho varies from 28 to 34 mW/m 2 in sites located in the Sudetic- /Fore-Sudetic Blocks, Middle Odra Horst and Wolsztyn–Leszno Horst. Locally it may slightly increase because of extraneous heat input by Cenozoic basaltic volcanism, but the values close to 30 mW/m 2 are specific for mantle root of Saxothuringian Zone in SW Poland. Mantle heat flow is 36 mW/m 2 in Września site and supposedly is a manifestation of different nature of lithospheric mantle underlying TESZ.

Low efficiency of turbines used in geothermal power production, along with large power demand for geothermal fluid pumping, limits use of geothermal resources for power production in the Canadian low to mid enthalpy basins. Much larger areas of Canadian sedimentary basins have potential for geothermal direct heating, but use will be dependent on the amortization period of the installation cost as well as the parasitic power demand to maintain large flow rates in injection and production wells. Maximum exergy (kJ/kg) potential for the most perspective geothermal resources in the deeper parts of Canadian basins (150 kJ/kg (0.15 MJ/kg)), are compared to exergy contained by the intrinsic chemical energy in oil, gas and coal (30-35 MJ/kg) that is required to be replaced in order to reduce carbon emissions. The calculated number of geothermal producing doublet well systems, at very high assumed flows of 0.08 m(3)/s (80 L/s), required to replace an average oil producing well in Alberta -WCSB will be > 10. But, such high exergy is available only in the deepest northern parts of the WCSB. (C) 2019 Elsevier Ltd. All rights reserved.

High-resolution 3D seismic P-wave velocity model of Poland (Grad et al., Tectonophysics 666:188–210, 2016) and corrected for paleoclimate heat flow map (Majorowicz and Wybraniec, Int J Earth Sci 100(4):881–887, 2011) gridded to a common mesh are used together with four independent thermal models of the crust and upper mantle to calculate heat flow variation with depth and geotherms. Heat flow at Moho depth are calculated and mapped and both confirm large variability with an elevated mantle heat flow (circa 30–40 mW/m 2 ) in the Paleozoic Platform which is some 10–20 mW/m 2 higher than Moho heat flow in the north-eastern and south-eastern Poland which belong to a variety of tectonic terranes (the oldest Precambrian Craton, younger Cadomian, Trans-European Suture Zone, Carpathians). Temperatures calculated for the crust show consistent pattern: higher temperatures beneath the Paleozoic Platform and lower temperatures beneath the Precambrian and Cadomian units. At 10 km depth this difference is about 150 °C, about 300 °C at 20 km depth, and about 400 °C at 50–60 km. Assuming the calculated isotherm 580 °C as Curie temperature the magnetic crust thickness was determined as 5–10 km only beneath the Polish Basin, circa 20 km in Carpathians, circa 30 km in Sudetes, and 35–40 km beneath the Precambrian and Cadomian units. Such a thick magnetic crust results from a great depth of Curie temperature, thick crystalline crust, and thin sediments. Mantle heat flow variability is mainly correlating with measured surface heat flow and influences geotherms. Calculated thermal LAB depth follows patterns of heat flow and Moho heat flow variability through Poland with thinnest lithosphere in the high surface heat flow and high mantle heat flow areas. Comparison of this thermal LAB depth estimates with seismic data based LAB depth shows general coincidences when Precambrian Craton vs Paleozoic Platform are considered along the P4 seismic experiment data model (circa 190 km depth vs some 90 km depth, respectively). However, significant differences exist in many areas and especially for the SE Poland when compared with map for the whole of Poland compiled from other seismic reported data.

Using a previously published temperature log of the 2363-m-deep borehole Hunt well (Alberta, Canada) and the results of its previous interpretation, the new reconstructions of ground surface temperature and surface heat flux histories for the last 30 ka have been obtained. Two ways to adjust the timescale of geothermal reconstructions are discussed, namely the traditional method based on the a priori data on thermal diffusivity value, and the alternative one including the orbital tuning of the surface heat flux and the Earth's insolation changes. It is shown that the second approach provides better agreement between geothermal reconstructions and proxy evidences of deglaciation chronology in the studied region.

Equilibrium temperature data from shafts in a mining area of SW Poland in the Paleozoic Platform were used for heat-flow calculations. A new technique to calculate paleoclimatic correction for heat-flow determination from single deep temperature data and equilibrium surface temperatures was applied. Elevated surface heat flow of 82–87 mW m−2 and mantle heat flow of some 37–41 mW m−2 were found. This high heat-flow zone spreads from S-W Poland, in the Variscan deformation front, towards the German part of the Polish-German basin. Calculations of geotherms for a variety of heat production models of the crust and upper mantle point to lithosphere–asthenosphere boundary depths of about 80–90 km compared to seismologically determined depths of 90–120 km.

Seismic P- and S-wave velocities of the lower lithosphere and underlying asthenosphere at the SW margin of the East European Craton in northern Poland were obtained with different seismic techniques: seismic refraction, P-residuals of the first arrivals from teleseismic earthquakes, P-wave receiver function, and inversion of the Rayleigh surface wave dispersion curves, the last two using data collected in the passive seismic experiment “13 BB star”. The uniform array consisted of 13 stations deployed in a 120 km in diameter area. Below the depth of 180–220 km a decrease of about 6% of the S-wave velocity is interpreted as a thermal gradient zone corresponding to a lithosphere–asthenosphere transition. The average mantle velocities down to a depth of 300 km beneath the array are relatively high, exceeding values for other Precambrian cratons by 0.1–0.2 km/s, and cannot be modeled by reasonable mantle peridotite compositions in the lithospheric part of the profile. We suggest that significant peridotite anisotropy could explain the misfit between measured and calculated seismic velocities in the lithosphere.

Heat flow high −80 ± 10 mW/m2 in the northern western parts of the Western Canadian foreland basin is in large contrast to low heat flow to the south and east (50 ± 7 mW/m2) of the same basin with the same old 2E09 year’s Precambrian basement and some 200-km-thick lithosphere. Over-thrusted and flat-laying sedimentary units are heated from below by heat flow from the old craton’ crust and low 15 ± 5 mW/m2 mantle contribution. The heat flow vs. radiogenic heat production statistical relationship is not found for this area. To account for this large heat flow contrast and to have 200-km-thick lithosphere, we would need to assume that high heat production layer of the upper crust varies in thickness as much as factor of 2 and/or that the measured heat production at top of Precambrian basement is not representative for deeper rocks. The other explanation proposed before that heat in the basin is redistributed by the regional fluid flow systems driven from high hydraulic head areas close to the foothills of the Rocky Mountains toward low elevation areas to the east and north cannot be explained by observed low Darcy fluid velocities and the geometry of the basin.

The analysis of the warming/cooling patterns from inversion of 94 well temperature logs for the study area of Central Canada shows very high variability (−1 to 3 °C). Analysis of the warming/cooling patterns in last 2–3 centuries indicates that warming has not affected the whole study area and some surface areas have significantly cooled. Regions of large cooling as well as regions of large warming are apparent. Largest cooling is observed in the NE part of the study area while large warming is observed in the area south–east of it in a ridge running NW–SE slightly north of Great Lakes. These patterns go against patterns of land development which is an unlikely factor forcing these regional scale changes derived mainly from the well sites chosen to be in remote and forested areas.

The NE margin of Variscan Orogen in Europe comprises Sudety Mts., Fore-Sudetic Block, Odra Fault Zone and Fore-Sudetic Homocline. The Sudety Mts. together with the located to the NE Fore-Sudetic Block form NE part of the Bohemian Massif. The Variscan crystalline basement is exposed at the surface here. The Odra Fault Zone is situated further to the NE. It is a ca. 20 km wide horst of crystalline basement, hidden beneath relatively thin (< 1000 m) Permian-Mesozoic and Cenozoic sedimentary sequences and is called the Odra Horst in the following. This horst marks the margin of stretching to NE Fore-Sudetic Homocline, in which the crystalline basement is dipping to NE under thickening Permo-Mesozoic strata, covered by few hundred meter thick Cenozoic sedimentary layer (Żelaźniewicz et al. 2016 and references therein). The Odra Horst is possibly a continuation of the Mid German Crystalline High at the NE side of the Bohemian Massif (Dörr et al. 2006).

Models of talik, permafrost and gas hydrate (GH) histories below shallow lakes are investigated and compared to models of Beaufort Mackenzie Basin (BMB) GH occurrences to describe lacustrine inundation effects, which are compared against factors controlling the variations among Mackenzie Delta (MD) permafrost, GH and talik occurrence. Models using a 2–4 °C boundary temperature range indicate that geological setting, specifically underlying lithology and porosity, are the primary controls in talik formation below lakes. Below a lake of any size, where the underlying lithology is sandy it is practically impossible to produce a pervasive talik or to completely degrade significant GH accumulations in response to the boundary condition thermal effects alone. Models predict that talik formation is, in such cases, restricted to the upper few tens of meters below the lake. Permafrost degradation appears common where porosities are <40% and water bottom temperatures reach 2–4 °C, in both marine and lacustrine settings. Where porosities are higher a thin GH stability zone can persist, even where deep taliks have formed.