Large, multilevel magmatic intrusions as an important carbon degassing source in a nonvolcanic setting

This study revisits an old concept in meteorology ‐ level of neutral buoyancy (LNB). The classic definition of LNB is derived from the parcel theory and can be estimated from the ambient sounding (LNB_sounding) without having to observe any actual convective cloud development. In reality, however, convection interacts with the environment in complicated ways; it will eventually manage to find its own effective LNB and manifests it through detraining masses and developing anvils (LNB_observation). This study conducts a near‐global survey of LNB_observation for tropical deep convection using CloudSat data and makes comparison with the corresponding LNB_sounding. The principal findings are as follows: First, although LNB_sounding provides a reasonable upper bound for convective development, correlation between LNB_sounding and LNB_observation is low suggesting that ambient sounding contains limited information for accurately predicting the actual LNB. Second, maximum mass outflow is located more than 3 km lower than LNB_sounding. Hence, from convective transport perspective, LNB_sounding is a significant overestimate of the “destination” height level of the detrained mass. Third, LNB_observation is consistently higher over land than over ocean, although LNB_sounding is similar between land and ocean. This difference is likely related to the contrasts in convective strength and environment between land and ocean. Finally, we estimate the bulk entrainment rates associated with the observed deep convection, which can serve as an observational basis for adjusting GCM cumulus parameterization.

Spreading of salt structures in the Gulf of Mexico

Infant affective behavior, temperament and autonomic patterning

Transient dike propagation and arrest near the level of neutral buoyancy

Terrestrial heat flow, Q=K×ΔT/ΔZ cal/cm2 sec has been determined at 51 localities (39 on land and 12 in the sea) in and around the Japanese Islands. The average values of observed heat flow in land and sea are 1.53µ cal/cm2sec and 1.48µcal/cm2sec respectively. These value do not differ greatly from the world’s averages. The outstanding features of the heat flow distribution are as follows:a) High heat flow region (Q>2.0µcal/cm2sec) exists in the Inner Zone of the Honshu Arc. This region of high heat flow is more distinct in the northeastern Japan than in the southwestern Japan.b) The High heat flow region seems to extend, through the Fossa Magna area, down to the Izu-Mariana Arc.c) It is also probable that a similar high heat flow zone exists in the inner side of the Kurile Arc.d) These zones of high heat flow precisely coincide with the zones of the Cenozoic orogeny in the area concerned.e) Far off the coast of the northeastern Japan, the area at about 150° E may be a high heat flow region.f) Low heat flow (Q<1.0µcal/cm2sec) prevails in the Pacific coast side of the northeastern Japan and in the oceanic area directly east of it, including the area of the Japan Trench.g) The region bounded by the above mentioned high and low heat flow regions has heat flow which is more or less normal. Based on these measurements, a « steady state ” temperature distribution in the crust has been calculated for each of the above regions of high, low and intermediate heat flow, and it was found that there is a large temperature differences between the bottom of the crust of the high and low heat flow regions: the temperature at the Moho boundary in the high heat flow regions should be as high as some 800∼1000°C (d=27 km), whereas that under the low heat flow region should be only about 200°C (d=23 km). The high general temperature at the Moho under the high heat flow region seems to favor a production of magma in the upper mantle. Calculated Moho temperatures disfavor the hypothesis that the Moho boundary is due to phase transition.

Abstract. Although it is generally accepted that the level of neutral buoyancy (LNB) is only a coarse estimate of updraft depth, the LNB is still used to understand and predict storm structure in both observations and modeling. This study uses case studies to quantify the variability associated with using environmental soundings to predict detrainment levels. Nine dual-Doppler convective cases were used to determine the observed level of maximum detrainment (LMD) to compare with the LNB. The LNB for each case was calculated with a variety of methods and with a variety of sources (including both observed and simulated soundings). The most representative LNB was chosen as the proximity sounding from NARR using the most unstable parcel and including ice processes. The observed cases were a mix of storm morphologies, including both supercell and multicell storms. As expected, the LMD was generally below the LNB, the mean offset for all cases being 2.2 km. However, there was a marked difference between the supercell and non-supercell cases. The two supercell cases had LMDs of 0.3 km and 0.0 km below the LNB. The remaining cases had LMDs that ranged from 4.0 km below to 1.6 km below the LNB, with a mean offset of 2.8 km below. Observations also showed that evolution of the LMD over the lifetime of the storm can be significant (e.g., &gt;2 km altitude change in 30 min), and this time evolution is lacking from models with coarse time steps, missing significant changes in detrainment levels that may strongly impact the amount of boundary layer mass transported to the upper troposphere and lower stratosphere.

The Chingshui geothermal area southwest of the Ilan plain is identified as a western extension of the Okinawa Trough in the northern Taiwan subduction system. Numerous geophysical, geological and geochemical investigations have been conducted since the 1970s by the Industrial Technology Research Institute, the Chinese Petroleum Corporation of Taiwan and the National Science Council of Taiwan. These studies indicated that the Chingshui stream is one of the largest geothermal areas for electricity generation in Taiwan. However, the power generation efficiency has not met initial expectations. Magnetotelluric (MT) data analyses show that the Chingshui geothermal region is a geologically complex area. A full three-dimensional (3D) inversion was therefore applied to reprocess the MT data and provide the detailed electrical structure beneath the Chingshui geothermal region. The 3D geoelectrical model displays an improved image that clearly delineates the Chingshui geothermal system geometry. Two conductive anomalies are imaged that possibly indicate high potential areas for geothermal energy in the Chingshui geothermal system. One of the potential areas is located in the eastern part of the Chingshui Fault at shallow depths. A significant conductive anomaly is associated with high heat flow and fluid content situations southwest of the geothermal manifest area at depth. A higher interconnected fluid indicates that this area contains the highest potential for geothermal energy in the Chingshui geothermal system.

Heat flow models across the Trans-European Suture Zone in the area of the POLONAISE’97 seismic experiment

We present a new 3‐D S wave velocity model of the northeast (NE) China from the joint inversion of the Rayleigh wave ellipticity and phase velocity at 8–40 s periods. Rayleigh wave ellipticity, or Rayleigh wave Z/H (vertical to horizontal) amplitude ratio, is extracted from both earthquake (10–40 s) and ambient noise data (8–25 s) recorded by the NorthEast China Extended SeiSmic Array with 127 stations. The estimated Z/H ratios from earthquake and ambient noise data show good consistency within the overlapped periods. The observed Z/H ratio shows a good spatial correlation with surface geology and is systematically low within the basins. We jointly invert the measured Z/H ratio and phase velocity dispersion data to obtain a refined 3‐D S wave velocity model beneath the NE China. At shallow depth, the 3‐D model is featured by strong low‐velocity anomalies that are spatially well correlated with the Songliao, Sanjiang, and Erlian basins. The low‐velocity anomaly beneath the Songliao basin extends to ~ 2–3 km deep in the south and ~5–6 km in the north. At lower crustal depths, we find a significant low‐velocity anomaly beneath the Great Xing'an range that extends to the upper mantle in the south. Overall, the deep structures of the 3‐D model are consistent with previous models, but the shallow structures show a much better spatial correlation with tectonic terranes. The difference in sedimentary structure between the southern and northern Songliao basin is likely caused by a mantle upwelling associated with the Pacific subduction.

The thermal structure of East Asian continental lithosphere is critical for understanding its diffuse and variable intracontinental deformation in the Cenozoic. Here, we present a three‐dimensional model of the lithospheric thermal structure of East Asia, using the latest thermal conductivity and radiogenic heat production measurements in mainland China. The results show great lateral heterogeneity of lithospheric temperature. The crust of orogenic belts such as the Tibetan Plateau, the Mongolia Plateau, the Tian Shan orogen, and Northeast China, is generally characterized by high temperatures. Other regions of high crustal temperatures include the southeast coast of China and Lake Baikal. The heat sources for the crust also vary. In the Tibetan Plateau, high crustal temperatures result mainly from radiogenic heat production within the thick crust, indicating the influence of continental collision. However, high heat flow from the upper mantle is the main cause of high surface heat flow in the eastern part of East Asia, where the relatively thin lithosphere and hot asthenosphere is related to the subduction of the Pacific Plate. This subduction is also responsible for Cenozoic continental volcanoes in East Asia.

Tropical deep convective clouds are important drivers of large‐scale atmospheric circulation representing the main vertical transport pathway through the depth of the troposphere for heat, momentum, water, and chemical species. The strength and depth of this transport are impacted by the convective updraft size and intensity that are driven by buoyancy, dynamical forcing, and mixing of environmental air, that is, entrainment. In this study, we identify tropical deep convective systems with well‐defined forward anvils using Atmospheric Radiation Measurement (ARM) ground‐based profiling radars, at three ARM fixed sites in the Tropical Western Pacific (TWP; i.e., Manus, Nauru, and Darwin) and three ARM Mobile Facility deployments in Niamey, Niger; Gan Island, Maldives; and Manacapuru, Brazil. We use the difference between the level of neutral buoyancy (LNB) and the level of maximum detrainment (LMD) as a proxy for the effective bulk convective entrainment (εproxy). The LNB, the theoretical height that a parcel raised above the level of free convection would reach with no mixing, is calculated based on preconvection radiosonde measurements using parcel theory. The LMD is the height of the maximum reflectivity observed in forward anvil clouds by profiling radars. Deep convective systems over the TWP show higher LNBs that extend to 16.3 km on average and largerεproxy(median value of LNB minus LMD up to 6.5 km) compared to their continental counterparts in the Amazon and West Africa. Oceanic conditions show larger convective available potential energy (CAPE) coupled with higher moisture at low levels, which favors largerεproxy. In contrast, continental cases initiate and develop, under high convective inhibition, steeper environmental lapse rate, and high wind shear conditions, which show smaller offset between LNB and LMD. Deep convective cases that promote significant cold pools at the surface experience lessεproxy. Using a Random Forest regression algorithm, CAPE is associated with the highest feature importance score for predicting convectiveεproxy, followed by low‐level relative humidity. For continental cases, the low‐level wind shear also indicates higher importance.

We report 66 new heat flow and 24 new heat production measurements from the Sirt Basin, a late Jurassic‐Miocene sedimentary depression in north central Libya underlain by late Proterozoic basement. Heat flow determinations were made using bottom hole temperatures from oil wells and thermal conductivity measurements from drill core and cuttings; heat production measurements come from core samples of basement rock. Heat flow is fairly uniform throughout the basin, with a mean of 72 ± 9 (s. d.) mW m−2. It is not clear if heat flow from the Sirt Basin is elevated as a consequence of its origin as a late Mesozoic rift. The difference between the mean basin heat flow and the global mean heat flow from tectonically undisturbed late Proterozoic terrains (55 ± 17 mW m−2) is 17 mW m−2, but this difference lies within the uncertainties associated with these mean heat flow estimates. If heat flow from the Sirt Basin is elevated, it could be caused by enhanced crustal heat production and need not be attributed to thermal alteration of the lithosphere related to basin formation. Mean crustal heat production is 3.9 ± 2.1 μW m−3, 1/2 to 3 times greater than surface heat production in other Proterozoic terrains in Africa. From west to east, the pattern of heat flow across northern Africa is characterized by high (80–110 mW m−2) heat flow throughout most of northwestern Africa, normal to perhaps slightly elevated heat flow in the Sirt Basin, low to normal (35–55 mW m−2) heat flow in Egypt inboard of the Red Sea, and high heat (75–100 mW m−2) flow along the Red Sea. High heat flow near the Red Sea and in northwestern Africa along the Mediterranean coast can be readily attributed to Cenozoic tectonic activity, but high heat flow in the Paleozoic Sahara basins of southern Algeria is harder to understand within the tectonic framework of northern Africa. A possible explanation, advanced previously, is that elevated heat flow in the Sahara basins arises from a regional thermal anomaly within the north African lithosphere. If that explanation is correct, then the heat flow distribution in the Sirt Basin and in Egypt away from the Red Sea suggests that the postulated lithospheric thermal anomaly does not extend beyond the Sahara basins to the east.

Positive heat flow anomaly in the Carpathian basin

SUMMARY Krafla is an active volcanic field and a high-temperature geothermal system in northeast Iceland. As part of a program to produce more energy from higher temperature wells, the IDDP-1 well was drilled in 2009 to reach supercritical fluid conditions below the Krafla geothermal field. However, drilling ended prematurely when the well unexpectedly encountered rhyolite magma at a depth of 2.1 km. In this paper we re-examine the magnetotelluric (MT) data that were used to model the electrical resistivity structure at Krafla. We present a new 3-D resistivity model that differs from previous inversions due to (1) using the full impedance tensor data and (2) a finely discretized mesh with horizontal cell dimensions of 100 m by 100 m. We obtained similar resistivity models from using two different prior models: a uniform half-space, and a previously published 1-D resistivity model. Our model contains a near-surface resistive layer of unaltered basalt and a low resistivity layer of hydrothermal alteration (C1). A resistive region (R1) at 1 to 2 km depth corresponds to chlorite-epidote alteration minerals that are stable at temperatures of about 220 to 500 °C. A low resistivity feature (C2) coincides with the Hveragil fault system, a zone of increased permeability allowing interaction of aquifer fluids with magmatic fluids and gases. Our model contains a large, low resistivity zone (C3) below the northern half of the Krafla volcanic field that domes upward to a depth of about 1.6 km b.s.l. C3 is partially coincident with reported low S-wave velocity zones which could be due to partial melt or aqueous fluids. The low resistivity could also be attributed to dehydration and decomposition of chlorite and epidote that occurs above 500 °C. As opposed to previously published resistivity models, our resistivity model shows that IDDP-1 encountered rhyolite magma near the upper edge of C3, where it intersects C2. In order to assess the sensitivity of the MT data to melt at the bottom of IDDP-1, we added hypothetical magma bodies with resistivities of 0.1 to 30 Ωm to our resistivity model and compared the synthetic MT data to the original inversion response. We used two methods to compare the MT data fit: (1) the change in r.m.s. misfit and (2) an asymptotic p-value obtained from the Kolmogorov–Smirnov (K–S) statistical test on the two sets of data residuals. We determined that the MT data can only detect sills that are unrealistically large (2.25 km3) with very low resistivities (0.1 or 0.3 Ωm). Smaller magma bodies (0.125 and 1 km3) were not detected; thus the MT data are not sensitive to small rhyolite magma bodies near the bottom of IDDP-1. Our tests gave similar results when evaluating the changes in r.m.s. misfit and the K–S test p-values, but the K–S test is a more objective method than appraising a relative change in r.m.s. misfit. Our resistivity model and resolution tests are consistent with the idea of rhyolite melt forming by re-melting of hydrothermally altered basalt on the edges of a deeper magma body.

Fractal characteristics of Upper Cretaceous lacustrine shale from the Songliao Basin, NE China