Miracle-dz/UniFAR-FTUs huggingface dataset:
A decadal oscillation due to the coupling between an ocean circulation model and a thermodynamic sea-ice model

A 3-dimensional, planetary-geostrophic, ocean general circulation model is coupled to a thermodynamic sea-ice model. The thermal coupling takes account of the insulating effect of the ice. A simple approach is taken in the case of the freshwater flux by allowing this to pass through the ice, except that some is used for snow accumulation. It is then modified by salinity rejection/dilution due to freezing/melting. The model has idealized box geometry extending 60° in both latitude and longitude, with a horizontal resolution of 2° and 14 vertical levels. Annual mean surface forcings are used. The coupled system is first spun up using restoring conditions on both surface temperature and surface salinity to reach a steady state which includes ice in the high latitudes. A switch of the surface forcing to mixed boundary conditions (restoring on temperature and flux on salinity) leads to an oscillation of period 17 years in the magnitude of the thermohaline circulation and the ice extent. The oscillation is due to a feedback between ice cover and ocean temperature. Since ice forms only in regions where the ocean loses heat to the atmosphere, the thermal insulation of an increased ice cover makes the ocean warmer. The thermohaline circulation plays a role in transporting this heat polewards, which in turn melts the ice. The heat loss over open water at high latitudes then leads to ice formation and the process repeats itself. Salinity rejection/dilution associated with ice formation/melting is shown to be of secondary importance in this oscillation. Rather, changes in surface salinity are dominated by changes in deep convection and the associated vertical mixing, which are themselves associated with the reduction in surface heat loss due to the insulating effect of the ice. As a consequence the model exhibits the negative correlation between surface salinity and ice extent that is observed in the high latitude North Atlantic
Four Views of a Portion of the North Atlantic Subtropical Gyre

Abstract Data from four cruises to the “β-triangle” centered at 27°N, 32°30′W were smoothed by fitting second-degree polynomials at each of about 30 different density surfaces. The density intervals were Δσp=0.3‰, corresponding to about 50 db intervals in pressure. From the polynomials, determination was made of central values, horizontal derivatives and Laplacians of the fields of pressure, salt, oxygen and dynamic height. In addition, maps of the fits and deviations of each nation from the smoothed fits were produced. From the steady advective diffusive equation and the smoothed fits to the age oxygen and dynamic height fields, the lateral isopycnal diffusivity as estimated to be KH ∼ 0.5 × 103 m2 s−1. Although the salt field was reasonably stable from cruise to cruise, the variability of the baroclinic velocity shear was found to be as large as the baroclinic shear itself. The maps suggest a wobble of the gyre. The standard deviation of the fluctuations at each nation from the smoothed fits, when norma.
The shifting identities and loyalties in Kyrgyzstan: The evidence from the field

The main objective of the ethnic policy of the government of Kyrgyzstan in the post-Soviet era was a consolidation of all people and ethnic groups on the territory of the Republic into the Kyrgyzstani nation. Such a goal is important for any nation that has just gained independence, but for the Kyrgyz Republic it was an especially important task for several reasons. First, the multiethnic composition of the country: in 1991 the Kyrgyzs, or the titular nation of the Republic, constituted roughly 52% of the population, there were around 22% Russians, and the Uzbeks represented 13% of the population. Second, interethnic relations in the Republic were especially tense at the beginning of the 1990s because of the interethnic conflicts in the southern regions of the Republic in 1989 and 1990.1 Third, the Kyrgyzs themselves lacked national cohesiveness and they often defined themselves as members of different tribes or tribal groups with distinct dialects, dress, and political affiliations.
Strain-Dependent Dynamic Properties of Remolded Sand-Clay Mixtures

A series of undrained cyclic torsional simple shear tests using hollow cylindrical torsional shear apparatus was carried out to investigate the dynamic shear moduli and damping properties of clayey specimens with various sand contents and plasticity indices. The clayey soils used were collected from various sites along the coast of west Japan. Among these clayey soils, a clay sample with intermediate plasticity and another with high plasticity were mixed with silica sand at different proportions in order to examine the dynamic properties of sand-clay mixtures. In addition, experiments were carried out on undisturbed and remolded natural clay specimens with various plasticities. The effects of plasticity, loading frequency and confining pressure on the strain dependent normalized shear modulus and damping ratio were examined. Based on the results, empirical correlations for predicting the normalized shear modulus and damping ratio of remolded sand-clay mixtures at various shear strain levels were proposed.
Region-specific network plasticity in simulated and living cortical networks: comparison of the center of activity trajectory (CAT) with other statistics

Electrically interfaced cortical networks cultured in vitro can be used as a model for studying the network mechanisms of learning and memory. Lasting changes in functional connectivity have been difficult to detect with extracellular multi-electrode arrays using standard firing rate statistics. We used both simulated and living networks to compare the ability of various statistics to quantify functional plasticity at the network level. Using a simulated integrate-and-fire neural network, we compared five established statistical methods to one of our own design, called center of activity trajectory (CAT). CAT, which depicts dynamics of the location-weighted average of spatiotemporal patterns of action potentials across the physical space of the neuronal circuitry, was the most sensitive statistic for detecting tetanus-induced plasticity in both simulated and living networks. By reducing the dimensionality of multi-unit data while still including spatial information, CAT allows efficient real-time computation of spatiotemporal activity patterns. Thus, CAT will be useful for studies in vivo or in vitro in which the locations of recording sites on multi-electrode probes are important.
The geomorphic impact of the catastrophic October 1984 flood on the planform of Squamish River, southwestern British Columbia

Small-format aerial photography of Squamish River just prior to and immediately following the October 1984 flood of record forms the basis of a quantitative evaluation of floodplain erosion and construction during this extreme event. Channel changes in 1984 are compared with those determined from sequential aerial photography at various other times since 1947 and associated with less extreme flooding.Depending on the type of river planform, the degree of channel change during the 1984 flood varied from a relatively minor response to a major reorganization of the channel. Despite its large size, the 1984 flood accomplished little more floodplain modification in the meandering and transitional semibraided reaches than had previous smaller floods of similar duration. In general, greater erosion was accomplished here by relatively small but longer duration flood events. In contrast, in the braided reach the 1984 flood caused floodplain erosion and major reorganization of the channel to an extent previously un.
Characterization of hydraulic properties of rocks using probability of fluid-induced microearthquakes

The use of borehole fluid injections is typical for exploration and development of hydrocarbon or geothermal reservoirs. Such injections often induce small-magnitude earthquakes. The nature of processes leading to triggering of such microseismicity is still not completely understood. Here, we consider induced microseismicity, using as examples two case studies of geothermal reservoirs in crystalline rocks and one case study of a tight-gas sandstone reservoir. In all three cases, we found that the probability of induced earthquakes occurring is very well described by the relaxation law of pressure perturbation in fluids filling the pore space in rocks. This strongly supports the hypothesis of seismicity triggered by pore pressure. Moreover, this opens additional possibilities of using passive seismic monitoring to characterize hydraulic properties of rocks on the reservoir scale with high precision.
Geodiversity and Landscape Sensitivity: A Geomorphological Perspective

Abstract The concept of geodiversity has its roots in the need for conservation of fossil localities and other sensitive geological sites, but the field has now widened to embrace concerns at the landscape scale as well as the geoscience input to ecosystem management. The geomorphological component of geodiversity becomes central in these wider contexts and is examined here as a response to the operation of endogenic (magmatic) and exogenic (surface) processes interacting over different time periods. Geomorphological diversity thus reflects the history and dynamics of landforms, and the varying sensitivity of earth materials to surface processes and their perturbations. The process coupling between the landscape elements comprising geodiversity requires a dynamic approach to their management and conservation, with attention to their sensitivities to changes in climate, weather patterns and land management. Geodiversity is also dependent on the scale of enquiry, and the unique features of many iconic landforms may have their greatest significance at the global scale. If geodiversity is to be relevant to scenarios for managing climate change impacts on ecosystems and, therefore, biodiversity, a full understanding of the process interactions with the landscape is required, in parallel with the development of numerical modelling of form and process at a variety of scales.
Solar dimming over the tropical urban region of Hyderabad, India: Effect of increased cloudiness and increased anthropogenic aerosols

[1] The present work examines the multidecadal changes in the net downward shortwave radiation (NDSWR) over the urban region of Hyderabad, India, during the period 1979–2005. The trends in NDSWR and in cloud optical depth (COD) are analyzed over the region using the Modern Era Retrospective-Analysis for Research and Applications (MERRA 2D), which is a newly available data set. The NDSWR exhibits a significant reduction of ∼−20.25 W m−2 for the period 1993–2005; however, it declined at a slower rate (0.468 W m−2) during the period 1979–1992. This reduction translates to −1.56 W m−2 yr−1 in the first period and to −0.04 W m−2 yr−1 in the second. The large difference in the NDSWR trends between the two periods is mainly attributed to the dramatic increase in high COD and in aerosol optical depth (AOD) during the last decade. The total COD over the region suggests an increase of 6.85% during the study period, with the larger increase to be depicted in the high-level clouds (70.86%). Furthermore, retrievals of AOD550 from Microtops-II Sun photometer and Terra–Moderate Resolution Imaging Spectroradiometer (MODIS) show a significant increase of ∼34% and ∼20% during the period 2002–2008 over Hyderabad, respectively. It is demonstrated that aerosols and clouds contribute to the remarkable reduction in NDSWR over Hyderabad in the recent years, thus resulting in a continuous solar dimming over the area. The main role in the decline of NDSWR has been the increase in COD of the high clouds, mainly in monsoon and premonsoon. On the other hand, the dramatic increase in the AOD550 plays an important role in the decrease of NDSWR, mainly in winter. Furthermore, the indirect aerosol effect can modify the cloud formation, albedo, and lifetime, also playing a key role in the aerosol-cloud-radiation interactions.
Are relay ramps conduits for fluid flow? Structural analysis of a relay ramp in Arches National Park, Utah

Abstract Relay ramps associated with overlapping faults are commonly regarded as efficient conduits for fluid flow across potentially sealing intra-reservoir fault zones. The current study demonstrates that structural heterogeneity in the often anomalously wide damage zone of relay ramps may represent potential baffles to intra-ramp fluid flow. A network of ramp-parallel, ramp-diagonal and curved cataclastic deformation bands causes compartmentalization of the ramp studied in Arches National Park, Utah. Harmonic average calculations demonstrate that, although single deformation bands have little or no effect on effective permeability, the presence of even a very small number of low-permeable deformation band clusters could reduce along-ramp effective permeability by more than three orders of magnitude. Thus, although relay zones may maintain large-scale geometric communication, the results of this study demonstrate that caution must be exercised when considering relay ramps as fluid conduits across sealing faults in a production situation. Although relay ramps clearly represent effective migration pathways for hydrocarbons over geological time, the extent to which they conduct fluids in a production situation is more uncertain. Quantitative approaches include adjusting the transmissibility multipliers for faults in reservoir models to allow for increased cross-fault flow. If, however, the effect of internal structural heterogeneity is not taken into consideration, this type of adjustment may lead to gross overestimation of the effect of relay ramps. Sedimentology, stratigraphy, burial history and deformation mechanisms are some of the controlling factors for the formation of such structural heterogeneities.
Diurnal, seasonal, and geomagnetic variations of large field-aligned ion upflows in the high-latitude ionospheric F region

A statistical analysis is carried out by using both the European Incoherent Scatter mainland radar (called EISCAT in the following) and the EISCAT Svalbard radar (ESR) data to investigate the morphology of large field-aligned ion upflows in the high-latitude F region ionosphere, emphasizing its dependence on geomagnetic activity and latitude. By binning data with respect to geomagnetic conditions, significant differences are found between quiet and disturbed periods in the morphology of field-aligned upflows obtained by EISCAT around solar maximum: (1) the occurrence frequency on the nightside is more than 3 times higher during disturbed times than during quiet times; (2) the starting altitude of upflows lowers from 350–400 km under quiet conditions to 200–250 km under disturbed conditions; (3) the magnetic local time (MLT) distribution of the occurrence frequency of upflows exhibits a dawn-dusk asymmetry above 400 km altitude, and it favors the dusk sector under quiet conditions but favors the dawn sector under disturbed conditions; (4) the disturbed-time upflow occurrence frequency exhibits a semiannual variation above 400 km, with higher values around equinoxes. ESR observations during the rising phase of the solar cycle reveal some preliminary features of upflows in comparison to EISCAT observations: (1) the occurrence frequency of upflows on the dayside becomes significantly noticeable at about 200 km altitude, which is lower than that at EISCAT; (2) the upflow occurrence frequency above 400 km exhibits an obvious MLT distribution, with higher values during 0400-1500 MLT, in contrast to 1800–0200 MLT at EISCAT; (3) the upflow occurrence frequency above ESR is higher than that above EISCAT during 0700–1500 MLT but is lower during 2000–0200 MLT. Possible clues on the driving mechanisms of upflows are drawn from these observations.
Toward elucidating the microstructure of warm rainfall: A survey

Quantitative measurement, estimation, and prediction of precipitation remains one of the grand challenges in the hydrological and atmospheric sciences with far‐reaching implications across the natural sciences. Although the roots of current research activity in this topic go back to the beginning of the twentieth century, advances in radar technology and in numerical modeling have provided the impetus for prolific research in the area of cloud and precipitation physics over the last 50 years. As radar rainfall measurements progressively became the staple of hydrometeorological observing systems, cloud and precipitation microphysics emerged as increasingly preeminent areas of research. Here we present a synthesis of the state of the science with respect to the physical dynamics of hydrometeors and, specifically, the transient processes that affect the temporal evolution of rainfall microstructure and that are directly relevant to the quantitative interpretation of radar rainfall measurements and explicit numerical simulations. The focus of our survey is on raindrop morphodynamics (equilibrium raindrop shape and raindrop oscillations), drop‐drop interactions (bounce, coalescence, and breakup), and the dynamical evolution of raindrop size distributions in precipitating clouds.
The conodont animal

A unique specimen of a small, elongate, soft-bodied animal from the Lower Carboniferous of the Edinburgh district, Scotland, is described. The head expands anteriorly into two lobate structures flanking a central lumen; behind this lies a conodont apparatus, apparently in situ, consisting of an aligned set of ramiform elements followed by a pair of ozarkodiniform elements and one of platform elements. From the morphology of the platform elements the animal has been identified as Clydagnathus? cf. cavusformis. Repeated structures which may represent segments are evident in the posterior part of the trunk, which bears a posterior and a caudal fin, each supported by rays. The animal shows similarities to both chordates and chactognaths, but the evidence supports its assignment to a separate phylum, the Conodonta. The function of the conodonts remains equivocal, but it seems more likely that they served as teeth than as internal supports.
Causes and rate-limiting mechanisms of ridge propagation: A fracture mechanics model

All known propagating rifts (PR's) are growing away from shallow ridge axis seafloor. We examine a model for rift propagation in which the ridge axis conduit, like a crack in the lithosphere, propagates in response to a stress concentration at its tip. The stress concentration near the tip which causes progressive failure of the lithosphere is primarily due to excess gravity-spreading stresses associated with anomalously shallow ridge axis along the growing ridge. This stress concentration near the tip is characterized by a stress intensity factor K, which must exceed a threshold value to cause failure of the plate. A remotely applied tensile stress would make a positive contribution to K but would act equally on both ridge segments and not favor the propagation of either. The pressure in the crack may, depending on its distribution, make either a positive or negative contribution to K. For a high enough propagation rate, viscous flow induced suction due to the growth of the ridge axis as well as the reduced vertical flow near the PR tip would make K < 0. This simple model thus includes a mechanism to control the speed of propagation and is consistent with the axial morphology of the spreading segment associated with the well-studied 95.5°W PR of the Galapagos spreading center. Analytical solutions for the contribution to the stress intensity factor of viscous forces resisting ridge axis growth and causing the PR axial topography are consistent with the observed propagation rate for asthenosphere viscosities of about 1019 Pa s (1020 P). We also examine a more general model of a ridge-transform-ridge system on the basis of energy conservation. In terms of energetics this more general model reduces to that of a single propagating ridge axis crack when both the work done by forces driving propagation and the viscous dissipation due to forces resisting propagation are generated along the growing ridge axis. However, the more general model also includes mechanisms that may stop ridge propagation. Propagation will stop either when the energy needed for transform migration is larger than that available for ridge axis growth or when the strain energy absorbed at the dying ridge axis is comparable to that released at the growing ridge axis, i.e., if the stress intensity factors for both ridge axes are similar. Both of these possibilities may occur when the propagating rift completely propagates through a ridge segment as at 85°W in the Galapagos. Finally, in this model the slight systematic differences in ridge axis orientation of the growing and dying ridges are a consequence rather than a cause of ridge propagation.
Interaction between the Chile Ridge and Chile Trench: Geophysical and geothermal evidence

Geophysical and geothermal data are examined from the three southernmost sections of the Chile Ridge, starting at 44°S and continuing south to the triple junction of the Nazca, Antarctic, and South America plates at 47°S. These sections represent three progressively younger stages in a ridge-trench collision event, corresponding to 3 m.y. before the collision, 1 m.y. before the collision, and culminating in an ongoing collision at the triple junction. Magnetic and bathymetric data across the Chile Rise indicate that there is little change in the configuration of the spreading center as the ridge approaches and then collides with the trench. In the collision zone a “normal” looking rift valley can be traced for 40 km before it disappears beneath the toe of the landward trench slope. There is no evidence for the complex pattern of ridge jumps and spreading center rotations that occurred when the Pacific-Farallon spreading center collided with North America. In contrast, the overriding plate is greatly affected by the ridge collision. The landward trench slope steepens and narrows as the collision zone is approached. At the southern end of the collision zone a ridge associated with the Taitao Fracture Zone is colliding with the trench and may be in the process of being obducted onto the landward trench slope. Geothermal measurements were made along three transects of the margin, corresponding to the time 3 m.y. before the collision, during the collision, and 6 m.y. after the collision. The heat flow measurements in the collision zone document a large pulse of heat associated with the subduction of the ridge: Values as high as 345 mW/m2 were recorded on the lower trench slope. A prominent bottom-simulating reflector (BSR) observed over a wide area of the landward trench slope north of the triple junction, and, more locally, south of the triple junction, is used to expand the grid of heat flow observations. Excellent agreement is found between measured heat flow and estimates of heat flow based on the depth to the BSR. The heat flow measurements compare favorably with a theoretical model assuming conductive heat flow. We estimate that the accretionary prism has been substantially removed in the collision zone and conclude that the landward trench slope is undergoing an episode of rapid tectonic erosion. Periodic ridge collisions in the past may account for the apparent truncation of the Andean forearc region.