Miracle-dz/UniFAR-FTUs huggingface dataset:
Nutrient fluxes during extended blooms of Arctic ice algae

Estimates of nutrient demand by dense mats of ice algae in the high Arctic indicate that substantial nutrient fluxes are necessary to satisfy the observed growth over the 2-month bloom. In our study area, Barrow Strait, the quantity of nutrients in the surface-mixed layer is about 3–10 times greater than estimates of total demand during the bloom, and nutrient fluxes in the water column are estimated to be of the same order of magnitude as algal demand. The fluxes in the water column are predicted to vary by more than an order of magnitude over the fortnightly tidal cycle, assuming that fluxes depend upon the strength of tidal currents and the vertical nutrient gradients. In the latter half of the bloom, when biomass levels are high, it appears that established populations of ice algae may experience cyclic conditions of nutrient limitation during neap tides when nutrient fluxes are minimal. Contributions from regeneration and brine exclusion from the ice sheet appear to satisfy only a portion of the bloom's total requirement for nutrients.
Possibility of Postliquefaction Flow Failure due to Seepage

This study examines the postliquefaction flow failure mechanism, in which shear strain develops due to seepage upward during the redistribution of excess pore water pressure after an earthquake. The mechanism is addressed as both a soil element and a boundary value problem. Triaxial tests that reproduce the stress state of a gentle slope subjected to upward pore water inflow were performed, with the results showing that shear strain can increase significantly after the stress state reaches the failure line. In addition, when subject to equivalent volumetric strain, shear strain is considerably larger in loose sand conditions than in dense sand. Compared with consolidated and drained test results, the dilatancy coefficient β, which indicates the rate of dilation, is the same as that obtained from pore water inflow tests. Torsional hollow cylinder tests were also performed to ascertain the limit of dilation of sand specimens. It was found that the β values are nonlinear in behavior. In addition, a postliquefaction flow failure mechanism based on one-dimensional consolidation theory and shear deformation behavior as a result of pore water inflow is proposed.
Determination of diapycnal diffusion rates in the upper thermocline in the North Atlantic Ocean using sulfur hexafluoride

[1] The apparent diapycnal diffusivity below the wind-driven surface mixed layer of the ocean was determined in an anticyclonic eddy in the eastern North Atlantic using sulfur hexafluoride (SF6) tracer data collected in June 1998. In this tracer experiment the downward penetration of SF6 was measured for 3 weeks following the deliberate injection of SF6 in the surface mixed layer. The resulting data were used to constrain the one-dimensional Fickian diffusion model to estimate the diapycnal diffusivity. The model also includes the lateral diffusion component so that it can more accurately represent the time evolution of the SF6 concentrations along the isopycnal surface. This affects the estimation of the diapycnal diffusivity. For the upper thermocline immediately below the surface mixed layer we estimated the diapycnal diffusivity for the 3 week period as 0.3 ± 0.2 cm2 s−1 at a buoyancy frequency of 8.2 cph.
Les complexes volcaniques Rhyolithiques quaternaires d'Anatolie centrale (Göllü Dag et Acigöl, Turquie) : Genèse, instabilité, contraintes environnementales

During the Quaternary, important and rapid environmental changes occurred in central Anatolian in relation with calco-alcaline volcanism. This volcanic activity generated two large rhyolitic complexes integrating calderas, several pyroclastic deposits and lavic extrusions interstratified with various detritic formations. Activity of the Gollu Dag and the Acigol complexes lasted respectively from the lower Pleistocene until the middle Pleistocene, and from the middle Pleistocene until the upper Pleistocene. Results presented here allow i) to evidence the Gollu Dag caldera for the first time, ii) to define the extension of the Acigol caldera according to new data, and iii) to reconstruct the successive phases in the evolution of both complexes. These complexes present three main types of activity : pre-, syn-, and post-caldera, each timing being responsible for various environmental changes related to different pyroclastite deposition characteristics (volume, types, dynamics, .). Syn-caldera activity induced the most important environmental changes, which affected palaeogeography and palaeohydrology. During post-caldera activity, changes are less important and concern the extrusion of local rhyolitic domes, in the frame of an original model of extrusion presenting phreatomagmatism associated with annular obsidian dykes, pelean eruptions and rhyolitic extrusion. During Palaeolithic and Neolithic times, mining and chopping of obsidian caused the noticeable presence and activity of human societies. In comparison with syn- caldera activities, the volumes of pyroclastites deposited during the post-caldera episodes were reduced, so that they are interbedded within alluvial and colluvial Pleistocene formations containing also some obsidian artefacts. This context offers interesting sequences where tephra layers, paleosol, reworked formations and archaeological (Palaeolithic) industries, give opportunities to set a quite precise chronology and to identify palaeogeographical changes. This study allows also to analyse factors controlling environmental changes in a volcanic region and to correlate these changes using a tephrostratigraphical framework detailed here for the first time.
Sedimentation in ice-dammed Hazard Lake, Yukon

"Hazard Lake," located in Kluane National Park, the Yukon, is an ice-dammed lake formed in 1966 by the surge of the Steele Glacier. Since 1975 it has drained annually by means of a subglacial tunnel. During July 1979, observations were made of lake processes before drainage and of sections described in the lake bottom after drainage. Three facies associations are believed to represent prelake, stable lake, and annual draining phases. Gravel commonly found at the base of sections represents deposition in a braided fluvial system prior to 1966. Lake sediments deposited between 1966 and 1975 are dominantly graded laminated silt deposited by turbid underflow from the major inflow stream. Lamination is probably caused by diurnal underflow events or daily variation in strength of underflow. No "winter" clay component of varved sediments is observed. During drainage a regressive sequence is deposited as the lake level drops, with sand-dominated sediments overlapping laminated silt where the main inflow stream en.
Single-Scattering Albedo and Radiative Forcing of Various Aerosol Species with a Global Three-Dimensional Model

Global distributions of the aerosol optical thickness, Angstrom exponent, and single-scattering albedo are simulated using an aerosol transport model coupled with an atmospheric general circulation model. All the main tropospheric aerosols are treated, that is, carbonaceous (organic and black carbons), sulfate, soil dust, and sea salt aerosols. The simulated total aerosol optical thickness, Angstrom exponent, and single-scattering albedo for mixtures of four aerosol species are compared with observed values from both optical ground-based measurements and satellite remote sensing retrievals at dozens of locations including seasonal variations. The mean difference between the simulation and observations is found to be less than 30% for the optical thickness and less than 0.05 for the single-scattering albedo in most regions. The simulated single-scattering albedo over the Saharan region is, however, substantially smaller than the observation, though the standard optical constant of soil dust is used in this study. The radiative forcing by the direct effect of the main tropospheric aerosols is then estimated. The global annual mean values of the total direct radiative forcing of anthropogenic carbonaceous plus sulfate aerosols are calculated to be 20.19 and 20.75 W m22 under whole-sky and clear-sky conditions at the tropopause, respectively.
On the multiplicity of nonnegative solutions with a nontrivial nodal set for elliptic equations on symmetric domains

We consider the Dirichlet problem for a class of fully nonlinear elliptic equations on a bounded domain $\Omega$. We assume that $\Omega$ is symmetric about a hyperplane $H$ and convex in the direction perpendicular to $H$. Each nonnegative solution of such a problem is symmetric about $H$ and, if strictly positive, it is also decreasing in the direction orthogonal to $H$ on each side of $H$. The latter is of course not true if the solution has a nontrivial nodal set. In this paper we prove that for a class of domains, including for example all domains which are convex (in all directions), there can be at most one nonnegative solution with a nontrivial nodal set. For general domains, there are at most finitely many such solutions.
The Mw 7.8, 2001 Kunlunshan earthquake: Extreme rupture speed variability and effect of fault geometry

[1] By analyzing body wave seismograms, we show that the rupture speed on the Main Kunlun Fault during the Mw 7.8 2001 Kunlunshan, Tibet, earthquake was highly variable and the rupture process consisted of three stages. In the first stage, the rupture accelerated from rest to an average speed of 3.3 km/s over a distance of 120 km. The rupture then propagated for another 150 km at an apparent rupture speed exceeding the P wave speed. In the final stage, the earthquake fault bifurcates, and the rupture front slowed down. The region of highest rupture velocity is found to coincide with the region of highest fault slip, has the longest slip duration, and is where off-fault ground cracking is observed in the field. Stress drops are found to be higher in regions of higher rupture speeds. The greatest concentration of aftershocks is located near the fault bifurcation zone and hence coincides with the region of highest fault slip, highest stress drop and highest rupture velocity. The fault width is no more than 10 km in most places and is about 20 km in the region of highest slip. This narrow fault width is attributed to the fact that crust below this depth is sufficiently warm not to permit brittle failure to occur. The remarkable similarity of this earthquake with the 1906 California earthquake, in spite of occurring in very different tectonic regimes, is discussed.
Application of Raman spectroscopy to distinguish adularia and sanidine in drill cuttings from the Ngatamariki Geothermal Field, New Zealand

Adularia and sanidine are polymorphs of potassium feldspar commonly present in felsic, hydrothermally altered volcanic deposits. Sanidine is a high-temperature volcanic mineral, whereas adularia forms post deposition by hydrothermal processes. Petrographically differentiating between these polymorphs in hydrothermally altered volcanic rocks may be utilised to distinguish geological units as well as provide insights into fluid–rock interactions. However, petrographic identification may be difficult or not possible in fine-grained drill cuttings. Here, polymorphic-sensitive, Raman spectroscopy and electron microprobe analyses are utilised to characterise adularia and potential sanidine in drill cuttings from the Ngatamariki Geothermal Field, Taupo Volcanic Zone, New Zealand. Differences in Raman spectra are capable of distinguishing between adularia and sanidine whether using peak positions or principal component analysis. All the Ngatamariki Geothermal Field potassium feldspars analysed by Raman spectroscopy were found to be adularia, as expected, with typical high K, low Ca compositions between Or94 and Or99 confirmed with electron microprobe analyses. This applied approach demonstrates that Raman spectroscopy is a fast and effective method for lending confidence to adularia and sanidine identification, which can be utilised in geothermal fields worldwide.
Rock Glaciers on Prins Karls Forland. II: GPR Soundings and the Development of Internal Structures

Internal structures in four rock glaciers in the continuous permafrost zone on the island of Prins Karls Forland, western Svalbard (78°50′N,10°30′E), were studied utilizing ground penetrating radar (GPR). A comparative study was performed on the Broggerbreen rock glacier close to Ny-Alesund, about 50 km to the east. The bedrock interface was visible on some GPR profiles. Further, the length profiles revealed a system of reflectors that was comparable between the different rock glaciers. A layering structure parallel with the surface was visible in the upper part of the talus cones above the rock glaciers, while further down towards the rock glaciers these reflectors started to slant up against the surface slope. This inclination of the layers prevailed towards the fronts, although a more irregular pattern was discernible in the frontal part of some of the rock glaciers. The layering structure is probably formed by mass movements of higher magnitude, covering either snow patches or the active layer above supersaturated permafrost. We suggest that the structural development along the rock glaciers is caused by an accumulation gradient along the talus-cone/rock-glaciers system, causing differences in vertical velocity along a layer. Copyright © 2000 John Wiley & Sons, Ltd. RESUME Les structures internes de quatre glaciers rocheux de la zone du pergelisol continu sur l'ile du Prins Karls Forland, Svalbard occidental (78°50′N,10°30′E), ont ete etudiees en utilisant un radar dont les ondes penetrent le sol (GPR). Une etude comparative a ete realisee sur le glacier rocheux de Broggerbreen, environ 50 km a l'est de Ny-Alesund. Le sommet du bedrock etait visible sur quelques profils GPR. En outre, les profils longitudinaux ont montre un systeme de reflecteurs comparable dans les differents glaciers rocheux. Une structure en couches paralleles a la surface a ete vue a la partie superieure des cones d'eboulis surmontant les glaciers rocheux, tandis que, plus bas, ces reflecteurs s'inclinent dans une direction opposee a la pente de surface. Cette inclinaison des couches domine vers les fronts, quoique une disposition plus irreguliere soit perceptible dans la partie frontale de quelques glaciers rocheux. Cette structure en couches resulte probablement de mouvements de masse de grande importance, recouvrant a la fois des plaques de neige ou de couche active situees au dessus du pergelisol supersature. Nous suggerons que le developpement structural le long des glaciers rocheux est du a une pente d'accumulation le long du systeme cone-glacier rocheux determinant des differences de vitesses verticales suivant une couche. Copyright © 2000 John Wiley & Sons, Ltd.
Dependence of apparent optical properties on solar altitude: Experimental results based on mooring data collected in the Sargasso Sea

The in situ variability of the vertical attenuation coefficient for downward irradiance (Kd) and radiance reflectance (RL) in response to changing solar altitude has been investigated. Observations were made 18 times per day from a fixed position mooring deployed in the Sargasso Sea, The mooring included instrumentation to measure spectral downwelling irradiance (Ed) and spectral upwelled radiance (Lu) at 15- and 35-m depths. Time series data used for our analysis represent conditions of low, almost constant concentration of chlorophyll-like pigments in the water and sunny or partly cloudy sky conditions. During sunny days the dominant component of the observed diel variability of the apparent optical properties (AOPs) was caused by the variable solar altitude. The statistical analysis performed on the data indicates a significant correlation between Kd and the cosine of the zenith angle of the direct solar beam after refraction at the air/water boundary (μ). These changes were wavelength dependent; Kd at 412, 443, 490, 510, and 555 nm decreased by 18–30%, while Kd at 665 and 683 nm increased by more than 50% when solar altitude increased from about 17° to 60° (i.e., when μ increased from 0.69 to 0.93). The vertical attenuation coefficient for photosynthetically available radiation (KPAR) decreased by about 25%. The daily amplitudes of similar changes in RL at the blue/green light were much smaller, up to about 4 to 8% at 412, 443,490, and 510 nm and 11% at 555 nm. However, at 665 and 683 nm, RL changed by more than 100%. This large increase of RL and decrease of Kd at 665 and 683 nm with Sun altitude (with μ) can be explained by the fact that the light field at red wavelengths was strongly affected by inelastic processes such as Raman scattering and natural fluorescence. Remote-sensing techniques rely on the interpretation of reflectance and upwelled radiance ratios. We observed up to 8% changes in reflectance ratios and up to 17% changes in upwelling radiance ratios during the day. These maximum changes were observed for the ratios including Lu or RL at 555 nm, which were affected by inelastic scattering of light. Although our data illustrate the dependence of AOPs on the Sun altitude on a daily timescale, similar relationships are expected to be of importance on a seasonal scale and with latitude.
Characterizing the low‐altitude magnetic belt at Venus: Complementary observations from the Pioneer Venus Orbiter and Venus Express

Using Venus Express, Zhang et al. (2012b) identified strong magnetic field enhancements at low altitudes over the north polar region of Venus as giant flux ropes. Strong fields at low altitudes were also observed during the Pioneer Venus Orbiter mission, but at low latitudes near the subsolar and midnight regions. We examine the possibility that the Venus Express observations are not giant flux ropes, but part of a low‐altitude magnetic belt that builds up in the subsolar region, passes over the terminator, and extends to the nightside. Our analysis indicates the magnetic belt is dominantly horizontal over the dayside and gains a radial component nightward. The peak magnetic field strength of the belt and the altitude at which it peaks also varies around the planet, with the lowest altitude and strongest field strength in the subsolar region, consistent with the idea of the belt forming on the dayside. Zhang et al. (2012b) also noted the fields in the polar region had a bias in the +By direction in Venus Solar Orbital coordinates. The multifluid magnetohydrodynamic simulation we present shows an asymmetry in the plasma flow from the subsolar region to the poles due to the oxygen ion and proton mass ratio. This causes the magnetic field to preferentially accumulate in the north for a +By interplanetary magnetic field direction, providing an explanation for this bias.
Arctic oscillation and Arctic sea‐ice oscillation

The variability of the sea‐ice cover in the Arctic and subpolar regions associated with the Arctic Oscillation (AO) was investigated using historical data from 1901 to 1997. Unrotating principal component analyses (or empirical orthogonal functions, EOFs) were applied to demeaned, normalized sea‐level pressure (SLP), surface air temperature (SAT), and sea‐ice area (SIA) for the periods 1901–97 and 1953–97. The leading SLP EOF mode is the AO. The leading SIA EOF mode is named the Arctic Sea‐Ice Oscillation (ASIO), which accounts for 41% of the total variance for the period of 1901‐1995. This dominant ASIO is AO‐related; its spatial and temporal patterns are consistent with the leading modes of SLP and SAT, and with the total arctic sea‐ice anomalies. The second SIA mode is North Atlantic Oscillation (NAO)‐related because sea‐ice anomalies in the Labrador Sea region and the Greenland Sea region are out of phase. During the last three decades, the arctic sea ice has significantly decreased, which may be the decreasing phase of long term variations.
Modulus and damping from shaking table tests of reinforced soil walls

The paper presents rational procedures to estimate normalised shear modulus and damping ratio from measured responses of reinforced soil model walls tested in a 1-g shaking table. Displacement measured at the top of the model walls and input base acceleration time histories are used to produce equivalent hysteretic responses of the model walls. Equivalent hysteretic loops at different strain amplitudes are developed and used to calculate normalised modulus degradation curves and damping ratio for the tested model walls. Model wall responses are also analysed using the single degree of freedom (SDOF) model to determine damping ratio and phase difference, and to verify the validity of SDOF model for application with reinforced soil walls. Results indicate that the normalised shear modulus significantly decreased at the early stage of the base shaking (i.e. γs < 0.03%). For example, about 68% and 80% reductions in shear modulus occurred at γs = 0.005% and 0.01% respectively. In addition, a 90% reduction in the normalised shear modulus realised at relatively strong input base acceleration (i.e. for γs > 0.03%). Minimum damping ratio of 5% to 10% for both model walls was obtained, increased to 15% to 20% at strain amplitude γs = 0.3%, and reached higher values thereafter. Finally, dynamic properties determined from the proposed method are compared with experimental and empirical relationships proposed in literature as well as resonant column test results.
Hindcast and predictability of sporadic Kuroshio-water intrusion (kyucho in the Bungo Channel) into the shelf and coastal waters

[1] Prerequisite(s) for ocean circulation models capable of hindcasting “kyucho” occurrence (a sudden coastal temperature rise induced by Kuroshio frontal waves) in the Bungo Channel, Japan, is investigated using long-term observed temperature and sea level time series, archived hydrographic data, and reanalysis data provided by the Japanese Coastal Ocean Predictability Experiment (JCOPE) group. Anticyclonic mesoscale eddies impinging on the Kuroshio front south of the Bungo Channel enhance the frontal sharpness, frontal wave growth, and activity of kyucho phenomena. A kyucho hindcast is carried out to examine the reliability of a numerical model including realistic anticyclonic eddies propagating south of Japan. The Finite Volume Coastal Ocean Model (FVCOM) for which boundary conditions are given by daily JCOPE2 reanalysis data is adopted in the present study. This numerical model does a reasonable job of hindcasting kyucho occurrence in 2003. It is therefore considered that forecasts of kyucho occurrence up to 2 or 3 months ahead are possible by using the FVCOM in conjunction with JCOPE2 forecast data.
Fault-related fluid flow history in shallow marine sediments from carbonate concretions, Crotone basin, south Italy

We present the results of a multidisciplinary study on the relationships between the structural architecture of an extensional fault system in poorly lithified shallow marine sands and the associated pattern of diagenetic carbonate concretions. Based on their shape, spatial distribution, cement texture and chemistry, and isotopic signature, carbonate concretions are grouped into (1) tabular (encompassing also nodular and lens-shaped) concretions developed within the fault zones, and (2) elongate and coalescent strata-bound concretions formed adjacent and mostly parallel to fault zones. Cement chemistry and morphology, as well as stable carbon–oxygen isotopic signatures, indicate that tabular concretions formed during early diagenesis in the vadose mixing marine–meteoric zone, possibly during coseismic rupture propagation and, in the interseismic periods, as a result of slow capillary suction along the low-permeability fault zones. On the other hand, elongate concretions formed after regional uplift and during telodiagenesis by precipitation from meteoric, phreatic water flowing parallel to the fault zones, which acted as a hydraulic barrier. The concretion patterns record the evolution of fluid flow orientation and the changing chemistry of fault-zone fluids, which were fundamentally driven by fault system propagation and resulting fault architecture during two major diagenetic stages.