ALBERT

Description: Abstract Contractional deformation in the outer parts of fold‐and‐thrust belts is in part controlled by the presence of syntectonic sediments and multiple décollements (e.g. the Apennines, the Appalachians, the Pyrenees, the Zagros, or the Sub‐Andean and Kuqa fold‐and‐thrust belts). To better understand the influence of these parameters in the kinematic evolution of fold‐and‐thrust systems, we carried out an experimental study including four 3D sandbox models inspired by one of the previously mentioned prototypes, the Kuqa fold‐and‐thrust belt. This belt contains two décollements: a weak synorogenic salt layer; and a deeper, preorogenic and frictionless décollement (i.e., organic‐rich shales) showing along strike variations of rheology. The experimental results show that increasing synkinematic sedimentation rate: (i) generates a progressive change from distributed to localized deformation and, (ii) delays the development of frontal contractional structures detached on the salt, favoring the formation and reactivation of more hinterland thrusts and backthrusts. With respect to the rheology, our study reveals that as the viscosity of the prekinematic décollement increases: (i) the deformation propagates more slowly towards the foreland and, (ii) the underlying thrust stack becomes broader and lower and has a gentler thrust taper angle. The rheology of the prekinematic décollement defines the distribution and geometry of the structures detached on it that in turn influence the development of overlying, salt‐detached structures. Subsalt structures can: (i) determine the areal extent of the salt and therefore of any fold‐and‐thrust system detached on it and, (ii) hamper or even prevent the progressive foreland propagation of deformation above the salt.

Description: Abstract The aim of this paper is to improve semi‐seasonal forecast of groundwater availability in response to climate variables, surface water availability, groundwater level variations, and human water management using a two‐step data‐driven modeling approach. First, we implement ensemble artificial neural networks (ANN) for the three hundred wells across the High Plains aquifer (US). The modelling framework includes a method to choose the most relevant input variables and time lags; an assessment of the effect of exogenous variables on the predictive capabilities of models; and the estimation of the forecast skill based on the Nash‐Sutcliffe efficiency index (NSE), the normalized root mean squared error and the coefficient of determination (R2). Then, for the ANNs with low accuracy, a Multi Model Combination (MuMoC) based on a hybrid of ANN and instance‐based learning method is applied. MuMoC uses forecasts from neighboring wells to improve the accuracy of ANNs. An exhaustive‐search optimization algorithm is employed to select the best neighboring wells based on the cross‐correlation and predictive accuracy criteria. The results show high average ANN forecasting skills across the aquifer (average NSE 〉 0.9). Spatially distributed metrics of performance showed also higher error in areas of strong interaction between hydro‐meteorological forcings, irrigation intensity, and the aquifer. In those areas, the integration of the spatial information into MuMoC lead to an improvement of the model accuracy (NSE increased by 0.12), with peaks higher than 0.3 when the optimization objectives for selecting the neighbors were maximized.

Description: Abstract Explosive volcanic eruptions have large climate impacts, and can serve as observable tests of the climatic response to radiative forcing. Using a high resolution climate model, we contrast the climate responses to Pinatubo, with symmetric forcing, and those to Santa Maria and Agung, which had meridionally asymmetric forcing. Although Pinatubo had larger global‐mean forcing, asymmetric forcing strongly shifts the latitude of tropical rainfall features, leading to larger local precipitation/TC changes. For example, North Atlantic TC activity over is enhanced/reduced by SH‐forcing (Agung)/NH‐forcing (Santa Maria), but changes little in response to the Pinatubo forcing. Moreover, the transient climate sensitivity estimated from the response to Santa Maria is 20% larger than that from Pinatubo or Agung. This spread in climatic impacts of volcanoes needs to be considered when evaluating the role of volcanoes in global and regional climate, and serves to contextualize the well‐observed response to Pinatubo.

Description: Abstract Megathrust earthquakes are commonly accompanied by increased upper‐plate seismicity and occasionally triggered fault slip. In Chile, crustal faults slipped during and after the 2010 Maule (M8.8) earthquake. We studied the El Yolki fault (EYOF), a transtensional structure midways the Maule rupture not triggered in 2010. We mapped a Holocene coastal plain using LiDAR, which did not reveal surface ruptures. However, the inner‐edge and shoreline angles along the coastal plain as well as 4.3‐4.0 ka intertidal sediments are back‐tilted on the EYOF footwall block, documenting 10 m of vertical displacement. These deformed markers imply ~2 mm/yr throw rate and dislocation models a slip rate of 5.6 mm/yr for the EYOF. In a 5‐m‐deep trench, the Holocene intertidal sediments onlap to five erosive steps, interpreted as staircase wave‐cut landforms formed by discrete events of relative sea‐level drop. We tentatively associated these steps with coseismic uplift during EYOF earthquakes between 4.3 and 4.0 ka. The Maule earthquake rupture may be subdivided into three subsegments based on coseismic slip and gravity anomalies. Coulomb stress transfer models predict neutral stress changes at the EYOF during the Maule earthquake but positive changes for a synthetic slip distribution at the central subsegment. If EYOF earthquakes were triggered by megathrust events, their slip distribution was probably focused in the central subsegment. Our study highlights the millennial variability of crustal faulting and the megathrust earthquake cycle in Chile, with global implications for assessing the hazards posed by hidden but potentially seismogenic coastal faults along subduction zones.

Description: Abstract Aim To understand how variations in precipitation and topographic wetness influence tree community assembly at both regional and landscape scales in tropical forests. Location New Caledonia (SW Pacific). Methods We sampled 40 tree communities in 0.04‐ha plots laid along topographic gradients within two landscapes with contrasting precipitation. Within a dry (〈1400 mm.yr‐1) and a wet (〉2500 mm.yr‐1) landscape we used the Topographic Wetness Index (TWI) to sample communities in topographic position with low (e.g. ridges) and high (e.g. valleys) water accumulation. For each sampled species, we measured five functional traits involved in drought resistance and resource acquisition (wood density, leaf area, leaf specific area, leaf dry matter content, and leaf thickness). We first examined trait covariation across species. We then analyzed how the functional composition of communities varied between landscapes (according to precipitation) and within landscape (according to TWI), using trait‐based statistics and null models. Results We identified two ecological trade‐offs driving trait variation across species: (i) one opposing high hydraulic efficiency to drought resistance, related to a wood economic spectrum, and (ii) the other opposing resource acquisition to resource conservation, related to a leaf economic spectrum. Across landscapes, species with drought‐resistance strategies were favored at lower precipitation. Within landscapes, drought‐resistant species were selected under low TWI in the dry landscape, while low TWI increased the abundance of species with conservative strategies in the wet landscape. Conclusions Precipitation and topography jointly shape the functional composition of tree communities. At low precipitation, hydric constraints prevailed on ridges and upslopes by filtering drought‐resistant strategies along the wood economic spectrum. Contrastingly, higher precipitation relaxed the hydric constraints and resource availability became a primary driver of changing strategies along the leaf economic spectrum. Thus, the landscape‐scale influence of topography on processes driving community assembly and functional composition critically depends on the regional climatic context. This article is protected by copyright. All rights reserved.

Description: Abstract A new methodology to quantify minerals’ criticalities is proposed—the criticality systems of minerals. In this methodology, four types of agents—mineral suppliers, consumers, regulators of the market, and others, such as the communities near mining operations—interact with each other through three types of indicators: constraints, such as the political stability in the mining regions, the mineral's substitutability and economic importance; agents’ interactions, such as buyer–seller bargaining; and interactive variables, such as the demand, supply, and price. When the criticality systems of two mineral groups are constructed, analyses that compare the indicators of these criticality systems can determine which group is more critical than the other. This methodology allows evaluation of criticality in a dynamic and systemic manner.

Description: The assimilation of SMOS brightness temperature ( TB) data in Numerical Weather Prediction Systems influences the state of the soil, which in turn affects the exchange of energy and water fluxes between the soil and the near surface atmosphere, with potential implications in the prediction of atmospheric variables. In this paper, the impact of assimilating SMOS TB alone or in combination with screen level observations and ASCAT soil moisture retrievals is assessed. Independent quality controlled in situ soil moisture observations belonging to several networks, included in the International Soil Moisture Network, were used to validate the quality of both the new soil moisture analyses and the skill to predict soil moisture up to 5 days ahead. The impact on atmospheric variables is indirect and it was evaluated through computation of the forecast skill at different lead times. The analysis period was selected to be around the boreal summer, a period of the year when evaporatranspiration fluxes are stronger, and when it is therefore expected that the assimilation of remote sensing data provides the largest impact on the state of the soil. The results show that the soil moisture state benefits from the direct assimilation of SMOS TB, especially in better representing the temporal variations of soil moisture. The skill on atmospheric variables is mainly driven by the screen level observations. Despite the clear benefits to the soil state, remote sensing data needs to be used with screen level variables to add value to the state of the atmosphere, pointing to inconsistencies in the physical coupling between the land and near‐surface components of the ECMWF Earth system.

Description: Abstract Broadband seismic data were recorded on the ground surface around an exceptionally regular eruptive system, geyser El Jefe, in the El Tatio geyser field, Chile. We identify two stages in the eruption, recharge and discharge, characterized by a radial expansion and contraction, respectively, of the surface around the geyser. We model the deformation with spherical sources that vary in size, location, and pressure, constrained by pressure observations inside the conduit that are highly correlated with deformation signals. We find that in order to fit the data, the subsurface pressure sources must be laterally offset from the geyser vent during the recharge phase and that they must migrate upward toward the vent during the eruption phase. This pattern is consistent with models in which ascending fluids accumulate and then are released from a bubble trap that is horizontally offset from the shallow conduit of the geyser.

Description: Abstract Aim To synthesize published knowledge on palm–frugivore seed dispersal observations and to test whether broad‐scale differences in geographic coverage, diversity, composition and functional structure of plant–animal interactions emerge between biogeographical regions. Location Neotropics and Afrotropics. Methods We constructed a meta‐network for both regions by aggregating observations of pairwise palm–frugivore interactions from the primary literature. We assessed sampling completeness with accumulation curves and estimated knowledge gaps for individual palm species and geographic units within biogeographical regions. We compared the taxonomic composition as well as structural indices of regional interaction networks and tested whether functional trait matching (i.e., the relationship between palm fruit size and frugivore body size) differs between regions. Results A total of 750 unique pairwise interaction records were retrieved from the primary literature covering 340 frugivores and 126 palms. Sampling completeness of frugivore interactions within biogeographical regions and for individual palm species was low (often 〈50%), geographic coverage limited, and relative knowledge gaps were largest in areas with high palm species richness. Interaction diversity and network modularity was larger in the Neotropics than the Afrotropics. A positive fruit size–body mass relationship (i.e., functional trait matching) was statistically significant in the Afrotropics, but not in the Neotropics. Main conclusions Available data on palm–frugivore interactions suggest major biogeographical differences in ecological networks among regions, even when taking differences in palm species richness into account. The Neotropics showed a larger interaction diversity and more modular network structure than the Afrotropics. Broad‐scale morphological trait matching among plants and frugivores was only observed in the Afrotropics. The lack of a Neotropical trait matching relationship might be driven by the late Quaternary extinctions of mammalian megafauna in this region. Although our work has increased the digital availability of palm–frugivore interaction observations, massive knowledge gaps of interaction diversity remain in the tropics.