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The East Junggar orogen is a major constituent of the southwestern Central Asian Orogenic Belt (CAOB). The Permian-Triassic strata exposed there is the first terrestrial sedimentary cover overlaying the Palaeozoic volcanic basement, and are well developed in the Kalamaili Mountain in the East Junggar. An obvious angular unconformity developed between the Permian and Triassic in the East Junggar, which is also widely seen in the Tian Shan and the Junggar Basin. Based on field observations, petrology, sedimentology, and detrital zircon U-Pb geochronology, we evaluate different mechanisms for the Permian-Triassic angular unconformity, clarify the characteristics of the tectonic movement during Permian-Triassic time and its control on the sedimentation in the East Junggar region, and identify the mountain-basin coupling processes.The sedimentary characteristics of the deposits show an abrupt change in depositional environments from a fluvial delta-lacustrine depositional system to an alluvial fan across the unconformity. The yellow conglomerate developed in the Middle Permian Pingdiquan Formation contains rounded and imbricated clasts, which indicate a relatively strong hydrodynamic environment within a fluvial delta. The red-brownish conglomerates in the Lower Triassic Cangfanggou Formation have poor sorting and are interpreted as typical alluvial fan deposits. Meanwhile, the heavy minerals statistics from sandstones show a higher abundance of stable heavy minerals in the Middle Permian Pingdiquan Formation than in the Lower Triassic Cangfanggou Formation, which indicates a provenance change from distal to proximal.The detrital zircon U-Pb ages from 9 clastic rock samples from the south flank of the Kalamaili Mountain show that in the Early Permian, a prominent age peak of ~330 Ma occurred. These sediments may have been derived from neighboring source areas, such as the Early Carboniferous volcanic rocks in the Kalameli tectonic belt. The Middle Permian samples show multiple age peaks of ~260 Ma, ~320 Ma, ~360 Ma, and ~510 -420 Ma, indicating that the source area gradually became enriched from other sediment sources. The source might include the Early Carboniferous volcanic rocks, Late Carboniferous granites, northern Early Paleozoic Yemaquan Island arc (~450 Ma), and/or the Early Paleozoic Karameli ophiolite (~490 Ma). The occurrence of these units marks the uplift of the East Junggar orogen range and significant deep terrane exhumation. The age peaks of the red conglomerate in the Lower Triassic are more diverse ~830-260Ma, which suggests that this region is still in a state of uplift and denudation, providing continuous supply to the basin. Combined with sedimentary characteristics and published data, our new data suggest that the East Junggar has also gone through a tectonic inversion in the Late Permian after large-scale orogenesis in the Late Carboniferous and post-collisional extension in Early-Middle Permian. Together, these events caused the Permian-Triassic angular unconformity and different sedimentary environments. In addition, results are consistent with the published conclusion that an uplift occurred in the Northern-Central Tianshan and the Bogda mountain in the southeastern Junggar in the Late Permian. These results provide vital data for reconstructing the Pangea supercontinent and the Hercynian movement of the Central Asian Orogenic Belt.

Topography in compressional mountain ranges represents an interface at which tectonic and climatic forces interact. Understanding the relative contribution of these two components to mountain formation has been at the forefront of research over the last two decades. The theory underlying the mechanics that govern these interactions has been built on Coulomb wedge mechanics, i.e., mechanical failure and rock uplift occur everywhere along the wedge and the orogen. Observed rock displacement along single, discrete fault planes, including the translation of uplifted topography laterally, appears to be counter to such mechanics. However, a critically tapered topography across fold-thrust belts still emerges. If a critically tapered topography along an orogenic wedge can be produced by the sequential evolution of the subsurface fault geometry and the associated motion of bedrock over discrete fault planes, then a mechanical failure everywhere is not required. Here, the geomorphic evolution of the fold-thrust belt in central Nepal since the Miocene is investigated using a numerical surface processes model whereby the structural geometry, location and magnitude of fault motion are prescribed and based on observations. In addition, end-member climatic scenarios are adopted, i.e., uniform precipitation and climatic change over geologic time as predicted by atmospheric general circulation models. The experiments reproduce the first-order topography of central Nepal. Our modelling results indicate a dynamic variability of erosional efficacy that promotes the interplay of two modes of orogenic wedge behaviour and are contrary to a mechanical failure everywhere along the wedge: (mode 1) phases of lateral translation of uplifted topography and in-sequence propagation of deformation fronts, and (mode 2) phases of hinterland incision during out-of-sequence fault activity. The successful replication of first-order geomorphic indices in central Nepal in our experiments confirms an unusually long-lasting Miocene to Pliocene activity of the Main Boundary Thrust in central Nepal. This period is followed by Late Pleistocene hinterland incision coeval with out-of-sequence fault activity prior to the onset of rock displacement along the Main Frontal Thrust during a time of increased precipitation relative to today.

The Andes’ elevation of ~4 km and great meridional extent of ~50°S to 10°N greatly influences the spatial climate patterns across the South American continent. Apart from latitude and altitude, quasi-stable pressure systems modify the climate of the region. The Bolivian high, an upper-level anticyclonic circulation over the central part of the continent, is one such feature and has a strong impact on atmospheric moisture transport and the regional hydroclimate of the Central Andes. Orbitally forced shifts in the Bolivian High have been hypothesised to be responsible for anti-phase palaeoclimate changes in Peru in the mid-Holocene, such as the increase in humidity in the Palpa region and synchronous extreme drought near Lake Titicaca [e.g., Mächtle et al. 2013]. However, this hypothesis has not been tested, and it has not been determined how much of the mid-Holocene hydroclimate change in the Central Andes can be explained by changes in regional pressure systems. Here, we test the hypothesis that mid-Holocene orbital variations and palaeogeographical changes modified pressure fields and regional moisture transport, and lead to anti-phase changes in regional hydroclimate. We test this hypothesis using the physics-based, isotope-tracking climate model ECHAM5-wiso. More specifically, we analyse pre-industrial and mid-Holocene paleoclimate simulations [Mutz et al. 2018] to track changes in pressure fields and moisture transport. We then assess their impacts on regional hydroclimate in the Central Andes. Results indicate that: (a) the climate models reproduce the observed synchronous anti-phase (wetter and drier) climate changes documented in different parts of Peru, and (b) these can be explained by changes in the regional pressure and wind fields. Taken together, previous proxy-based observations and model results present here indicate that orbital variations drive changes in the regional pressure systems and lead to spatially heterogenous variations in hydroclimate across the Central Andes.

Stream piracy has been central in explaining landscape evolution since W. M. Davis first introduced the concept. Reconstructions of drainage histories routinely invoke rerouting of an antecedent river to a lower adjacent stream. However, despite decades of analytical and computational progress, inferring discrete river reorganisation events remains challenging. In this contribution, we document how the transient drainage history of a region can be reconstructed using digital topography. Our premise is that previous topographic analyses neglect older stream piracy events. For example, in a typical retreating escarpment scenario, such as in southwestern Germany, erosion is concentrated in steep escarpment-draining rivers that occasionally capture plateau areas. These captures are readily detectable using topographic archives such as paired "area-gain/area-loss" profiles in χ-elevation space and mobile knickpoints at or upstream of capture points. However, such topographic archives decay as channels adjust to changes in drainage area, and thus many captures remain 'undetected' after escarpment retreat.Here we use wind-gaps, a unique post-capture landform that is more prone to persist due to its position as a drainage divide, to identify otherwise 'undetectable' prior piracy events. We take advantage of TopoToolbox's DIVIDEobj algorithm to extract the drainage divide network of a landscape as a whole (i.e., every ridgeline separating neighbouring streams). From this, we calculate the ratio between the elevation of a segment in the divide network and the average elevation of neighbouring divides. We identify wind-gaps as (i) low-elevation divides confined on both sides by neighbouring higher divide segments, which (ii) are also characterised by low across-divide differences in relief. This approach provides insight into the drainage evolution history of South German Scarplands. The tectonic development of the Upper Rhine Graben led to an incipient northwest-oriented drainage that became progressively more erosive, especially since the Late Miocene. These northwest-draining rivers, such as the Neckar River, expanded their drainage areas via multiple discrete piracy events. This sequence of capture events led to the reversal of southern German rivers that originally drained to the southeast (towards the Danube). Our results identify tens of piracy events considerably downstream of the current divide separating the Neckar and Danube catchments that otherwise would not have been identified and put in temporal context. These results are in contrast to previous approaches that could only identify capture events in the vicinity of the current divide. In areas adjacent to wind-gaps and along 'reversed' and 'beheaded' streams, we explore the morphological relationships with the relative timing of the stream piracy events. Taken together, these results lead to a more comprehensive treatment of drainage history from topographic data.

Proposed drivers of eastern Andean Plateau river incision in the Pliocene include climate change, dynamically driven plateau uplift, and long-wavelength surface uplift above deep basement structures. However, the evaluation of each mechanism has been hampered in previous studies due to the lack of along-strike data on the timing and extent of canyon incision. In addition, the magnitude of exhumation, permissible structural geometries, and integration of the long-term deformation, erosion, exhumation, and sedimentation histories remain poorly understood.This presentation focuses on two balanced geologic cross-sections and thermochronologic bedrock sample transects across the Andean Plateau, Eastern Cordillera, and Subandes in southern Peru. Based on (i) age-distance and age-elevation patterns of >80 new thermochronologic dates (apatite and zircon (U-Th)/He and fission-track) from plateau, interfluve, and canyon sample locations; (ii) inverse thermal history model results; and (iii) flexural and thermo-kinematic modeling, we highlight similarities and differences in thermochronometric age patterns, exhumation magnitude, structural geometries, and shortening rates between each section.Results show that the first-order thermochronometric age pattern is a function of rocks' vertical and lateral movement over basement ramps and resulting exhumational erosion. This pattern is superimposed with a regional and synchronous incision-related exhumation signal since the Pliocene. While this incision occurred independent of structural deformation, the exhumation magnitude and difference in interfluve and canyon thermochronometric ages require the presence of a tectonic contribution to exhumation. We conclude that uplift over a basement ramp in the Eastern Cordillera and a decrease in shortening rates since ~10 Ma set the stage for climate-enhanced incision to occur in southern Peru.

The Northern Alpine Foreland Basin, also known as the Molasse Basin, developed as a flexural response to the loading of the European plate by the Alpine thrust wedge during a continental collision between the Adriatic and European plates. Along-strike variations in Middle Eocene to Early Miocene depositional environments in the Molasse Basin are the sedimentary transcript of along-strike variations in crustal- and lithospheric processes that governed flexural subsidence and sediment supply. To study which mechanism(s) drove the generation of observed along-strike variations, we analyse both the basement and fill of the Molasse Basin. To this end, we construct a low-resolution 3D geological model which allows us to reconstruct the architecture of both the Mesozoic European margin and the Eocene basin floor at the onset of flexural subsidence. Furthermore, we interpret 2D/3D reflection seismic data, constrained by well data, to characterize the spatiotemporal development of depositional environments and syn-flexural normal fault kinematics. The latter is used as a fingerprint of hinterland tectonics. Our results suggest that the dominant mechanism driving along-strike variations in basin architecture was oblique continental collision leading to along-strike variations in source area uplift. However, this does not exclude additional contributions of the Oligocene to Early Miocene slab breakoff- and subsequent tearing below the Alps to orogen-parallel variations in the uplift of the sediment source area.

It has been proposed that geodiversity (the diversity of geological, geomorphological and pedological features) is positively correlated with biodiversity. This suggests that by preserving geodiversity, we can also preserve biodiversity and the associated ecosystem functions. However, a significant correlation between geodiversity and biodiversity measures does not mean causation and does not distinguish spatial and temporal scale dependencies of the processes involved. In fact, such a correlation could also imply that biodiversity estimates can predict geodiversity. These aspects have, nonetheless, rarely been considered in geo- and biodiversity studies, which constrains the applicability of these analyses in, for example, models of geo- and biodiversity distribution that rely on explicit processes. We aim to explore the interactions between geo- and biodiversity across different scales, identifying the key mechanisms that link them. The feedbacks between geodiversity and biodiversity start at the microscale during the process of soil aggregation and formation, driven by microbial diversity such as fungi and biological soil crusts, as well as by plant roots. On the other hand, soil texture defines microsites for microbial life, and surface types and quality shape their colonization process. At intermediate landform or catchment scales, the spatial variability of topographical, lithological and soil features benefits the formation of diverse habitats and resources for biota (e.g. plants, vertebrates and invertebrates), which, at the same time, will affect radiation distribution, erosion and nutrient availability. At even larger scales, processes like mantle dynamics and the number of plate boundaries can determine regional-scale shifts in ecosystems, isolation processes and the evolution of biota. Similarly, temporal variability determined by, e.g. microclimate, catchment scale meteorology or orographic effects, induces niche variability within a spatial scale. Finally, based on these process-related relationships at variable scales, we suggest a list of geodiversity parameters to be used when assessing geo- and biodiversity interactions.

The European Alps are hypothesized to have experienced diachronous surface uplift in response to post-collisional processes such as, e.g., slab break-off. Therefore, understanding the geodynamic and geomorphic evolution of the Alps requires knowledge of its surface uplift history. This study presents the simulated response of regional climate and oxygen isotopic composition of precipitation (δ18Op) to different along-strike topographic evolution scenarios. These responses are modeled to determine if diachronous surface uplift in the Western and Eastern Alps would produce δ18Op signals in the geologic record that are sufficiently large and distinct for stable isotope paleoaltimetry. This is tested with a series of sensitivity experiments conducted with the water isotope tracking atmospheric General Circulation Model (GCM) ECHAM5-wiso. The topographic scenarios are created from the variation of two free parameters, (1) the elevation of the West-Central Alps and (2) the elevation of the Eastern Alps. Results suggest significant changes in the spatial patterns of δ18Op, the elevation-dependent rate of change in δ18Op (“isotopic lapse rate”), near-surface temperatures, precipitation amounts, and atmospheric circulation patterns in response to the different scenarios. The predictions for the diachronous surface uplift experiments are distinctly different from simulations forced with present-day topography and for simulations where the entire Alps experience synchronous surface uplift. Topographic scenarios with higher elevations in the West-Central Alps produce higher magnitude changes and an expansion of the affected geographical domain surrounding the Alps when compared to present-day topography. Furthermore, differences in δ18Op values of up to −2 to −8 ‰ are predicted along the strike of the Alps for the diachronous uplift scenarios, suggesting that the signal can be preserved and measured in geologic archives. Lastly, the results highlight the importance of sampling far-field and low-elevation sites using the δ-δ paleoaltimetry approach to discern between different surface uplift histories.

Precipitation in wet seasons influences catchment erosion and contributes to annual erosion rates. However, wet seasons are also associated with increased vegetation cover, which helps resist erosion. This study investigates the effect of present-day seasonal variations in rainfall and vegetation cover on erosion rates for four catchments along the extreme climate and ecological gradient (from arid to temperate) of the Chilean Coastal Cordillera (~26° S – ~38° S). We do this using the Landlab-SPACE landscape evolution model modified to account for vegetation-dependent hillslope-fluvial processes and hillslope hydrology. Model inputs include present-day (90 m) topography, and a timeseries (from 2000–2019) of MODIS-derived NDVI for vegetation seasonality; weather station observations of precipitation; and evapotranspiration obtained from GLDAS NOAH. Simulations were conducted with a step-wise increase in complexity to quantify the sensitivity of catchment scale erosion rates to seasonal variations in precipitation and/or vegetation cover. Simulations were conducted for 1,000 years (20 years of vegetation and precipitation observations repeated 50 times). After detrending the results for long-term transient changes, the last 20 years were analyzed. Results indicate that when vegetation cover is varied but precipitation is held constant, the amplitude of change in erosion rates relative to mean erosion rates ranges between 6.5 % (humid-temperate) to 36 % (Mediterranean setting). In contrast, in simulations with variable precipitation change and constant vegetation cover, the amplitude of change in erosion rates is higher and ranges between 13 % (arid) to 91 % (Mediterranean setting). Finally, simulations with coupled precipitation and vegetation cover variations demonstrate variations in catchment erosion of 13 % (arid) to 97 % (Mediterranean setting). Taken together, we find that precipitation variations more strongly influence seasonal variations in erosion rates. However, the effects of seasonal variations in vegetation cover on erosion are also significant (between 5–36 %) and are most pronounced in semi-arid to Mediterranean settings and least prevalent in arid and humid-temperature settings.

Funding: This manuscript resulted from a Workshop in 2019 at the Senckenberg Research Institute and Natural History Museum Frankfurt, Germany, supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA20100300). J. Liu also thanks the support of the Henan Provincial Key Laboratory of Hydrosphere and Watershed Water Security. T. Ehlers thanks the California Institute of Technology Moore Distinguished Scholar Program for support in completing this manuscript during a sabbatical. J. Liu and T. Bolch thank the support from the Strategic Priority Research Program of the Chinese Academy of Sciences (grants no. XDA20060402, XDA20100300). We thank the German Science Foundation (DFG) for support of the TiP (Tibetan Plateau: Formation-Climate-Ecoystems) priority research program (SPP-1372) for initiating the collaborations that led to this manuscript. Interactions between the atmosphere, biosphere, cryosphere, hydrosphere, and geosphere are most active in the critical zone, a region extending from the tops of trees to the top of unweathered bedrock. Changes in one or more of these spheres can result in a cascade of changes throughout the system in ways that are often poorly understood. Here we investigate how past and present climate change have impacted permafrost, hydrology, and ecosystems on the Tibetan Plateau. We do this by compiling existing climate, hydrologic, cryosphere, biosphere, and geologic studies documenting change over decadal to glacial-interglacial timescales and longer. Our emphasis is on showing present-day trends in environmental change and how plateau ecosystems have largely flourished under warmer and wetter periods in the geologic past. We identify two future pathways that could lead to either a favorable greening or unfavorable degradation and desiccation of plateau ecosystems. Both paths are plausible given the available evidence. We contend that the key to which pathway future generations experience lies in what, if any, human intervention measures are implemented. We conclude with suggested management strategies that can be implemented to facilitate a future greening of the Tibetan Plateau. Publisher PDF

Changes to the landscape over millions of years are a driver of Earth system processes

Frost cracking is a dominant mechanical weathering phenomenon facilitating the breakdown of bedrock in periglacial regions. Despite recent advances in understanding frost cracking processes, few studies have addressed how global climate change over the late Cenozoic may have impacted spatial variations in frost cracking intensity. In this study, we estimate global changes in frost cracking intensity (FCI) by segregation ice growth. Existing process-based models of FCI are applied in combination with soil thickness data from the Harmonized World Soil Database. Temporal and spatial variations in FCI are predicted using surface temperature changes obtained from ECHAM5 general circulation model simulations conducted for four different paleoclimate time slices. Time slices considered include pre-industrial (∼ 1850 CE, PI), mid-Holocene (∼ 6 ka, MH), Last Glacial Maximum (∼ 21 ka, LGM), and Pliocene (∼ 3 Ma, PLIO) times. Results indicate for all paleoclimate time slices that frost cracking was most prevalent (relative to PI times) in the middle- to high-latitude regions, as well as high-elevation lower-latitude areas such the Himalayas, Tibet, the European Alps, the Japanese Alps, the US Rocky Mountains, and the Andes Mountains. The smallest deviations in frost cracking (relative to PI conditions) were observed in the MH simulation, which yielded slightly higher FCI values in most of the areas. In contrast, larger deviations were observed in the simulations of the colder climate (LGM) and warmer climate (PLIO). Our results indicate that the impact of climate change on frost cracking was most severe during the PI–LGM period due to higher differences in temperatures and glaciation at higher latitudes. The PLIO results indicate low FCI in the Andes and higher values of FCI in Greenland and Canada due to the diminished extent of glaciation in the warmer PLIO climate.

Rock exhumation and surface uplift over subduction zones require part of the stresses to cause crustal thickening within the wedge and/or through basal accretion. Although accumulated elastic strain around subduction zones is released through megathrust earthquakes and related aftershocks, these large events often result in no permanent forearc surface uplift. Nevertheless, energy is also released by more frequent and dispersed background seismicity, a signal that is often overlooked. Here we investigate the variability of this energy along the Peru–Chile and Japan margins. We find that the pattern of background seismicity correlates with the margin-parallel long-wavelength wedge geometry and with published estimates of geologic-timescale coastal uplift. Furthermore, the orientation of the principal stresses related to these background events is consistent with contractional seismicity, predominantly located at the deep (30–60 km) plate interface depth. Taken together, these results indicate that background seismicity is associated with crustal thickening during the megathrust interseismic period. This mechanism may contribute substantially to the surface uplift of subduction margins over geologic timescales. Frequent and dispersed small earthquakes may contribute substantially to uplift of subduction margins, according to an analysis of such seismicity in the Peru–Chile and Japan margins.

In this study, we have created 10 geoscience video lessons that follow the paired-teaching pedagogical approach. This method is used to supplement the standard school curriculum with video lessons, instructed by geoscientists from around the world, coupled with activities carried out under the guidance of classroom teachers. The video lessons introduce students to the scientific concepts behind earthquakes (e.g. the Earth's interior, plate tectonics, faulting, and seismic energy), earthquake hazards, and mitigation measures (e.g. liquefaction, structural, and non-structural earthquake hazards). These concepts are taught through hands-on learning, where students use everyday materials to build models to visualize basic Earth processes that produce earthquakes and explore the effects of different hazards. To evaluate the effectiveness of these virtual lessons, we tested our videos in school classrooms in Dushanbe (Tajikistan) and London (United Kingdom). Before and after the video implementations, students completed questionnaires that probed their knowledge on topics covered by each video, including the Earth's interior, tectonic plate boundaries, and non-structural hazards. Our assessment results indicate that, while the paired-teaching video lessons appear to enhance student knowledge and understanding of some concepts (e.g. Earth's interior, earthquake location forecasting, and non-structural hazards), they bring little change to their views on the causes of earthquakes and their relation to plate boundaries. In general, the difference between UK and Tajik students' level of knowledge prior to and after video testing is more significant than the difference between pre- and post-knowledge for each group. This could be due to several factors affecting curriculum testing (e.g. level of teachers' participation and classroom culture) and students' learning of content (e.g. pre-existing hazards knowledge and experience). To maximize the impact of school-based risk reduction education, curriculum developers must move beyond innovative content and pedagogical approaches, take classroom culture into consideration, and instil skills needed for participatory learning and discovery.

The propagation of slab break-off (slab tearing) is usually attributed to laterally variable plate convergence systems with a spatial transition between simultaneous oceanic subduction and continental collision. To study the process of slab tearing in a non-collisional geodynamic context, here we use a 3D thermo-mechanical numerical approach to model the oblique subduction of a homogeneous oceanic plate. We investigate the effects of the following parameters: (1) subduction obliquity angle, (2) age of oceanic slab, and (3) partitioning of boundary velocities (i.e., the ratio between the subduction component and the advance of the overriding plate in the total convergence). In our simulations, the retreat of the subduction zone leads to a thinning of the fore-arc and back-arc lithosphere, which are decoupled from the subducting slab by the rise of the hot asthenosphere from the underlying mantle wedge. As a consequence of the initial obliquity of the active plate margin, slab roll-back velocities are subject to progressive along-trench variations. Consistent with the gradual rotation of the trench, the front of the decoupling between the overriding and downgoing plates (together with predicted magmatic activity and topographic uplift) migrates in a horizontal direction. In the experiments with low angles of subduction obliquity (< 15°), relatively old subducting plates (> 50 Ma), and in the absence of the subduction component in the overall shortening, slab detachment either develops simultaneously along the entire length of the subduction zone or does not occur at all. In contrast, with higher subduction obliquity (≥ 15°), younger slabs (≤ 50 Ma) and in the presence of a boundary push on the oceanic side, the initial slab break-off is followed by the gradual growth of the “tear” window in the direction opposite to the migration path of the previously established plates decoupling. The sharp contrast in trench retreat rates between subduction zone segments affected and unaffected by slab detachment results in the arcuate shape of the trench. Furthermore, the direction of slab tearing may change from horizontal to vertical, eventually leading to the formation of a transform fault on the subducting plate. Our results show striking similarities with several features – such as trench curvature, subduction zone segmentation, magmatic production, lithospheric stress/deformation fields, and associated topographic changes – observed in many subduction zones (e.g., Marianas, New Hebrides, Mexico, Calabrian).

The hydroclimate of the Tibetan Plateau (TP) and Central Asia (CA) plays a crucial role in sustaining surface water reservoirs and thus water resources in the respective regions. In this study, we investigate the changes in Asian hydroclimate and its driving forces during specific time intervals in the last 3 Ma. We conduct high-resolution (∼0.75° per grid cell) general circulation model ECHAM-5 experiments with boundary conditions for the mid-Pliocene (∼3 Ma), the Last Glacial Maximum (LGM; ∼21 ka), the mid-Holocene (∼6 ka), and the pre-industrial. Results suggest that seasonally relatively high precipitation rates (>1 mm day−1) were longer in the mid-Pliocene and shorter in the LGM, relative to the pre-industrial. We calculate different monsoon indices to detect changes in the intensity, strength and duration of the East Asian summer monsoon (EASM), South Asian summer monsoon (SASM), and the Indian summer monsoon (ISM), and construct climatologies of mid-latitude high-level westerly jet (WJ) stream occurrences based on the ECHAM5 wind fields. Our results suggest that in warm periods (e.g., mid-Pliocene or interglacial), the WJ migrates northward earlier in the year (April) and reaches higher latitudes than in the pre-industrial, resulting in a wetter TP and CA. During cooler periods (e.g., LGM or glacial), the WJ migrates northward later in the year (June) and remains over lower latitudes, resulting in a drier TP and CA. Increased/decreased local precipitation in TP and CA for the mid-Pliocene/LGM experiments correlates strongly with (a) intensity, strength and duration of the EASM, SASM, and the ISM and (b) WJ latitudinal position.

The Ekström Ice Shelf is one of numerous small ice shelves that fringe the coastline of western Dronning Maud Land, East Antarctica. Reconstructions of past ice-sheet extent in this area are poorly constrained, due to a lack of geomorphological evidence. Here, we present a compilation of geophysical surveys in front of and beneath the Ekström Ice Shelf, to identify and interpret evidence of past ice-sheet flow, extent and retreat. The sea floor beneath the Ekström Ice Shelf is dominated by an incised trough, which extends from the modern-day grounding line onto the continental shelf. Our surveys show that mega-scale glacial lineations cover most of the mouth of this trough, terminating 11 km away from the continental shelf break, indicating the most recent minimal extent of grounded ice in this region. Beneath the front ∼30 km of the ice shelf measured from the ice shelf edge towards the inland direction, the sea floor is characterised by an acoustically transparent sedimentary unit, up to 45 m thick. This is likely composed of subglacial till, further corroborating the presence of past grounded ice cover. Further inland, the sea floor becomes rougher, interpreted as a transition from subglacial tills to a crystalline bedrock, corresponding to the outcrop of the volcanic Explora Wedge at the sea floor. Ice retreat in this region appears to have happened rapidly in the centre of the incised trough, evidenced by a lack of overprinting of the lineations at the trough mouth. At the margins of the trough uniformly spaced recessional moraines suggest ice retreated more gradually. We estimate the palaeo-ice thickness at the calving front around the Last Glacial Maximum to have been at least 305 to 320 m, based on the depth of iceberg ploughmarks within the trough and sea level reconstructions. Given the similarity of the numerous small ice shelves along the Dronning Maud Land coast, these findings are likely representative for other ice shelves in this region and provide essential boundary conditions for palaeo ice-sheet models in this severely understudied region.

Local scale estimates of temperature change in the twenty-first century are necessary for informed decision making in both the public and private sector. In order to generate such estimates for Chile, weather station data of the Dirección Meteorológica de Chile are used to identify large-scale predictors for local-scale temperature changes and construct individual empirical-statistical models for each station. The geographical coverage of weather stations ranges from Arica in the North to Punta Arenas in the South. Each model is trained in a cross-validated stepwise linear multiple regression procedure based on (24) weather station records and predictor time series derived from ERA-Interim reanalysis data. The time period 1979–2000 is used for training, while independent data from 2001 to 2015 serves as a basis for assessing model performance. The resulting transfer functions for each station are then directly coupled to MPI-ESM simulations for future climate change under emission scenarios RCP2.6, RCP4.5 and RCP 8.5 to estimate the local temperature response until 2100 A.D. Our investigation into predictors for local scale temperature changes support established knowledge of the main drivers of Chilean climate, i.e. a strong influence of the El Niño Southern Oscillation in northern Chile and frontal system-governed climate in central and southern Chile. Temperature downscaling yields high prediction skill scores (ca. 0.8), with highest scores for the mid-latitudes. When forced with MPI-ESM simulations, the statistical models predict local temperature deviations from the 1979–2015 mean that range between − 0.5–2 K, 0.5–3 K and 2–7 K for RCP2.6, RCP4.5 and RCP8.5 respectively.

This study addresses the temporal variations in rockfall activity in the 5.2 km2 calcareous cliffs of the deglaciated Lauterbrunnen Valley, Switzerland. We did this using 19 campaigns of repeated terrestrial laser scans (TLS) over 5.2 yr, power-law predicted behavior from extrapolation of the TLS-derived frequency-magnitude relationship, and estimates of long-time-scale (∼11 k.y.) activity based on the volume of preserved postglacial rockfall talus. Results from the short-time-scale observations indicate no statistically significant difference between TLS observations averaging over 1.5 versus 5.2 yr. Rock-wall retreat rates in both cases are 0.03–0.08 mm/yr. In contrast, the power-law predicted rock-wall retreat rates are 0.14–0.22 mm/yr, and long-term rates from talus volumes are 0.27–0.38 mm/yr. These results suggest (1) short (1.5 yr) TLS inventories of rockfalls provide (within uncertainties) similar frequency-magnitude relationships as longer (5.2 yr) inventories, thereby suggesting short observation periods may be sufficient for hazard characterization from TLS, and (2) higher rock-wall retreat rates over long time scales (Holocene averaged) may reflect debuttressing and stress relaxation effects after glacial retreat, and/or enhanced rockfall activity under periglacial (climatic) conditions.

Erosion-vegetation interactions The impact of vegetation on erosion rates is hard to gauge. Although vegetation can hold soils in place mechanically, root systems can also loosen soils or even help to fracture rock. These processes can increase erosion, especially because areas of heavy vegetation tend to be in areas with high precipitation rates. Starke et al. tackled this issue using a large set of observations that span 3500 km of the Andes mountain range. They found a complex set of interactions where increasing vegetation decreases erosion in more arid regions but can accelerate erosion in vegetation dense regions. Science , this issue p. 1358

The Northern Alpine Foreland Basin developed in response to the collision between the European and Adriatic plates. During the Oligocene-Early Miocene coeval along-strike deposition of terrestrial and deep marine conditions are recorded in the western and eastern parts of the basin respectively. However, the mechanisms driving the observed variability in along-strike development of the basin are still poorly understood.To study the causes of the observed along-strike variability we review published geological data and (re)interpret available 2D and 3D seismic data, constrained by well data. We interpret (1) seismic facies, (2) stratigraphic surfaces and (3) tectonic structures. Our current focus area covers the transitional zone between the western and eastern parts of the basin.In our study we distinguish 6 stratigraphic surfaces from the Base Tertiary to the Top Aquitanian. From Upper Swabia to the German-Austrian border (along the basin strike) we observe that the top of the crystalline basement is tilted towards the east with an angle of 2-3°. Furthermore, the base of the Tertiary deposits is also tilted towards the east with an angle of 0.3°. The main structural features are E-W and NW-SE striking normal faults. In the western part of our study area the normal faults cut the crystalline basement, Mesozoic and Oligocene deposits. The faults are sealed by Rupelian deposits. Thickness changes (~20 m) occur in Rupelian and overlying Chattian deposits. Maximum offsets of up to 60 m are observed for Mesozoic reflectors. In the eastern part of our study area the normal faults cut the crystalline basement, Mesozoic, Oligocene and Early Miocene deposits. Thickness changes across these faults indicate fault activity during the Rupelian, Chattian and Aquitanian. Maximum offsets (>150 m) are observed for Chattian reflectors. Upper Aquitanian deposits seal these faults, which is younger than observed in the western part of the study area. The NW-SE striking faults confine Paleozoic grabens within the crystalline basement.We relate the observed normal faulting of the Oligocene and Early Miocene deposits to flexural downbending of the European plate, assumed to have been caused by tectonic loading of the Alps and/or European slab pull. Furthermore, we suggest that the observed temporal variation in termination of fault activity is related to temporal and spatial variations in tectonic loading of the Alps and/or European slab pull. Finally, based on the observed eastward tilt of the top crystalline basement and Base Tertiary along the basin strike, variations in pre-existing crustal architecture must be considered.

The 2015 Gorkha earthquake reignited an existing debate about whether geometric barriers on faults play a role in containing the propagation of ruptures. Models suggest that the extent of the Gorkha earthquake rupture, and of other historical earthquakes were controlled by the locations of ramps in the Main Himalayan thrust (MHT), notably on the western edge of the rupture. The existence of such a pronounced lateral boundary to the west of the Gorkha epicenter is supported by an offset in the surface trace of the Main Central thrust (MCT), closely followed by an offset in the distribution of young (40Ar/39Ar (MAr) ages. However, the zircon (U-Th)/He (ZHe) and apatite fission track ages show more linear east-west distributions over the same region, as does Physiographic Transition 2 (PT2). We explore the formation of these relationships by combining forward-modeled balanced cross-sections through the Marsyangdi, Daraundi, and Budhi Gandaki valleys in central Nepal, and investigate the continuity of active structures across the western portion of the Gorkha rupture. The sequential kinematics of each of these sections are combined with a thermokinematic model (PECUBE) to evaluate the exhumation and cooling histories of the rocks exposed at the surface. We gauge the validity of these models by comparing their predicted cooling ages to measured ages, discarding those that do not match the measured distribution of cooling ages.Our 3D models show that the offset in the surface geology along the Daraundi is due to a shorter (by 1/3) Trishuli thrust sheet, that has been completely translated to the south of the modern ramp and folded by the Lesser Himalayan duplex. Similarly, the southern extent of the reset MAr ages is also controlled by these relationships requiring observed surface offsets to be the result of changes in the hanging wall rocks translated over the ramp, rather than changes in the geometry of the modern ramp. Notably, the continuity and location of the modern MHT ramp is evidenced by the linear distribution of the youngest ZHe and AFT ages, which are most sensitive to the location of the active ramp. Additionally, the out-of-sequence thrust responsible for PT2 soles directly into the modern ramp during its proposed period of activity at ~1.2 Ma, resulting in the highly linear trace of PT2, running parallel to the location of the ramp. These linear relationships and their reproducibility in thermo-kinematic models argue strongly against any geometric offsets in the modern MHT ramp that have been proposed to limit rupture propagation in central Nepal.

Rockfall both is a major process in shaping steep topography and a hazard in mountainous regions. Besides increasing thread due to thawing permafrost-stabilization in high-elevation areas, there are abundant permafrost-free over-steepened rockwalls releasing rockfall due to other triggers. General rockfall event susceptibility is addressed to frost cracking, earthquake shacking and hydrologic pressure in the walls, and to geotechnical rock properties. Spatial rockwall surface surveys or scans (delivering 3D point clouds) have been used to both deduce rock fracture patterns and to measure individual rockfall events from comparing subsequent scans. Though, the actually measured rockwall topography data has rarely been used as a general predictor of rockfall susceptibility against the background of observed events.In this study, we use a series of dm-resolved annual (2014 to 2020) terrestrial laser scan surveys along 5km2 of limestone cliffs in the Lauterbrunnen Valley, Switzerland. The annual scan data were hand-cut to remove vegetation and fringes, and then referenced to detect subsequent topographic change in the direction of the wall. From the change-detection point clouds individual rockfall event volumes were detected from cluster and filtering analyses. One surveyed rockwall section of 2014 was used as training data for our Bayesian classification model of rockfall susceptibility, while the adjacent remaining section served for model validation. We rasterized their 3D data points and calculated several surface parameters per cell, including roughness, topography, mean distances for the three main fracture systems, fracture density, local dip, percent of overhang area, normal vector change rate (called edge) and percentage of overhang area. For various parameter sets and different cell sizes (32m2, 52m2, 102m2, 152m2, 252m2, and 402m2), we trained Naïve-Bayes-Classifier models. These were then used to predict rockfall susceptibility per cell, based on our observations of surface parameters, and assessed using Kullback-Leibler Divergence analysis and the misclassification cost score.Results indicate the overall best model (accounting for the parameters roughness, edge, topography and overhang area) and for the lowest cell size (32m2) could predict rockfall cells with a probability of 0.73 (against a mean of 0.3 for all cells). Predictions on another rockwall section with observed rockfall, located on the opposite side of the valley, verified the model’s applicability by both comparable probabilities (0.6 vs 0.25) and visual surveys on overhangs. We find our approach could reliably extend this spatial rockfall susceptibility classification to all Lauterbrunnen rockwalls. The classification model generally identified overhang areas and fractured zones as high rockfall risks, matching the general insight of these zones to be of major susceptibility. Interestingly, our method is based only on orientation-independent variables that are directly calculated from the 3D point cloud. Thus, it should be principally transferable to other sites of fractured limestone walls. Specifically, there is no need to determine fracture sets from the point cloud as is generally done for susceptibility studies, since we account for topography that would anyway be used to calculate fracture planes (facets). Hence, this method provides a simple means to predict spatial rockfall susceptibility, applicable for both hazard mapping and landscape evolution studies.

The topographic formation of large mountains and plateaus significantly impacts regional and global climate. Previous studies demonstrated that major mountain ranges can explain important aspects of synoptic scale climate dynamics and notable features of the climate system, such as the position of the intertropical convergence zone. Quantifying the synergistic climatic effects of the coeval evolution of major mountain ranges fosters a deeper understanding of climate and Earth system dynamics. Furthermore, it helps estimate where (and by how much) a regional climate signal recorded in a geological archive is affected by topographic changes in distant, off-site orogens. In this study, we use ECHAM5-wiso General Circulation Model (GCM) simulations to explore the synergistic global effects of systematically co-varying the height of the Andean and Himalaya-Tibet Plateaus. The simulations are conducted with different topographic evolution scenarios for these orogens, while environmental boundary conditions, such as global ice cover and greenhouse gas concentrations, are kept constant. More specifically, the topographies of the orogens are incrementally reduced by 25% of their current height. This results in 5 topographic scenarios for the Himalaya-Tibet by setting its elevation to 100%, 75%, 50%, 25% and 0% of current values. These are nested in the analogous 5 topographic scenarios for the Andes, resulting in a total of 25 scenarios and GCM simulations. We then conduct an empirical orthogonal functions (EOF) analysis on the pressure fields produced by each of the simulations to track changes in quasi stable pressure systems. Furthermore, we track changes in cross-equatorial atmospheric transport and synoptic scale atmospheric flow. While most of the regional impacts of evolving topographies can be explained by atmospheric lapse rates and physical air flow disruption, global impacts can be explained by changes in surface heat distribution and pressure centres affecting synoptic scale atmospheric flow. We also find that the height of Himalaya-Tibet modifies the impact of Andean topography on northern hemisphere climate, highlighting interhemisphere climate teleconnections between the two orogens. Our results suggest that robust interpretations of climate signals recorded in geological archives in many regions on Earth are only possible when the global climatic effects of the topography of distant, off-site orogens are considered.

Reconstructions of topography and surface uplift histories of mountain ranges over geological time help constrain the geodynamic evolution of collisional domains and improve our understanding of the interactions between climate, tectonics, and surface processes. Stable isotope palaeoaltimetry is a powerful tool to estimate past surface elevations. However, recent studies suggest that knowledge of climate conditions is needed to accurately interpret the isotopic composition of water recorded in geologic archives. Furthermore, the geodynamic history of the European Alps is hypothesized to have resulted from the eastward propagation of surface uplift that could be reflected in palaeoaltimetry data. In this study we apply high-resolution isotope-tracking ECHAM5-wiso General Circulation Model (GCM) to forward-model the climate and water isotopes in meteoric water for different surface uplift histories of the Alps. Our emphasis is on understanding the climate and topographic signals preserved in the isotopic composition of precipitation (δ18Op) which is eventually recorded in paleosol carbonates. More specifically, we test the hypothesis that different topographic configurations for Eastern and Western Alps result in significantly different regional climates and spatial distributions of δ18Op. We present sensitivity experiments with two free parameters: the height of the Western/Central Alps and the height of the Eastern Alps. Results indicate a different response of δ18Op, precipitation, surface temperature, low level wind patterns and isotopic lapse rate for the different topographic scenarios. In addition, we find δ18Op locally increases up to 2‰ when the Eastern Alps are reduced to 0% of their current height, and decreases up to -8% when uplifted to 200%. The precipitation amount increases by ~60 mm/month in response to surface uplift due to orographic effects. The surface temperature locally decreases by -4°C in response Eastern Alps uplift due to both adiabatic and non-adiabatic cooling and increases by -8°C for reduced elevation scenario. The results of our study suggest that the hypothesized west-to-east surface uplift should be reflected in the isotopic composition of meteoric water. Furthermore, our simulated isotopic response to different uplift scenarios provides a basis for the interpretation of isotopic composition derived from geological archives in a stable isotope palaeoaltimetry approach.

Precipitation in wet seasons is the main driver of fluvial erosion and accounts for a significant contribution to annual erosion rates. However, wet seasons also encounter an increase in vegetation cover, which helps to resist erosion. This study quantifies the implications of present-day seasonal variations in rainfall and spatially variable vegetation cover on erosion rates over distinct climate-vegetation settings. We do this using the Landlab-SPACE landscape evolution model modified to account for weathering, rainfall-infiltration-runoff, and the effects of vegetation cover on hillslope and fluvial processes. The input parameters also include present-day SRTM DEM (90m) for the initial condition, MODIS NDVI, and weather station observations of precipitation (between 2000 – 2019). The soil properties (input parameters) and dynamically evolving soil depths were considered to estimate soil-water infiltration using the Green-Ampt method. Simulations were tuned to four selected catchments in the Chilean Coastal Cordillera (~26 °S – ~38 °S) which contains a steep climate (from arid to temperate humid) and ecological gradient with similar granodiorite lithology and tectonic forcings. The size (and mean slopes) of the catchments range from 64 (8°) – 142.5 km2 (23°). These catchments are not in steady-state with a background uplift rate of 0.05 mm yr-1. We designed multiple sets of simulations to explore the sensitivity of catchment scale erosion rates to seasonal variations in precipitation and/or vegetation cover. The simulations were conducted for 1,000 years (20 years of vegetation and precipitation observations repeated 50 times) with a time-step of 1 season (3 months). After detrending the results for long-term transient changes, the last 20 years were analyzed. Results indicate that when vegetation cover is varied but precipitation is held constant then the amplitude of change in erosion rates is very low (e.g. 17% in the humid setting). Whereas, in simulations with variable precipitation change and constant vegetation cover, and coupled variations in both precipitation and vegetation cover, the amplitude of change in erosion rates is higher and in a similar range (e.g., 95% in the humid setting). The results during wet seasons also indicate that erosion in the semi-arid region is ~2 times and ~4 times more sensitive than mediterranean and humid regions respectively. However, minimal erosion is observed in the arid setting, due to low precipitation subjected to soil infiltration which leads to lower runoff than the erosion threshold. Overall, we found that at a seasonal scale, erosion rates are significantly influenced by precipitation variations and base vegetation cover (moderately by seasonal variations). Secondly, the vulnerability of erosion rates to weather seasonality increases from humid to semi-arid regions.

The Middle Miocene (15.99–11.65 Ma) of Europe witnessed major climatic, environmental, and vegetational change, yet we are lacking detailed reconstructions of Middle Miocene temperature and precipitation patterns over Europe. Here, we use a high-resolution (∼0.75°) isotope-enabled general circulation model (ECHAM5-wiso) with time-specific boundary conditions to investigate changes in temperature, precipitation, and δ18O in precipitation (δ18Op). Experiments were designed with variable elevation configurations of the European Alps and different atmospheric CO2 levels to examine the influence of Alpine elevation and global climate forcing on regional climate and δ18Op patterns. Modeling results are in agreement with available paleobotanical temperature data and with low-resolution Middle Miocene experiments of the Miocene Model Intercomparison Project (MioMIP1). However, simulated precipitation rates are 300–500 mm/yr lower in the Middle Miocene than for pre-industrial times for central Europe. This result is consistent with precipitation estimates from herpetological fossil assemblages, but contradicts precipitation estimates from paleobotanical data. We attribute the Middle Miocene precipitation change in Europe to shifts in large-scale pressure patterns in the North Atlantic and over Europe and associated changes in wind direction and humidity. We suggest that global climate forcing contributed to a maximum δ18Op change of ∼2‰ over high elevation (Alps) and ∼1‰ over low elevation regions. In contrast, we observe a maximum modeled δ18Op decrease of 8‰ across the Alpine orogen due to Alpine topography. However, the elevation-δ18Op lapse rate shallows in the Middle Miocene, leading to a possible underestimation of paleotopography when using present-day δ18Op—elevation relationships data for stable isotope paleoaltimetry studies.

The Ekström Ice Shelf is one of numerous small ice shelves that fringe the coastline of western Dronning Maud Land, East Antarctica. Reconstructions of past ice-sheet extent in this area are poorly constrained, due to a lack of geomorphological evidence. Here, we present a compilation of geophysical surveys in front of and beneath the Ekström Ice Shelf, to identify and interpret evidence of past ice sheet flow, extent and retreat. The sea floor beneath the Ekström Ice Shelf is dominated by an incised trough, which extends from the modern day grounding line on to the continental shelf. Our surveys show that Mega-Scale Glacial Lineations cover most of the mouth of this trough, terminating 11 km away from the continental shelf break, indicating the most recent maximal extent of grounded ice in this region. Beneath the front ~30 km of the ice shelf, the sea floor is characterised by an acoustically transparent sedimentary unit, up to 45 m-thick. This is likely composed of subglacial till, further corroborating the presence of past grounded ice cover. Further inland, the sea floor becomes rougher, interpreted as a transition from subglacial tills to a crystalline bedrock, corresponding to the outcrop of the volcanic Explora Wedge at the sea floor. Ice retreat in this region appears to have happened rapidly in the centre of the incised trough, evidenced by a lack of overprinting of the lineations at the trough mouth. At the margins of the trough uniformly spaced recessional moraines suggest ice retreated more gradually. We estimate the palaeo-ice thickness at the calving front around the Last Glacial Maximum to have been at least 305 m to 320 m, based on the depth of iceberg ploughmarks within the trough and sea-level reconstructions. Given the similarity of the numerous small ice shelves around the Dronning Maud Land coast, these findings are likely representative for other ice shelves in this region and provide essential boundary conditions for palaeo ice-sheet models in this severely understudied region.

Dynamics of polar outlet glaciers vary with ocean tides, providing a natural laboratory to understand basal processes beneath ice streams, ice rheology and ice-shelf buttressing. We apply Terrestrial Radar Interferometry to close the spatiotemporal gap between localized, temporally well-resolved GNSS and area-wide but sparse satellite observations. Three-hour flowfields collected over an eight day period at Priestley Glacier, Antarctica, validate and provide the spatial context for concurrent GNSS measurements. Ice flow is fastest during falling tides and slowest during rising tides. Principal components of the timeseries prove upstream propagation of tidal signatures $>$ 10 km away from the grounding line. Hourly, cm-scale horizontal and vertical flexure patterns occur $>$6 km upstream of the grounding line. Vertical uplift upstream of the grounding line is consistent with ephemeral re-grounding during low-tide impacting grounding-zone stability. On the freely floating ice shelves, we find velocity peaks both during high- and low-tide suggesting that ice-shelf buttressing varies temporally as a function of flexural bending from tidal displacement. Taken together, these observations identify tidal imprints on ice-stream dynamics on new temporal and spatial scales providing constraints for models designed to isolate dominating processes in ice-stream and ice-shelf mechanics.

The need for geoscience students to develop a quantitative skillset is ever increasing. However, this can be difficult to implement in university-style lecture courses in a way that is both manageable for the instructor and does not involve lengthy, potentially repetitive, question sheets for the students. Here, a method for teaching dimensional analysis, basic fluid dynamics, and the interpretation and scaling of experimental data is presented for a graduate student audience. The proposed method utilizes simple fluid dynamic benchtop experiments that require a small amount of teaching space and use readily available, low cost materials. Our analysis of student performance through pre- and post-tests demonstrates that students have a better knowledge of dimensional analysis, data interpretation and experimental design after the series of practical sessions compared to instruction through a single, passive lecture. We therefore show that simple benchtop experiments can be an effective way to improve and integrate quantitative learning into a graduate geoscience class.

The Qaidam Basin (QB) in the northeastern Tibetan Plateau held a megalake system during the Pliocene. Today, the lower elevations in the basin are hyperarid. To understand to what extent the climate plays a role in the maintenance of the megalake system during the Pliocene, we applied the Weather Research and Forecasting model for dynamical downscaling of ECHAM5 global climate simulations for the present day and the mid���Pliocene. When imposing the mid���Pliocene climate on the QB with its modern land surface settings, the annual water balance (��S), that is, the change in terrestrial water storage within the QB, increases. This positive imbalance of ��S induced solely by the changes in the large���scale climate state would lead to a readjustment of lake extent, until a new equilibrium state is reached, where loss due to evaporation over lake areas compensates for the input by runoff and precipitation. Atmospheric water transport (AWT) analysis at each border of the QB reveals that this imbalance of ��S is caused by stronger moisture influx across the western border in winter, spring, and autumn and weaker moisture out���flux across the eastern border in summer. These changes in AWT are associated with the strengthening of the midlatitude westerlies in all seasons, except for summer, and the intensification of the East Asian Summer Monsoon. Given that the mid���Pliocene climate is an analog to the projected warm climate of the near future, our study contributes to a better understanding of climate change impacts in central Asia., Key Points: ECHAM5 global climate simulations for the present day and the mid���Pliocene were dynamically downscaled over the Qaidam Basin (QB). Results show a positive imbalance in water balance when the mid���Pliocene climate is imposed on the QB with its modern surface settings. This imbalance in water balance is closely associated with changes in the midlatitude westerlies and in the East Asian Summer Monsoon., Bundesministerium f��r Bildung und Forschung (BMBF) http://dx.doi.org/10.13039/501100002347, Technische Universit��t Berlin

Many studies have recently shown the potential of geophysical tools in bridging the information gap between individual point-scale measurements. Here, we upscale and extend the point-scale layering information from pedons (excavated pit of 1 m2) using geophysical methods. We applied multi-frequency ground-penetrating radar (GPR) in four study areas in the extreme climate and vegetation gradient of the Chilean Coastal Cordillera. The main goals of this study were to understand how granitic based regolith material varies depending on climate, vegetation cover, aspect, and topography. GPR was successfully used in all four study areas. Reflections, which were imaged up to a depth of 8 m, could be associated with boundaries visible in the pedons. The main recognizable reflections were linked with the interface between the mobile soil and the immobile saprolite. This boundary is characterized by hyperbolic-shape features, probably connected to heterogeneities (e.g. pebbles). A deeper GPR penetration depth in south-facing hillslopes was observed than in north-facing hillslopes. This is probably due to less sun exposure in the south facing slopes, which results in higher soil water content and denser plant growth, facilitating weathering processes. Furthermore, thicker layers in the GPR profiles are visible going from north to south along the latitude. Most of these observations were in agreement with the soil pedons. These results demonstrate the utility of the GPR technique for characterizing subsurface variations in regolith properties (e.g. thickness, boundaries). Additional soil pedons should be excavated based on GPR results. Applying noninvasive geophysical methods could improve the understanding of the interactions between soil formation, vegetation, and other environmental parameters.

Assessing paleo-climatic changes and the underlying driving mechanisms are an essential (and often poorly understood) first-step for understanding if natural variability in Earth's climate system from tectonic processes and orbital forcing could produce observed changes in surface processes. In this study, we take this first step of evaluating climate change in the Tibetan Plateau region for different distinct climate states. We do this using a high-resolution regional climate model parameterized for the Cenozoic rise of the Plateau and prominent Quaternary glacial and interglacial episodes. The main objective is to delimit the range of climate variability due to important natural drivers in the region by comparing climate changes during the main Cenozoic uplift period with climate anomalies during the last glacial maximum and the mid-Holocene optimum. This helps to interpret environmental changes documented by proxy data and to benchmark man-made climate changes expected during the 21st century. The innovative aspects of this study pertain to the use of a consistent high-resolution modeling framework and a multivariate statistical assessment of climate types and their shift during the various paleo-climatic episodes. Reduced plateau elevation leads to regionally differentiated patterns of higher temperature and lower precipitation amounts on the plateau itself, whereas surrounding regions are subject to colder conditions. In particular, Central Asia receives much more precipitation prior to the uplift, mainly due to a shift of the stationary wave train over Eurasia. Cluster analysis indicates that the continental-desert type climate, which is widespread over Central Asia today, appears with the Tibetan Plateau reaching 50% of its present-day elevation. The mid-Holocene is characterized by slightly colder temperatures, and the last glacial maximum by considerably colder conditions over most of central and southern Asia. Precipitation anomalies during these episodes are less pronounced and spatially heterogeneous over the Tibetan Plateau. The simulated changes are in good agreement with available paleo-climatic reconstructions from proxy data. The present-day climate classification is only slightly sensitive to the changed boundary conditions in the Quaternary. However, it is shown that in some regions of the Tibetan Plateau the climate anomalies during the Quaternary have been as strong as the changes occurring during the uplift period.

Conventional (U-Th(-Sm))/He thermochronology requires accurate determination of the grain shape and dimension for calculation of 4He loss by alpha particle ejection and diffusion. In routine practice, calculations of 4He loss and diffusion are calculated assuming that measured grains approximate symmetric grain shapes with perfectly smooth crystal surfaces. This may introduce uncertainties that are virtually impossible to quantify if grains that do not pass the latter criteria are used. Alternatively, this leads to a selection bias for the analyses of detrital minerals if only grains with perfect crystal surfaces are measured. To address this limitation, we introduce a flexible, open-source numerical approach in Matlab™ to accurately determine the three-dimensional grain shape and numerically model He loss by alpha ejection and diffusion on individual grains. The three-dimensional surface of a mineral grain is interpolated from photomicrographs taken orthogonal to the principal grain axes. He ejection and diffusion is simulated using a coupled Monte Carlo and Brownian motion algorithm. Comparing our approach to high-resolution X-ray microtomography, we demonstrate that our “3D-He” approach improves the accuracy of He loss corrections when mineral grains do not approximate perfect crystal shapes by avoiding constraints inherent to standard manual-analytical approaches. Importantly, this method mitigates any bias introduced by user-dependent grain selection, measurements and assigning grains to a mineral shape for which analytical solutions of He production have been derived. In routine practice, we find that our 3D-He approach improves the accuracy of geometric measures (volume and surface area) and associated sphere-equivalent radii (SER) significantly, reducing the average deviation from true values from ~7–8% (manual-analytical approach) to ~2.5% (3D-He approach). The difference in SER significantly impacts the resulting apatite (U-Th-Sm)/He ages, which may deviate up to 40% when long held at temperatures where He production roughly matches diffusive loss of He. Using the 3D-He approach, the average deviation and overall spread of He loss corrections due to alpha ejection (FT factors) could be reduced from 1.6 ± 4.6% to 0.6 ± 0.8%. In summary, our 3D-He approach is a significant refinement to (U-Th(-Sm))/He age calculation considering relatively low analytical uncertainty in U, Th, Sm and He measurement (~2%). Importantly, our 3D-He approach should mitigate the selection bias introduced through manual grain selection. Toward this end, we discuss additional advantages of our numerical approach to handling broken grains or grains with known parent isotope zonation.