Glacial isostatic uplift of the European Alps

Following the last glacial maximum (LGM), the demise of continental ice sheets induced crustal rebound in tectonically stable regions of North America and Scandinavia that is still ongoing. Unlike the ice sheets, the Alpine ice cap developed in an orogen where the measured uplift is potentially attributed to tectonic shortening, lithospheric delamination and unloading due to deglaciation and erosion. Here we show that ∼90% of the geodetically measured rock uplift in the Alps can be explained by the Earth's viscoelastic response to LGM deglaciation. We modelled rock uplift by reconstructing the Alpine ice cap, while accounting for postglacial erosion, sediment deposition and spatial variations in lithospheric rigidity. Clusters of excessive uplift in the Rhône Valley and in the Eastern Alps delineate regions potentially affected by mantle processes, crustal heterogeneity and active tectonics. Our study shows that even small LGM ice caps can dominate present-day rock uplift in tectonically active regions

Physical Limnology and Sediment Dynamics of Lago Argentino, the World's Largest Ice-Contact Lake

Proglacial lakes, whose numbers have been growing around the world, may drive accelerated glacier retreat and provide valuable records of past glacier and climatic changes. Despite their importance, few studies have investigated the sedimentary properties and processes acting within large proglacial lakes. Lago Argentino (LArg) is a 1,500 km2 ice-contact lake on the eastern flank of the Southern Patagonian Icefield. Here, we describe the results from a detailed analysis of 47 sediment cores obtained throughout this lake basin, supplemented with remotely sensed data. We show that: (a) LArg exhibits a seasonal variation in sediment properties (varves); (b) varve formation results from three distinct processes, driven by seasonal changes in glacial sediment input, seasonal changes in fluvial sediment input, and seasonal variations in lake mixing; and (c) distance from glacier calving fronts provides the first-order control on sediment grain size and accumulation rate. Our findings highlight the exceptional preservation of annual laminations within proglacial lakes, their potential for reconstructing past glacier changes, and their relevance for forecasting future glacier–lake interactions.Fil: Van Wyk de Vries, Maximillian. University of Minnesota; Estados UnidosFil: Ito, Emi. University of Minnesota; Estados UnidosFil: Shapley, Mark. University of Minnesota; Estados UnidosFil: Brignone, Guido. Universidad Nacional de Córdoba; ArgentinaFil: Romero, Matias. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Wickert, Andrew D.. German Research Centre for Geosciences; Alemania. University of Minnesota; Estados UnidosFil: Miller, Louis H.. Macalester College; Estados UnidosFil: MacGregor, Kelly R.. Macalester College; Estados Unido

Collapse of the North American ice saddle 14,500 years ago caused widespread cooling and reduced ocean overturning circulation

Collapse of ice sheets can cause significant sea level rise and widespread climate change. We examine the climatic response to meltwater generated by the collapse of the Cordilleran-Laurentide ice saddle (North America) ~14.5 thousand years ago (ka) using a high-resolution drainage model coupled to an ocean-atmosphere-vegetation general circulation model. Equivalent to 7.26 m global mean sea level rise in 340 years, the meltwater caused a 6 sverdrup weakening of Atlantic Meridional Overturning Circulation (AMOC) and widespread Northern Hemisphere cooling of 1–5°C. The greatest cooling is in the Atlantic sector high latitudes during Boreal winter (by 5–10°C), but there is also strong summer warming of 1–3°C over eastern North America. Following recent suggestions that the saddle collapse was triggered by the Bølling warming event at ~14.7–14.5 ka, we conclude that this robust submillennial mechanism may have initiated the end of the warming and/or the Older Dryas cooling through a forced AMOC weakening

What are the drivers of Caspian Sea level variation during the late Quaternary?

Quaternary Caspian Sea level variations depended on geophysical processes (affecting the opening and closing of gateways and basin size/shape) and hydro-climatological processes (affecting water balance). Disentangling the drivers of past Caspian Sea level variation, as well as the mechanisms by which they impacted the Caspian Sea level variation, is much debated. In this study we examine the relative impacts of hydroclimatic change, ice-sheet accumulation and melt, and isostatic adjustment on Caspian Sea level change. We performed model analysis of ice-sheet and hydroclimate impacts on Caspian Sea level and compared these with newly collated published palaeo-Caspian sea level data for the last glacial cycle. We used palaeoclimate model simulations from a global coupled ocean-atmosphere-vegetation climate model, HadCM3, and ice-sheet data from the ICE-6G_C glacial isostatic adjustment model. Our results show that ice-sheet meltwater during the last glacial cycle played a vital role in Caspian Sea level variations, which is in agreement with hypotheses based on palaeo-Caspian Sea level information. The effect was directly linked to the reorganization and expansion of the Caspian Sea palaeo-drainage system resulting from topographic change. The combined contributions from meltwater and runoff from the expanded basin area were primary factors in the Caspian Sea transgression during the deglaciation period between 20 and 15 kyr BP. Their impact on the evolution of Caspian Sea level lasted until around 13 kyr BP. Millennial scale events (Heinrich events and the Younger Dryas) negatively impacted the surface water budget of the Caspian Sea but their influence on Caspian Sea level variation was short-lived and was outweighed by the massive combined meltwater and runoff contribution over the expanded basin

Forecasting the response of Earth's surface to future climatic and land use changes: a review of methods and research needs

In the future, Earth will be warmer, precipitation events will be more extreme, global mean sea level will rise, and many arid and semiarid regions will be drier. Human modifications of landscapes will also occur at an accelerated rate as developed areas increase in size and population density. We now have gridded global forecasts, being continually improved, of the climatic and land use changes (C&LUC) that are likely to occur in the coming decades. However, besides a few exceptions, consensus forecasts do not exist for how these C&LUC will likely impact Earth-surface processes and hazards. In some cases, we have the tools to forecast the geomorphic responses to likely future C&LUC. Fully exploiting these models and utilizing these tools will require close collaboration among Earth-surface scientists and Earth-system modelers. This paper assesses the state-of-the-art tools and data that are being used or could be used to forecast changes in the state of Earth's surface as a result of likely future C&LUC. We also propose strategies for filling key knowledge gaps, emphasizing where additional basic research and/or collaboration across disciplines are necessary. The main body of the paper addresses cross-cutting issues, including the importance of nonlinear/threshold-dominated interactions among topography, vegetation, and sediment transport, as well as the importance of alternate stable states and extreme, rare events for understanding and forecasting Earth-surface response to C&LUC. Five supplements delve into different scales or process zones (global-scale assessments and fluvial, aeolian, glacial/periglacial, and coastal process zones) in detail

Forecasting the Response of Earth\u27s Surface to Future Climatic and Land Use Changes: A Review of Methods and Research Needs

In the future, Earth will be warmer, precipitation events will be more extreme, global mean sea level will rise, and many arid and semiarid regions will be drier. Human modifications of landscapes will also occur at an accelerated rate as developed areas increase in size and population density. We now have gridded global forecasts, being continually improved, of the climatic and land use changes (C&LUC) that are likely to occur in the coming decades. However, besides a few exceptions, consensus forecasts do not exist for how these C&LUC will likely impact Earth-surface processes and hazards. In some cases, we have the tools to forecast the geomorphic responses to likely future C&LUC. Fully exploiting these models and utilizing these tools will require close collaboration among Earth-surface scientists and Earth-system modelers. This paper assesses the state-of-the-art tools and data that are being used or could be used to forecast changes in the state of Earth\u27s surface as a result of likely future C&LUC. We also propose strategies for filling key knowledge gaps, emphasizing where additional basic research and/or collaboration across disciplines are necessary. The main body of the paper addresses cross-cutting issues, including the importance of nonlinear/threshold-dominated interactions among topography, vegetation, and sediment transport, as well as the importance of alternate stable states and extreme, rare events for understanding and forecasting Earth-surface response to C&LUC. Five supplements delve into different scales or process zones (global-scale assessments and fluvial, aeolian, glacial/periglacial, and coastal process zones) in detail

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Experimental alluvial-river and landsliding response to base-level fall

All files with time-dependent data contain 7-digit time stamps that provide the number of seconds since the start of each experiment. (1) Georeferenced overhead photos in GeoTIFF format within a Tape ARchive (tar). (2) Digital elevation models in GeoTIFF format within a GZipped Tape ARchive (tar.gz). (3) Landslide GIS vector areas (polygons) organized by experiment and time as ESRI Shapefiles stored within a GZipped Tape ARchive (tar.gz). Each subfolder is labeled .shx (the ".shx" is spurious) and contains the shp, shx, dbf, and prj files associated with each set of landslides at each time in the experiment. (4) Landslide attributes as comma-separated variables (csv) files for each experiments, stored within an XZipped Tape ARchive (tar.xz). Each CSV includes (in order): the x and y positions of the landslide center, the width (y-directed – i.e., cross-valley – distance from one end to the other) and length (x-directed – i.e., down-valley – distance from one end to the other) of the landslide, mean landslide depth, landslide area measured in the x-y (i.e., horizontal) plane, the semi-major and semi-minor axes of an ellipse fit to the landslide, the angle from the semi-major axis to the "horizontal" (confusingly meaning the x orientation, since I was thinking in x-y space while writing the analysis code), landslide volume calculated by subtracting the valley-bottom elevation from that of the DEM surface in the landslide area, the runtime at which the landslide occurs, and the wait time between landslide events. (5) Movies at 15 fps (5 minutes experiment time per 1 second watch time) for the full series of images from each experiment, stored within an XZipped Tape ARchive (tar.xz). I did not adjust for occasional skipped images (e.g., around the time of the laser scans), which will cause minor deviations from the 5-minutes-runtime-to-1-second-video conversion. (6) Schematic image (png) of a georeferenced overhead photo (ImgSec_0043168) atop a shaded-relief map (DEM_fullextent_0043188) with hatched landslide locations from runtimes after 0043168. Shadows running along the x axis show zones near the outlet where the basin walls prevented the angled laser-topography scanner from casting light on the the valley bottom. All images are from the 25 mm/hr base-level fall experiment.We observed the incisional response of an alluvial river to base-level fall. We conducted the experiment in a 3.9 × 2.4 × 0.4 m box that we filled with uniform 0.140±0.04 mm sand. We dropped base level by lowering the elevation of an "ocean" pool at the river outlet. As the initial condition, we cut a 10±2 cm wide channel to a steadily increasing depth, from 3±0.5 cm at the inlet, where we supplied water and sediment, to 10±1 cm at the outlet. Input water and sediment discharge were 0.1 L/s and 0.0022 L/s (including pore space), respectively. As base level fell, the river incised and migrated laterally, forming a valley with abandoned terrace surfaces and walls that failed in mass-wasting events as they were undercut. We include a control case with no base-level fall, as well as experiments with 25 mm/hr, 50 mm/hr, 200 mm/hr, 300 mm/hr, and 400 mm/hr of base-level fall. We supply georeferenced overhead photos (0.89 mm resolution, every 20 seconds), digital elevation models (DEMs, 1 mm horizontal resolution, every 15–30 minutes), videos generated from the overhead photos, mapped landslides in GIS vector area (polygon) format, and landslide attributes. Relevant code to process and plot the data, as well as further information on grain size, is available from GitHub and Zenodo.Start-up funds to A. Wickert from the University of MinnesotaRichard C. Dennis Fellowship awarded by the Department of Earth Sciences to O. Beaulie