Abstract. Automated electronic data loggers revolutionized environmental monitoring by enabling reliable high-frequency measurements. However, the potential to monitor the complex environmental interactions involved in global change has not been fully realized due to the high cost and lack of modularity of commercially available data loggers. Responding to this need, we developed the ALog series of open-source data loggers, based on the popular and easy-to-program Arduino microcontroller platform. ALog data loggers are low cost, lightweight, and low power; they function between −30 °C and +60 °C, can be powered by readily available consumer-grade batteries and solar panels, and can store up to 32 GB of data locally. They are compatible with standard environmental sensors, and the ALog firmware library may be expanded to add additional sensor support. The end-product is a set of robust and field-tested scientific instrumentation that is the direct descendant of dozens of individuals' contributions to the growing open-source electronics movement.

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<p>Gravel-bed rivers cross and sculpt Earth's upland regions. Field, flume, and theoretical studies together provide governing equations for these rivers. Building upon this rich background, we quantitatively link catchment-scale hydrology, sediment transport, and morphodynamics into a model of river long-profile change over time. We focus on the transport-limited case (i.e., alluvial rivers), as most rivers around the world expend the majority of their geomorphic work by moving sediment rather than eroding the underlying substrate. Morphologically, this "transport-limited" category includes all alluvial rivers as well as those bedrock rivers for which bedrock erosion is easy relative to sediment transport. This model provides predictions for how such systems respond to changes in water supply, sediment supply, and base level – which are often linked to climate, land use, and tectonics. After deriving the central equation for long-profile evolution, we demonstrate that river concavity is strongly determined by the attrition rate of gravel, which can occur by either hillslope weathering or downstream fining. This dependency creates the potential for significant feedbacks between climate, tectonics, lithology, and river morphology. Furthermore, the equation predicts that oscillations in sediment and water supply will lead to net river incision when compared to steady means of both quantities. If true, this theoretical prediction could help to explain the near-ubiquitous presence of river terraces around the world.</p>

<p>Periodic variation in Earth's orbit leads to variation in temperature and precipitation at its surface that are expected to exert a profound influence on landscape evolution. Indeed, cyclical fluctuations in sediment yield and grain size are a ubiquitous feature of the geological record, and recurrence times of geomorphological features such as fluvial terraces and alluvial fans often appear to reflect orbital periodicities. However, making quantitative interpretations of these records requires a detailed understanding of the ways in which sediment is transported from mountainous source regions along alluvial channels to depositional sinks. Sediment transport processes may dampen (i.e. buffer, 'shred') or amplify climate signals, such as changes in channel elevation or sediment flux, and may introduce a lag between them and the responsible external forcing. Recent modelling studies, mostly focused on the potential transmission of climatic signals to sedimentary archives, have predicted a wide range of behaviour and have proven challenging to test in the field. Here, we aim to clarify this discussion and also consider the potential preservation of climatic signals by fluvial terraces along alluvial channels. Our starting point is a recently developed model describing the long-profile evolution of gravel-bed rivers. This model is the first of its kind to be derived from first principles using physical relationships that have been extensively tested in laboratory settings, and takes a non-linear diffusive form. We employ perturbation theory to obtain approximate analytical solutions to the relevant equations that describe how channel elevation and sediment flux vary in response to periodic fluctuations in discharge and sediment supply. Our solutions contain expressions for response amplitudes and lag times as functions of downstream distance, system 'diffusivity' and forcing frequency. Lag times can be a significant fraction of the forcing period, implying that care is required when interpreting the timings of terrace formation in terms of changes in discharge or sediment supply. We also show that at the onset of periodic forcing, or a change in the dominant forcing period, alluvial channels undergo a transient response as they adjust to a new quasi-steady state. Importantly, this result implies that suites of fluvial terraces can be preserved without the need for significant local base-level fall. Since the expressions presented here are defined in terms of fundamental properties of alluvial channels, they should be readily applicable to real settings.</p>