Aeolian (wind-blown) sand dunes occupy 10% of the Earth's surface, both in vast desert sand seas and as important natural defences against flooding along coasts. While the environmental conditions that influence the shape, movement and patterns of fully grown dunes have been extensively studied, arguably the most enduring deficiency in our understanding of these landforms is also the most profound: how do wind-blown dunes initiate? Initiation is central to understanding dunes as major geological units, including the response of these landscapes to climatic drivers, environmental change and societal impact. The significance of dune initiation for the wider understanding of wind-blown sandy systems and their contexts, for which the discovery of extra-terrestrial dune fields has added a recent impetus, ensures that the question of initiation has remained prominent throughout the history of desert research. Despite this, existing ideas proposed to explain processes of dune origin have remained largely descriptive and uncorroborated. The persistence of the question regarding dune initiation is not due to an absence of appreciation of its importance but, rather, a lack of the means to tackle this fundamental issue. The critical obstacle to a fully developed understanding of dune initiation is that, until now, measurement of the necessary variables, at the ultra-high spatial and temporal resolutions required to detect small-scale variations in surface conditions and wind-blown sand transport, has been impossible. Recent technological advances in the geosciences both inspire and underpin this proposal, as they now provide the opportunity to meet the demanding requirements of process measurement. Surmounting the abiding problem of dune initiation requires novel approaches in research design and our proposal tackles the issues of measurement at small scales by forging complementary links between fieldwork and physical modelling, as well as an ability to widen the application of detailed process findings through computer modelling. Specifically, this proposal will for the first time examine the key inter-relationships between airflow, surface properties, changes in sand transport and bedform shape that lie behind a meaningful understanding of how nascent dunes emerge. Full measurement of controlling processes and bedform development will be achieved through field monitoring of surface properties and bedform change at extremely high resolution. A key novelty of the fieldwork is that it will be carried out at three carefully chosen locations of known dune development, with each location representing the 'type site' for three different drivers of dune initiation; surface roughness, surface moisture and sand bed instability. The fieldwork will inform experiments undertaken in a bespoke laboratory flume that is designed to enable accurate characterisation of flow very close to the 3D surface of modelled dunes using state-of-the-art imaging techniques. Our field and laboratory dataset will be used to drive a computer model that we will then run to test the sensitivity of dune initiation and growth to different controls in a range of environmental conditions in deserts, coasts and on other planets. Our proposal is built on a new capability to make field observations at the requisite exceptional levels of detail, augmented by closely coupled state-of-the-art laboratory flow simulations, plus the development and application of evidence-based modelling to examine drivers of dune initiation. In concert, this approach represents an unprecedented opportunity to overcome a truly enduring plateau for understanding the origins of one of the major terrestrial landform systems.

Understanding when, where, and how windblown dust is emitted from deserts is important because dust can be detrimental to human health, can pollute downwind environmental systems, and, when airborne, can influence climate. Desert dust can also be rich in iron and other nutrients so when it falls into oceans downwind of its desert source, it can stimulate the productivity of marine biota in the surface waters. The impact of this is especially important in certain sensitive coastal areas where the mixing of cold water occurs close to the shore, such as at the Atacama and Namib Desert coastlines. These coastal waters can be particularly receptive to the nutrients that deposited dust might be providing. The UK Team have undertaken research on windblown dust in southern African deserts for many years. Our approach has been to use satellite observations to identify the sources of dust in different areas of the desert landscape, and then install state-of-the-art monitoring and survey equipment in these 'hot-spots' of dust emission to measure the wind and surface characteristics that control how and when dust is eroded by the wind. Our data have allowed improvements to be made in models of windblown dust emission into the atmosphere, and have also shown the significance of deposited dust in the fertilisation of the South Atlantic Ocean. The Atacama Desert is similar in many interesting respects to the Namib Desert in southern Africa. Both deserts are located on continental west coasts, fringed by cold ocean currents to the west and steep topography to the east. They have similar types of landscapes with a mix of dry river valleys, stony plains, and salty dry lakes. In the Namib, such surfaces have been shown to be prone to wind erosion and the generation of dust storms. However, whilst we know that winds generate dust in the Atacama Desert, we know very little about when and where such storms occur, or whether the dust contains iron which might affect the nutrient levels in the adjacent ocean waters. Our aim is to start a new collaboration of scientists from Chile, the UK, and Namibia to begin to answer these questions and determine the impacts of and controls on windblown dust in the Atacama Desert. We wish to achieve an understanding of the relevant processes in the Atacama which is as good as that which we have gained in the Namib. This research will bring together researchers from the UK and Namibia who have expertise in identifying sites of dust erosion (termed emission 'hot-spots') in Namibia, and a Chilean researcher who has expertise on the Atacama wind erosion system. Together this new team will establish, for the first time and at high resolution, where dust in the region comes from (using satellite images to identify 'hot-spots'), and how frequently dust storms occur. The team will then undertake fieldwork to explore the surface ground conditions at these 'hot-spots' and, at specific sites, install instruments to directly measure the amount of dust that is being eroded. Based on the outputs from this project, the team will develop a long-term collaborative relationship that will explore the effects of dust in the Atacama region in more detail through additional grant proposals. This will include investigating the influence of climate cycles on the efficiency of wind erosion, how important dust in this region is for ocean productivity, and the significance of human impact, such as mining, on generating windblown dust.