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In this work we present a unique set of coincident and collocated high‐resolution observations of surface currents and directional properties of surface waves collected from an airborne instrument, the Modular Aerial Sensing System, collected off the coast of Southern California. High‐resolution observations of near surface current profiles and shear are obtained using a new instrument, "DoppVis", capable of capturing horizontal spatial current variability down to 128 m resolution. This data set provides a unique opportunity to examine how currents at scales ranging from 1 to 100 km modulate bulk (e.g., significant wave height), directional and spectral properties of surface gravity waves. Such observations are a step toward developing better understanding of the underlying physics of submesoscale processes (e.g., frontogenesis and frontal arrest) and the nature of transitions between mesoscale and submesoscale dynamics. Plain Language Summary: In recent years, through improvement of computational resolution of global ocean models, scientists have begun to suspect that kilometer‐scale eddies, whirlpools and fronts, called "submesoscale" variability, make important contributions to horizontal and vertical exchange of climate and biological variables in the upper ocean. Such features are challenging to analyze, because of their size (and how quickly they evolve; within hours), they are too large to study from a research vessel but smaller than regions typically studied with satellite measurements. In this work, we use a research aircraft instrumented to characterize ocean currents, temperature, color (in turn chlorophyll concentration) and the properties of surface waves over an area large enough to capture submesoscale processes. This approach is a step forward in understanding and quantifying the underlying physics of submesoscale processes, and in turn develops parameterization that can help improve the fidelity of weather and climate models. Key Points: Unique coincident and collocated airborne observations of Sea Surface Temperature, surface currents and properties of surface waves across submesoscales featuresA new airborne instrument enables observations of surface currents, vertical and horizontal shear to capture quickly evolving ocean featuresSuch observations are crucial to develop better understanding of the physics of submesoscale processes and wave‐current interaction [ABSTRACT FROM AUTHOR]

Airborne lidar altimetry can measure the sea surface height (SSH) over scales ranging from hundreds of kilometers to a few meters. Here, we analyze the spectrum of SSH observations collected during an airborne lidar campaign conducted off the California coast. We show that the variance in the surface wave band can be over 20 times larger than the variance at submesoscales and that the observed SSH variability is sensitive to the directionality of surface waves. Our results support the hypothesis that there is a spectral gap between meso‐to‐submesoscale motions and small‐scale surface waves and also indicate that aliasing of surface waves into lower wavenumbers may complicate the interpretation of SSH spectra. These results highlight the importance of better understanding the contributions of different physics to the SSH variability and considering the SSH spectrum as a continuum in the context of future satellite altimetry missions. Plain Language Summary: Using unique measurements of the sea surface height (SSH) taken from an instrument onboard an airplane off the California coast, we examine how the variance of the SSH is distributed across different spatial scales, ranging from hundreds of kilometers to a few meters. We show that surface waves can be 20 times more energetic than motions with larger scales (known as submesocales) and that the direction of surface waves impacts the SSH variability depending on different sampling and averaging strategies. These results highlight the importance of better understanding the contributions of different types of motions and physics to the SSH variability. In particular, we advocate measuring scales from meters to hundreds of kilometers as a continuum to better inform future satellite altimetry missions. Key Points: We present unique broadband airborne lidar observations of sea surface height spanning scales from hundreds of kilometers to a few metersThe sea surface height variance due to surface waves can be over an order of magnitude larger than the variance at submesoscalesThe observed sea surface height is sensitive to the direction of waves which may impact the interpretation of remote sensing measurements [ABSTRACT FROM AUTHOR]

This paper presents a detailed analysis of a dramatic rock slope acceleration that occurred in fall 2016 at the Moosfluh Landslide, located at the glacier tongue of the Great Aletsch Glacier (Switzerland). The acceleration that occurred in 2016 was unanticipated and exposed the valley bottom and an adjacent damned lake to high risk. This acceleration occurred in an active deep‐seated gravitational slope deformation (DSGSD) controlled primarily by deep block‐flexural toppling. In 2013, a highly accurate displacement monitoring system was developed and installed in the surroundings of the Great Aletsch Glacier, including a time‐lapse camera, GNSS, and robotic total stations. This monitoring system provided unique data during the 2016 slope acceleration which are used in this study to assess failure mechanisms, landslide volumes, and subsurface displacement geometry. Based on a novel displacement vector analysis, we find that three retrogressive secondary rockslides developed during the first six weeks of the slope acceleration, with rupture surface depths of 30 to 40 m, and estimated volumes between 1 and 4 Mm3. These rockslides display complex deformation features, including head and lateral scarps, which developed during the slope acceleration. The kinematics of these secondary rockslides changed through time, from primarily toppling to combined toppling and sliding. Our results provide a uniquely detailed understanding of the spatial and temporal evolution of deformation features and movement kinematics that occur when several sectors of a slowly moving DSGSD transitions into rapid rockslides. Plain Language Summary: The slow moving (~30 cm per year) deep‐seated (up to 170‐m depth) landslide of Moosfluh experienced a substantial acceleration of slope movement in September 2016. A comprehensive monitoring system recorded that several compartments in the center of the Moosfluh Landslide suddenly started to move rapidly with velocities of up to several meters per week. This caused a strong modification of the slope surface morphology and structure which is documented in detail in this study. Based on monitored changes in the directions of slope movement over time, a new method was developed to interpret subsurface movement types and geometries. With this method we found that on top of the Moosfluh deep‐seated landslide several shallow (30–40 m) rockslides developed during the Moosfluh slope acceleration in 2016. We are able to assign depths and inclinations of the failure surfaces and failure mechanisms. In this case the deep‐seated landslide is formed by rotation (toppling) of steep rock columns, whereas the shallow secondary rockslides within the deep‐seated landslide show sliding movements along planar rupture planes and mixtures of both sliding and toppling. Key Points: The rapid formation of 3 secondary rockslides within a toppling mode DSGSD (Moosfluh, CH) is monitored with DIC from webcam images, aerial photogrammetry and total station monitoringThis transition corresponds to an acceleration of the landslide from a few dm/a to 50 m/a in the lowermost sectors of the instabilityA novel method developed to interpret total station reflector data revealed a change in landslide kinematics (toppling, sliding) through time [ABSTRACT FROM AUTHOR]