High-resolution topographic surveying is traditionally associated with high capital and logistical costs, so that data acquisition is often passed on to specialist third party organizations. The high costs of data collection are, for many applications in the earth sciences, exacerbated by the remoteness and inaccessibility of many field sites, rendering cheaper, more portable surveying platforms (i.e. terrestrial laser scanning or GPS) impractical. This paper outlines a revolutionary, low-cost, userfriendly photogrammetric technique for obtaining high-resolution datasets at a range of scales, termed 'Structure-from-Motion' (SfM). Traditional softcopy photogrammetric methods require the 3-D location and pose of the camera(s), or the 3-D location of ground control points to be known to facilitate scene triangulation and reconstruction. In contrast, the SfM method solves the camera pose and scene geometry simultaneously and automatically, using a highly redundant bundle adjustment based on matching features in multiple overlapping, offset images. A comprehensive introduction to the technique is presented, followed by an outline of the methods used to create high-resolution Digital Elevation Models (DEMs) from extensive photosets obtained using a consumer-grade digital camera. As an initial appraisal of the technique, an SfM-derived DEM is compared directly with a similar model obtained using Terrestrial Laser Scanning. This intercomparison reveals that decimetre-scale vertical accuracy can be achieved using SfM even for sites with complex topography and a range of land-covers. Example applications of SfM are presented for three contrasting landforms across a range of scales including; an exposed rocky coastal cliff; a breached moraine-dam complex; and a glaciallysculpted bedrock ridge. The SfM technique represents a major advancement in the field of photogrammetry for geoscience applications. Our results and experiences indicate SfM is an inexpensive, effective, and flexible approach to capturing complex topography.

This study provides a detailed structural glaciological analysis of changes in surface structures on the Larsen B ice shelf on the Antarctic Peninsula prior to its collapse in February–March 2002. Mapped features include the ice-shelf front, rifts, crevasses, longitudinal linear surface structures and meltwater features. We define domains on the ice shelf related to glacier source areas and demonstrate that, prior to collapse, the central Larsen B ice shelf consisted of four sutured flow units fed by Crane, Jorum, Punchbowl and Hektoria/Green/Evans glaciers. Between these flow units were ‘suture zones’ of thinner ice where the feeder glaciers merged. Prior to collapse, large open-rift systems were present offshore of Foyn Point and Cape Disappointment. These rifts became more pronounced in the years preceding break-up, and ice blocks in the rifts rotated because of the strong lateral shear in this zone. Velocity mapping of the suture zones indicates that the major rifts were not present more than about 20 years ago. We suggest that the ice shelf was preconditioned to collapse by partial rupturing of the sutures between flow units. This, we believe, was the result of ice-shelf front retreat during 1998–2000, reducing the lateral resistive stress on the upstream parts of the shelf and glacier flow units, ice-shelf thinning and pre-shelf-break-up glacier acceleration.

This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.epsl.2015.09.004Many Himalayan glaciers are characterised in their lower reaches by a rock debris layer. This debris insulates the glacier surface from atmospheric warming and complicates the response to climate change compared to glaciers with clean-ice surfaces. Debris-covered glaciers can persist well below the altitude that would be sustainable for clean-ice glaciers, resulting in much longer timescales of mass loss and meltwater production. The properties and evolution of supraglacial debris present a considerable challenge to understanding future glacier change. Existing approaches to predicting variations in glacier volume and meltwater production rely on numerical models that represent the processes governing glaciers with clean-ice surfaces, and yield conflicting results. We developed a numerical model that couples the flow of ice and debris and includes important feedbacks between debris accumulation and glacier mass balance. To investigate the impact of debris transport on the response of a glacier to recent and future climate change, we applied this model to a large debris-covered Himalayan glacier-Khumbu Glacier in Nepal. Our results demonstrate that supraglacial debris prolongs the response of the glacier to warming and causes lowering of the glacier surface in situ, concealing the magnitude of mass loss when compared with estimates based on glacierised area. Since the Little Ice Age, Khumbu Glacier has lost 34% of its volume while its area has reduced by only 6%. We predict a decrease in glacier volume of 8-10% by AD2100, accompanied by dynamic and physical detachment of the debris-covered tongue from the active glacier within the next 150 yr. This detachment will accelerate rates of glacier decay, and similar changes are likely for other debris-covered glaciers in the Himalaya. (C) 2015 Elsevier B.V. All rights reserved.authorsversionPeer reviewe

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Bentley, M. J., Ocofaigh, C., Anderson, J. B., Conway, H., Davies, B., Graham, A. G. C., Hillenbrand, C. D., Hodgson, D. A., Jamieson, S. S. R., Larter, R. D., Mackintosh, A., Smith, J. A., Verleyen, E., Ackert, R. P., Bart, P. J., Berg, S., Brunstein, D., Canals, M., Colhoun, E. A., Crosta, X., Dickens, W. A., Domack, E., Dowdeswell, J. A., Dunbar, R., Ehrmann, W., Evans, J., Favier, V., Fink, D., Fogwill, C. J., Glasser, N. F., Gohl, K., Golledge, N. R., Goodwin, I., Gore, D. B., Greenwood, S. L., Hall, B. L., Hall, K., Hedding, D. W., Hein, A. S., Hocking, E. P., Jakobsson, M., Johnson, J. S., Jomelli, V., Jones, R. S., Klages, J. P., Kristoffersen, Y., Kuhn, G., Leventer, A., Licht, K., Lilly, K., Lindow, J., Livingstone, S. J., Mass?, G., McGlone, M. S., McKay, R. M., Melles, M., Miura, H., Mulvaney, R., Nel, W., Nitsche, F. O., O'Brien, P. E., Post, A. L., Roberts, S. J., Saunders, K. M., Selkirk, P. M., Simms, A. R., Spiegel, C., Stolldorf, T. D., Sugden, D. E., van der Putten, N., van Ommen, T., Verfaillie, D., Vyverman, W., Wagner, B., White, D. A., Witus, A. E. Zwartz, D. (2014). A community-based geological reconstruction of Antarctic Ice Sheet deglaciation since the Last Glacial Maximum. Quaternary Science Reviews, 100, 1-9.A robust understanding of Antarctic Ice Sheet deglacial history since the Last Glacial Maximum is important in order to constrain ice sheet and glacial-isostatic adjustment models, and to explore the forcing mechanisms responsible for ice sheet retreat. Such understanding can be derived from a broad range of geological and glaciological datasets and recent decades have seen an upsurge in such data gathering around the continent and Sub-Antarctic islands. Here, we report a new synthesis of those datasets, based on an accompanying series of reviews of the geological data, organised by sector. We present a series of timeslice maps for 20 ka, 15 ka, 10 ka and 5 ka, including grounding line position and ice sheet thickness changes, along with a clear assessment of levels of confidence. The reconstruction shows that the Antarctic Ice sheet did not everywhere reach the continental shelf edge at its maximum, that initial retreat was asynchronous, and that the spatial pattern of deglaciation was highly variable, particularly on the inner shelf. The deglacial reconstruction is consistent with a moderate overall excess ice volume and with a relatively small Antarctic contribution to meltwater pulse la. We discuss key areas of uncertainty both around the continent and by time interval, and we highlight potential priorities for future work. The synthesis is intended to be a resource for the modelling and glacial geological community. (C) 2014 The Authors. Published by Elsevier Ltd.publishersversionPeer reviewe

Westoby, M. J., Glasser, N. F., Brasington, J., Hambrey, M. J., Quincey, D. J., Reynolds, J. M. (2014). Modelling outburst floods from moraine-dammed glacial lakes. Earth-Science Reviews, 134, 137-159 Embargoed: 3.4.15In response to climatic change, the size and number of moraine-dammed supraglacial and proglacial lake systems have increased dramatically in recent decades. Given an appropriate trigger, the natural moraine dams that impound these proglacial lakes are breached, producing catastrophic Glacial Lake Outburst Floods (GLOFs). These floods are highly complex phenomena, with flood characteristics controlled, in the first instance, by the style of breach formation. Downstream, GLOFs typically exhibit transient, often non-Newtonian fluid dynamics as a result of high rates of sediment entrainment from the dam structure and channel boundaries. Combined, these characteristics introduce numerous modelling challenges. In this review, the historical, contemporary and emerging approaches available to model the individual stages, or components, of a GLOF event are introduced and discussed. A number of methods exist to model the stages of a GLOF event. Dam-breach models can be categorised as being empirical, analytical or numerical in nature, with each method having significant advantages and shortcomings. Empirical relationships that produce estimates of peak discharge and time to peak are straightforward to implement, but the applicability of these models is often limited by the nature of the case study data from which they are derived. Furthermore, empirical models neglect the inclusion of basic hydraulic principles that describe the mechanics of breach formation. Analytical or parametric models simulate breach development using simplified versions of the physically based equations that describe breach enlargement, whilst complex, physically-based codes represent the state-of-the-art in numerical dam-breach modelling. To date, few of the latter have been applied to investigate the moraine-dam failure problem. Despite significant advances in the physical complexity and availability of higher-order hydrodynamic solvers, the majority of published accounts that have attempted to reconstruct or predict GLOF characteristics have been limited, often by necessity, to the use of relatively simplistic models. This is in part attributable to the unavailability of terrain models of many high-mountain catchments at the fine spatial resolutions required for the effective application of numerically-sophisticated codes, and their proprietary (and often cost-prohibitive) nature. However, advanced models are experiencing increasing use in the glacial hazards literature. In particular, the suitability of emerging mesh-free, particle-based methods for simulating dam-breach and GLOF routing may represent a solution to many of the challenges associated with modelling this complex phenomenon. Sources of uncertainty in the GLOF modelling chain have been identified by various workers. However, to date their significance for the robustnes...

Many Karakoram glaciers periodically undergo surges during which large volumes of ice and debris are rapidly transported downglacier, usually at a rate of 1-2 orders of magnitude greater than during quiescence. Here we identify eight recent surges in the region and map their surface velocities using cross-correlation feature tracking on optical satellite imagery. In total, we present 44 surface velocity data sets, which show that Karakoram surges are generally short-lived, lasting between 3 and 5 years in most cases, and have rapid buildup and relaxation phases, often lasting less than a year. Peak velocities of up to 2 km a À1 are reached during summer months, and the surges tend to diminish during winter months. Otherwise, they do not follow a clearly identifiable pattern. In two of the surges, the peak velocity travels down-ice through time as a wave, which we interpret as a surge front. Three other surges are characterized by high velocities that occur simultaneously across the entire glacier surface, and acceleration and deceleration are close to monotonic. There is also no consistent seasonal control on surge initiation or termination. We suggest that the differing styles of surge can be partly accounted for by individual glacier configurations and that while some characteristics of Karakoram surges are akin to thermally controlled surges elsewhere (e.g., Svalbard), the dominant surge mechanism remains unclear. We thus propose that these surges represent a spectrum of flow instabilities and the processes controlling their evolution may vary on a glacier by glacier basis.

We used Little Ice Age (LIA) trimlines and moraines to assess changes in South American glaciers over the last ~140 years. We determined the extent and length of 640 glaciers during the LIA (~AD1870) and 626 glaciers (the remainder having entirely disappeared) in 1986, 2001 and 2011. The calculated reduction in glacierized area between the LIA and 2011 is 4131 km2 (15.4%), with 660 km2 (14.2%) being lost from the Northern Patagonia Icefield (NPI), 1643km2 (11.4%) from the Southern Patagonia Icefield (SPI) and 306 km2 (14.4%) from Cordillera Darwin. Latitude, size and terminal environment (calving or land-terminating) exert the greatest control on rates of shrinkage. Small, northerly, land-terminating glaciers shrank fastest. Annual rates of area loss increased dramatically after 2001 for mountain glaciers north of 52° S and the large icefields, with the NPI and SPI now shrinking at 9.4km2a-1 (0.23% a-1) and 20.5 km2a-1 (0.15% a-1) respectively. The shrinkage of glaciers between 52° S and 54° S accelerated after 1986, and rates of shrinkage from 1986 to 2011 remained steady. Icefield outlet glaciers, isolated glaciers and ice caps south of 54° S shrank faster from 1986 to 2001 than they did from 2001 to 2011.