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Supraglacial, moraine-dammed and ice-dammed lakes represent a potential glacial lake outburst flood (GLOF) threat to downstream communities in many mountain regions. This has motivated the development of empirical relationships to predict lake volume given a measurement of lake surface area obtained from satellite imagery. Such relationships are based on the notion that lake depth, area and volume scale predictably. We critically evaluate the performance of these existing empirical relationships by examining a global database of measured glacial lake depths, areas and volumes. Results show that lake area and depth are not always well correlated (r² = 0.38), and that although lake volume and area are well correlated (r² = 0.91), there are distinct outliers in the dataset. These outliers represent situations where it may not be appropriate to apply existing empirical relationships to predict lake volume, and include growing supraglacial lakes, glaciers that recede into basins with complex overdeepened morphologies or that have been deepened by intense erosion, and lakes formed where glaciers advance across and block a main trunk valley. We use the compiled dataset to develop a conceptual model of how the volumes of supraglacial ponds and lakes, moraine-dammed lakes and ice-dammed lakes should be expected to evolve with increasing area. Although a large amount of bathymetric data exist for morainedammed and ice-dammed lakes, we suggest that further measurements of growing supraglacial ponds and lakes are needed to better understand their development. [ABSTRACT FROM AUTHOR]

The return periods of Karakoram glacier surges are poorly quantified. Here, we present evidence of an historic surge of the Khurdopin Glacier that began in the mid- 1970s and peaked in 1979. Measured surface displacements reached > 5 km a-1, two orders of magnitude faster than during quiescence. The Khurdopin Glacier next surged in the late 1990s, equating to a return period of 20 years. Surge evolution in the two events shows remarkable similarity suggesting a common trigger. Surge activity in the Karakoram needs to be better understood if accurate mass balance assessments of Hindu-Kush-Karakoram-Himalaya glaciers are to be made. [ABSTRACT FROM AUTHOR]

The article discusses the difference of the dynamic behaviour of Karakoram glaciers from those in the central and eastern Himalayas because of the regional variations in precipitation and temperature tendencies. It discusses the data and methods used for velocity measurements covering the period 1993-2008 for the Baltoro Glacier, Pakistan, one of the longest glaciers in the Karakoram. The results and the conclusion that help to explain the observed dynamic variations of behaviour from glaciers in the Himalayas are also discussed.

The article presents a study which quantifies the glacier velocities of Everest region in Nepal and Tibet, China between 1992 and 2002 . The study used a satellite radar interferometry and feature tracking techniques in order to measure the degree of stagnation in 20 glaciers throughout the Everest region. It also examines the connection between local catchment topography and ice dynamics of each glacier. Results revealed that the Kangshung Glacier is the only glacier that can be considered as dynamic across the entire region. While twelve glaciers have slow velocities but are characterized as long, stagnant tongues that could have a widespread recession and in situ decay.

Understanding the changing mass balance and surface dynamics of the Earth's major ice sheets in Greenland and Antarctica is of fundamental importance for accurate predictions of future sea-level rise. In this review, the remote sensing data sources available to ice-sheet studies are considered and the range of information that can be gained from remote sensing is examined. The review demonstrates that the integration of a range of remote sensing data sets can provide information on ice-sheet dynamics and volume changes, melt patterns and formation and drainage of supra- and subglacial lakes. Such data are highly complementary to field investigations by providing a regional-scale, synoptic perspective. The review concludes that emerging remote sensing techniques such as SAR interferometry, feature tracking, scatterometry, altimetry and gravimetry provide vital information without which an understanding of ice sheets would be far less advanced. It also concludes that there remain several key challenges for remote sensing, in particular relating to the observation of rapid dynamical changes that are characteristic of contemporary ice-sheet response to continued climatic warming. [ABSTRACT FROM AUTHOR]

Remote sensing studies have shown that glaciers and their proximal environments exhibit unique temporal, spatial and spectral characteristics that can be analysed to better quantify glacial hazard potential. In this review, the optical remote sensing data sources available to glacial hazard assessors are considered and the range of information on glacial environments that can be derived is analysed. The review shows that the integration of a variety of data sources can provide geoscientists with information regarding glacial lakes and lake development, glacier dynamics, avalanche sources and ice-marginal fluctuations. Such data can be used to complement and, in many cases, improve field-based glacial hazard assessments. The review concludes that aerial photography still remains the main source of data for measuring a number of glacier characteristics, but that fine to moderate spatial resolution satellite sensors (e.g., ASTER, SPOT 5 HRVIR, Landsat ETM+) also provide useful information that can be used to support the assessment of hazards in high-mountain glacierized terrain. [ABSTRACT FROM AUTHOR]

The presence of supraglacial debris on glaciers in the Himalaya-Karakoram affects the ablation rate of these glaciers and their response to climatic change. To understand how supraglacial debris distribution and associated surface features vary spatially and temporally, geomorphological mapping was undertaken on Baltoro Glacier, Karakoram, for three time-separated images between 2001–2012. Debris is supplied to the glacier system through frequent but small landslides at the glacier margin that form lateral and medial moraines and less frequent but higher volume rockfall events which are more lobate and often discontinuous in form. Debris on the glacier surface is identified as a series of distinct lithological units which merge downglacier of the convergence area between the Godwin-Austen and Baltoro South tributary glaciers. Debris distribution varies as a result of complex interaction between tributary glaciers and the main glacier tongue, complicated further by surge events on some tributary glaciers. Glacier flow dynamics mainly controls the evolution of a supraglacial debris layer. Identifying such spatial variability in debris rock type and temporal variability in debris distribution has implications for glacier ablation rate, affecting glacier surface energy balance. Accordingly, spatial and temporal variation in supraglacial debris should be considered when determining mass balance for these glaciers through time. [ABSTRACT FROM PUBLISHER]

Accurate, precise and rapid acquisition of topographic data is fundamental to many sub-disciplines of physical geography. Technological developments over the past few decades have made fully distributed data sets of centimetric resolution and accuracy commonplace, yet the emergence of Structure from Motion (SfM) with Multi-View Stereo (MVS) in recent years has revolutionised three-dimensional topographic surveys in physical geography by democratising data collection and processing. SfM-MVS originates from the fields of computer vision and photogrammetry, requires minimal expensive equipment or specialist expertise and, under certain conditions, can produce point clouds of comparable quality to existing survey methods (e.g. Terrestrial Laser Scanning). Consequently, applications of SfM-MVS in physical geography have multiplied rapidly. There are many practical options available to physical geographers when planning a SfM-MVS survey (e.g. platforms, cameras, software), yet, many SfM-MVS end-users are uncertain as to the errors associated with each choice and, perhaps most fundamentally, the processes actually taking place as part of the SfM-MVS workflow. This paper details the typical workflow applied by SfM-MVS software packages, reviews practical details of implementing SfM-MVS, combines existing validation studies to assess practically achievable data quality and reviews the range of applications of SfM-MVS in physical geography. The flexibility of the SfM-MVS approach complicates attempts to validate SfM-MVS robustly as each individual validation study will use a different approach (e.g. platform, camera, georeferencing method, etc.). We highlight the need for greater transparency in SfM-MVS processing and enhanced ability to adjust parameters that determine survey quality. Looking forwards, future prospects of SfM-MVS in physical geography are identified through discussion of more recent developments in the fields of image analysis and computer vision. [ABSTRACT FROM AUTHOR]

Ice‐contact proglacial lakes are generally absent from numerical model simulations of glacier evolution, and their effects on ice dynamics and on rates of deglaciation remain poorly quantified. Using the BISICLES ice flow model, we analyzed the effects of an ice‐contact lake on the Pukaki Glacier, New Zealand, during recession from the Last Glacial Maximum. The ice‐contact lake produced a maximum effect on grounding line recession >4 times further and on ice velocities up to 8 times faster, compared to simulations of a land‐terminating glacier forced by the same climate. The lake contributed up to 82% of cumulative grounding line recession and 87% of ice velocity during the first 300 years of the simulations, but those values decreased to just 6% and 37%, respectively, after 5,000 years. Numerical models that ignore lake interactions will, therefore, misrepresent the rate of recession especially during the transition of a land‐terminating to a lake‐terminating environment. Plain Language Summary: Lakes form at the margins of glaciers as meltwater accumulates against hillsides and behind ridges of glacier debris. Lakes at a glacier terminus are known to affect its behavior. However, glaciers terminating into such lakes are usually absent from computer simulations, and the effects of these lakes on the rates of deglaciation and on glacier behavior are poorly quantified. In this study, we tested the effect of a lake on glacier recession under two different scenarios; a land‐terminating versus a lake‐terminating glacier. We used an ice flow model called BISICLES and applied it to what was once the Pukaki Glacier in New Zealand during the end of the last ice age. We found that the presence of a lake caused the glacier to recede more than 4 times further and it accelerated ice flow by up to 8 times when compared to the same glacier that terminated on land under the same climate. Our simulated lake processes predominantly influenced the glacier over decades to centuries rather than over millennia. We suggest, therefore, that simulations of glacier evolution ignoring glacial lakes will likely misrepresent the timing and rate of recession, especially during the transition from a land‐terminating to a lake‐terminating environment. Key Points: A reverse bedslope, combined with deep water and frontal ablation, produces a terminus geometry with a wider and steeper ice surface slopeA lake‐terminating glacier receded >4 times further and flowed up to 8 times faster than a land‐terminating glacier forced by the same climateOur simulated lake processes predominantly influenced the glacier over decades to centuries rather than over millennia [ABSTRACT FROM AUTHOR]