This paper records the history of how and why the Journal of Glaciology was started and how it has grown into the Journal we know today.

Women’s history in glaciology extends as far back in time as the discipline itself, although their contributions to the scientific discourse have for all of that history been constrained by the sociopolitical contexts of the times. The first Journal of Glaciology paper authored by a woman appeared in 1948, within a year of the founding of the Journal, but it was not until the 1980s that women produced more than a few percent of Journal and Annals of Glaciology papers. Here international perspectives on women’s participation in the sciences are presented in order to establish an economic and sociopolitical context for stories of women ‘pioneers’ in glaciology and a frame in which to discuss women’s persistent under-representation relative to men. We find that the experiences of individual glaciologists mirror women’s experiences in higher education and the sciences as a whole. The existence of both positive and negative trends in women’s participation in the sciences suggests caution in the interpretation of recent positive trends for women’s participation in glaciology.

This paper reviews the seminal contributions (and tussles) of Weertman and Lliboutry to the theory of glacier sliding in the 1950s and 1960s, and summarizes later developments up to the present day.

‘Extrusion flow’ describes any velocity field where maximum horizontal velocity occurs below the surface. By 1914, viscous flow and basal sliding over rough beds were accepted concepts. Between the world wars, there was little communication between naturalists describing complicated ice sheets, and physicists studying fundamental processes controlling flow. Max Demorest brought concepts from mechanics into glaciology and glacial geology; however, his extrusion flow theory, to explain how ice flowed out of central Greenland, overlooked force imbalance. Rudolf Streiff-Becker found an apparent large imbalance between ice flux discharged through a gate and net accumulation in the upstream catchment at Claridenfirn, Switzerland. Because he underestimated uncertainty in ice depth, he had to propose a strong undercurrent (extrusion flow) to evacuate the excess mass. Reassessment of his assumptions shows that extrusion was actually unnecessary. However, confluence of two lines of evidence for extrusion flow added stature to the concept. In 1952, John Nye showed that free extrusion flow was impossible due to force imbalance. Two forms of extrusion flow survive: capped extrusion flow is possible on local scales where longitudinal stress gradients allow upper ice to move slowly, and rigid- body rotational flow can allow deeper ice to move faster without strain.

For 40 years Anonymous (J. Glaciol., 8(52), 1969) has been the effective standard of glacier mass-balance terminology. It grew out of a concern for clarity in the communication of information, and has guided thinking about mass balance in many ways. Certain ambiguities and gaps in its conceptualization have become more evident with the passage of time, and some have been aggravated by ad hoc extensions of and deviations from the standard. Methodological progress means that a review of the terminology of Anonymous (1969) is now timely, and a forthcoming glossary to be published by the International Association of Cryospheric Sciences addresses this need. There are good reasons for being concerned about clear terminology, but consistent usage by the members of a large community cannot be secured other than by consensus.

The study of jökulhlaups has advanced from describing them qualitatively to measuring systematically on site their discharge curves and source geometry, as well as investigating conditions when particular floods were initiated. In the early days of this science, hypotheses were formulated which attempted to explain the processes responsible for unstable flood growth. The general theory of time-dependent turbulent water flow through intraglacial conduits marked a breakthrough in understanding jökulhlaup hydraulics and has since remained a classical foundation for jökulhlaup studies. This theory described flood evolution in terms of water input into the upper end of a tunnel leading from a reservoir, taking account of sensible stored lake heat and geometry. Such a tunnel expands by positive feedback, since its ice walls melt through frictional heat produced by the flowing water. While this model successfully described jökulhlaups in which the discharge hydrograph increases more or less exponentially over time, other floods were observed which are in stark contrast. In them, pressurized floodwater propagates in a turbulent subglacial water sheet which opens and expands a system of conduits, with an extremely rapid linear rise in discharge. The rushing water enlarges its subglacial pathway not only by melting the ice around it but also by lifting, deforming and fracturing it. Subsequent drainage is nourished by two different sources, with conduit growth being controlled not only by water input at the upper end of the flood path but also by further water joining in, all the way to the edge of the glacier. Moreover, the trigger for releasing meltwater from glacial lakes has been seen to be either of two conduit opening mechanisms, which also determine whether a turbulent subglacial water sheet will result or not. On the one hand, drainage may begin by expanding already existing conduits, in which case the pressure remains lower than that of the ice overburden at the dam and the conduits grow slowly. On the other hand, lake levels may rise until flotation of the ice dam, abruptly opening a sufficient gap for water to propagate as a sheet flow. In order to explain which of these two initiation mechanisms will act, further studies are required into the structure of hydrological drainage systems under ice dams and into their linkage with these two mechanisms. Although current theoretical models of jökulhlaups drainage have managed to reproduce the observed discharge patterns, inconsistencies with the observed behaviour of subglacial drainage systems along the flood path demand further exploration of the actual hydraulic and glaciodynamic processes of jökulhlaups.

Subglacial bedforms are a range of landforms (10-105m long) shaped mostly in glacial sediments and are abundant on ice-sheet beds. Numerous explanations for their generation, especially of drumlins, have been proposed. Rather than viewing them as resulting from erosion or deposition directly by ice, Smalley and Unwin (1968) proposed that both might occur simultaneously if, beneath the glacier, a layer of lubricating sediment existed and ‘flowed’, conducting geomorphic work (erosion, deposition, shaping) of its own. This idea appears to have steered the field, leading perhaps to final resolution of the centuries-old problem of drumlin genesis. Here I trace how the idea evolved, leading to the conclusion that subglacial bedforms are emergent phenomena arising from self-organization in the coupled flow of ice, sediment and water. The ubiquity and patterning of bedforms appears to be well explained by a naturally arising flow instability in the subglacial system, and which has been demonstrated by analytical and numerical modelling. A problem for the instability theory is an apparent mismatch between predicted and observed sedimentological properties of bedforms. A distinction is made between emergent drumlins, drumlin clones and obstacle drumlins which helps explain some apparent contradictions, and a conceptual framework is erected that might form a basis for confronting the theory with the wealth of observational evidence that exists.

Spaceborne interferometric synthetic aperture radar (InSAR) techniques for measuring ice flow velocity and topography have developed rapidly over the last decade and a half, revolutionizing the study of ice dynamics. Spaceborne interferometry has contributed to major progress in many areas of glaciological study by: providing the first comprehensive measurements of ice-stream flow velocity over the major outlets of Greenland and Antarctica; revealing that ice-stream and outlet-glacier flow can change rapidly (months to years); improving understanding of several ice-sheet and ice-shelf processes; providing velocity for flux-gate based mass-balance assessment; mapping flow of mountain glaciers; and capturing the geomorphic traces of past ice flow. We review the basic technique development, the measurement characteristics, and the extensive set of results yielded by these measurements.

An overview is given of the relatively short history, important issues and primary challenges of research on permafrost in cold mountain regions. The systematic application of diverse approaches and technologies contributes to a rapidly growing knowledge base about the existence, characteristics and evolution in time of perennially frozen ground at high altitudes and on steep slopes. These approaches and technologies include (1) drilling, borehole measurement, geophysical sounding, photogrammetry, laser altimetry, GPS/SAR surveying, and miniature temperature data logging in remote areas that are often difficult to access, (2) laboratory investigations (e.g. rheology and stability of ice-rock mixtures), (3) analyses of digital terrain information, (4) numerical simulations (e.g. subsurface thermal conditions under complex topography) and (5) spatial models (e.g. distribution of permafrost where surface and microclimatic conditions are highly variable spatially). A sound knowledge base and improved understanding of governing processes are urgently needed to deal effectively with the consequences of climate change on the evolution of mountain landscapes and, especially, of steep mountain slope hazards as the stabilizing permafrost warms and degrades. Interactions between glaciers and permafrost in cold mountain regions have so far received comparatively little attention and need more systematic investigation.

Major advances in understanding the plasticity of ice have been made during the past 60 years with the development of studies of the flow of glaciers and, recently, with the analysis of deep ice cores in Antarctica and Greenland. Recent experimental investigations clearly show that the plastic deformation of the ice single crystal and polycrystal is produced by intermittent dislocation bursts triggered by long-range interaction of dislocations. Such dislocation avalanches are associated with the formation of dislocation patterns in the form of slip lines and slip bands, which exhibit long-range correlations and scale invariance. Long-range dislocation interactions appear to play an essential role in primary creep of polycrystals and dynamic recrystallization. The large plastic anisotropy of the ice crystal is at the origin of large strain and stress heterogeneities within grains. The use of full- field approaches is now a compulsory proceeding to model the intracrystalline heterogeneities that develop in polycrystals. Ice is now highly regarded among the materials science community. It is considered a model material for understanding deformation processes of crystalline materials and polycrystal modeling.

The association between basal hydrology and glacier sliding has become nearly synonymous with the early work of Almut Iken and colleagues. Their research published in the Journal of Glaciology from 1981 to 1986 made an indelible impact on the study of glacier hydromechanics by documenting strong correlations between basal water pressure and short-term ice-flow variations. With a passion for elucidating the physics of glacier-bed processes, Iken herself made fundamental contributions to our theoretical and empirical understanding of the sliding process. From the theoretical bound on basal shear stress, to the inferences drawn from detailed horizontal and vertical velocity measurements, the work of Iken and colleagues continues to inform the interpretation of data from alpine glaciers and has found increasing relevance to observations from the ice sheets.

The theory of channelized water flow through glaciers, most commonly associated with the names of Hans Röthlisberger and Ron Shreve and their 1972 papers in the Journal of Glaciology, was developed at a time when interest in glacier-bed processes was expanding, and the possible relationship between glacier sliding and water at the bed was becoming of keen interest. The R-channel theory provided for the first time a physically based conceptual model of water flow through glaciers. The theory also marks the emergence of glacier hydrology as a glaciological discipline with goals and methods distinct from those of surface-water hydrology.

Observations of glacier flow and explanations of its origin started as early as the 18th century. Several mechanisms were suggested before gravity-driven viscous flow became the accepted theory of glacier flow in the 1950s, the early years of the Journal of Glaciology. Since the viscosity of ice is strongly temperature-dependent, the topic of glacier and ice-sheet dynamics became essentially a fluid-dynamical problem. The availability of growing computing power turned the field of glacier mechanics and thermodynamics into a field of numerical modelling with increasing sophistication.

Ice cores are remarkably faithful recorders of past climate, providing multiply duplicated reconstructions with small and quantifiable uncertainties. Ice core reconstructions in general do not rely on assumed quantitative time-invariance of empirical calibrations between climate and sedimentary characteristics, but instead rely on assuming little more than the constancy of physical law over time. The history of some of the discoveries that allow these ice-core climatic reconstructions is instructive for students, citizens and policymakers. Much important ice-core science was published in the Journal of Glaciology and the Annals of Glaciology, with scientific impacts much larger than indicated by mere citation counts.

The field observations of G.S. Boulton stimulated widespread interest in deformable beds. Shear resistance of till in its critical state is insensitive to strain rate and increases linearly with effective pressure. During unsteady deformation, pseudo-viscous shear resistance can be caused by dilation of consolidated tills and resultant pore-pressure decline. This effect is probably uncommon, however, because susceptible tills of low hydraulic diffusivity are also those least likely to consolidate significantly during effective-pressure transients. Stick-slip motion at Whillans Ice Stream, Antarctica, indicates that its basal till must weaken during rapid slip and strengthen during longer periods of slower slip. Recurrence intervals for rapid-slip episodes there (6-18hours) indicate that till-strength variations, if driven by changes in pore pressure either related or unrelated to basal freezing, are focused in the uppermost several centimeters of the bed. Ploughing of grains at the bed surface and associated excess pore pressures in adjacent till can account for rate-weakening during rapid slip, with pore-pressure decay causing strengthening between slip episodes. By promoting shallow, sluggish subglacial water flow and low effective pressure, soft beds may help sustain themselves by slowing their own transport. Soft-bed shear resistance, kinematics and continuity are problems rooted in subglacial hydrology.

Over the period of modern satellite observations, Arctic sea-ice extent at the end of the melt season (September) has declined at a rate of >11% per decade, and there is evidence that the rate of decline has accelerated during the last decade. While climate models project further decreases in sea- ice mass and extent through the 21st century, the model ensemble mean trend over the period of instrumental records is smaller than observed. Possible reasons for the apparent discrepancy between observations and model simulations include observational uncertainties, vigorous unforced climate variability in the high latitudes, and limitations and shortcomings of the models stemming in particular from gaps in understanding physical process. The economic significance of a seasonally sea-ice-free future Arctic, the increased connectivity of a warmer Arctic with changes in global climate, and large uncertainties in magnitude and timing of these impacts make the problem of rapid sea-ice loss in the Arctic a grand challenge of climate science. Meaningful prediction/projection of the Arctic sea-ice conditions for the coming decades and beyond requires determining priorities for observations and model development, evaluation of the ability of climate models to reproduce the observed sea-ice behavior as a part of the broader climate system, improved attribution of the causes of Arctic sea-ice change, and improved understanding of the predictability of sea-ice conditions on seasonal through centennial timescales in the wider context of the polar climate predictability.

The deformation of the ground surface that is produced by frost heave has motivated almost a century of concerted laboratory, field and theoretical studies. Well before the development of equipment capable of resolving the microscopic films that support liquid transport towards growing ice lenses, early investigators predicted their occurrence and noted their importance. Idealized experiments continue to prompt theoretical advances that have been combined to develop predictive models for the macroscopic frost-heave characteristics that are seen in the field. This contribution highlights steps on the road to our current understanding of the physical interactions that control how ice forms in unconsolidated porous media.

Observations of sea-ice thickness and kinematics are essential for understanding changes in sea-ice mass balance, interactions between the ice cover and the ocean and atmosphere and for improving projections of sea-ice response in a warming climate. These parameters are not directly observable with current sensor technology, but are derived from satellite altimetry and imagery. While there is progress in the retrievals of Arctic sea-ice thickness from satellite altimetry, approaches to address Southern Ocean ice thickness require additional attention. On the other hand, procedures to derive sea-ice motion from satellite imagery are more mature and better understood and have been employed to produce useful results for more than a decade. Adequate sampling of sub-daily ice motion, however, remains a challenge. Generally, satellite instruments provide large-scale coverage but the frequency of temporal sampling is limited by orbit characteristics. In this review, I focus on the approaches, uncertainties, sampling limitations and validation issues associated with the estimation of sea-ice thickness and motion. I provide a summary of current and anticipated capabilities for monitoring sea-ice thickness and kinematics from space. The prospects for continuing these measurements into the next decade, from a satellite remote-sensing perspective, are discussed.

Remote sensing offers local, regional and global observations of seasonal snow, providing key information on snowpack processes. This brief review highlights advancements in instrumentation and analysis techniques that have been developed over the past decade. Areas of advancement include improved algorithms for mapping snow-cover extent, snow albedo, snow grain size, snow water equivalent, melt detection and snow depth, as well as new uses of instruments such as multiangular spectroradiometers, scatterometry and lidar. Limitations and synergies of the instruments and techniques are discussed, and remaining challenges such as multisensor mapping, scaling issues, vegetation correction and data assimilation are identified.

Satellite remote sensing has come to dominate the measurement of glacier and ice-sheet change. Three independent methods now exist for assessing ice-sheet mass balance and we focus on progress in two: satellite altimetry (ICESat) and gravimetry (GRACE). With improved spatial and temporal sampling, and synergy with ice flow measurements, both the mechanisms and causes changing mass balance can be investigated. We present examples of mass losses due to widespread, intensifying glacier dynamic thinning in northwest Greenland, but local ablation rates in the northeast that are unchanged for decades. Advances in GRACE processing reveal Greenland net ice-sheet mass loss continuing into 2010, at 195 ± 30 Gta-1. A similarly negative trend in the Gulf of Alaska has significant spatial and temporal variation, that highlights the importance of intense summer melting here. Strong summer melt on the Antarctic Peninsula also precipitated recent ice-shelf collapse and prompted rapid dynamic thinning of tributary glaciers at up to 70 m a-1. Thinning continued for years to decades after collapse and propagated far inland. While understanding of the physical mechanisms of change continues to improve, estimates of future behaviour, and in particular the near-future glacial sea-level contribution, still rely on projections from such observations. We introduce the suite of new sensors that will monitor the ice sheets into the future.