Explore the vast range of titles available.

Detection, attribution and projection of mass loss from the Greenland Ice Sheet has been a central focus of the glaciological community, with surface meltwater thought to play a key role in feedbacks that could accelerate sea-level rise. While the prospect of runaway sliding has faded, much remains uncertain when it comes to the role of surface runoff and subglacial discharge in Greenland’s future.

One fifth of Earth's volcanoes are covered by snow or ice and many have active geothermal systems that interact with the overlying ice. These glaciovolcanic interactions can melt voids into glaciers, and are subject to controls exerted by ice dynamics and geothermal heat output. Glaciovolcanic voids have been observed to form prior to volcanic eruptions, which raised concerns when such features were discovered within Job Glacier on Qw̓elqw̓elústen (Mount Meager Volcanic Complex), British Columbia, Canada. In this study we model the formation, evolution, and steady-state morphology of glaciovolcanic voids using analytical and numerical models. Analytical steady-state void geometries show cave height limited to one quarter of the ice thickness, while numerical model results suggest the void height h scales with ice thickness H and geothermal heat flux $\\dot {Q}$ as $h/H = a H^b \\dot {Q}^c$, with exponents b = −n/2 and c = 1/2 where n is the creep exponent. Applying this scaling to the glaciovolcanic voids within Job Glacier suggests the potential for total geothermal heat flux in excess of 10 MW. Our results show that relative changes in ice thickness are more influential in glaciovolcanic void formation and evolution than relative changes in geothermal heat flux.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Radar sounding is a powerful geophysical approach for characterizing the subsurface conditions of terrestrial and planetary ice masses at local to global scales. As a result, a wide array of orbital, airborne, ground-based, and in situ instruments, platforms and data analysis approaches for radioglaciology have been developed, applied or proposed. Terrestrially, airborne radar sounding has been used in glaciology to observe ice thickness, basal topography and englacial layers for five decades. More recently, radar sounding data have also been exploited to estimate the extent and configuration of subglacial water, the geometry of subglacial bedforms and the subglacial and englacial thermal states of ice sheets. Planetary radar sounders have observed, or are planned to observe, the subsurfaces and near-surfaces of Mars, Earth's Moon, comets and the icy moons of Jupiter. In this review paper, and the thematic issue of the Annals of Glaciology on ‘Five decades of radioglaciology’ to which it belongs, we present recent advances in the fields of radar systems, missions, signal processing, data analysis, modeling and scientific interpretation. Our review presents progress in these fields since the last radio-glaciological Annals of Glaciology issue of 2014, the context of their history and future prospects.

Long‐term records of the flow patterns and dynamics of surge‐type glaciers improve our understanding of their underlying dynamic processes, and are critical to better resolve their contribution to a changing cryosphere. We adapt a modeling approach designed to emulate glacier surging and fold kinematics using the full Stokes ice‐flow model Elmer/Ice to simulate surging of the Dusty Glacier, located in the St. Elias Mountains, Canada. We combine distributed mass‐balance and numerical ice‐flow models to reconstruct the fold kinematics of the 2001–2003 surge of the Dusty Glacier by comparing model results to Landsat‐7 and Sentinel‐2 imagery, and assess the sensitivity of centennial‐scale modeled glacier structure to different mass balance and sliding parameterizations. This study demonstrates the feasibility of using the approach to reconstruct the surface structure kinematics of a surge‐type glacier in nature, highlighting its potential application to other surge‐type glaciers and regions. Plain Language Summary Glaciers can exhibit irregular flow patterns that complicate predictions of their evolution over the coming decades and centuries. We present a method for reproducing iconic surface structures known as folded medial moraines using glaciological modeling. These moraines are wavy flow patterns found on surge‐type glaciers, highlighted by sediment deposited onto the ice that traces their path. By reconstructing these patterns, the underlying climate and sliding conditions that contributed to the glacier's past flow can be identified. Improving our knowledge of these conditions can help improve glacier flow models. We demonstrate that our methodology successfully reconstructs the flow patterns present on a large surge‐type glacier in Yukon, Canada, and explore its past flow history, and possible future, based on these results. Key Points We use a distributed mass‐balance model and Elmer/Ice to reconstruct the 2001–2003 surge kinematics of the Dusty Glacier, Yukon, Canada We explore the centennial‐scale sensitivity of glacier surface fold geometry to mass balance and sliding parameterizations This study is a proof‐of‐concept for further model reconstructions of the past dynamics of surge‐type glaciers

We investigate unusual discontinuous glacier motion on Thompson Glacier, Umingmat Nunaat, Arctic Canada, using synthetic aperture radar (SAR) images and ice-flow modeling. A novel intensity-rescaling scheme is developed to reduce errors in high-resolution speckle tracking, resulting in a ~25% improvement in accuracy. Interferometric SAR (InSAR) and speckle tracking using high resolution RADARSAT-2 data indicate velocity discontinuities of up to 1 cm d−1 across deep and longitudinally extensive supraglacial channels on Thompson Glacier. We use a cross-sectional finite-element ice-flow model to determine the conditions under which velocity discontinuities of the observed magnitude and signature are possible. The modeling suggests that discontinuous motion across (long and straight) supraglacial channels can occur without ice fracture and under a wide variety of glacier thermal structures, including in fully temperate glaciers. Despite the wide range of conditions conducive to discontinuous motion, the form we observe requires that the associated channels be deep, longitudinally extensive and located in regions of lateral shearing. We speculate that these combined conditions are rare except on polythermal glaciers, where drainage features such as moulins are comparatively scarce and lower deformation rates allow channels to incise consistently and persist over many years.

Runoff contributions from glacierized catchments are changing in response to accelerating mass loss. We reconstruct the 1980–2022 mass balance, runoff and water budget of the ∼70% glacierized Kaskawulsh River headwaters in Yukon, Canada, using an enhanced temperature-index model driven by downscaled and bias-corrected reanalysis data. Debris is treated using melt-scaling factors based on site-specific measurements of the critical debris thickness. Accumulation is estimated from downscaled precipitation bias corrected based on in situ measurements. Model tuning incorporates observations of the 2007–18 geodetic mass balance and seasonal snowline positions on the Kaskawulsh Glacier. We assess model sensitivity to the representation of supraglacial debris and accumulation, including treatments of these processes that can be applied in the absence of in situ data. Different representations of debris produce <1% variation in the catchment-wide runoff and water budget. In contrast, accumulation estimates that omit in situ data produce 33–40% variations in modelled runoff relative to those that use these data. This work identifies site-specific measurements of accumulation as critical to accurate estimates of mass balance and runoff for the Kaskawulsh Glacier, in contrast to site-specific characterization of the effects of debris which influence estimated thinning rates at the glacier terminus but have little impact on the glacier-wide runoff.

Theory and observation show that glacier-flow regimes characterized by high basal slip enhance the projection of topographic detail to the surface, motivating this investigation into the efficacy of using glacier surges to improve bed estimation. Here we adapt a Bayesian inversion scheme and apply it to real and synthetic data as a proof of concept. Synthetic tests show a reduction in mean RMSE between true and inferred beds by more than half, and an increase in the mean correlation coefficient of ~0.5, when data from slip- versus deformation-dominated regimes are used. Multi-epoch inversions, which partition slip- and deformation-dominated regimes, are shown to outperform inversions that average over these flow regimes thereby squandering information. Tests with real data from a surging glacier in Yukon, Canada, corroborate these results, while highlighting the challenges of limited or inconsistent data. With the growing torrent of satellite-based observations, fast-flow events such as glacier surges offer potential to improve bed estimation for some of the world's most dynamic glaciers.

Atmospheric warming is causing glaciers worldwide to retreat and disappear, with repercussions for nearby communities. Effects of glacier retreat have been especially consequential for mountain resorts such as Whistler Blackcomb, Canada, where nearly 60 years of summer glacier use by skiing has been terminated due to the ongoing demise of Whistler, Horstman and Blackcomb Glaciers. Over the past five decades, these three glaciers decreased in area by 95%, 75% and 60%, respectively. Using a degree-day model with downscaled CMIP6 data, we project that Whistler Glacier will disappear within the next decade, whereas Horstman and Blackcomb Glaciers will vanish in the next $20\\pm10$ years and $50\\pm20$ years, respectively. The large uncertainty in disappearance dates depends primarily on the applied ice-thickness model. Our work demonstrates that ski resorts that rely on glaciers will need to balance current ice-preservation strategies with adaptation in light of ongoing future climate change.

Recent observations of dynamic water systems beneath the Greenland and Antarctic ice sheets have sparked renewed interest in modelling subglacial drainage. The foundations of today's models were laid decades ago, inspired by measurements from mountain glaciers, discovery of the modern ice streams and the study of landscapes evacuated by former ice sheets. Models have progressed from strict adherence to the principles of groundwater flow, to the incorporation of flow 'elements' specific to the subglacial environment, to sophisticated two-dimensional representations of interacting distributed and channelized drainage. Although presently in a state of rapid development, subglacial drainage models, when coupled to models of ice flow, are now able to reproduce many of the canonical phenomena that characterize this coupled system. Model calibration remains generally out of reach, whereas widespread application of these models to large problems and real geometries awaits the next level of development.