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Speckle tracking of ALOS PALSAR fine beam data from 2007-2011 are used to determine the surface motion of major ice masses on Baffin Island and Bylot Island in the southern Canadian Arctic Archipelago. Glacier velocities are low overall, with peaks of ~100 m [a.sup.-1] and means of ~20-60 m [a.sup.-1] common along the main trunk of many outlet glaciers. Peak velocities on Penny and Bylot Island ice caps tend to occur near the mid-sections of their primary outlet glaciers, while the fastest velocities on all other glaciers usually occur near their termini due to relatively large accumulation areas draining through narrow outlets. Estimates of ice thickness at the fronts of tidewater-terminating glaciers are combined with the velocity measurements to determine a regional dynamic discharge rate of between ~17 Mt [a.sup.-1] and ~108 Mt [a.sup.-1], with a mid-point estimate of ~55 Mt [a.sup.-1], revising downward previous approximations. These velocities can be used as inputs for glacier flow models, and provide a baseline dataset against which future changes in ice dynamics can be detected. Le suivi speckle des donnees de faisceau fin ALOS PALSAR, prelevees entre 2007 et 2011, est utilise pour determiner le mouvement de surface des grandes masses de glace sur les iles de Baffin et de Bylot dans le sud de l'archipel arctique canadien. Les vitesses des glaciers sont generalement faibles avec des pointes d'environ 100 m [a.sup.-1] et des moyennes de 20 a 60 m [a.sup.-1] frequentes le long du tronc principal de nombreux glaciers emissaires. Les vitesses de pointe des champs de glace de Penny et de Bylot tendent a etre pres des sections medianes de leurs glaciers emissaires primaires, alors que les vitesses les plus rapides sur tous les autres glaciers sont enregistrees pres du front en raison des aires d'accumulation relativement grandes qui s'ecoulent a travers d'etroites decharges. Des estimations de l'epaisseur de la glace aux fronts de glaciers de maree sont combinees aux mesures de vitesse afin de determiner un taux regional de decharge dynamique entre ~17 Mt [a.sup.-1] et ~108 Mt [a.sup.-1], avec une estimation du taux median de ~55 [a.sup.-1], ce qui revise les estimations anterieures a la baisse. Ces vitesses peuvent etre utilisees comme donnees d'entree pour les modeles d'ecoulement glaciaire et ainsi fournir un ensemble de donnees de reference pour detecter les futurs changements dans la dynamique glaciaire. [Traduit par la Redaction], Introduction The southern Canadian Arctic Archipelago (CAA), consisting of Baffin Island and Bylot Island (Fig. 1), contain ~40 000 [km.sup.2] of glacier ice (Gardner et al. 2012). Recent studies indicate [...]

Glacier velocity measurements are essential to understand ice flow mechanics, monitor natural hazards, and make accurate projections of future sea-level rise. Despite these important applications, the method most commonly used to derive glacier velocity maps, feature tracking, relies on empirical parameter choices that rarely account for glacier physics or uncertainty. Here we test two statistics- and physics-based metrics to assess velocity maps from a range of existing feature-tracking workflows at Kaskawulsh Glacier, Canada. Based on inter-comparisons with ground-truth data, velocity maps with metrics falling within our recommended ranges contain fewer erroneous measurements and more spatially correlated noise than velocity maps with metrics that deviate from those ranges. Thus, these metric ranges are suitable for refining feature-tracking workflows and evaluating the resulting velocity products. We have released an open-source software package for computing and visualizing these metrics, the GLAcier Feature Tracking testkit (GLAFT). [ABSTRACT FROM AUTHOR]

The physical, sedimentological, mineralogical and elemental geochemical properties of sediment cores AMD1803‐02BC and 01PC from the Cape Norton Shaw Inlet were investigated to reconstruct glacial sediment discharges from southeastern Manson Icefield and document the impact of ice–ocean interactions on the sediment dynamics and opening of the North Water Polynya (NOW) in northwestern Baffin Bay since the last deglaciation. Laminated glaciomarine sediments rich in quartz and feldspar are observed prior to 11 cal. ka BP and were probably deposited by hyperpycnal currents triggered by the local retreat of the southern margin of the Innuitian Ice. Detrital proxies suggest that Early Holocene sediment dynamics were mainly influenced by sea ice and iceberg rafting and meltwater discharges related to the deglaciation of eastern Smith (~11 to 10.65 cal. ka BP) and Jones (~10.7 cal. ka BP) sounds. This also provides an upper limit to the timing of formation of the NOW. The high detrital carbonate contents during 8.8 to 6.6 cal. ka BP confirm that enhanced carbonate‐rich sediment export from Nares Strait to northern Baffin Bay occurred during and after the deglaciation of Kennedy Channel (8.8 to 8.2 cal. ka BP). Canadian Shield sediment inputs have dominated since 6.6 cal. ka BP, indicating that sedimentation is mainly influenced by Cape Norton Shaw glacier discharges. The lower level of sedimentation recorded in core 01PC during the Middle to Late Holocene suggests an accelerated landward retreat of the Cape Norton Shaw glaciers in response to warmer marine conditions. During the Neoglacial period, higher sedimentation rates and detrital proxies in the cores suggest increased glacial erosional processes, probably associated with the long‐term declines in boreal summer insolation and glacier growth. Finally, mineralogical and grain‐size data in core 02BC support the idea that increased Arctic atmospheric temperatures have had an important influence on the glacial dynamics during the industrial period. [ABSTRACT FROM AUTHOR]

Substrate properties and hydrological conditions at the base of Haut Glacier d'Arolla, Switzerland, are nonuniform. The thickness and grain size of subglacial sediment vary on length scales less than one ice thickness, whereas hydrological conditions vary seasonally and on length scales of about one ice thickness transverse to ice motion. There is a close relationship between the annually averaged velocity field and this nonuniformity of bed conditions. Basal motion dominates in an area with large water-level variations in boreholes, whereas ice deformation contributes significantly to total movement elsewhere. Localized enhanced basal motion occurs primarily in summer, especially during a July 'spring event,' but this motion is barely discernible in annually averaged surface velocity measurements, because transverse coupling suppresses surface expression of the basal motion discontinuity. These results highlight the need to include representations of bed nonuniformity in models of glacier flow and to consider ice deformation and basal motion as interdependent processes.

Glacier surficial melt rates are commonly modelled using surface energy balance (SEB) models, with outputs applied to extend point-based mass-balance measurements to regional scales, assess water resource availability, examine supraglacial hydrology and to investigate the relationship between surface melt and ice dynamics. We present an improved SEB model that addresses the primary limitations of existing models by: (1) deriving high-resolution (30 m) surface albedo from Landsat 8 imagery, (2) calculating shadows cast onto the glacier surface by high-relief topography to model incident shortwave radiation, (3) developing an algorithm to map debris sufficiently thick to insulate the glacier surface and (4) presenting a formulation of the SEB model coupled to a subsurface heat conduction model. We drive the model with 6 years of in situ meteorological data from Kaskawulsh Glacier and Nàłùdäy (Lowell) Glacier in the St. Elias Mountains, Yukon, Canada, and validate outputs against in situ measurements. Modelled seasonal melt agrees with observations within 9% across a range of elevations on both glaciers in years with high-quality in situ observations. We recommend applying the model to investigate the impacts of surface melt for individual glaciers when sufficient input data are available. [ABSTRACT FROM AUTHOR]

We would like to thank Dr. Ommanney for his insightful discussion regarding our paper (Van Wychen et al. 2015). Dr. Ommanney correctly points out that the glacier identification scheme provided [...]