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Glacial acceleration is a main source of uncertainty in sea-level-change assessment. Measurement of ice-surface heights with a spatial and temporal resolution that not only allows elevation-change calculation, but also captures ice-surface morphology and its changes is required to aid in investigations of the geophysical processes associated with glacial acceleration. The Advanced Topographic Laser Altimeter System aboard NASA’s future ICESat-2 Mission (launch 2017) will implement multibeam micropulse photon-counting lidar altimetry aimed at measuring ice-surface heights at 0.7-m along-track spacing. The instrument is designed to resolve spatial and temporal variability of rapidly changing glaciers and ice sheets and the Arctic sea ice. The new technology requires the development of a new mathematical algorithm for the retrieval of height information. We introduce the density-dimension algorithm (DDA) that utilizes the radial basis function to calculate a weighted density as a form of data aggregation in the photon cloud and considers density an additional dimension as an aid in autoadaptive threshold determination. The autoadaptive capability of the algorithm is necessary to separate returns from noise and signal photons under changing environmental conditions. The algorithm is evaluated using data collected with an ICESat-2 simulator instrument, the Slope Imaging Multi-polarization Photon-counting Lidar, over the heavily crevassed Giesecke Brær in Northwestern Greenland in summer 2015. Results demonstrate that ICESat-2 may be expected to provide ice-surface height measurements over crevassed glaciers and other complex ice surfaces. The DDA is generally applicable for the analysis of airborne and spaceborne micropulse photon-counting| lidar data over complex and simple surfaces. [ABSTRACT FROM PUBLISHER]

The dynamics of a surge is manifested in the crevasse patterns: literally, deformation state frozen in ice. This basic observation is utilized as the concept of an automated approach to map and analyze deformation stages and progression of surge kinematics. The classification method allows imagery to be used as geophysical data and is applied to aerial observations (photographic and video imagery, GPS data) collected in September 2011 during the surge of the Bering Glacier-Bagley Ice Valley system, Alaska, USA. As the third dimension that complements two-dimensional imagery, icesurface elevation is observed using aerial laser altimetry. The classification method builds on concepts from signal processing, geostatistical data analysis and neural networks. Steps include calculation of generalized directional vario functions from image data and composition into feature vectors. The vario function operates as an information filter that retains spatial characteristics at an intermediate scale that captures crevasse spacing, anisotropy and other generalized roughness properties. Association of feature vectors to crevasse classes and hence deformation types employs a connectionist algorithm. In general, the connectionist-geostatistical classification allows the mapping of kinematic changes in crevassed glaciers. [ABSTRACT FROM AUTHOR]

Crevasse initiation is linked to strain rates that range over three orders of magnitude (0.001 and 0.163 a-1) as a result of the temperature-dependent nonlinear rheological properties of ice and from water and debris inclusions. Here we discuss a small cold glacier that contains buried crevasses at and near an ice divide. Surface-conformable stratigraphy, the glacier's small size, and cold temperatures argue for limited rheological variability at this site. Surface ice-flow velocities of (1.2-15.5) ± 0.472 m a-1 imply classic saddle flow surrounding the ice divide. Numerical models that incorporate field-observed boundary conditions suggest extensional strain rates of 0.003-0.015 a-1, which fall within the published estimates required for crevasse initiation. The occurrence of one crevasse beginning at 50m depth that appears to penetrate close to the bed suggests that it formed at depth. Field data and numerical models indicate that a higher interior stress at this crevasse location may be associated with steep convex bed topography; however, the dynamics that caused its formation are not entirely clear. [ABSTRACT FROM AUTHOR]

The article discusses a study which investigated the effects of several factors, such as debris thickness, diurnally cyclic radiation and rainfall, on melt rates beneath rock-avalanche debris and sand. A background of studies on the role of debris cover in modifying glacier behaviour is presented. Information is also presented on the sources of supraglacial ablation-zone debris. The article also examines diurnal radiation cycles and debris properties and critical thickness and diurnal cyclicity.

The article discusses a study which explores the englacial drainage systems that are formed by hydrologically driven crevasse propagation. Surface-to-bed drainage systems were developed at the ice sheet and at the High Arctic glaciers in Greenland. Researchers examined and surveyed englacial drainage systems what were formed by hydrofracturing in the glaciers in Svalbard, Nepal and Alaska. They used speleological techniques and found vertical shafts that were followed by cold ice and temperate basal ice to subglacial conduit. The study found that englacial drainages by hydrofracturing in glaciological periods is a common process.

Accelerated glacial recession and downwasting in Pacific North America is exposing land surfaces and features buried by glacial advances that, in many locations, predate the recent Little Ice Age (LIA). Dendrochronologic analyses of increment core samples from living trees (Abies lasiocarpa, Tsuga mertensiana) and samples of subfossil wood collected in the Todd Icefield area, Boundary Ranges, British Columbia Coast Mountains, provide the basis for a dendroglaciological and radiocarbon-based reconstruction of late Holocene glacier activity. Five intervals of glacier expansion were recorded by trees killed or buried by advancing glaciers: (1) an advance prior to ~3000 14C years BP; (2) an advance at ~3000 14C years BP that coincides with the regional Tiedemann advance; (3) an unattributed advance at 2300 14C years BP; (4) a two-phase advance at ~1700 and ~1450 14C years BP that corresponds with the regional First Millennium advance; (5) an advance with three phases of expansion that began prior to ~750 14C BP and is consistent with the regional early LIA interval and a two-phase interval of late LIA expansion culminating after ~240 and 100 years BP. This chronology of late Holocene glaciation matches that emerging from similar investigations in the coastal cordillera of Pacific North America and provides additional support for the regional significance of both the Tiedemann and the First Millennium advances. [ABSTRACT FROM AUTHOR]

The article reports on the history of glaciers with emphasis on its significance towards global climatology specifically on global warming. The author argues that glaciers play a significant role in climate science as well as on the advent of temperature increases in all parts of the world. Glaciers have been regarded as a sublime scenery, a mere recreation site, a place to conquer and explore among others without due regard to its inherent role in ecology. The author further argues that global warming and glaciers can be a good platform for discussions in environmental as well as climate science.

The article discusses the use of TerraSAR-X to calculate the ice stream of Recovery Glacier system in Antarctica. It notes that TerraSAR-X can be used to investigate fine structures on ice and snow surfaces as well as offers good observations on features like flow lines and crevasses. It mentions that the Recovery Glacier system plays a significant role in releasing East Antarctic ice to the sea. It also examines the importance of ice sheet surface velocity in assessing ice sheet balance and in figuring controls on ice sheet dynamics.

The flow of several large glaciers draining the Greenland Ice Sheet is accelerating. This change, combined with increased melting, suggests that existing estimates of future sea-level rise are too low. [ABSTRACT FROM AUTHOR]

Summary: The summer melt in Arctic ice is attracting increasing commercial interest in exploiting this once pristine region. Nigel Williams reports. [ABSTRACT FROM AUTHOR]