Following the collapse of Larsen A in 1995, about 3200 km2 of Larsen B ice shelf disintegrated in early 2002 during the warmest summer recorded on the northeastern Antarctic Peninsula. Immediately prior to disintegration the last field campaign was carried out on Larsen B. Measurements included surface net mass balance, velocity and strain rate on a longitudinal transect along Crane Glacier flowline and over a remnant section confined within Seal Nunataks that survived the collapse. In addition, an automatic weather station located nearby allowed derivation of melt days relevant to the formation and extent of surface meltwater. Repeated surveys allowed us to detect a significant acceleration in ice-flow velocity and associated increasing strain rates along the longitudinal transect. It may be possible to use this acceleration as a predictor of imminent ice-shelf collapse, applicable to ice shelves subject to similar climatic conditions. Additional information on recent ongoing changes was provided by a visible satellite image acquired in early 2003.

Using US National Centers for Environmental Prediction/US National Center for Atmospheric Research re-analysis data, we investigate the relationships between crustal ion (nssCa2+) concentrations from three West Antarctic ice cores, namely, Siple Dome (SD), ITASE00-1 (IT001) and ITASE01-5 (IT015), and primary components of the climate system, namely, air pressure/geopotential height, zonal (u) and meridional (v) wind strength. Linear correlation analyses between nssCa2+ concentrations and both air-pressure and wind fields for the period of overlap between records indicate that the SD nssCa2+ variation is positively correlated with spring circumpolar zonal wind, while IT001 nssCa2+ has a positive correlation with circumpolar zonal wind throughout the year (r > 0.3, p < 0.01). Intensified Southern Westerlies circulation is conducive to transport of more crustal aerosols to both sites. Further correlation analyses between nssCa2+ concentrations from SD and IT001 and atmospheric circulation suggest that the high inland plateau (represented by core IT001) is largely influenced by transport from the upper troposphere. IT015 nssCa2+ is negatively correlated with westerly wind in October and November, suggesting that stronger westerly circulation may weaken the transport of crustal species to IT015. Correlations of nssCa2+ from the three ice cores with the Antarctic Oscillation index are consistent with results developed from the wind-field investigation. In addition, calibration between nssCa2+ concentration and the multivariate El Niño–Southern Oscillation (ENSO) index shows that crustal species transport to IT001 is enhanced during strong ENSO events.

Drastic changes have been detected in glacial systems of the Antarctic Peninsula in the last few decades and are well documented in numerous scientific publications. However, the spatial and temporal distribution of glacier changes on the Antarctic Peninsula remains largely restricted to ice fronts. To expand the current monitoring of a few glaciers, unevenly distributed along the peninsula, to a representative set, we developed a method to simplify the detection of boundaries between glacier zones using satellite SAR data. The evolution of glacier zones is greatly influenced by local and regional climatic and meteorological settings. Their variations in response to changes in energy or mass balance are considered as good indicators of climatic changes. In this paper, we describe the results of knowledge-based image analysis algorithms on test areas located at Trinity Peninsula and near Marguerite Bay. In general, the two analyzed areas show different patterns of glacier zone development. The bare-ice zone occurs mainly on glaciers located on the eastern side of Trinity Peninsula. Its upper boundary shows a good correlation with the mean summer air temperature. Finally, the position of the dry-snow line shows different spatial patterns of change in both study areas.

Along most particle paths in polar ice sheets, ice experiences a slowly changing local deviatoric-stress pattern, and develops a fabric characteristic of its current stress state, in which there is generally a correspondence between non-zero strain-rate components and non-zero deviatoric-stress components. Where the stress pattern changes rapidly in special transition zones, fabric may evolve more slowly than the local stress field, and unusual or unexpected deformation patterns can result. The degree to which fabric tracks the local stress is determined by the relative characteristic times for changes in stress, given by the transition-zone width and ice velocity, and for changes in crystal orientation, given, in the absence of recrystallization, by the inverse of the local strain rate due to the principal stress. Recrystallization can significantly reduce the time-scale of fabric adjustment. We examine transition zones where ice (a) enters ice-stream margins, (b) is overrun by a migrating divide, and (c) flows through a strong saddle. Stress and fabric tend to be significantly misaligned in ice-stream margins and in flow through a saddle. When stresses that are markedly different from in situ stresses are applied to ice specimens during creep tests, deformation may be difficult to interpret.

An expendable bathythermograph (XBT) survey around an iceberg grounded in 100 m of water shows that iceberg melt-driven convection significantly alters the surrounding water properties in two ways, by a general cooling of the water in the upper 40 m by as much as 3 deg and by the formation of isothermal layers with a 5 m vertical-length scale in the pycnocline. Both of these effects become more pronounced as the distance to the iceberg decreases. The overall cooling of the upper layers supports the upwelling concept of Neshyba (1977) and of Josberger and Martin (in preparation*), while the formation of a step-like structure supports the cell formation idea of Huppert and Turner (1978) and Huppert and Josberger (1980).

Synoptic surface surveys around the iceberg show the existence of melt plumes containing water of a lower temperature than the adjacent water, and these plumes are detectable at distances of 0.5 km.

Concentrated rhodamine placed at depths of 14 and 18 m adjacent to an ice wall sloping down-ward at a 30° angle flowed upward along the ice. The dye reached the surface immediately next to the ice in 240 s and 540 s, respectively, to give a characteristic upward velocity of approximately 0.07 m s−1. The dye then dispersed outward away from the iceberg until it was no longer visible.

Pine Island Glacier (PIG), West Antarctica, has been experiencing acceleration in its flow speed and mass loss for nearly two decades, driven in part by an increase in the delivery of relatively warm Circumpolar Deep Water (CDW). However, at present, the configuration of the sub-ice-shelf cavity and bed conditions beneath the PIG ice shelf that dictate such oceanic influences remain poorly understood. Here, we use aerogravity data and ocean bottom depths measured by an autonomous underwater vehicle (AUV) to model the bathymetry and sediment layer thickness beneath the PIG ice shelf. Results reveal that the deep basins, previously found by AUV on both landward and seaward sides of a submarine ridge, extend substantially to the north and south. The water column thickness of the basins reaches 400-550 m on the landward side of the ridge and 500-600 m on the seaward side. The sediment layer covers the whole expanse of the seabed beneath the ice shelf, and the thickness is in the range ∼200-1000 m. The thinnest sediments (<200 m) are found on the seaward slope of the submarine ridge, suggesting that erosion by advancing ice may have been concentrated in the lee of the topographic high.

A conceptual precipitation–runoff model (HYCYMODEL) is used to simulate the daily runoff from the 67% glacierized Lirung basin (16% of which is covered by debris). The average thermal resistance of the debris cover of the Lrung Glacier has been estimated from the surface temperature of the debris, which was obtained from Landsat 5 (TM Band 6) images. This enabled calculation of the melt rate of the debris-covered area of the glacier using meteorological data collected at a nearby weather station. The calculated discharge results are roughly compatible with the observed daily discharges.

Following on from the successful project to recover an ice core to bedrock on Berkner Island, similar drilling equipment and logistics were used on two further projects to recover ice cores to bedrock in the Antarctic Peninsula. At James Ross Island, a ship- and helicopter-supported project drilled to bedrock at 363 m depth in a single season, while a Twin Otter-supported project drilled to bedrock at 654m depth, again in a single season, from Fletcher Promontory. In both new projects, drilling was from the surface, with the infrastructure enclosed in a tent, using an uncased, partially fluid-filled, borehole.

The temporal thermal stability, size, structure and spatial uniformity of Antarctic Plateau regions such as Dome C make them ideal candidates for external calibration and validation, or radiometric performance monitoring of planned space-borne L-band radiometers such as the Soil Moisture and Ocean Salinity (SMOS) radiometer. As experimental observations do not exist at this frequency, a combination of historical Ka-, X- and C-band data are used together with electromagnetic and ionospheric models to extrapolate to this longer wavelength. Dome C is demonstrated to exhibit negligible seasonal variability (<0.1 K) and may prove to be a suitable candidate, provided the effects of atmospheric and ionospheric perturbations can be mitigated.

Two-dimensional steady isothermal flow of a marine ice stream is studied. Gases of different relations between shear stress and longitudinal deviatoric stress in the ice stream are considered. Analysis of the ice-stream-ice-shelf transition zone shows that even if the longitudinal stress deviator in the ice stream is much larger than the shear stress (as it is in the ice shelf), the ice-stream-ice-shelf transition zone if singular and the full system of Stokes equations must be solved in it. Scales of fields in the transition zone and the relation between the ice thickness and the horizontal mass flux at the grounding line are found.

We investigated a buried surface-hoar layer using the SnowMicroPen (SMP), an instrument designed to measure detailed snowpack profiles.We collected data from two adjacent parts of a slope 6 days apart. In addition, one manual snowpack profile was sampled each day, as well as 50 quantified loaded column tests (QLCTs) which provided an index of shear strength. For the SMP data, a 900 m2 area was sampled on both days in a grid with points 3 mapart, with some sub-areas of more closely spaced measurements. We collected 86 SMP profiles on the first day and 129 on the second day. Our analyses involved manually locating layer boundaries and calculating statistics for the force signal through the surface-hoar layer. The shear strength index increased by 40% between the two sampling days, but the SMP data show no statistical difference in layer thickness, and the mean, minimum, median, and a variety of percentile measures of the SMP force signal through the layer also do not change. Interestingly, the maximum hardness, and the variance and coefficient of variation of the SMP signal, increased. Since the small SMP tip might only break one or a couple of bonds as it passes through the weak layer, we interpret these changes as being indicative of increasing bond strength. Though we cannot specifically tie the increasing maximum hardness of the SMP signal to our QLCT results, our work suggests that the maximum SMP signal within buried surface-hoar layers may be useful for tracking increases in the shear strength of those layers.

For the deep ice-core drilling community, the 2005/06 Antarctic season was an exciting and fruitful one. In three different Antarctic locations, Dome Fuji, EPICA DML and Vostok, deep drillings approached bedrock (the ice–water interface in the case of Vostok), emulating what had previously been achieved at NorthGRIP, Greenland, (summer 2003 and 2004) and at EPICA Dome C2, Antarctica (season 2004/05). For the first time in ice-core drilling history, three different types of drill (KEMS, JARE and EPICA) simultaneously reached the depth of ‘warm ice’ under high pressure. After excellent progress at each site, the drilling rate dropped and the drilling teams had to deal with refrozen ice on cutters and drill heads. Drills have different limits and perform differently. In this comparative study, we examine depth, pressure, temperature, pump flow and cutting speed. Finally, we compare a few parameters of ten different deep drills.

In order to reconstruct the palaeoglaciation in Fennoscandia and northern Asia during the late-Weichselian ice-age phase, simulations with the dynamic and thermodynamic ice-sheet model SICOPOLIS are carried out. Our focus is on the Last Glacial Maximum (LGM) around 20 kyr BP. Climate forcing is based on mean annualsur-face temperature and precipitation derived from present data and Palaeoclimatic Modelling Intercomparison Project (PMIP) UKMO21 results for the LGM. These distributions are interpolated via a glacial index defined by the Greenland Icecore Project (GRIP) δ18O record. The extent of the Scandinavian and the Barents ice sheets is reproduced in good agreement with the Quaternary Environments of the Eurasian North (QUEEN) reconstruction, but the Kara Sea and Taymyr Peninsula areas are excessively glaciated. The fast-flow regions derived from the simulations, which are generally connected to regions with a temperate base and temperate ice above, are compared to hypothesized palaeo-ice-stream locations, especially in the Norwegian Channel and the Baltic area. In the Norwegian Channel, temperate basal conditions with temperate ice above prevail and favour fast flow. In the Baltic area, ice-sheet advance is generally accompanied by slow ice velocities (<200 m a–1). Some temporary fast-flow features occur due to transitional temperate-base conditions, and higher velocities arise in retreat phases.

Barnes Ice Cap, Baffin Island, Canada, is a remnant of the Laurentide ice sheet that separated from it about 8500 years ago. Owing to recession of the ice cap during the Holocene, Pleistocene-age ice is now exposed along the margin in a distinctive bubble-rich white band. δ18O variations across the white ice resemble those in Canadian Arctic ice cores, suggesting that Barnes Ice Cap preserves a climatic record through the last glacial period, possibly reaching back into the previous (Sangamon) interglacial. the δ18O shift at the Wisconsin–Holocene transition (15‰) exceeds that in other Canadian and Greenland records and cannot be explained solely in climatic terms. A steady-state model reconstruction of the Laurentide ice sheet during the Last Glacial Maximum suggests that Late-glacial strata in Barnes Ice Cap originated high up (>2400ma.s.l.) and far “inland” on the ice sheet, along a ridge that extended between the ancestral Foxe and Keewatin ice domes.

The transformation of dry snow to firn is described by the transition between densification by deformationless restacking and densification by power-law creep. The observed decrease with temperature of the density at the snow-firn transition seems to result from the competition between grain-boundary sliding and power-law creep. These two densification processess occur concurrently in snow, although there are probably micro-regions in which sliding alone occurs. Validation of a geometrical densification model developed for ceramics has been obtained from densification data from several Antarctic and Greenland sites and from the characterization of the structure of polar firn.

Seismograms acquired on the McMurdo Ice Shelf, Antarctica, during an Austral summer melt season (November 2016–January 2017) reveal a diurnal cycle of seismicity, consisting of hundreds of thousands of small ice quakes limited to a 6–12 hour period during the evening, in an area where there is substantial subsurface melting. This cycle is explained by thermally induced bending and fracture of a frozen surface superimposed on a subsurface slush/water layer that is supported by solar radiation penetration and absorption. A simple, one-dimensional model of heat transfer driven by observed surface air temperature and shortwave absorption reproduces the presence and absence (as daily weather dictated) of the observed diurnal seismicity cycle. Seismic event statistics comparing event occurrence with amplitude suggest that the events are generated in a fractured medium featuring relatively low stresses, as is consistent with a frozen surface superimposed on subsurface slush. Waveforms of the icequakes are consistent with hydroacoustic phases at frequency $ {\bf \gt} \bf 75\,{\bf Hz}$ and flexural-gravity waves at frequency $ \bf {\bf \lt}25\,{\bf Hz}$. Our results suggest that seismic observation may prove useful in monitoring subsurface melting in a manner that complements other ground-based methods as well as remote sensing.

Measurements of sensible- and latent-heat fluxes under stable conditions are rare. In order to obtain indirect measurements of turbulent fluxes, meteorological data measured at the Col de Porte laboratory (1320 m a.s.l, France) under very stable conditions (cold, clear night with low wind) are used. The radiative fluxes are measured, the conduction within the snowpack is calculated using the snow model Crocus and the turbulent fluxes are determined as a residual term of the surface-energy balance equation. These data were used to fit a new parameterization of the turbulent fluxes for the snow model. The turbulent fluxes are increased as compared to the theory. Crocus was also applied to the data from the LEADEX92 experiment and the turbulent fluxes calculated by the model were compared to the fluxes measured using sonic anemometers/thermometers on the site.

Passive microwave-brightness temperatures over the Greenland ice sheet are examined during the melt season in order to develop a technique for determining surface-melt occurrences. Time series of Special Sensor Microwave/ Imager (SSM/I) data are examined for three locations on the ice sheet, two of which are known to experience melt. These two sites demonstrate a rapid increase in brightness temperatures in late spring to early summer, a prolonged period of elevated brightness temperatures during the summer, and a rapid decrease in brightness temperatures during late summer. This increase in brightness temperatures is associated with surface snow melting. An objective technique is developed to extract melt occurrences from the brightness-temperature time series. Of the two sites with summer melt, the site at the lower elevation had a longer period between the initial and final melt days and had more total days classified as melt during 1988 and 1989. The technique is then applied to the entire Greenland ice sheet for the first major surface-melt event of 1989. The melt-zone signal is mapped from late May to early June to demonstrate the advance and subsequent retreat of one “melt wave”. The use of such a technique to determine melt duration and extent for multiple years may provide an indication of climate change.

The dynamic/thermodynamic shallow-ice model SICOPOLIS is applied to the Greenland ice sheet. Paleoclimatic spin-ups from 125 ka BP until today, as well as future-climate experiments 500 years into the future, are carried out with three different grid spacings, namely 20, 10 and 5 km. The scenarios are a subset of those specified by the SeaRISE (Sea-level Response to Ice Sheet Evolution) community effort. The bed topography includes improved troughs for Jakobshavn Isbræ, Helheim, Kangerdlugssuaq and Petermann glaciers, processed by an algorithm that preserves shape, orientation and continuity of the troughs on the 5 km scale. Comparison of simulated and observed present-day surface velocities shows that these ice streams and outlet glaciers are resolved with different accuracies, ranging from poor (20 km grid) to reasonably good (5 km grid). In the future-climate experiments, the simulated absolute ice volumes depend significantly on the resolution, while the sensitivities (ice volumes relative to the constant-climate control run) vary only by a few centimeters of sea-level equivalent.

Although the disaster reduction effects of forest braking have long been known empirically, they have not been known in detail down to recent. In this study, we ascertained forest braking effect by numerical simulations using the avalanche dynamics program, TITAN2D, to model large-scale avalanches. One of these avalanches occurred in the Makunosawa valley, Myoko, and damaged a cedar forest; the others occurred on Mt. Iwate and damaged a subalpine forest. All avalanches damaged many trees and terminated within the forests. In our simulations, the resistance of the forests to avalanches is simulated using a larger bed friction angle. Fitting the observations from the Makunosawa avalanche by trial and error, a bed friction angle of 13–14° in the non-forested area and of 25° in the forested area is obtained. We conducted simulations of the Mt. Iwate avalanches using the same method as for the Makunosawa valley avalanche, and obtained good agreement between observations and simulations. Simulations reveal that without the forest, the avalanche would have traveled at least 200 m farther than the forest's actual end in the Makunosawa valley, and at least 200 m and possibly up to 600 m farther on Mt. Iwate. This study therefore clearly shows that forests provide a braking effect for avalanches.