The transition of the International Commission on Snow and Ice (ICSI) of the International Association of Hydrological Sciences (IAHS) to become the International Association of Cryospheric Sciences (IACS) within the International Union of Geodesy and Geophysics (IUGG) is described. IACS was accepted as the eighth Association of IUGG in 2007 and is the first new Association of the Union to be formed in over 80 years. Particular attention is paid to the reasons that prior to 1999 led to the request by the Commission to the Union for a change in status, and to the steps taken during the period 1999–2007 by the ICSI Bureaux and IUGG, that preceded the acquisition of Association status.

Collections of disaggregated snow particles were examined in a temperature-controlled microscope stage. In addition to necks that appeared to sinter in a manner congruent with the two-particle model, there also appeared unanticipated dendritic growth, which developed on some grains and grew into the pore space. These branches developed preferentially only on part of, and in different directions on, individual grains. Some of these grew enough to join with adjacent grains that were in close proximity but not initially in contact, while the surface of the adjacent grains did not show measurable growth or loss. Growth orientation is hypothesized to be due to crystal habit dependence on temperature. Columnar growth was observed at –5˚C and plate-like at –15˚C. The random growth orientation is in contrast to observed source and sink development aligned with a temperature gradient imposed using a gradient stage. In this case, a source-to-sink directionality across the pore was apparent in which faceted crystals grew at the expense of neighboring source grains. The process of mechanically disaggregating snow produces numerous broken shards and sharp-edged fracture surfaces. We hypothesize that it is the sublimation of these high-surface-energy regions that provides the excess vapor to facilitate the diffusion-limited dendritic growth observed in this ‘equitemperature’, mechanically processed snow.

The metamorphism of seasonal snow is classically considered as limited by vapour diffusion in the pore phase. To account for the lack of knowledge of the ice–vapour reaction coefficient near 0°C, the assumption of a reaction-limited metamorphism was first tested in three-dimensional simulations at low and very low temperature gradients; however, the validity of such results is difficult to verify experimentally. By a reasoned use of traditional iterative schemes, vapour diffusion is now simulated in three dimensions on tomographic snow data, mapping the gradient of vapour pressure near the grains. Repeating this process may provide a way to simulate the isothermal metamorphism without grain packing at a reasonable expense of computation time. Preliminary results are compared with existing computations made within the reaction-limited hypothesis.

A new sub-seasonal chemical record is presented from the North Greenland Icecore Project (NorthGRIP) ice core during the onset of one of the longest and strongest interstadials of the last glacial period, Dansgaard–Oeschger event 8 (approximately 38 000 years ago). This is the first time that a record of such resolution has been achieved over several metres of deep glacial ice and provides a unique opportunity for using additional parameters to carry out accurate dating using annual-layer counting. The very high-resolution chemical data were used to assess the phasing of various ions and determine changes in the seasonal strength of chemical deposition and the shape of the seasonal cycle. The study shows that a change in seasonality accompanied the dramatic warming transition from stadial to interstadial conditions in Greenland.

We present the results of preliminary investigations of globular moss growth on the surface of Falljökull, a temperate outlet glacier of the Vatnajökull ice cap, southern Iceland. Supraglacial debris has provided a basis for moss colonization, and several large (>500m2) patches of moss growth (Racomitrium spp.) are observed on the surface of the glacier. Each area of moss-colonized supraglacial debris shows a downslope increase in sphericity and moss cushion size and a decrease in percentage surface coverage of moss-colonized and bare clasts. It is suggested that moss growth on supraglacial debris allows preferential downslope movement of clasts through an associated increase in both overall mass and sphericity. Thermal insulation by moss cushions protects the underlying ice surface from melt, and the resulting ice pedestals assist in downslope sliding and toppling of moss cushions. The morphology and life cycle of supraglacial globular mosses is therefore not only closely linked to the presence and distribution of supraglacial debris, but also appears to assist in limited down-glacier transport of this debris. This research highlights both the dynamic nature of the interaction of mosses with supraglacial sedimentary systems and the need for a detailed consideration of their role within the wider glacial ecosystem.

A degree-day model extended for surface mass-balance calculations has been applied to derive the sensitivity of Gran Campo Nevado ice cap (GCN), southwest Patagonia, to climate change. Seasonal sensitivity characteristics were computed using automatic weather station data gathered in the period 2000–05. Results indicate pronounced mass-balance sensitivity to temperature during the summer, with monthly values of –0.27±0.01mw.e. K–1. Monthly sensitivity to a 10% precipitation perturbation fluctuates around +0.03mw.e The sensitivity characteristics obtained were used to model the surface mass-balance evolution of GCN during the 20th and 21 st centuries based on monthly means of air temperature and precipitation derived from bias-corrected weather station data and statistically downscaled re-analysis and general climate model data. Surface mass balance shows a persistently negative trend ranging from around +1mw.e. a–1 at the beginning of the 20th century down to almost –1.5mw.e. a–1 during the first years of the 21st century, with only a few positive years occurring occasionally during the second half of the 20th century. The scenario for the end of the 21 st century totals approximately –4.5mw.e. a–1, i.e. an estimated ice volume loss for GCN of 59 km3 during 1900–2099.

The majority of glaciers in central Chile have receded in recent decades, from >50m to only a few meters per year, mainly in response to an increase in the 0˚C isotherm altitude. The Aconcagua river basin (33˚ S) is one of the major glaciated basins in central Chile, with 121 km2 of ice in 2003. An earlier inventory using 1955 aerial photographs yielded a total surface area of 151 km2, implying a reduction in glacier area of 20% (0.63km2 a–1) over the 48 years. Photographic stereo models, high-resolution satellite images (Landsat, ASTER) and SRTM data have been used to delineate glacier basins. A focus on Glaciar Juncal Norte, one of the largest glaciers in the basin, allows a more detailed analysis of changes. The glacier has exhibited a smaller reduction (14%) between 1955 and 2006, and the resulting elevation changes over this smaller period are not significant. The above reduction rates are lower than in other glaciers of central Chile and Argentina. This trend emphasizes water runoff availability in a river where most of the water in the dry summers is generated by glaciers and snowpack, and where most of the superficial water rights are already allocated. Ongoing hydrological research including modelling of future water runoff will improve our understanding.

A distributed surface energy-balance study was performed to determine sub-debris ablation across a large part of Baltoro glacier, a wide debris-covered glacier in the Karakoram range, Pakistan. The study area is ~124km2. The study aimed primarily at analyzing the influence of debris thickness on the melt distribution. The spatial distribution of the physical and thermal characteristics of the debris was calculated from remote-sensing (ASTER image) and field data. Meteorological data from an automatic weather station at Urdukas (4022ma.s.l.), located adjacent to Baltoro glacier on a lateral moraine, were used to calculate the spatial distribution of energy available for melting during the period 1–15 July 2004. The model performance was evaluated by comparisons with field measurements for the same period. The model is reliable in predicting ablation over wide debris-covered areas. It underestimates melt rates over highly crevassed areas and water ponds with a high variability of the debris thickness distribution in the vicinity, and over areas with very low debris thickness (<0.03 m). We also examined the spatial distribution of the energy-balance components (global radiation and surface temperature) over the study area. The results allow us to quantify, for the study period, a meltwater production of 0.058 km3.

We examine the role of the propagation of atmospheric mid-latitudes wave trains in modulating the Amundsen and Bellingshausen sea-ice area (SIA), Antarctica, on intra-seasonal timescales (20–100 days). Spectral analysis of passive microwave estimates of SIA in the Amundsen and Bellingshausen Seas for 1979–2004 shows significant peaks on intra-seasonal timescales. Previous studies have suggested that variations in SIA are linked to disturbances in atmospheric circulation and sea surface temperature. We show that extreme SIA anomalies on intra-seasonal timescales lag the propagation of subtropical wave trains in the Southern Hemisphere by approximately 10–15 days. The sign of the SIA anomaly depends on the phase of the wave. We present evidence that the number of disturbances that cause extreme anomalies of SIA on intra-seasonal timescales has increased in the last 14 years.

Passive microwave sea-ice concentration fields provide some of the longest-running and most consistent records of changes in sea ice. Scatterometry-based sea-ice fields are more recently developed data products, but now they provide a record of ice conditions spanning several years. Resolution enhancement techniques applied to scatterometer fields provide much higher effective resolutions (~10 km) than are available from standard scatterometer and passive microwave fields (25–50 km). Here we examine ice-extent fields from both sources and find that there is general agreement between scatterometer data and passive microwave fields, though scatterometer estimates yield substantially lower ice extents during winter. Comparisons with ice-edge locations estimated from AVHRR imagery indicate that enhanced scatterometer data can sometimes provide an improved edge location, but there is substantial variation in the results, depending on the local conditions. A blended product, using both scatterometer and passive microwave data, could yield improved results.

This paper explores spatial and temporal relationships between variations in Arctic sea-ice concentration (summer and winter) and near-surface atmospheric temperature and atmospheric pressure using multivariate statistical techniques. Trend, empirical orthogonal function (EOF) and singular value decomposition (SVD) analyses are used to identify spatial patterns associated with covariances and correlations between these fields. Results show that (1) in winter, the Arctic Oscillation still explains most of the variability in sea-ice concentration from 1979 to 2006; and (2) in summer, a decreasing sea-ice trend centered in the Pacific sector of the Arctic basin is clearly correlated to an Arctic-wide air temperature warming trend. These results demonstrate the applicability of multivariate methods, and in particular SVD analysis, which has not been used in earlier studies for assessment of changes in the Arctic sea-ice cover. Results are consistent with the interpretation that a warming signal has now emerged from the noise in the Arctic sea-ice record during summer. Our analysis indicates that such a signal may also be forthcoming during winter.

An assessment of the glaciological and meteorological characteristics of Dome A, the summit of the East Antarctic ice sheet, is made based on field investigations during the austral summer of 2004/05. Knowledge of these characteristics is critical for future international studies such as deep ice-core drilling. The assessment shows that: (1) Dome A is characterized by a very low 10m depth firn temperature, –58.3˚C (nearly 3˚C lower than at EPICA Dome C and 1˚C lower than at Vostok). (2) Automatic weather station (AWS) measurements of snow surface height and reference layers in a snow pit indicate the present-day snow accumulation rate at Dome A is within the range 1–3cmw.e. a–1. Densification models suggest a range of 1–2cmw.e. a–1. This is lower than at other sites along the ice divide of East Antarctica (IDEA). Annual layers at Dome A are thus potentially thinner than at other sites, so that a longer record is preserved in a given ice thickness. (3) The average wind speed observed at Dome A (<4ms–1) is lower than at other sites along IDEA. Together, these parameters, combined with radio-echo sounding data and information on the subglacial drainage distribution beneath Dome A, suggest Dome A as a candidate site for obtaining the oldest ice core.

Numerical calculations are described, aimed at evaluating the influence of precipitation seasonality (summer and winter) on glacier mass balance. First, equilibrium-line altitudes (ELAs) are modeled using idealized meteorological variables. Modeled climatic conditions (summer mean temperature and annual precipitation) at the ELA of glaciers located within a winter accumulation pattern confirm the observational results of earlier studies. However, the ELA of glaciers located within a summer accumulation climate pattern locates in a colder environment than that of glaciers located within a winter accumulation climate pattern. This difference is mainly due to the annual snow accumulation and the surface albedo. A warming test (+1K) reveals higher sensitivities for the glaciers located within a summer accumulation pattern than for the glaciers located within a winter accumulation pattern. In a humid environment, a significant decrease in snow accumulation on the glaciers located within a summer accumulation pattern directly causes higher sensitivities. In an arid environment, on the other hand, the decreased summer snow induces accelerated melting by lowering the surface albedo and thus increasing absorption of solar radiation on the glaciers located within a summer accumulation pattern. Both influences are due to significant differences in summer precipitation. This study shows the importance of precipitation seasonality on the climatic sensitivity of glacier mass balance, which in previous studies has been linked only with annual precipitation.

Changes of the equilibrium-line altitude (ELA) since the end of the Little Ice Age (LIA) in eastern Nepal have been studied using glacier inventory data. The toe-to-headwall altitude ratios (THARs) for individual glaciers were calculated for 1992, and used to estimate the ELA in 1959 and at the end of the LIA. THAR for debris-free glaciers is found to be smaller than for debris-covered glaciers. The ELAs for debris-covered glaciers are higher than those for debris-free glaciers in eastern Nepal. There is considerable variation in the reconstructed change in ELA (ΔELA) between glaciers within specific regions and between regions. This is not related to climate gradients, but results from differences in glacier aspect: southeast- and south-facing glaciers show larger ΔELAs in eastern Nepal than north- or west-facing glaciers. The data suggest that the rate of ELA rise may have accelerated in the last few decades. The limited number of climate records from Nepal, and analyses using a simple ELA–climate model, suggest that the higher rate of the ΔELA between 1959 and 1992 is a result of increased warming that occurred after the 1970s at higher altitudes in Nepal.

No continuous record from Greenland of the Eemian interglacial period (130–115 ka BP) currently exists. However, a new ice-core drill site has been suggested at 77.449˚ N, 51.056˚Win north-west Greenland (North Eemian or NEEM). Radio-echo sounding images and flow model investigations indicate that an undisturbed Eemian record may be obtained at NEEM. In this work, a two-dimensional ice flow model with time-dependent accumulation rate and ice thickness is used to estimate the location of the Eemian layer at the new drill site. The model is used to simulate the ice flow along the ice ridge leading to the drill site. Unknown flow parameters are found through a Monte Carlo analysis of the flow model constrained by observed isochrones in the ice. The results indicate that the Eemian layer is approximately 60m thick and that its base is located approximately 100m above bedrock.

Three-dimensional (3-D) snow analysis techniques provide comprehensive and accurate snow microstructure data. Nevertheless, there remains a requirement for less elaborate methods for snow characterization, as numerical snow models such as SNOWPACK are presently based on two-dimensional (2-D) grain analysis. We present a detailed assessment of various methods and shape descriptors used for snow characterization from digitized images. Dendricity, the ratio of the square of grain perimeter to its area, allows distinction between new and old snow while sphericity distinguishes between faceted and rounded grains. The concept of sphericity is based on curvature, yet another powerful shape descriptor. However, curvatures obtained from images of disaggregated snow grains depend on both resolution and methods chosen. We compared the standard parabola method with a cubic smoothing spline approach for curvature measurement. Applying both methods to parametrically generated shapes, descriptor values were compared with their analytical counterparts. The spline method was found to be able to measure a wider range of curvatures accurately, but both methods suffered from a filtering effect. Although some descriptor errors were as high as 50%, a method for effectively outlining snow grains was found. As well as assessing the classification potential of 2-D analysis on full samples, new descriptors were also investigated.

Dome A, the highest point on the Antarctic ice sheet at just over 4000 ma.s.l., is located near the centre of East Antarctica. Chinese National Antarctic Research Expeditions have studied ice-sheet dynamics and mass balance along a traverse route from Zhongshan station to Dome A during the austral summers from 1996/97 to 2004/05. Nineteen GPS sites were occupied on at least two occasions at approximately 50 km intervals. The purpose of the surveys was to provide accurate ice-dynamics data. A dual-frequency GPS receiver was used and each site was occupied for 1–12 hours. GPS data were processed using GAMIT/GLOBK software, and horizontal accuracies were within 0.1 m. Repeat GPS measurements provided ice velocities. The horizontal surface ice velocities increase from the summit of the ice sheet to the coast. In the Dome A area, the velocities are <10ma–1; in the plateau area, velocities range from 8 to 24 ma–1 and reach about 98.2 ma–1 at a site (LT980) near the coast. The flow directions are roughly perpendicular to the ice-sheet surface elevation contours, primarily toward the Lambert Glacier basin.

Records of discharge of rivers draining Alpine basins with between 0 and ~70% ice cover, in the upper Aare and Rhône catchments, Switzerland, for the period 1894–2006 have been examined together with climatic data for 1866–2006, with a view to assessing the effects on runoff from glacierized basins of climatic warming coupled with glacier recession following the Little Ice Age maximum. Annual runoff from ice-free basins reflects precipitation variations, rising from minima between 1880 and 1910 to maxima between the late 1960s and early 1980s. The more highly glacierized the basin, the more runoff mimicked mean May–September air temperature during two periods of warming. Runoff increased gradually from the 1900s, rapidly in the 1940s, before decreasing to the late 1970s. Rising runoff levels during the second warming period failed to exceed those attained during the first, despite higher summer temperatures. Although temperatures continued to rise, discharge from glacierized basins declined after reaching maxima in the late 1980s to early 1990s. In the first warming period, rising specific melt rates augmented by increasing precipitation opposed the impact of declining glacier area on runoff. Although melt continued to increase in the second period, enhanced melting (even in the exceptionally warm summer of 2003) appears to have been insufficient to offset reducing glacier surface area exposed to melt, low or reducing levels of precipitation, and increasing evaporation. Thus runoff from glacierized basins peaked in the late 1940s to early 1950s.

The evolution of surging glaciers of the Pamirs, central Asia, has been studied using repeat remote-sensing surveys in the Institute of Geography, Russian Academy of Sciences, since the early 1970s. We use images obtained from national Resurs-F satellites (1972–91), as well as Landsat 7 and Terra (1999–2006), to provide a basis for monitoring of surging glaciers, aimed at developing their inventory, studying the causes and mechanisms of surges and examining the timing and extent of glacial catastrophes. The inventory from the early 1990s allows identification of 215 glaciers with a dynamically unstable regime. We discovered 51 surging glaciers. Up until 2006, 10 more surges had occurred. We use stereoscopic deciphering and photogrammetric processing of consecutive satellite images to study the morphology and ice-velocity changes of several compound surging glaciers. We analyze the results of monitoring of Bivachny and Oktyabr’sky glaciers from 1972 to 1991 and Sugran glacier from 1972 to 2006. Two surges of Sugran glacier occurred during this time: an internal surge in 1976–80, and a surge with glacier tongue advance as far as 4.5 km in 2000–05. The role of damming in compound glacier systems is examined. Satellite-based monitoring is now the only method for obtaining initial information about the state and fluctuations of such glaciers.

Rotated principal components of the 500 hPa geopotential heights in the Euro-Atlantic sector are used as indicators of circulation pattern intensity. Daily snow-cover depth data for the years 1951–95 from 71 eastern European stations are examined. Maps of linear correlation coefficient between monthly change in snow depth and rotated principal components are presented. The positive and negative extremes of each circulation pattern are analyzed, and positive and negative snow-depth signals indicated. A daily analysis of relationships between snow depth and circulation pattern is performed for three locations. The strongest impact of the atmospheric circulation on changes in snow depth is observed in the south and west of the study area, where the eastern European (EE) and central European circulation patterns are found to have the greatest impact. The North Atlantic Oscillation (NAO) impact on the snow depth in eastern Europe is limited to the beginning and the end of winter. Snow cover has low variability in northeastern Europe (where the Scandinavian (SC) pattern is of greatest importance) and low sensitivity to change in the atmospheric circulation. The decrease in snow-cover depth observed in spring is related to the NAO, SC and EE patterns, the latter being important for snow-cover depth fluctuations over northeastern Europe in April.