Albedo variations are presented at two on-glacier sites in the semi-arid Andes, Chile, with >3 years of continuous measurements. Although <2 km apart and at similar elevations, the sites show significantly different albedo cycles. Whereas Toro 1 exhibits a clear seasonal cycle, Guanaco reveals a more complicated pattern, as exposed ice can occur in any month of the year. Daily albedo values are as low as 0.18 for debris-covered Toro 1, while minima are higher on Guanaco (0.38). A method is presented to discern cloud-free from cloudy conditions using measured incoming shortwave radiation only. A cloud climatology is provided showing very low cloudiness values. We see that effective cloud cover relates inversely to cloud occurrence (i.e. either more but thin or fewer but thick clouds). The cloud-free diurnal albedo cycle is pronounced, with lowest values around noon. Clouds increase albedo by 0.04 as a median hourly value, and 0.20 for the 95% quantile. There is a positive relationship between effective cloud cover and resulting albedo rise. Calculations as to whether the diurnal albedo cycle or the effect of clouds on albedo should be considered in energy-balance estimations show that the former is necessary whereas the latter can be neglected in the semi-arid Andes.

Semi-permanent snow is part of the continuum between seasonal snow and glacier ice. Although ubiquitous in the High Arctic, most late-lying snow banks and snow beds have lost their perennial status over the past decade as the summers have become progressively warmer. The loss over the past decade is the most unprecedented since aerial photography of the Canadian Arctic islands was first undertaken over half a century ago, and it has produced observable thermal, hydrological and ecological impacts. Where the ground has become exposed beneath the perennial snow cover, seasonal ground thaw has deepened. Tundra ponds and patchy wetlands fed principally by meltwater in the summer have suffered water-level decline or desiccation. The water balance of headwater basins is also affected, losing a buffering vehicle that accumulates storage surplus from the wet cool years to support streamflow and evaporation in the dry warm years. The tundra vegetation, already sparse, undergoes changes in the long term. As an essential source of water in the polar desert environment, the widespread distribution of semi-permanent snow magnifies its Arctic-wide importance.

Twin time-lapse cameras were set up to provide a convergent view of ten targets located on the surface of an Arctic glacier, near its terminus. Using photogrammetric analysis, daily target elevations were calculated over three winters and two ablation seasons. Results show that the glacier surface level dropped by approximately 2.9 and 2.5 m respectively over the 2009 and 2010 ablation seasons. GPS measurements suggest the associated average vertical errors were 0.105 m and 0.04 m respectively. Photogrammetric measurements indicated that thinning from melting exceeded surface gains due to ice inflow by a factor of ~ 5: 1 during 2009 and 2010. Horizontal flow rates of 6–12 mm d–1 were measured photogrammetrically during autumn 2008 and compared to interpolated winter rates established from GPS measurements, with differences ranging between 7.4% and 17.2%. The availability of a continuous series of data for the duration of the study allowed the start and end dates of each ablation season to be identified, making it possible to determine the length of each balance year. The results show the utility of time-series photogrammetry for observing surface elevation changes and dynamic processes in remote glacial environments.

Oceanographic instruments suspended beneath the Amery Ice Shelf, East Antarctica, have recorded sporadic pressure decreases of 10–20 dbar over a few days at three sites where basal marine ice growth is expected. We attribute these events to flotation due to platelet ice accretion on the instrument moorings. Some events were transient, rapidly returning to pre-event pressures, probably through dislodgement of loosely attached crystals. Driven by these pressure changes, temperatures recorded by the shallowest instruments (within 20 m of the shelf base) tracked in situ freezing temperatures during the events. These observations provide indirect evidence for the presence of frazil ice in the sub-ice-shelf mixed layer and for active marine ice accretion. At one site we infer that a dense layer of platelet ice ˜1.5 m thick was accreted to the ice shelf over a 50 day period. Following some permanent abrupt pressure decreases (which we interpret as due to the lodgement of the uppermost instrument at the ice-shelf base), altered background trends in pressure suggest compaction rates of 3–4 m a–1 for the accreted basal platelet layer. Attachment of platelet ice and resulting displacement of moorings has ramifications for project design and instrument deployment, and implications for interpretation of oceanographic data from sub-ice-shelf environments.

Glacier dynamics are inextricably linked to the basal conditions of glaciers. Seismic reflection methods can image the glacier bed under certain conditions. However, where a seismically thin layer of material is present at the bed, traditional analyses may fail to fully characterize bed properties. We use a targeted full-waveform inversion algorithm to quantify the basal-layer parameters of a mountain glacier: thickness (d), P-wave velocity (α) and density (ρ). We simultaneously invert for the seismic quality factor (Q) of the bulk glacier ice. The inversion seeks to minimize the difference between the data and a one-dimensional reflectivity algorithm using a gradient-based search with starting values initialized from a Monte Carlo scheme. We test the inversion algorithm on four basal layer synthetic data traces with 5% added Gaussian noise. The inversion retrieved thin-layer parameters within 10% of synthetic test parameters with the exception of seismic Q. For the seismic dataset from Bench Glacier, Alaska, USA, inversion results indicate a thin basal layer of debris-rich ice within the study area having mean velocity 4000 ± 700 m s–1, density 1900 ± 200 kg m–3 and thickness 6 ± 1.5 m.