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In contrast to the general trend for glaciers of the Southern Patagonia Icefield, Glaciar Pio XI has experienced a large cumulative frontal advance since 1945. In an effort to better understand this advancing behaviour, this paper presents a synoptic analysis of frontal fluctuations (1998–2014), ice velocities (1986–2014), ice-surface elevations (1975–2007) and supraglacial moraines (1945–2014) derived from geospatial datasets. These analyses reveal changes in the ice flow of Glaciar Pio XI's freshwater calving northern terminus and tidewater calving southern terminus over recent decades. Between 1986 and 2000, ice flow speed generally accelerated reaching peaks of >15 m d−1 at the frontal edge of the southern terminus. Following this period, flow speed decreased, reducing to −1 for the central part of the southern terminus in 2014, despite advancing to a neoglacial maximum. From 2000 to 2014 the reduction in speed was accompanied by a shift in maximum velocity away from the southern terminus, towards the central glacier trunk. As a result, the northern terminus, which accelerated during this period, represented the new primary flow path in 2014. Notably, the moraine maps presented highlight surges occurring around 1981 and again between 1997 and 2000, marked by arcuate moraine features on the southern terminus.

Despite their importance as freshwater reservoirs for downstream river systems, few glaciers in central Chile have been comprehensively surveyed. This study presents ground-penetrating radar (GPR) and field-based observations for characterizing the englacial and basal conditions of Glaciar Olivares Alfa (33°110 S, 70°130 W), central Chilean Andes. Using a 50 MHz radar mounted onto a helicopter platform, data were collected covering large portions of the glacier accumulation and ablation zones. The radar data revealed boundaries of a temperate-ice layer at the base of the eastern body of Glaciar Olivares Alfa which appears to be covered by colder ice that extends throughout large parts of the glacier. The thickness of the temperate ice layer is highly variable across the glacier, being on average 40% of the total ice thickness. Radar data analyses reveal regions of cold ice at the bottom/base of the glacier and also patterns of highly saturated sediments beneath the glacier. Using GPR data, this study represents the most exhaustive analysis of glacier ice structure performed in the central Chilean Andes. The results will enable improved estimations of the glacier’s mass balance and ice dynamics, helping us to understand its further development and its impact on water availability.

In order to measure total ice thickness and surface snow accumulation in Antarctica, we have designed and built a surveying system comprising two types of radar. This system is aimed at having low power consumption, low weight/volume and low construction cost. The system has a pulse-compression radar to measure ice thickness, and a frequency-modulated continuous wave (FM-CW) radar designed to measure hundreds of meters of surface snow/firn layers with high resolution. The pulse-compression radar operates at 155MHz, 20 MHz of bandwidth; and the FM-CW radar operates from 550 to 900 MHz. The system was tested in December 2010 at Union Glacier (79°46'S, 83°24'W), West Antarctica, during an oversnow campaign, where Union and other nearby glaciers (Schanz, Schneider and Balish) were covered through 82 km of track. Ice thickness of 1540m and snow/firn thickness of 120 m were detected in the area. The collected data allowed the subglacial topography, internal ice structure, isochronous and the snow/ice boundary layer to be detected. Here we describe radar electronics, their main features and some of the results obtained during the first test campaign. Further improvements will focus on the adaptation of the system to be implemented on board airplane platforms.

Tidewater calving glaciers can undergo large fluctuations not necessarily in direct response to climate, but rather owing to complex ice–water interactions at the glacier termini. One example of this process in Chilean Patagonia is Glaciar Jorge Montt, where two cameras were installed in February 2010, collecting up to four glacier photographs per day, until they were recovered on 22 January 2011. Ice velocities were derived from feature tracking of the geo-referenced photos, yielding a mean value of 13 ±4 md–1 for the whole lower part of the glacier. These velocities were compared to satellite-imagery-derived feature tracking obtained in February 2010, resulting in similar values. During the operational period of the cameras, the glacier continued to retreat (1 km), experiencing one of the highest calving fluxes ever recorded in Patagonia (2.4 km3 a–1). Comparison with previous data also revealed ice acceleration in recent years. These very high velocities are clearly a response to enhanced glacier calving activity into a deep water fjord.

Regional climate warming has caused several ice shelves on the Antarctic Peninsula to retreat and ultimately collapse during recent decades. Glaciers flowing into these retreating ice shelves have responded with accelerating ice flow and thinning. The Wordie Ice Shelf on the west coast of the Antarctic Peninsula was reported to have undergone a major areal reduction before 1989. Since then, this ice shelf has continued to retreat and now very little floating ice remains. Little information is currently available regarding the dynamic response of the glaciers feeding the Wordie Ice Shelf, but we describe a Chilean International Polar Year project, initiated in 2007, targeted at studying the glacier dynamics in this area and their relationship to local meteorological conditions. Various data were collected during field campaigns to Fleming Glacier in the austral summers of 2007/08 and 2008/09. In situ measurements of ice-flow velocity first made in 1974 were repeated and these confirm satellite-based assessments that velocity on the glacier has increased by 40–50% since 1974. Airborne lidar data collected in December 2008 can be compared with similar data collected in 2004 in collaboration with NASA and the Chilean Navy. This comparison indicates continued thinning of the glacier, with increasing rates of thinning downstream, with a mean of 4.1 ± 0.2 m a−1 at the grounding line of the glacier. These comparisons give little indication that the glacier is achieving a new equilibrium.

We describe the development of a low-frequency airborne radar specifically designed for the sounding of temperate ice. The system operates at a central frequency of 1 MHz and consists of an impulse transmitter with an output voltage up to 5000 V and a digital receiver with a maximum gain of 80 dB. The radar was deployed on board a CASA 212 aircraft, which also carries a laser altimeter, an inertial navigation system, a digital camera and a GPS receiver. A description of the radar system is provided, as well as preliminary results obtained at Glaciar Tyndall, Campo de Hielo Sur (Southern Patagonia Icefield), where an ice depth of 670 m was reached.

In January 2003, shallow firn cores were recovered from Glaciar Esmeralda on Cerro del Plomo (33°14’S, 70°13’W; 5300 ma.s.l.), central Chile, and from Glaciar La Ollada on Cerro Mercedario (31°58’S, 70°07’W; 6070 ma.s.l.), Argentina, in order to find a suitable archive for paleoclimate reconstruction in a region strongly influenced by the El Nino-Southern Oscillation. In the area between 28°S and 35°S, the amount of winter precipitation is significantly correlated to the Southern Oscillation Index, with higher values during El Nino years. Glaciochemical analysis indicates that the paleo-record at Glaciar La Ollada is well preserved, whereas at Glaciar Esmeralda the record is strongly influenced by meltwater formation and percolation. A preliminary dating of the Mercedario core by annual-layer counting results in a time-span of 17 years (1986-2002), yielding an average annual net accumulation of 0.45 m w.e.

The variations and dynamics of the southern edge of Fuchs Ice Piedmont, Adelaide Island (67˚45’ 09’ S, 68˚55’ 04’ W), Antarctic Peninsula, are presented. The snow-covered surface of the glacier has been used since the 1960s for landing aeroplanes in support of British, and more recently Chilean, operations at nearby Teniente Carvajal station (formerly known as Adelaide T). In recent years, snow conditions in the runway area have progressively deteriorated, due to increasingly early summer melting. Radio-echo sounding, global positioning system and remotely sensed data have been analyzed for mapping the crevasse and ice velocity fields, as well as the surface and subglacial topography of the area. The results show that the runway area is located on a local ice divide surrounded by crevasses which are appearing on the glacier surface progressively earlier in the summer, presumably due to higher snowmelt and perhaps higher ice velocities, in response to regional atmospheric warming. In the near future, landing operations will be further affected as more crevasses will appear in the runway area if present warming trends persist. This situation affects all coastal areas in the Antarctic Peninsula, hence the need to search for possible new locations of crevasse-free runways at higher elevations.

We report measurements of ice surface elevation, ice thickness and surface area for Glaciar Tyndall, Patagonia, made in 1999–2002. The measurements, together with previously published observations, show acceleration over the last few decades of the rates of thinning and retreat of the main calving front. The acceleration of shrinkage appears to be driven by a combination of climate and feedback processes, the dominant feedback being increased melting associated with lowering of the glacier surface (elevation feedback). The melting capacity in the main terminus lake is now too small to be a major factor accelerating the retreat. The glacier bed has low slope and remains below the elevation of the lake spillway for >14 km upstream from the 2000 calving front, indicating the potential for extensive retreat under the influence of strong elevation feedback and increasing interaction with the lake as it enlarges.

Hielo Patagónico Sur (HPS; southern Patagonia icefield) is the largest temperate ice mass at mid-latitudes in the Southern Hemisphere. With few exceptions, the glaciers in this region have been retreating during the last 50 years. Based on field data, vertical aerial photographs and satellite images, ice-elevation changes since 1975 on Glaciar Chico, one of the main tongues of HPS, are presented. A maximum ice thinning of 5.4 ± 0.55 m a-1 was observed at the glacier front between 1975 and 1997. Global positioning system (GPS) data were used in the accumulation area of the glacier to infer a thinning rate of 1.9 ± 0.14 m a-1 between 1998 and 2001. This thinning rate is three times higher than the snow accumulation rate estimated for that part of the glacier. A mean net glacier mass balance of -0.29 ± 0.097 km3 w.e. a-1 was estimated between 1975 and 2001. Climate data suggest an increase in temperature and a reduction in precipitation during most of the 20th century in the vicinity of HPS. Although these climate changes are the primary explanation for the observed ice-elevation changes of the glacier, ice-dynamics effects are also believed to play an important role.

Patriot Hills is located at 80˚18’ S, 81˚22’W, at the southernmost end of the Heritage Range, Ellsworth Mountains, West Antarctica. A comparison of glacier elevation data and ice velocities obtained by the differential global positioning system in the period 1996–97 is presented. Ablation/accumulation rates measured at a network of stakes in Horseshoe Valley show average accumulation of 70 kg m–2 a–1 in the central part of the valley, and a maximum ablation of ∼170 kg m–2 a–1 at the edge of the blue-ice area, close to Patriot Hills. Changes in the surface elevation of the glacier measured at 81 stakes in the period 1995–97 show a mean thickening of +0.43±0.42ma–1, which, considering the uncertainties, indicates that the ice sheet around Patriot Hills is in near steady state. Surface velocities, in combination with ice thicknesses obtained by ground-based radio-echo sounding, are used to compute the ice flux across the Horseshoe Valley transect. A total outflow of 0.44 ±0.08km3 a–1 is obtained. Considering a catchment area for Horseshoe Valley of 1087 km2 upstream from the flow transect, and a net accumulation rate of 100 kg m–2 a–1, a total input of 0.11 ±0.04km3 a–1 by snow accumulation is obtained. Accepting a near-equilibrium condition for the ice sheet, the flux difference, i.e. 0.33 km3 a–1, must be supplied by flow from the inland ice sheet through ice cliffs located in mountain gaps in the Heritage Range. If Horseshoe Valley is not in steady state but is thickening, the positive mass balance could be due to increased snow accumulation or enhanced ice flow from the interior of the ice sheet. New data are needed to elucidate this.

In November–December 2002, a joint airborne experiment by Centro de Estudios Cientifícos and NASA flew over the Antarctic ice sheet to collect laser altimetry and radio-echo sounding data over glaciers flowing into the Amundsen Sea. A P-3 aircraft on loan from the Chilean Navy made four flights over Pine Island, Thwaites, Pope, Smith and Kohler glaciers, with each flight yielding 1.5–2 hours of data. The thickness measurements reveal that these glaciers flow into deep troughs, which extend far inland, implying a high potential for rapid retreat. Interferometric synthetic aperture radar data (InSAR) and satellite altimetry data from the European Remote-sensing Satellites (ERS-1/-2) show rapid grounding-line retreat and ice thinning of these glaciers. Using the new thickness data, we have reevaluated glacier fluxes and the present state of mass balance, which was previously estimated using ice thicknesses deduced largely from inversion of elevation data assuming hydrostatic equilibrium. The revised total ice discharge of 241 ± 5km3 a–1 exceeds snow accumulation by 81 ± 17 km3 a–1 of ice, equivalent to a sea-level rise of 0.21 ± 0.04 mma–1. This magnitude of ice loss is too large to be caused by atmospheric forcing and implies dynamic thinning of the glaciers. This is confirmed by ice-flow acceleration observed with InSAR. We attribute the flow acceleration and ice thinning to enhanced bottom melting of the ice shelves by a warmer ocean, which reduces buttressing of the glaciers, and in turn accelerates them out of balance.

A synthesis of glaciological studies carried out in Chile during recent decades is presented, including inventories and records of glacier variations, fluctuations of which are related to regional climate change and their contribution to eustatic sea-level rise. Based upon satellite imagery, aerial photographs and historical records, new data for 20 glaciers are presented. These new data are combined with previous records to cover the historical variations of 95 Chilean glaciers. Of these glaciers, only 6% show a net advance during the study period, 6% show no significant change, while 88% have retreated. The contribution of Chilean glaciers to eustatic sea-level rise has been estimated to be approximately 8.2% of the worldwide contribution of small glaciers on Earth during the last 51 years. Most of the glacier variations are thought to have been driven by a temperature increase, which has been documented by several stations in Chile. Anomalies in rainfall, and the decreasing trend in annual precipitation shown at a few stations, have probably also contributed to glacier recession. Based on observed climatic trends, it is expected that the glacier retreat will continue, that the mass balance will continue to show a negative trend and that thinning rates will increase. All of these changes will ultimately affect the availability of water resources in Chile that depend on glacierized basins.

Most glaciers in Patagonia are retreating rapidly. Glaciar O’Higgins, a freshwater calving glacier, has experienced the largest retreat rate of all, as measured from 1945 to 1986 (Aniya and others, 1992). Based on historical maps, early exploration reports and recent aerial photography, the front-position record of Glaciar O’Higgins is extended to cover the period 1896–1995). Climatic warming, in combination with the detaching of the glacier front from an island, is believed to be the cause of the rapid retreat.

Glaciar Pio XI (or Glaciar Brüggen) may be the only glacier in the world currently at its Neoglacial maximum. During the 20th century, most glaciers in Patagonia have consistently retreated, whereas Glaciar Pio XI has advanced almost 10 km, most recently at rates of ≤ 1.5 m d−1. This advance cannot be explained with reference to climate alone. An explanatory model combining calving dynamics, sediment budget and fjord topography explains the main features of recent behaviour. This case-study exemplifies the climatically out-of-phase behaviour so typical of calving glaciers, and illustrates the spatial and temporal scale over which they may behave asynchronously in the southern Andes.

Glacial calving is a poorly understood process. This study tests the influence of local environmental variables on the magnitude and frequency distributions of calving behaviour at Glaciar San Rafael, Chile. Near the terminus of the glacier, surface speeds average 17 m d−1in summer and calving is profuse and continual. The size, location and characteristics of over 7000 calving events were recorded during 32d in 1991 and 1992, together with meteorological, bathymetric and oceanographic data. Mean daily calving exceeds 400 events per day and the mean calving flux is more than 2 Mm3d1. Mean annual calving speed and calving flux are about 4500 m a−1and 2.0 km3a−1, respectively. This calving speed is higher than that predicted by the established empirical relationship between tide-water calving speed and water depth. This is surprising, given the low salinity of Laguna San Rafael and that fresh-water calving speeds are commonly much lower than those in ride water. Daily patterns of calving frequency and flux correlate poorly or not at all with meteorological variables, but tidal stage may have some control over the timing of large submarine calving events. Submarine calving produced the largest bergs. However, the relatively small total flux recorded from the submerged pars of the ice cliff may imply unusually rapid melt rates.

Modern geoinformatic techniques allow the automated creation of detailed glacier inventory data from glacier outlines and digital terrain models (DTMs). Once glacier entities are defined and an appropriate DTM is available, several methods exist to derive the inventory data (e.g. minimum, maximum and mean elevation; mean slope and aspect) for each glacier from digital intersection of both datasets. Compared to the former manual methods, the new grid-based statistical calculations are very fast and reproducible. The major aim of this contribution is to help in standardizing the related calculations to enhance the integrity of the Global Land Ice Monitoring from Space (GLIMS) database. The recommendations were prepared by a working group and also contribute to the European Space Agency project GlobGlacier. The document follows the former UNESCO manual for the production of the World Glacier Inventory published in 1970, identifies the potential pitfalls, and describes the differences from the former methods of compilation. The online background material for this paper (see http://www.glims.org) contains example scripts for calculation of each parameter and will be updated when required.

The energy balance of bare snow and tephra-covered ice near the glacier equilibrium line elevation on Villarrica Volcano, southern Chile, was investigated during 2004 and 2005, combining meteorological, surface temperature and ablation measurements with energy balance modelling. A tephra thermal conductivity of 0.35 Wm–1 K–1, and a critical tephra thickness of 0.1m tephra. Windblown tephra impurities lowered snow albedo, but increased snowmelt by only an estimated 0.28mw.e. over the same period. The net mass balance impact of supraglacial tephra at Villarrica Volcano is therefore positive, as thick ash and lapilli mantle most of the glacier ablation zones, probably reducing annual ablation by several metres w.e. In the accumulation seasons, frequent melting events were recorded with modelled daily snowmelt rates of up to 50 mmw.e.

Most of the glaciers in southern Chile have been retreating and shrinking during recent decades in response to atmospheric warming and decrease in precipitation. However, some glacier fluctuations are directly associated with the effusive and geothermal activity of ice-covered active volcanoes widely distributed in the region. The aim of this paper is to study the ice volumetric changes by comparing several topographic datasets. A maximum mean ice thinning rate of 0.81 ± 0.45 m a−1 was observed on the ash/debris-covered ablation area of Volcan Villarrica between 1961 and 2004, whilst on Volcan Mocho the signal-to-noise ratio was too small to yield any conclusion. An area reduction of 0.036 ±0.019 km2 a−1 since 1976 was obtained on Glaciar Mocho, while on Volcan Villarrica the area change was −0.090 ± 0.034 km2 a−1 between 1976 and 2005. Glaciers on active volcanoes are therefore shrinking, mainly in response to climatic driving factors. However, volcanic activity is affecting glaciers in two opposite ways: ash/debris advection is helping to reduce surface ablation at lower reaches by insulating the ice from solar radiation, while geothermal activity is probably enhancing melting and water production at the bedrock, resulting in negative ice-elevation changes.

The Patagonia icefields constitute a unique location in the Southern Hemisphere for obtaining non-polar paleo-records from ice cores south of 45°S. Nevertheless, no ice-core record with meaningful paleoclimate information has yet been obtained from Patagonia. This deficiency is due to extremely harsh field conditions, and to the fact that the main plateaus of both Hielo Patagónico Norte (HPN; northern Patagonia icefield) and Hielo Patagónico Sur (HPS; southern Patagonia icefield) are strongly affected by meltwater percolation. In order to explore the suitability of high-elevation glacier sites at HPS as paleoclimate archives, three shallow firn cores were retrieved covering the altitude range 1543−2300 ma.s.l. The glaciochemical records from the two lower sites confirm the presence of superimposed ice, a clear sign of meltwater formation and percolation. In the core from 2300 m, the glaciochemical signature appears to be preserved, indicating that no significant melting occurred. Although there might be problems associated with wind erosion and extreme melt events, there is good potential for well-preserved paleo-records within glaciers in the Patagonia icefields located higher than 2300 m.