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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.

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.

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.