Claudio Bravo

Glaciar Jorge Montt (Chilean Patagonia) dynamics derived from photos obtained by fixed cameras and satellite image feature tracking

Abstract 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.

Recent ice-surface-elevation changes of Fleming Glacier in response to the removal of the Wordie Ice Shelf, Antarctic Peninsula

Abstract 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.

First Glacier Inventory and Recent Changes in Glacier Area in the Monte San Lorenzo Region (47°S), Southern Patagonian Andes, South America

Abstract We present the first glacier inventory of the Monte San Lorenzo region (47°35′S, 72°18′W) in the southern Patagonian Andes of Chile and Argentina. This region contains the largest and easternmost glaciers at these latitudes in South America. The inventory was developed using a combination of ASTER and Landsat ETM + scenes from 2005 and 2008, respectively, and a semi-automatic band ratio approach to map glacier ice. Manual corrections were applied to include debris-covered ice and ice in cast shadows. We inventoried 213 glaciers that cover a 2005/2008 total area of ca. 207 km2 and lie between 520 m and 3700 m in elevation. Landsat TM images acquired in 1985 and 2000 were subsequently used to assess changes in glacierized area over the 1985–2008 interval. Based on all available information, we determined an 18.6% reduction in the total glacier area since 1985. Glaciers smaller than 1 km2 have shown highly variable (0–100%) relative areal reduction, whereas the formation and growth of proglacial lakes promoted rapid recession of the larger valley glaciers, which concentrate the major ice losses, representing ca. 32% of the total glacier area reduction. Glacier fragmentation has occurred for 50% of the ice bodies larger than 1 km2. These results agree with the generalized pattern of glacier retreat observed throughout the Patagonian Andes, but the lack of detailed meteorological and glaciological data in the area preclude a more refined analysis of the climate-glacier relationships and processes explaining the recent glacier trends.

First Glacier Inventory and Recent Glacier Variation on Isla Grande de Tierra Del Fuego and Adjacent Islands in Southern Chile

The first glacier inventory of the islands south of the Estrecho de Magallanes including Isla Grande de Tierra del Fuego, Isla Santa Ines, and Isla Hoste, has been compiled using several ASTER and Landsat ETM+ satellite images acquired between 2001 and 2011, yielding a total glacier cover of 3,289.5 km2, distributed among 1,681 glaciers. Previous estimations of total glaciated area for these islands amounted to only 2,500 km2, the difference being attributed to more precise glacier delimitation—not to glacier advance. Most glacier tongues analyzed from recent remotely sensed imagery have been compared with historical data, with a number of glaciers showing retreat in recent decades, especially on the northern side of Cordillera Darwin and at Monte Sarmiento, both located on Isla Grande de Tierra del Fuego. Within the survey area of interest, Glaciar Marinelli showed the greatest change, with a frontal retreat of 15 km between 1913 and 2011. Many other glacier fronts have been stable, with only minor changes since the first historical accounts. Only two glaciers, located at the southern edge of Cordillera Darwin, have shown advances in the last decade; namely, Glaciar Garibaldi (+1.1 km between 2001 and 2007) and an unnamed glacier calving into Bahia Pia (+0.6 km between 1991 and 2004). These advancing glaciers seem to be responding to calving oscillations and not necessarily to the current climatic trend in the region of atmospheric warming and less precipitation.

Recent glacier changes in southern Chile and in the Antartic Peninsula

Se presenta una sintesis de la investigacion glaciologica reciente realizada por el Centro de Estudios Cientificos, CECS, en Chile y la Peninsula Antartica mediante el uso de una variedad de metodologias modernas, con el fin de detectar las tendencias de cambio experimentadas por los glaciares en las ultimas decadas.