Juan Luis García

Glacier expansion in southern Patagonia throughout the Antarctic cold reversal

Resolving debated climate changes in the southern middle latitudes and potential teleconnections between southern temperate and polar latitudes during the last glacial-interglacial transition is required to help understand the cause of the termination of ice ages. Outlet glaciers of the Patagonian Ice Fields are primarily sensitive to atmospheric temperature and also precipitation, thus former ice margins record the extent and timing of past climate changes. 38 10 Be exposure ages from moraines show that outlet glaciers in Torres del Paine (51°S, south Patagonia, Chile) advanced during the time of the Antarctic cold reversal (ACR; ca. 14.6– 12.8 ka), reaching a maximum extent by ~14,200 ± 560 yr ago. The evidence here indicates that the South Patagonian Ice Field was responding to late glacial climate change distinctly earlier than the onset of the European Younger Dryas stadial (ca. 12.9 ka). Major glacier recession and deglaciation in the Torres del Paine region occurred by 12.5 ka and thus early in the Younger Dryas. We provide direct evidence for extensive ice in Patagonia at the very start of the ACR that agrees with atmospheric and marine records from the Southern Ocean and Antarctica. Atmospheric conditions responsible for the early late glacial expansion at Torres del Paine resulted from a climate reorganization that prompted a northern migration of the south westerly wind belt to the latitude of Torres del Paine at the onset of the ACR chronozone.

LATE PLEISTOCENE ICE FLUCTUATIONS AND GLACIAL GEOMORPHOLOGY OF THE ARCHIPIÉLAGO DE CHILOÉ, SOUTHERN CHILE

Abstract Most of the last glacial maximum (LGM) glacier record west of the southern Andes (40–55° S) is today submerged under the Pacific Ocean and therefore the Archipiélago de Chiloé (42–43° S) provides an unusual opportunity to study local sediment and landform associations to help understand paleoglacial features of the former Patagonian ice sheet (PIS). In this context, this work presents the first comprehensive glacial geomorphologic mapping of the central region of the Archipiélago de Chiloé, which is located in a transitional geomorphic region between the Chilean Lake District (CLD, 39–41° S, 73° W) and northwest Patagonia (∼43–48° S, 74° W). The Chilotan glacial geomorphology and sediment associations resulted from a warm‐based glacier that characterizes a typical active glacial temperate landsystem, which in central Chiloé combines deposits and landform units originated in subglacial and subaerial environments. Paleoglacial features that occur in central Chiloé are characteristic of an ice‐sheet style of glaciation, which differentiates it from a typical Alpine glacial style defined previously for the CLD. Therefore, the Archipiélago de Chiloé represents a geographical break point where the PIS became the large ice mass that occupied the Patagonian Andes during the last glacial period (Llanquihue Glaciation). A double ice‐contact slope on the east face of the Cordillera de La Costa provides evidence for the most extensive Early Llanquihue glacial advance on Isla Grande de Chiloé. The most prominent LGM advance in the area occurred at 26 000 cal yr BP, coincident with regional stadial conditions, and is defined by a big moraine along the east coast of the island.

El aluvión del 9 agosto 2015 en Alto Patache, región de Tarapacá, Desierto de Atacama 1

espanolRESUMEN Durante el 9 agosto de 2015 (9A) (ano El Nino Fuerte) se produjeron lluvias torrenciales anomalas que favorecieron el desarrollo de aluviones en el Norte Grande de Chile. En la Estacion Atacama UC de Alto Patache, cordillera de la Costa de la region de Tarapaca, se registraron 51,6 mm en 6 horas, condicion que supero rapidamente el umbral de infiltra cion del suelo gatillando aluviones en las quebradas aledanas. En la cuenca de control de 7,2 Ha se cuantifico una erosion maxima de 1.070 m3 de sedimentos, parte de los cuales se depositaron en un cono aluvial de ~637 m3 de material. En la seccion inferior de la cuenca se estimo caudales medios de 11 m3 s-1. La secuencia del 9A es diferenciada en tres fases: Inicio, Peak y Termino que incluyen la dinamica meteorologica e hidrogeomorfologica conjunta. El aluvion 9A descrito en este estudio tiene precedentes en Alto Patache, donde periodos de relativa estabilidad geomorfologica son interrumpidos por lluvias intensas con alto impacto en el paisaje en respuesta al fenomeno ENSO. EnglishABSTRACT During the 09 August 2015 (strong El Nino year) heavy rains fell in the coastal Atacama Desert, including our Research Station Atacama UC_Alto Patache (cordillera de la Costa, Tarapaca Region). In this study we provide a detailed analysis of the meteorology and hydrogeomorphic response to the 51,6 mm in 6 hours of rain recorded in Alto Patache. In our control basin (7.2 Ha) we estimated a maximum erosion of ~1070 m3, which were partially stored in the distal alluvial fan, where we quantified 637 m3 of material. We es timated a mean water discharge of 11 m3 s-1 at the lower basin. The comparison between the meteorological and morphostratigraphical data allows us to define three phases that best characterize the anatomy of the 9A: Initial, Peak and End. We conclude that Alto Pa tache embraces an overall geomorphic stability that is interrupted recurrently by debris flows linkable to ENSO variability.

Lecciones y desafíos para la investigación científica en la Estación Atacama UC_Oasis de niebla Alto Patache. Conversaciones sobre desierto y niebla con Horacio Larraín y Pilar Cereceda

HL: Creo que se ha aprendido muchísimo, tanto acerca del comportamiento de la niebla misma, como de sus efectos sobre el ecosistema desértico y, también, sobre sus ricas potencialidades como recurso hídrico limpio para el futuro de la presencia humana en la zona costera. Por ejemplo, se ha aprendido la relación entre velocidad del viento y el monto de captación de agua de niebla; la importancia de la altitud sobre el nivel del mar, el valor de la gran proximidad de la línea de costa, la importancia de la presencia de “puntas” o estribaciones de montaña rocosa que penetran mar adentro, hacia el Oeste, interrumpiendo el aspecto rectilíneo de ésta y generando, en el océano, surgencias marinas; sobre el efecto e importancia de los “portezuelos”, en las partes altas de la cadena montañosa costera; y, por fin, la importancia de la existencia de sectores altos que miran directamente al Sur o Suroeste, enfrentando directamente los vientos predominantes.