Browsing by Author "Garcia, Juan Luis"

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    Spatial distribution and interannual variability of coastal fog and low clouds cover in the hyperarid Atacama Desert and implications for past and present Tillandsia landbeckii ecosystems
    (SPRINGER WIEN, 2021) del Rio, Camilo; Lobos Roco, Felipe; Latorre, Claudio; Koch, Marcus A.; Garcia, Juan Luis; Osses, Pablo; Lambert, Fabrice; Alfaro, Fernando; Siegmund, Alexander
    The hyperarid Atacama Desert coast receives scarce moisture inputs mainly from the Pacific Ocean in the form of marine advective fog. The collected moisture supports highly specialized ecosystems, where the bromeliad Tillandsia landbeckii is the dominant species. The fog and low clouds (FLCs) on which these ecosystems depend are affected in their interannual variability and spatial distribution by global phenomena, such as ENSO. Yet, there is a lack of understanding of how ENSO influences recent FLCs spatial changes and their interconnections and how these variations can affect existing Tillandsia stands. In this study, we analyze FLCs occurrence, its trends and the influence of ENSO on the interannual variations of FLCs presence by processing GOES satellite images (1995-2017). Our results show that ENSO exerts a significant influence over FLCs interannual variability in the Atacama at similar to 20 degrees S. Linear regression analyses reveal a relation between ENSO3.4 anomalies and FLCs with opposite seasonal effects depending on the ENSO phase. During summer (winter), the ENSO warm phase is associated with an increase (decrease) of the FLCs occurrence, whereas the opposite occurs during ENSO cool phases. In addition, the ONI Index explains up to similar to 50 and similar to 60% variance of the interannual FLCs presence in the T. landbeckii site during summer and winter, respectively. Finally, weak negative (positive) trends of FLCs presence are observed above (below) 1000 m a. s. l. These results have direct implications for understanding the present and past distribution of Tillandsia ecosystems under the extreme conditions characterizing our study area.
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    Stratigraphic sequence of the paleodunes and paleosols of Ventanas II in the coast of central Chile (32°) and its paleoclimatic implication
    (2023) Cabello, Misael; Garcia, Juan Luis; Quilaman, Andrea; Pfeiffer, Marco
    The coast of central Chile maintains an extensive eolian sedimentary record that has remained without much attention and has potential as a paleoenvironmental record. In the Quintero Bay (32 degrees S), Ventanas sector, extensive paleodune fields have been described with a stratigraphy that includes sand sequences intercalated with paleosols, but details on the morphogenesis and pedogenesis of these records and their paleoenvironmental evolution remain unknown. This paper aims to determine the paleogeographic and paleoenvironmental implications of the Ventanas II stratigraphic site. By applying field, laboratory, statistical, and depositional environment descriptions we recognize sedimentary facies and pedogenetic intensity. In Ventanas II site, 13 sedimentary units were identified, which we classified into four facies: paleodune, paleosol, paleowetland, and paleobeach. The lower units of the sequence correspond to a coastal wetland and beach and the upper units (Units 10 to Unit 1) to five paleosols intercalated with paleodunes, denoting a change in the paleogeography within the stratigraphic sequence. The Unit 13 towards the base of the section is a paleosol developed on reworked sediments from the Horcon Formation. The paleosols and the paleodunes suggest similar and recurrent humid and dry conditions, respectively, caused by the latitudinal oscillation of the southern westerly winds during the last glacial period in central Chile.
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    The alluvium of August 9, 2015 in Alto Patache, Tarapaca region, Atacama Desert
    (PONTIFICA UNIV CATOLICA CHILE, INST GEOGRAFIA, 2017) Orellana, Hector; Garcia, Juan Luis; Ramirez, Carla; Zanetta, Nicolas
    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 similar to 1070 m(3), which were partially stored in the distal alluvial fan, where we quantified 637 m3 of material. We estimated a mean water discharge of 11 m(3) 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 Patache embraces an overall geomorphic stability that is interrupted recurrently by debris flows linkable to ENSO variability.