Glacier Clusters identification across Chilean Andes using Topo-Climatic variables

<p>This study presents a glacier clustering for the Chilean Andes (17.6-55.4°S) realized with the Partitioning Around Medoids (PAM) algorithm and using topographic and climatic variables over the 1980-2019 period. We classified ~24,000 glaciers inside thirteen different clusters (C1 to C13). These clusters show specific conditions in terms of annual and monthly amounts of precipitation, temperature, and solar radiation. In the Northern part of Chile, the Dry Andes (17-36°S) gather five clusters (C1-C5) that display mean annual precipitation and temperature differences up to 400 mm/yr and 8°C, respectively, and a mean elevation difference reaching 1800 m between glaciers in C1 and C5 clusters. In the Wet Andes (36-56°S) the highest differences were observed at the Southern Patagonia Icefield (50°S), with mean annual values for precipitation above 3700 mm/yr (C12, maritime conditions) and below 1000 mm/yr in the east of Southern Patagonia Icefield (C10), and with a difference in mean annual temperature near 4°C and mean elevation contrast of 500 m.</p><p>This classification confirms that Chilean glaciers cannot be grouped only latitudinally as it has been commonly considered, hence contributing to a better understanding of recent glacier volume changes at regional and watershed scales. An example of this was observed in the Maipo watershed (33°S), where the Echaurren Norte glacier is located, which is the reference glacier for Chile and WGMS because it has the oldest time series of mass balance monitoring in the Andes, followed by the Piloto Este glacier, since the 70's. Indeed, we identified that Echaurren Norte glacier only has similarities with 5% of the glacierized surface area of the Maipo watershed. Echaurren Norte glacier is within a glacier cluster that presents warmer and wetter climate conditions (3.1°C, 574 mm/yr) than the average of the watershed, a cluster that contains also 68% of the glacierized surface composed of rock glaciers.</p>

The first soil moisture reconstruction in the Mediterranean Chilean Andes region developed by tree rings and satellite observations to inform climate change impacts in South America

<p>Soil moisture (SM) is a key variable in the earth surface dynamics; however, long-term in situ measurements at the global scale are scarce. In the Mediterranean Chilean Andes (MA; 30°-37°S), Sclerophyllous Forest tree species such as Belloto del Norte (BN; <em>Beilschmiedia miersii</em>) can grow for more than two centuries in very scarce humid lowland geographical zones. At the present work, we assess the linkages between two BN tree-ring chronologies (BML and AGU sites; 70 cores) and daily high-resolution satellite-based surface soil moisture product v201812.0 from ESA and to reconstruct past SM variations in the MA region. Our findings exhibit strong relationships between tree-growth from BML and AGU sites and the SM from 32°-34°S and 71°-73°W spatial domain, especially from February to September. We found significant r Pearson correlations of 0.85 and 0.68 during 1983-2014 (<em>P</em>-value < 0.001), respectively. Based on these results, we reconstructed the SM between 1800 - 2014 period using multiple linear regression. Our model retains 71.4% of the total variance and exhibits an unprecedented SM reduction since 2006 in the context of the past two centuries. This work constitutes the first reconstruction of surface soil moisture variability derived from remote sensing carried out in Chile, and can provide new information to understand current environmental changes related to the severe mega-drought period experienced in  Chile since 2010, which has provoked water conflicts, the Sclerophyllous Forest decline and browning, and the intensification of climate extreme events such as heatwaves and wildfires in the MA. </p><p>Acknowledgments</p><p>Álvaro González-Reyes wish to thank: ANID+PAI+CONVOCATORIA NACIONAL SUBVENCIÓN A INSTALACIÓN EN LA ACADEMIA CONVOCATORIA AÑO 2019 + PAI77190101. Ariel Muñoz and Isadora Schneider thanks to the FONDECYT 1201714 and the Center for Climate and Resilience Research (CR)2, FONDAP 15110009.   </p>

Comment on “Crustal faults in the Chilean Andes: geological constraints and seismic potential” by Santibáñez et al. (2019), Andean Geology 46 (1): 32-65

Understanding the location and nature of Quaternary active crustal faults is critical to reduce both the impact of fault rupture and strong ground motions hazards (when these faults rupture causing earthquakes). It is also important for understanding how and where deformation related to plate tectonics is accommodated along geological structures (oftentimes faults and folds). In Chile, work on active tectonics in the upper crust (neotectonics or earthquake geology) is relatively new, in particular regarding fault-focused studies. Therefore, any effort to further progress in our understanding of active fault systems for the benefit of the public, and for aiding local and regional governments and the earthquake engineering and scientific community with mitigation strategies should be applauded. Demonstrating where active faults are located through careful mapping, and to determine how fast they accommodate tectonic deformation and their seismic and fault rupture hazards are key questions in neotectonics. Recently Santibáñez et al. (2019) explore active fault systems in the Chilean Andes. In their paper they outline active and potentially seismogenic (i.e., earthquake producing) fault systems in the Chilean Andes through a review of the literature, seismicity, case studies (earthquakes), and modeling data and then they define potential tectonic domains for subdivision of Chile. These domains were suggested to allow “a first-order approach for seismic potential assessment” (Santibáñez et al., 2019). The three subdivisions they suggest, i.e., domains are the External Forearc, Inner Forearc and Volcanic Arc, were proposed based on several fault parameters (e.g., fault length), case studies, the morphotectonic setting and seismicity. Their paper generates a great foundation to build upon for both the active tectonics and geological hazards community, in addition to being useful for potential end users such as the Chilean local and national government from a planning perspective. Although the Santibáñez et al. (2019) paper takes steps in the right direction, and should be considered an important contribution to the scientific community, this comment addresses three potential issues with their analysis and conclusions that should be reflected upon by the seismic hazard and active tectonics community. These ideas are summarized below and expanded on in detail thereafter.