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The high-altitude lakes of the Altiplano–Puna Plateau in the Central Andes commonly have large radiocarbon reservoir effects. This, combined with the general scarcity of terrestrial organic matter, makes obtaining a reliable and accurate chronological model based on radiocarbon ages a challenge. As a result, age–depth models based on radiocarbon dating are often constructed by correcting for the modern reservoir effect, but commonly without consideration of spatial and possible temporal variations of reservoir ages within the lake and across the basin. In order to get a better constraint on the spatial variability of the radiocarbon reservoir effects, we analyse 14 C ages of modern terrestrial and aquatic plants from the El Peinado basin in the southern Puna Plateau, which hosts Laguna del Peinado fed by hydrothermal springs. The oldest 14 C ages of modern samples (> 18 000 and > 26 000 BP) were found in hot springs discharging into the lake, likely resulting from the input of 14 C-depleted carbon from old groundwater and 14 C-free magmatic CO 2. In the littoral and central part of Laguna del Peinado, 14 C ages of modern samples were several thousand years younger (> 13 000 and > 12 000 BP) compared to the inflowing waters as a result of CO 2 exchange with the atmosphere. Altogether, our findings reveal a spatial variability of up to 14 000 14 C years of the modern reservoir effect between the hot springs and the northern part of the Peinado lake basin. Temporal changes of reservoir effects in sediment records are more difficult to quantify, but 14 C ages from a short core from Laguna del Peinado may suggest temporal reservoir age variations of a few thousand years. This study has implications for accurate 14 C-based chronologies for palaeoclimate studies in the Altiplano–Puna Plateau and similar settings. Our results highlight the need to consider spatial and likely also temporal variations in the reservoir effects when constructing age–depth models. [ABSTRACT FROM AUTHOR]

Given the short span of instrumental precipitation records in the South American Altiplano, longer-term hydroclimatic records are needed to understand the nature of climate variability and to improve the predictability of precipitation, a key natural resource for the socioeconomic development in the Altiplano and adjacent arid lowlands. In this region grows Polylepis tarapacana, a long-lived tree species that is very sensitive to hydroclimatic changes and has been widely used for tree-ring studies in the central and southern Altiplano. However, in the northern sector of the Peruvian and Chilean Altiplano (16–19 ∘ S) still exists a gap of high-resolution hydroclimatic data based on tree-ring records. Our study provides an overview of the temporal evolution of the late-spring–mid-summer precipitation for the period 1625–2013 CE at the northern South American Altiplano, allowing for the identification of wet or dry periods based on a regional reconstruction from three P. tarapacana chronologies. An increase in the occurrence of extreme dry events, together with a decreasing trend in the reconstructed precipitation, has been recorded since the 1970s in the northern Altiplano within the context of the last ∼4 centuries. The average precipitation over the last 17 years stands out as the driest in our 389-year reconstruction. We reveal a temporal and spatial synchrony across the Altiplano region of dry conditions since the mid-1970s. Independent tree-ring-based hydroclimate reconstructions and several paleoclimatic records based on other proxies available for the tropical Andes record this synchrony. The influence of El Niño–Southern Oscillation (ENSO) on the northern Altiplano precipitation was detected by our rainfall reconstruction that showed past drier conditions in our study region associated with ENSO warm events. The spectral properties of the rainfall reconstruction showed strong imprints of ENSO variability at decadal, sub-decadal, and inter-annual timescales, in particular from the Pacific NIÑO 3 sector. Overall, the recent reduction in precipitation in comparison with previous centuries, the increase in extreme dry events and the coupling between precipitation and ENSO variability reported by this work is essential information in the context of the growing demand for water resources in the Altiplano. This study will contribute to a better understanding of the vulnerability and resilience of the region to the projected evapotranspiration increase for the 21st century associated with global warming. [ABSTRACT FROM AUTHOR]

We investigate how evaporation changes depending on the scales in the Altiplano region of the Atacama Desert. More specifically, we focus on the temporal evolution from the climatological to the sub-diurnal scales on a high-altitude saline lake ecosystem. We analyze the evaporation trends over 70 years (1950–2020) at a high-spatial resolution. The method is based on the downscaling of 30 km ERA5 reanalysis data at hourly resolution to 0.1 km spatial resolution data, using artificial neural networks to analyze the main drivers of evaporation. To this end, we use the Penman open-water evaporation equation, modified to compensate for the energy balance non-closure and the ice cover formation on the lake during the night. Our estimation of the hourly climatology of evaporation shows a consistent agreement with eddy-covariance (EC) measurements and reveals that evaporation is controlled by different drivers depending on the time scale. At the sub-diurnal scale, mechanical turbulence is the primary driver of evaporation, and at this scale, it is not radiation-limited. At the seasonal scale, more than 70 % of the evaporation variability is explained by the radiative contribution term. At the same scale, and using a large-scale moisture tracking model, we identify the main sources of moisture to the Chilean Altiplano. In all cases, our regime of precipitation is controlled by large-scale weather patterns closely linked to climatological fluctuations. Moreover, seasonal evaporation significantly influences the saline lake surface spatial changes. From an interannual scale perspective, evaporation increased by 2.1 mmyr-1 during the entire study period, according to global temperature increases. Finally, we find that yearly evaporation depends on the El Niño–Southern Oscillation (ENSO), where warm and cool ENSO phases are associated with higher evaporation and precipitation rates, respectively. Our results show that warm ENSO phases increase evaporation rates by 15 %, whereas cold phases decrease it by 2 %. [ABSTRACT FROM AUTHOR]

The hydrologic cycle behaviour in the Bolivian Altiplano and how it interacts with human activity are still not fully understood. The hydraulic cycle is examined in a novel way in this work by considering extended time series of associated hydrologic and climatic data. Results show that human exploitation and losses from the sewage and water supply networks in the urban areas might cause an hydraulic imbalance in the region. These anthropogenic incomes, at the same time, increase concentrations of different pollutants. Water isotopic analysis reinforces the conceptual model showing that the groundwater sampled are mainly from precipitation. Workshops with local municipalities supported and defined the most relevant anthropic pressures in the basin. This information supports a vulnerability analysis in collaboration among them. The decision-making process for government entities might be strengthened by this study, which would help to develop long-term strategies to prevent and mitigate the issues found in the evaluation of water vulnerability in the region. [ABSTRACT FROM AUTHOR]

We investigate the influence of regional atmospheric circulation on the evaporation of a saline lake in the Altiplano (also known as the Andean Plateau) region of the Atacama Desert. For that, we conducted a field experiment in the Salar del Huasco (SDH) basin (135 km east of the Pacific Ocean), in November 2018. The measurements were based on surface energy balance (SEB) stations and airborne observations. Additionally, we simulate the meteorological conditions on a regional scale using the Weather Research and Forecasting Model. Our findings show two evaporation regimes: (1) a morning regime controlled by local conditions, in which SEB is dominated by the ground heat flux (∼0.5 of net radiation), very low evaporation (LvE<30 Wm-2) and wind speed <1 ms-1 ; and (2) an afternoon regime controlled by regional-scale forcing that leads to a sudden increase in wind speed (>15 ms-1) and a jump in evaporation to >500 Wm-2. While in the morning evaporation is limited by very low turbulence (u*∼0.1 ms-1), in the afternoon strong winds (u*∼0.65 ms-1) enhance mechanical turbulence, increasing evaporation. We find that the strong winds in addition to the locally available radiative energy are the principal drivers of evaporation. These winds are the result of a diurnal cyclic circulation between the Pacific Ocean and the Atacama Desert. Finally, we quantify the advection and entrainment of free-tropospheric air masses driven by boundary layer development. Our research contributes to untangling and linking local- and regional-scale processes driving evaporation across confined saline lakes in arid regions. [ABSTRACT FROM AUTHOR]

A deeper understanding of past atmospheric circulation variability in the Central Andes is a high-priority topic in paleoclimatology mainly because of the necessity to validate climate models used to predict future precipitation trends and to develop mitigation and/or adaptation strategies for future climate change scenarios in this region. Within this context, we here investigate an 18-year firn core drilled at Nevado Illimani in order to interpret its mineral dust record in relation to seasonal processes, in particular atmospheric circulation and deep convection. The core was dated by annual layer counting based on seasonal oscillations of dust, calcium, and stable isotopes. Geochemical and mineralogical data show that dust is regionally sourced in winter and summer. During austral summer (wet season), an increase in the relative proportion of giant dust particles (∅>20 µm) is observed, in association with oscillations of stable isotope records (δ D, δ18 O). It seems that at Nevado Illimani both the deposition of dust and the isotopic signature of precipitation are influenced by atmospheric deep convection, which is also related to the total amount of precipitation in the area. This hypothesis is corroborated by regional meteorological data. The interpretation of giant particle and stable isotope records suggests that downdrafts due to convective activity promote turbulent conditions capable of suspending giant particles in the vicinity of Nevado Illimani. Giant particles and stable isotopes, when considered together, can be therefore used as a new proxy for obtaining information about deep convective activity in the past. [ABSTRACT FROM AUTHOR]

This study investigates the combined hydrogen deuterium and triple oxygen isotope hydrology of the Salar del Huasco, an endorheic salt flat with shallow lakes at its centre that is located on the Altiplano Plateau, N Chile. This lacustrine system is hydrologically dynamic and complex because it receives inflow from multiple surface and groundwater sources. It undergoes seasonal flooding, followed by rapid shrinking of the water body at the prevailing arid climate with very high evaporation rates. At any given point in time, ponds, lakes, and recharge sources capture a large range of evaporation degrees. Samples taken between 2017 and 2019 show a range of δ18 O between -13.3 ‰ and 14.5 ‰, d-excess between 7 ‰ and -100 ‰, and 17 O-excess between 19 and -108 per meg. A pan evaporation experiment conducted on-site was used to derive the turbulence coefficient of the Craig–Gordon isotope evaporation model for the local wind regime. This, along with sampling of atmospheric vapour at the salar (-21.0±3.3 ‰ for δ18 O, 34±6 ‰ for d-excess and 23±9 per meg for 17 O-excess), enabled the accurate reproduction of measured ponds and lake isotope data by the Craig–Gordon model. In contrast to classic δ2 H– δ18 O studies, the 17 O-excess data not only allow one to distinguish two different types of evaporation – evaporation with and without recharge – but also to identify mixing processes between evaporated lake water and fresh flood water. Multiple generations of infiltration events can also be inferred from the triple oxygen isotope composition of inflow water, indicating mixing of sources with different evaporation histories. These processes cannot be resolved using classic δ2 H– δ18 O data alone. Adding triple oxygen isotope measurements to isotope hydrology studies may therefore significantly improve the accuracy of a lake's hydrological balance – i.e. the evaporation-to-inflow ratio (E / I) – estimated by water isotope data and application of the Craig–Gordon isotope evaporation model. [ABSTRACT FROM AUTHOR]

Modern precipitation anomalies in the Altiplano, South America, are closely linked to the strength of the South American summer monsoon (SASM), which is influenced by large-scale climate features sourced in the tropics such as the Intertropical Convergence Zone (ITCZ) and El Niño–Southern Oscillation (ENSO). However, the timing, direction, and spatial extent of precipitation changes prior to the instrumental period are still largely unknown, preventing a better understanding of the long-term drivers of the SASM and their effects over the Altiplano. Here we present a detailed pollen reconstruction from a sedimentary sequence covering the period between 4500 and 1000 cal yr BP in Lago Chungará (18 ∘ S; 4570 m a.s.l.), a high-elevation lake on the southwestern margin of the Altiplano where precipitation is delivered almost exclusively during the mature phase of the SASM over the austral summer. We distinguish three well-defined centennial-scale anomalies, with dry conditions between 4100–3300 and 1600–1000 cal yr BP and a conspicuous humid interval between 2400 and 1600 cal yr BP, which resulted from the weakening and strengthening of the SASM, respectively. Comparisons with other climate reconstructions from the Altiplano, the Atacama Desert, the tropical Andes, and the southwestern Atlantic coast reveal that – unlike modern climatological controls – past precipitation anomalies at Lago Chungará were largely decoupled from north–south shifts in the ITCZ and ENSO. A regionally coherent pattern of centennial-scale SASM variations and a significant latitudinal gradient in precipitation responses suggest the contribution of an extratropical moisture source for the SASM, with significant effects on precipitation variability in the southern Altiplano. [ABSTRACT FROM AUTHOR]

The iconic hailstorm and flash flood episode of 19 February 2002 over La Paz city is numerically investigated in this article. Large scale atmospheric circulation is dynamically downscaled in order to take into account the complex orography forcing and local features. Satellite observations suggests late morning shallow convection over the Altiplano that becomes deep convection in the early afternoon around complex orography. The control simulation captures well the cloud evolution and suggest a two-stage precipitation mechanism. First, early convection occurred around 1200 LST and originated from thermodynamic instability combined with lake breeze and orographic lifting. Rainfall discharge then generated cold pools. During the second stage, cold pools around complex orography were propagated by lake breeze and encountered the La Paz Valley breeze, triggering the deep convection near La Paz city around 1400 LST. We assess the importance of local features through numerical experiments, which include modification of orography, suppression of surface heat fluxes, changes of surface lake temperature and removal of the lake. We show the importance of orographic configuration as triggering mechanism for convection initiation and for mesoscale circulation, the role of lake temperature for frontal breeze and propagation of cold pools, and of surface heat fluxes for atmospheric instability. This study highlights the complex interaction between lakes, surface heating and orography that favour deep convection and hailstorm formation, which is especially relevant around the Titicaca lake region. [ABSTRACT FROM AUTHOR]

Remotely sensed data are often used as proxies for indirect precipitation measures over data-scarce and complex-terrain areas such as the Peruvian Andes. Although this information might be appropriate for some research requirements, the extent at which local sites could be related to such information is very limited because of the resolution of the available satellite data. Downscaling techniques are used to bridge the gap between what climate modelers (global and regional) are able to provide and what decision-makers require (local). Precipitation downscaling improves the poor local representation of satellite data and helps end-users acquire more accurate estimates of water availability. Thus, a multifractal downscaling technique complemented by a heterogeneity filter was applied to TRMM (Tropical Rainfall Measuring Mission) 3B42 gridded data (spatial resolution ~ 28 km) from the Peruvian Andean high plateau or Altiplano to generate downscaled rainfall fields that are relevant at an agricultural scale (spatial resolution ~ 1 km). [ABSTRACT FROM AUTHOR]

Throughout the second half of the 20th century, the Central Andes has experienced significant climatic and environmental changes characterized by a persistent warming trend, an increase in elevation of the 0 C isotherm, and sustained glacier shrinkage. These changes have occurred in conjunction with a steadily growing demand for water resources. Given the short span of instrumental hydroclimatic records in this region, longer time span records are needed to understand the nature of climate variability and to improve the predictability of precipitation, a key factor modulating the socio-economic development in the South American Altiplano and adjacent arid lowlands. In this study we present the first quasi-millennial, tree-ring based precipitation reconstruction for the South American Altiplano. This annual (November-October) precipitation reconstruction is based on the Polylepis tarapacana tree-ring width series and represents the closest dendroclimatological record to the Equator in South America. This high-resolution reconstruction covers the past 707 yr and provides a unique record characterizing the occurrence of extreme events and consistent oscillations in precipitation. It also allows an assessment of the spatial and temporal stabilities of the teleconnections between rainfall in the Altiplano and hemispheric forcings such as El Ni"no-Southern Oscillation. Since the 1930s to present, a persistent negative trend in precipitation has been recorded in the reconstruction, with the three driest years since 1300AD occurring in the last 70 yr. Throughout the 707 yr, the reconstruction contains a clear ENSO-like pattern at interannual to multidecadal time scales, which determines inter-hemispheric linkages between our reconstruction and other precipitation sensitive records modulated by ENSO in North America. Our reconstruction points out that centuryscale dry periods are a recurrent feature in the Altiplano climate, and that the future potential coupling of natural and anthropogenic-induced droughts may have a severe impact on socio-economic activities in the region. Water resource managers must anticipate these changes in order to adapt to future climate change, reduce vulnerability and provide water equitably to all users. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms that build orogenic plateaus requires a multifaceted view of the surface uplift history and the tectonic evolution that led to the modern lithospheric structure and the modern distribution of topography. In the Central Andean Plateau, comparison of the timing, magnitude, and distribution of shortening and surface uplift, in combination with other geologic evidence, highlights the pulsed nature of plateau growth. In particular, the crustal shortening history of the central Altiplano and Eastern Cordillera leads to estimated crustal thicknesses that exceed the modern crustal thickness, requiring the loss of crustal material by removal of dense lower lithosphere and/or crustal flow. During the late Oligocene-early Miocene in the Eastern Cordillera and late Miocene-Pliocene in the Eastern Cordillera and central Altiplano, rapid surface uplift events correspond with time periods when crustal thicknesses exceeded the modern crustal thickness. In contrast, the crustal shortening history of the northern Altiplano and Eastern Cordillera predicts thinner than modern crustal thickness, requiring crustal flow into this region, likely from the central Eastern Cordillera and Altiplano. Integrative studies of the Central Andean Plateau indicate that gradual crustal thickening and weakening of the lower lithosphere promotes pulsed surface uplift events in discrete regions associated with both convective removal of the lower lithosphere and lower crustal flow. These two processes likely work in concert, with convective removal promoting subsequent crustal flow. Lastly, we will examine an early stage of Central Andean Plateau growth and compare it to the modern architecture of other parts of the Andes, where high standing ranges bound low elevation intermontane basins, to speculate on the processes that ultimately build broad high elevation plateaus or limit mountain belt growth to narrow ranges and basins. [ABSTRACT FROM AUTHOR]

The Chacaltaya GAW Station (16.3505ºS, 68.1314ºW, 5240 masl) was established in December of 2011 with a set of instruments for monitoring atmospheric composition; mainly aerosol physical and chemical properties as well as concentration of greenhouse and reactive gases. The station is located on the eastern flank of the Andes Mountains near the center of South America, close to the Amazon rain forest and the highest plateau in South America, the Altiplano, at 3800 m asl. Due to its strategic location, air masses arriving from the Amazon, the Altiplano, the Pacific Ocean and the metropolitan area of La Paz/El Alto, the largest city complex in the region, are sampled regularly at the station. The daily behaviors of both aerosol and gas concentration are strongly influenced by the planetary boundary layer (PBL). A clear signal of aerosols arriving from the metropolitan area (about 1200 m below the station) is frequently measured late in the morning under the right meteorological conditions. The complex topography of the region produces complicated patterns of air mass transport and several atmospheric layers in the surrounding region. In spite of this, very different conditions characterize day and night aerosol and gas concentrations. Turbulent conditions are typically observed during daytime whereas stable conditions, characteristic of the free troposphere, are present at nighttime. However, relatively large values of aerosol concentration in the free troposphere are measured at night. In addition, long range transport of aerosols is clearly discernible in the data especially during the biomass burning season, which occurs in the transition period between the dry and wet seasons in August and September. Results from the continuous measurements at Chacaltaya and from two campaigns in the metropolitan are discussed in this work. [ABSTRACT FROM AUTHOR]

The distribution and characteristics of the Cenozoic alluvial and fluvio-alluvial deposits in the Coastal Cordillera and the Coastal Plain in northern Chile reflect the paleo-climatic conditions in this area. Here, pre-Upper Oligocene fluvio-alluvial rocks (Cañón del Loa Beds, CLB) have been recognized in the canyon walls of the Loa River and adjacent pampa, Oligocene-Pliocene alluvial deposits (Alto Hospicio Gravels, AHG) are broadly distributed in the Coastal Cordillera, and more restricted Pleistocene-Holocene alluvial deposits (PHAD) crop out in the Coastal Cordillera and Coastal Plain. The components of the Cenozoic alluvial units are derived from erosion of the basement units that crop out in the Coastal Cordillera.The CLB have an exposed surface area of ca. 24.2 km2 in the studied area, and are localized near the canyon of the Loa River, where they unconformably cover the Paleozoic-Mesozoic basement. This unit has a maximum thickness of 300 m and consists of conglomerates with rounded to well-rounded clasts and minor intercalated sandstones. This unit was deposited syntectonically in hemigrabens limited by NNW-SSE to NNE-SSW striking normal faults linked to the Atacama Fault System. In the top of this unit, there is a gypsic soil, indicating an important hiatus in sedimentation.The AHG have a broad distribution and cover ca. 3412 km2 of surface in the studied area. This unit consists of a sequence of gravels with minor volcanic ashes and evaporitic layers. Radiometric ages (K-Ar and 40Ar/39Ar) vary between 24.7 and 2.7 Ma. These deposits have a maximum thickness of 200 m, and accumulated in N-S oriented structural basins.The PHAD have an area of 209 km2 in the Coastal Cordillera and 37 km2 in the Coastal Plain. They consist of unconsolidated angular sand and gravels, with local intercalations of volcanic ash. This unit has few centimeters to 1 m thick. It is highlighted that in the Coastal Plain these deposits are confined to the southern part of the studied area, suggesting a latitudinal climatic segmentation.In general terms, the lithological characteristics and distribution of the CLB suggest that they were deposited under semi-arid paleoclimatic conditions. This setting could be a result of a local climatic condition or to a latitudinal climatic segmentation. The AHG have characteristics that indicate an intensification of arid conditions, and their broad distribution shows that the paleoclimatic condition affected an extensive swath of the Coastal Cordillera of northern Chile. The PHAD have a smaller areal distribution and relative thickness that suggest deposition during hyperarid climatic conditions. In summary, the alluvial record of the Coastal Cordillera shows a gradual increase in aridity in the climatic conditions through time.It is important to emphasize that the alluvial deposits of the Coastal Cordillera are a more accurate register of its local climatic conditions, whereas the extensive alluvial deposits in the Pampa del Tamarugal and the western Precordillera are a product of the prevailing climatic conditions that characterize the Altiplano situated far away from the Coastal Cordillera.This work is part of the National Mapping Program of the SERNAGEOMIN (Chile). [ABSTRACT FROM AUTHOR]

Chilean Central Andes has been subjected to different long-period magnetotelluric surveys since the 80's. And even though it's been 40 years since those early studies there are still many places to get covered. Extreme heights, lack of proper access, long lasting records and difficult electrical contacts are amongst the problems.The mission of the INSUD group of the Geophysics Department of the University of Chile is to comprehend the relationship between the subduction process and natural disasters. In this context, a magnetotelluric survey was deployed at 23°S in the Chilean Andes. The 180 km long profile goes through the Domeyko Range, Salar de Atacama basin, Western Cordillera and Puna. Western Cordillera coincides with the actual volcanic arc, comprised in the Central Volcanic Zone. It's worth to mention that the arc has an eastward shift of its position at this latitude and includes one of most active volcanoes in Chile, the Lascar volcano.The array comprises 14 long-period stations separated by 10 km and 6 broadband stations in between long-period stations located in the Puna and Western Cordillera. Preliminary dimensional analysis shows a 2D structure for long periods with an almost N-S geoelectric strike. It remarkably coincides with the geological strike of the main morphostructural features and structural systems. With that in mind, 2D inversionsare executed using WinGlink software. A large conductive anomaly shows up in every inversion at the easternmost end of the cross-section. It may be related with similar anomalies shown in MT studies north of this region which have been interpreted as the Altiplano – Puna Magma Body. This interpretation is also supported by the fact that superficial manifestations of the Altiplano – Puna Volcanic Complex are common at the study area. Some examples are the La Pacana caldera, Puricó Volcanic Complex and the widespread of Neogene ignimbrite sheets. A 3D inversion is also performed with the addition of previously measured data. [ABSTRACT FROM AUTHOR]

The removal/foundering of the continental lithosphere has been put forward to explain varying volumes of melt production derived from sublithospheric/asthenospheric mantle (e.g mafic magmatism) on Earth, and potentially on other planets. Based on the distribution of OIB-type (Ocean Island Basalts, non-subduction related) volcanics, delamination or convective removal mechanisms have been suggested to occur below the Puna-Altiplano plateau (central Andes back-arc). Recently, pyroxenite and peridodite melts, were used to approximate the amount of melting and the temperature constraints in relation to the mantle drip magmatism under the Puna region. In accord with geological-petrological interpretations, seismic tomography images, re in favour of lithospheric removal/drip/delamination (although the style is not agreed upon). In this work, we explore magma/melt types and amounts by using petrological-thermomechanical numerical models of mantle drip/convective removal. In the experiments, we calculate the volumetric melt production of dry and wet (hydrous) melting in the models. The dry (decompression) melting is an approximation of the mafic magmatism following the removal of the lithospheric drip migrating under the crust, whereas the hydrous melting is an approximation to the devolatilize melt produced by pinching off of the dripping viscous lithosphere. We conduct two series of experiments, with delamination, and with convective removal. We analyze melting temperature increase and melt production in these series, to compare with the short timescale signals from the Puna plateau. Our first of models use the small-scale removal (50 km diameter) and the second set of models consider larger volumes of melt production due to the convective removal. We specifically compare our results to see if the melting temperature increase over relatively short timescale (1 - 2 myrs) as suggested for the Puna plateau. [ABSTRACT FROM AUTHOR]

Geological and climatological events had a particularly great impact on the evolution of life in extremely water limited environments, such as the Atacama Desert in northern Chile. The evolutionary history in this region has been poorly studied. Within the CRC 1211 (Earth - Evolution at the dry limit), we focus on the evolution of darkling beetles of the genus Psectrascelis. These beetles belong to the most conspicuous biotic components in Altiplano (or Puna) and represent a hyperdiverse genus with small areas of distribution. To elucidate the evolutionary pattern we analyzed genetic markers and additionally analyzed, by MALDI-TOF mass fingerprinting, the structural diversity of neuropeptides. The phylogenetics results suggest a deep separation between westen and eastern lineages about 4,5 Myrs ago, during the Pliocene. Then a secondary split by the colonization of the Puna and Prepuna region occurred about 3 Myrs ago and separated the coquimbean lineage from the Puna-Prepuna lineages. Finally, the Puna lineage with three species colonized the Altiplano in the last 700 kyrs from the prepuna region in the south. The other two species from the eastern lineage colonized the Altiplano in a completely independent history just in the last 200 Kyrs. The evolution of Psectrascelis in the Altiplano shows a complex history related with uplift of the Andes and climatological changes in the Plio-Pleistocene periods. [ABSTRACT FROM AUTHOR]

The Pampa del Tamarugal (PdT; ~19º30'S-21º30'S) is an endorheic basin located today at the core of the Atacama Desert (northern Chile), the most arid desert on earth. Water, a fundamental resource for survival of humans, animals and plants, is a scarce resource in the PdT landscape given that precipitation fall upslope over the Andes and the Altiplano and perennial springs infiltrate in the foothills before reaching this basin. However, discontinue human occupations in the since 13ka and the presence extinct fauna dated 18-14ka southernmost part of the PdT, revealed the presence of water in the past under a highly environmental variability. It is widely known that two pluvial phases occurred in the Atacama Desert (CAPE I-II) and the Altiplano (Tauca and Coipasa phases) during the Late Pleistocene characterized by significant increases of rainfall amount and the consequent environmental changes. However, palaeoecological evidence that allowed to understand the environmental scenarios that supported human populations and extinct fauna in the PdT since and/or during the Late Pleistocene is scarce and fragmentary. Thus, this paper presents new palaeoecological evidences from the PdT in order to shed light to the environmental dynamics and landscape characteristics.Between the Guatacondo and Tambillos ravines, growing evidence shows different features of past landscapes and human activities. Thus, plant macro-remains as leaf litter packs, trunks in horizontal position, in situ bases of trunks, plant stem imprints as well as different sedimentary deposits revealed the presence of paleosprings, paleowetlands and small shallow lacustrine basins during the Late Pleistocene. In Quebrada Maní, for example, large paleowetlands developed until 11ka. Instead, the preserved vegetal macro-remains showed a peculiar spatial pattern of vegetation during that period where Prosopis trunks are more frequent in lowlands (~850 m asl) of PdT while the macro-remains, mainly of Escallonia, are abundant near to the foothill (~1150 masl). Later on, during the early and mid-Holocene, an abrupt decrease in rainfall in the Central Andes generated hiperarid conditions in PdT and consequently, no evidence of human populations was found. Sedimentological observations and OSL dates suggest the development of arid landscapes in the Guatacondo ravine (21ºS) by this time, dating the incision of the ravine sometime between 6.6-1.3ka.After that, a new humid pulse during the Late Holocene (2.5-1ka), associated with new human occupations in PdT characterized by the development of villages and wide field-crops occurred. This period of intensive cultural development and "re-use" of the PdT ended around 1-0.7ka, following a trend to aridization recorded in the rodent middens pollen record. After that the villages of PdT were abandoned and population moved to villages located at higher altitude or associated with water oases active until the present. Around 100-150 yr BP, a brief humid pulse in the PdT occurred synchronously with the reoccupation of the field-crops but probably just seasonally.Acknowledgments: FONDECYT# 1181829; CONICYT/PIA ANILLO SOC1405. [ABSTRACT FROM AUTHOR]

The South American Altiplano is a high-level plateau (around 4000m) situated in the centralAndes between 15˚S and 22˚S. The rainfall in the Southern Hemisphere (SH) summer (December – January) is nearly the only water resource for the population and the agriculture. The Climandes project, a development project between MeteoSwiss and the Peruvian National Service of Meteorology and Hydrology (SENAMHI) aims at providing climate services for this region, among them seasonal forecasts which can greatly help for the planning of agricultural activities. However, the complex topography of the Andes poses a severe challenge for models to predict local climate especially precipitation. We aim to explore whether large scale patterns are better represented in the models and could be used to improve seasonal forecast products for the region. For this we first derived the statistical relationships between the atmospheric patterns and local precipitation using large-scale fields and trajectories calculated from ERA-interim data and observational data from SENAMHI. First results of the trajectory analysis show three distinct hotspots of moisture uptake leading to precipitation in the region. In agreement with previous studies we found that geopotential height and the wind field at 200hPa are the main influencing factors.A first index based on the geopotential height at 200hPa shows good correlations with precipitation data from stations on the Altiplano and can be represented reasonably well by the ECMWF seasonal forecast model. [ABSTRACT FROM AUTHOR]