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This study focuses on Patagonia, where Foehn events observed in the lee of the Andes mountains are not yet well simulated by state‐of‐the‐art climate models. It has been agreed that one source of this shortcoming is related to the poor relief representation in models. To resolve this need, a common method used is to enhance the spatial resolution of the model to retrieve a more complex surface elevation, at the expense of calculation time or surface area covered. This paper tackles the problem from a different angle by addressing the Digital Elevation Model (DEM) generalization, that is, the altitudes generalization from a high‐resolution DEM to a coarser resolution grid model. Most current climate models use DEM generalization methods that smooth the relief, a key controlling factor in Foehn events modelling. The aim of this study is to compare three original methods of DEM generalization (percentile 90 [P90], envelope maximum [EM], and thalweg and crests [TC]) and to evaluate their impact on simulated precipitation and temperature fields on the eastern part of Patagonia, where warm and dry air masses are expected. Thanks to MAR, a Regional Climate Model, we validate the models at 10 and 5 km resolutions against the Climate Research Unit and perform three sensitivity experiments involving a change in the DEM generalization. Our results show that (a) a finer spatial resolution can slightly improve the temperature biases, however, it cannot resolve the precipitation biases and (b) a more appropriate use of DEM generalization induces a significant decrease in precipitation for the P90 and EM methods and an increase in mean temperature for all three methods in the study area. This study serves as a recommendation for a better use of DEM generalization in climate models performing in Patagonia, but also regions sharing the same orographic features as the Patagonian relief. [ABSTRACT FROM AUTHOR]

Drylines have been identified as relevant synoptic-scale phenomena that frequently occur in several regions around the world. Despite previous works and the experience of local forecasters that recognizes the occurrence of drylines in Argentina and suggests its possible association with convection initiation, knowledge about the mechanisms leading to the genesis of these features is poor. This paper presents the first synoptic climatology of these drylines as well as a first approach to the understanding of the processes leading to their formation. The climatology is based on an automated algorithm for dryline identification applied to reanalysis data. We found that drylines are more frequent between the northern Patagonia plateau and the central Argentinean plains. A composite analysis is performed to analyze the processes leading to the formation of synoptic-scale drylines within this region. It was found that these drylines form in the confluence between a warm and moist air mass driven by a northwesterly flow and drier air flowing east over the northern Patagonia plateau. The dry air originates on top of the Pacific maritime boundary layer and experiences lee subsidence after crossing the Andes range creating an area of dry and warm air that is advected to the east by the westerly synoptic-scale flow, and transported downward during the day due to strong boundary layer turbulence. At the same time, surface heating over the plateau leads to substantial warming of the originally colder dry air behind the dryline, thus reversing the horizontal temperature gradient across the dryline. [ABSTRACT FROM AUTHOR]

The aim of this study is to assess the variability of the stable carbon and nitrogen isotope composition of herbivores -guanaco and huemul-in southern Patagonia. The study area extends from the eastern slopes of the Andes to the Atlantic Coast between 47° and 49° S. The ultimate aim of the research was to generate an isotopic ecology with an adequate spatial resolution that allows the incorporation and development of stable isotope studies in discussions of the population dynamics of hunter-gatherers in continental Patagonia. This paper presents the δ13C and δ15N values of 159 guanaco and huemul specimens, both modern and archaeological. This space was divided into three areas: Western area, Central Plateau and Eastern Area. Isotopic variability within groups was analyzed using the SIBER, from which the isotopic niches of the different groups are compared. The results show a spatial pattern of isotopic variability in herbivores, i.e. lower δ13C and δ15N values associated with forest environments in the western end of the transect and higher values, especially δ15N, towards the east, with maximum values observed near the Atlantic coast. Our results support the stated expectations on herbivore stable isotope composition variability and its association with environmental variables in a longitudinal transect across the southern Argentinean Patagonia. [ABSTRACT FROM AUTHOR]

Recent airborne pollen records data from Northern Patagonia (San Carlos de Bariloche, Argentina, Lat. 41.1435° S, Long. 71.375°W, 800m elevation) suggest that pollen transport takes place from the west to the east slope of the Andes. However, the atmospheric characteristics responsible of this transport have not yet been studied. The aim of this paper is to assess potential source areas and to describe the involved atmospheric mechanisms of the trans- Andean pollen transport. Methodology relies on the analysis of backward trajectories of air masses calculated with the HYSPLIT 4.9 regional model for particular days where airborne pollen of Weinmannia trichosperma Cav. was detected east of the Andes. This pollen type was selected because it is found regularly at localities in eastern Patagonia beyond its present-day distribution. Weinmannia's substantial presence during early Holocene times would also benefit from better knowledge of its transport mechanisms. Correspondence between atmospheric trajectories and the position of sources was checked using GIS maps. Mode T, Principal Component Analysis (PCA) with Varimax rotation was used to identify the main spatial structure of geopotential height anomalies producing the calculated trajectories. Eighty-eight cases showed that the calculated directions of trajectories trended from the Northwest to Southwest passing over the Chilean region of W. trichosperma distribution. PCs results showed two patterns of negative anomalies over southern Patagonia. The prevailing circulation pattern which drives airborne transport is the presence of a trough located south of 37 to 40° S with its axis over western Patagonia. The synoptic situations for two cases highly correlated with principal component scores were described. [ABSTRACT FROM AUTHOR]

• Maize consumption record from the northeast Patagonia is presented. • Archaeobotanical data is discussed with the oxygen isotopes (δ18O) on human remains. • Maize-consumers were local individuals who also consumed local wild plants. • Maize would have entered through exchange, probably from southern Andes. This paper discusses the maize consumption record among hunter-gatherers outside assumed production areas in northeastern Patagonia. We evaluated if this anomalous record is the result of occasional events of local production/consumption; the transport of the microremains in the teeth of individuals after consuming maize in non-local production areas; or the local consumption of maize after its transport/exchange from production areas. Archaeobotanical results showed that analyzed individuals, including maize-consumers, mainly consumed local wild plants. Maize was not cultivated locally, and its consumption was unusual but not extraordinary in northeastern Patagonia. Oxygen isotope values of analyzed individuals are strongly compatible with local water sources, which imply that the mobility range of them must have not exceeded extra-Andean North Patagonia. For this reason, the most plausible explanation for the presence of maize in the local archaeological record is that this plant to have entered northeastern Patagonia through exchange, probably from southern Andes (central Chile or central-west Argentina). [ABSTRACT FROM AUTHOR]

The hinterland zone of the North Patagonian Andes between 41° and 43°S constitutes a poorly explored sector of the Andes, where no structural studies and scarce geochronological determinations have been carried out. This paper focuses on two isolated volcanic sections hosted at the main Andes, in which field evidence indicates a common synextensional origin. Geochronological data establish that this volcanic event occurred diachronously at the innermost sector of the evolving fold and thrust belt, during middle to late Miocene times. Therefore, the event was briefly coeval and postdated compressive tectonics recognized in the deformational front and correlative to the last phase of pluton emplacement of the North Patagonian Batholith. Local-scale topographic swath profiles performed in this work reveal negative topographic anomalies where normal faults were recognized. Moreover, regional swath profiles show not only a conspicuous depressed zone at the hinterland zone, where the studied sections are located, but also anomalously high altitudes at the foreland zone. In addition, calculated orogenic volumes increase in this sector of the fold and thrust belt, which agrees with recent shortening estimations. These topographic along-strike variations, in association with late Miocene extension following the main compressive stage in the area, are explained by a supercritical stage of the orogenic wedge that would have led to focused extension at the innermost sector of the fold and thrust belt. [ABSTRACT FROM AUTHOR]

The Last Glacial Termination (T1) featured major changes in global circulation systems that led to a shift from glacial to interglacial climate. While polar ice cores attest to an antiphased thermal pattern at millennial timescales, recent well-dated moraine records from both hemispheres suggest in-phase fluctuations in glaciers through T1, which is inconsistent with the bipolar see-saw paradigm. Here, we present a glacier chronology based on 30 new 10Be surface exposure ages from well-preserved moraines in the Lago Palena/General Vintter basin in northern Patagonia (~ 44°S). We find that the main glacier lobe underwent profound retreat after 19.7 ± 0.7 ka. This recessional trend led to the individualization of the Cerro Riñón glacier by ~ 16.3 ka, which underwent minor readvances at 15.9 ± 0.5 ka during Heinrich Stadial 1, during the Antarctic Cold Reversal with successive maxima at 13.5 ± 0.4, 13.1 ± 0.4, and 13.1 ± 0.5 ka, and a minor culmination at 12.5 ± 0.4 ka during Younger Dryas time. We conclude that fluctuations of Patagonian glaciers during T1 were controlled primarily by climate anomalies brought by shifts in the Southern Westerly Winds (SWW) locus. We posit that the global covariation of mountain glaciers during T1 was linked to variations in atmospheric CO2 (atmCO2) promoted by the interplay of the SWW-Southern Ocean system at millennial timescales. [ABSTRACT FROM AUTHOR]

We describe the stratigraphy, age, geochemistry and correlation of tephra from west to east across the northern Patagonian Andes (c. 40–41°S) with a view to further refining the eruptive history of this region back to the onset of the Last Glacial Termination (~18 cal. ka). Eastwards across the Andes, rhyodacite to rhyolitic tephra markers of dominantly Puyehue‐Cordón Caulle source are persistently recognised and provide a stratigraphic context for more numerously erupted intervening tephra of basalt to basaltic–andesite composition. Tephra from distal eruptive centres are also recognised. West of the Andean Cordillera, organic‐rich cores from a small closed lake basin (Lago Pichilafquén) reveal an exceptional high‐resolution record of lowland vegetation–climate change and eruptive activity spanning the last 15 400 years. Three new rhyodacite tephra (BT6‐T1, ‐T2 and ‐T4) identified near the base of the Pichilafquén record, spanning 13.2 to 13.9 cal. ka bp, can be geochemically matched with correlatives in basal andic soil sequences closely overlying regolith and/or basement rock. The repetitiveness of this tephrostratigraphy across this Andean transect suggests near‐synchronous tephra accretion and onset of up‐building soil formation under more stable (revegetating) ground‐surface conditions following rapid piedmont deglaciation on both sides of the Cordillera by at least ~14 cal. ka bp. [ABSTRACT FROM AUTHOR]

The middle atmosphere over South America, particularly above the Andes mountain range, is known as one of the most dynamically active regions in the world. Previous studies have investigated wave dynamics at mesosphere and lower thermosphere (MLT) altitudes within this region, but only a handful of them have made use of continuous measurements provided by specular meteor radars (SMRs). Furthermore, it was only until recently that MLT horizontal wind gradients were estimated for the first time using Spread Spectrum Interferometric Multistatic meteor radar Observing Network (SIMONe) Argentina, a multistatic SMR network located in southern Patagonia. By observing larger amounts of meteors from different viewing angles, multistatic SMRs allow, among others, for more reliable momentum flux estimates. In this work, we explore and compare the summer and winter MLT momentum flux dynamics at low and middle latitude sectors over the Andes mountain range. We also investigate the intermittency of the total momentum flux over these sectors. For this purpose, we analyze measurements provided by four multistatic SMR networks: SIMONe Peru (12°S), Chilean observation network de Meteor radars (30°S), SIMONe Argentina (49°S) and multi‐frequency Agile radar for investigations of the atmosphere‐southern Argentina agile meteor radar (54°S). We find that the momentum flux dynamics can change considerably over distances of only a few hundred km (e.g., southern Argentina). On the other hand, the contributions of large momentum fluxes to the total flux can be similar between regions separated by thousands of km (e.g., between Peru and southern Argentina). Key Points: First latitudinal comparison of mesosphere and lower thermosphere momentum fluxes along the Andes mountain range28‐day mean momentum flux dynamics vary depending on the latitude and the seasonTotal momentum flux distributions are well represented by log‐normal functions, with parameters varying on location and season [ABSTRACT FROM AUTHOR]

Abstract: The structure and tectonics of the retro-arc area of the Andes between 38°30′ and 40°S remains poorly understood because of the scarcity of previous structural studies. This paper analyzes the styles, distribution and timing of the deformation in the eastern flank of the Andes between these latitudes, with focus in the Tertiary tectonics of the area. This Andean section can be divided into an internal and an external domain based on its distinctive structural evolution. The boundary between them coincides with the Bio Bio and Aluminé valleys, which separate sectors of the fold-and-thrust belt with opposite vergence and different structural styles. Structures developed in the external domain during the Andean cycle are associated with a west-verging fold-and-thrust belt which was controlled geometrically by pre-existing normal faults of the Mesozoic rift phase. We also differentiate three segments along the external domain of the inner retro-arc zone at these latitudes. Each segment is associated with a Tertiary depocenter related to the western border of a structural high (Copahue–Pino Hachado Block and Cordilleras de Catan Lil and Chachil) which constitutes an outstanding feature within the study area. The recognition and interpretation of the main structures and the spatial and temporal distribution of the Tertiary sequences allowed us to establish a tectonic model in which the uplift of this NNW-trending block during upper Miocene times, originated a series of intermontane depocenters well represented between 38 and 40°S. As a result of that, syntectonic and synorogenic deposits accumulated in a compressive regime. These depocenters can be integrated in a narrow deposition zone associated with the western slope of the Copahue–Pino Hachado Block and its southward prolongation in the Cordillera de Catan Lil and Cordillera del Chachil. On the basis of tectonostratigraphic controls we define the last Andean contractional phase of the inner retro-arc area at these latitudes, between 11 and 5.67Ma for the northern segment, between 10 and 6.2Ma for the central segment and between 13 to 8 and 4.3Ma for the southern segment. After this short-lived compressional stage, deformation migrated to the west associated with the onset of the Liquiñe-Ofqui strike-slip fault zone along the intra-arc zone. [Copyright &y& Elsevier]

Abstract: This paper evaluates the chronology of the last glacial cycle and deglaciation in the Lago Pueyrredón valley of central Patagonia, 47.5° S, Argentina. The valley was a major outlet of the former Patagonian Ice Sheet and the moraines that record its fluctuations are an important proxy record of climate change in southern South America. Such moraines are well-preserved in the Lago Pueyrredón valley owing in part to the semi-arid environment east of the mountain front. Here, we provide the first direct chronology for the age of the “Rio Blanco” moraine system by utilizing cosmogenic-nuclide surface exposure ages. Boulders on the moraines give 10Be exposure ages that indicate the Last Glacial Maximum (LGM) maximum extent occurred by 27–25ka. Subsequent advances occurred at 23–22ka, 20–18ka, and ca. 18–17ka. Initial deglaciation began after ca. 18–17ka and was interrupted as evidenced by the Lago Columna moraines up-valley. Subsequently the outlet glaciers occupying both the Lago Pueyrredón basin (Chilean name: Lago Cochrane) and the Lago Buenos Aires basin (Chilean name: Lago General Carrera) to the north, rapidly retreated more than 80km at around 16.5–15ka. The timing of the LGM maximum extent and the onset of deglaciation occurred broadly synchronously throughout Patagonia. Deglaciation resulted in a series of interconnected glacier-dammed lakes in the region that initially drained toward the Atlantic Ocean and later drained to the Pacific Ocean as a consequence of disintegrating ice in the Andes. [Copyright &y& Elsevier]

Abstract: While the Ensenadan Stage/Age (ca. 2.1 to 0.5Ma) was characterized by certain mammal associations in the Pampean plains, the Andean ranges of Patagonia and Tierra del Fuego, their piedmont areas and, in some cases, the adjacent lowlands were undergoing a well-defined alternating sequence of glacial and interglacial stages driven by the regional climate of Southernmost South America and Antarctica. This paper reviews the available geographical, geological and chronological evidence of glaciation during the Ensenadan stage/age, with perhaps more than 15 distinct glacial events, including the Great Patagonian Glaciation (GPG) and other cold episodes that took place before and after it. Finally, a tentative correlation of Patagonian glacial episodes and the Pampean biostratigraphic stages, based on radiometric dating and paleomagnetic studies, is herein presented. [Copyright &y& Elsevier]

Abstract: This paper presents an updated, extensive review of glacier fluctuations during the past 1000years in the extratropical Andes of South America between ca. 17° and 55°S. Given the variety of environmental conditions and evidence available for glacier fluctuations across this wide latitudinal range, regional accounts are given for the Desert Andes (∼17°–31°S), the Andes of central Chile and Argentina (31°–36°S), and the North (36°–45°S) and South (45°–55°S) Patagonian Andes. The techniques, dating limitations, and interpretations of the glacier records along this transect are also discussed. Information on glacier fluctuations in the Desert Andes is limited to the 20th century. Documentation on past glacier variations is more abundant in the Central Chilean-Argentinean Andes, but the number of chronologies dealing with glacier fluctuations prior to the 1900s is also limited. Most records indicate that glaciers were generally more extensive prior to the 20th century, with dates of maximum expansion ranging from the 16th to the 19th centuries. The number and extent of glaciers increase significantly in the Patagonian region, where the evidence available for dating glacier variations during the past centuries is more abundant and the dating control for glacier events is generally better than in the northern parts of the study area. For some Patagonian glaciers, maximum Little Ice Age (LIA) or post-LIA advances have been precisely dated by dendro-geomorphological determinations or in situ measurements. However, for most sites, the evidence available is still preliminary and there is considerable variability in the extent and timing of events related to the maximum LIA expansion identified in most areas between the 16th and 19th centuries. Evidence is starting to appear at a growing number of sites for glacier advances during the first half of the past millennium. These events were generally less extensive than the LIA maximum pulses. Despite the occurrence of several post-LIA readvances over the past 100–110years, most areas in the Andes of extratropical South America have experienced a general pattern of glacier recession and significant ice mass losses. The differences in the glacier histories observed at local and regional scales probably reflect the inherent limitations associated with the glacier records and/or the dating techniques used in each case together with the varying dominance of precipitation, temperature and other climatic and non-climatic factors on glacier mass balance and glacier dynamics. These differences indicate that the late Holocene glacier history of southern South America is more complex than commonly assumed. The evidence discussed in this study highlights not only the immense potential for glaciological studies of this region but also a significant need for an increased number of detailed, well-dated records of glacier fluctuations. [Copyright &y& Elsevier]

In this study we explored how picoplankton community structure and diversity varied along three cascade oligo-mesotrophic reservoirs of the Limay River (Patagonia, Argentina): Alicura, Piedra del Águila and Ramos Mexía. We analyzed the spatial changes, covering lotic and lentic stretches along a gradient of 262 km from Andes to steppe, and we also sampled the main affluent of the Limay River (Collon Cura). In all sampling sites the main limnological variables were measured, and the picoplankton abundance (autotrophic and heterotrophic) was analyzed by flow cytometry. The bacterial biodiversity was assessed using high throughput sequencing Illumina MiSeq. We expected an increase in the trophic state along this series of cascade reservoirs, which would determine spatial differences in the structure of the picoplankton communities. We also hypothesized that the lotic and lentic conditions along the system would influence the bacterial composition. The results showed a slight increase in trophic state together with an increase in overall picoplankton abundance downstream, towards Ramos Mexía Reservoir. Picocyanobacteria were represented by phycoerythrin-rich cells all along the system, in accordance to the pattern described for oligotrophic aquatic ecosystems. Multivariate analyses based on bacterial OTU composition and environmental variables showed a spatial ordination of sites following the trend of increasing trophic state downstream. Molecular analyses of bacterial OTU diversity also showed an increase in richness and a decrease in evenness at the lotic stretches, and the opposite pattern in the reservoirs, suggesting that water retention time may play a role in structuring the community composition. [ABSTRACT FROM AUTHOR]

Resolving the history of vegetation, fire, and glaciation on the eastern slope of the central Patagonian Andes (44°-49°S) since the Last Glacial Termination (T1) has proved difficult. This is due to the steep environmental gradients, vegetation heterogeneity, and scarcity of dated glacial deposits and geomorphic features. Unsurprisingly, published records show important heterogeneities which limit our understanding of the timing and magnitude of climate and vegetation changes, and their driving mechanisms since T1. In this paper, we describe sediment cores from small closed-basin lakes located in the deciduous Nothofagus forest zone near Coyhaique, Chile. Our results indicate that the Coyhaique glacier lobe abandoned its final Last Glacial Maximum position just before ~17.9 cal kyr BP and underwent a step-wise recession that included a halt/readvance that culminated at ~16.8 cal kyr BP, contemporaneous with the formation of an ice-dammed proglacial lake in the Coyhaique/Balmaceda sector. This glacial lake stood at its highest level between ~17.9–17.2 cal kyr BP (<726 and > 650 m.a.s.l.), lowered between ~17.2–16.2 cal kyr BP (<650 and > 570 m.a.s.l.), and disappeared thereafter. Herbs and shrubs, currently dominant in high Andean and Patagonian steppe environments, colonized the ice-free terrains distal to the glacier margins and proglacial lakes under cold and dry conditions. This was followed by a steady increase in Nothofagus between ~16.6–14.8 cal kyr BP that led to the establishment of forests starting at ~14.8 cal kyr BP. The Holocene started with a sudden increase in Nothofagus and disappearance of conifers in the context of increase fire activity between ~11.7–9.4 cal kyr BP. Closed-canopy Nothofagus forests persisted virtually unaltered from ~9.4 cal kyr BP to the present day, despite frequent explosive volcanism and millennial-scale variations in fire regimes, attesting to their extraordinary postglacial resilience which contrasts with their behavior during T1. Recent large-scale deforestation by fire, livestock grazing, and the spread of non-native invasive plant species drove the fastest and largest-magnitude shifts seen during the last ~16,500 years. • Glacial retreat began at ~17.9 ka and followed a stepwise pattern until ~16.2 ka. • Arboreal Pollen rose at ~16.6 ka driven by stronger Southern Westerly Winds (SWW). • Rainforest conifers peaked between ~14.8–11.7 ka suggesting maximum SWW influence. • Fires and disappearance of conifers suggest weak SWW between ~11.7–9.4 ka. • Extraordinarily resilient Nothofagus forests have persisted since ~9.4 ka. [ABSTRACT FROM AUTHOR]

This study investigates the spatial structure and the seasonal occurrence of foehn wind to the east of the Andes using a flow blocking analysis in a 20-year climate simulation. The latter was performed by the Eta-CPTEC regional model at 50-km horizontal resolution. This version of the model includes a cut-cell scheme to represent topography and a finite-volume vertical advection scheme for dynamic variables. The results indicate that foehn wind more frequently blows during winter and spring on the eastern slopes of the Andes, except to the south of 37° S where it blows at all seasons. Higher mountains of the Central Andes (27° S–35° S) and the High Plateau (15° S–27° S) result in blocked foehn events, with a weak adjustment to the geostrophic balance. On the Central Andes, rain and snow on mountain tops may also contribute to generate foehn wind on the eastern slopes. The results show that a low pressure develops to the east of the Central Andes, and also to the east of the High Plateau when foehn blows. Lower mountains in Patagonia (to the south of 37° S) result in more frequent non-blocked foehn event, with better adjustment to the geostrophic balance. [ABSTRACT FROM AUTHOR]

Radiations of ectothermic vertebrates across cold climates depend on the coordinated evolution of multiple traits that compensate for the constraints imposed by limited and fluctuating resources, such as temperature, food and oxygen. One of nature's most prolific such radiations, Liolaemus lizards, has diversified across the extreme cold climates of the Andes and Patagonia. Remarkably, the prevailing patterns of reptile herbivory are opposed by Liolaemus which, in contrast with lizards generally, have repeatedly evolved plant consumption across small-bodied species from cold climates. Herbivory is hypothesized to depend on the evolution of multiple traits that maximize absorption of nutrients from an intrinsically poor-quality diet, such as increases in gastrointestinal tract size and increases in the density of nematodes in the intestine that may assist with plant digestion. Here, a comparative phylogenetic approach across Liolaemus species is implemented to test these hypotheses, which have only been investigated nonphylogenetically. Results reveal that intestine length increases consistently with increasing herbivory, whereas stomach size or nematode load are not associated with plant consumption. Body size plays no role in herbivory either. Consequently, this evidence places emphasis on the enlargement of the intestine to facilitate the evolution of herbivory in cold climates. [ABSTRACT FROM AUTHOR]

Lake sediments are key archives for paleoenvironmental investigation as they provide continuous records of the depositional history of the lake and its watershed. Lake Futalaufquen (42.8°S) is an oligotrophic waterbody located in Los Alerces National Park in the Andes of northern Patagonia, South America. A sedimentary sequence covering 1600 years was recovered to analyze the potential for paleoenvironmental reconstructions of the last millennia. Integration of different geochemical and mineralogical parameters and comparison with climatic reconstructions from other Patagonian records give clues for the identification of a warm period around AD 800–1000, associated with the Medieval Climatic Anomaly. The high frequency of tephra layers beginning in the mid-sixteenth century precludes identification of the Little Ice Age, recorded in northern Patagonia as a cold period from the fourteenth to the eighteenth century. Furthermore, the parameters analysed do not provide evidence of late-twentieth-century global warming. However, Zn deposition, a long-distance atmospheric transport process of anthropogenic origin, was identified during the last century. [ABSTRACT FROM AUTHOR]

Marine sedimentary rocks of the lower Miocene Monte León Formation of southeastern Patagonia (Austral Basin), Argentina are important geological archives for better understanding regional tectonics, paleoenvironments, oceanography, and climate. In this paper, we describe assemblages of invertebrates, palynomorphs, foraminifera, ostracods and calcareous nannofossils in a stratigraphical and sedimentological framework, which suggest deposition during a transgressive-regressive cycle. From base to top, the lowermost outcropping deposits of the Punta Entrada Member represent an inner shelf environment, formed during a transgressive phase. The zone of maximum flooding is marked by a high diversity of protoperidiniaceans (heterotrophic) and offshore dinoflagellate cysts, an increase in the percentage and size of planktonic foraminifera, and a decrease in shallow water benthic foraminifera. Regressive deposits in the upper part of the Punta Entrada Member exhibit a progradational stratal stacking pattern and are characterized by an upward decrease in bioturbation and in the content of marine invertebrates; the dinoflagellate cyst assemblages point toward shallower and more restricted marine conditions than in underlying deposits. The cycle ends with the Monte Observación Member, which contains an impoverished and mostly reworked fauna of invertebrates. The presence of monospecific reefs of Crassostrea orbignyi , the decrease in dinoflagellate cysts and calcareous microfossils diversity, and the increase of continental palynomorphs suggest progressively shallower conditions and increasing influence of freshwater discharge. Although eustatic controls could have contributed to the sedimentary evolution of the Monte León Formation, the upward regressive trend is interpreted as the result of tectonism linked to the Andean orogeny, which led to the uplift, exhumation, and erosion of the highlands in the west. This is supported by the abundance of pyroclastic material, together with reworked specimens of Upper Cretaceous forams and Upper Cretaceous and middle Eocene dinoflagellate cysts in the upper part of the Punta Entrada Member and in the Monte Observación Member. • Multiproxy data indicate that study rocks represent a transgressive-regressive cycle. • A maximum flooding and/or higher organic flux zone was identified at the coastal cliffs. • The regressive trend was the result of tectonics, sediment supply dynamics, and volcanism. • Cretaceous/Eocene forams and dinocysts evidence exhumation and reworking from the Andes. [ABSTRACT FROM AUTHOR]

Pleistocene glaciations have promoted important landscape transformations as a result of high rates of erosion and rapid sediment evacuation to adjacent marine basins. In the Patagonian Andes the role of the Patagonian Ice Sheet on landscape evolution, in particular the spatial patterns of glacial erosion and its influence on sediment fluxes, is poorly documented. Here, we investigate the Middle and Late Pleistocene sedimentary record of the continental slope from Ocean Drilling Program (ODP) Site 861, offshore Patagonia (46°S), to evaluate the link between glaciations, mountain range erosion and continental margin strata formation. Petrographic analysis of the sand‐size fraction (0.063–2 mm) and ɛNd and 87Sr/86Sr measurements in the silt‐size fraction (10–63 µm) indicate that glacial erosion over the last 350,000 years has focused within the Patagonian Batholith, with a minor influence of a proximal source to the drilling site, the Chonos Metamorphic Complex. This shows that erosion has focused in the core of the northern Patagonian Andes, coinciding roughly with the location of the Liquiñe‐Ofqui Fault Zone and the zone of concentrated precipitation during glaciations, suggesting a combined climatic and structural control on glacial erosion. Temporal variation in the provenance signal is contemporaneous with a marked change in the stratigraphy of ODP Site 861 that occurred after the glaciation of MIS 8 (~240 kyr ago). Before MIS 8, a restricted provenance signal and coarse lithofacies accumulated on the continental slope indicates spatially restricted erosion and efficient transfer of sediment towards the ocean. In contrast, very high provenance variability and finer continental slope lithofacies accumulation after MIS 8 suggest a disorganized expansion of the areas under erosion and a more distal influence of ice sediment discharge to this site. We argue that this change may have been related to a re‐organization of the drainage patterns of the Patagonian Ice Sheet and flow of outlet glaciers to the continental margin during the last two glaciations. [ABSTRACT FROM AUTHOR]

Volcanic eruptions often modify the structure and function of ecosystems at large geographical scales. However, the extent to which species diversity patterns respond to these major natural disturbances is still poorly known. We tested the shape of the species richness – elevation relationship (SRER) and its environmental correlates (thermal environment at ground level, vegetation structure and soil attributes) before and 6 months after (in the first summer) the most recent eruption of the Puyehue Cordon Caulle volcanic complex (PCCVC), which caused an extensive ash accumulation in northwestern Patagonia, Argentina.We re‐established 32, 100‐m2 sampling plots of nine pitfall traps, placed every 100 m of altitude from the base to the summit of three mountains differentially affected by ash deposition, and from which we had pre‐eruption data on richness and environmental variables.Coverage‐based rarefaction/extrapolation curves showed a local post‐eruptive decrease in richness on only one mountain. Generalised additive models (GAMs) showed no significant differences between pre‐ and post‐eruptive SRER shapes. Partial least squares structural equation modelling (PLS‐SEM) showed that woody vegetation and the thermal environment accounted for most of the variation in richness before and after the eruption. Soil attributes were only indirectly associated with beetle richness and the association was mediated by woody vegetation. Ash accumulation ameliorated the thermal environment, promoting a local increase in beetle richness.The rapid recovery of the SRER shape and its environmental correlates suggest that the structuring of local diversity patterns at temperate latitudes of the southern hemisphere is resilient to major volcanic eruptions. [ABSTRACT FROM AUTHOR]

The rise of the southern Andes and the Quaternary glacial cycles influenced the landscape of Patagonia, affecting the phylogeographic and biogeographic patterns of its flora and fauna. Here, we examine the phylogeography of the freshwater fish, Percichthys trucha, using 53 sequenced microsatellite DNA markers. Fish (n= 835) were collected from 16 river systems (46 locations) spanning the species range on both sides of the Andes. Eleven watersheds drain to the Pacific, five of which are trans-Andean (headwaters east of Andes). The remaining five drainages empty into the Atlantic. Three analytical approaches (neighbour-joining tree, hierarchical AMOVAs, Structure) revealed evidence of historic drainage reversals: fish from four of the five trans-Andean systems (Puelo, Futalaufquen/Yelcho, Baker, Pascua) exhibited greater genetic similarity with Atlantic draining systems than with Pacific systems with headwaters west of Andes. Present-day drainage (Pacific versus Atlantic) explained only 5% of total genetic variance, while ancestral drainage explained nearly 27% of total variance. Thus, the phylogeographic structure of P. trucha is consistent with episodes of drainage reversal in multiple systems and suggests a major role for deglaciation in the genetic and indeed the geographical distribution of P. trucha in Patagonia. The study emphasizes the significant role of historical processes in the current pattern of genetic diversity and differentiation in a fish from a southern temperate region. [ABSTRACT FROM AUTHOR]

In this study, we identify the main modes of variability of the Normalized Difference Vegetation Index (NDVI) and their relationships with precipitation and temperature variations across northern Patagonia (36°–45° S). In this approach, we combined a recently developed high-resolution gridded dataset (20 × 20 km) for temperature and precipitation with a re-scaled NDVI grid to spatially match the climate database. Climate–vegetation relationships were analyzed taking into account a wide range of temporal variations (intra- to inter-annual) of both climate and NDVI. An Empirical Orthogonal Function analysis performed on NDVI delimits four regions that are spatially consistent with previous vegetation classifications for northern Patagonia. In addition, these coherent NDVI regions show similarities with the spatial precipitation patterns and the temporal evolution of precipitation over the common period 2001–2010. Both NDVI and precipitation show evident annual cycles over the Mediterranean climatic region in northwestern Patagonia. These annual cycles decrease in amplitude toward the eastern arid rangelands, and to the south on the evergreen all-year-round rainforests. Significant positive relationships between monthly precipitation and NDVI are recorded in the dry temperate rangelands in northeastern Patagonia. In contrast, direct associations between monthly NDVI and precipitation were absent in the Central Patagonia cold grasslands, where seasonal interactions between precipitation, temperature and NDVI appear to be more relevant. Relationships between NDVI and temperature are generally weaker east of the Andes, but significantly positive in late winter/spring over the temperate forests in western North Patagonia. Our results indicate that climate–NDVI relationships in northern Patagonia are biome specifics with the occurrence of temporal lags and precipitation–temperature interactions in the responses of vegetation to climate at some ecosystems. [ABSTRACT FROM AUTHOR]

Few studies have examined in detail the sequence of events during the last glacial termination (T1) in the core sector of the Patagonian Ice Sheet (PIS), the largest ice mass in the Southern Hemisphere outside of Antarctica. Here we report results from Lago Edita (47°80 S, 72°250W, 570ma.s.l.), a small closed-basin lake located in a valley overridden by eastward-flowing Andean glaciers during the Last Glacial Maximum (LGM). The Lago Edita record shows glaciolacustrine sedimentation until 19 400 yr BP, followed by organic sedimentation in a closed-basin lake and a mosaic of cold-resistant hygrophilous conifers and rainforest trees, along with alpine herbs between 19 400 and 11 000 yr BP. Our data suggest that the PIS retreated at least ~90 km from its LGM limit between ~21 000 and 19 400 yr BP and that scattered, low-density populations of cold-resistant hygrophilous conifers, rainforest trees, high-Andean and steppe herbs thrived east of the Andes during the LGM and T1, implying high precipitation levels and southern westerly wind (SWW) influence at 47° S. The conifer Podocarpus nubigena increased between 14 500 and 13 000 yr BP, suggesting even stronger SWW influence during the Antarctic Cold Reversal, after which it declined and persisted until 11 000 yr BP. Large increases in arboreal pollen at ~13 000 and ~11 000 yr BP led to the establishment of forests near Lago Edita between 10 000 and 9000 yr BP, suggesting a rise in the regional tree line along the eastern Andean slopes driven by warming pulses at ~13 000 and ~11 000 yr BP and a subsequent decline in SWW influence at ~11 000 yr BP. We propose that the PIS imposed a regional cooling signal along its eastern, downwind margin through T1 that lasted until the separation of the northern and southern Patagonian ice fields along the Andes during the Younger Dryas period. We posit that the withdrawal of glacial and associated glaciolacustrine environments through T1 provided a route for the dispersal of hygrophilous trees and herbs from the eastern flank of the central Patagonian Andes, contributing to the afforestation of the western Andean slopes and pacific coasts of central Patagonia during T1. [ABSTRACT FROM AUTHOR]

Aim Our aim was to determine the combined impacts of Pleistocene climatic oscillations and glacial periods with recognized biogeographical barriers on the evolutionary history of huemul deer ( Hippocamelus bisulcus). Location Southern Chile and Argentina's Andean forest, and Patagonian fjords. Methods We examined the phylogeography of huemul using 772 bp of the mitochondrial DNA control region sequence from 275 samples (29 locations) collected throughout the distributional range of the species. We grouped samples into clusters based on Bayesian genetic and spatial structure analyses and reconstructed the species' phylogeographical and demographic history. Results We observed 63 haplotypes that grouped into three clusters (Central Chile, North Patagonia and South Patagonia). All but five haplotypes in North and South Patagonia were distributed locally. Bayesian skyline plots showed that population sizes remained fairly constant until an increase during and after the Last Glacial Maximum. Genetic diversity was generally low, except in three populations in the eastern Andes and on Wellington Island (Patagonian fjords). Main conclusions Our results suggest that the biogeographical separation of huemul into phylogeographical groups has been heavily influenced by Pleistocene glacial stages, and more recently by habitat fragmentation and isolation. This provides the first evidence that the region west of the Cordilleran ice field was a refugium for at least one species of large mammal during the Pleistocene in southern South America. These results have direct implications for the conservation and management of this endangered deer species. [ABSTRACT FROM AUTHOR]

The limit of a species' distribution can be determined biotically if an environmental gradient causes the loss of critical mutualists such as pollinators. We assessed this hypothesis for Embothrium coccineum, a self-incompatible red-flowered treelet growing along a strong west-east precipitation gradient from rainforest to forest-steppe ecotone in the rain shadow of the southern Andes in northwestern Patagonia. For 16 populations along this gradient, we quantified composition of the pollinator assemblage, pollination efficiency and limitation, and reproductive output. The treelet has a generalized pollination system, but the hummingbird Sephanoides sephaniodes was the most effective pollinator. The relative importance of this hummingbird as a flower visitor within populations influenced pollen transfer and fruit set more strongly than local precipitation. As hummingbirds and other pollinators, including passerine birds and nemestrinid flies, were replaced by bees towards the dry eastern range limit, pollen limitation increased and reproduction eventually failed. These results support the hypothesis that pollinators can act as important biotic filters influencing plant distribution, and warn against predictions of geographical range shifts based solely on climatic variables. [ABSTRACT FROM AUTHOR]

Cold stress decreases the growth and productivity of agricultural crops. Psychrotolerant plant growth-promoting bacteria (PGPB) may protect and promote plant growth at low temperatures. The aims of this study were to isolate and characterize psychrotolerant PGPB from wild flora of Andes Mountains and Patagonia of Chile and to formulate PGPB consortia. Psychrotolerant strains were isolated from 11 wild plants (rhizosphere and phyllosphere) during winter of 2015. For the first time, bacteria associated with Calycera, Orites, and Chusquea plant genera were reported. More than 50% of the 130 isolates showed ≥33% bacterial cell survival at temperatures below zero. Seventy strains of Pseudomonas, Curtobacterium, Janthinobacterium, Stenotrophomonas, Serratia, Brevundimonas, Xanthomonas, Frondihabitans, Arthrobacter, Pseudarthrobacter, Paenarthrobacter, Brachybacterium, Clavibacter, Sporosarcina, Bacillus, Solibacillus, Flavobacterium, and Pedobacter genera were identified by 16S rRNA gene sequence analyses. Ten strains were selected based on psychrotolerance, auxin production, phosphate solubilization, presence of nifH (nitrogenase reductase) and acdS (1-aminocyclopropane-1-carboxylate (ACC) deaminase) genes, and anti-phytopathogenic activities. Two of the three bacterial consortia formulated promoted tomato plant growth under normal and cold stress conditions. The bacterial consortium composed of Pseudomonas sp. TmR5a & Curtobacterium sp. BmP22c that possesses ACC deaminase and ice recrystallization inhibition activities is a promising candidate for future cold stress studies. [ABSTRACT FROM AUTHOR]

We analyzed 28-year-long monthly oxygen isotope composition of precipitation (δ18Op) data from Punta Arenas (Chile) on the leeward side of the Andes to understand how different synoptic weather types and moisture transport pathways influence δ18Op variability in this region. Combining weather station 6 h precipitation data and atmospheric back trajectories, we found that in such a region where the atmospheric circulation pattern is dominated by very strong westerlies, an increased monthly proportion of easterly-delivered precipitation—with the air-mass trajectory path evading the influence of Andean "isotopic rain shadow" and having less rainout en route—would increase δ18Op. These synoptic easterlies are a result of quasi-stationary blocking-like flow that are an important but underappreciated part of regional circulation patterns and climate. In addition, synoptic easterlies are more often associated with heavy precipitation events as shown by weather station data and higher deuterium excess that indicates weaker post-condensation raindrop re-evaporation. Therefore, our analysis demonstrated the process link between the frequency of synoptic weather types characterized by blocking-like flow and temporal variations in δ18Op in Southern Patagonia. We conclude that isotope proxy paleo-records in this region could provide unique insights into the behaviors and dynamics of the large-scale Southern Hemisphere Westerly Winds over long timescales. [ABSTRACT FROM AUTHOR]