Southeastern South America Research Articles

Compound dry-hot-fire events connecting Central and Southeastern South America: an unapparent and deadly ripple effect

South America has experienced severe compound drought-heatwaves (CDHW), exacerbating fires. Recently, the unprecedented Pantanal 2020 fire season (P20F), burning a third of the biome, resulted in well-reported local impacts on the ecosystem, economy, and health. Nevertheless, the long-range ripple effects of this event remain unknown. We investigated the P20F-related cascading hazards, integrating models, observational and satellite-based data. P20F-related smoke elevated PM2.5 levels in the SA’s most populated area, exceeding WHO guidelines by up to 600%. Smoke-induced air pollution episodes coincided with widespread heatwaves, amplifying health risks. The mortality burden attributable to this multi-hazard short-term (14 days) exposure was estimated to be 2150 premature deaths (21% increase above expected levels). Our findings highlight that the impacts of CDHW-fires in SA are beyond the local level, implying growing challenges for risk management and public health and the need for governance based on telecoupled flows, linking different systems over multiple scales.

Advancing global solar photovoltaic power forecasting with sub-seasonal climate outlooks

Given the high weather dependency of solar photovoltaic energy, accurate weather information ranging from days to weeks in advance are required for stable plant operation and management. This study emphasizes that sub-seasonal climate outlooks can advance global solar power forecasting. We evaluate the capacity factor (CF) for standard test conditions (CFstc), calculated from atmospheric reanalysis of surface solar irradiance and ambient air temperature, by comparing it with actual CF from two solar plants in Korea. Results confirm CFstc as a reliable estimate of actual CF. Application of this methodology to four-week outlooks from two state-of-the-art sub-seasonal climate forecast systems shows a significant anomaly correlation coefficient (ACC) skill for global solar power forecasting at least one week in advance (5–11 forecast days). Regional ACC skills vary at extended lead times, with South Asia, eastern South America and eastern Australia maintaining ACC > 0.6 for up to two weeks (12–18 forecast days). Notably, useful ACC skill persists for up to four weeks (26–32 forecast days) across 70.9 % of global land areas. These findings suggest that sub-seasonal climate outlooks can provide decision-making information in developing more reliable solar energy strategies, highlighting the importance of transdisciplinary collaboration between renewable energy and meteorological sectors.

Holocene landscape changes in response to sea level oscillations and agricultural intensification in a coastal plain of southeastern South America

This study identified landscape changes in response to variations in mean sea level (MSL) and anthropogenic intervention, from the Early to Late Holocene in Southestern South America. Ananalysis based on palynology and sedimentary bacterial DNA from two sediment cores from the Patos-Mirim System (PMS) is introduced for the first time, to achieve an integrated paleoenvironmental and ladscape reconstruction. The data indicated an east-west migration of the freshwater and forest environments set in the lowlands during the transgressive period (6000–5000 cal yr BP) and an increase in external total biomass input during this MSL rise. A consolidated vegetation onset was inferred, especially of forest environments, after the Holocene Climatic Optimum (5000 cal yr BP). During the last century, landscape changes especially associated with anthropogenic factors were clearly identified from the palynological assemblages. That is, an alternation between Poaceae and Cyperaceae, the first occurrence of Pinus spp. and an increase in the influx of herbs and trees flagged the increase in cultivated areas due to the agricultural and agroforestry intensification. Extreme values of palynological influx appear to be a good proxy for the impact of El Niño events on the sedimentary record, which were associated to increased precipitation. The study also clearly demonstrates the high environmental stress generated by human activities, e.g. loss of plant diversity and changes in the bacterial abundance due to the higher agrochemicals input.

Testing a spaceborne passive‐microwave severe hail retrieval over Argentina using ground‐based dual‐polarization radar data

AbstractPassive‐microwave hail detection methods rely on the scattering signal produced by large ice hydrometeors. Recently, passive‐microwave hail retrieval methods have been trained by pairing Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) and Global Precipitation Measurement (GPM) Microwave Imager (GMI) data with United States surface hail reports to present a global hail climatology. In particular, Southeastern South America (SESA) stands out as a hotspot for hail occurrence, more specifically northeastern Argentina. However, the analysis performed with the available ground hail reports in Argentina shows some differences from the available ground hail reports in Argentina, as it locates the most frequent hail storms in the southwestern (Mendoza and Córdoba) and northeastern (Misiones) regions of SESA. To assess the retrieval from a regional perspective, we take a case study approach and focus on polarization‐corrected temperature features (PCTFs) with a detected . We mainly rely on polarimetric weather radars and a hydrometeor identification algorithm (HID) as a proxy for ground truth. Results indicate that the hail retrieval responds mainly to low 37‐GHz polarized corrected (brightness) temperatures (PCTs) and large PCTF area, while HID outputs show that high probabilities of hail also correspond to abundantly suspended graupel. The observed passive‐microwave hail detection hotspot could be influenced by mesoscale convective systems with deep columns of graupel‐sized frozen hydrometeors, common in northeastern Argentina.

Effects of Storm‐Time Winds on Ionospheric Pre‐Midnight Equatorial Plasma Bubbles Over South America as Observed by ICON and GOLD

AbstractThis study uses satellite measurements of plasma densities and thermospheric winds to analyze the effects of the November 2021 geomagnetic storm on ionospheric pre‐midnight topside plasma bubbles over South America. Using observations from the Ionospheric Connection Explorer (ICON) and the Global‐scale Observations of the Limb and Disk (GOLD) satellites, we find that pre‐midnight topside plasma bubbles were inhibited over eastern South America during the recovery phase of the storm. This is particularly notable because of the otherwise high occurrence rate of plasma bubbles at these longitudes during this season. This inhibition coincided with the recovery phase of the geomagnetic storm, marked by a northward turning of the z‐component of the interplanetary magnetic field (IMFBz) and quiet‐time values of the SuperMAG Auroral Electrojet Index (SME). We observed a westward turning of the zonal wind before the bubble inhibition, so we conclude the inhibition of topside plasma bubbles is likely related to a westward disturbance dynamo electric field (DDEF) causing a downward drift and suppress the growth of the instability responsible for bubble development. Contrary to theoretical predictions, we do not observe notable changes to the meridional wind during the event. These results provide new insights into the ionosphere‐thermosphere system's response to geomagnetic storms and highlight the role of wind patterns in inhibiting ionospheric irregularities, contributing to better predictive models for these phenomena.

Precipitation variability at sub-seasonal scale under the ENSO influence in southeastern South America

Precipitation variability at sub-seasonal scale under the ENSO influence in southeastern South America

Effects of anticoagulants time storage on stable isotope values of crocodilians’ blood tissues

ABSTRACT Rapid coagulation of reptile blood often hinders its use in studies in remote and difficult-to-access areas, necessitating chemical preservation. Therefore, understanding the potential effects of anticoagulants on the isotopic compositions of blood is essential to avoid issues in interpreting the results for ecological studies. In this study we aimed to verify whether the storage time of the blood tissue in anticoagulants can influence its isotopic compositions of the broad-snouted caiman (Caiman latirostris), an ectothermic top predator from eastern South America. Blood samples were obtained from ten adult females of C. latirostris from a commercial breeding facility in 2015. Samples were stored in vials containing ethylenediaminetetraacetic acid (EDTA) and sodium heparin (SH) and centrifuged after 2 and 8 h to separate red blood cells and plasma. No effect of time was found on the δ13C and δ15N of whole blood, plasma, and red blood cells in contact with the two types of anticoagulants, EDTA and SH. The findings have practical implications for researchers in this field, as they suggest that anticoagulants can be used effectively for at least eight hours under refrigeration.

Exploring the mitochondrial genomes and phylogenetic relationships of trans-Andean Bryconidae species (Actinopterygii: Ostariophysi: Characiformes).

Comparative mitogenomics and its evolutionary relationships within Bryconidae remains largely unexplored. To bridge this gap, this study assembled 15 mitogenomes from 11 Bryconidae species, including five newly sequenced. Salminus mitogenomes, exceeding 17,700 bp, exhibited the largest size, contrasting with a median size of 16,848 bp in the remaining species (Brycon and Chilobrycon). These mitogenomes encode 37 typical mitochondrial genes, including 13 protein-coding, 2 ribosomal RNA, and 22 transfer RNA genes, and exhibit the conserved gene arrangement found in most fish species. Phylogenetic relationships, based on the maximum-likelihood method, revealed that the trans-Andean species (found in northwestern South America) clustered into two main sister clades. One clade comprised the trans-Andean species from the Pacific slope, Brycon chagrensis and Chilobrycon deuterodon. The other clade grouped the trans-Andean species from the Magdalena-Cauca Basin Brycon moorei and Salminus affinis, with their respective cis-Andean congeners (found in eastern South America), with Brycon rubricauda as its sister clade. Since the current members of Brycon are split in three separated lineages, the systematic classification of Bryconidae requires further examination. This study provides novel insights into mitogenome characteristics and evolutionary pathways within Bryconidae, standing as crucial information for prospective phylogenetic and taxonomic studies, molecular ecology, and provides a valuable resource for environmental DNA applications.

Analysis of lithium trade patterns and influencing factors in the regions along the "Belt and Road".

Lithium has broad applications in several emerging industries and fields, including high energy batteries, energy storage, aerospace, and controlled nuclear reactions. Currently, the discrepancy between the supply and demand for lithium resources increases, and its distribution is uneven. Within the framework of the "Belt and Road" Initiative, the lithium trade pattern evolves constantly. However, the trade pattern of lithium in the nations along the "Belt and Road" is likely to face substantial repercussions in modern world of unilateral protectionism and geopolitical conflicts. Taking the social network analysis approach as a tool, this study first examines the characteristics of the lithium trade network structure as it has evolved over the years in the Belt and Road countries, from 2000 to 2022. Additionally, this study uses the quadratic assignment problem approach to analyze the factors influencing the evolution of the lithium trade network. The study shows that: (1) The spatial patterns of import and export trade network of lithium in countries along the route has a certain path dependence. And the market is mainly concentrated in East Asia, Central and Eastern Europe, South America and Southeast Asia. (2) The network density of the countries along the route has increased year after year, but it remains low. And the fluctuation of the network's reciprocity has increased, with a huge magnitude of variation. The number of core countries in the network has decreased over time, but the core-periphery structure has stayed largely steady. China, Chile, and South Korea are the network's main node countries. (3) Regarding the influencing factors, the differences in economic and technological development between these countries have a beneficial impact on the formation of lithium trade; whether or not regional trade agreements have been signed, the differences about average tax rates for mineral products, bordering countries, and similar languages and cultures are all conducive to the establishment of close trade links. The contribution of this essay is of paramount importance for understanding different countries' role along the Belt and Road in the lithium trade network pattern, and promoting regional trade cooperation.

Climate storylines as a tool for interdisciplinary dialogue on risk decision-making: Analyzing a severe drought in southeastern South America

Recently, we are witnessing a growing interest in the study of climate narratives and storylines. These are seen as critical tools both for improving shared understandings involving different stakeholders (including scientists from different disciplines) and guiding initiatives for transformative adaptation actions and decision making. This paper approaches the storylines about a severe drought event that took place in southeastern South America (SESA) in 2008/2009 from an interdisciplinary dialogue between climatologists and anthropologists. This approach responds to the need for a more robust understanding of the event and the responses adopted locally, i.e: not restricted to physical aspects but considering socio-economic and political aspects, with the aim of contributing to the development of socially relevant climatic information for realistic climate risk decision making contexts. In particular it intends to contribute to the decision-making processes of government agencies focused on climate communication and public climate services, such as national and weather services and regional agencies. Considering disciplinary differences, we account for the interpretative polyphony regarding this event, i.e.: what each actor/sector is talking about (for what and to whom they are talking about) when referring to "the drought", and analyze climate storylines as an agonistic field of meanings. This implies recognizing the disputes and contradictions among them, how different storylines promote certain lines of argumentation and meanings to the detriment of others, knowledge gaps, the role of social power relations, socio-political order factors and their impact in terms of the necessary transformations towards an environmentally sustainable and socially just horizon.

Global patterns of taxonomic and phylogenetic endemism in liverwort assemblages

Exploring the worldwide patterns of endemism and the processes that lead to the formation of high-endemism centers is crucial in biogeography. This study examines the geographic distribution and ecological influences on the endemism of liverworts across 390 regions worldwide. We assess phylogenetic endemism and relative phylogenetic endemism in relation to eleven environmental factors, which represent current and Quaternary climate variations, as well as topographic and environmental heterogeneity. Areas with higher endemism in liverworts tend to have higher temperatures, precipitation, and environmental heterogeneity, but lower temperature seasonality and lesser impacts from Quaternary climate changes. Regions exhibiting notably high endemism are predominantly found in tropical Asia, Madagascar, eastern Australia, and the Andes, while those with notably low endemism are generally in temperate Eurasia and North America, parts of Africa, and eastern South America. Centers of neo-endemism are mainly in southern Africa, whereas centers of paleo-endemism are in southern South America, tropical Asia, and New Zealand. Environment variability is a more significant predictor of phylogenetic endemism than current climate conditions, which are themselves more predictive than variables related to Quaternary climate changes. Nevertheless, these three types of explanatory variables combined explain only about one-third of the variance in phylogenetic endemism.

Environmental changes in the southeastern Pampa plain (southeastern South America) during the last millennium based on multiple lacustrine indicators and historical records

Environmental changes in the southeastern Pampa plain (southeastern South America) during the last millennium based on multiple lacustrine indicators and historical records

Dendroclimatology of Prosopis nigra in the Espinal woodlands, southeastern South America

This paper evaluates the dendrochronological potential of Prosopis nigra in the subtropical xerophytic forests of northeastern Argentina, an area of the Espinal forest particularly poor in dendrochronological records. Our study is based on tree-ring analyses of 23 cross sections providing a high-quality chronology (Rbar = 0.24 and EPS = 0.92). The mean annual radial increment recorded was 2.38 ± 1.51 mm. The inter-annual variability in the tree rings indicates that water availability from the previous winter to the current summer growing season is the major forcing on tree growth. Above-average rainfall and SPEI from July to February favored radial growth. Our results show for the first time the strong influence of both ENSO 3.4 and subtropical Atlantic SST variations, mediated by changes in local precipitation, on the growth of P. nigra in the Espinal. We concluded that P. nigra has great dendrochronological and dendroclimatological potential, since its rings are visible after careful polishing of the samples, and its inter-annual variations in radial growth are related to regional climate variability. These results can help improve our knowledge of the vulnerability of xerophytic forests to climate change in northeastern Argentina. In addition, this dendroclimatological study provides new proxy climate records for the Pampean grasslands, one of the most important food producing regions in the world.

The South American precipitation trends under (or not) El Niño‐Southern Oscillation influences and relationship with large‐scale circulation

AbstractThe precipitation trend patterns in South America (SA) are determined using trend empirical orthogonal function analysis for the 1951–2016 period. The associated large‐scale tropical and extratropical anomalous circulation patterns are also examined. The words “total” and “residual” refer to the monthly anomalies and monthly anomalies without the El Niño–Southern Oscillation (ENSO) effects, respectively. The total precipitation features a positive trend in southeastern SA (SESA, southern Brazil, Uruguay, most of eastern Argentina) and northern Chile, and a negative trend over central‐eastern Brazil and central Amazonia. The residual precipitation shows an increased positive trend over most of the coastal extension of northern SA and Colombia; a weak positive trend over southern Brazil, northeastern Argentina, and northern Chile; and a negative trend over central‐eastern SA and western Amazonia. The differences between the total and residual precipitation trend patterns in tropical SA is explained as responses to total and residual zonally asymmetric anomalous sea surface temperature (SST) patterns, respectively. The total SST pattern along the equatorial Pacific configures the Pacific Decadal Oscillation, which impacts ENSO variability and as response intensifies the Walker circulation. Without the ENSO, the Walker cell is mainly driven by the tropical Indian and Atlantic Oceans, which configure residual asymmetric anomalous warming. Furthermore, the warming in the equatorial Indian and eastern Pacific Oceans, in the presence of ENSO, induces a Rossby wave train‐type anomalous pattern that extends across the South Pacific into SA and modulates the atmospheric anomalous circulation over SESA. In this region, an anomalous anticyclonic accompanied by an intensified South American Low‐Level Jet induces a moisture transport to SESA. This anticyclone is also observed in the absence of ENSO but is weaker. The results suggest the importance of ocean warming in the western Pacific‐Indian in the modulation of extratropical teleconnections to SESA in the tropical ocean warming scenario.

My cave, my rules: Specialization, modularity, and topology of bat‐fly interactions in hot and cold caves from eastern South America

AbstractCaves provide relatively stable and advantageous roosting sites for bats compared to more open roosts, like tree foliage. This environment may have the drawback of facilitating interactions with their ectoparasites due to the confined spaces. Understanding the structure of interactions between bats, acting as hosts, and bat flies, serving as parasites in cave ecosystems, is a crucial first step in deciphering the roles of each species (pullers and pushers) within the networks that form in subterranean ecosystems. Here, we describe and evaluate the network structures of bat‐fly interactions in two distinct cave systems: cold caves (n = 10), also known as bat caves, and hot caves (n = 6). Based on the records of 700 bats from 16 species and 1.412 bat flies from 30 species we uncovered highly distinct topologies comparing hot and cold bat caves that differed also in terms of interactions, specializations, and modularity. We found relatively lower specialization and modularity in hot caves compared to the cold caves, which may be associated to the bat composition and the cave microclimate. Bat flies were highly species‐specific in relation to their bat hosts and dependent on the bats in both hot and cold caves systems. The differences in network structure and at the species level between the bat (cold) and hot caves systems suggest that bat‐fly interactions are shaped by the host species' composition and by the cave system type. Those differences stem from each bat species' adaptation to extreme cave microclimates and their species‐specific roosting behaviors.Abstract in Portuguese is available with online material.

Biomass Burning Aerosol Observations and Transport over Northern and Central Argentina: A Case Study

Biomass Burning Aerosol Observations and Transport over Northern and Central Argentina: A Case Study

The Role of the Subtropical and Extratropical Southern Hemisphere Anomalous Sea Surface Temperature in the Trans‐Seasonal Influence of Southern Annular Mode on Rainfall Over Southeastern South America

AbstractThe current study explores the linkage and possible mechanisms of the Southern Annular Mode (SAM) with rainfall variability over southeastern South America (SESA). The findings indicate that the preceding May SAM can modulate the subsequent rainfall over the SESA region in September‐October‐November (SON), independent of the El Niño‐Southern Oscillation (ENSO) signal. Further analysis suggests that the SAM‐rainfall relationship is mainly due to the response of sea surface temperature (SST) in the subtropical and extratropical Southern Hemisphere to SAM variability via air‐sea interactions. Such SST anomalies persist to the subsequent SON and stimulate an upstream wave train extending into the study region from the South Pacific. Such wave patterns form a cyclone anomaly over SESA, indicating strong subsidence and reduced convection over the region. Meanwhile, the low‐level anomalous cyclone and anticyclone located over the subtropical South Atlantic (on the coast of the study region) are associated with easterly winds to the South (North) of the anomalous cyclone (anticyclone), which advect colder and drier air into the study region due to the cold SST over the subtropical South Atlantic and leading to increased moisture scarcity and decreased rainfall over SESA. Besides, model results based on the joint climate indices (i.e., SAM, ENSO and Indian Ocean Dipole (IOD)) revealed a satisfactory estimate of the SON rainfall compared with either single index, indicating that the SAM can be one of the precursors of the SESA rainfall, besides ENSO and IOD.

A taxonomic revision of Chotoy spinetail Schoeniophylax phryganophilus

Chotoy spinetail Schoeniophylax phryganophilus is widely distributed in southern and eastern South America. What was believed to be a geographically disjunct population was described, as S. p. petersi, from eastern Brazil, in the valley of the Rio São Francisco, in northern Minas Gerais and western Bahia, based on comparatively minor plumage characters (chiefly colour and strength of the streaking). Its range was subsequently believed to extend to the northeast Brazilian state of Piauí. We analysed a total of 91 specimens of Schoeniophylax (74 S. p. phryganophilus, 17 S. p. petersi) for external morphology (plumage and biometrics), and 27 recordings of the species’ main song (22 S. p. phryganophilus and five S. p. petersi). We found no evidence to support intraspecific geographical variation, which is unsurprising in the light of vastly increased fieldwork that has removed any obvious disjunction in the distribution of Schoeniophylax, and we therefore recommend that the species be returned to monotypy.

Ocean waves in the southwestern Atlantic Ocean: An evaluation of global wave models

AbstractIn situ wave observations are essential for implementing coastal management strategies, designing coastal and offshore structures and understanding many processes related to sedimentology and marine biology. Despite their importance, these observations are rather scarce in the coastal areas of southeastern South America. Moreover, the existing observations are discontinuous, with several gaps and no simultaneity. Today, global wave models have improved their performance by providing reliable wave parameters with high resolution and coverage even at near‐shore areas. In this work, wave parameters from five global models were compared with significant wave heights (HS), peak periods (T) and propagation direction at nine sites located at the Southwestern South Atlantic Ocean. The global products used were WAVERYS (Global Reanalysis Wav 001 032), IOWAGA (WAVEWATCH III Hindcast – WW3 – Global grid – CFSR), ERA5 (ECMWF reanalysis), NOAA WW3 – 30‐year Hindcast Phase 2 and NCEP/EMC Operational global wave model GFS – Wave. Mean arithmetic error (Bias), root mean square deviation, scatter index and the Pearson linear correlation coefficient (r) were assessed at each location where wave observations were available. The best agreements for HS were obtained at the deepest sites located farther from the coast. Lower statistical metrics were achieved at coastal sites where the bathymetry is roughly represented by the global models. The calculated correlation coefficients were found to be lower for T than for HS. Overall, T was slightly underestimated by global models. Wave propagation directions were excellently represented by global models at offshore sites. The WAVERYS model is the global product that best represents the wave parameters in the study area, probably due to its higher spatial resolution (0.2°) and more realistic atmospheric forcing (ERA5). In addition, it satisfactorily represents the temporal variability of HS in open water as well as swell characteristics at the outer the Río de la Plata.

Bulk cloud microphysical properties as seen from numerical simulation and remote sensing products: case study of a hailstorm event over the La Plata Basin

Hailstorms develop over the La Plata Basin, in south-eastern South America, more often during later winter and early austral spring, between September and October. These systems have significant socioeconomic impacts over the region. Thus, a better understanding of how atmospheric drivers modulate the formation of hailstorms is important to improve the forecast of such phenomena. In this study, we selected a hailstorm event observed over the eastern La Plata Basin during 14–15 July 2016 to evaluate the performance of the Brazilian developments on the Regional Atmospheric Modelling System (BRAMS) model. The ability of the model in simulating cloud microphysical properties was evaluated by comparing simulations driven by different global forcings against in situ and remote sensing observations. The model results showed good skill in capturing the basic characteristics of the thunderstorm, particularly in terms of the spatial distribution of hydrometeors. The simulated spatial distribution of hail covers locations where hail fall was reported. The BRAMS simulations suggest that, despite relatively low values of the convective available potential energy (CAPE) (700–1000 J kg−1), environments with strong 0–8-km bulk shear (60–70 kt, ~30.9–36.0 m s–1) can promote the formation of ice clouds and hail fall over the eastern La Plata Basin. To be more conclusive, however, further research is needed to understand how different combinations of CAPE and shear affect hail formation over the region.