IntCal, SHCal, or a Mixed Curve? Choosing a 14C Calibration Curve for Archaeological and Paleoenvironmental Records from Tropical South America

Radiocarbon ◽  
2018 ◽  
Vol 60 (3) ◽  
pp. 925-940 ◽  
Author(s):  
Erik J Marsh ◽  
Maria C Bruno ◽  
Sherilyn C Fritz ◽  
Paul Baker ◽  
José M Capriles ◽  
...  
Keyword(s):  
South America ◽  
Cultural Change ◽  
Calibration Curve ◽  
Substantial Part ◽  
South American ◽  
Lake Titicaca ◽  
Air Masses ◽  
Tree Ring Data ◽  
New Research ◽  
Tropical South America

AbstractBecause the 14C calibration curves IntCal and SHCal are based on data from temperate latitudes, it remains unclear which curve is more suitable for archaeological and paleoenvironmental records from tropical South America. A review of climate dynamics reveals a significant influx of Northern Hemisphere air masses and moisture over a substantial part of the continent during the South American Summer Monsoon (SASM). Areas affected by the SASM receive unknown amounts of input from both hemispheres, where an argument could be made for either curve. Until localized tree-ring data can resolve this, we suggest using a mixed calibration curve, which accounts for inputs from both hemispheres, as a third calibration option. We present a calibration example from a crucial period of environmental and cultural change in the southern Lake Titicaca. Given our current lack of data on past ∆14C variation in South America, our calibrations and chronologies will likely change in the future. We hope this paper spurs new research into this topic and encourages researchers to make an informed and explicit choice of which curve to use, which is particularly relevant in research on past human–environmental relationships.

scholarly journals Transformation and aging of biomass burning carbonaceous aerosol over tropical South America from aircraft in-situ measurements during SAMBBA

2019 ◽  
Author(s):  
William T. Morgan ◽  
James D. Allan ◽  
Stéphane Bauguitte ◽  
Eoghan Darbyshire ◽  
Michael J. Flynn ◽  
...  
Keyword(s):  
South America ◽  
Biomass Burning ◽  
Chemical Properties ◽  
Carbonaceous Aerosol ◽  
Air Masses ◽  
Atmospheric Aging ◽  
Primary Driver ◽  
Tropical South America

Abstract. We present a range of airborne in-situ observations of biomass burning carbonaceous aerosol over tropical South America, including a case study of a large tropical forest wildfire and a series of regional survey flights across the Brazilian Amazon and Cerrado. The study forms part of the South American Biomass Burning Analysis (SAMBBA) Project, which was conducted during September and October 2012. We find limited evidence for net increases in aerosol mass through atmospheric aging combined with substantial changes in the chemical properties of organic aerosol (OA). Oxidation of the OA increases significantly and rapidly on the scale of 2.5–3 hours based on our case study analysis and is consistent with secondary organic aerosol production. The observations of limited net enhancement in OA coupled with such changes in chemical composition, imply that evaporation of OA is also occurring to balance these changes. We observe significant coatings on black carbon particles at source, but with limited changes with aging in both particle core size and coating thickness. We quantify variability in the ratio of OA to carbon monoxide across our study as a key parameter representing both initial fire conditions and an indicator of net aerosol production with atmospheric aging. We observe ratios of 0.075–0.13 μg sm−3 ppbv−1 in the west of our study region over the Amazon tropical forest in air masses less influenced by precipitation and a value of 0.095 μg sm−3 ppbv−1 over the Cerrado environment in the east. Such values are consistent with emission factors used by numerical models to represent biomass burning OA emissions. Black carbon particle core sizes typically range from 250–290 nm, while coating thicknesses range from 40–110 nm in air masses less influenced by precipitation. The primary driver of the variability we observe appears to be related to changes at the initial fire source. A key lesson from our study is that the complex nature of the regional aerosol and its drivers precludes aggregating our observations as a function of atmospheric aging due to the many conflating and competing factors present. Our study explores and quantifies key uncertainties in the evolution of biomass burning aerosol at both nearfield and regional scales. Our results suggest that the initial conditions of the fire are the primary driver of carbonaceous aerosol physical and chemical properties over tropical South America, aside from significant oxidation of OA during atmospheric aging. Such findings imply that uncertainties in the magnitude of the aerosol burden and its impact on weather, climate, health and natural ecosystems most likely lie in quantifying emission sources, alongside atmospheric dispersion, transport and removal rather than chemical enhancements in mass.

scholarly journals South American Climate during the Early Eocene: Impact of a Narrower Atlantic and Higher Atmospheric CO2

2020 ◽  
Vol 33 (2) ◽  
pp. 691-706 ◽  
Author(s):  
Xiaojuan Liu ◽  
David S. Battisti ◽  
Rachel H. White ◽  
Paul A. Baker
Keyword(s):  
South America ◽  
Climate Model ◽  
Atmospheric Composition ◽  
South American ◽  
Early Eocene ◽  
Tropical Atlantic ◽  
State Changes ◽  
Climate Model Simulations ◽  
South American Climate ◽  
Tropical South America

AbstractThe Cenozoic climate of tropical South America was fundamental to the development of its biota, the most biodiverse on Earth. No previous studies have explicitly addressed how the very different atmospheric composition and Atlantic geometry during the early Eocene (approximately 55 million years ago) may have affected South American climate. At that time, the Atlantic Ocean was approximately half of its current width and the CO2 concentration of Earth’s atmosphere ranged from ~550 to ~1500 ppm or even higher. Climate model simulations were performed to examine the effects of these major state changes on the climate of tropical South America. Reducing the width of the Atlantic by approximately half produces significant drying relative to modern climate. Drying is only partly offset by an enhancement of precipitation due to the higher CO2 of the early Eocene. The main mechanism for drier conditions is simple. Low-level air crosses the tropical Atlantic from North Africa in much less time for a narrower Atlantic (2 days) than for the modern Atlantic (~6 days); as a result, much less water is evaporated into the air and thus there is far lower moisture imported to the continent in the Eocene simulation than in the modern control. The progressive wetting (during the mid- to late Cenozoic) of the Amazon due to the widening Atlantic and the rising Andes, only partly offset by decreasing CO2 values, may have been partly responsible for the accumulating biodiversity of this region.

The southernmost fossil record of Squamates

2017 ◽  
Vol 38 (1) ◽  
pp. 15-30 ◽  
Author(s):  
Adriana Albino ◽  
Santiago Brizuela ◽  
Sergio Vizcaíno
Keyword(s):  
South America ◽  
Fossil Record ◽  
Early Miocene ◽  
Substantial Part ◽  
South American ◽  
Santa Cruz ◽  
Origin And Evolution ◽  
Present Distribution ◽  
First Time

Squamates form a substantial part of the present-day South American herpetofauna, and their fossils constitute an indispensable evidence for understanding the origin and evolution of the main taxa. Squamates are relatively common in Miocene localities of Patagonia, especially in levels of the late early Miocene Santa Cruz Formation. In this contribution, remains of the three species of the extinct iguanidErichosaurusAmeghino 1899 (E. diminutus,E. bombimaxillaandE. debilis) are redescribed, and new squamate specimens are reported for first time. The genusErichosaurusis considered invalid.Erichosaurus debilis,E. diminutusand a new specimen are recognized as indeterminate species of the extant polichrotinePristidactylus, whereasE. bombimaxillaremains as an indeterminate iguanid. Snakes are represented by an indeterminate colubrid. All these specimens, together with a tupinambine teiid previously described for the same formation, represent the southernmost fossil record of squamates in South America and indicate the occurrence of the iguanidPristidactylus, the teiidTupinambisand the colubrid snakes south to their present distribution as back as during the early Miocene.

scholarly journals Infection with Mayaro virus in a French traveller returning from the Amazon region, Brazil, January, 2010

2010 ◽  
Vol 15 (18) ◽  
Author(s):  
M C Receveur ◽  
M Grandadam ◽  
T Pistone ◽  
D Malvy
Keyword(s):  
South America ◽  
Amazon Basin ◽  
Amazon Region ◽  
South American ◽  
High Grade ◽  
South American Country ◽  
High Grade Fever ◽  
Mayaro Virus ◽  
Tropical South America

Mayaro virus (MAYV) disease is a mosquito-borne zoonosis endemic in humid forests of tropical South America. MAYV is closely related to other alphaviruses that produce a dengue-like illness accompanied by long-lasting arthralgia. A French tourist developed high-grade fever and severe joint manifestations following a 15-day trip in the Amazon basin, Brazil, and was diagnosed with MAYV infection in January 2010. This case is the first reported in a traveller returning from an endemic South American country to Europe.

Recent changes in the atmospheric circulation patterns during the dry-to-wet transition season in south tropical South America (1979-2020): Impacts on precipitation and fire season

2021 ◽  
pp. 1-56
Author(s):  
Jhan-Carlo Espinoza ◽  
Paola A. Arias ◽  
Vincent Moron ◽  
Clementine Junquas ◽  
Hans Segura ◽  
...  
Keyword(s):  
South America ◽  
Atmospheric Circulation ◽  
Low Frequency ◽  
Fire Season ◽  
South American ◽  
Low Level ◽  
Atmospheric Circulation Patterns ◽  
Transition Season ◽  
Circulation Patterns ◽  
Tropical South America

AbstractWe analyze the characteristics of atmospheric variations over tropical South America using the pattern recognition framework of weather typing or atmospheric circulation patterns (CPs). During 1979-2020, nine CPs are defined in the region, using a k-means algorithm based on daily unfiltered 850 hPa winds over 0035°N-30°S, 90°W-30°W. CPs are primarily interpreted as stages of the annual cycle of the low-level circulation. We identified three “winter” CPs (CP7, CP8 and CP9), three “summer” CPs (CP3, CP4 and CP5) and three “transitional” CPs (CP1, CP2 and CP6). Significant long-term changes are detected during the dry-to-wet transition season (July-October) over south tropical South America (STSA). One of the wintertime patterns (CP9) increases from 20% in the 1980s to 35% in the last decade while the “transitional” CP2 decreases from 13% to 7%. CP9 is characterized by enhancement of the South American Low-Level Jet and increasing atmospheric subsidence over STSA. CP2 is characterized by southerly cold-air incursions and anomalous convective activity over STSA. The years characterized by high (low) frequency of CP9 (CP2) during the dry-to-wet transition season are associated with a delayed South American Monsoon onset and anomalous dry conditions over STSA. Consistently, a higher frequency of CP9 intensifies the fire season over STSA (1999-2020). Over the Brazilian states of Maranhão, Tocantins, Goiás and São Paulo, the seasonal frequency of CP9 explains around 35%-44% of the interannual variations of fire counts.

Empirical ozone production in the subtropical UTLS from South American biomass burning during SOUTHTRAC

2020 ◽  
Author(s):  
Peter Hoor ◽  
Daniel Kunkel ◽  
Hans-Christoph Lachnitt ◽  
Heiko Bozem ◽  
Vera Bense ◽  
...  
Keyword(s):  
South America ◽  
Biomass Burning ◽  
Cross Sections ◽  
Ozone Production ◽  
South American ◽  
Air Masses ◽  
First Results ◽  
Tropopause Region ◽  
Large Fires ◽  
Flight Level

<p>The biomass burning season in America was exceptionally intense during summer 2019. Particularly in the subtropics biomass burning potentially contributes significantly to the trace gas budget of the upper troposphere and can affect chemistry and composition far from the source.</p><p>During the SOUTHTRAC mission, which took place in September and November 2019, several cross sections from the equator to the southern tip of south America were flown at typical altitudes of 13-14 km. During the northbound flight on October, 7<sup>th</sup> 2019 massive enhancements of pollutants were observed at these altitudes. Notably, in-situ observations show continuously elevated CO values exceeding 200 ppbv over a flight distance of more than 1000 km. These massive enhancements were accompanied by largely elevated NO and NO<sub>y</sub> as well as CO<sub>2</sub> and could be attributed to the large fires in South America during this time. Observations of C2H<sub>2</sub> and PAN from GLORIA show, that pollution covered a layer extending from 8-9 km to the flight level at 13 km.</p><p>Comparing the tracer observations to previous flights in exactly the same region three weeks earlier, we could estimate the ozone production due to the biomass burning. Based on first results we estimate ozone production in the polluted air masses up to 30-40 ppbv in the UT which is almost 40% of the observed ozone mixing ratio. Given the large extent of the polluted area over 15 degrees of latitude this may have an impact on the local energy budget of the tropopause region.   </p><p> </p>

South American climatic response to changes in the tropical South Atlantic Ocean hydrography during Termination 1

2020 ◽  
Author(s):  
Karl J. F. Meier ◽  
Andrea Jaeschke ◽  
Julia Hoffmann ◽  
Barbara Hennrich ◽  
Oliver Friedrich ◽  
...  
Keyword(s):  
South America ◽  
High Latitude ◽  
South Atlantic ◽  
Convergence Zone ◽  
South American ◽  
The South ◽  
Low Latitude ◽  
Brazil Current ◽  
South American Climate ◽  
Tropical South America

<p>Rapid climatic reorganizations during the last Termination (i.e. Heinrich Stadials 0-1) had major impacts on the Atlantic Meridional Overturning Circulation (AMOC) strength and on global atmospheric circulation patterns. However, if and how this high-latitude forcing affected low-latitude climate variability is still poorly constrained. Here we present a high-resolution multi-proxy record from marine sediment core M125-3-35 recovered in the western tropical South Atlantic combining foraminiferal Mg/Ca, Ba/Ca ratios, stable oxygen isotope measurements and organic biomarker-based sea surface temperature (SST) proxies (TEX86 and UK’37). The near-shore core position of M125-3-35 off the Paraíba do Sul river mouth in southeastern Brazil and the means of foraminiferal Ba/Ca ratios, which depends on the quantity of continental freshwater input, enables us to investigate direct coupling of continental hydroclimate and oceanographic changes.</p><p>The data show a complex interplay of oceanic and atmospheric forcing dominating the tropical South American climate, which is mainly controlled by the strength and position of the Intertropical Convergence Zone (ITCZ) and South Atlantic Convergence Zone (SACZ). During times of weakest AMOC in Heinrich Stadial 1 (HS1) , a distinct SST peak in the tropical South Atlantic points to an enhanced Brazil Current and strong recirculation of heat within the southern hemisphere. Further, wet conditions prevailed during this time in tropical South America caused by a maximum southward shift of the ITCZ. This happened in coincidence with a temperature drop and weakening of the North Brazil Current (NBC) in the tropical North Atlantic (Bahr et al., 2018) as result of maximum AMOC slowdown. Therefore, for the first time, we reveal a clear seesaw-like pattern of the NBC and BC during times of abrupt AMOC variability.</p><p>While HS1 is generally characterized by a warm and wet anomaly in our record, Ba/Ca ratios and SST show a distinct centennial-scale alternation between warmer (colder) and wetter (drier) phases indicating a distinct climate instability during this climatic phase. A distinct offset exists between SST reconstructed using Mg/Ca, TEX86, and UK’37 which points to strong seasonal differences in the oceanographic settings and/or changes in the terrestrial input from the south American continent. These findings illustrate the strong sensitivity of hydroclimate variability in tropical South America to oceanic forcing as expected also during future climate change, in line with recent studies that showed a severe impact on modern South American climate by changes in (tropical) South Atlantic SSTs (Rodrigues et al., 2019, Utida et al., 2018).</p><p> </p><p>Bahr, A., Hoffmann, J., Schönfeld, J., Schmidt, M. W., Nürnberg, D., Batenburg, S. J., & Voigt, S. (2018). Low-latitude expressions of high-latitude forcing during Heinrich Stadial 1 and the Younger Dryas in northern South America. <em>Global and Planetary Change, 160</em>, 1-9.</p><p>Rodrigues, R. R., Taschetto, A. S., Gupta, A. S., & Foltz, G. R. (2019). Common cause for severe droughts in South America and marine heatwaves in the South Atlantic. <em>Nature Geoscience, 12</em>(8), 620-626.</p><p>UTIDA, Giselle, et al. Tropical South Atlantic influence on Northeastern Brazil precipitation and ITCZ displacement during the past 2300 years. <em>Scientific reports</em>, 2019, 9. Jg., Nr. 1, S. 1698.</p>

scholarly journals Tropical South America–Atlantic Sector Convective Margins and Their Relationship to Low-Level Inflow

2010 ◽  
Vol 23 (10) ◽  
pp. 2671-2685 ◽  
Author(s):  
Benjamin R. Lintner ◽  
J. David Neelin
Keyword(s):  
South America ◽  
Convection Zone ◽  
Precipitable Water ◽  
Distribution Functions ◽  
Back Trajectory ◽  
Atlantic Sector ◽  
Air Masses ◽  
Northern Margin ◽  
Low Level ◽  
Tropical South America

Abstract The edges or margins of tropical convective zones are hypothesized to be sensitive to low-level inflow conditions. The present study evaluates where and to what extent convective margin variability is sensitive to low-level inflow variability using observed precipitation and reanalysis wind and total precipitable water data over the tropical South America–Atlantic sector in austral summer. Composite analysis based on an inflow measure defined by projecting low-level monthly-mean atmospheric boundary layer (ABL) or lower free troposphere (LFT) winds onto either mean horizontal precipitation or precipitable water gradients shows widespread contraction of the edges of convection zones in the direction of stronger convection for anomalously strong low-level inflow; such behavior is consistent with enhanced import of relatively dry air along the edges of convection zones. However, the distinction between ABL and LFT winds may be significant regionally, for example, along the Atlantic ITCZ’s northern margin. Back trajectory analysis is employed to estimate source regions of low-level air masses arriving at margin points over time scales (2–4 days) during which low-level air masses are expected to retain some memory of initial moisture conditions while also undergoing diabatic modification. Probability distribution functions of mean precipitation values encountered along trajectories facilitate objective quantification of the frequency with which trajectories approach the margin from drier areas outside the convection zone. While margin points in the ABL are strongly dominated by inflow (i.e., trajectories originating outside of the convection zone), points in the LFT may show inflow, outflow, or mixed inflow–outflow conditions. LFT locations dominated by inflow trajectories generally correspond to regions with composites exhibiting the clearest signatures of LFT wind variability on precipitation.

A new species of Archaebranchinecta (Anostraca: Branchinectidae) from the South American Altiplano

Zootaxa ◽  
2019 ◽  
Vol 4683 (1) ◽  
pp. 55-83 ◽  
Author(s):  
ROSA GRACIELA COHEN ◽  
MARÍA CRISTINA MARINONE ◽  
SARAH J. ADAMOWICZ
Keyword(s):  
New Species ◽  
South America ◽  
South American ◽  
Morphological Comparison ◽  
Lake Titicaca ◽  
Basal Segment ◽  
Genital Segment ◽  
Western Shore ◽  
A New Species ◽  
Male Genital

A detailed morphological comparison was carried out among specimens of several samples of Archaebranchinecta Rogers & Coronel, 2011 from the Altiplano of Peru, Bolivia, and Argentina. Surprisingly, striking differences were found between Peruvian samples collected near the western shore of Lake Titicaca, and those from Bolivia taken southwardly, near the east coasts of River Desaguadero and Lake Poopó. Accordingly, the new species Archaebranchinecta aimara sp. nov. is described, representing the second specific entity of a genus that so far included only A. pollicifera (Harding, 1940). The main differential features between both species include: (a) size and shape of the three processes of basal segment of the male second antenna; (b) shape and protrusion degree of the pair of medioventral bulges in the male genital segments; (c) presence or absence of strong ventrolateral spine on the second genital segment of female; and (d) presence or absence of a pair of ventrolateral outgrowths in the brood pouch. This research contributes to our understanding of the biodiversity and endemism of the unique Altiplano region of South America. 

scholarly journals The influence of volcanic eruptions on the climate of tropical South America during the last millennium in an isotope-enabled general circulation model

2016 ◽  
Vol 12 (4) ◽  
pp. 961-979 ◽  
Author(s):  
Christopher M. Colose ◽  
Allegra N. LeGrande ◽  
Mathias Vuille
Keyword(s):  
South America ◽  
Oxygen Isotope ◽  
Southern Oscillation ◽  
Volcanic Eruptions ◽  
Hydrologic Cycle ◽  
South American ◽  
Last Millennium ◽  
Continental Scale ◽  
The Impact ◽  
Tropical South America

Abstract. Currently, little is known on how volcanic eruptions impact large-scale climate phenomena such as South American paleo-Intertropical Convergence Zone (ITCZ) position and summer monsoon behavior. In this paper, an analysis of observations and model simulations is employed to assess the influence of large volcanic eruptions on the climate of tropical South America. This problem is first considered for historically recent volcanic episodes for which more observations are available but where fewer events exist and the confounding effects of El Niño–Southern Oscillation (ENSO) lead to inconclusive interpretation of the impact of volcanic eruptions at the continental scale. Therefore, we also examine a greater number of reconstructed volcanic events for the period 850 CE to present that are incorporated into the NASA GISS ModelE2-R simulation of the last millennium. An advantage of this model is its ability to explicitly track water isotopologues throughout the hydrologic cycle and simulating the isotopic imprint following a large eruption. This effectively removes a degree of uncertainty associated with error-prone conversion of isotopic signals into climate variables, and allows for a direct comparison between GISS simulations and paleoclimate proxy records. Our analysis reveals that both precipitation and oxygen isotope variability respond with a distinct seasonal and spatial structure across tropical South America following an eruption. During austral winter, the heavy oxygen isotope in precipitation is enriched, likely due to reduced moisture convergence in the ITCZ domain and reduced rainfall over northern South America. During austral summer, however, more negative values of the precipitation isotopic composition are simulated over Amazonia, despite reductions in rainfall, suggesting that the isotopic response is not a simple function of the "amount effect". During the South American monsoon season, the amplitude of the temperature response to volcanic forcing is larger than the rather weak and spatially less coherent precipitation signal, complicating the isotopic response to changes in the hydrologic cycle.

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