Abrupt variations in South American monsoon rainfall during the Holocene based on a speleothem record from central-eastern Brazil

Geology ◽  
2011 ◽  
Vol 39 (11) ◽  
pp. 1075-1078 ◽  
Author(s):  
N. M. Strikis ◽  
F. W. Cruz ◽  
H. Cheng ◽  
I. Karmann ◽  
R. L. Edwards ◽  
...  
Keyword(s):  
Monsoon Rainfall ◽  
South American ◽  
The Holocene ◽  
South American Monsoon ◽  
Eastern Brazil ◽  
Central Eastern

scholarly journals A high-resolution history of the South American Monsoon from Last Glacial Maximum to the Holocene

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Valdir F. Novello ◽  
Francisco W. Cruz ◽  
Mathias Vuille ◽  
Nicolás M. Stríkis ◽  
R. Lawrence Edwards ◽  
...  
Keyword(s):  
High Resolution ◽  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
South American ◽  
The South ◽  
The Holocene ◽  
South American Monsoon ◽  
Last Glacial ◽  
History Of ◽  
History Of The South

The joint impacts of Atlantic and Pacific multidecadal variability on South American precipitation and temperature

2021 ◽  
pp. 1-55
Author(s):  
Zhaoxiangrui He ◽  
Aiguo Dai ◽  
Mathias Vuille
Keyword(s):  
South America ◽  
The Other ◽  
South American ◽  
Atlantic Multidecadal Variability ◽  
Multidecadal Variability ◽  
Temperature Anomalies ◽  
Central Brazil ◽  
Eastern Brazil ◽  
Precipitation Anomalies ◽  
Central Eastern

AbstractSouth American climate is influenced by both Atlantic multidecadal variability (AMV) and Pacific multidecadal variability (PMV). But how they jointly affect South American precipitation and surface air temperature is not well understood. Here we analyze composite anomalies to quantify their combined impacts using observations and reanalysis data. During an AMV warm (cold) phase, PMV-induced JJA precipitation anomalies are more positive (negative) over 0°-10°S and southeastern South America, but more negative (positive) over the northern Amazon and central Brazil. PMV-induced precipitation anomalies in DJF are more positive (negative) over Northeast Brazil and southeastern South America during the warm (cold) AMV phase, but more negative (positive) over the central Amazon Basin and central-eastern Brazil. PMV’s impact on AMV-induced precipitation anomalies shows similar dipole patterns. The precipitation changes result from perturbations of the local Hadley and Walker Circulations. In JJA, PMV- and AMV-induced temperature anomalies are more positive (negative) over entire South America when the other basin is in a warm (cold) phase, but in DJF temperature anomalies are more positive (negative) only over the central Andes and central-eastern Brazil and more negative (positive) over southeastern South America and Patagonia. Over central Brazil in JJA and southern Bolivia and northern Argentina in DJF, the temperature and precipitation anomalies are negatively correlated. Our results show that the influence of Pacific and Atlantic multidecadal variability need to be considered jointly, as significant departures from the mean AMV or PMV fingerprint can occur during a cold or warm phase of the other basin’s mode.

scholarly journals Late Quaternary Variations in the South American Monsoon System as Inferred by Speleothems – New Perspectives Using the SISAL Database

2018 ◽  
Author(s):  
Michael Deininger ◽  
Brittany Marie Ward ◽  
Valdir F. Novello ◽  
Francisco W. Cruz
Keyword(s):  
South America ◽  
Time Scales ◽  
Late Pleistocene ◽  
Convergence Zone ◽  
South American ◽  
The South ◽  
The Holocene ◽  
South American Monsoon ◽  
Monsoon System ◽  
South American Monsoon System

Here we present an overview of speleothem δ18O records from South America, which mostly are available in the Speleothem Isotopes Synthesis and Analysis (SISAL_v1) database. South American tropical and subtropical δ18O time series are primarily interpreted as being driven by the amount effect and, consequently show the past history of the convection intensity of convergence zones such as the Intertropical Convergence Zone and the South America Monsoon System. We investigate past hydroclimate scenarios in South America related to the South American Monsoon System in three different time scales: Late Pleistocene, Holocene and the last two millennia. The precession driven insolation is the main driver of convective variability over the continent during the last 250 kyrs, including the Holocene period. However a dipole is observed between the west and east portions of the continent. Records located in the central region of Brazil appear to be weakly affected by insolation driven variability and more susceptible to the South Atlantic Convergence Zone. Cold episodic events in Northern Hemisphere increase the activity of the South American Monsoon System on all time scales, in turn increasing rainfall amounts in South America, as was documented during Heinrich events in the late Pleistocene and Bond events in the Holocene, as well as during the Little Ice Age.

scholarly journals Interannual Variability and Seasonal Evolution of Summer Monsoon Rainfall in South America

2009 ◽  
Vol 22 (9) ◽  
pp. 2257-2275 ◽  
Author(s):  
Alice M. Grimm ◽  
Marcia T. Zilli
Keyword(s):  
South America ◽  
Interannual Variability ◽  
Monsoon Rainfall ◽  
The South ◽  
Eastern Brazil ◽  
Second Mode ◽  
Rainfall Anomalies ◽  
Central Eastern ◽  
The Impact ◽  
Peak Summer

Abstract The analysis of the interannual variability of the South American monsoon rainfall is carried out separately for austral spring and summer (and for November and January), based on a 40-yr station gauge dataset. Relationships between modes of variability in these seasons show the influence of antecedent conditions in spring (or November) on the evolution of the monsoon rainfall in peak summer (or January). In spring the first mode is dipolelike, with opposite loadings over central-eastern and southeastern South America. It is connected with ENSO. The second mode shows the highest loadings slightly south of the South Atlantic convergence zone. The leading mode of summer also features dipolelike oscillations between central-eastern and southeastern South America, but is not strongly connected with ENSO. The second mode represents the impact of ENSO, and the third is modulated by SST anomalies in the southern tropical Atlantic. Significant relationships are disclosed between the first dipolelike modes of spring and summer rainfall and thus between the rainfall in spring and summer over central-eastern South America, which includes part of the monsoon core region. These dipolelike modes are associated with a rotational anomaly over southeast Brazil that either conveys moisture flux into central-eastern Brazil (if it is cyclonic) or into southeastern South America (if it is anticyclonic). In spring this anomaly seems to be remotely forced, but after strong rainfall anomalies over central-eastern Brazil in spring, it tends to reverse sign in peak summer, inverting the dipolelike rainfall anomalies. This reversal is hypothesized to be locally forced by surface–atmosphere feedback triggered by the spring anomalies, as weaker teleconnections in summer allow local processes that are stronger in summer to overcome remote forcing. SST and circulation anomalies associated with the first modes in spring and summer, and also the relationship between the first summer mode and surface temperature in spring, are consistent with that hypothesis.

scholarly journals Speleothem records of monsoon interannual-interdecadal variability through the Holocene

2021 ◽  
Author(s):  
Sarah Parker ◽  
Sandy P Harrison ◽  
Pascale Braconnot
Keyword(s):  
Climate Model ◽  
East Asian Monsoon ◽  
East Asian ◽  
Regional Scale ◽  
Interdecadal Variability ◽  
Global Network ◽  
South American ◽  
Monsoon Region ◽  
The Holocene ◽  
South American Monsoon

Abstract Modern observations show considerable interannual to interdecadal variability in monsoon precipitation. However, there are few reconstructions of variability at this timescale through the Holocene, and there is therefore less understanding of how changes in external forcing might have affected monsoon variability in the past. Here, we reconstruct the evolution of the amplitude of interannual to interdecadal variability (IADV) in the East Asian, Indian and South American monsoon regions through the Holocene using a global network of high-resolution speleothem oxygen isotope (δ18O) records. We reconstruct changes in IADV for individual speleothem records using the standard deviation of δ18O values in sliding time windows after correcting for the influence of confounding factors such as variable sampling resolution, growth rates and mean climate. We then create composites of IADV changes for each monsoon region. We show that there is an overall increase in δ18O IADV in the Indian monsoon region through the Holocene, with an abrupt change to present-day variability at ~2 ka. In the East Asian monsoon, there is an overall decrease in δ18O IADV through the Holocene, with an abrupt shift also seen at ~2 ka. The South American monsoon is characterised by large multi-centennial shifts in δ18O IADV through the early and mid-Holocene, although there is no overall change in variability across the Holocene. Our regional IADV reconstructions are broadly reproduced by transient climate-model simulations of the last 6 000 years. These analyses indicate that there is no straightforward link between IADV and changes in mean precipitation, or between IADV and orbital forcing, at a regional scale.

Onset and demise dates of the rainy season in the South American Monsoon region: a cluster analysis result

2021 ◽  
Author(s):  
Maria A. M. Rodrigues ◽  
Sâmia R. Garcia ◽  
Mary T. Kayano ◽  
Alan J. P. Calheiros ◽  
Rita V. Andreoli
Keyword(s):  
Cluster Analysis ◽  
Rainy Season ◽  
South American ◽  
Monsoon Region ◽  
The South ◽  
South American Monsoon

scholarly journals Regionally extinct species rediscovered: the bush dog Speothos venaticus in Minas Gerais, south-eastern Brazil

Oryx ◽  
2014 ◽  
Vol 49 (1) ◽  
pp. 60-63 ◽  
Author(s):  
Guilherme Braga Ferreira ◽  
Marcelo Juliano Rabelo Oliveira ◽  
Rogério Cunha de Paula ◽  
Flávio Henrique Guimarães Rodrigues ◽  
Érica Daniele Cunha Carmo
Keyword(s):  
Protected Areas ◽  
Minas Gerais ◽  
The State ◽  
South American ◽  
North West ◽  
South Eastern ◽  
The North ◽  
Eastern Brazil ◽  
Bush Dog ◽  
Speothos Venaticus

AbstractThe bush dog Speothos venaticus, a rare Near Threatened South American canid that lives in packs, was thought to be extinct in Minas Gerais state, south-eastern Brazil, until recently. Here, we report four recent records of the species in Minas Gerais, the first in the state since the description of the species in 1842. All records are from the Cerrado ecosystem in the north and north-west of the state; two are from animals found dead, one from footprints and another from a camera trap. Three of the records were inside or close (< 10 km) to strict protected areas, in a region recognized as the Protected Areas Mosaic Sertão Veredas–Peruaçu, where we expect any new records of the bush dog to be found. We discuss the low probability of detecting the bush dog and the main regional threats to the species, and emphasize the need to protect large and interconnected natural areas and keep them free of domestic dogs to avoid the extinction of the bush dog in Minas Gerais.

Reconstruction of the last three millennia South American Monsoon variability over the Amazon basin using speleothem isotope records 

2021 ◽  
Author(s):  
Marcela Eduarda Della Libera de Godoy ◽  
Valdir F. Novello ◽  
Francisco William Cruz
Keyword(s):  
High Resolution ◽  
Amazon Basin ◽  
Rainfall Variability ◽  
Isotope Analysis ◽  
Core Region ◽  
South American ◽  
The South ◽  
Continuous Increase ◽  
South American Monsoon ◽  
The Core

&lt;p&gt;South American Monsoon System (SAMS) and its main feature, the South American Convergence Zone (SACZ) are responsible for the major distribution of moisture in South America. The current work presents a novel high-resolution oxygen isotope record (&amp;#948;&lt;sup&gt;18&lt;/sup&gt;O) based on speleothems from southwest Amazon basin (Brazil), right at SAMS' core region and SACZ onset, where there is still a gap of high resolution paleoclimate records. The novel &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O&amp;#160;record presents an average of 3 year-resolution, composed by 1344 stable isotope analysis performed in two speleothems with a well-resolved chronology (37 U/Th ages) with average errors &lt;1%. This work aims to describe the rainfall variability of the core region of the South American monsoon for the last 3k years and to take a broader look at precipitation patterns over Amazon basin. The Rond&amp;#244;nia &amp;#948;18O record shows three main stages throughout this time period. The first is from -1000 to ~400 CE, where it&amp;#8217;s in accordance with most of other paleorecords from the Amazon basin. the second segment &amp;#160;is from ~400 to 1200 CE, when there is a continuous increase in the &amp;#948;18O record until it reaches its highest values around 850 CE during the MCA (800-1200 CE), which is in accordance with western Amazon records, whilst the record in eastern Amazon presents an opposite trend. Thus, a precipitation dipole over Amazon emerges from ~400 CE onwards, majorly triggered by anomalous climate changes such as MCA, where western (eastern) Amazon is drier (wetter). During LIA (1450-1800 CE), on the other hand, Rond&amp;#244;nia record presents its lowest values, also agreeing with western records and with records under the influence of SACZ whilst on eastern Amazon a drier period is established. Therefore, with this novel paleoclimate record located at the core region of SAMS, it's possible to evidence the dynamics of the precipitation dipole over the Amazon region, as well as understand the SACZ intensity variations.&lt;/p&gt;

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