Sensitivity of South America Climate to Positive Extremes of Antarctic Sea Ice

Parise, Cláudia Klose; Pezzi, Luciano Ponzi; Carpenedo, Camila Bertoletti; Vasconcellos, Fernanda Cerqueira; Barbosa, Wesley Lima; Lima, Leonardo Gonçalves de

doi:10.1590/0001-3765202220210706

Cited by 3 publications

(1 citation statement)

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“…According to Ciasto and Thompson (2008), large‐scale atmospheric variability in the Southern Hemisphere is mainly driven by two climate variability modes: the Southern Annular Mode (SAM) and the El Niño–Southern Oscillation (ENSO). On an interannual timescale, the interaction between these modes generates SST anomalies in the South Atlantic Ocean that contribute to the South American climate (Andreoli & Kayano, 2006; Parise et al, 2022; Queiroz et al, 2022; Rudeva & Simmonds, 2015; Silva & Ambrizzi, 2006; Torres et al, 2022; Vasconcellos et al, 2022).…”

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confidence: 99%

Warming trends of southwestern Atlantic SST and the summer's warmest SST's impact on South American climate

Vasconcellos

Souza

Dereczynski

et al. 2023

Intl Journal of Climatology

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Several atmospheric variables are directly influenced by oceanic conditions, mainly the sea surface temperature (SST). SST trends and variability over the southwestern Atlantic (SWA) have affected the South American climate, principally the monsoonal period (austral summer). This study analysed the SST trends over the SWA for all seasons. In addition, possible large‐scale triggers of the austral summer's warmest SST over the SWA and the straight impacts of these warmest SSTs on the South American climate were investigated. The results showed a significant positive SST trend of approximately 0.02°C·year−1 over the SWA for all seasons. Since 2000, positive SST anomalies have increased in frequency in all seasons, with the seven warmest summers occurring during the 2010s. The highest SST summers over the SWA have been related to four leading causes: (i) planetary waves triggered by warm anomalies over the subtropical South Pacific; (ii) an omega‐type blocking configuration over the South Atlantic; (iii) a Southern Annular Mode positive phase; and (iv) a strengthening of the Hadley Cell, responding to warm SST over tropical North Atlantic. They all reflected on intensification of the South Atlantic Subtropical High and the western boundary current, heating the SWA. The summer's warmest SST led to positive air temperature anomalies extending in almost all of eastern South America, with significantly highest temperatures over southeastern Brazil, northern Argentina and western Paraguay. Clouds decrease strengthen the incident shortwave in southeastern Brazil, warming the region. Significant reduction of cloudiness and precipitation indicate a low performance of the South Atlantic Convergence Zone. The comparison of the warmest summers in 1980s–1990s in the SWA ratified the role of SST intensification. In conclusion, the positive SST trends over the SWA are related to the summer's warmest SST after 2000s, causing heating and dryness in eastern South America, mainly over southeastern Brazil.

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Section: Introductionmentioning

confidence: 99%

Warming trends of southwestern Atlantic SST and the summer's warmest SST's impact on South American climate

Vasconcellos

Souza

Dereczynski

et al. 2023

Intl Journal of Climatology

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Sea ice in the Weddell Sea and its relationship with the South Atlantic Subtropical High and precipitation in South America

Carpenedo

Ambrizzi

Silva

2022

An. Acad. Bras. Ciênc.

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This study aims to evaluate the position and intensity of the South Atlantic Subtropical High (SASH), related to sea ice extent (SIE) retraction and expansion in the Weddell Sea, assessing precipitation in South America. We assess the difference between atmospheric fi elds related to SIE (four most intense retraction events minus four most intense expansion events) in February. To this end, we used NSIDC SIE, ERA-5 reanalysis, CHIRPS precipitation, ICOADS SST, ONI/SAM indexes (CPC/NOAA). In the following month, under neutral ENSO and SAM, we observed tropospheric warming in the Weddell Sea and cooling in the mid-latitudes South Atlantic. There is a weakening of both the Weddell Sea circumpolar low and the high pressures between tropical and subtropical latitudes, in addition to the equatorward shift of the Ferrel cell. Therefore, SASH weakens and contracts, resulting in a reduction of the tropical Atlantic moisture supply to South America and negative precipitation anomalies in the tropical regions imilar to the suppression pattern of the South Atlantic Convergence Zone. Our results suggest that SIE retraction (expansion) in the Weddell Sea may contribute to the weakening (strengthening) of the SASH and an early-ending (longer-ending) or drierending (wetter-ending) rainy season in tropical South America.

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Anthropocene epoch proposal rejected - does it really matter?

KELLNER

2024

An. Acad. Bras. Ciênc.

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As has reported for some time now, several researchers have embraced the idea that we currently live in a time so different from last centuries that we should separate it into a distinct geological time unit. Specialists who fall under the designation of Earth scientists -such as geologists, paleontologists, and geochemists -divide our planet's geological record expressed in rocks and layers according to events that have had an affect on a global scale. Perhaps the best known is the extinction of non-avian dinosaurs and many other organisms that occurred about 66 million years ago due to the impact of a large meteorite (e.g., Renne et al. 2013). This led to the establishment of the Cretaceous-Paleocene (K-Pg) boundary, revealing two very distinct worlds -one with and one without non-avian dinosaurs, separated by a thin layer with a high concentration of iridium -a chemical element that is very rare on the planet, but abundant in meteorites.The geologic time in which we live is called Holocene, an epoch that began about 11.700 years ago, after the last glaciation (e.g., Walker et al. 2009). At some point, the Dutch environmental chemist Paul Crutzen took up a previous expression used by the American ecologist Eugene Stoermer, the Anthropocene, to make people understand that the current world is quite different from the rest of the Holocene (Crutzen & Stoermer 2000). Just for the sake of fidelity to history, apparently this expression and/or its meaning already existed in the Russian literature before that (e.g., Brookes & Fratto 2020). And the term stuck! Several studies have been published on this subject (e.g., Zalasiewicz et al. 2024), some firmly opposing the idea (e.g., Demos 2017). There have even been periodicals created with what is becoming a popular term, some charging quite hefty fees for open access (e.g., Anthropocene 2024), a problematic issue that will not be addressed here (e.g., Kellner 2023).An interdisciplinary Anthropocene Working Group (AWG) has been established to study this matter in detail and provide a recommendation to the International Commission on Stratigraphy (ICS). The latter is part of the International Union of Geological Sciences (IUGS) and has the responsibility to validate questions and suggestions that might affect the geologic time scale. Contrary to many expectations, this body of scientists has just refused the introduction and formalization of the Anthropocene epoch (IUGS 2024), which has already led to some protests (e.g., Witze 2024).But the question on the minds of many scientists (including geologists like me): does it really matter? Would the "extinction" of the Holocene and the introduction of a new epoch change our perception of the world we live in? There is no doubt that our planet is being affected by the wise species Homo sapiens. Just to stay local, recent examples in Brazil are the collapse of the ALEXANDER W.A. KELLNER EDITORIAL NOTE An Acad Bras Cienc (2024) 96(2) e2024962 2 | 3 How to cite KELLNER AWA. 2024. Anthropocene epoch proposal rejected -does it real...

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Sensitivity of South America Climate to Positive Extremes of Antarctic Sea Ice

Cited by 3 publications

References 58 publications

Warming trends of southwestern Atlantic SST and the summer's warmest SST's impact on South American climate

Warming trends of southwestern Atlantic SST and the summer's warmest SST's impact on South American climate

Sea ice in the Weddell Sea and its relationship with the South Atlantic Subtropical High and precipitation in South America

Anthropocene epoch proposal rejected - does it really matter?

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