Células de Circulação Meridional Durante os Eventos Extremos de Gelo Marinho Antártico

Abstract

ResumoComo a borda do gelo marinho antártico está localizada em uma região muito sensível, sob a Frente Polar Antártica, existe um grande potencial da variabilidade do gelo marinho afetar a circulação atmosférica. Assim, o objetivo deste estudo foi investigar as possíveis relações entre os eventos extremos de gelo marinho antártico e as células de circulação meridional no Pacífico Sudeste, região onde há intensa variabilidade em várias escalas de tempo. Os resultados mostram que quando há eventos extremos de expansão de gelo marinho no setor do mar de Ross, existe um resfriamento da TSM, que resulta em uma atmosfera adjacente fria, aumentando os gradientes térmicos entre a borda do gelo marinho e a região de mar aberto. Os gradientes de pressão são fortalecidos, fortalecendo o cinturão circumpolar de baixas pressões e o jato polar. Assim, existe um fortalecimento do ramo ascendente da célula de Ferrel sobre o Oceano Austral, enquanto há enfraquecimento nas latitudes médias, por conservação de massa. Observamos o padrão oposto em eventos extremos de retração de gelo marinho no setor do mar de Ross e expansão no setor do mar de Weddell. Palavras-chave: células de circulação meridional, gelo marinho, variabilidade interanual. Cells of Meridional Circulation During the Extreme Events of Antarctic Sea Ice AbstractBecause the Antarctic sea ice edge is located in a region quite sensible, under the Antarctic Polar Front, there is a great potential of sea ice variability to affect the atmospheric circulation. The objective of this study was to investigate possible relationships between the extreme events of Antarctic sea ice and the cells of meridional circulation over the Southeastern Pacific, where there is intense climate variability on various time scales. The results show that when there are extreme events of sea ice expansion in the Ross Sea sector there is cooling of the SST, which results in the surrounding atmosphere cools, increasing the thermal gradient between the edge of sea ice and the open water region. The southern pressure gradients are strengthened, which strengthens the circumpolar low pressure belt and the polar jet. So there is a strengthening of the ascending branch of the Ferrel cell over the Southern Ocean while there is a weakening in midlatitudes via conservation of mass. We observe the opposite pattern in extreme events of sea ice decrease in the Ross Sea sector and expansion in the Weddell Sea sector.

Combined performance of September’s Weddell sea ice extent, Southern Annular Mode, and Atlantic SST anomalies over the South American temperature and precipitation

“…Climate links between the Antarctic sea ice (ASI) extremes, the atmospheric circulation, and the climate of South America have been intensely investigated in the last decades due to the importance of ASI in the balance of the global climate system by controlling the atmospheric circulation in Southern Hemisphere (Carvalho et al 2005, Lefebvre & Goosse 2005, Pezza et al 2008, 2012, Reboita et al 2009, Silvestri & Vera 2009, Parise et al 2015, Carpenedo & Ambrizzi 2016, Oliva et al 2021. This significant impact of ASI on the climate of the Southern Hemisphere occurs since the atmosphere functions as a heat engine, characterized by excessive heating in the tropics and cooling in the high latitudes (Raphael et al 2011, Carpenedo & Ambrizzi 2016. Antarctica represents an excellent heat sink for the planet and the Southern Hemisphere, controlling atmospheric circulation in the middle and high latitudes.…”

“…The ASI variability modulates the Equator-to-Pole temperature gradients, changing the southern heat transport and consequently the local, regional, and global climate (Carpenedo et al 2013, Parise et al 2015, Carpenedo & Ambrizzi 2016, Morioka et al 2017. Some studies have shown the complexity and the relevance of the cryosphere-atmosphere interactions (Hall & Visbeck 2002, Cunningham & Bonatti 2011, Raphael et al 2011, Parise et al 2015, Lima & Carvalho 2017.…”

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

“…However, the impact of ASI changes on the southern atmosphere is not confined to the lower troposphere, where ocean fluxes heat it, but also extend to medium and high levels of the troposphere (e.g., Cunningham & Bonatti 2011, Raphael et al 2011, Parise et al 2015. In addition, the variability of ASI modulates the Equator-to-Pole temperature gradients, changing the southern heat transport and consequently the local, regional and global climate (Carpenedo et al 2013, Parise et al 2015, Carpenedo & Ambrizzi 2016.…”

The high‐frequency variability of Antarctic sea ice and polar cold air incursions over Amazonia

“…This weakens the Southern Hemisphere's storm tracks and shifts the polar jet northward. Thus, the polar cell expands and weakens, and the Ferrel cell is shifted north (Raphael et al, 2011), affecting the position of the Subtropical Highs (Carpenedo and Ambrizzi, 2016) and the density and position of transient systems (Watkins and Simmonds, 1995;Godfred-Spenning and Simmonds, 1996;Menéndez et al, 1999aMenéndez et al, , 1999bPezza et al, 2008) in the Southern Hemisphere.…”