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

Abstract

The cold air incursion over South America is associated with the frontal systems generated in the Antarctic region, and sea ice cover plays an important role in its formation. Little is known about how the high‐frequency variability of the coupled ocean–cryosphere‐atmosphere system affects weather conditions in South America, especially in the Amazon region ‐ in tandem with the largest tropical forest on the planet and a key region of the global climate system. The results presented here suggest that the high‐frequency variability of the expansion of Antarctic sea ice extent (SIE) extremes, in the Ross Sea and Indian Ocean, modulate the cold air incursion over the Amazon in the southern winter 4 and 2 days after the expansion of SIE extremes, respectively. The SIE extremes can couple with the atmosphere, inducing Rossby waves that propagate and undergo amplification downstream from the Ross Sea and Indian Ocean during such extremes. In this way, the atmospheric wave train acquires a more southern spread over South America, reaching tropical latitudes after the SIE extremes. In non‐SIE extreme periods, the atmospheric wave train has a more zonal spread and reaches only the extratropical latitudes of the continent.

Atmospheric circulation patterns associated with surface air temperature variability trends between the Antarctic Peninsula and South America

“…Extreme weather events significantly influence highly productive agricultural regions in South America. Polar air masses affect the continent´s weather and climate, through the abrupt drop in its air temperature (Ricarte et al 2015, Lanfredi & Camargo 2018, Carpenedo et al 2022, severe frost formations and occasional snow, which results in agricultural productivity losses (Marengo et al 1997). These systems can trigger not only cold events, but also warm events (Rusticucci & Vargas 1995).…”

“…The asymmetrical orography of the Antarctic continent in relation to the geographic South Pole favors Rossby wave formations. These modify the structure of the high-level flow and modulate the characteristics of transient systems, consequently affecting mid and low-latitude atmospheric circulation (Pezza et al 2008, Carpenedo et al 2022. Rossby waves originate at the contact zone, between cold polar air and relatively warm air at midlatitudes, which is modulated by the polar jet stream.…”