The Azores anticyclone, the high pressure system over the Atlantichas expanded like never before in the last 1,200 years, a situation that is causing the driest conditions in the Iberian Peninsula for more than eight centuries and for which human beings are responsible.
According to research published Monday in the journal Nature Geoscience, its area is expected to continue to increase in the 21st century as greenhouse gas levels rise and this could lead to a high risk of drought.
“Article: The Azores High over the North Atlantic has expanded due to anthropogenic climate change, disrupting precipitation patterns in western Europe https://t.co/uqnLhw4kWE@WHOI pic.twitter.com/8zKLNXZDzb“
— Nature Geoscience (@NatureGeosci) July 4, 2022
The changes, they noted, “unprecedented in the last millennium” and affect the climate of Western Europe, as the Azores are also known as the “guardian” of European rainfall. Specifically, will intensify the drought in Spain and Portugal with a 10 to 20% drop in winter rainfall over the next century.
The anticyclone began to expand along with the growth of human emissions of greenhouse gases 200 years ago, but its increase was accentuated in the 20th century, which is consistent with a anthropogenic warming.
The Azores, key to the climate of the Iberian Peninsula
Weather and long-term climate patterns in Western Europe are strongly affected by the atmospheric circulation associated with that high-pressure area, which rotates clockwise around North Africa, the US East Coast, and the United States. USA and Western Europe.
The dry air that descends towards the surface within the system is one of the main causes of hot and arid summers in much of Portugal and Spain, as well as in the western Mediterranean in general.
During the typically wetter winter months, changes in the position of the Azores anticyclone are responsible for the westerly windsdisplacing moisture towards the Iberian Peninsula, but these winter rains have decreased in recent decades.
This decrease in rainfall, according to experts, is linked to the expansion of the anticyclone. The team, led by American scientists from the Woods Hole Oceanographic Institution, has discovered this by developing and comparing various models of its size and spatial extent with geochemical indicators of past precipitation levels preserved in Portuguese stalagmites, dating back to the year 850.
Observations and simulations have indicated that winters with an “extremely large” Azores anticyclone are significantly most common in the industrial age (approximately 1850) than in the pre-industrial period, resulting in “anomalous dry conditions” throughout the western Mediterranean, including the Iberian Peninsula. According to the study, an extreme winter every 10 years in the pre-industrial period has gone to one every four years in the 21st century.