Tropical Atlantic mixing changes rules for weather patterns

MADRID, (EUROPA PRESS). – The churning of the upper layers of the Atlantic Ocean plays a crucial role in shaping long-term weather patterns around the world.

Researchers have found that changes in the ocean’s mixed layer (the upper section where wind and waves mix warm surface waters with cooler deep waters) are the main force driving a climate phenomenon known as Atlantic multidecadal variability (AMV) in the tropics, which ranges from 50 to 70 years.

The VMA has far-reaching effects on global climate. It influences weather patterns from North America to Europe and Africa, affecting everything from hurricane activity in the Caribbean to rainfall in the Sahel region.

Dr Balaji Senapati, lead author of the study from the University of Reading, said in a statement: “Until now, it was believed that changes in the exchange of heat between the ocean and the atmosphere determined the climate patterns that affect weather in different parts of the world. Our new study challenges that view, showing that the depth of the ocean’s mixed layer is the key factor in global climate variability.

“This research improves our understanding of Atlantic climate variability and highlights the complex relationship between the ocean and atmosphere in shaping our planet’s climate. Insights into natural climate variability are becoming increasingly valuable for developing effective mitigation strategies as we face the challenges of climate change.”

The study, published in Geophysical Research Letters, found that when the extratropical North Atlantic is warmer than average, the trade winds weaken. This weakening causes the ocean’s mixed layer to become shallower, especially during the summer. As a result, the sun’s energy heats a thinner layer of water, leading to more intense warming of the tropical Atlantic.

This process creates a feedback loop: warmer waters in the northern part of the Atlantic weaken the trade winds, which then leads to a more shallow mixed layer and increased warming in the tropics. When the AMV shifts to its cooler phase, this process is reversed, resulting in cooler temperatures across the Atlantic.

The findings have significant implications for climate modeling and long-term forecasting, according to the authors. Many current climate models may not accurately represent these upper ocean processes, potentially leading to poor predictions of AMV and its global impacts. By incorporating this new understanding of ocean mixing into climate models, scientists hope to improve their ability to forecast long-term climate trends and their associated effects on weather patterns around the world.