Analysis: The presence of cooler water can have wider-ranging impacts on global weather patterns

It’s not the first time recently that chilly conditions have gripped parts of southern South America in the lead-up to the southern hemisphere winter. Over the past couple of days, an area of low pressure has positioned itself just south-east of the continent and allowed cold air to filter northwards into southern Chile and Argentina. This process will continue over the coming days with temperatures 5-10 degrees below normal in Argentina from Thursday.

In fact, the western side of South America, including farther north into Peru, has experienced almost perpetually cool conditions of late linked to an ongoing La Niña event in the Pacific Ocean. During these events, which usually occur every few years, sea surface temperatures (SSTs) in the south-eastern Pacific cool significantly as colder waters from the deep upwell to the surface. Current observations suggest SSTs just off the coast of Peru are between 1.5 and 3.5C colder than normal and they have been cooler than normal since last autumn. The presence of cooler water has an often moderating impact on temperatures in South America but can have wider-ranging impacts on global weather patterns too.