Which mechanism causes increased coastal upwelling during La Niña conditions?

💡 Explanation

During La Niña, stronger easterly trade winds increase the pressure gradient because of the intensified Walker circulation, leading to greater Ekman transport and upwelling along the western coast of South America. Therefore enhanced trade wind pressure results, promoting upwelling, rather than changes in thermohaline fronts, meltwater impact or gyre circulation, which have different primary drivers.

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