Which shift occurs in coastal upwelling patterns along South America's western coast during an El Niño event?

💡 Explanation

During El Niño, trade winds weaken and the thermocline deepens along South America's coast, which leads to reduced upwelling because the nutrient-rich cold water from the deep is now further down preventing it to rise. Therefore upwelling weakening results, rather than strengthening, localization or migration of upwelling zones which presuppose sustained pressure gradients and wind forcing.

• Which outcome arises where a low-gradient river encounters localized bank erosion during flood conditions?
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