Pacific Ocean and El Niño/La Niña

Pacific Ocean and El Niño/La Niña

• The Pacific Ocean is the largest and deepest ocean on Earth, with a strong link to the atmosphere. It significantly impacts global weather patterns.
• Trade winds and ocean currents are influenced by the ocean's interaction with the atmosphere.
• Normal Walker Circulation patterns involve easterly winds pushing warm surface water to the western Pacific, creating low pressure. Cold, nutrient-rich water upwells along the eastern Pacific (Peru).
• This difference in water temperature creates a temperature gradient with rising warm air and low pressure in the west. Cooler air sinks and creates high pressure in the east. The layer between warm surface water and cold deep water is called the thermocline.
• Upwelling is the rising of cold, nutrient-rich water from the deep ocean to the surface, typically occurring off the coast of South America.

El Niño

• El Niño is a warming of the central and eastern Pacific Ocean, causing significant global weather changes.
• Tropical easterlies weaken, and warm surface waters flow eastward toward the eastern Pacific.
• Upwelling of cold water is suppressed in the east.
• Lower pressure than normal develops over the eastern and central Pacific.
• Cooler water collects in the western Pacific, leading to less rain.
• Higher pressure than normal develops over the western Pacific.
• This creates wetter conditions over South America and the central Pacific, and drier conditions in the western Pacific.

Extreme El Niño

• Extreme El Niño is the most severe form, with even greater warming and reversed trade wind patterns.
• A stronger reversal of trade wind patterns impacts the movement of warmer and cooler water.
• Greater flooding and drought are observed
• Impacts upwelling of water, leading to less rain or increased rain causing problems like droughts and floods.

La Niña

• La Niña is the cooling of the central and eastern Pacific Ocean.
• Stronger tropical easterlies blow across the Pacific, bringing warm, moist air and warmer surface waters towards the western Pacific.
• Lower pressure than normal over the western Pacific.
• Increased cold water upwells along the eastern Pacific.
• Higher pressure than normal over the eastern Pacific.
• Creates drier conditions over South America and wetter conditions in the western Pacific.

Factors Triggering El Niño and La Niña Events

• Warm ocean waters in the central and eastern Pacific Ocean.
• Atmospheric pressure changes.
• Tropical cyclones.
• Seasonal changes and global patterns.
• Local land and sea interactions.
• Human activities (e.g., burning fossil fuels, cloud seeding).

Effects of El Niño and La Niña

• El Niño: Droughts in Africa (especially maize harvests), stock farmers slaughtering animals to avoid high food costs impacting food security and causing shortages. Decreased fish stocks, and vanishing anchovy catches in Peru due to decreased upwelling
• La Niña: Flooding in South Africa.

The Dipole

• The dipole refers to differences in ocean temperatures between two regions of the Pacific.
• The ENSO dipole has two contrasting poles (eastern and western).
• The eastern Pacific warms up and the western Pacific cools down during El Niño
• The Indian Ocean Dipole (IOD) influences weather patterns in the Indian Ocean region and beyond. Similar to the El Niño-Southern Oscillation (ENSO) in the Pacific Ocean.

Explore the significant impact of the Pacific Ocean on global weather patterns with this quiz. Understand the mechanisms of normal Walker Circulation, upwelling, and the phenomena of El Niño and La Niña. Test your knowledge on how these oceanic processes influence climate variation around the globe.