El Niño - Southern Ocean Oscillation. El Niño-Southern Oscillation is a periodic change in the atmosphere and ocean of the tropical Pacific region. El.

El Niño - Southern Ocean Oscillation

• El Niño-Southern Oscillation is a periodic change in the atmosphere and ocean of the tropical Pacific region. El Niño is the warm phase La Niña is the cold phase

ENSO

ENSO is associated with floods, droughts and other weather disturbances in many regions of the world.

Blame it on the weather phenomenon called El Nino. And it's not just India, countries across the world will enter a rough and dry patch.

So what is the reason behind this alarming drought situation?

Frequency of El Niño

• An El Niño occurs about every three to eight years

3-Day Temperature Loop

The surface water becomes warmer going westward because of its longer exposure to the sun’s heating.

In the tropical Pacific, winds drive the surface waters westward

El Niño

• El Niño occurs when the easterly trade winds weaken, allowing warmer waters of the western Pacific to migrate eastward and eventually reach the South American Coast.

normal El Nino

cold, nutrient-rich surface water, normally found along the coast of Peru

Nutrient rich

El Niño's warm current of nutrient-poor tropical water, replaces the cold, nutrient-rich surface water, normally found along the

coast of Peru

Nutrient poor

Upwelling and Downwelling

• westward-flowing, wind-driven surface currents near the equator turn northward on the north side of the equator and southward on the south side.

• surface waters are moved away from the equator and replaced by upwelling waters.

surface waters move away from the coast and are replaced by water that wells up from below.

surface waters move toward the coast, the water piles up and sinks

Coastal upwelling in the Peruvian Current System makes the coastal water nutrient-rich.

El Niño and La Niña Mix Up Plankton Populations

•

• nutrient transport into the surface waters where sunlight, is present, results in rapid growth of phytoplankton, the base of marine food webs

Great Fishing!

• The world's most productive fisheries are located in areas of coastal upwelling that bring cold nutrient rich waters to the surface

• El Niño was named by Peruvian fishers who noticed that the warming of ocean surface waters reduced their anchovy catch.

Upwelling and downwelling influence sea-surface temperature and biological productivity

upwelling waters are usually rich in the dissolved nutrients, nitrogen and phosphate compounds, required for phytoplankton growth.

about half the world's total fish catch comes from upwelling zones

• There is an abundance of marine life in these areas. The upwelling regions constitute about one percent of the surface of the ocean, yet they account for 50 percent of the fisheries catch worldwide!

When El Niño conditions last for many months, ocean warming occurs resulting in serious economic impact to local fishing. There is a dramatic reduction in marine fish and plant life.

Peruvian Anchovy Effect

• Alternate upwelling of nutrient poor and nutrient rich waters off the coast of Ecuador and Peru are associated with El Niño and La Niña episodes.

• During El Niño the pycnocline is so deep that the upwelled waters come from the nutrient poor waters above the pycnocline.

• In extreme cases, nutrient-deficient waters coupled with over-fishing cause fisheries to collapse bringing about severe, extended economic impacts.

Peruvian Anchovy Effect

• Upwelled systems of the ocean are cold areas high in nutrients and productivity. – large marine fisheries develop there.

• During an El Niño, upwelling decreases, the thermocline lowers, and the warmer water near the surface lacks the nutrients found during cold conditions.

Peruvian Anchovy Effect

• Beginning in the 1950s, an important anchovy fishing industry developed and grew in Peru, due to the huge numbers of anchovies that lived in the areas of cold, nutrient-rich waters welling up off the Peruvian coast.

• By 1971, the Peruvian anchovy harvest had climbed to 12.5 million tons per year.

• in 1972, an El Niño year, the anchovy stocks declined sharply. Only 2.5 million tons were harvested that year, leading to great economic hardship and a virtual collapse of the Peruvian fishing industry.

Peruvian Anchovy Effect

• The decrease in the anchovy population triggered a series of interrelated problems. – much of the anchovy catch is processed into fishmeal.

• During the growth years of the Peruvian fishing industry, the fishmeal had become a major source of feed for livestock and poultry around the world.

• When the anchovy catch collapsed in 1972, nations around the world that had become dependent on the fishmeal had to find other, more expensive, sources of feed. – This caused meat prices to rise. In the United States, poultry prices

rose more than 40%