Download El Niño

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.
So what is the reason behind this alarming drought situation?
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.
Frequency of El Niño
• An El Niño occurs about every three to eight years
3-Day Temperature Loop
In the tropical Pacific, winds drive the surface waters westward
The surface water becomes
warmer going westward
because of its longer
exposure to the sun’s
heating.
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%