El Niño

by Sarah Koteen

What is El Niño?

•It means young child in Spanish!

But with weather:

•El Niño is a “major climate force around the world that is an oscillation of the ocean-atmosphere system in the tropical Pacific having important consequences for weather…”-National Oceanic and Atmospheric Administration (NOAA)

NORMAL CONDITIONS IN THE PACIFIC

www.kidsgeo.com/images/pacific-ocean.jpg

The East Australian Current

Controls:• Most tropical

precipitation• Position of

the Jet Stream

http://squall.sfsu.edu/gif/jetstream_pac_init_00.gif

The Western Pacific (Australian

areas)• Typically the western

tropical pacific is the warmest area in the global ocean

• sea surface temperatures at 30°C, about 8°C higher in the west than in the east

• This is important because warmer water evaporates more freely, leads to wet conditions

• Where the east Pacific is relatively dry, 22°C, 8°C lower than the west

• Colder air is harder to evaporate

The Eastern Pacific (South American

areas)

Humboldt Current • http://en.wikipedia.org/wiki/Humboldt_Current

• A North-Westward current throughout South America that carries nutrients that feed the most economic fish in the world: anchovetta

ALL NORMAL CURRENTShttp://images.google.com/imgres?imgurl=

El Niño’s Effect

Occurs every three to seven years! This is the general trend, but they can occur more often

Properties of El Niño

• It is officially called an El Niño when sea surface temperatures are sustained at 0.5°C deviant of normal temperatures in the central Pacific Ocean

• If this occurs for less than five months, it is called El Niño conditions

• If this occurs more than five months, it is called an El Niño episode

El Niño’s Effect

Weakening of the east to west tropical winds

allows the warm surface water to flow back eastward

abnormal warming of surface ocean waters in the eastern tropical Pacific

That was the process, but El Niño becomes stronger from the cycle of events

• The warmer ocean winds weaker

• The weakened winds the ocean warmer

• The ocean warmerwinds weaker

Consequences of El Niño Trends

• Brings wet winters to the South Eastern United States

• Overwhelms the Humboldt current and releases humidity into the atmosphere bringing floods to South American deserts, leading to a drastic decline in primary productivity, affecting higher trophic levels of the food chain

• Cooler water collects in the far western Pacific, does not evaporate as fast as warm water, drought strikes Australia and southeast Asia

• Extreme El Niños can afflict two thirds of the world with droughts, floods, and other extreme weather

Effects in the Eastern Pacific: South America

• Normally: dry conditions

• El Niño: Warm and very wet summers FLOODS

Effects in the Western Pacific: Southeast Asia and Australia

• Normally: warm, wet conditions

• El Niño: Much drier conditions DROUGHTS

http://www.bulverdefiredepartment.com/images/brush_fire_3.jpg

Effects in North America

• Winters are warmer than normal in the Midwest, Northeast, and Canada

• Wetter and cooler conditions in California, Mexico and the southwestern U.S.

• Summer is wetter in the intermountain regions of the U.S.

• The Pacific Northwest experiences dry but foggy winters and warm, sunny and precocious springs during an El Niño.

•Cases of El Niño

http://www.pmel.noaa.gov/tao/elnino/el-nino-story.html

Normal: LeftEl Niño: Right

•Left is Western Pacific towards Indonesia•Right is Eastern Pacific near South America •Blue is cool water typically in the Eastern Pacific •Red color on the left is the warm water typically observed in the western Pacific Ocean. •El Niño-See warm water penetrating eastward on the right side•El Niño: Water temperatures significantly warmer than the norm are shown in red, and water temperatures cooler than the norm are shown in blue.

http://www.pmel.noaa.gov/tao/jsdisplay/plots/data-access/EQSST_xt.gif

The Central Pacific is where El Niño’s are detectedthe first ‘magic gate’ of 1976 originated in Maiana in the Republic of Kiribati on a 155- year-old Porites coral

Left:www.kango.org.ki/images/map.kiribati.gif Right: http://www.janeresture.com/maiana/index.htm

1976 El Niño

• There was a sustained increase in sea surface temperature of 0.6°C

• A decline in the ocean’s salinity of 0.8 percent• This really was a magic gate of change because

between 1945-1955 the sea surface temperature of the western Pacific commonly fell below 19.2°C, but in 1976, the gate ‘opened’ to a temperature of 25° C

• In 1977, National Geographic reported the crazy weather that was felt the previous year, which included unprecedented mild conditions in Alaska and blizzards in the rest of the United States

• This was because a down shift in the jet stream

Galapagos Islands• Darwin’s famous finches,

Geospiza fortis• In 1977, all finches died

except on one island because of extreme drought

• Went from population of 1,300180

• 150/180 were males, led to tough competition for mates

• Shows a bottleneck effect of evolution, all that survived had the longest beak because most efficient to capture food

http://www.gct.org/images/mainmap.jpg

http://www.blackwellpublishing.com/ridley/images/finch_magnirostris.jpg

The second ‘magic gate’:1997-1998 El Niño

• Caught worldwide attention as the event temporarily warmed air temperature by

1.5°C, compared to the usual increase of 0.25°C associated with El Niño events

1997-1998 El Niño: the worst ever recorded

Known as the year where the world caught fire

1997-1998• Drought had dominated a

large part of the planet , and so fires burned on every continent, but it was in the normally wet forests of southeast Asia that the amounts of fires reached their peak

• 10 million hectares burned, half was ancient rainforest

• Island of Borneo in South East Asia, 5 million hectares were lost

• Tim Flannery says these forests will never recover during human’s lifetime

1997-1998: The Forests of New Guinea• The world’s second largest island, just north of Australia Forests

consist of mid-montane oak forests, produce massive amounts of acorns have the largest amount of possum and giant rat,

• No rain fell in 1997! Caused fires, killed forest trees led to extinction of possum and giant rats

• 1985 2001

»

1997-1998 El Niño and Coral Reefs in Indonesia

• When the rainforests of Indonesia burned like never before, for months the air was thick with a smog cloud rich in iron

• Caused a vibrant coral reef off of Sumatra to turn to a red tide because the organisms fed on iron in the smog

• In the 1992 El Nino, the smog cloud was the size of the United States, cut sunlight by ten percent

1998 El Niño:Coral Bleaching

• Triggered the global dying of coral reefs • Because it caused sea temperatures to exceed

a threshold• In Indian Ocean: Scott and Seringapatam Reefs

percentage of coral cover went from 41%15%• Great Barrier Reef- 42% bleached• 2002, 60% of Great Barrier Reef affected• Important because as we previously learned, no

ocean’s ecosystem is more diverse than coral reefs

A scary fact

Computer-based models state that as greenhouse gas

concentrations increase in the atmosphere, a semi-permanent El Niño like condition will result

Summary

• El Niños occur every two to seven years• The normal West Pacific wet conditions

turn very dry during an El Niño and often cause droughts

• The normal Eastern Pacific dry conditions turn very wet during an El Niño and often cause floods

• The most memorable El Niños were in 1976 and in 1997-1998

Works Cited

• “What is an El, Nino anyway?” Scripp’s Institution of Oceanography: Experimental Climate Prediction Center

• Department of Commerce/ National Oceanic and Atmospheric Administration(NOAA) “El Niño Theme Page”

• Flannery, Tim. The Weather Makers: Our Changing Climate and What it Means for Life on Earth

• http://images.google.com/imgres?imgurl=http://www.sbg.ac.at/ipk/avstudio/pierofun/atmo/el-scans/el-nino1.jpg&imgrefurl=http://www.sbg.ac.at/ipk/avstudio/pierofun/atmo/elnino.htm&usg=__lvAxMRxk1KeOSKJtpaQd5fWtmaU=&h=389&w=709&sz=94&hl=en&start=1&um=1&tbnid=thPbUMxC5YJFgM:&tbnh=77&tbnw=140&prev=/images%3Fq%3DEl%2BNino%26um%3D1%26hl%3Den