Geography and Oceanography - Chapter 15 potx

Objectives
Objectives

learn how El Niño and La
learn how El Niño and La
Niña work
Niña work

emphasize that the ocean
emphasize that the ocean
& atmosphere are
& atmosphere are
strongly
strongly
coupled
coupled

understand that
understand that
one
one


component of the Earth’s
component of the Earth’s
system can have drastic
system can have drastic
effects on the
effects on the
rest of

rest of
the
the
Earth
Earth
El Niño: The Enigma
El Niño: The Enigma

Unusual oceanic and atmospheric
Unusual oceanic and atmospheric
phenomenon - an anomaly
phenomenon - an anomaly
–
We don’t know everything about it
We don’t know everything about it
–
We can’t really predict it yet
We can’t really predict it yet
El Niño: The Term
El Niño: The Term

First discovered in 1795
First discovered in 1795

Recognized by local fisherman along
Recognized by local fisherman along
Ecuador and Peru
Ecuador and Peru
–
Warm, surface countercurrent

Warm, surface countercurrent
–
North >South
North >South
–
Discovered around Christmas-time
Discovered around Christmas-time
–
“
“
The Christ Child”
The Christ Child”
El Niño Characteristics
El Niño Characteristics

Normally develops in W. tropical
Normally develops in W. tropical
Pacific
Pacific

Often results in natural disasters
Often results in natural disasters

Occurs every 2 to 10 years
Occurs every 2 to 10 years

Most recent and severe events in
Most recent and severe events in
1953, ‘57-’58, ‘65, ‘72-’73, ‘76-’77,
1953, ‘57-’58, ‘65, ‘72-’73, ‘76-’77,

‘82-’83
‘82-’83
, ‘91-’92,
, ‘91-’92,
‘97-’98
‘97-’98
, ‘02-’04,
, ‘02-’04,
‘06-’07, ’09’10
‘06-’07, ’09’10
Slides from 1982-’83 El Niño
Slides from 1982-’83 El Niño
-09-’10
INDEX =
•
Air temperature
•
Sea surface temp
•
Surface winds
•
Cloudiness of sky
•
Sea level pressure

Suppressed
Sea Surface
Elevated
Sea Surface

Tradewinds weaken or fail
Tradewinds weaken or fail

Tropical winds reverse and go east
Tropical winds reverse and go east
instead of west
instead of west

Atmospheric pressure cells reverse
Atmospheric pressure cells reverse
–
Wet areas become dry (drought)
Wet areas become dry (drought)
–
Dry areas get flooded
Dry areas get flooded

“
“
oscillates” like a giant
oscillates” like a giant
sea
sea
-saw,

-saw,
taking 3-5 months
taking 3-5 months
“
“
Southern Oscillation” (SO)
Southern Oscillation” (SO)
Non El Niño
El Niño
Non El Niño El Niño
Coupled Ocean-Atmosphere
Circulation
Ocean’s Response to the SO
Ocean’s Response to the SO

Warm water moves to the east
Warm water moves to the east

Elevates sea surface temperatures
Elevates sea surface temperatures
(SSTs) in SE Pacific
(SSTs) in SE Pacific

Shuts down upwelling, can induce
Shuts down upwelling, can induce
downwelling
downwelling

Reduces available nutrients
Reduces available nutrients


Kills fish and sea birds - especially
Kills fish and sea birds - especially
bad off Peru
bad off Peru
Animations
Animations
Ocean AND Atmosphere
Ocean AND Atmosphere

El Niño is both an oceanic and an
El Niño is both an oceanic and an
atmospheric phenomenon
atmospheric phenomenon
–
Often called ENSO
Often called ENSO

Scientists knew of
Scientists knew of SO
from
from
wind and
wind and
precip.
precip.
data
data

Scientists knew of

Scientists knew of
El Niño
El Niño
from
from
SST
SST


data
data

Didn’t make connection until 1969
Didn’t make connection until 1969
Jacob Bjerknes
Jacob Bjerknes

Jacob Bjerknes, a Norwegian
Jacob Bjerknes, a Norwegian
meteorologist made
meteorologist made
breakthrough in
breakthrough in


1969
1969

Combined wind, rain, AND SST data
Combined wind, rain, AND SST data


Ocean & atm. part of “big climate
Ocean & atm. part of “big climate
engine”
engine”

Effects of ENSO not just local to Peru
Effects of ENSO not just local to Peru
but could affect whole Pacific, whole
but could affect whole Pacific, whole
world
world
Interdisciplinarity Rules!
Interdisciplinarity Rules!

Bjerknes was a meterologist who
Bjerknes was a meterologist who
was willing to take a good, hard look
was willing to take a good, hard look
at oceanographic data
at oceanographic data

Oceanography a versatile science
Oceanography a versatile science
How Do We Track El Niño Today?
How Do We Track El Niño Today?

in situ
in situ
(on site) measurements

(on site) measurements

Satellite sea surface temperature
Satellite sea surface temperature

Computer models
Computer models