Page 205 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

Chapter 6 atmospheric and Oceanic Circulations 169
SST* 28°C
Indonesia
Northern Territory 0m
30° N
15° N
50 m
South America
*SST = Sea-surface temperature
40 cm
Tahiti, Society Islands Upwelling
Darwin,
SST 25°C (77°F) 0° 0m
L
SST 25°C
H
Australia
(a) Normal wind and pressure patterns across the Pacific Ocean.
200 m
Indonesia
Darwin
30 cm 0m
200 m
H
SST 28°C
L
Tahiti
Upwelling blocked by warm surface waters
30° N
15° N
South America
▲Figure 6.21 Normal, El Niño, and La Niña conditions in the Pacific. [(a) and (b) adapted and corrected from C. S. ramage, “el niño.” © 1986 by Scientific American, Inc. (b image)–(c) TOPEX/Poseidon, (d) Jason–1, (e) OSTM-Jason–2 images courtesy of Jet Propulsion laboratory, naSa.]
the subsequent La Niña was not as strong as predicted and shared the Pacific with lingering warm water (Figure 6.21c).
In contrast, the 2010–2011 La Niña was one of the strongest on record, according to atmospheric indicators (and correlated with sea­surface height anomalies, Figure 6.21e). This event corresponded with the wettest
December in history in Queensland and across eastern Australia, where heavy rainfall led to the country’s worst flooding in 50 years. Weeks of precipitation caused the Fitzroy River to overflow its banks, inundating an area the size of France and Germany combined and causing the evacuationofthousandsofpeople(seeFigure6.22).This La Niña intensified again in late 2011, lasting into 2012.
0°
15 cm
El Niño November 10, 1997
0m 50 m
Australia
New thermocline
(b) El Niño wind and pressure patterns across the Pacific Ocean. Image shows sea-surface height anomalies. White indicates the warmest surface water—a warm pool.
(c) La Niña October 12, 1998
(d) El Niño January 3, 2010
Sea Surface Height Anomaly
(e) Strong La Niña December 26, 2010
􏰀180 􏰀140
􏰀100 􏰀60 􏰀20 20 60 100 140 180 millimetres
130° E
180° 150° W Trade winds
Equator Normal sea level
180° 150° W
Trade winds
Equator
Thermocline
International
International
Date Line
Date Line