Geoscience Reference
In-Depth Information
agricultural lands in Peru. By December, an area of warm water greater than
the size of the United States covered the eastern Pacii c, heating the overlying
air from the eastern Pacii c to Central America and even into the Atlantic
from Cuba to Libya, imposing its own weather patterns. h e Northern
Hemisphere jet stream shit ed in February 1998, bringing warm tropical
air northward and warmer than average temperatures into North America,
Europe, and eastern Asia.
Half a world away, rice paddies in the Philippines were dry and dying,
with more than $20 billion in lost crops, food shortages, and several hundred
deaths. Drought led to catastrophic wildi res in Indonesia because the nor-
mal monsoon rains never came, and the i res i lled the air with thick clouds
of smoke, causing rampant respiratory illnesses. h ese disasters occurred
despite an early warning system and programs that gave advance notice of
droughts, l oods, and potential crop failures to af ected regions of the world.
h e 1982-83 and 1997-98 El Niño events combined caused $120 billion in
damages and 24,000 deaths worldwide.
the pacific decadal oscillation (pdo)
Scientists have been monitoring the ocean and atmosphere over several
decades and have detected long-term climate patterns originating in the
North Pacii c Ocean. One of these patterns was discovered when i sheries
scientists Robert Francis and Steven Hare began analyzing cycles in salmon
populations of the coast of Alaska in the early 1990s. When they compared
the salmon population sizes with climatic and oceanographic data over a
period of several decades, they realized that the two cycles appeared to be
tracking each other.
Climatologist Nate Mantua and colleagues at the University of
Washington further analyzed the data and correlated l uctuations in
salmon productivity in the area between Alaska and the Pacii c Northwest
with changing ocean conditions during the twentieth century. h e team
observed that changes in wind direction during wintertime inl uence the
temperature of surface waters along the Pacii c Coast of North America.
When the direction of the winds causes increased upwelling of cool, nutri-
ent-rich waters, the enhanced growth of phytoplankton and krill allows
salmon populations to increase. During periods of decreased upwelling,
sea-surface temperatures rise and nutrient levels are lower, causing krill and
