1. IGY and the Origins of El Niño/Southern Oscillation (ENSO) Research
Michael J. McPhaden
NOAA/Pacific Marine Environmental Laboratory
Seattle, Washington
A story of how geophysical exploration, remarkable coincidences and brilliant insights led to fundamental breakthroughs in our understanding of seasonal-to-interannual climate variability
Fall AGU Meeting
10 December 2002

2. El and La El Niño, La Niña, & ENSO
El Niño: Warming of the tropical Pacific every 3-7 years
Linked to weakened trade winds, redistribution of upper ocean heat content, and shifts in tropical rainfall patterns
Typically lasts months
La Niña: an unusual cooling of the tropical Pacific
ENSO cycle: the oscillation between warm (El Niño) and cold (La Niña) conditions in the tropical Pacific.
El and La

3. Impacts on Global Weather
El Niño and La Niña increase the probability of droughts, floods, heat waves, forest fires, and extreme weather events in large regions of the globe
• El Nino also affects Pacific Marine ecosystems and commercially valuable fishstocks
• Point out Indian drought
• Temperature and precipitation changes related to El Nino.
• Wet and dry in the tropical Pacific as the most immediate consequence of shifting rainfall patterns.
• Cool and wet in the SE, warm in the NW as a result of jet stream changes.
• Notice also the dryness of the Indian summer monsoon.
• Net result is droughts, floods, heat waves, forest fires and changes in extreme weather around the world.
After Ropelewski and Halpert, 1986, 1992
Global Impacts

4. Impacts on Global Weather Global Impacts of the 1997-98 El Niño
Fatalities:
23,000
Economic Losses:
$36 Billion
• El Nino also affects Pacific Marine ecosystems and commercially valuable fishstocks
• Point out Indian drought
• Temperature and precipitation changes related to El Nino.
• Wet and dry in the tropical Pacific as the most immediate consequence of shifting rainfall patterns.
• Cool and wet in the SE, warm in the NW as a result of jet stream changes.
• Notice also the dryness of the Indian summer monsoon.
• Net result is droughts, floods, heat waves, forest fires and changes in extreme weather around the world.
After Ropelewski and Halpert, 1986, 1992
Global Impacts

5. Jacob Bjerknes,

6. The 1957-58 IGY coincides with an El Niño!
Serendipity

7. Sea Surface Temperature Index
NINO-3.4

8. Surface Air Pressure Pattern
Southern Oscillation
Surface Air Pressure Pattern
Walker

9. Southern Oscillation Index
High SOI=Strong Trades
Low SOI=Weak Trades
Darwin
Tahiti
Tahiti minus Darwin Air Pressure
Walker could not explain the 3-4 yr periodicity of the SOI, nor could he explain the spatial pattern.
Hence the SOI met with skepticism that it was a real phenomenon, rather than a statistical artifact.
Died during the IGY. Obituary was pessimtics

10. Walker’s Legacy?
“Walker’s hope was presumably not only to unearth relations useful for forecasting but…to provide a productive starting point for a theory of world weather. It hardly seems to be working out like that.”
Lots of unanswered questions about detailed physics. How the ocean switched from normal to El Nino and back, the how the tropical teleconnection were established, the extent to which it was predictable, etc. Laid the groundwork for 40 years of research.
Quart. J. Roy. Met. Soc., 1959

11. IGY-Inspired El Nino/Southern Oscillation Advances
El Niño arises from coupled interactions between the ocean and the atmosphere
Involves the entire tropical Pacific
Causes shifts in tropical rainfall patterns that can affect mid-latitude climate through atmospheric teleconnections
Might be predictable
Lots of unanswered questions about detailed physics. How the ocean switched from normal to El Nino and back, the how the tropical teleconnection were established, the extent to which it was predictable, etc. Laid the groundwork for 40 years of research.
J. Bjerknes, 1966, 1969, 1972

12. ENSO Advances Since the IGY
New theoretical understanding (“delayed oscillator”, “recharge oscillator”, etc.)
Definition of ocean and atmospheric variability (ocean waves, air-sea interactions, atmospheric teleconnections)
ENSO forecast models (statistical & dynamical)
ENSO Observing System (satellites & in situ measurements in the tropical Pacific)

13. Decadal Variations and Trends
Stochastic atmospheric forcing?
Natural decadal variability?
Anthropogenically induced?

14. The ENSO Observing System
Developed during the TOGA program ( )
Complementary satellite & in situ observations
Key oceanic and atmospheric variables for improved description, understanding, and prediction of ENSO
Timely data delivery
Long term commitment
One lesson from the IGY was that new measurements provide the underpinnings of new discoveries in geophysics, and this need for new observations motivated development of the ENSO observing system.

15. Global Ocean Observing System
Building a Sustained Ocean Observing System for Climate
Sea Surface Temperature, Height, and Vector Wind from Space
As we enter the 21st century, we realize that to further our understanding of ENSO and its global impacts, to understand the decadal modulation of ENSO, to understand other modes of climate variability, such as the newly discovered PDO and IOD, to understand anthropogenically forced climate change, and its interactions with natural climate variability, to detect the possible onset of rapid climate change, need to develop a sustained, long term, comprehensive, and integrated global ocean and global climate observing systems.
One view of the ocean component of such a system is shown here. Some parts implemented already, some in the process of being implemented, but we are still a long way away to go.
Continued progress in climate research will require routine, global, sustained, long term, high quality satellite and in situ measurements that can provide us global record of the ocean’s role in climate over many decades.
Tide Gauge Network 45 % complete
3˚x3˚ Argo Profiling Float Array Fully funded
5˚x5˚ Surface Drifting Buoy Array 35 % complete
Moored Buoy Existing Planned
Ocean Reference Station Existing Planned
High Resolution XBT and Flux Line Existing Planned
Frequently Repeated XBT Line Existing Planned
Carbon Inventory & Deep Ocean Line Survey 1.5 lines/year, 50 % funded
Global Ocean Observing System

16. Global Ocean Observing System
Sustained for the long term
Routine and cost-effective
Timely data delivery
Accuracy sufficient for climate studies
Mix of satellite & in situ observations
Adaptable to new technological and scientific advances
Multi-disciplinary
Multi-national
Freely accessible data
Integrated data and information service
Linked to model-based analysis and prediction efforts
Global Ocean Observing System for Climate
As we enter the 21st century, we realize that to further our understanding of ENSO and its global impacts, to understand the decadal modulation of ENSO, to understand other modes of climate variability, such as the newly discovered PDO and IOD, to understand anthropogenically forced climate change, and its interactions with natural climate variability, we need to develop a global ocean observing system.
One view of such a system is shown here. Some part implemented already, some in the process of being implemented, but we are still a long way away to go.
Continued progress in climate research will require routine, global, sustained, long term, high quality satellite and in situ measurements that can provide us global record of the ocean’s role in climate over many decades.
Global Ocean Observing System

17. “In the future, we can envision the creation of a worldwide service of…monitoring buoys reporting by way of communication satellites data…to give electronic computers the right input for global dynamic long-range predictions…of the coupled circulations of the atmosphere and ocean.”
J. Bjerknes, 1969
Bjerknes quote

18. Outstanding Questions
What are the new challenges and scientific questions that might frame a 21st Century IGY?
Global climate change and variability
Would a 21st Century IGY jumpstart another 50 years of groundbreaking research?
Yes, but jump starting isn’t enough. For climate, sustained, long term measurements are essential

19. Outstanding Questions
How do we convince our citizens and decision makers of its importance?
Detecting, understanding, predicting climate change and variability are critical for developing environmentally sound strategies of sustainable development