Michael J. McPhaden

NOAA/Pacific Marine Environmental Laboratory

Seattle, Washington

Fall AGU Meeting

10 December 2002

IGY and the Origins of El Niño/Southern Oscillation (ENSO)

Research

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 12-18 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.

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

After Ropelewski and Halpert, 1986, 1992

Impacts on Global Weather

After Ropelewski and Halpert, 1986, 1992

Global Impacts of the 1997-98 El Niño

Fatalities:23,000

Economic Losses:$36 Billion

Jacob Bjerknes, 1897-1975

The 1957-58 IGY coincides with an

El Niño!

Sea Surface Temperature Index

NINO-3.4

Southern Oscillation

Walker

Surface Air Pressure Pattern

Southern Oscillation Index

High SOI=Strong Trades

Low SOI=Weak Trades

Darwin Tahiti

Tahiti minus Darwin Air Pressure

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.”

Quart. J. Roy. Met. Soc., 1959

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

J. Bjerknes, 1966, 1969, 1972

ENSO Advances Since the IGY

ENSO forecast models (statistical & dynamical)

New theoretical understanding (“delayed oscillator”, “recharge oscillator”, etc.)

ENSO Observing System (satellites & in situ measurements in the tropical Pacific)

Definition of ocean and atmospheric variability (ocean waves, air-sea interactions, atmospheric teleconnections)

Decadal Variations and Trends

Stochastic atmospheric forcing?Natural decadal variability?

Anthropogenically induced?

The ENSO Observing System Developed during the TOGA

program (1985-1994) Complementary satellite &

in situ observations Key oceanic and

atmospheric variables for improved description, understanding, and prediction of ENSO

Timely data delivery Long term commitment

Building a Sustained Ocean Observing System for ClimateBuilding a Sustained Ocean Observing System for Climate

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

Sea Surface Temperature, Height, and Vector Wind from Space

Global Ocean Observing System for Climate

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

Bjerknes quote

“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

Outstanding Questions

What are the new challenges and scientific questions that might frame a 21st Century IGY?

Global climate change and variabilityGlobal 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, Yes, but jump starting isn’t enough. For climate, sustained, long term measurements are essentialsustained, long term measurements are essential

Outstanding Questions

How do we convince our citizens and decision makers of its importance?

Detecting, understanding, predicting Detecting, understanding, predicting climate change and variability are critical for climate change and variability are critical for developing environmentally sound strategies developing environmentally sound strategies of sustainable developmentof sustainable development