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| Southern Oscillation (ENSO) | |
|---|---|
| Name | Southern Oscillation (ENSO) |
| Period | Interannual |
| Area | Pacific Ocean, global teleconnections |
| Related | El Niño–Southern Oscillation |
Southern Oscillation (ENSO) The Southern Oscillation, commonly referred to by its coupled climate mode ENSO, is an interannual climate phenomenon linking tropical Pacific sea surface temperatures, atmospheric pressure, and global circulation. Observational networks led by National Oceanic and Atmospheric Administration and Australian Bureau of Meteorology characterize ENSO through indices such as the Southern Oscillation Index and Niño sea surface temperature anomalies, which influence weather patterns across continents including South America, Australia, Africa, and Asia. Research on ENSO informs institutions like the Met Office and projects at the National Aeronautics and Space Administration and the World Meteorological Organization for seasonal forecasting and climate risk management.
ENSO is a coupled ocean–atmosphere phenomenon that emerged as a focus of study after events documented by explorers near Easter Island and analyses by scientists at Scripps Institution of Oceanography and CSIRO; it unifies the atmospheric Southern Oscillation described by Gilbert Walker with the oceanic El Niño described in historical accounts by Peruvian fishermen and scientists at Instituto Geofísico del Perú. Key metrics include pressure differences measured at Tahiti and Darwin, Northern Territory and anomalous SSTs in regions labeled Niño 1–4 monitored by centers such as NOAA's Climate Prediction Center and the Bureau of Meteorology (Australia). ENSO operates within the broader context of decadal variability studied by researchers at Potsdam Institute for Climate Impact Research and the Scripps Institution of Oceanography.
ENSO arises from interactions among the tropical Pacific ocean, the Walker circulation first inferred by Gilbert Walker, and equatorial wave dynamics studied by scientists at Woods Hole Oceanographic Institution and Lamont–Doherty Earth Observatory. Wind anomalies in the equatorial Pacific alter thermocline depth via Kelvin and Rossby waves investigated by researchers at University of Hawaii at Mānoa and Institut Français de Recherche pour l'Exploitation de la MER. Bjerknes feedbacks, described by Jacob Bjerknes, amplify SST and pressure anomalies through coupled oceanic and atmospheric responses, while stochastic forcing from phenomena recorded by Hurricane Katrina-era studies and volcanic influences considered by Mount Pinatubo research can modulate ENSO onset. Thermodynamic and dynamical theories developed at Princeton University and Massachusetts Institute of Technology frame ENSO as a mode of tropical variability interacting with midlatitude teleconnections such as the Pacific–North American pattern investigated at NOAA.
ENSO exhibits phases commonly labeled El Niño and La Niña, with neutral intervals; El Niño events historically include the 1982–83 and 1997–98 episodes analyzed by teams at International Research Institute for Climate and Society and Intergovernmental Panel on Climate Change, while La Niña episodes include 2010–11 studied by Australian Bureau of Meteorology and NOAA. Phase classification uses Niño 3.4 SST anomalies monitored by the Climate Prediction Center and the Southern Oscillation Index measured at Tahiti and Darwin, Northern Territory. Interactions with modes such as the Pacific Decadal Oscillation analyzed by James Overland and the Indian Ocean Dipole studied by CSIRO researchers modulate amplitude, frequency, and regional impacts, as documented by collaborative programs at World Climate Research Programme.
ENSO drives teleconnections that alter precipitation and temperature across regions including California, Peru, Kenya, Indonesia, and Japan. Major floods and droughts associated with ENSO have affected events like the 1997–98 floods examined by United Nations Office for Disaster Risk Reduction and agricultural outcomes evaluated by the Food and Agriculture Organization. ENSO influences tropical cyclone activity in basins managed by agencies such as National Hurricane Center and Japan Meteorological Agency and modulates polar patterns that affect phenomena discussed in studies at British Antarctic Survey and National Snow and Ice Data Center. Impacts on ecosystems have been documented in research on coral bleaching by Great Barrier Reef Marine Park Authority and fisheries monitored by Instituto del Mar de Perú.
Operational monitoring uses arrays including the Tropical Atmosphere Ocean (TAO) array developed by NOAA and Scripps Institution of Oceanography, satellite missions by European Space Agency and NASA (e.g., TOPEX/Poseidon), and reanalysis products from ECMWF. Forecasts employ coupled models from centers such as Met Office Hadley Centre, NOAA Geophysical Fluid Dynamics Laboratory, and research consortia at International Research Institute for Climate and Society and Potsdam Institute for Climate Impact Research. Prediction challenges include the spring predictability barrier analyzed by teams at Columbia University and the role of stochastic atmospheric noise studied at Lamont–Doherty Earth Observatory.
Notable historical ENSO events include the 1877–78 and 1899 episodes reconstructed by archives at National Archives and Records Administration and paleoclimate proxies from corals and tree rings archived by Smithsonian Institution and Chinese Academy of Sciences. Paleoclimate records from corals in the central Pacific studied by Australian Institute of Marine Science and speleothems analyzed by University of Arizona demonstrate ENSO variability over centuries and millennia, informing debates featured in Intergovernmental Panel on Climate Change assessments. Socioeconomic impacts of historic events are documented in colonial records from Peru and ship logs curated by National Maritime Museum.
ENSO influences agriculture, water resources, and public health, affecting commodity markets tracked by World Bank and humanitarian responses coordinated by United Nations Office for the Coordination of Humanitarian Affairs. Crop failures in regions such as Ethiopia and Peru during strong ENSO phases have prompted interventions by United States Agency for International Development and International Red Cross and Red Crescent Movement. Insurance and reinsurance sectors like Munich Re and Swiss Re integrate ENSO-related risk in models, while adaptation planning is undertaken by national agencies including Ministry of Agriculture (Australia) and regional bodies such as Association of Southeast Asian Nations.
Category:Climate phenomena