El Niño is back – again

April 2010

Cyclones are sweeping the Pacific more than usual, whereas the last Atlantic hurricane season was a bit on the low side. El Niño, this ocean/climate phenomenon is back, wrecking havoc in climate worldwide.

In early summer 2009, forecast models predicted a moderate El Niño event for the autumn. Sea surface height positive anomalies are measured by altimetry satellites from August 2009 with a maximum during December 2009. These conditions are weakening to normal conditions during the first half of 2010.

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Source: MyOcean Product: Global Ocean Sea Surface Heights

For centuries, Peruvian fishermen have feared the sea warming called El Niño which, every few years, around Christmas, drastically reduces their fishing catches. These El Niño events are part of a broader disruption to normal weather patterns which causes drought, flooding and hurricanes around the world. In the tropical Pacific, ocean and atmosphere circulations are closely linked, each reacting quickly to changes in the other.

Particularly strong "El Niño" events were observed in 1982-1983 and 1987-1988, which lead to the realization of a need to monitor the Equatorial Pacific and forecast this phenomenon. A smaller episode was observed in 1993-1994, before the “El Niño of the (twentieth) century” in 1997-98. From then on (2002, 2004 and 2009), the observed El Niño were mostly of a moderate strength and localized around the Central Pacific rather than along the American coasts as the typical El Niño event. For these reasons, these episodes are known as El Niño "Modoki" (meaning "similar but different" in Japanese).

Since the 1990s, an in situ observation system has been set up in the Pacific and new altimetry satellites have continuously scanned the global ocean (at the moment, Jason-2, Jason-1 and Envisat). These observation systems contribute to testing and refining our knowledge of ocean-climate interactions and numerical models of the climate. The 1997-98 El Niño was the first closely monitored event, especially by Topex/Poseidon; for the first time, global-scale seasonal forecasts were produced.

Though we cannot avoid El Niño's whims, we can predict and mitigate its impacts. Setting up an alerting system is important for all phases of natural hazard management, from outreach and education to preparing for danger. MyOcean is an important initiative in this respect, organizing all the worldwide ocean monitoring and forecasting system at the European level.

MyOcean is a European project dedicated to operational oceanography. MyOcean Service provides the best information available on the ocean, on both large and regional scales (European seas), based on the combination of satellite and in situ observations and their use in models: temperature, salinity, currents, ice extent, sea level, primary ecosystems, ...