El Niño

Since the beginning of this year experts have been warning of increasing El Niño conditions and we have also mentioned this a few times on our blog. Here’s a little summary for those who are not quite familiar with this term.

El Niño (spanish “Christ Child”, because the phenomenon occurs around Christmas in South America) happens, when the atmosphere and the surface of the sea in the equatorial Pacific are heated up more than usual.

Under normal conditions the water temperatures in the Pacific are 28 °C off Indonesia and only 24 °C off Peru. In strong El Niño years these temperatures are more than 2 degrees higher.

Due to the trade winds, cool water rises from the deep sea near the coast of Peru and causes the Humboldt current, which transports cool, eutrophic water up the South American coast northwards. In strong El Niño condition this current weakens and can even stop completely.

Usually warm surface water flows westward in the Pacific. During El Niño this current can be reversed because of changes in the wind patterns. The Eastern Pacific gets heated up while the waters off the Australian coast get cooler.

Experts presume that El Niño is a natural, cyclic climate phenomenon. However it seems likely that it is reinforced by global warming.

El Niño conditions influence the climate on a global level: Tropical cyclones are more numerous and even more destructive (the higher water temperatures supply them with more energy…). Strong rainfall on the South and North American westcoasts leads to floods and landslides, while the Amazonian forest lacks rain. Southeast Asia and Australia experience droughts, which then cause giant forest fires. While East African countries experience more rainfall, Southern Africa is drier than usual.

The interruption of the Humboldt Current is fatal for the fauna off the coast of South America and Galapagos. When the plancton dies off the food chain in the ocean collapses and masses of fish, seabirds and seals die from starvation. Due to the abnormally high sea temperatures coral in shallow areas suffers and eventually dies off from coral bleaching.

For us here in the tropical South Pacific, El Niño means that prevailing weather patterns move closer to the equator. This is also true for the South Pacific Convergence Zone, which is usually aligned in southeasterly direction and then reaches as far as Fr. Polynesia. In the convergence zone clouds, squalls and troughs are generated and during southern summer also cyclones can be developped. The risk for Fr. Polynesia (which is usually considered safe) to get in the path of such a storm rises considerably. The Societies, western Tuamotus and Austral Islands have been devasted by cyclones during former strong El Niño episodes.
Near the convergence zone the usual tradewind pattern is interrupted. Wir are planning on using those phases with northerly or even westerly winds to sail eastwards before the onset of the cyclone season in November.

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