They often take center stage and are indeed very important, but they are not unique. El Niño And La Nina, these climatic phenomena which, in turn, warm or cool the equatorial Pacific and disrupt many regional climates, have cousins all over the world. Where are these other climate systems located? And what concrete impacts do they have? Response elements.
The Indian dipole, closest cousin ofEl Niño and of
The phenomenon closest to the Pacific dipole El Niño/La Niña (which the Anglo-Saxons call ENSO, for “El Niño – Southern Oscillation”) is to be found in the Indian Ocean.
“The Indian Ocean dipole is defined by the difference in sea surface temperature between two zones: a western pole in the Arabian Sea (west of the Indian Ocean) and an eastern pole south of the Indonesia (eastern Indian Ocean) »explain Australian Weather Bureau, which particularly follows this phenomenon. For comparison, for the couple El Niño/La Niñathese poles are made up of the east of the equatorial Pacific (off the coast of Peru), where the water is colder, and the west (off the coast of Indonesia) where it is warmer.
As it happens with El Niño And La Ninathe temperatures measured in the waters of these two poles of the Indian Ocean can vary, leading to a chain reaction. “This can have an impact on atmospheric circulation and generate wetter or drier conditions in certain sectors of this basin”explains to West France Pierre Bonnin, climatologist at Météo France.
For example, when the water in the western Indian Ocean is warmer than normal, Australia experiences less rain than usual. Conversely, when it is colder, it knows more.
This system being geographically “closer to us” than ENSO is, it is also likely to have “repercussions on the Middle East and the Mediterranean basin”, explains Pierre Bonnin. However, given the numerous influences to which these regions are subject, it remains difficult to know the extent and real nature of the effects that this Indian dipole may have on Europe.
Note that after having been in a hot phase in recent months, the latter is currently in a neutral position, which means that the temperature differences with normal are minimal in the sector. The climatic influence of this dipole is therefore just as limited.
In the Atlantic, an oscillation that works over the long term
Like its counterparts in other large oceans, the Atlantic basin also has its large climate system. It is not organized as a dipole but is a global oscillation of water temperature in a band extending from the equator to the North Atlantic.
This system is less powerful and less marked than the equatorial climatic phenomena of other oceans. For what ? Because “the equatorial part of the Atlantic basin (between South America and Africa) is ultimately small”, recalls Pierre Bonnin. The water reservoir capable of experiencing a temperature anomaly is therefore smaller than in the Pacific, which explains why the potential impacts are less strong there. Above all, the oscillation known in this basin occurs at timescales “of the order of several decades”whileEl Niño can for example reappear every 3 to 7 years.
However, these long phase changes still have consequences. Pierre Bonnin: “When there is a positive anomaly (temperatures higher than normal), this favors the emergence of cyclones”, since warm waters constitute the “fuel” of cyclones.
The Atlantic Oscillation also “an influence on precipitation in the Sahel, or even on the Indian monsoon”continues the climatologist.
Finally, certain parts of the globe are also under the influence of oscillations measured at the level of the tropics, or at the level of the poles. Yet another sign proving that when it comes to climate, the butterfly effect does indeed exist.