ELNINO AND ITS WORLDWIDE IMPACTS

             Near the end of each calendar year, the fishermen along the coasts of Ecuador and Northern Peru used to notice a strange phenomenon in the sea:  the surface temperature of the sea rises with the waters becoming warmer. From antiquity, the local residents referred to this annual warming event as El Niño which, in Spanish, means the Boy child (Jesus) because of its appearance around the Christmas season of the year. The appearance of El Niño signifies the end of the fishing season and the arrival of the time for Peruvian fishermen to repair and maintain their boats and fishing nets. Every 2 to 7 years, a much stronger warming effect unfolds along the west coast of South America, which lasts for several months and is often accompanied by heavy rainfall in the arid coastal regions of Ecuador and Northern Peru. Over time, the term El Niño began to be used in reference to these greater warming cycles only instead of the lesser annual warming phenomena. During the 1960s, scientists began to link these strange warm waters along the west coast of South America with the abnormally warm waters throughout the central and east-central equatorial Pacific. In addition, the event was shown to be closely related to a global atmospheric pressure oscillation known as the El Nino Southern Oscillation (ENSO). Now, El Nino is thought to be the major factor affecting the world-wide weather and climate.

What Causes El Nino?

         The El Nino phenomenon is caused by the warmer waters in the eastern Pacific Ocean. This water is warmer because as trade winds lessen or reverse their direction, winds from the West push warm surface water to the east in the direction of the South America continent. Therefore, there is less cold water pulled up from below as a result of this increase in warmer waters.

 WORLDWIDE EFFECTS OF EL NINO

Effects on South America

The effects of El Niño in South America are direct and stronger than elsewhere in the world.  It creates increased rainfall across the east-central and the eastern Pacific Ocean including several parts of the South American West coast.  An El Niño is associated with warm and very wet weather conditions in April to October months along the coasts of northern Peru and Ecuador causing major flooding during its active period.

          Along the west coast of South America, El Niño reduces the upwelling of cold, nutrient-rich water in the sea that sustains a large fish population which, in turn, sustains abundant sea birds. The reduction in upwelling leads to a reduction of the fish population throughout the shores of Peru affecting the fishing industry and the entire food chain of the region. So El Nino has a devastating effect on the Peruvian economy.

           It also favours the proliferation of small and fast-growing aquatic species along the Peruvian coast as periods of low population removes predators in the area. Similar effects benefit migratory  birds that travel each Spring from predator-rich tropical areas to the distant winter-stressed nesting areas.

      Southern Brazil and Northern Argentina also experience wetter conditions than normal mainly during the Spring and early Summer. Central Chile receives a mild winter with large rainfall and the Peruvian-Bolivian Altiplano is sometimes exposed to unusual winter snowfall events. Drier and hotter weather conditions prevail in parts of the Amazon River Basin, Colombia  and Central America.

 

Effects on North America

           Winters during the El Niño onset are warmer and drier than the average in most parts of The United States, and hence, it experiences reduced snowfalls. Meanwhile, significantly wetter winters are experienced in northwest Mexico and some parts of the United States including central and southern California. Both cooler and wetter than average winters are experienced in northeast Mexico and the southeast United States.

              Some believed that the Ice storm of January 1998 which devastated parts of New England, Southern Ontario and Southern Quebec was caused or accentuated by El Niño's warming effects.  El Niño also affected the Vancouver 2010 Winter Olympics as the area experienced a warmer than average winter during the games. El Niño is also credited with suppressing the Atlantic hurricanes and made the 2009 Atlantic hurricane season the least active in 12 years.

 

 Effect on Tropical Cyclones

 

    Most tropical cyclones form on the side of the subtropical ridge closer to the Equator, then move towards the Pole crossing the ridge axis before re-curving into the main belt of the Westerlies. As the subtropical ridge position shifts due to El Niño effect, the preferred tropical cyclone track also undergoes changes. Areas west of Japan and Korea tend to experience much fewer tropical cyclone impacts during El Niño for the period September to November and the remaining El Nino free years. During El Niño years, the break in the subtropical ridge tends to lie near 130⁰ E longitude, which favours the Japanese archipelago. During El Niño years, the island of Guam's chance of receiving a tropical cyclone impact is one-third higher than the long-term average. The tropical Atlantic Ocean experiences depressed hurricane activity due to increased vertical wind shear  across the region during El Niño years. 

       On the other hand, the tropical Pacific Ocean east of the dateline has cyclonic activity above the normal during El Niño years due to seawater temperatures well above the average and decreased wind shear. Most of the recorded East Pacific category 5 hurricanes occur during El Niño years in clusters. 

 Effect on Indian Monsoon

                   Generally, El Nino and the Indian Monsoon rains are inversely related. Trade winds coming from South America normally blow westward towards Asia during the Southwest monsoon  . The warming of the Pacific Ocean results in the weakening of these winds. Therefore, moisture and heat content of the wind is decreased that results in the reduction and uneven distribution of rainfall across the Indian sub-continent. This leads to widespread drought and famine in India.

 

                  The most prominent droughts in India, 6 of them since 1871, have been thought to be El Nino triggered droughts, including the recent ones that occurred in the years 2002 and 2009. Going by historical records of 135 years from 1880 to 2014, about 90% of all evolving El Nino years have led to below normal rainfall and 65% of evolving El Nino years has brought droughts. From this fact, it is clear that most El Nino years adversely affect the climate and weather conditions in India in terms of the Monsoon rain, which in turn, has a drastic effect on crop production and the economy of the country.

 

 El Ninos in the Recent Past

  

          El Niño events of 1982-83 and 1997-98 were the most intense of the 20th century. During the 1982-83 events, sea-surface temperatures in the eastern tropical Pacific were many degrees above normal. These strong temperature variations caused severe climatic changes: Australia experienced harsh drought conditions; Typhoons devastated Tahiti and record rainfall and flooding plagued central Chile. The west coast of North America was unusually stormy during the winter season, and fish catches were dramatically reduced from Chile to Alaska.

              The El Niño event of 1997-98 is regarded as the strongest of the 20th century. This was the first El Niño event to be scientifically monitored from beginning to end. The 1997-98 event produced severe drought conditions in Indonesia, Malaysia, and the Philippines. Peru experienced very heavy rains and severe flooding. In the United States, increased winter rainfall hit California, while the Midwest experienced record-breaking warm temperatures.

             The El Niño has drastically affected the lives and livelihoods of people and places worldwide. Hence studying and monitoring El Niño with the latest technological tools will contribute our greater understanding of these bizarre phenomena of nature, and thereby, equipping us to combat its menaces in a much better and organized way.

 

                                        

                                                                                         

                                                                                                         Nikunja Bihari Sahu

                                                                                                            Education Officer

                                                                                                       Regional Science Centre

                                                                                                                  Bhopal