El Nino - affected Southern Oscillation (ENSO phase)
Every 4 to 7 years, around Christmas (reason why El Nino received its name: little Jesus-Child), rapid changes in SO appear, caused by phenomenon which we today reffer to as El Nino (ENSO phase). In contrast to usual conditions warm waters (over 28C) extend further to the east causing ITCZ to migrate southwards. Dry winds are weakning and sometimes going backwards. Such a change has huge effect on the atmosphere and air masses over the Pacific Ocean. Now, the heaviest raifalls are occuring on the west coast of South America and dry winds cause drought in the area of so south east Asia. The temperature of water in the eastern part of the ocean increases by about 5 degrees, because the upwelling of water is reduced. Warm water lacks oxygen reducing nutrients at the same time, which in a long run affects marine life.