European Journal of Biomedical and Pharmaceutical Sciences

TROPICAL PACIFIC RELATIONSHIP BETWEEN NATURALLY OCCURING; EL NINO AND LA NINA ON THE OCEAN SURFACE AND THE ATMOSPHERE

Dr. Dhrubo Jyoti Sen* and Anuru Sen

ABSTRACT

During normal conditions in the Pacific Ocean, trade winds blow west along the equator, taking warm water from South America towards Asia. To replace that warm water, cold water rises from the depths — a process called upwelling. El Nino and La Nina are two opposing climate patterns that break these normal conditions. Scientists call these phenomena the El Nino-Southern Oscillation (ENSO) cycle. El Nino and La Nina can both have global impacts on weather, wildfires, ecosystems, and economies. Episodes of El Nino and La Nina typically last nine to 12 months, but can sometimes last for years. El Nino and La Nina events occur every two to seven years, on average, but they don’t occur on a regular schedule. Generally, El Nino occurs more frequently than La Nina. El Nino means Little Boy in Spanish. South American fishermen first noticed periods of unusually warm water in the Pacific Ocean in the 1600s. The full name they used was El Nino de Navidad, because El Nino typically peaks around December. El Nino can affect our weather significantly. The warmer waters cause the Pacific jet stream to move south of its neutral position. With this shift, areas in the northern U.S. and Canada are dryer and warmer than usual. But in the U.S. Gulf Coast and Southeast, these periods are wetter than usual and have increased flooding. El Nino also has a strong effect on marine life off the Pacific coast. During normal conditions, upwelling brings water from the depths to the surface; this water is cold and nutrient rich. During El Nino, upwelling weakens or stops altogether. Without the nutrients from the deep, there are fewer phytoplankton off the coast. This affects fish that eat phytoplankton and, in turn, affects everything that eats fish. The warmer waters can also bring tropical species, like yellowtail and albacore tuna, into areas that are normally too cold. La Nina means Little Girl in Spanish. La Nina is also sometimes called El Viejo, anti-El Nino, or simply "a cold event." La Nina has the opposite effect of El Nino. During La Nina events, trade winds are even stronger than usual, pushing more warm water toward Asia. Off the west coast of the Americas, upwelling increases, bringing cold, nutrient-rich water to the surface. These cold waters in the Pacific push the jet stream northward. This tends to lead to drought in the southern U.S. and heavy rains and flooding in the Pacific Northwest and Canada. During a La Nina year, winter temperatures are warmer than normal in the South and cooler than normal in the North. La Nina can also lead to a more severe hurricane season. During La Nina, waters off the Pacific coast are colder and contain more nutrients than usual. This environment supports more marine life and attracts more cold-water species, like squid and salmon, to places like the California coast.

Keywords: El Nino, La Nina, ENSO.