La Nina and Its Effects on The Environment

What is La Nina? La Nina originates from Spanish with the meaning ‘small girl’ refer to a phenomenon that describes cooler than normal ocean surface temperatures in the Eastern and Central Pacific Ocean; regions close to the equator off the west coast of South America. La Nina is considered to be opposite or counterpart to El Nino. It is one part of the larger and naturally occurring ocean-atmosphere phenomenon known as the El Nino/Southern Oscillation or ENSO cycle.

ENSO is series of linked weather and ocean related phenomena, characterized by changes in atmospheric pressure and unusually warm (El Nino) and cool (La Nina) sea surface temperatures. In the past, La Nina also has been called as ‘anti-El Nino’ and ‘El Viejo’ which means the old man in Spanish. La Nina occurs when the easterly trade winds get stronger and blow more warm water west allowing cold water below the sea surface to push towards the top near the South American coast to replace the warm water. A build up of cooler than normal waters in the tropical Pacific, the area of the Pacific Ocean between the Tropic of Cancer and the Tropic of Capricorn caused La Nina. Upwelling process which is unusually strong eastward moving trade winds and ocean currents bring cold water to the surface can cause a drastic drop in sea surface temperature. Water in the equatorial regions follow the patterns of the trade winds. Surface currents are then formed from the winds that always blow from high pressure areas to low pressure areas.

The winds will move faster from high to low pressure if gradient difference in pressure is steeper. Sea surface temperatures across the eastern and central Pacific Ocean tend to be lower between 3 to 5 degrees Celsius than the normal temperatures during La Nina period. These sea surface temperature importance lies in the fact that largely dictate where tropical thunderstorm develop and be the most persistent that thrive over warm ocean waters. Warmest ocean waters are confined to the western equatorial pacific region during La Nina events and this is the preferred placement for tropical thunderstorms when the Northern Hemisphere cold season. These thunderstorms considered as a ‘bridge’ between atmosphere and the ocean. When develop, these thunderstorms induce low pressure within the western pacific region and meanwhile high pressure sets up across the eastern equatorial pacific that leads to stronger easterly trade winds. These strong trade winds help reinforce the sea surface temperature pattern by pushing the warm water west and enhance the strength of cool eastern pacific water due to upwelling.

La Nina conditions typically last from 9 to 12 months up to 2 years and recur every 3 to 7 years. La Nina sometimes follows El Nino although they occur at asymmetrical intervals of approximately 2 to 7 years. Both La Nina and El Nino tend to develop from March to June during the Northern Hemisphere spring, peak from November to February during late fall and winter then weaken when the following spring into summer which is March to June. Scientists collect data about La Nina using a number of technologies. The National Oceanic and Atmospheric Administration (NOAA) operates a network of buoys that measure sea surface temperature, air temperature, currents, winds and humidity where the buoys transmit data to researchers and meteorologists daily. Scientists using the buoy data in conjunction with visual information received from the satellite.

Affects of La Nina to the environment are increased rainfall, catastrophic floods, affects the climate patterns, affects weather cycles, drier than normal conditions and increased commercial fishing. When the La Nina phase, air pressure across the western Pacific less than average and this low pressure zones contribute increased rainfall in the Southeast parts of the world. Increased rainfall benefit the Southeast countries in Asia such as Bangladesh and India in term of agricultural purposes. Rainier than normal conditions also associated with La Nina events over Southeastern Africa and northern Brazil. Catastrophic floods in Queensland, Australia Drier than normal conditions. Catastrophic floods in some parts of the world cause by extreme La Nina events. Worst floods experienced in Queensland, Australia in 2010 because of the strong La Nina events. Over 10,000 people were displaced and forced to evacuate then it was estimated that over $2 billion worth of property were lost in this disastrous flood. Bolivia also experienced catastrophic flood that result in massive loss of lives and property.

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Instead of affects the rainfall patterns and atmospheric pressure, La Nina also affect the global atmospheric circulation. Atmospheric circulation describe as the large scale air movement together with the ocean currents that distributes thermal energy to earth surface. These changes are main sources of variability in climate patterns worldwide. During typical La Nina event, Montana’s spring known to be cooler and wetter.

La Nina associated with cooler temperature affect the Canadian weather, affects the British Columbian west coast, the Prairie Province through to Ontario. The different weather cycles affect Canadian agricultural sector because farmers need to wait the snow to melt before they can plant crops. Beside that, wildlife also had to adapt to extreme condition cause by different weather cycles. Parts of southern Canada receive all manner of high precipitation and more snow than usual received by the Southern British Columbia during La Nina. Higher than normal pressure over the eastern and central Pacific cause by La Nina leads to decreased cloud formation, subsequently reduced rainfall in particular region. Drier than normal conditions are observed along the west coast of tropical South America, lowland region of South America, the Gulf Coast of United States of America and also across equatorial East Africa from December to February.

This period can be shorter or longer depend to severity of La Nina. La Nina can be unpredictable and irregular as recently the climate is unpredictable. Some areas expected to be drier conditions but experience rainfall. Southern California can run drier than normal throughout the wet season that leading to more drought conditions when experience the moderate to strong La Nina.

During La Nina, high fishing season for the fishermen in Peru when changes in temperatures increased the presence of fish along the coast line that contribute to increased commercial fishing. The waters are a little warmer and the winds come along with fish food attracts more fish to the surface. It is easier for the fishermen to catch plenty of fish and in different types. Same situation also for fishing industry of western South America when upwelling brings cold and waters rich with nutrient like plankton to the surface. This will attract the fish and crustaceans also high level predators such as sea bass and prey on the crustaceans. La Nina refers to the climate pattern that describes the cooling of surface ocean waters along the tropical west coast of south America. Persistent colder than normal sea surface temperature anomalies across the central and eastern equatorial Pacific. La Nina also is part of the El Nino Southern Oscillation (ENSO).

We can conclude that the effects of La Nina experienced globally like catastrophic floods, hurricanes and cyclones in countries on the western part of the Pacific. Bushfires and drought along the west coast of the USA and East Africa. Agricultural sector also affected in term of shortage in production when farms affected and crops cannot be produced as expected.