La Nina and Its Effects on The Environment

What is La Nina?

Originating from the Spanish term meaning 'small girl,' La Nina denotes a meteorological phenomenon characterized by cooler-than-normal ocean surface temperatures in the Eastern and Central Pacific Ocean, particularly in regions adjacent to the equator along the west coast of South America. It stands as the antithesis to El Nino and constitutes a pivotal component of the broader El Nino/Southern Oscillation (ENSO) cycle, a natural oscillation involving interconnected weather and oceanic processes.

The ENSO cycle manifests through fluctuations in atmospheric pressure and the emergence of anomalously warm (El Nino) and cool (La Nina) sea surface temperatures. Historical references to La Nina include terms like 'anti-El Nino' and 'El Viejo,' meaning 'the old man' in Spanish, reflecting its contrasting nature to El Nino.

La Nina materializes when the easterly trade winds intensify, propelling greater volumes of warm water westward and allowing colder water from deeper ocean layers to ascend near the South American coast. This buildup of cooler waters in the tropical Pacific, spanning the area between the Tropic of Cancer and the Tropic of Capricorn, defines La Nina conditions.

The phenomenon is perpetuated by an upwelling process, facilitated by robust eastward-moving trade winds and oceanic currents, which transport cold water to the ocean surface, inducing a significant decrease in sea surface temperature. These oceanic currents are steered by prevailing winds moving from high-pressure regions to low-pressure zones, with faster wind speeds resulting from steeper pressure gradients.

During La Nina events, sea surface temperatures across the eastern and central Pacific Ocean typically register 3 to 5 degrees Celsius below normal levels. These temperature anomalies play a pivotal role in dictating the spatial distribution and persistence of tropical thunderstorms, which thrive over warm oceanic waters.

Notably, the warmest oceanic waters are concentrated in the western equatorial Pacific region during La Nina, serving as a focal point for the development of tropical thunderstorms, particularly during the Northern Hemisphere cold season. These thunderstorms act as conduits between the atmosphere and the ocean, inducing low-pressure systems in the western Pacific and fostering high-pressure conditions across the eastern equatorial Pacific. Consequently, the intensified easterly trade winds further reinforce the characteristic sea surface temperature patterns by driving warm water westward and enhancing the cooling effect in the eastern Pacific through upwelling processes.

La Nina conditions typically persist for 9 to 12 months, with some episodes extending up to 2 years, recurring every 3 to 7 years. It often follows El Nino events, albeit at irregular intervals spanning approximately 2 to 7 years. The development of both La Nina and El Nino typically occurs between March and June, peaking from November to February, before weakening in the subsequent spring and summer months.

To monitor La Nina phenomena, scientists employ various technologies, including a network of buoys operated by the National Oceanic and Atmospheric Administration (NOAA). These buoys collect data on sea surface temperature, air temperature, currents, winds, and humidity, transmitting vital information to researchers and meteorologists on a daily basis. Complementary data obtained from satellite imagery further enhances our understanding of La Nina dynamics.

Impacts of La Nina on the Environment

The ramifications of La Nina on the environment encompass a spectrum of effects ranging from increased precipitation and catastrophic floods to alterations in climate patterns, weather cycles, and commercial fishing activities. During the La Nina phase, below-average air pressure prevails across the western Pacific, contributing to heightened rainfall in Southeastern regions worldwide. This surplus precipitation proves beneficial for agricultural purposes in countries like Bangladesh and India, while similar wetter-than-normal conditions prevail over Southeastern Africa and northern Brazil.

However, the intensified rainfall associated with extreme La Nina events can lead to catastrophic floods, as exemplified by the devastating inundations experienced in Queensland, Australia, during the robust La Nina episode of 2010. This calamitous event displaced over 10,000 individuals and incurred losses exceeding $2 billion in property damage. Bolivia similarly faced severe flooding, resulting in substantial loss of life and property.

Beyond its impact on precipitation patterns and atmospheric pressure, La Nina exerts influence on global atmospheric circulation, shaping large-scale air movements and ocean currents that distribute thermal energy across the Earth's surface. Consequently, during typical La Nina events, regions like Montana experience cooler and wetter spring seasons, affecting agricultural practices such as the planting of red spring wheat.

The cooling effects associated with La Nina extend to Canadian weather patterns, affecting regions from the British Columbian west coast to the Prairie Provinces and Ontario. These shifts in weather cycles pose challenges for the agricultural sector, necessitating adjustments in planting schedules to align with favorable weather conditions. Additionally, wildlife populations must adapt to the extremes brought about by these fluctuations.

While some regions experience increased precipitation, others encounter drier-than-normal conditions during La Nina events. Areas along the west coast of tropical South America, lowland regions of South America, the Gulf Coast of the United States, and equatorial East Africa typically observe reduced rainfall from December to February. However, the duration and severity of these conditions can vary, contributing to unpredictability in climate patterns.

In Southern California, for instance, the wet season may yield drier-than-normal conditions, exacerbating drought concerns during moderate to strong La Nina episodes. Conversely, La Nina's influence on ocean temperatures enhances commercial fishing opportunities, particularly along the coasts of Peru and western South America. Warmer waters and nutrient-rich upwellings attract an abundance of fish, facilitating higher catch rates for fishermen.

Conclusion

La Nina represents a climatic phenomenon characterized by cooling surface ocean waters along the tropical west coast of South America, manifesting in persistently colder-than-normal sea surface temperatures across the central and eastern equatorial Pacific. Its global impacts encompass a myriad of environmental effects, from floods and hurricanes in Pacific-facing countries to droughts and bushfires along the western coasts of the United States and East Africa. Furthermore, the agricultural sector contends with production shortages when crops are adversely affected by these climatic anomalies.