The National Oceanic and Atmospheric Administration (NOAA), a prestigious American scientific agency, has recently made public that La Niña has re-developed in a pattern referred to as Double-Dip. This occurrence, together with other environmental indicators, gives us comprehensive insights on the upcoming weather patterns. This article provides an in-depth look at the El Nino Southern Oscillation (ENSO) cycle, which encompasses La Niña, and outlines how these phenomena affect global climate patterns.
An Overview of La Niña and ENSO
La Niña is a part of the larger system known as the ENSO cycle. Comprised of both warm and cool phases, the ENSO cycle dictates oceanic and atmospheric conditions in the tropical Pacific Ocean. A sequential occurrence of La Niña, after a transition through ENSO neutral conditions, can happen quite frequently and is termed a “Double-Dip.”
La Niña was observed to evolve in August 2020 and dissipate by April 2021 as ENSO-neutral conditions returned. Interestingly, for the forthcoming winter season, from December 2021 through February 2022, La Niña stands an 87% chance of regenerating. Previous occurrences of La Niña were noted in the winters of 2020-2021 and 2017-2018, with an intervening El Nino developing during 2018-2019. In the absence of either climate pattern, ENSO remains neutral, exerting no influence on global climate patterns.
The ENSO Cycle Explained
ENSO is a recurring fluctuation, predominantly affecting the sea surface temperature (El Niño phase) and the overlying atmospheric pressure (Southern Oscillation phase) across the equatorial Pacific Ocean. It includes the climatic patterns of El Niño and La Niña, which emanate from changes in ocean temperatures in the Equatorial Pacific Region. These episodes typically span nine to 12 months, with certain prolonged events lasting for years.
El Niño versus La Niña: A Comparison
El Niño, Spanish for ‘Little Boy’, is signified by warmer than average ocean water extending from near Ecuador and Peru to the central tropical Pacific. This warming occurs when trade winds weaken or reverse, transporting warm water from the western Pacific eastwards. Consequently, sea temperatures in the far western Pacific can fall below average, impacting the Walker Circulation and affecting global weather patterns.
On the other hand, La Niña, meaning ‘Little Girl’ in Spanish, is characterized by cooler than average ocean water stretching from off the coast of South America to the central tropical Pacific. This cooling results from stronger than normal easterly trade winds stirring up colder, deep sea water to the ocean’s surface and warming the far western Pacific. This, in turn, alters global weather patterns through changes in Walker Circulation and the Pacific Jet Stream.
Impacts on Marine Life and Global Weather
Both El Niño and La Niña have profound effects on marine life and global weather patterns. During El Niño, upwelling (the vertical movement of cold, nutrient-rich water from the deep ocean to the surface) weakens or halts, resulting in diminished phytoplankton populations, which disrupts the marine food chain. In the Indian Ocean, El Niño is associated with reduced monsoon rainfall.
Contrastingly, during a La Niña event, upwelling intensifies along the west coast of the Americas, driving cold, nutrient-rich water to the surface and supporting marine life. The climatic pattern also causes increased temperatures in the Western Pacific and the Indian Ocean and off the Somali coast, often causing heavy flooding in Australia and more robust monsoon rains in India.
Understanding the ENSO cycle, which includes phenomena like El Niño and La Niña, equips us better to predict and adapt to global climate changes. Given their significance, continuous scientific observation and exploration of these patterns remain a priority.