El Nino is a climate trend in which the eastern equatorial Pacific Ocean has unusually warm surface waters. El Nino influences ocean temperatures, strength and speed of ocean tides, the well-being of coastal fisheries, and regional weather from South America and Australia, and beyond. The occurrence of El Nino plays an essential role in different ways in the coastal regions, while it also leads to negative impacts in different fields. The main objectives of this paper are to examine the atmospheric and oceanic circulation caused by El Nino.
During an El Nino event, surface waters in the eastern and central Pacific oceans become warmer than usual. This movement is influenced by the winds and the atmosphere that cuts across the Pacific Ocean. Eastern trade winds blowing from the Americas to Asia start to weaken and diverge to the west; as a result, warm waters from the western Pacific end up reaching the Americas. It slows or reverses ocean currents along the west coasts of Central and South America and at the equator by reducing the upwelling of colder, nutrient-rich waters from the deep (Carlowicz & Uz, 2017). Westerly breezes from the Pacific are more likely to come in warmer, moister air bursts, whereas easterly breezes are usually dry and persistent. The Pacific basin, which covers a third of the global humidity and wind changes, is transported throughout the globe, affecting circulation patterns like jet streams, also known as powerful upper-level winds.
Every two to seven years, an El Nino event occurs, resulting in warm air patterns that alternate with its eastern Pacific counterpart, La Nina, which has a cooling cycle and neutral effects on the surrounding areas. El Nino mostly peaks between January and November, with the effects taking months to spread throughout the world. The southeast trades are relatively steady south of around 10 degrees latitude, with its northern border moving northward to southerly throughout the northern summer, winter, and fall.
On the other hand, the winds shift considerably north of 10°s, changing direction with the storms. The depth of the thermocline is one indicator of the ocean’s dynamic response to wind forcing (Schott, Shang-Ping, & McCreary Jr, 2009). The thermohaline circulation is particularly fascinating because it responds to changes in surface freshwater forcing in a highly nonlinear manner, allowing for substantial variations in heat transmission (Rahmstorf, 2002). Tepid-water pulses are pushed easterly towards the sphere by plan jets known as Wyrtki Jets after its found twice a year; they strengthen the thermocline at the eastern boundary in the late part of the semi-annual inter-monsoon blasts, decreasing or eliminating upraising there. While salinity, temperature, and other qualities vary in three dimensions: surface to depth, east to west, and north to south, the ocean is not a comparable ecosystem whereby ocean has fronts and circulation types that transport heat and nutrients around ocean basins, as well as its weather system. Profound alterations frequently occur before changes near the surface.
According to research, El Nino affects ocean circulation in various ways. At the same time, it is also approved to impact the climatic change where many countries in the Pacific Ocean are affected by El Nino’s teleconnection pattern. When compared to the central Pacific El Nino (CP-El), abnormal rainfall is significantly boosted during the year. The central and eastern equatorial Pacific experienced increased rainfall, while the western equatorial Pacific experienced decreased rainfall on eastern Pacific El Nino (EP-El) (Sang-Wook et al., 2009). According to a new study, extreme El Nino episodes are becoming more frequent due to climate change, causing droughts to deteriorate, flooding to worsen, and storm patterns to shift (Yale Environment, 2019). The study, which Chinese and American experts conducted, looked at statistics from 33 El Nino events dating away to 1901. According to the study, El Nino, natural cyclical warming patterns in the Pacific Ocean affect worldwide weather patterns. This has been the case in the west of the Pacific Ocean, where conditions have been warmer since the 1970s (Yale Environment, 2019). Powerful El Nino may lead to specific droughts in dry weather like the case of India and Australia, significant floods in wetter climates like Peru and the Pacific Northwest, and an increase in the number of hurricanes in the Pacific while decreasing the number in the Atlantic (Yale Environment, 2019). Since the change in 1982, 1997, and 2015 three “super” El Nino have occurred, each breaking new average temperature records and triggering devastating natural calamities. According to the United Nations, thousands of people died due to harsh drought, flooding, heat, and coastal storms in the 1997-1998 El Nino, causing $96 billion in property damage.
Even though FAO does not have the mandate to study the geophysical components of the El Nino phenomena, the Organization’s concerns are focused on food security and the effects of extreme positive or negative climatic events that El Nino on agriculture can generate. (Rojas, Li, & Cuman, 2014). Major meteorological institutes keep a careful eye on El Nino situations, and forecasts are adjusted accordingly. Climate scientists issue an early warning each year, allowing governments throughout the region to consider and implement El Nino-related contingency preparations. Drought is the most severe threat to crops; El Nino, on the other hand, could have additional climatic consequences, such as flash floods or powerful hurricanes, which could disrupt agricultural activity and cause crop damage. The Agriculture Stress Index (ASI) can’t measure the adverse effects of flash floods or hurricanes; it can only estimate the positive effects, if any, due to increased water availability following heavy rainfall.
Climate change research has progressed to the point that paleoclimatic data may now provide increasingly trustworthy information on the driving forces and responses of the climate system. Understanding the mechanisms beyond these climate changes has progressed from conjecture to precise, testable theories backed up by valued simulations. The climate approach has proven to be sensitive to forcing, responding with massive and frequently abrupt changes in the surface situation. The ocean circulation plays the role of a highly irregular amplifier of climate change. El Nino might increase further if global temperatures continue to rise, wreaking havoc on populations all across the globe. Therefore, civic leaders and resource managers need to improve El Nino predictions, which will help in community preparedness for likely impacts which would minimize disruptions.
References
Carlowicz, M., & Uz, S. S. (2017). El Nino: Pacific wind and current changes bring warm, wild weather.
Rahmstorf, S. (2002). Ocean circulation and climate during the past 120,000 years.
Rojas, O., Li, Y., & Cuman, R. (2014). Understanding the drought impact of El Niño on the global agricultural areas.
Sang-Wook, Y., Kug, J. S., Dewitte, B., Kwon, M., Kirtman, B. P., & Fei-Fei, J. (2009). El Nino in a changing climate.
Schott, F. A., Shang-Ping, X., & McCreary Jr, J. P. (2009). Indian Ocean Circulation and Climate Variability.
Yale Environment. (2019). Climate change is making el Niños more intense, study finds.