As a child I was often in trouble with my parents. The offenses ranged from not telling them where I had gone to getting into fights with my older brother Timothy. Going through these challenges and experimenting in my youth taught me many lessons about life. I am often amazed that the simple lessons I learned as a child apply in new circumstances today. One lesson which I never knew was going to help me later happened while in the bathtub. As I imagine is common with most children, I didn’t want to take baths. If I had to take a bath I thoroughly enjoyed them; I would make fantastic tidal waves by pushing my body back and forth in the bathtub which would have the adverse effect of creating a small lake on the tile floor of our bathroom. My parents were not too impressed with my fun, but perhaps they would not make me take another bath in the future. Through observing the movement of water and the effect that I had on it, it helped me better understand how such things as thermohaline circulation and water currents work.
Water and the World
Water covers roughly 70.9% of the world’s surface; it is essential for all known forms of life. According to The World Almanac and Book of Facts Americans use on average 123 gallons of fresh water each day; if this held true as a national average than the entirety of the world uses 852,390,000,000 (852 billion) gallons of water daily. Water provides the means to clean ourselves, prepare our food, and it nurtures wildlife which we in turn eat. However, many people are unaware or perhaps uninterested that water plays a large part in Global weather and temperature. Water affects the climate and weather in several ways: it is the source of precipitation, it absorbs carbon dioxide, while water vapors are in the air it acts as a greenhouse gas, and water creates cloud cover which provides shade and can reflect and radiate away energy. Water can also affect the climate through thermohaline circulation, also known as the ocean conveyer belt. This affects both local temperatures through the transfer of water and the global climate. Water also takes a lot of energy to change temperature and as such it absorbs much of the sun’s heat. Otherwise, it would have had to have been absorbed by land mass which heats up much easier than water. Another way that water affects us is through cycles such as the El Nino of La Nina.
The El-Nino Southern Oscillation (ENSO)
Before we can fully understand why this happens, we must first understand three things about water. Firstly, we must understand that dense objects sink in water. Secondly, cold water is heavier than warm water because the water molecule contracts. Thirdly, salt water is heavier than fresh water because the salt ions have closely bonded to the water molecules. This will help us understand how the El-Nino Southern Oscillation works.
The reason that El Nino and La Nina occurs is due to the variations of the generally constant easterly trade winds in the south pacific which in turn effect the movement and currents of the South Pacific Ocean.
During a La Nina year, the winds on earth are blowing more strongly from east to west. This moves the warmer surface waters near South America towards the western pacific area: Australia and South-east Asia. This causes increased water levels, rainfall, and water pressure in the western south pacific, but for the east pacific it causes it to be colder than usual. While the warm water is being pushed to the west it piles up and displaces the colder waters below pushing that lower, colder water westward towards South America. When the cold, deep water gets to South America it replaces the warmer water that is being moved west by a process known as upwelling. This works as a general cycle – warm water in the west and cold water in the east. After the La Nina season winds return to their normal westward blowing thus decreasing the effects of the La Nina. This will stay constant for nearly 3 to 5 years before the next big change – an El Nino year.
During an El Nino year the effects are opposite of the La Nina. For some reason the winds stop blowing westward, and as a result the water no longer piles up on the west but rather rushes back towards America and eventually settles more evenly along the south pacific with the warm water distributed along the top of the ocean while the cold water remains below. This causes rain and warmer temperatures along the coast of South America along with droughts in the south east pacific. Along with the direct affects, the El-Nino Southern Oscillation also affects temperatures and air currents worldwide. As the El Nino year subsides, the normal prevailing eastern trade winds returns and blows back the warm surface water towards the south east pacific and remains fairly constant for the next 3 to 5 years until the next La Nina.
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