Ocean currents re-distribute heat, circulate water and regulate the temperature of Earth. Learn more about the effects of ocean currents on the Earth’s climate, their types, and factors that affect these ocean currents in this HelpSaveNature article.
Did you know…
… that one of the causes for the Titanic to sink is ocean currents. The Labrador current, a cold current which passes through the west coast of Greenland, frequently carries icebergs that block the ship transport routes in the North Atlantic Ocean. It was one such iceberg that caused the Titanic disaster.
Ocean currents play a major role in the distribution of heat, nutrients, water and salt around the globe. The moisture content of a region gets affected by a change in the ocean currents. They help in the formation of clouds and rain. Trade winds are formed when air which is heated over the oceans, gets lighter and is replaced by the dense cold air. In the same way, the gap created by the cold air is replaced by the warm air and an equal distribution of warm and cold air takes place. These winds and ocean currents together drive, change and affect the climate and weather across the planet.
A current is movement of water in an ocean. Based on their origin, ocean currents are classified as follows:
Surface Currents : These are currents that occur around the top 400 meters of the ocean and constitute about 10% of the water of the oceans. They mainly arise due to flowing of winds on the ocean surface and are affected by tides, gravity and other atmospheric conditions.
Deep Water Currents : These water currents are a result of the motion of water that occurs below 400 meters from the ocean water level and constitute 90% of the ocean. They arise, and are impacted by change in temperatures as well as density of water.
These currents are affected by various factors that include salinity differences, temperature and heat variations, rotation of the Earth, etc. The gravitational pull of the moon and sun causes tidal currents that also influence the ocean currents. Ocean currents govern and affect the climate of the Earth in ways discussed below.
Effects of Surface Water Currents on the Climate
Surface currents are driven by trade winds which create huge circular currents called ‘gyres’, in the oceans. The rotation of the earth causes a deflection of these gyres as well as winds to the right in the Northern Hemisphere and towards left in the Southern Hemisphere. This is called the Coriolis effect which causes the currents to move in a circular motion.
Surface currents are affected by the temperature of the water. There is an unusual heating of the water of the Pacific ocean every 2 to 12 years that causes a disturbance in the weather pattern of the region. This variations in ocean water temperature causes extreme weather conditions that are discussed below.
El Nino and La Nina
The El Nino and La Nina phenomena are collectively called El Niño Southern Oscillation (ENSO).
➥ An El Nino event is caused as a result of queer heating of the Pacific ocean water that affects the climate of the globe. It causes heavy rains, storms and floods along the American coast and its counter-effect which is severe drought is experienced along the Australian coast.
➥ A La Nina event is the opposite of an El Nino event. The warming of water occurs in the western Pacific region near Northern Australia. This causes cold temperatures as well as drought like conditions in east Pacific i.e. the mid-western U.S. and wet conditions in Australia. There is a possibility of increase in the number of tropical cyclones during a La Nina event. On the other side of the globe, a La Nina event proves beneficial for the south-west monsoon in India.
➥ ENSO events may also alter atmospheric pressures, winds, formation of clouds, temperature and humidity across various regions of the planet.
Effects of Deep Water Currents on the Climate
The deep water currents or thermohaline circulation of water is also called the Global Conveyor Belt. It takes almost 1000 years for it to complete one cycle around the planet.
Upwelling and Downwelling
These events occur as a result of the temperature and salinity difference which drive the global conveyor belt. Water, as compared to air and land, takes longer to heat up as well as cool down. The water that warms up gets lighter, and is replaced by the denser cold water. This is called upwelling. The void created by the cold water is filled again by warm water through downwelling. This upwelling and downwelling of water causes the distribution of nutrients in the ocean.
➥ The global conveyor belt is important for the circulation of carbon dioxide and other nutrients required for the growth of algae that form the basis of the food chain.
➥ The conveyor belt is very sensitive to the differences in temperature and salinity and has changed course or shut down many times in the past. This has caused dramatic changes in temperature, dust-levels, winds, glacier formations over many regions of Earth.
➥ According to meteorologists, if the global conveyor belt stops, then there will be a severe increase in the formation of glaciers and it will start an ice age on Earth.
Effects of Ocean Currents on the Temperature of the Earth
The shape of the Earth causes oceans to heat unevenly. The equator receives direct heat from the sun’s rays and warms up quickly. On the other hand, as you go towards the poles, the suns rays are slanted and the temperature gets colder. This unequal distribution and differences in temperatures would have made Earth uninhabitable. However, because of ocean currents there is an equal distribution of heat across the globe.
➥ For example, the Gulf stream warms up northwest Europe as it carries warm water from the Gulf of Mexico to the North Atlantic Ocean. If we compare the temperatures of the regions at same latitudes in Europe and North America, the difference becomes obvious. Bodo, Norway, experiences an average temperature of -2°C in January and 14°C in July whereas Nome, Alaska located at the same latitude has -15°C in January and 10°C in July.
➥ If the Gulf stream stops, Europe will experience extreme cold temperatures and may also experience a small ice age. The winter temperatures in UK will fall down further by about 5°C which will have an adverse impact on the country’s agriculture, economy and wildlife.
➥ The coastal areas experience little fluctuations in day and night temperatures as a result of ocean currents.
Effects of Ocean Currents on the Absorption and Release of Energy
➥ About 98% of the sun’s heat is absorbed by the oceans. Since the sun’s rays are perpendicular to the equator, the areas around it receive the maximum amount of the sun’s radiation. Whereas at the poles, the slanting sun’s rays causes the uneven heating of the water.
➥ The water that warms up evaporates, and is released back into the atmosphere. The tropics, thus release tremendous amount of heat and water vapor back into the atmosphere. This released heat acts as a driving force behind the atmospheric circulation of air as well as water, and formation of winds, rains and storms.
Effects of Global Warming on Ocean Currents and the Climate
➥ Global warming melts the ice at the poles which dumps huge amounts of freshwater in the oceans affecting the salinity of the water. This cold water dilution affects the flow of warm ocean currents over certain regions. This is proven by a study of the North Atlantic that reflects the reduction of the Gulf Stream current by about 30%. Thus, climate change causes alteration of the ocean currents which in turn affects the climate. It is a vicious circle that has no end.
➥ Global Warming may stop the thermohaline circulation and have devastating consequences on the nutrient and carbon dioxide cycle of the Earth.
Winds, precipitation, temperature, storms, weather patterns, hurricanes, etc., are all regulated by ocean currents. It won’t be an exaggeration to say that Earth is habitable because of ocean currents. Hence, it is important that we curb the anthropogenic activities that can have destructive effects on the Earth’s climate before it gets too late.