CHARACTERISTICS OF OCEAN AND THE FORMATION OF WATER CURRENTS By: Ryne I. Sicam • An ocean is a body of saline water that composes much of a planets hydrosphere. Salinity is a main defining component of the ocean, and it is the amount of dissolved solid material in the water. Although there are many dissolved salts in seawater, sodium chloride (commonly known as salt) is the most abundant. This is what makes oceans unique to other aquatic ecosystems. The amount of salt water required to maintain and balance the ocean is greater than the amount of fresh water needed. • Oceans of the earth take up about 140 million square miles covering neatly 71% of the earth’s surface. The deepest point in the ocean is 36,198 feet! The five world oceans are the Pacific, Atlantic, Indian, Southern and Arctic Oceans. Ocean ecosystems have distinct characteristics and contain various life forms found only in this environment. This Photo by Unknown author is licensed under CC BY-NC. The Formation of Ocean Currents When the wind blows persistently in a particular direction, the wind stress on the sea surface causes the water in the upper layer to move bodily and a current is thereby formed. These windinduced currents may be permanent in regions of strong prevailing winds but they do not flow in the same direction as the wind. In the Northern Hemisphere they are deflected to the right of the wind direction and in the Southern Hemisphere to the left by an angle varying between 30 and 60 degrees. This deflection is an effect of the earth's rotation. • Winds • Wind is the primary force driving surface currents in the ocean. The sun heats the surface of the earth unevenly because of the shape and tilt of the earth. Warm air masses form where the sun’s radiation is most intense, which is at the equator. Cold air masses form at the poles, where the sun’s radiation is less intense. Warmer air masses rise into the atmosphere, creating areas of low pressure. As air masses cool high in the atmosphere, they sink and create areas of high pressure. The rising and sinking of air masses in the earth’s atmosphere create winds. • The Coriolis Effect • If the earth did not rotate, rising air at the equator and sinking air at higher latitudes would move straight from the poles to the equator. In reality, the air moves in a curved direction relative to the surface of the earth as it flows (creating winds in westerly and northeasterly directions) because the earth is rotating beneath the air. Imagine that you are strong enough to throw a ball from New England to Costa Rica. The ball would travel in a straight line, but the earth rotates beneath the path of the ball. Because of this, it would appear that the ball moves to the right relative to the surface of the earth, when really the earth is moving relative to the path of the ball. This is known as the Coriolis effect. Put simply, the Coriolis Effect makes things (like planes or currents of air) traveling long distances around Earth appear to move at a curve as opposed to a straight line. Gyres • The motion of the winds and deflection of water towards the right (northern hemisphere) and left (southern hemisphere) of th prevailing wind directions generates large circular current systems in the world’s oceans known as gyres. • Deflection of water towards the center of the gyre due to the Coriolis effect causes water to “pile up” in the center of the gyre creating an area of slightly higher elevation on the surface of the ocean. Gravity then pulls the water back down the slope to area of lower elevation, fueling further rotation of the gyre. • Currents along the western side of gyres are called western boundary currents, while currents along the eastern side of gy are called eastern boundary currents. The westerly flowing currents that are created where the North Pacific and South Pacific gyres meet are known as the equatorial currents . • Western boundary currents flow deeper and stronger than eastern boundary currents. This means that cool, nutrient-rich wa is closer to the surface in eastern boundary currents than western boundary currents. This results in the creation of rich upwelling zones in areas with eastern boundary currents, such as the California Current. THANK YOU FOR LISTENING!
