Oceans Moderate ClimateOceans Moderate Climate

By: Suzanne A. McKeonBy: Suzanne A. McKeon

AKA: “Sammie”AKA: “Sammie”

Heating the oceanHeating the ocean

Earth is a complex and dynamic system with a surface that is more ocean than land. The ocean interacts continually with the atmosphere, by exchanging, storing, and transporting matter and energy. Water bodies have a much higher heat capacity than land and intercept more incoming sunlight than land surfaces because of its greater transparency.

Heat Transfer Heat Transfer

Wherever the Sun is perpendicular to Earth's Wherever the Sun is perpendicular to Earth's surface, the most heat absorption takes place. surface, the most heat absorption takes place. Equatorial and tropical regions have a net gain of Equatorial and tropical regions have a net gain of heat, whereas polar regions experience a net loss. heat, whereas polar regions experience a net loss. Both air and water currents re-distribute heat over Both air and water currents re-distribute heat over Earth. The Sun warms the surface of the ocean Earth. The Sun warms the surface of the ocean and land, which in turn warm the atmosphere from and land, which in turn warm the atmosphere from the bottom up. Wherever the atmosphere contacts the bottom up. Wherever the atmosphere contacts warm water, evaporation occurs and water vapor warm water, evaporation occurs and water vapor and energy are transferred to the air mass.and energy are transferred to the air mass.

Heat Energy Heat Energy

Ocean surface waters can store tremendous Ocean surface waters can store tremendous amounts of heat energy. This heat amounts of heat energy. This heat evaporates large quantities of water and evaporates large quantities of water and warms the overlying atmosphere. Winds warms the overlying atmosphere. Winds then distribute this heat around the globe. then distribute this heat around the globe. The direction of air movements and the The direction of air movements and the temperature of the ocean water determine temperature of the ocean water determine the direction storm fronts take as well as the direction storm fronts take as well as their intensity. their intensity.

Oceans Effects on Weather Oceans Effects on Weather About 70% of the world is covered by water. 97% of this water is in the About 70% of the world is covered by water. 97% of this water is in the oceans oceans and and seasseas. Ocean water moves a lot! Tides, waves, surface currents, and deep . Ocean water moves a lot! Tides, waves, surface currents, and deep water circulation are all types of ocean water movement. The oceans have a water circulation are all types of ocean water movement. The oceans have a major effect on the weather, and they moderate the world's climate. major effect on the weather, and they moderate the world's climate.

The Water CycleThe Water Cycle

http://ga.water.usgs.gov/edu/watercycle.html

The Water Cycle cont…The Water Cycle cont…The Earth's water is always in circulation. It has been recycled for the last 3 The Earth's water is always in circulation. It has been recycled for the last 3 billion years. This process is called the billion years. This process is called the water cyclewater cycle. .

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Water CycleWater CycleThe cycle starts when the sun's heat evaporates The cycle starts when the sun's heat evaporates water from the oceans into the atmosphere to form water from the oceans into the atmosphere to form clouds. When the conditions are just right, the clouds. When the conditions are just right, the clouds release water as rain or snow. Most of the clouds release water as rain or snow. Most of the rain falls in the oceans, but the rest falls onto land. rain falls in the oceans, but the rest falls onto land. Rivers and streams collect water from the ground Rivers and streams collect water from the ground and return it to the ocean so the whole cycle can and return it to the ocean so the whole cycle can start all over again. The water cycle never ends start all over again. The water cycle never ends because the salty ocean water constantly supplies because the salty ocean water constantly supplies fresh water to the continents. fresh water to the continents.

The Evaporation StageThe Evaporation Stage

One process which transfers water from the ground back to One process which transfers water from the ground back to the atmosphere is evaporation. Evaporation is when water the atmosphere is evaporation. Evaporation is when water passes from a liquid phase to a gas phase. Rates of passes from a liquid phase to a gas phase. Rates of evaporation of water depend on things like the evaporation of water depend on things like the temperature, humidity, and wind. temperature, humidity, and wind.

Water that is held in lakes and rivers evaporates directly Water that is held in lakes and rivers evaporates directly into the atmosphere. Some of the water in the ground may into the atmosphere. Some of the water in the ground may also be returned to the atmosphere by way of evaporation also be returned to the atmosphere by way of evaporation through the soil surface. Of course, the ocean is the through the soil surface. Of course, the ocean is the greatest source for water evaporated into the atmosphere. greatest source for water evaporated into the atmosphere.

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The Transpiration StageThe Transpiration Stage

Transpiration is the process by which plants return water to Transpiration is the process by which plants return water to the atmosphere. After absorbing water from the ground, the atmosphere. After absorbing water from the ground, plants release water through their leaves. Transpiration plants release water through their leaves. Transpiration helps plants stay cool, in the same way perspiration keeps helps plants stay cool, in the same way perspiration keeps humans and animals cool. humans and animals cool.

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The Carbon CycleThe Carbon Cycle

Carbon is an element. It is part Carbon is an element. It is part of oceans, air, rocks, soil and all of oceans, air, rocks, soil and all living things. Carbon doesn’t living things. Carbon doesn’t stay in one place. It is always on stay in one place. It is always on the move! the move! Carbon moves from the Carbon moves from the atmosphere to the oceans. atmosphere to the oceans. The oceans, and other bodies of The oceans, and other bodies of water, soak up some carbon water, soak up some carbon from the atmosphere. Animals from the atmosphere. Animals that live in the ocean use the that live in the ocean use the carbon to build their skeletons carbon to build their skeletons and shells. and shells.

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Circulation of the Oceans Surface waterCirculation of the Oceans Surface water

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Warm currents are noted in the color Warm currents are noted in the color redred and cold currents are noted in the color and cold currents are noted in the color blueblue..

Oceans CurrentsOceans Currents

Two Types of Ocean CurrentsTwo Types of Ocean Currents

1. 1. Surface CurrentsSurface Currents----Surface Surface CirculationCirculation

10% of all the water in the ocean.10% of all the water in the ocean.

these waters are the upper 400 meters of these waters are the upper 400 meters of the ocean.the ocean.

2. 2. Deep Water CurrentsDeep Water Currents----Thermohaline Thermohaline CirculationCirculation

90% of the ocean90% of the ocean

Oceans CurrentsOceans Currents North & South Equatorial Current North & South Equatorial Current Equatorial Counter Current Equatorial Counter Current North Atlantic Drift North Atlantic Drift

Surface water movement takes place in the form of currents. Currents move Surface water movement takes place in the form of currents. Currents move ocean water horizontally at the ocean's surface. Surface currents are driven ocean water horizontally at the ocean's surface. Surface currents are driven mainly by the wind. Other forces such as the Coriolis effect and the location of mainly by the wind. Other forces such as the Coriolis effect and the location of land masses do affect surface current patterns. In fact, huge circular patterns land masses do affect surface current patterns. In fact, huge circular patterns called current gyres can be seen when looking at the world's ocean currents. called current gyres can be seen when looking at the world's ocean currents.

From the equator to middle latitudes, the circular motion is clockwise in the From the equator to middle latitudes, the circular motion is clockwise in the Northern Hemisphere and counterclockwise in the Southern hemisphere. Near Northern Hemisphere and counterclockwise in the Southern hemisphere. Near the poles of the Earth, there is a tendency for the gyres to flow in the opposite the poles of the Earth, there is a tendency for the gyres to flow in the opposite direction. This circulation of water helps spread energy from the Sun. The Sun direction. This circulation of water helps spread energy from the Sun. The Sun warms water at the equator and then water and heat are transported to higher warms water at the equator and then water and heat are transported to higher latitudes. latitudes.

Ocean currents are produced by Ocean currents are produced by many different things. many different things.

Currents are made by the gravitational pull of the Currents are made by the gravitational pull of the moon and sun, the prevailing winds blowing on the moon and sun, the prevailing winds blowing on the ocean surface and the unequal heating of the ocean surface and the unequal heating of the water by the rays of the sun. water by the rays of the sun.

The ocean currents are also affected by the The ocean currents are also affected by the rotation of the earth. The general movement of the rotation of the earth. The general movement of the currents is clockwise in the Northern Hemisphere currents is clockwise in the Northern Hemisphere and counterclockwise in the Southern and counterclockwise in the Southern Hemisphere. Hemisphere.

Gravitational PullGravitational Pull

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Why do currents flow?Why do currents flow?

Currents exist at all depths in the ocean; in Currents exist at all depths in the ocean; in some regions, two or more currents flow in some regions, two or more currents flow in different directions at different depths. different directions at different depths. Although the current system is complex, Although the current system is complex, ocean currents are driven by two forces: the ocean currents are driven by two forces: the Sun and the rotation of the Earth. Sun and the rotation of the Earth.

Deep Currents Deep Currents

Currents in the deep ocean exist because of changes in Currents in the deep ocean exist because of changes in the density of sea water occurring at the surface. These the density of sea water occurring at the surface. These density changes give rise to specific water masses, which density changes give rise to specific water masses, which have well-defined temperature and salinity characteristics, have well-defined temperature and salinity characteristics,

and which can be traced for long distances in the ocean.and which can be traced for long distances in the ocean.

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Role of Water MassesRole of Water Masses

Water masses help to transfer oxygen from the Water masses help to transfer oxygen from the atmosphere into the deep ocean. The sinking water is very atmosphere into the deep ocean. The sinking water is very cold and contains high concentrations of dissolved oxygen cold and contains high concentrations of dissolved oxygen acquired at the surface, because cold water can hold more acquired at the surface, because cold water can hold more oxygen than warm water. oxygen than warm water.

During their flow, they mix with "older" water that has been During their flow, they mix with "older" water that has been away from the surface for a longer time, thus ensuring that away from the surface for a longer time, thus ensuring that

the bottom waters of the ocean are supplied with oxygen.the bottom waters of the ocean are supplied with oxygen.

Affects of the SunAffects of the Sun

The Sun affects the ocean in two ways. The Sun affects the ocean in two ways. First, it heats the atmosphere, creating First, it heats the atmosphere, creating winds and moving the sea surface through winds and moving the sea surface through friction. This tends to drag the water surface friction. This tends to drag the water surface along as the wind blows over it. Although along as the wind blows over it. Although the wind strongly affects the surface layer, the wind strongly affects the surface layer, its influence does not extend much below its influence does not extend much below about 100 meters (325 feet) in depth.about 100 meters (325 feet) in depth.

Affects of the Sun cont…Affects of the Sun cont…

The second effect of the Sun is to alter the The second effect of the Sun is to alter the density of the ocean surface water directly density of the ocean surface water directly by changing its temperature and/or its by changing its temperature and/or its salinitysalinity. If water is cooled or becomes . If water is cooled or becomes saltier through evaporation, it becomes saltier through evaporation, it becomes denser. This can result in the water column denser. This can result in the water column becoming unstable, setting up density-becoming unstable, setting up density-dependent currents, also known as the dependent currents, also known as the thermohaline circulation.thermohaline circulation.

Coriolis force Coriolis force

A parcel of water at the equator A parcel of water at the equator is moving at the same speed as is moving at the same speed as the Earth. If it starts to move the Earth. If it starts to move north, with no friction, it is then north, with no friction, it is then going faster than the Earth going faster than the Earth beneath it. To conserve beneath it. To conserve momentum (the product of mass momentum (the product of mass and velocity), it consequently and velocity), it consequently moves more to the east as it moves more to the east as it gets farther from the equator. gets farther from the equator. The Coriolis force therefore The Coriolis force therefore increases away from the increases away from the equator. equator.

Coriolis ForceCoriolis Force

This force causes water to move to the right This force causes water to move to the right in the Northern Hemisphere and to the left in in the Northern Hemisphere and to the left in the Southern Hemisphere. It exists because the Southern Hemisphere. It exists because moving ocean water is affected by friction moving ocean water is affected by friction with the Earth only at the seafloor, and with the Earth only at the seafloor, and because the eastward linear velocity of the because the eastward linear velocity of the earth decreases from a maximum at the earth decreases from a maximum at the equator to zero at the poles (the rotational equator to zero at the poles (the rotational velocity, however, does not change). velocity, however, does not change).

Ekman's Theory. Ekman's Theory.

The first reasonable theory of how the wind affects surface The first reasonable theory of how the wind affects surface currents was derived by Swedish oceanographer and currents was derived by Swedish oceanographer and mathematician Valfrid Ekman in 1890. Ekman considered mathematician Valfrid Ekman in 1890. Ekman considered an infinitely wide and deep ocean of constant density, an infinitely wide and deep ocean of constant density, divided into an infinite number of horizontal layers. divided into an infinite number of horizontal layers.

The top layer is affected by the wind and by friction with the The top layer is affected by the wind and by friction with the layer below it. The second layer is also affected by friction layer below it. The second layer is also affected by friction at top and bottom, and so on. The Coriolis force also at top and bottom, and so on. The Coriolis force also

affects the layers because they are moving.affects the layers because they are moving.