why do the ocean and the sky look blue?

The Color We SeeOur eyes are able to see the color that is

reflected or scattered off an object. We cannot usually see the colors that are absorbed by an

object. If all light reflects off an object, the object appears white. If all light is absorbed by an object, the object appears black. A red crab

appears red because it reflects red light and absorbs all other colors.

Hazy Air vs. Clear AirClear air becomes hazy when tiny particles are present in the air. The distance visible light is able to travel is dependent upon the clarity of the air. If the air is hazy there are more molecules, so there will be more scattering and the visible light will not travel very far. If the air is clear there are less molecules and there will be less opportunities for the visible light to scatter, allowing it to travel farther.

Cloudy Water vs. Clear Water

Water located in the middle of the ocean is a very clear, deep, dark blue whereas, water

located along the coast is much more cloudy and murky in appearance. In the clearest water,

10% of the visible light that passes through the surface of the ocean can travel down 90 meters. In coastal water, however, visible light does not

typically travel deeper than a few meters.

The Blue SkyWhen sunlight enters the atmosphere, it is absorbed or scattered by molecules and particles. The short wavelengths of visible light; blue, green, and violet, are scattered by air molecules more frequently than the long wavelengths; red, yellow, and orange. The sky looks blue, rather than green or violet, because human eyes are most sensitive to blue light.

The Blue OceanWhen sunlight enters the ocean, it is absorbed

or scattered by molecules and particles. The ocean looks blue because the molecules and

particles in water absorb red light first and then blue light. The ocean’s color is also dependent

upon the color of the sky. On a day when the sky is bright blue the ocean appears blue, but

on a cloudy day the ocean appears gray.

Did You Know?

Underwater all things appear blue because blue light penetrates

deepest in the ocean.

1. Ahrens, C. D. (2005). Essentials of Meteorology: An Invitation to the Atmosphere (4th ed.). California: Thomson.2. Chase, V. (2007, January 24). Learning Ocean Science through Ocean Exploration: Section 5 - Ocean Zones. NOAA. Retrieved July 2, 2007, from http://oceanexplorer.noaa.gov/edu/curriculum/section5.pdf3. Ocean Explorer. (2006, March 21). NOAA. Retrieved July 5, 2007, from http://oceanexplorer.noaa.gov/explorations/04deepscope/background/deeplight/media/diagram3.html4. Stewart, R. H. (2005). An Introduction to Physical Oceanography. Texas: Texas A & M University.

Created by Leeanne Hazzard & Fabrice Veron, 2007Air-Sea Interaction Laboratory

College of Marine and Earth StudiesUniversity of Delaware

Light in the OceanRather than reflecting, most sunlight that reaches

the ocean’s surface passes directly into the ocean. As the light travels through the ocean, it is absorbed

and scattered by molecules and particles. Water absorbs light faster when the wavelength is long

and the energy is low. Consequently, red light disappears within the ocean quickly, while blue light

is able to reach great depths.

Light in the AtmosphereAs light travels through the atmosphere, it travels along a path until it comes in contact with an object, such as an air molecule, dust, or a gas molecule. Once in contact, the light is absorbed by the object, it is reflected or scattered off the object, or it travels through the object. In particular, air molecules scatter all colors of visible light, however, blue and violet are the colors scattered most frequently.

Did you know?

Light travels slower in water than in air.

1. Ahrens, C. D. (2005). Essentials of Meteorology: An Invitation to the Atmosphere (4th ed.). California: Thomson.2. Chase, V. (2007, January 24). Learning Ocean Science through Ocean Exploration: Section 5 - Ocean Zones. NOAA. Retrieved July 2, 2007, from http://oceanexplorer.noaa.gov/edu/curriculum/section5.pdf3. Stewart, R. H. (2005). An Introduction to Physical Oceanography. Texas: Texas A & M University.

Visible LightThe visible region is organized

with red at one end of the spectrum, followed by orange, yellow, green, blue, and violet.

Red has the longest wavelength, lowest frequency, and least

amount of energy, while violet has the shortest wavelength,

highest frequency, and greatest amount of energy. As you move across the spectrum from red to violet, wavelength decreases,

while energy increases.

The Sun’s EnergyThe Sun transmits energy to the surface of Earth. The Sun’s energy travels in the form of electromagnetic waves, which are

are organized into the electromagnetic spectrum. The visible region of the

electromagnetic spectrum is the portion of the Sun’s energy that we can see. Visible

light makes up 44% of total radiation emitted from the Sun.

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http://eosweb.larc.nasa.gov/EDDOCS/Wavelengths_for_Colors.html



1. Are air temperatures the same over land and water? (2002, April 16). National Data Buoy Center NOAA. Retrieved on July 5, 2007, from http://www.ndbc.noaa.gov/educate/temps.shtml2. Stewart, R. H. (2005). An Introduction to Physical Oceanography. Texas: Texas A & M University.3. VanCleave, J. (1996). Oceans for Every Kid: Easy Activities that Make Learning Science Fun. New York: John Wiley & Sons, Inc.

Characteristics of Ocean WaterThe water in the ocean heats and cools at a very slow rate. Throughout the day, the ocean absorbs heat from the sun and during the night the ocean holds in the heat permitting only small changes in temperature.

Fast Fact:You need the Calories contained in 1 Dairy Queen hamburger

(290 Calories) to heat up 80 gallons of ocean

water by 1°C.

Effect of Ocean Water on Coastal TemperaturesLocations along the coast do not experience very drastic changes in weather. The ocean stores heat in the summer, releases it in the winter, and then starts the cycle over again. As a result of this cycle, winters along the coast tend to be warmer than winters inland and summers along the coast tend to be cooler than summers inland.

Air Temperatures over the Land and SeaThe range of air temperatures throughout the year increases as you travel farther away from the ocean. In the center of most continents, the range of air temperatures may exceed 40°C, whereas, over the ocean and along coasts the range of air temperatures is usually less than 10°C.

Ocean vs. LandBoth the ocean and the land continuously exchange heat with the atmosphere, however, the land stores and releases much less heat than the ocean.

North CarolinaMeasurements were taken from

two locations, Cape Lookout, N.C. and a deep-sea buoy off the coast of N.C. The stations were positioned at the latitude 34.6°N and separated by only

192 miles. Despite their closeness, the air temperatures

at each of these stations differed greatly during the months from November to

March. Taking a closer look at the air and water temperatures

recorded by the deep-sea buoy, it is evident that during the winter months the warm

ocean water radiates heat into the air, causing the air

temperatures above the ocean to rise.

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1. Ahrens, C. D. (2005). Essentials of Meteorology: An Invitation to the Atmosphere (4th ed.). California: Thomson.2. Herring, D., Weier, J., & Gubbels, T. (2002, August). Environmental Indicators for Coastal Management. Earth Observation Magazine, 11(8).3. Hutchinson, S. & Hawkins, L. E. (2005). Oceans: A Visual Guide. New York: Firefly Books.4. Sustain Healthy Coasts. (2005). NOAA Strategic Plan – Executive Summary. Retrieved July 20, 2007, from http://www.noaa.gov/str-plan/m-coasts.html

Coral ReefsCoral reef habitats cover 0.2% of the ocean floor. Despite their small percentage, coral reefs are a crucial part of the marine habitat because they are home to millions of fish and marine plants. During the past 50 years, humans have put a strain on coral reefs by altering their surrounding waters and disturbing their foundations. Currently, 27% of coral reefs have been lost and 32% are at risk of being lost in the near future.

http://earthobservatory.nasa.gov/

Coastal PollutionThe two major sources of coastal pollution include, land run-off and conscious dumping of hazardous material into the ocean. Marine pollution is becoming more evident in the increased amount of trash found on the beaches. Less visible to the naked eye, but equally as dangerous are the chemicals rapidly accumulating in our rivers, lakes, and oceans, which are contaminating marine food chains on a global scale.http://www.foprobim.org/

Fishing and Shellfish FarmingOceans have helped to provide communities along the coasts with food for thousands of years. Today, many commercial and sport fisheries rely on remote sensing measurements of sea surface temperatures to capture images of the boundary lines between warm and cold water masses in the ocean. Since fish and shellfish typically school along these boundaries, fishermen can more effectively harvest fish and shellfish. However, as a result of improved fishing technology, fish and shellfish are now being over harvested.

What are coasts used for?Coasts provide habitats for various marine organisms. Currently, earth’s marine habitats are showing signs of stress. Increased habitat destruction, coastal pollution, and over fishing have begun to diminish the population of coastal fish, shellfish, and other various species. Also, natural resources in coastal areas have been depleted in response to rapid population growth and increased demand.

Make an EffortA majority of the public has very little insight into the devastation currently occurring in marine habitats. With this, society must make an effort to become aware of their surroundings and begin to efficiently manage earth’s coastal and inland waters before these resources become unusable.

Fast Fact:More than 66% of

the world’s population lives

within 62 miles of the coast.



1. Ahrens, C. D. (2005). Essentials of Meteorology: An Invitation to the Atmosphere (4th ed.). California: Thomson.2. Groves, D. (1989). The Oceans: A Book of Questions and Answers. New York: John Wiley & Sons, Inc.3. Hutchinson, S. & Hawkins, L. E. (2005). Oceans: A Visual Guide. New York: Firefly Books.

The Hydrologic, or Water, CycleThe ocean, the atmosphere, and the land continuously exchange moisture among each other by means of the water cycle. Solar heating on Earth’s surface causes water to evaporate from sea surfaces and leaves of growing plants. During evaporation, liquid water turns into a gas, known as water vapor. The water vapor condenses to form clouds and then falls from the clouds as precipitation. Most of the precipitation that reaches the surface of Earth falls onto the land, but some enters directly back into the ocean. On land, precipitation fills inland water storages, replenishes rivers and streams, and drains back into the sea surfaces. Some of the water does not reach the sea surfaces immediately because it either freezes in glaciers or it evaporates directly back into the atmosphere.

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Why does most precipitation fall onto the land?A larger portion of Earth’s surface is covered by water than by land, however, more precipitation falls onto the land. Since weather patterns form and dissipate slower over the water than over the land, there is more circulation occurring in the atmosphere above the land and, therefore, more cloud formation. Once the cloud particles get too heavy to remain suspended in the air, they fall to the ground in the form of precipitation. All in all, since clouds are typically found in larger quantities over land, most precipitation will fall onto the land.

How much of the

water on Earth is

saltwater?The salty oceans

contain 97.5 percent of the liquid

water on Earth.

How much water covers Earth’s

surface?71 percent of the surface of Earth

is covered by liquid water.

Did you know?

As precipitation falls through the atmosphere, it picks up dust particles. Rainfall is nature’s way of

cleaning the air.

http://www.buffer.forestry.iastate.edu/Photogallery/illustrations/Images/Hydrologic-Cycle.jpg

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1. Ahrens, C. D. (2005). Essentials of Meteorology: An Invitation to the Atmosphere (4th ed.). California: Thomson.2. Hutchinson, S. & Hawkins, L. E. (2005). Oceans: A Visual Guide. New York: Firefly Books.3. Nowacek, D. P. (2000, Fall). Unit 2, Lesson 1: Introduction to Marine Mammals and Acoustics. Project Oceanography. Retrieved on July 12, 2007, from http://www.marine.usf.edu/pjocean/packets/4. Tarbuck, E. J. & Lutgens, F. K. (2003). Earth Science (10th ed.). New Jersey: Pearson Education.

Waves can be found in the earth, ocean, and

atmosphere

Kelvin Helmholtz WavesA sudden change in wind speed and direction is called wind shear. Wind shear produces forces that form eddies. Downwind of a mountain in a wind shear zone, turbulent eddies produce Kelvin Helmholtz Waves. Billow clouds form when Kelvin Helmboltz Waves become visible in the air.

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Mountain WavesAs wind blows over mountains, eddies and mountain waves can form beyond the mountain. Eddies, which are whirls of air, and mountain waves are usually produced when the air is stable and the wind is blowing faster than 40 knots.

Sound WavesEnergy is transferred in the form of waves within air and water. Sounds begin as a vibration and then turn into a series of waves in order to travel. Sound travels in sinusoidal or compressional waves. Sinusoidal waves look like a jump rope moving up and down, whereas compressional waves look like a slinky moving down steps.

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Seismic WavesSeismic waves are waves of energy released every time there is an earthquake. Seismic waves penetrate the Earth’s interior and can be used to study its internal structure. The waves change speed, bend, and reflect as they travel through the layers of Earth. Seismic waves can also be used to look at the seabed, in order to locate oil and gas deposits below Earth’s surface.

http://www.physics.uiowa.edu/adventure/spr_2006/feb_18-06.html

Surface WavesSurface waves are found at the surface of the ocean. These waves form when winds blow over the ocean’s surface.

Internal WavesInternal waves flow beneath the surface of the ocean due to the buoyancy force. In other words, these waves are created by differences in the density of ocean water at various depths.

Internal Waves

High Density Water

Lower Density Water

Surface Waves

Did you know?

Mammals endure hearing damage

when seismic waves are sent into the

ocean.

Sinusoidal Wave

Compressional Wave

why do the ocean and the sky look blue?

Documents

blue light

red light

ocean exploration

ocean zones

air molecules

ocean explorer

distance visible light

bright blue