OSU OC 103 - e-OC103_Lesson13 (8 pages)

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e-OC103_Lesson13



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e-OC103_Lesson13

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Pages:
8
School:
Oregon State University
Course:
Oc 103 - Exploring The Deep: Geography Of The World's Oceans

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OC103 Lesson 13 Chemical and Physical Structure of the Oceans Almost all of the ocean is very dark and cold just a few degrees above freezing I know that sounds like western Oregon in December but this is much worse Only the upper few hundred meters of the ocean ever sees any sunlight or ever warms up much above freezing Not surprisingly that upper few hundred meters is where most of the biological activity takes place This lesson covers some of the chemical and physical properties of the ocean how they vary with depth and from place to place and how that affects biological activity Color Why is the Ocean Blue or Greenish Blue o Colors other than blue and sometimes green too are absorbed by water molecules Only blue and some green are reflected back to your eye reds and yellows are absorbed by the water Light Absorption in the oceans o 2 3 of the sunlight striking the ocean surface is absorbed by the first several meters of seawater That absorbed light energy converts to heat which significantly warms the upper several meters of the surface ocean o Red and yellow light are absorbed first green and blue light penetrate farther into the ocean before they are absorbed The figure at right shows how deep the different colors of light penetrate into the ocean o 99 of light is absorbed in the top 100 m or so so at about 100 m the light is very dim and gets even dimmer down deeper These shallower depths where 99 of the light is are called the photic zone because photosynthetic plants of which there are many in the oceans can survive there This 100 m depth for the photic zone is an average that varies depending upon the amount of suspended sediments and organisms in the water In areas of unusually clear water the photic zone may extend as deep as 150 200 m and in areas of unusually cloudy water it may only extend to 20 50 m deep o Below about 100 m is the aphotic zone where photosynthesis is not possible because there is not enough light Temperature Remember from the



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