Earth’s Oceans

Freshwater vs. Seawater (differences) 3% of Earth’s water 2% in glaciers 1% lakes, rivers, & aquifers Mixture of substances not just pure H2O Minerals from rocks and pollutants from air get mixed in Density = 1.0g/cm3 Freezes at 0ºC 97% of Earth’s water Mixture of substances 96.5% water and 3.5% dissolved salts NaCl is most abundant salt Dissolved gases include O, N, CO2 Salinity varies from place to place Density = 1.02-1.03 g/cm3 Freezes at -2ºC

Both Fresh and Seawater Respond to solar radiation (sunlight) Remember, the sun drives the water cycle

Visible Light Visible light is both absorbed and reflected Most wavelengths are absorbed Blue light is reflected All wavelengths are absorbed by 100m depth so deep lakes and oceans are dark except for surface.

Absorption of Light Water absorbs light, which gives rise to another physical property of oceans—they are dark. In general, light penetrates only the upper 100 m of seawater. Light sufficient for photosynthesis exists only in the top 100 m of the ocean.

Infrared Rays Determine water temperature Rapidly moving water does not have time to absorb infrared rays Lakes and ponds become warm because they absorb infrared rays Upper zone of ocean absorbs infrared rays so only surface is heated Surface temperature varies with latitude Deep seawater is very cold (Don’t draw diagram until the end)

How Did the Oceans Form? About 4.5 billion years ago, there were no oceans. Sometime before 4 billion years ago, water vapor in the atmosphere condensed and fell as rain. The rain filled the deeper levels of Earth’s surface and the first oceans began to form.

The Global Ocean 3/21/2011 All waterways on earth are connected to the oceans because almost all watersheds empty into the ocean. Minerals & gases are carried along with the water and dissolve into seawater

The Global Ocean The ocean affects every person on Earth 3/21/2011 The Global Ocean Oceans produce most of the earth’s rain and oxygen (over 50%) The ocean affects every person on Earth

Divisions of the Global Ocean 3/21/2011 Pacific Ocean – largest (North and South) Atlantic Ocean - half the volume of Pacific (North and South) Indian Ocean - 3rd largest Southern Ocean-Newest recognized in 2000 Arctic Ocean – smallest with most covered in ice

Divisions of Ocean All five of Earth’s oceans are connected to each other by the ocean currents creating 1 global ocean

Ocean water contains salt Ocean water is 96.5% water Plus, ions of dissolved salts Evaporation removes pure water Leaving salt behind Low levels of nutrients (nitrogen and phosphorus) Oxygen is added by plants, bacteria, and atmospheric diffusion

Ocean water is vertically structured Temperature declines with depth Heavier (colder, saltier) water sinks Light (warmer, less salty) water stays near the surface Temperatures are more stable than land temperatures Water has high heat capacity (heat required to increase temperature by a given amount) It takes more energy to warm water than air Oceans regulate Earth’s climate They absorb and release heat The ocean’s surface circulation moves heat around

What’s in Ocean Water? Oceans contain many dissolved solids and gases. Dissolved solids like minerals and salts are eroded from the land as rivers travel to the sea. When the water evaporates, these minerals are left behind. This is why the ocean is salty. Some gases become dissolved in the ocean through wave action. Others come from photosynthesis and respiration of ocean organisms.

Characteristics of Ocean Water Dissolved solids: Sodium chloride, or table salt, is the most abundant dissolved solid in the ocean. Other solids are also found in ocean water. (Draw next slide)

Salinity Amount of dissolved salts present in a sample of ocean water Described in parts per thousand ‰ this is the notation for parts per thousand Changes in Salinity - Climate and water movement affect salinity. Costal water in cool, humid places has a low salinity. Slow-moving bodies of water have higher salinity than other parts of the ocean do. Salinity in various regions all differ Range from 33‰ to 40‰ Average Salinity is 35‰ Salinity-generally increases with depth (WRITE THIS IN!)

Characteristics of Ocean Water Dissolved Gases Nitrogen, oxygen, and carbon dioxide are the main gases dissolved in ocean water. More than half of Earth’s oxygen comes from the surface layers of the ocean. About 93% of the world’s carbon dioxide is dissolved in the ocean.

CO2 Has more than 60 times that is the atmosphere Called carbon sink can trap CO2 for thousands of years

Behavior of Gases in Water You know that warm water dissolves solids more easily than cold water. Try to dissolve sugar in cold and warm water, and you’ll see that it’s true. Gases behave in the opposite way. Cold water dissolves gases more easily than warm water. Open a warm and a cold soda. The warm one will fizz more and go flat more quickly. This is because the CO2 dissolved in the soda stays dissolved easier in cold water.

Behavior of Gases in Water Pressure also plays a role in how easily gases dissolve in water. If the water is under high pressure, gases dissolve more easily than water under no pressure. To keep CO2 dissolved in soda, it is bottled under pressure. When you open the soda, it loses pressure. The CO2 fizzes out and the soda eventually goes flat.

Temperature Zones (Draw in box!) 3/21/2011 25°C Surface 0m 23°C Surface Zone 300m 5°C Thermocline 700m 1°C Deep Zone to1200m

Temperature Zones Sunlight heats the top 100m of the surface zone 3/21/2011 Sunlight heats the top 100m of the surface zone Surface currents mix the heated water with cooler water in surface zone

Surface Temperature Changes 3/21/2011 Two factors affect surface temperatures: Latitude-water along equator is warmer because it receives more direct sunlight (So temp would be lowest at the poles.) Time of year more direct sun during summer, so surface zone is heated more

FYI - A Global Thermostat 3/21/2011 Ocean absorbs and holds energy from sunlight Releases energy more slowly than land does. This keeps our temps from going to extremes every day/night. Ocean currents move warm water around our planet

Ocean Currents Oceans don’t just sit still. Currents move ocean water from place to place, moving nutrients and organisms with it. One very important kind of ocean current is upwelling.

Upwelling Defined as the movement of deep, cold, nutrient rich water to the surface. Because many nutrients sink to the bottom of the ocean, upwelling brings nutrients up where surface organisms can use them. These nutrient rich waters near the surface create productive fisheries.

Upwelling Wind blows away from the shore, taking surface water with it. Deep water “wells up” to replace the surface water. This brings deep, cold, nutrient rich water up to the surface.

Draw & label this diagram under the Infrared Ray section Draw & label this diagram under the Infrared Ray section! Remember to draw the wavelength in the diagram!

Video Clips (15 min) Exploring Oceans - https://www.youtube.com/watch?v=3GRA7ilM708 Birth of an Ocean - https://www.youtube.com/watch?v=PoV4qSwg7nc 5 Oceans of the Earth - https://www.youtube.com/watch?v=vy6dj_ZWOos Why is the Sea Salty? - https://www.youtube.com/watch?v=EIDSMzXXzLM Upwelling – http://www.youtube.com/watch?v=APMzM-xYlOs Observe how upwelling occurs - http://www.classzone.com/books/earth_science/terc/content/visualizations/es2405/es2405page01.cfm