Oceans I Notes Outlines on the front table Oceanography the science of our oceans that mixes biology, geology, chemistry, and physics (among other sciences) to unravel the mysteries of our seas. Divisions of Oceanography Chemical Oceanography study of chemical reactions Biological Oceanography study of living things in their environment Divisions of Oceanography (cont.) Physical Oceanography study of changes in motion of sea water Geological Oceanography study of sediments & topography The Global Ocean Covers 71% of the Earth s surface Salt Water 97% of all water on Earth The Hemispheres of the Earth Northern Hemisphere 39% land Land Hemisphere Southern Hemisphere 19% land Water Hemisphere 1
Hydrosphere Describes the combined mass of water found on, under, and over the surface of the a planet. Composition of Seawater Main salts/minerals present in oceans (ppt): 1. NaCl (halite) 3.5% 2. MgCl 2 3. Na 2 SO 4 4. CaCl 2 5. KCl and others Salinity amount of dissolved salt in water; usually expressed as parts per thousand (ppt) Average salinity = 33 38 ppt (3.3-3.8%) Where do the salts come from? What affects salinity? 1. Weathering of rocks and minerals 2. Outgassing from Earth's interior 3. Hard parts of marine organisms (i.e., shell material) 2
What affects salinity? Increase salinity (remove water) Evaporation Formation of sea ice Decrease salinity (add water) Precipitation Sea ice melting Regions of heavy precipitation at the Equator shows lower surface salinity than regions of excess evaporation at the mid-latitudes that shows increased surface salinity. What is Ocean Water Composed of? Divisions of the Global Ocean 5 characteristics 1. Salinity 2. Currents 3. Seafloor depth 4. Submarine ridges 5. Some definable continental boundaries. Divisions of the Global Ocean Pacific Pacific Ocean Atlantic Ocean Indian Ocean Southern Ocean Arctic Ocean 3
Pacific Ocean Largest and Deepest Holds 50% of Earth s ocean water Covers 31% of Earth s surface Average depth = 4.3 kilometers (2.7 miles) Mountain building along margins Abundant islands (mostly volcanic) Marianas Trench 6.8 miles deep Atlantic Atlantic Ocean 2nd largest ocean 23% of Earth s ocean water Avg. depth = 3.9 km (2.4 miles) Mid-Atlantic Ridge Few islands Large sediment deposits from rivers (Amazon & Congo 25% of world s river discharge) Indian Indian Ocean 3 rd largest ocean Avg. depth = 3.9 km (2.4 miles) 20% of Earth s ocean water Mostly in the S.Hemis. Abundant fresh water due to river discharge (Ganges, Brahmaputra, Indus) Southern (Antarctic) Defined in 2000 Starts at 60 o S latitude Surrounds Antarctica 5.5% of ocean water 4
Arctic Arctic Ocean 1.5% of ocean water Smallest & Shallowest Surrounds the North Pole Almost completely surrounded by land Covered with sea ice most of the year Extension of the Atlantic Ocean Temperature Surface water temperature varies with amount of solar radiation received Variation with depth Low latitudes = rapid decrease in temp. w/depth (thermocline) High latitudes = no rapid change in temp. w/depth Determined based on light: Ocean Density Determined based on density: Density = mass/volume Depends on: temperature and salinity Determines water s vertical position in the ocean Pure water = 1 g/cm 3 Remember densest water is COLD & SALTY 5
Ocean Layers Determined based on density: 1. Surface mixed zone (Epipelagic): 2%, sunlit zone warmest from solar energy, mixed by waves, 300 m, most saline 2. Transition zone (Mesopelagic): 18%, Twilight Zone, 200 1000 m, includes thermocline 3. Deep zone (Bathypelagic): 80%, Midnight Zone, just slightly above or at freezing, not very saline Ocean Layers Determined based on Light Photic Zone - Sunlit layer of water Deepest in tropics Typical value: 100 meters Photosynthesis occurs here Most ocean life found here Aphotic Zone Complete darkness Circulation The color red is the first color absorbed by water so therefore most water we see is blue. Atmospheric Circulation Depends on density Surface Ocean Circulation Depends on the wind Deep Ocean Circulation Depends on density Why is Ocean Circulation Important? Ocean Circulation Transports heat from equator to poles Transport nutrients and organisms Influences weather and climate 6
Upwelling is the force that vertically moves cooler, nutrient rich water from approximately 1000 feet below the surface to the near surface. Surface Currents *Coriolis Effect - ocean currents are directed to the right (clockwise) in the northern hemisphere and to the left (counterclockwise) in the southern hemisphere Deep Ocean Currents (Thermohaline) Two factors are important in creating a dense mass of moving water: 1. Temperature 2. Salinity *Colder and salty water is denser than warmer, less salty water. Waves A Wave is a rhythmic movement that carries energy through matter or space. In oceans, waves move through seawater Caused by: Wind Earthquakes Gravitational force of the Moon and Sun (tides) Parts of a Wave Crest highest point of a wave Trough lowest point of a wave Wave Height vertical distance between the crest and the trough Wavelength horizontal distance between two crests or two troughs Wave Parts Wavelength Wave Height Crest Still Water Trough 7
Waves Caused by Wind When wind blows across a body of water, friction causes the water to move along with the wind. Wave Height depends on Wind speed Distance over which the wind blows Length of time the wind blows Earth s Oceans 8