Oceans

Oceans

1. Basic Information

   • Oceans are an important part of the Earth’s interconnected aquatic systems
     • Receive most inputs of water sediments, pollution
   • Oceans influence climate, teem with biodiversity, provide resources, and help transportation and commerce
   • Oceans cover 71% of Earth’s surface and contain 97.5% of its water
     • Oceans influence the atmosphere, lithosphere, and biosphere
     • They are a single vast body of water
       • Ocean water is 96.5% water by mass
         • Remainder is mostly ions of dissolved salts
           • Ocean water is over 33,000 parts per million salts, fresh water is 500 ppm
         • Ocean water contains high concentrations of dissolved salt
           • Oceans contain low levels of nutrients (nitrogen and phosphorus)
             • Oxygen is added by plants, bacteria, and atmospheric diffusion
               • Carbon dioxide enters the oceans from the atmosphere

2. Seafloor Topography

   • The seafloor consists of underwater volcanoes, steep canyons, mountain ranges, vast trenches, mounds of debris, and some flat areas
     • We can look at the ocean’s bathymetry (depths) and topography (landforms)
     • Continental shelves = areas of shallow, gently sloping sea floor next to the continents
       • Sea floor angles down from there at the self-slope break
         • The continental slope then drops to the deep ocean basin below

3. Solar Energy

   • Solar energy structures ocean water from surface to bottom
     • Water temperature declines with depth
       • Heavier (colder, saltier) water sinks; light (warmer, less salty) water stays near the surface
         • Surface zone (condition)
           • Warmed by sunlight and stirred by wind
             • Consistent water density down to about 150m
               • Contains about 2% of the oceans water
         • Pycnocline = zone (condition) below the surface
           • Density increases rapidly with depth
             • Contains about 18% of ocean water
         • Deep zone (condition) = zone below the pycnocline; remaining 80%
           • Dense, sluggish water
             • Unaffected by winds, storms, sunlight, temperature
           • 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

4. Surface water flows horizontally in currents

   • Currents = vast riverlike flows in the oceans
     • Move horizontally in the upper 400 m of water
       • Driven by density differences, heating and cooling, gravity, and wind
     • Currents have helped carry people across the globe
       • Also transport heat, nutrients, pollution, and the larvae of many marine species
   • Vertical movement of water affects marine ecosystems
     • Upwelling = the upward flow of cold, deep water toward the surface
       • Water is rich in nutrients
         • Sites of high primary productivity and lucrative fisheries
           • Also occurs where strong winds blow away from, or parallel to, coastlines
     • Downwelling = process in which oxygen-rich water sinks where surface currents come together
       • “Buries” CO2 in the deep waters

Images and files in the map