Earth Science Oceanography Part 2

1. Marine Life Zones

2. 15.2 The Diversity of Ocean Life  Water Depth • The pelagic zone is open zone of any depth. Animals in this zone swim or float freely. • The benthic zone is the marine-life zone that includes any sea-bottom surface regardless of its distance from shore. • The abyssal zone is a subdivision of the benthic zone characterized by extremely high pressures, low temperatures, low oxygen, few nutrients, and no sunlight. Marine Life Zones

3. 15.2 The Diversity of Ocean Life  Hydrothermal Vents • Here seawater seeps into the ocean floor through cracks in the crust. • At some vents, water temperatures of 100 o C or higher support communities of organisms found nowhere else in the world. Marine Life Zones

4. Hydrothermal Vents

5. Tube Worms Found Along Hydrothermal Vents

6. 15.3 Oceanic Productivity  Primary productivity is the production of organic compounds from inorganic substances through photosynthesis or chemosynthesis.  Photosynthesis is the use of light energy to convert water and carbon dioxide into energy-rich glucose molecules.  Chemosynthesis is the process by which certain microorganisms create organic molecules from inorganic nutrients using chemical energy. Primary Productivity

7. Productivity in the Barents Sea

8. 15.3 Oceanic Productivity  Productivity in Polar Oceans • The low availability of solar energy limits photosynthetic productivity in polar areas.  Productivity in Tropical Oceans • Productivity in tropical regions is limited by the lack of nutrients. Primary Productivity

9. Water Layers in the Tropics

10. 15.3 Oceanic Productivity  Productivity in Temperate Oceans • In temperate regions, which are found at mid-latitudes, a combination of these two limiting factors, sunlight and nutrient supply, controls productivity. • Winter - Days are short and sun angle is low. - Low productivity Primary Productivity

11. Productivity in Northern Hemisphere, Temperate Oceans

12. 15.3 Oceanic Productivity  Productivity in Temperate Oceans • Summer - Phytoplankton population remains relatively low. - Strong thermocline develops so surface nutrients are not replaced from below. - Productivity is limited. • Spring - Spring bloom of phytoplankton is quickly depleted. Primary Productivity

13. 15.3 Oceanic Productivity  Trophic Levels • A trophic level is a nourishment level in a food chain. Plant and algae producers constitute the lowest level, followed by herbivores and a series of carnivores at progressively higher levels. • The transfer of energy between trophic levels is very inefficient.  Transfer Efficiency Oceanic Feeding Relationships

14. 15.3 Oceanic Productivity  Food Chains and Food Webs • A food chain is a sequence of organisms through which energy is transferred, starting with the primary producer. • Animals that feed through a food web rather than a food chain are more likely to survive because they have alternative foods to eat should one of their food sources diminish or disappear. • A food web is a group of interrelated food chains. Oceanic Feeding Relationships

15. Food Chains and Webs

17. 16.1 The Composition of Seawater  Ocean current is the mass of ocean water that flows from one place to another.  Surface Currents • Surface currents are movements of water that flow horizontally in the upper part of the ocean’s surface. • Surface currents develop from friction between the ocean and the wind that blows across its surface. Surface Circulation

18. Ocean Surface Currents

19. 16.1 The Composition of Seawater  Gyres • Gyres are huge circular-moving current systems that dominate the surfaces of the oceans. • The Coriolis effect is the deflection of currents away from their original course as a result of Earth’s rotation. Surface Circulation

20. 16.1 The Composition of Seawater  Ocean Currents and Climate • When currents from low-latitude regions move into higher latitudes, they transfer heat from warmer to cooler areas on Earth. • As cold water currents travel toward the equator, they help moderate the warm temperatures of adjacent land areas. Surface Circulation

21. False-Colored Satellite Image of the Gulf Stream

22. 16.1 The Composition of Seawater  Upwelling • Upwelling is the rise of cold water from deeper layers to replace warmer surface water. • Upwelling brings greater concentrations of dissolved nutrients, such as nitrates and phosphates, to the ocean surface. Surface Circulation

23. Effects of Upwelling

24. 16.1 The Composition of Seawater  Density Currents • Density currents are vertical currents of ocean water that result from density differences among water masses. • An increase in seawater density can be caused by a decrease in temperature or an increase in salinity. Deep-Ocean Circulation

25. 16.1 The Composition of Seawater  High Latitudes • Most water involved in deep-ocean currents begins in high latitudes at the surface.  Evaporation • Density currents can also result from increased salinity of ocean water due to evaporation. Deep-Ocean Circulation

26. 16.1 The Composition of Seawater  A Conveyor Belt • In a simplified model, ocean circulation is similar to a conveyor belt that travels from the Atlantic Ocean, through the Indian and Pacific Oceans, and back again. Deep-Ocean Circulation

27. Conveyor Belt Model

28. Cross Section of the Arctic Ocean