ocean

Study Guide on the Ocean

Overview of the Ocean

  • The ocean is a body of salt water covering approximately 70.8% of the Earth's surface.

  • Contains 97% of Earth's water and is essential for life, influencing climate, weather, and the carbon and water cycles.

  • Traditionally divided into five oceans:

    • Pacific Ocean

    • Atlantic Ocean

    • Indian Ocean

    • Antarctic/Southern Ocean

    • Arctic Ocean

Zones of the Ocean

Vertical and Horizontal Zones

  • Pelagic Zone: Open ocean extending from the surface to the ocean floor, divided based on depth and light penetration.

    • Photic Zone:

      • Depth where light intensity is at least 1% of surface value (up to ~200m).

      • Area for photosynthesis by phytoplankton and algae, contributing to biodiversity and oxygen production (about 50% of Earth's oxygen).

    • Mesopelagic Zone:

      • The twilight zone with limited light penetration.

    • Aphotic Zone:

      • Dark deep ocean where no sunlight penetrates, relying on marine snow (organic debris) or chemosynthesis for energy.

Continental Shelf

  • Shallow area where the ocean meets land, generally under a few hundred meters deep. Human activities here significantly impact marine ecosystems.

Ocean Temperature and Salinity

  • Tropical water can reach temperatures over 30°C (86°F); polar water is around −2°C (28°F).

  • Deep Ocean Temperatures: Ranges from −2°C (28°F) to 5°C (41°F).

  • Salinity: Average is about 35 grams of salt per kilogram of seawater (3.5%). Influenced by evaporation and fresh water input from rivers.

Ocean Currents

  • Surface Currents: Driven by wind, affecting climate and weather patterns globally.

  • Deep Ocean Currents: Determine circulation patterns influenced by temperature and salinity (thermohaline circulation).

  • Tidal Currents: Caused by gravitational pull of the moon and the sun, influencing coastal ecosystems.

Biological Diversity

  • Known to host over 230,000 species, possibly over two million yet to be discovered.

  • Major organisms include:

    • Phytoplankton (primary producers)

    • Zooplankton (primary consumers)

    • Various marine mammals, birds, fishes, and benthic organisms.

Benefits to Humans

  • Ocean provides:

    • Ecosystem services (carbon cycling, oxygen production)

    • Seafood and resources (fishing industry valued globally)

    • Transportation (major trade routes).

Environmental Threats

  • Threats include:

    • Marine Pollution: Plastic debris, chemicals affecting ecosystems and human health.

    • Overfishing: Leads to unsustainable fish populations.

    • Climate Change: Ocean warming, acidification, altered currents, and rising sea levels pose risks to marine life and coastal populations.

Human Interaction

  • Ocean governance involves regulation and protection of marine environments through measures like marine protected areas (MPAs).

  • Notable agreements include UNCLOS and the recent High Seas Treaty to protect more areas of the ocean.

Conclusion

  • Understanding the ocean's complex systems and the threats it faces is essential for not only marine conservation but also for the well-being of human life on Earth.