OCN 102 Oceans I

OCN 102: Introduction to the Environment, Climate Change and Sustainability

  • Instructor: Dr. Michael Cooney

  • Location: Post 104

Climate Change and Ocean Currents

  • Main Idea: Climate change is affecting ocean currents, which play a critical role in shaping weather patterns on both sides of the Atlantic.

    • Increased heat in the oceans can lead to:

      • More frequent heat waves in Europe.

      • Elevated sea levels in North America.

      • Displacement of marine species as fish migrate northward.

The Role of Oceans in Global Climate

  • Significance:

    • The oceans are vital for global climate regulation.

    • They function as heat reservoirs, slowly absorbing and releasing heat, which stabilizes temperatures on Earth.

    • Human activities, particularly fossil fuel burning, have significantly increased ocean heat levels (approximately 90% of additional heat absorbed).

    • The oceans facilitate gas exchange, crucial for atmospheric oxygen and carbon dioxide sequestration.

Historical Perspective on CO2 and Ocean Warming

  • Key Question: What are the CO2 concentration limits that human life can tolerate?

  • Holocene Era impact: Rising atmospheric CO2 levels correlate with ocean temperatures.

The Five Oceans

  • Overview:

    • The Earth has one global ocean, divided into five major parts:

      • Atlantic Ocean

      • Indian Ocean

      • Pacific Ocean

      • Arctic Ocean

      • Southern Ocean

    • Oceans cover approximately 71% of the Earth's surface.

    • Seas: Smaller, partially land-enclosed bodies of saltwater, often nutrient-rich and abundant in marine life.

Coral Reefs

  • Definition and Importance:

    • Underwater structures formed from the skeletons of coral polyps, known for high biodiversity (over 4,000 species of fish).

    • Only found in shallow tropical waters. Coral reefs contribute significantly to marine biodiversity and are crucial ecosystems.

    • Threatened by climate change, predicted to be the first biome lost this century.

Coral Reefs - Growth

  • Formation Process:

    • Coral polyps attach to substrates and create a calcium carbonate skeleton.

    • The process is aided by organisms like parrotfish and sponges that help shape and strengthen the reef.

Coral Reefs - Formation

  • Types:

    • Fringing Reefs, Barrier Reefs, and Atolls based on their structure.

    • Growth is slow, taking up to millions of years for significant structure formation.

Coral Reefs - Degradation

  • Factors causing coral reef decline:

    • Warming waters, pollution, ocean acidification, overfishing.

    • Over 50% of coral reefs have perished in the last 30 years.

    • Coral polyps rely on symbiotic relationships with zooxanthellae for energy, which can be disrupted under stress.

Ocean Physical Properties

Salinity

  • Average seawater salinity: 35 parts per thousand (3.5%).

  • Variations occur regionally based on rainfall, river discharge, and evaporation rates.

Temperature

  • Ocean temperatures: range from -2°C to over 30°C based on the location, with the warmest waters near the equator.

  • Notable warming trends especially in the Indian Ocean.

  • Presence of thermocline—a layer of rapid temperature change affecting weather and hurricane predictions.

Ocean Currents

Global Ocean Conveyor Belt

  • Significance:

    • A massive global current system driven by thermohaline (density-driven) and surface winds.

    • Influences climate by stabilizing temperatures and redistributing heat globally.

Ocean Currents Dynamics

  • The Atlantic Meridional Overturning Circulation (AMOC) is crucial for the global system, mixing warm and cold waters.

  • Changes in freshwater input from melting ice and increased rainfall are disrupting the AMOC, leading to potential extreme weather conditions.

Upwelling

  • Concept: Occurs when surface winds push away water, causing nutrient-rich water to rise.

  • Global warming is likely to weaken upwelling, diminishing fishery productivity.

Conclusion

  • Understanding the interaction between climate change and ocean currents is essential for predicting future environmental impacts and marine biodiversity losses.

  • The complexity of these systems emphasizes the need for comprehensive climate action.