Lecture Notes: North Pacific Garbage Patch and Ocean Currents

The North Pacific Garbage Patch

• Largest human trash dump in the world, located in the Pacific Ocean.
• Composed of several trash vortices, not a solid island.
• Mostly a "soup" of tiny microplastics.
• Estimated size: ~700,000 km² (about the size of Texas).
• One of five giant trash collections in oceans globally.

Ocean Currents and Trash Movement

• Trash moves from inland to oceans via currents.
• Ocean currents act like rivers of energy, moving in predictable patterns.
• Driven by differences in density and pressure, influenced by insolation (solar radiation).

Factors Affecting Ocean Currents

• Temperature and Density: Warm water near the equator is less dense, affecting flow.
• Salinity: Saltier water is denser, influencing movement.
• Sea Surface Height: Varies due to thermal expansion and pressure differences.
• Coriolis Effect: Influences movement direction due to Earth's rotation.

Interaction of Winds and Currents

• Winds transfer energy to ocean currents through friction.
• Subtropical high-pressure areas contribute to current patterns known as gyres.
• Gyres flow clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.

Example: Journey of a Water Bottle

• Starts in Hawaii, moves via Equatorial Current, Kuroshio Current, North Pacific Current, and California Current.
• Travels vast distances due to predictable ocean currents.

Global Ocean Circulation

• Surface Currents: Transport warm and cold water, regulating regional temperatures.
• Deep Currents: Move slowly, circulate nutrients, and are part of thermohaline circulation.
• Upwelling and Nutrient Movement: Vital for fisheries, supports global fish harvest.

Human Impact and Marine Debris

• Marine debris, particularly plastics, are pervasive in oceans.
• Shipping contributes to pollution; containers often lost at sea.
• Connection of global economies and marine ecosystems through ocean circulation.

Challenges and Questions

• Ocean pollution is transboundary; difficult to attribute responsibility.
• Environmental Responsibility: Who cleans international waters?
• Balancing human needs with environmental protection poses significant challenges.