Lecture Notes: Understanding Sea Level Rise

Introduction

• Key Concept: Sea level rise is a significant issue affecting coastal populations globally.
• Specific Example: New York City is experiencing sea level rise 1.5 times faster than the global average.

Causes of Sea Level Rise

1. Climate Change

• Global Warming: Melting of ice sheets and glaciers contributes to rising sea levels.
• Thermal Expansion: As the ocean warms, water expands, causing sea levels to rise.

2. Ocean Surface Topography

• Non-Uniform Surface: Oceans have "hills and valleys" due to various factors.
• Gravity's Role:
  • Large masses like ice sheets exert gravitational pull on water.
  • Example: Ice in Antarctica pulls water towards it; as ice melts, gravity weakens, shifting water away from Antarctica.

3. Ocean Currents

• Gulf Stream: A major current in the Atlantic affects water levels.
  • Operates like a conveyor belt moving water away from the US East Coast.
  • Melting glaciers add fresh water, reducing water density, slowing the current, and piling up water along the US East Coast.

Land Movements Affecting Sea Level

Relative Sea Level Changes

• Land Sinking or Rising: Changes the relative sea level.
• Example Locations:
  • California: Tectonic activity causes land uplift, leading to falling sea levels.
  • Louisiana: Land sinking due to sediment deposition from the Mississippi River.

New York's Unique Situation

• Historical Ice Sheet Impact:
  • 20,000 years ago, New York was on the periphery of a massive ice sheet.
  • The weight pushed down Earth's mantle, causing surrounding land to rise (peripheral bulge).
  • Post-ice age, land is slowly sinking back.

Conclusion

• Complex Interactions: Sea level rise is influenced by warming oceans, melting ice, gravitational shifts, and land movements.
• Future Uncertainty: Scientists understand current dynamics well but are less certain about future impacts due to continued CO2 emissions.

Final Thought

• Dynamic Earth: The planet is constantly changing, not a static entity.

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