How the Ocean Affects Climate

How the Ocean Affects Climate

Introduction

  • Exploration of how ocean water movement and mixing influence climate.

  • Example of surfer's location hints at ocean temperature; potential locations include:
      - West Coast: Cooler Pacific Ocean, mild year-round climate (e.g., San Diego).
      - Southeast Coast: Warmer waters in the Atlantic Ocean (e.g., Charleston, South Carolina).

  • Question posed: Why is the water colder off California's coast than off the East Coast despite similar latitudes?

  • Objectives of the lesson:
      - Understand properties of the ocean in storing and releasing energy.
      - Learn about data collection on ocean temperature and movement by scientists.
      - Explore the phenomenon of El Niño and its impacts on climate.

The Ocean and Energy Storage

  1. Energy Storage
       - Ocean vs. Atmosphere Temperature Variance:
         - Ocean warms and cools more slowly than the air above due to its size and energy absorption capacity.
         - Water requires more energy to change temperature compared to other substances.
       - Example: Pool water retains warmth overnight due to energy absorption from sunlight.
       - Ocean controls Earth's temperatures by absorbing energy:
         - Cooler ocean water absorbs heat from warmer air, redistributing energy globally.

Distributing Solar Energy

  1. Temperature Mapping
       - Ocean temperature varies across the globe, with warmer waters near the equator.
       - Satellite data shows temperature range of about 30°C:
         - Red regions indicate warmth, while purple indicates cooler temperatures.
       - Sunlight Distribution:
         - Earth's shape and axial tilt affect sunlight reception; hence, varying ocean temperatures.
         - Energy perpetually moves from equator (warm) to poles (cool).
         - Unlike equilibrium in static bodies (e.g., bathtubs), ocean temperatures are dynamic and in constant flux.

Ocean Currents

  1. Surface Currents
       - Definition: Ocean currents are movements of water along specific paths, analogous to rivers.
       - Types of currents:
         - Surface currents (top 100 m) driven by global winds.
         - Deep currents occurring at greater depths.
       - Surface currents influenced by:
         - Coriolis Effect: Causes currents to curve due to Earth’s rotation.
         - Continental Deflection: Change in current direction when meeting land.
       - Gyres: Spiraling systems of ocean currents, formed through interactions of surface currents:
         - Five main gyres: North Pacific, South Pacific, North Atlantic, South Atlantic, and Indian Ocean gyres.
         - Energy Redistribution: Warm currents toward poles, cold currents toward equator, influencing coastal climates.

Impact of Currents on Climate

  1. Gulf Stream
       - Description: A warm-water surface current flowing northeast in the North Atlantic.
       - Effects on Climate:
         - Moderates climate in the eastern U.S. and Western Europe, making winters milder.
         - Temperature range from ~32°C (warm) to ~0°C (cold).
       - Comparison Example: Winter temperatures in Norway vs. Alaska.
         - Norway benefits from warm Gulf Stream air; average winter temperature: >0°C (32°F).
         - Anchorage, Alaska: Average winter temperature: −7°C (19°F).

  2. California Current
       - Description: A cold-water current flowing south along the West Coast (from British Columbia to Baja California).
       - Causes: Upwelling where surface winds push warm water away, allowing cold, nutrient-rich water to rise.
       - Effects on Climate:
         - Causes coastal areas like San Diego to have cooler summers.
         - Contribution to coastal fog due to interactions between warm moist air and cold water.

Global Ocean Convection Cycle

  1. Density Currents
       - Definition: Currents that flow due to differences in water density influenced by temperature and salinity.
       - Mechanism:
         - Cold, salty water near poles sinks as it cools.
         - The global ocean convection cycle moves water and energy through a system of surface and density currents.
         - This cycle, also known as thermohaline circulation, transfers heat and water around the globe, forming a global conveyor belt.

El Niño and La Niña Patterns

  1. El Niño
       - Definition: Climate phenomenon characterized by warmer sea surface temperatures in the Pacific Ocean (exceeds 0.5°C or 0.9°F above normal for at least five successive three-month seasons).
       - Occurrence: Happens approximately every two to seven years.
       - Effects:
         - Increased rainfall in southwest U.S., warmer winters in Northeast, drier conditions in the Pacific Northwest.
       
       La Niña: Opposite of El Niño, marked by decreased sea surface temperatures (below -0.5°C).
       - Effects: Drier conditions in the southwest U.S., cooler temperatures in the Northwest.
       - Both patterns demonstrate the interconnectedness of ocean-atmosphere systems affecting global climate.

Summary

  • The ocean regulates global temperatures by storing and distributing energy.

  • Surface Currents: Shape local climates through interactions with winds.

  • Gulf Stream and California Current: Examples of how particular currents influence regional climates.

  • Global Ocean Convection Cycle: Thalassothermal interplay shaping energy distribution.

  • El Niño and La Niña: Significant climate events illustrating how slight temperature changes can lead to significant global weather alterations.