Exploring Our Fluid Earth

Fig. 3.1. Hōkūleʻa, a wind-powered traditional Hawaiian voyaging canoe, returns to Honolulu, Hawai‘i from Tahiti on its 1975 inaugural voyage.

Image courtesy of Phil Uhl, Wikimedia Commons

Wind is the movement of air across the earth’s surface. Most people have experienced wind in some form, from a gentle summer breeze to a strong howling gale. Humans use wind to generate electricity and move sailing ships across the water (Fig. 3.1). Wind also plays an important role in Earth’s natural processes. Wind distributes heat around the world, powers ocean surface currents, and causes erosion of the land.

Ocean Literacy Principles

Principle 1: The earth has one big ocean with many features.

Ocean Literacy Fundamental Concept: Throughout the ocean there is one interconnected circulation system powered by wind, tides, the force of the earth’s rotation (Coriolis effect), the sun, and water density differences. The shape of the ocean basins and adjacent landmasses influence the path of circulation. (OLP 1c)

Sea level is the average height of the ocean relative to the land, taking into account the differences caused by tides. Sea level changes as plate tectonics cause the volume of ocean basins and the height of the land to change. It changes as ice caps on land melt or grow. It also changes as seawater expands and contracts when ocean water warms and cools. (OLP 1d)

Principle 3: The ocean is a major influence on weather and climate.

The ocean absorbs much of the solar radiation reaching earth. The ocean loses heat by evaporation. This heat loss drives atmospheric circulation when, after it is released into the atmosphere as water vapor, it condenses and forms rain. Condensation of water evaporated from warm seas provides the energy for hurricanes and cyclones. (OLP 3b)

The ocean has had, and will continue to have, a significant influence on climate change by absorbing, storing, and moving heat, carbon, and water. (OLP 3f)

The El Niño Southern Oscillation causes important changes in global weather patterns because it changes the way heat is released to the atmosphere in the Pacific. (OLP 3c)

Ocean Literacy Fundamental Concept: The ocean controls weather and climate by dominating the Earth’s energy, water, and carbon systems.

• Global heat transport is largely controlled by ocean circulation, specifically global thermohaline circulation. Excess heat is moved from the tropics to the poles and cool water from the poles replaces it. Flux of heat is a big component of regional weather and global climate. This equilibrium helps make earth habitable.
  
   
• Both ocean and weather conditions are linked to ocean current and atmospheric patterns. They have dominant features, but can change over time, and sometimes in predictable ways. El Niño Southern Oscillation is an example of a cycle of change in that has significant consequences for heat transport in the tropics and weather patterns globally.
  
   
• Water transport in the ocean is driven by many factors including wind, density effects, Coriolis effects, thermohaline circulation, upwelling, and tides. The location and path of ocean circulation is also driven by many factors including Coriolis effects and ocean boundaries.

These concepts will be explored in this unit through the following activities and investigations: