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# Currents

## Currents Tutorial

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When used in association with water, the term "current" describes the  motion of the water. Some currents you may be familiar with are the  motion of rainwater as it flows down the street, or the motion of the  water in a creek, stream, or river flowing from higher elevation to  lower elevation. This motion is caused by gravity. The speed and  direction (velocity) of currents can be measured and recorded.

Oceanic currents are driven by several factors. One is the rise and  fall of the tides, which is driven by the gravitational attraction of  the sun and moon on Earth's oceans. Tides create a current in the  oceans, near the shore, and in bays and estuaries along the coast.  These are called "tidal currents." Tidal currents are the only type of  currents that change in a very regular pattern and can be predicted for  future dates.

A second factor that drives ocean currents is wind. Winds drive  currents that are at or near the ocean's surface. These currents are  generally measured in meters per second or in knots (1 knot = 1.15  miles per hour or 1.85 kilometers per hour). Winds drive currents near  coastal areas on a localized scale, and in the open ocean on a global  scale.

A third factor that drives currents is thermohaline circulation - a  process driven by density differences in water due to temperature  (thermo) and salinity (haline) in different parts of the ocean.  Currents driven by thermohaline circulation occur at both deep and  shallow ocean levels and move much slower than tidal or surface  currents.

The Currents Tutorial is an overview of the types of currents, what  causes them, how they are measured, and how they affect people's lives.

The Roadmap to Resources directs you to online data and education materials from NOAA and other reliable resources. 

### Currents Lessons

              - Welcome
              - Tidal Currents 1
              - Tidal Currents 2
              Coastal Currents
              - Waves
              - Longshore Currents
              - Rip Currents
              - Upwelling
              Surface Ocean Currents
              - The Coriolis Effect
              - Surface Ocean Currents
              - Boundary Currents
              - The Ekman Spiral
              The Global Conveyor Belt
              - Thermohaline Circulation
              - The Global Conveyor Belt
              - Effects of Climate Change
              How Are Currents Measured?
              - Age of Exploration
              - What is a "knot"?
              - Shallow Water Drifter
              - Deep Ocean Drifter
              - Current Profiler
              - Shore-based Current Meters
              - How Currents Affect Our Lives?
              - References
              - Roadmap to Resources
              - Subject Review

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