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Lesson 8: Currents Physical Oceanography

Lesson 8: Currents Physical Oceanography. Last class we learned about ocean layers. What are the three main ocean layers? How does temperature change with depth in the thermocline? How does it change below the thermocline?. Today we’re going to explore ocean currents.

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Lesson 8: Currents Physical Oceanography

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  1. Lesson 8: Currents Physical Oceanography

  2. Last class we learned about ocean layers • What are the three main ocean layers? • How does temperature change with depth in the thermocline? • How does it change below the thermocline?

  3. Today we’re going to explore ocean currents • An ocean current is a regular movement of large amounts of water along defined paths. • There are two primary types of ocean currents: • Surface Currents (to a depth of about 400 m) • Driving factor: Wind • Deep Currents (entirely below the effect of wind) • Driving factor: Density differences • Thermohaline circulation: Ocean circulation driven by differences in density caused by temperature (“thermo”) and salinity (“haline”) variations

  4. Influence world climate and weather Ocean navigation and transportation Support marine life (transport mechanism, food source) Transport of materials (both helpful and harmful) and energy to different regions and depths of the ocean Why are currents so important? Photo: NOAA Marine organisms like the Southern right whale (above) depend upon currents to circulate the nutrients that support their food sources

  5. An important ‘current’ event: Thermohaline Circulation (THC) • THC creates a world wide current system called the “global conveyor belt" • The global conveyor belt begins with sinking of cold, dense water near the North Pole in North Atlantic • Cold temps + Sea ice = cold, salty, dense water that sinks • Then water moves south and circulates around Antarctica, where cold salty conditions “recharge” it • The water then moves northward to the Indian, Pacific and Atlantic ocean basins • It can take around 1,000 years for water to complete one cycle of the entire global conveyor belt!

  6. A map of the global conveyor belt Photo: NASA

  7. What drives ocean currents? • Density gradients (differences) drive deep ocean currents • Upwelling brings cold, nutrient-rich water from the depths up to the surface • Wind is one of the primary drivers of surface currents

  8. Student activity In today’s activity, we will play a game to learn the names and locations of the ocean’s currents

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