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Ocean Currents 1

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Ocean currents exist to help balance the Earth's uneven heating by the Sun. The Sun deposits most of its energy at the equator, so atmospheric circulation and ocean currents transfer heat from the equator toward the poles. Winds drive 80% of this redistribution, while ocean currents account for 20%. Surface ocean currents form circular gyre patterns in ocean basins, driven by subtropical high pressure systems, and affect the locations of deserts on western continents in the Southern Hemisphere. Deep ocean currents also circulate heat but over much longer timescales of around 1,000 years.

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Ocean Currents Year 13

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What can we interpret from the following global map?

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How does ocean currents try to balance the Earth’s energy budget?

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Definitions: • An ocean current can be defined as a horizontal movement of unusually cold or warm surface water, to a depth of 100m. • Ocean currents are driven by the circulation of wind above surface waters. Frictional stress at the interface between the ocean and the wind causes the water to move in the direction of the wind.

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Ocean currents: why do they exist? • The sun’s energy is not distributed evenly; it is most concentrated upon the equator. • Atmospheric circulation and ocean currents exist as a means of transferring heat away from the equator and towards the polar regions. • Winds account for 80% and ocean currents for 20% of this redistribution.

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Surface Oceanic Circulation

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Surface Oceanic Circulation Notice circulatory cells or ‘gyres’. Driven by subtropical high pressure systems. Desert regions are located towards the western side of continents, particularly in the Southern Hemisphere. Look at the map of global ocean currents above and your mapped desert locations – what do you notice?

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The movement of sea water in the South Pacific

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‘Global ocean conveyer belt’, or deep ocean currents Begins here. BBC Wild Weather - Wet – Ocean Circulations 9 min10 to12 min12 These travel at a much slower speed than surface currents and are driven by differences in the density of seawater. Density is affected by differences in temperature and salinity. One complete circuit, as shown above, is estimated to take about 1,000 years!

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How can we connect ocean currents to the balancing of Earth’s energy budget?

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We can refer to global atmospheric circulations and ocean currents as factors that influence global climates. Can you think of two other factors?

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Latitude • Length of daylight – Compare the tropics to the poles • Angle of incidence – ‘Height’ of the sun in the sky Further reading: p. 43 in AQA Textbook

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Altitude Temperatures decrease with height above sea level Adiabatic Lapse Rate… …temperature change with height for a parcel of air that has no exchange of heat or moisture with the air surrounding it There are three types of lapse rates….

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Altitude 1. Environmental Lapse Rate (ELR) – 6.5oC per 1000m (does vary seasonally) 1. Dry Adiabatic Lapse Rate (DALR) – 10oC per 1000m 1. Saturated Adiabatic Lapse Rate (SALR) – 5oC per 1000m Lapse Rate Exercise

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Activity Account for the likely reasons behind the temperature differences recorded on the same day for the paired locations: 1. Berlin -13oC, Amsterdam -3oC in January 2. London 24oC , Hull 17oC in August 3. Cape Town 22oC , Stockholm -1oC in December 4. Aspen -2oC , Denver 2oC in February 5. Halifax (Canada) -4oC , Penzance 8oCin January

More Related Content

Ocean Currents 1

  • 2. What can we interpret from the following global map?
  • 3. How does ocean currents try to balance the Earth’s energy budget?
  • 4. Definitions: • An ocean current can be defined as a horizontal movement of unusually cold or warm surface water, to a depth of 100m. • Ocean currents are driven by the circulation of wind above surface waters. Frictional stress at the interface between the ocean and the wind causes the water to move in the direction of the wind.
  • 5. Ocean currents: why do they exist? • The sun’s energy is not distributed evenly; it is most concentrated upon the equator. • Atmospheric circulation and ocean currents exist as a means of transferring heat away from the equator and towards the polar regions. • Winds account for 80% and ocean currents for 20% of this redistribution.
  • 7. Surface Oceanic Circulation Notice circulatory cells or ‘gyres’. Driven by subtropical high pressure systems. Desert regions are located towards the western side of continents, particularly in the Southern Hemisphere. Look at the map of global ocean currents above and your mapped desert locations – what do you notice?
  • 8. The movement of sea water in the South Pacific
  • 9. ‘Global ocean conveyer belt’, or deep ocean currents Begins here. BBC Wild Weather - Wet – Ocean Circulations 9 min10 to12 min12 These travel at a much slower speed than surface currents and are driven by differences in the density of seawater. Density is affected by differences in temperature and salinity. One complete circuit, as shown above, is estimated to take about 1,000 years!
  • 10. How can we connect ocean currents to the balancing of Earth’s energy budget?
  • 11. We can refer to global atmospheric circulations and ocean currents as factors that influence global climates. Can you think of two other factors?
  • 12. Latitude • Length of daylight – Compare the tropics to the poles • Angle of incidence – ‘Height’ of the sun in the sky Further reading: p. 43 in AQA Textbook
  • 13. Altitude Temperatures decrease with height above sea level Adiabatic Lapse Rate… …temperature change with height for a parcel of air that has no exchange of heat or moisture with the air surrounding it There are three types of lapse rates….
  • 14. Altitude 1. Environmental Lapse Rate (ELR) – 6.5oC per 1000m (does vary seasonally) 1. Dry Adiabatic Lapse Rate (DALR) – 10oC per 1000m 1. Saturated Adiabatic Lapse Rate (SALR) – 5oC per 1000m Lapse Rate Exercise
  • 15. Activity Account for the likely reasons behind the temperature differences recorded on the same day for the paired locations: 1. Berlin -13oC, Amsterdam -3oC in January 2. London 24oC , Hull 17oC in August 3. Cape Town 22oC , Stockholm -1oC in December 4. Aspen -2oC , Denver 2oC in February 5. Halifax (Canada) -4oC , Penzance 8oCin January