Paper 1-Oceans and Coastal Margins

What drives ocean currents?

• driven by energy friction of wind against water from surface winds

• how the wind energy interacs with the coriolisis effect

• how the wind energy interacts with other currents

• how the wind energy interacts with geographical features such as continents and islands

What are ‘gyres’ and how do they form? What do they impact?

• large rotating ocean currents in the center of an ocean basin

  • there is one in all of earth’s ocean basins

• they form due to geostrophic flow —> where the Coriolis effect is the strongest influence on these currents

• westerly or easterly trade winds push water in one direction, Coriolis effect turns the water 90 degrees which causes it to pile up and form hills

• the hills create a difference in pressure —> center is more elevated and higher in pressure

• water flows along lines of equal pressure around the hill instead of down it

• gyres influence ocean currents which influence other stuff (see other flashcard)

What is the ocean conveyor belt? Explain how it moves water?

• driven by thermohaline circulation

  • thermo =temp, haline=salt, these factors influence water’s density

• Warmer water has a lower density and rises while cold water sinks

• water density increases with salt content

  • salty cold water is the densest and is located at the poles

• The return flow of fyres move water around based on these thermohaline factors

  • warm ocean currents move water away from the equator while cold ocean currents move water away from the poles

Give two examples of ocean currents that show the importance of the ocean conveyor belt

• Gulf Stream moves warm water through the North Atlantic gyre and towards Northwest Europe which keeps temperatures mild in winter

  • without it, major cities like London and Paris would ressemble the arctic

• Benguela current transports cold nutrient dense water towards SW Africa for countries like Angola, South Africa, and Namibia. The nutrient dense water support aquatic life.

  • Fishing is a major industry in these countries and not only supports economic livelihood but also balanced protein rich diets (synthesis)

What is the walker circulation cycle?

• Walker circulation cycle is the normal atmospheric circulation pattern in the ocean

  • warm water is pushed near Asia and Australia by winds from SW South America

  • Cold water is upwelled from below and replaces it

• This creates a natural temperature difference in the tropical pacific

  • warmer water near Australia, cold water near Peru

• Warmer water warms the air, whic causes the air to rise more vigourously

  • leads to more clouds, rain, and uncertain weather near Australia

• Cooler dryper air in the East

What is the El Nino Southern Oscillation?

• trade winds weaken, so there is less push of warm surface water to Australia/Asia and less upwelling of cold water near South America

  • this leads to more rainfall/clouds in the west, leaving countries like Peru more vulnerable to flooding

  • disrupts natural rainfall in Australia/Asia, leaving countries like Australia and India more prone to droughts

• ENSO is associated with warmer sea-surface temperatures across the pacific

  • warmer than 28 degrees celcius

What is the La Nina cycle?

• opposite of La Nino —> normal trade winds are stronger

• This pushes more warm water to the western pacific (Australia/Asia) and increases upwelling in the Eastern pacific

• Leads to increased rainfall in Asia/Australia which puts them at risk for flooding

• Leads to risk of drought in South America

What are 2 examples of El Nino and La Nina events?

El Nino:

• Colombia, El Niño 2015-2016

  • Colombia experienced severe drought during the 2015/16 ENSO event

  • 65% of the country’s electricity comes from hydropower, the lack of rainfall dried up dams