Module #21 - Ocean Currents and El Nino / La Nina

INSTRUCTIONS FOR TODAY

1. Watch the following short videos today in class: 

a. El Nino and La Nina Explained (8 minutes)

b. El Nino and La Nina (4 minutes)

c. What is El Nino? (3 minutes)

Be sure to make point form notes from these videos in your digital video journal. Please make sure this document is SHARED with Mr. Durk. 

2. Read the following information below in Part 1: Background and Terminology. Follow all hyper-links to external websites for activities, demonstrations and videos (if applicable). Copy only KEY information (i.e. the highlighted terms) to your digital notebook (in google docs). Mr. Durk will be doing a notebook check today for 10 of your 20 possible marks for Module #21. Your notebook may be digital or on paper ("old school"). Both are acceptable as long as you have taken notes on each of the modules in the course.

3. Part 2: Blog Posting: El Nino or La Nina Weather Events (10 marks)- See instructions below (complete on the LMS)

4. If you get done early, you can go to the Culminating Project section of the course and start researching what and how you would like to complete the Final Summative Project for the course (15% of your final grade in CGF 3M1).

DUE DATE:  Submit all components to Mr. Durk via the UG Cloud before Module #22.

Part 1: Background and Terminology


Please remember to record all definitions and content in your virtual notebook. Definitions can be found by clicking on highlighted words.

Ocean Currents

The Gulf Stream is orange and yellow in this representation of water temperatures of the Atlantic. Blue colours represent cooler water.

Huge rivers, known as ocean currents, flow through the world’s oceans. These ocean currents are not usually referred to as rivers but they act in a similar way, transporting sediments, affecting temperatures and changing climatic conditions.

Four factors affect ocean currents: prevailing winds, convection currents, the Coriolis effect, and the shape of the ocean basin.

Prevailing winds tend to blow from one direction. In Canada, for example, the Westerlies consistently blow from the west to the east, transferring some of this wind energy into wave energy. These waves tend to blow from west to east, thus creating the North Atlantic Drift. As the warm Gulf Stream current flows northeast ward along the American coast, it meets cooler water coming down from Greenland and Canada. The Gulf Stream swings eastward and turns into the North Atlantic Drift, flowing in an eastward direction across the Atlantic Ocean to Europe.

Gulf Stream (in Yellow)
Source: NASA
 

Convection currents also play a role in the ocean currents. Currents can result from differences in water temperature and salinity (saltiness of the water). Cold, less salty polar waters sink as hot, saltier waters from the Tropics flow toward the poles to replace them. Therefore ocean currents distribute vast amounts of heat throughout the planet, transferring heat from the equatorial regions to the cooler polar regions. If the salinity of the North Atlantic Ocean changes (due to global warming melting large parts of the Greenland icecap)by a flood of fresh water, this could severely affect the transfer of heat. Because Northern Europe relies on the North Atlantic Drift to supply much of its heat, Northern Europe could face serious cooling if global warming continues.

The Gulf Stream alone, flowing off the coast of North America, carries approximately 30 million cubic metres of water per second, an amount more than five times the total flow of all the freshwater rivers in the world combined!

The Coriolis effect causes water to be deflected to the right in the northern hemisphere and to the left in the southern hemisphere, due to the spinning of the earth. To help you understand the Coriolis effect, imagine you are playing catch with someone on a merry-go-round. If you are spinning around and around and you throw the ball to your friend in a straight line, they will have moved by the time the ball gets to them. As the earth spins, the water appears to be deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

The shape of the ocean basins is the final factor that shapes ocean currents. The shape of coastlines, deep troughs, and shallow areas will all play a part in determining where ocean currents flow. For example, as the Gulf Stream current flows north, along the coast of Florida, it is forced northeast (instead of north) due to the shape of the North America coast.

Please remember to record all definitions in your virtual notebook. Definitions can be found by clicking on highlighted words.

Ocean Currents influence on coastal climates

Ocean currents have a dramatic effect on climate. The temperature of an ocean current affects the temperature of the air that passes over it. Therefore, on the west coast, the North Pacific Current heats the cool, moist air that passes over it, giving the coast areas of British Columbia a warmer climate than might be expected at this latitude. Comparing Port Hardy, British Columbia, Saskatoon, Saskatchewan and Halifax, Nova Scotia it can quickly be seen how dramatic an effect ocean currents have on local climates.

CityLatitudeMean Maximum
January Temperature

Port Hardy

50 ° North

6.4 ° C

Saskatoon

52 ° North

-12 ° C

Halifax

44 ° North

- 4 ° C

Notice how warm the mean maximum temperature is in Port Hardy, despite being much farther north than Halifax and almost as far north as Saskatoon.

Saskatoon has no ocean current to moderate its climate, thus the temperatures fluctuate more throughout the winter and summer than the cities of Halifax and Port Hardy which are beside ocean currents.

Location of Chile in South AmericaOcean currents can also cause regions of the world to be arid (dry). A good example of this is the Humboldt Current which flows north along the coasts of Chile and Peru.

Air that passes over the cool Humboldt Current is cooled, reducing the amount of precipitation that is generated along the west coast of Chile and Peru. Although fog and clouds are produced, very little precipitation actually falls.

The Atacama desert is the driest desert on earth, with some parts of the desert averaging just one millimetre of rain per year!

El Nino and La Nina

The names El Nino (meaning “the little boy” and La Nina meaning “the little girl” in Spanish) refer to the Christ child because this ocean phenomena usually occurs around Christmas time. Every three to seven years off the west coast of Peru, the cold water flowing northward up the east coast of South America and then flowing eastward across the Pacific reverses. El Niño is observed when the easterly trade winds weaken, allowing warmer waters of the western Pacific to migrate eastward and eventually reach the South American. When this occurs, the surface temperature of the ocean currents off Peru can be up to seven degrees warmer than normal. The cool nutrient-rich sea water normally found along the coast of Peru is replaced by warmer water depleted of nutrients, resulting in a dramatic reduction in marine fish and plant life. This unusually w arm water off the coast of Peru increases evaporation and convection currents in the atmostphere. This has a dramatic effect on the world’s weather patterns and causes unusual and extreme weather in many parts of the world.

During an El Nino year tropical rains usually centred over Indonesia shift eastward, influencing atmospheric wind patterns worldwide. Other possible impacts include: a shifting of the jet stream, storm tracks and monsoons producing unseasonable weather over many regions of the globe.

This image compares the water temperatures observed between January 25 and February 1, 2006, to long-term average conditions for that time period. Red shows where sea surface temperatures are warmer than normal and blue where they are colder than normal. A large swath of the Pacific near the Equator is cooler than normal. In other words, a La Nina condition is in effect.
La Niña is thought to occur due to increases in the strength of the normal patterns of trade wind circulation. Under normal conditions these winds move westward, carrying warm surface water to Indonesia and Australia and allowing cooler water to upwell along the South American coast. For reasons not yet fully understood, periodically these trade winds are strengthened, increasing the amount of cooler water toward the coast of South America and reducing water temperatures. The changes in the tropical Pacific are accompanied by large fluctuations of the jet stream within the middle latitudes, shifting the point at which the stream normally crosses North America. The shifted jet stream contributes to large departures from the normal location and strength of storm paths. The overall changes in the atmosphere result in temperature and precipitation anomalies over North America, which can persist for several months.


Enrichment

To learn more about La Nina and its effects on the Canadian and global climates, check out this site: El Nino, La Nina and Weather Woes.

 Resources

  1. Surface Currents in the Atlantic Ocean, CIMAS
  2. La Niña, Environment Canada
  3. Climographs, West Coast North America
  4. El Niño

Part 2: BLOG POSTING: Complete the following assignment and submit your answers in full sentence form on the LMS.

Using the internet, you are to research the effects of El Nino or La Nina on a specific region of the earth. 

  1. Research an El Nino or La Nina event that has occurred somewhere in the world.
  2. Using a specific year, describe how El Nino or La Nina changed the normal weather conditions in the region.
  3. Use actual data to prove your points.
  4. Include human, economic and environmental costs when researching the affects of the weather changes.
  5. What can humans do to prepare themselves for this cyclical event?
  6. How can El Nino or La Nina events be predicted in the future?