World Geography Unit 2: World Climate Patterns Ocean Currents and Other Factors That Affect Climate
Ocean Currents Oceans cover 70% of the worlds surface All of these oceans have OCEAN CURRENTS Ocean Currents: A permanent or semi-permanent horizontal movement of unusually cold or warm surface water of the oceans. To a depth of about 100m. They closely follow the global wind currents. They vary in heat, and density. They are influenced by the Coriolis force
Three Factors That Influence Ocean Currents Three main factors that influence how and where ocean currents flow. Ocean currents are affected by the Coriolis effect They shift left or right depending on the hemisphere The size and shape of the body of water they form in. May be deflected by coastlines (Gulf Stream) Differences in temperature and salt content The heating and cooling of water by the sun drives it to form convection currents (much like in the air). Salt content also has an affect as it influences how easily the water heats or cools.
Ocean Currents cont. Ocean currents are a major factor affecting world climates. They greatly influence the average temperatures of the coastal regions that they pass by. Take a look at this ocean currents map. Follow the line of latitude that shows Newfoundland and England. Note that St. Anthony, NL is at roughly the same latitude as London, England. The climate in St. Anthony usually is quite cold in the winter with cool temperatures in the summer. They tends to get a lot of snow and can experience a very harsh winter. London, England tends to have much warmer temperatures with a more moderate temperature range and a lot of rain with very little snow.
This difference is accounted for by the presence of ocean currents This difference is accounted for by the presence of ocean currents. The cold Labrador Current brings very cold water down from the Arctic region and this current passes right along by the Newfoundland coast. The Warm Gulf Stream comes up from the Gulf of Mexico, is pushed off shore from Newfoundland by the Labrador Current and the coriolis force curves it across the North Atlantic over to England and Ireland.
Continentality and Climate (Distance from the ocean and climate) Temperature Range – The range between the highest and lowest average annual temperatures of a region. Water both absorbs and loses heat more slowly than land. This means that land close to large bodies of water tend to have more moderate temperature ranges. The land is warmed by the sun in the day and by nightfall the water has warmed so winds blowing off the water will be warmer than those blowing off land. Further inland the temperatures are more extreme from day to night and season to season as there is no large body of water present to moderate temperatures.
Continentality and Precipitation Coastal areas tend to have greater amounts of precipitation than continental areas due to their closeness to the ocean. Air is more humid over the ocean and as winds blow this humid air onshore the humidity condenses as precipitation.
Compare this precipitation map to the prevailing winds map in your textbook on page 65. Can you explain why some places are dry even though they are on the coast?
Continentality and Precipitation There are seasonal changes in wind and ocean currents because of the change in the earth’s position in relation to the sun. Winds blow from different directions depending on the time of year which can change the level of humidity in the air. The temperature of this humid air can also change if the temperature of the ocean current is different.
Seasonal variations continued: Monsoon – Comes from an Arabic word that meant seasonal wind. Now it refers to a sudden wet season in the tropics. India experiences monsoons twice in a year, winter and summer.
Winter monsoons happen when: Continental Asia heats up and creates high atmospheric pressure Wind blows southward towards the low over the Indian ocean Very little rain or a “dry season” results because the wind is blowing over dry land and does not pick up water.
Summer monsoons happen when: Continental Asia cools and creates an area of low atmospheric pressure. Wind blows northward towards the low over India Tremendous rains result because the wind is blowing over the warm Indian Ocean.
Elevation and Climate Elevation – The height of land above sea level. Elevation affects: Temperature Rainfall Conditions (windward, leeward, rain shadow) As well: Land forms and topography greatly affect wind and precipitation patterns. Winds are sensitive to Earth’s surface variations.
Mountains Mountains Mountains
Elevation & Precipitation Leeward - side of mountain opposite from windward. Windward - side of a mountain the wind blows toward. Places on windward side = more rain. Places on leeward side = less rain. Rain shadow - region on leeward side of mountain that receives little precipitation because most rain has fallen on the windward side.
Blue = Windward Brown = Leeward
Elevation and Climate cont. Air temperature decreases 2C for every 300m increase in elevation. The higher up we go the colder it gets; hence snow on mountain tops. La Paz, Bolivia, has an elevation of 3600m. Its coldest month has an average temperature of 9C. Rio de Janeiro, Brazil, has an elevation of 61m. Its coldest month has an average temperature of 25C. La Paz and Rio de Janeiro have a similar distance from the ocean and a similar latitude. However, La Paz is much colder because of higher elevation.
La Paz, Bolivia, has an elevation of 3600m La Paz, Bolivia, has an elevation of 3600m. Its coldest month has an average temperature of 9C. Rio de Janeiro, Brazil, has an elevation of 61m. Its coldest month has an average temperature of 25C. La Paz and Rio de Janeiro have a similar distance from the ocean and a similar latitude. However, La Paz is much colder because of its higher elevation.