Weather & Ocean Currents
Earth is heated unevenly Causes: Earth is round Earth is tilted on an axis Earth s orbit is eliptical Effects: Convection = vertical circular currents caused by temperature differences Warm air is less dense and rises & is replaced by cooler air
Weather Water vapor in the air relates to air temperature, density, and pressure As temperature rises, air pressure increases and density decreases Adding water vapor decreases the density more Deserts have little water vapor a lot of temperature variation Weather is important because It redistributes heat around the Earth Precipitation is the primary source of water
Atmospheric Circulation Cells Distinct air masses with individual air flow patterns Hadley Cells Between equator and 30 o N or S Ferrel Cells Between 30 o & 60 o North or South Polar Cells Between 60 o & the poles Trade winds caused by air rising at the equator and moving northward or southward Westerlies = wind from Hadley cells that continues toward the poles & shifts to the west.
Monsoons & Cyclones Monsoons = seasonal wind pattern changes cause by heating or cooling on the continents Summers have significant rainfall Winters with little rain Cyclones = large rotating storm systems of low pressure with converging winds at the center Extratropical & Tropical
Coriolis Effect Currents move clockwise in the Northern hemisphere Currents move counterclockwise in the Southern hemisphere Caused by Earth s Rotation Creates Gyres
Ocean Heating & Cooling Earth s usable energy comes from the sun. Excess energy is radiated back to the atmosphere through evaporation & radiation Greenhouse gasses block heat radiation, causing global warming Most direct sunlight between 30 o N & 30 o S Warmest oceans Uneven heating
Causes of Currents Wind Surface currents Changes in sea level & resulting pressure gradients Gyres Variations in water density Thermohaline circulation Upwelling & downwelling
Importance of currents Transport heat from warm areas to cool areas Moderate global temperature & climate
Surface Currents 10% of ocean water Move the upper 400 meters of ocean water Caused by winds Move in predictable patterns
Gyres Circular flow patterns around the edge of ocean basins There are 5 major gyres: North Atlantic Gyre South Atlantic Gyre North Pacific Gyre South Pacific Gyre Indian Ocean Gyre
Upwelling An upward vertical current that brings deep water to the surface Coastal upwelling occurs when the wind blows offshore or parallel to shore. Biological Effects: Nutrients & cold water are carried to the surface Related to significant weather patterns
El Niño Every 3 to 8 years, normal weather patterns over the Pacific Ocean change Trade winds weaken or reverse High & low pressure systems rearrange Upwelling along the S. American coast stops Warmer water moves toward the coastline Fewer nutrients are available for marine life
Effects of El Niño Increased rain in normally dry areas Western coastlines of N. America & S. America Causes floods Decreased rain in normally rainy areas Droughts & fires in Australia & Indonesia Disruptions in animal food chains and reproduction Fisheries off the coast of S. America Whole marine ecosystems decline
Downwelling A downward vertical current that pushes surface water to the bottom Cycles nutrients to the deep ocean ecosystems and sediments
Thermohaline Circulation Water motion caused by changes and differences in density Thermo = heat Haline = salinity Occur in the deep ocean Wind is not a factor
Oceanic Conveyor Belt The interconnected flow of currents that redistribute heat Connects surface and deep currents Transports heat and salt throughout all oceans