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Ocean-Air Interaction Distribution of Solar Energy • Concentrated solar radiation at low latitudes • Solar radiation more diffuse at high latitudes Oceanic Heat Flow • High latitudes–more heat lost than gained • Low latitudes–more heat gained than lost Density Variations in the Atmosphere • Convection cell – rising and sinking air • Warm air rises – Less dense • Cool air sinks – More dense • Moist air rises – Less dense • Dry air sinks – More dense Movement of the Atmosphere • Thick column of air at sea level – High surface pressure equal to 1 atmosphere • Air always flows from high to low pressure. • Wind – moving air The Coriolis Effect • Deflects path of moving object from viewer’s perspective – To right in Northern Hemisphere – To left in Southern Hemisphere • Due to Earth’s rotation Merry Go Round CE Drawn CE The Coriolis Effect • Zero at equator • Greatest at poles • Change in Earth’s rotating velocity with latitude – 0 km/hour at poles – More than 1600 km/hour (1000 miles/hour) at equator The Coriolis Effect © 2011 Pearson Education, Inc. Global Atmospheric Circulation • High pressure zones – descending air – Subtropical highs – 30 degrees latitude – Polar highs –90 degrees latitude – Clear skies • Low pressure zones – rising air – Equatorial low – equator – Subpolar lows – 60 degrees latitude – Overcast skies with lots of precipitation Storms and Air Masses • Storms – disturbances with strong winds and precipitation • Air masses – large volumes of air with distinct properties Ocean’s Climate Patterns • Open ocean’s climate regions are parallel to latitude lines. • These regions may be modified by surface ocean currents. Ocean’s Climate Zones • Equatorial – Rising air – Weak winds – Doldrums • Tropical – North and south of equatorial zone – Extend to Tropics of Cancer and Capricorn – Strong winds, little precipitation, rough seas • Subtropical – High pressure, descending air – Weak winds, sluggish currents Ocean’s Climate Zones • Temperate – Strong westerly winds – Severe storms common • Subpolar – Extensive precipitation – Summer sea ice • Polar – High pressure – Sea ice most of the year Ocean Circulation Fig. CO7 Ocean currents Moving seawater Surface ocean currents Transfer heat from warmer to cooler areas Similar to pattern of major wind belts Affect coastal climates Deep ocean currents Provide oxygen to deep sea Affect marine life Types of ocean currents Surface currents Wind-driven Primarily horizontal motion Deep currents Driven by differences in density caused by differences in temperature and salinity Vertical and horizontal motions Ekman spiral Surface currents move at angle to wind because of the coriolos effect. Ekman spiral describes speed and direction of seawater flow at different depths Each successive layer moves increasingly to right (N hemisphere) Ocean currents and climate Fig. 7.9 Gulf Stream Meanders or loops Warm-core rings Cold-core rings Unique biological populations Fig. 7.17b Climate effects of North Atlantic surface currents • Gulf Stream warms East coast of U.S. and Northern Europe • North Atlantic and Norwegian Currents warm northwestern Europe • Labrador Current cools eastern Canada • Canary Current cools North Africa coast Thermohaline circulation • • • • Below the pycnocline 90% of all ocean water Slow velocity Movement caused by differences in density (temperature and salinity) – Cooler seawater denser – Saltier seawater denser Thermohaline circulation • Originates in high latitude surface ocean • Cold surface seawater sinks at polar regions and moves towards the equator Thermohaline circulation Fig. 7.26