CH06 - CH AP T E R 6 Air-Sea Interaction Overview Examples...

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Unformatted text preview: CH AP T E R 6 Air-Sea Interaction Overview ! Examples of interactions: ! Hurricanes ! El Niño-Southern Oscillation Atmosphere and ocean (and solid earth) one interdependent system: ! Atmosphere/Hydrosphere/Cryosphere/Geosphere ! Solar energy creates winds Winds drive ocean currents and waves ! S e a s o ns Uneven solar heating at surface 1. 2. 3. Day/night Seasons Angle of incidence of solar rays " " Are there any other energy sources besides the sun? Equatorial regions get more heat Polar regions get less heat 4. 5. Rays hitting polar regions pass through more atmosphere Albedo All these effects have consequences for winds Daily and Seasonal Cycles Summer Winter Equinox (Vernal, Autumnal) Solstice Solstice S e a s o ns Warming, cooling, plant cycle, ice growth and decay… S e a s o ns ! ! Earth’s axis of rotation tilted with respect to ecliptic Tilt responsible for seasons ! ! ! ! Vernal (spring) equinox (March 20 2007) Summer solstice (June 21 2007) Autumnal equinox (Sept 23 2007) Winter solstice (Dec 22 2007) ! Seasonal changes and day/night cause unequal solar heating of Earth’s surface Seasons Sunlight Infrared Oceanic heat flow ! ! ! ! High latitudes lose heat due to albedo of ice and angle of solar rays Low latitudes gain heat from sun Ocean transfers about 1/2 of heat from low to high latitudes Atmosphere transfers other half Heat is transported by ocean and atmosphere Physical properties of atmosphere ! Absorbs heat ! Radiates heat Atmosphere mostly nitrogen (N2) and oxygen (O2) Temperature profile of lower atmosphere ! Troposphere – Troposphere temperature cools with increasing altitude Physical properties of atmosphere ! ! ! ! Warm air, less dense (rises) Cool air, more dense (sinks) Moist air, less dense (rises) Dry air, more dense (sinks) Movements in atmosphere ! ! ! Cool dense air, higher surface pressure Warm less dense air, lower surface pressure Air (wind) always moves from regions of high pressure to low… Or does it? Movements in air Non-rotating Earth ! ! Air (wind) always moves from regions of high pressure to low Convection or circulation cell Movements in air on a rotating Earth Movements ! Coriolis effect causes deflection in moving body due to Earth’s rotation Deflection to right in Northern Hemisphere Deflection to left in Southern Hemisphere Maximum Coriolis effect at poles No Coriolis effect at equator ! ! ! ! M e r r y - go - r o und Movements in air on a rotating Earth Global atmospheric circulation 1. High pressure zones Subtropical highs ! Polar highs -> Clear skies ! 2. L o w p re s s ure z o ne s Equatorial low ! Subpolar lows -> Overcast skies with lots of precipitation ! Global atmospheric circulation ! Air changes density due to: Changes in air temperature ! Changes in water vapor content ! ! Density changes drive circulation cells: Hadley cells (0o to 30o N and S) ! Ferrel cells (30o to 60o N and S) ! Polar cells (60o to 90o N and S) ! Polar Cell Ferrel Cell Hadley Cell Global wind belts 1. Trade winds • • Northeast trades in Northern Hemisphere Southeast trades in Southern Hemisphere 2. 3. Prevailing westerlies Polar easterlies Boundaries between wind belts ! Doldrums or Intertropical Convergence Zone (ITCZ) ! Horse latitudes ! Polar fronts Modifications to idealized 3-cell model of atmospheric circulation ! More complex in nature due to ! Seasonal changes ! Distribution of continents and ocean ! Differences in heat capacity between continents and ocean ! M o ns o o n winds ! S e a-bre e ze Actual mean pressure zones and winds !Northern hemisphere winds move counterclockwise (cyclonic) around a low pressure region !Southern hemisphere winds move clockwise (anticyclonic) around a low pressure region Ocean weather and climate patterns ! ! Weather – conditions of atmosphere at particular time and place Climate – long-term average of weather Coming next: n Coastal winds n Fronts and storms n Cyclones n Ocean climate regions and patterns n Greenhouse effect Coastal winds ! ! ! Solar heating Different heat capacities of land and water Se a bre e ze ! From ocean to land From land to ocean ! La nd b r e e z e ! Fronts and storms ! ! Air masses meet at fronts Storms typically develop at fronts Warm moist air cools and condenses - rain! Cold air pushes moist air upwards Tropical cyclones (hurricanes) ! ! ! Large rotating masses of low pressure Strong winds, torrential rain Classified by maximum sustained wind speed Hurricane Dennis Hurricane Hurricane morphology and movement Historical record 2005 Other factors: tides and wave propagation Hurricane destruction Fast winds ! Flooding from torrential rains ! Storm surge most damaging Historical examples: Galveston, TX, 1900 Hurricane Andrew, 1992 Hurricane Mitch, 1998 … ! ! Dennis in 2005 caused 2m surge in St Marks, 15 deaths “Supercell thunderstorm” caused 20 deaths 2 Feb in central Florida Supercell Thunderstorm Ocean supplies moisture and heat to fuel thunderstorms The ocean’s climate patterns 1. Ocean near continents influenced by land: 1. 2. 3. m o re e x tre m e t e m pe rature s dry air turbidity (light penetration) 2. 3. Open ocean’s climate regions follow latitude - angle of sun Modified by surface ocean currents CLIMATE REGIONS I Lower lat !Equatorial ocean regions – warm, lots of rain in ITCZ (Intertropical Co nve rge nc e Z o ne ) !Tropical regions – warm, less rain, trade winds !Subtropical regions – dryer, high rate of evaporation, weak winds Higher lat CLIMATE REGIONS II mid-lat ! Temperate regions – strong westerlies (from the west) westerlies ! Subpolar regions – stormy, winter sea ice, lots of snow ! Polar regions – permanent sea ice, polar high pressure Pole Ocean’s climate patterns Polar oceans and sea ice ! Sea ice or masses of frozen seawater form at surface in high-latitude oceans ! ! ! ! Begins as small needle-like ice crystals Slush turns into thin sheets that break into Pancake ice that coalesces to Ice floes Rate of formation depends on temperature ! Fur seal on pancake ice (Weddell Sea) Polar o c e a ns a nd s e a ic e Polar oceans and icebergs ! Icebergs – fragments of glaciers or shelf ice So what? B.a.U. -> 50-100yrs 1m 3ft 6m 18ft Greenhouse effect In ! ! ! Out In: Solar radiation mostly ultraviolet and visible region of electromagnetic s pe c trum Out: I nfrare d he at radiated by Earth Atm o s phe re g as e s absorb he at radiated from s urfac e o f E arth Earth’s heat budget ! Earth maintained a nearly constant average temperature because of equal rates of heat gain and heat loss 1/4 + + + = 100 1/4 GG 1/2 + + = 47 Greenhouse gases ! ! ! ! Absorb longer wave radiation from Earth Water vapor most important Carbon dioxide (CO2) next Other trace gases: methane, nitrous oxide, ozone, and chlorofluorocarbons Global warming over last 100 years ! Average global temperature increased CO2 ! Part of warming due to anthropogenic greenhouse (heat-trapping) gases such as CO 2 Int e r go v e r nm e nt a l P a ne l o n Climate Change Possible consequences of global warming ! ! Rising sea level from warming and melting glaciers Shift in species distribution ! ! Animals Trees… ! ! Warmer oceans ! More frequent (?) and more intense storms ! Changes in deep ocean circulation ! Acidification and reef destruction Shifts in areas of rain/drought Reducing greenhouse gases ! ! ! ! ! Greater fuel efficiency Alternative fuels Re-forestation Reduce CFC (chlorofluorocarbons) emissions (Montreal Protocol worked - CFC now 7% of 1989) Reduce CO2 emissions ! ! Intergovernmental Panel on Climate Change 1988 Kyoto Protocol 1997 - ? Ocean’s role in reducing CO2 ! ! ! ! ! ! Oc e an s tore s c arbon … Oceans absorbs CO2 from atmosphere CO2 incorporated in organisms and carbonate shells (tests) - biofuels? Stored as biogenous calcareous sediments and fossil fuels Ocean is repository or sink for CO2 Add iron to tropical oceans to “fertilize” oceans (increase biologic productivity) End of CHAPTER 6 Air-Sea Interaction ...
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