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Overview Atmosphere and ocean one interdependent system Solar energy creates winds Winds drive surface ocean currents and waves Examples of interactions: El Niño-Southern Oscillation Greenhouse effect Seasons Earth’s axis of rotation tilted with respect to ecliptic orbit around sun Tilt responsible for seasons Vernal (spring) equinox (3/21) Autumnal (fall) equinox ○ sun overhead at equator (9/23) ○ Equal day/night periods ○ sun overhead at equator ○ Equal day/night periods Summer solstice (6/21) ○ sun overhead at Tropic of Cancer (23.5O N) ○ Longest day of the year in Northern hemisphere Winter solstice (12/22) ○ sun overhead at Tropic of Capricorn (23.5O S) ○ Shortest day of the year in Northern hemisphere Seasons Seasonal changes and day/night cause unequal solar heating of Earth’s surface Arctic circle (66.5O N) latitude receives direct sunlight all day on summer solstice no direct sunlight during winter solstice Antarctic circle – reverse of above Seasons Fig. 6-1 http://go.owu.edu/~jbkrygie/krygier_html/geog_111/geog_111_lo/geog_111_lo05.html Uneven solar heating Angle of incidence of solar rays per area Greater the angle, solar energy spread over more area Equatorial regions more heat Polar regions less heat Thickness of atmosphere – absorbs or reflects energy ○ Think about South Florida compared to Maine Uneven solar heating Albedo Albus = white % incident radiation reflected back into space Affected by angle of sun – more angle , more reflected Affected by type of surface ○ Snow/ice reflects more ○ Water surface absorbs more ○ Land absorbs most Day/night and seasonal cycles affect solar heating http://go.owu.edu/~jbkrygie/krygier_html/geog_111/geog_111_lo/geog_111_lo05.html Oceanic heat flow Depending on latitude, there is a net heat gain (closer to equator) or net heat loss (closer to poles) Due to albedo of ice and high incidence of solar rays discussed above Exchange of heat between equatorial and polar regions via ocean and atmospheric circulation Physical properties of atmosphere http://www.ux1.eiu.edu/~cfjps/1400 Atmosphere is comprised of gases and dust mostly nitrogen (N2) – 78% Oxygen (O2) – 21% CO2, water vapor, ozone (O3) are variable Physical properties of atmosphere • Fig. 6.4 Temperature profile of lower atmosphere: • Troposphere • temperature cools with increasing altitude • Stratosphere - From 11 - 45 km • Contains the ozone layer • Little vertical mixing • Gets warmer with increasing elevation solar radiation • Mesosphere above stratosphere ○ Troposphere - Up to 11 km Weather layer with lots of mixing Gets cooler with increasing elevation (decreasing air pressure allows expanding/cool ing air) http://tonydude.net/NaturalScience100/Topics/2Earth Physical properties of atmosphere Warm air, less dense (rises) Cool air, more dense (sinks) Moist air, less dense (rises) Dry air, more dense (sinks) Fig. 6.5 Winds, Wind Belts and Climate Introductory geography ○ ○ ○ Equator = 0O latitude Earth rotates from west to east Wind direction indicated by direction winds are blowing from http://www.lakelandsd.com Movements in atmosphere Fig. 6.6 Air (wind) always moves from regions of high pressure to low Cool dense air, higher surface pressure Warm less dense air, lower surface pressure Air movements over non-rotating Earth • Convection or circulation cell • • • Air heated at equator warm (less dense) air rises Surface air moves in to replace rising air mass Air expands & cools as it rises • As it cools, becomes more dense • Warm air holds more moisture than cooler air • As air cools moisture condenses & forms clouds/precipitation Fig. 6.7 Air movements over a rotating Earth Coriolis effect causes deflection in moving body due to Earth’s rotation to east Most pronounced on objects that move long distances across latitudes Deflection to right in Northern Hemisphere Deflection to left in Southern Hemisphere Maximum Coriolis effect at poles No Coriolis effect at equator Movements in air on a rotating Earth Rotational velocity increases approaching equator Fig. 6.9 Global atmospheric circulation Circulation cells as air changes density due to: Changes in air temperature Changes in water vapor content 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) 6 cells of windbelts and boundaries: Intertropical convergence zone Doldrums Horse latitudes Tradewinds Westerlies Polar front Polar easterlies • 1. Intertropical convergence zone (boundary) • Air warms & rises at equator low surface pressure (rising air) poduce light winds = doldrums • Long ago sailing ships became stuck here because of lack of winds Rising air cools cloud belt & precipitation • • Winds split at top of troposphere • Move toward both poles in spiral fashion, cool • Sink at about 30O N & S latitude • 2. Horse latitudes (boundary) – low winds, high pressure ridge • Dry, cool, sinking air • Sailors would also get “stuck” here and would through horses overboard to conserve water • Winds: • 3. Tradewinds return to Equator, deflected west • 4. Westerlies move toward poles, deflected east • Winds converge at 50-60O N & S with polar air • • • 5. Polar Front (boundary) - warm air rises (low press./clouds) Upper air splits & cools sinks near poles Winds: • 6. Polar Easterlies – air sinks near poles, moves from poles toward equator Global atmospheric circulation High pressure zones Subtropical highs Polar highs Clear skies Low pressure zones Equatorial low Subpolar lows Overcast skies with lots of precipitation Global wind belts and boundaries – review Trade winds Northeast trades in Northern Hemisphere Southeast trades in Southern Hemisphere Prevailing westerlies Southern hemisphere Northern hemisphere 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 Winds are more complex in nature due to… Seasonal changes Distribution of continents and ocean Differences in heat capacity between continents and ocean ○ Monsoon winds Actual pressure zones and winds Fig. 6.11 Seasonal Pressure and Precipitation Patterns http://www.wunderground.com/US/Region/US/2xFronts.html Ocean weather and climate patterns Weather – conditions of atmosphere at particular time and place Climate – long-term average of weather Northern hemisphere winds move counterclockwise (cyclonic) around a low pressure region Southern hemisphere winds move clockwise (anticyclonic) around a low pressure region Hurricane Francis 9/3/04 http://apod.nasa.gov/apod/image/0409/frances2_noaa.jpg Cyclones and Anticyclones Coastal winds Caused by solar heating & different heat capacities of land and water Sea breeze From ocean to land During day, land heats air rises draws cooler ocean air onto coast Land breeze From land to ocean At night, warmer ocean water rises, draws cooler land air over coast Fig. 6.13 Fronts and storms Air masses Large volumes of air, meet at fronts Storms Disturbances with strong winds, precipitation, often with thunder and lightning typically develop at fronts Fig. 6.14 Fronts and storms United States mostly affected by polar air masses in winter and tropical air masses in summer Fig. 6.14 Warm front contact between moving warm air mass with cooler air mass More extensive, lighter rains Cold front contact between moving cold air mass with warmer air mass Usually steep front, with heavier, but briefer, rains Clear skies follow behind Cold Fronts and Warm Fronts Tropical cyclones (hurricanes) Caused by release of energy (latent heat of condensation) Low-pressure system breaks off equatorial low-pressure belt Surface winds feed moisture into storm ○ As water vapor condenses, heat released warms air ○ Rising warm air draws in more moist air fueling cyclone ○ Large rotating masses of low pressure with calm “eye” (< 25 mph winds) Strong winds, torrential rain outside eye Fig. 6.16 Hurricane movement At low latitudes, affected by trades move west Curve toward right in No. hemisphere cooler water, influenced by westerlies Hurricane Wilma 10/25/2005 http://cimss.ssec.wisc.edu/tropic/archive/montage/atlantic/2005/WILMA-track.gif Fig. 6.17 Hurricane Wind Patterns Tropical cyclones (hurricanes) Classified by maximum sustained wind speed Tropical storm – 39-73 mph winds Hurricane – above 74 mph winds Hurricane Jeanne 09/26/2004 http://www.mapwatch.com/news-blog/images/hurricane-jeanne-track-map.gif http://coastal.er.usgs.gov/hurricanes/jeanne/images/jeanne_radarLG.jpg Table 6.5 Hurricane destruction Fast winds Flooding from torrential rains Storm surge most damaging increased water levels from low pressure at eye On top of tide, most damaging at high tides Storm waves on top of storm surge Historical examples: Galveston, TX, 1900 Hurricane Andrew, 1992 Hurricane Mitch, 1998 Hurricane Katrina, 2005 Ocean climate patterns Equatorial regions ○ Warm, lots of rain Tropical regions ○ Warm, less rain, trade winds ○ South Florida is tropical, defined rainy and dry season Subtropical regions ○ Warm, lots of wind and evaporation, find dessert areas Temperate regions ○ Strong westerlies Subpolar regions ○ Cool, winter sea ice, lots of snow Polar regions ○ Cold, ice Polar oceans and sea ice Sea ice or masses of frozen seawater form in high latitude oceans Begins as small needle-like ice crystals ○ Pushes out dissolved salts dense brine ○ Ice is much lower salinity Rate of formation depends on temperature Polar oceans and icebergs Icebergs – fragments of glaciers or shelf ice Fig. 6-23 http://static.howstuffworks.com/gif/iceberg-calving.jpg Climate Change Global warming (Climate Change) Average global temperature increased Part of warming due to anthropogenic greenhouse (heattrapping) gases such as CO2 http://healthandenergy.com/images/carbon%20dioxi de%201700-2000.jpg http://earthobservatory.nasa.gov/Library/GlobalWarmi ng/Images/temperature_vs_co2_rt.gif Greenhouse effect Solar radiation enter atmosphere Some of that radiation is reflected to space Some of it is reflected back towards Earth by trace gases and particles in the atmosphere Elevated levels of carbon dioxide, methane, etc can increase that effect Literally “trapping” more heat in the atmosphere close to the Earth Fig. 6.24 Atmospheric Energy Balance Greenhouse gases Absorb longer wave radiation from Earth Many “greenhouse gases” Water vapor – most common and important Carbon dioxide (CO2) Other trace gases: methane, nitrous oxide, ozone, and chlorofluorocarbons Current controversy is not whether global temperatures are increasing, but in the extent of human impact The climate is changing, we cannot deny that The last time this happen human population was not as large, even small changes in climate can effect agricultural crops, larger storms hitting populated areas, etc. Is it significantly above natural background change? Can we afford to keep our heads in the sand? Consequences of global warming are not certain, but can be predicted… When scientists say “uncertain” it DOES NOT mean that they do not know what they are talking about It does not mean that there will not be consequences It is just difficult to predict the extent of those consequences, the timing of those consequences, etc. ○ This is the first time we are experiencing these changes with today’s society ○ The Earth and it’s systems are dynamic – constantly changing - But when we talk about these changes, we are talking about thousands, millions of years - Our society, population boom, building of extensive cites along coastlines, etc has been very recent - So, let’s say for a moment that man isn’t making it worse by putting more carbon dioxide into the atmosphere – changes are still happening……and we have to be prepared to deal with them…. Rising sea level Melting glaciers and ice sheets Thermal expansion of ocean water 1-meter sea level rise http://resumbrae.com/archive/warming/americaMap.jpg&imgrefurl 3-meter sea level rise Consequences of Climate Change Sea level rise Contamination of freshwater sources Vulnerability of more low-lying areas to storm surges Shift in species distribution Shifts in climate patterns will affect all living organisms Melting ice caps & expanding deserts threaten wildlife Extreme weather patterns Heat waves, extreme winters, larger storms in populated areas Droughts will affect productivity and crops Changing ocean chemistry Ocean water will become more acidic, warmer Changes in ocean circulation Spread of tropical diseases http://iceglaces.ec.gc.ca/content_contenu/images/bearours3.jpg http://www.ldeo.columbia.edu/edu/dees/ees/ arctic/images/05.jpg Possible Impacts of Climate Change on South Florida Possible sea level rise of 15-20 inches by 2060 ○ South Florida Water Management plays a delicate balancing game to ensure that areas in South Florida don’t flood during rain events (canal system), higher sea level would make that more difficult – areas would be more vulnerable to flooding ○ Greater vulnerability to storm surges and erosion ○ Salt water intrusion – fresh water supply for the population could be threatened Reducing greenhouse gases Greater fuel efficiency Alternative fuels Re-forestation Eliminate chlorofluorocarbons Reduce CO2 emissions Intergovernmental Panel on Climate Change 1988 Kyoto Protocol 1997 Ocean’s role in reducing CO2 Oceans absorbs CO2 from atmosphere CO2 incorporated in organisms and carbonate shells (tests) Stored as biogenous calcareous sediments and fossil fuels Ocean is repository or sink for CO2 Increases ocean acidity enough to affect organisms (corals) http://www.whoi.edu/science/MCG/cafethorium/website/images/tzex_img1.jpg Ocean’s role in reducing CO2 Add iron to tropical oceans to “fertilize” oceans May increase biologic productivity that will increase uptake of CO2 in oceanic life Plankton will die and fall to bottom, sequestering CO2 in sediment May not affect global CO2 levels significantly, may not work May cause unknown problems in ocean ecology for future http://www.whoi.edu/science/MCG/cafethorium/website/images/ocean_iron.jpg Ocean Literacy Principles 1c - Throughout the ocean there is one interconnected circulation system powered by wind, tides, the force of the Earth’s rotation (Coriolis effect), the Sun, and water density differences. The shape of ocean basins and adjacent land masses influence the path of circulation. 1d - Sea level is the average height of the ocean relative to the land, taking into account the differences caused by tides. Sea level changes as plate tectonics cause the volume of ocean basins and the height of the land to change. It changes as ice caps on land melt or grow. It also changes as sea water expands and contracts when ocean water warms and cools. 3a - The ocean controls weather and climate by dominating the Earth’s energy, water and carbon systems. 3b - The ocean absorbs much of the solar radiation reaching Earth. The ocean loses heat by evaporation. This heat loss drives atmospheric circulation when, after it is released into the atmosphere as water vapor, it condenses and forms rain. Condensation of water evaporated from warm seas provides the energy for hurricanes and cyclones. 3c - The El Niño Southern Oscillation causes important changes in global weather patterns because it changes the way heat is released to the atmosphere in the Pacific. 3d - Most rain that falls on land originally evaporated from the tropical ocean. 3f - The ocean has had, and will continue to have, a significant influence on climate change by absorbing, storing, and moving heat, carbon and water. 3g - Changes in the ocean’s circulation have produced large, abrupt changes in climate during the last 50,000 years. Sunshine State Standards SC.6.E.7.1 Differentiate among radiation, conduction, and convection, the three mechanisms by which heat is transferred through Earth's system. SC.6.E.7.2 Investigate and apply how the cycling of water between the atmosphere and hydrosphere has an effect on weather patterns and climate. SC.6.E.7.3 Describe how global patterns such as the jet stream and ocean currents influence local weather in measurable terms such as temperature, air pressure, wind direction and speed, and humidity and precipitation. SC.6.E.7.5 Explain how energy provided by the sun influences global patterns of atmospheric movement and the temperature differences between air, water, and land. SC.6.E.7.6 Differentiate between weather and climate. SC.912.E.7.4 Summarize the conditions that contribute to the climate of a geographic area, including the relationships to lakes and oceans. SC.912.E.7.7 Identify, analyze, and relate the internal (Earth system) and external (astronomical) conditions that contribute to global climate change. SC.912.E.7.9 Cite evidence that the ocean has had a significant influence on climate change by absorbing, storing, and moving heat, carbon, and water. SC.912.P.10.4 Describe heat as the energy transferred by convection, conduction, and radiation, and explain the connection of heat to change in temperature or states of matter.