GEOL 1060 Global Change An Earth Science Perspective Fall 2013 2nd Hour Exam Vocabulary and Concepts Unit IV Circulation of the Liquid Earth Convergence surface water tends to pile up at the center of gyres where downwelling occurs If HOT salinity increases as surface water evaporates Divergence where ocean currents separate upwelling occurs Upwelling The rising of cooler nutrient rich ocean water to the surface to replace warm divergent surface water Downwelling The sinking of surface water caused by convergence and water accumulation at surface Coriolis effect and resultant Ekman transport surface currents are deflected to right NH or left SH of prevailing wind Ekman Spiral transfer of Coriolis effect down through the water column Ekman transport Net effect surface water moves at right angles to the wind NH vs SH Salinity how much salt is in the water Temperature temperature of the water Density for sea water density of controlled by temperature and salinity Mixed layer Deepwater or Bottom Water Surface currents driven by winds through the frictional coupling between atmosphere and sea surface Deepwater formation forms in the northern north Atlantic very salty and cold and Antarctica not as salty but colder leaving it denser Thermohaline circulation Density driven vertical circulation Primary Productivity conversion of CO2 into organic matter by organisms through photosynthesis chemosynthesis Sunlight and nutrients control primary productivity or Net Primary Productivity Nutrients a substance that provides nourishment for essential growth Monsoons COME BACK Monsoons summer wet winter dry Strongest where large land mass adjacent to ocean high elevations close to the sea warm oceans high evaporation deep convection releases latent heat Monsoons seasonal reversal in surface winds Summer heating of Tibetan Plateau causes high surface temperatures low atmospheric pressure and intense convection of air above the surface Winter it reverses High elevations and persistent snow cover enhance the continentally producing even lower temperatures Monsoons drivers Variability on historical and longer time scales Role of primary insolation and how the positive feedbacks from latent heat release ocean temperature and vegetation increase monsoon vigor Unit V Global Warming The Evidence Direct evidence the instrumental temperature record Total amount identifying the first and second order trends Sources of uncertainty Heat island effect oceans vs land geographic variability in thermometer records Arctic warming compared to global warming does the planet warm equally in all areas Is there a link between precipitation and global warming Indirect evidence of 20th century warming Climate proxies what are they Glaciers Small glaciers and ice caps Greenland and Antarctica Ice shelves Sea level rise how much Tide gauges and satellites Why is sea level rising two reasons Sea Ice evidence for melting Two large positive feedbacks from sea ice one in summer and a different one in winter You will want to be able to explain these How much sea level change from sea ice melt Permafrost What is it is there much is it changing and are there positive or negative feedbacks Permafrost Take Homes Arctic warming has resulted in permafrost thawing On land carbon rom plants preserved in permafrost is then released as either CO2 or CH4 both GHG producing positive feedbacks on warming Vast amounts of methane clathrates frozen What is coming out from beneath melting snowbanks ice caps and glaciers What do they tell us about 20th Century warming The Swiss Iceman Alaskan snowbanks Key questions from Unit V Is the planet warming How do we know How confident are we If it is warming where has it been warming how long has it been warming and what is its structure Unit VI Global Warming The Explanation A Greenhouse gases GHG are gases that are transparent to SW Solar radiation and absorb LW Earth radiation CO2 is a GHG The instrumental record of atmospheric CO2 What controls the changes of CO2 we observe in the troposphere Why are the sampling spots where they are and what do we learn from records in such different places around the planet 1st order trends Regular increase in the level of CO2 in the atmosphere 2nd order trends The Biosphere breathing regular annual wiggles in the level of CO2 in the atmosphere What are the roles of the following in the global carbon cycle Primary production Photosynthesis Respiration Decomposition Be able to explain why the observed CO2 records from different points on Earth differ Why is CO2 increasing in the atmosphere Why is it not by the amount of fossil fuel burning The global carbon cycle What is this and what can we learn from it Other Greenhouse gases CH4 residence time two primary sources NOx CFCs Changes in GHG over time Instrumental record How can we reconstruct changes before direct measurements of the atmosphere How do we calibrate Last 1000 years Last 800 000 years Can changes in GHG fully explain the pattern of global warming of the past 100 years B Solar Constant Solar irradiance Solar energy reaching Earth may change for several reasons including Sun has been getting hotter throughout Earth History Precession of the equinoxes and tilt of our spin axis Solar irradiance measurements sunspots and sunspot cycles 30 yr of measurements and 100 yr of secure proxy record through changes in sunspots How do we know that suspots are a reliable proxy for solar irradiance How do sunspot records compare to the instrumental temperature record Is there a role for the Sun in explaining 20th Century warming C Volcanism to be significant we need the right stuff and have it injected into the stratosphere Explosive injects ash into the stratosphere where gravity removes ash in weeks to months no precipitation in stratosphere Fluid volcanism only releases stuff into the troposphere where precipitation gravity scrub it out within days to weeks Ash Particulate Volcanic aerosols sulfuric acid aerosols origin effect and duration of effect Perturbation vs Forcing Pinatubo What did we learn How do we recognize volcanic eruptions in prehistory How does volcanic loading compare to the instrumental temperature record Is there a role for volcanoes in explaining recent climate change D Other factors Aerosols tiny airborne particles of matter either liquid droplets or solids that are so small that they remain suspended in the atmosphere for a long time Soot aerosols are smaller than clay Sulfuric acid aerosols
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