GEOL 1060 Global Change: An Earth Science PerspectiveFall 2013, 2nd Hour Exam: Vocabulary and ConceptsUnit IV. Circulation of the Liquid EarthConvergence: surface water tends to pile up at the center of gyres, where downwelling occurs. If HOT, salinity increases as surface water evaporatesDivergence: 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 surfaceCoriolis 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. SHSalinity: how much salt is in the waterTemperature: temperature of the waterDensity: for sea water density of controlled by temperature and salinityMixed layerDeepwater or Bottom WaterSurface 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 circulationPrimary Productivity: conversion of CO2 into organic matter by organisms through photosynthesis/chemosynthesis. Sunlight and nutrients control primary productivity or Net Primary ProductivityNutrients: a substance that provides nourishment for essential growthMonsoons – COME BACK• Monsoons summer wet/ winter dryStrongest where:large land mass adjacent to oceanhigh elevations close to the seawarm oceans, high evaporation deep convection releases latent heat Monsoons: seasonal reversal in surface windsSummer heating of Tibetan Plateau causes high surface temperatures, low atmospheric pressure, and intense convection of air above the surfaceWinter it reverses: High elevations and persistent snow cover enhance the continentally, producing even lower temperaturesMonsoons: (drivers) Variability on historical and longer time scalesRole of primary insolation, and how the positive feedbacks from latent heat release, ocean temperature and vegetation increase monsoon vigorUnit V. Global Warming: The EvidenceDirect evidence: the instrumental temperature record: Total amount, identifying the first and second-order trendsSources of uncertainty; “Heat island” effect, oceans vs land, geographic variability inthermometer 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 warmingClimate proxies: what are they?Glaciers? Small glaciers and ice caps… Greenland and AntarcticaIce shelvesSea level rise: how much? Tide gauges and satellites Why is sea level rising… two reasonsSea Ice, evidence for melting? Two large positive feedbacks from sea ice; one insummer 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 ornegative feedbacks?Permafrost Take Homes• Arctic warming has resulted in permafrost thawing• On land, carbon rom plants preserved in permafrost is then released as either CO2or 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? Whatdo they tell us about 20th Century warming? The Swiss Iceman, Alaskan snowbanksKey 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 itsstructure?Unit VI. Global Warming: The ExplanationA. 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 CO2What controls the changes of CO2 we observe in the troposphere? Why are the samplingspots 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 atmosphere2nd-order trends: The Biosphere breathing: regular annual wiggles in the level of CO2 in the atmosphereWhat are the roles of the following in the global carbon cycle?Primary productionPhotosynthesisRespirationDecompositionBe 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 fuelburning?The global carbon cycle: What is this and what can we learn from it?Other Greenhouse gases: CH4 (residence time, two primary sources), NOx, CFCsChanges in GHG over timeInstrumental recordHow can we reconstruct changes before direct measurements of theatmosphere? How do we calibrate?Last 1000 years:Last 800,000 yearsCan 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 severalreasons, including:Sun has been getting hotter throughout Earth HistoryPrecession of the equinoxes and tilt of our spin axisSolar irradiance measurements, sunspots, and sunspot cycles (30 yr of measurements and100 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 rolefor the Sun in explaining 20th Century warming?C. Volcanism: to be significant we need the right stuff and have it injected into the stratosphereExplosive: 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 weeksAsh: ParticulateVolcanic aerosols/sulfuric acid aerosols: origin, effect, and duration of effect.Perturbation vs ForcingPinatubo: 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 rolefor volcanoes in explaining recent climate change?D. Other factorsAerosols: tiny airborne particles of matter, either liquid droplets or solids, that are so small that
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