Water - Its Properties and Role in the EnvironmentOutline:• Role in early history and science• Unique chemistry• Hydrologic cycle - redistribution, climate effects• Ocean circulation - basic wind & thermohalineChemically uniqueExists in all three phases at atmospheric temperatures & pressures(high melting and boiling points compared to molecules of similarsize It is the only substance that does this!• High heat capacity (4.2 J/g/K). It stores a lot of heat energy whichmakes it a good medium for spreading the planet’s heat• High heat of fusion (solid to liquid ~ 335 J/g/K) and vaporization(liquid to gas ~ 2400 J/g/K) so more effectively transfers heat whenchanging phase in atmosphere/oceanChemically and Physically unique•Water is physicallyunique because it is lessdense as a solid (ice) thanas a liquid.•The maximum density ofliquid water occurs at 4ºCPhysically Unique• High surface tension so it forms drops & helps make good cellmembranes• Dissolve other compounds very easily and so can transportchemicals (e.g., NaCl, nutrients)• Mediates or facilitates most chemical reactions in living systems(e.g., takes water to photosynthesize) - neutral pHChemically andBiologicallyUniqueCovalent and Ionic BondsHydrogen Bonds - 10 x stronger than normalintermolecular (van der Waals)forces.100%326,000,000Total watervolume0.0001%300Rivers0.001%3,100Atmosphere0.005%16,000Soil moisture0.008%25,000Inland seas0.009%30,000Fresh-water lakes0.61%2,000,000Ground water2.14%7,000,000Icecaps, Glaciers97.24%317,000,000OceansPercent oftotalwaterWater volume, incubic milesWater sourceDistribution of waterHydrologic Cycle (in 103km3)Quantitative Hydrological Cycleseveral hoursBiological water8 daysAtmospheric moisture16 daysChannel network1 yearsSoil moisture5 yearsBogs17 yearsLakes10000 yearsGround ice of the permafrost zone1600 yearsMountain glaciers9700 yearsPolar ice1400 yearsGround water2500 yearsWorld OceanPeriod of renewalWater of Hydrospherehttp://www.unesco.org/science/waterday2000/Cycle.htmPeriod of RenewalAquifersFreshwater Resources1407000Flux(cubic miles / year)1400 yrs16 daysResidence Time200000300Volume(cubic miles)GroundwaterRiversAtmospheric circulationEquatorial Hadley Cellshttp://psb.usu.edu/psbdept/faculty/lh/bmet2000/Image56.gifTo see the animated version go tohttp://geography.uoregon.edu/envchange/clim_animations/gifs/prate_web.gifPrecipitationRain shadowGlobal warmingGlobal warming(temperature increase)(temperature increase)Effects of global warming on water cycleEffects of global warming on water cycleSpeeds up globalSpeeds up globalwater cyclewater cycleMore extreme weather eventsMore extreme weather events••DroughtsDroughts••StormsStorms••FloodsFloodsProjected Changes in Annual Precipitation for the 2050sProjected Changes in Annual Precipitation for the 2050sSource: The Met Office. Hadley Center for Climate Prediction and ResearchThe projected change is compared to the present day with a ~1% increase per year in equivalent COThe projected change is compared to the present day with a ~1% increase per year in equivalent CO22GreenGreen••= increasing, Brown= increasing, Brown••= decreasing= decreasingGlobal Precipitation TrendsGlobal Precipitation Trends(% per decade) (% per decade) 1900 - 19941900 - 1994Source: Watson 2001U.S. Precipitation Trends: 1901 to 1998U.S. Precipitation Trends: 1901 to 1998Source: National Climatic Data Center/NESDIS/NOAAGreenGreen••= increasing, Brown= increasing, Brown••= decreasing= decreasingAll stations/trends displayed regardless of statistical significanceAll stations/trends displayed regardless of statistical significanceExtreme Precipitation Events in the U.S.Extreme Precipitation Events in the U.S.Source: Karl, et.al.