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Oren Gaylord III
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This 14 page Class Notes was uploaded by Oren Gaylord III on Monday October 5, 2015. The Class Notes belongs to HON321M at Central Michigan University taught by Staff in Fall. Since its upload, it has received 12 views. For similar materials see /class/218929/hon321m-central-michigan-university in Honors at Central Michigan University.
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Date Created: 10/05/15
Humans and the global water supply 112608 Before we study how humans use water we need to understand the global water cycle How do cycles work Reservoirs Fluxes Sources Sinks How do cycles work Reservoir 1 Source Reservoir 2 Sink Reservoir 4 Reservoir 3 balanced How does any cycle work Accounting where are things or the distribution of the element in different reservoirs within a system Cycling where are things going and how fast they are moving from different reservoirs in the system Controls how does the system function and what factors drive the cycling Water cycle reservoirs Reservoirs Amount x 1000000 km3 Rocks not usable Oceans Ice Groundwater LakesRivers Atmosphere 25000 1350 275 82 0025 0031 Usable water Riversor anismsair Groundwater Oceans 914 GlaCIers 112608 Pathways for water cycling Precipitation Evapotranspiration Vapor transfer from ocean to land Return flow in rivers and ground waters from land to oceans Pathways for water cycling CLOUDS 9 WATER upon 39 O Wagons 393 3 umosuow ug coucausmou v mm iumumuma P U or W V abb l t g quot 39i 3 P 39 Us v BOUNDARY LAYER AND EXCHANGE WITH FREE ATMOSPHERE ge nrto A a n lrf v39 39 quotA b 39 f A 2 39 A 7 rquot39 RIVER DISCHARGE Controls on the water cycle Human consumption Temperature Land use changes Human consumption Increased dramatically since the industrial revolution Water is a critically lacking resource in certain areas such as deserts and semideserts It is very likely that water shortages due to human consumption will occur at the regional scale in the near future remember first part of the class Temperature Temperature affects Evapotranspiration Evaporation from oceans Melting of ice Sea level 112608 Land use Changes in land use result in changes in the Evapotranspiration Land runoff Now that we know how the water cycle works let s ta k about how do humans use water how much of the global water supply is appropriated by humans History of water use by humans 2000 yrs ago huntergatherers continually return to fertile river valleys 7000 yrs Ago water shortages spur humans to invent irrigation 1100 yrs ago collapse of Mayan civilization due to drought Mid 180039s fecal contamination of surface water causes severe health problems typhoid cholera History of water use by humans 1858 quotYear ofthe Great Stinkquot in London due to sewage and wastes in Thames Late 1800searly 1900 Dams became popular as a water management tool 1900s The green revolutionquot agriculture dependent on irrigation After World War II industrial development and water pollution 1972 Clean Water Act passed humans recognize need to protect water How do humans use water Consumptive use water is not returned to the stream after use Nonconsumptive use water is returned to the streams after use Consumptive use Water that is lost to the atmosphere because of evaporation from reservoirs and from plant transpiration Most consumptive water use is irrigation Consumptive use reduces surface runoff An example is the Colorado River Most of its water diverted to irrigated agriculture Unless year is very wet water does not reach the rivers mouth Consumptive use Domestic Commercial 12 Industrial Mining 8 IrrigationLivestock Thermoelectric 39 Consumptive use Agriculture is responsible for 87 of the total water used globally By continents Asia 86 of total annual water withdrawal North and Central America 49 Europe 38 By crops Rice heavy consumer of water it takes 5000 liters of water to produce 1 kg of rice Wheat for example consumes 4000 m3ha while rice consumes 7650 m3ha Consumptive use Next after irrigation is power production Constructing a dam leads to the conversion of a reservoir where there used to be a lake water evaporates more from a reservoir Many power plants are cooled by water evaporation Evaporation from dams Table 1 Water Evaporation of Reservoirs Compared with FreeRunning River Reservoir River Dam Evaporation Surface Area Evaporation Surface Area Evaporation Percentage l allyear Acres Galyear Difference l Hoover 80 164000 36E11 4000 87E09 24 l Glen Canyon 76 169700 35E11 6764 14E10 40 l Totals 71 E11 23E1D Average 32 20 18 16 14 12 Percentage of All Power Plants 3 3 Water drawn from power plants 02 225 2550 50100 1007250 250500 500750 750 1000 gt1000 Million Gallons per Day MGD Nonconsumptive use Water is used and then returned to the rivers streams Examples Power plants Industry Agriculture the water that does not evaporate will eventually make its way to the river Domestic Nonconsumptive use will often return water pollutedunusable 112608 Is there enough water in the world About 13 ofthe world39s population is experiencing water stress In Asia per capita availability declined by 4060 between 1955 and 1990 Projections suggest that most Asian countries will have severe water problems by the year 2025 Most ofAfrica historically has been waterpoor How much of the water are we already appropriating We can look separately at Evapotranspiration Surface runoff Eva potranspiration We can start with our estimate from last week of the total NPP that the humans have appropriated We can then factor in irrigation estimates for lawnpark irrigation and we come up wi At least 30 of all the water available for evapotranspiration on earth is appropriated by humans Natural ecosystems have to make do with the remaining 70 Surface runoff Distribution of global runoff is highly uneven and does not correspond to the distribution of the worid population Asia has 69 of world population but 36 of global runoff South America has 5 of world population 25 of runoff Amazon has 15 ofworld water supply but it is used by 04 of world s popula ion Surface runoff We factor in Agriculture Industrial use E z a 2 a n39 z u m a omest c Reservoir loss to evaporation Water cleanup diluting pollutedtreated water And it turns out that we are using more than 60 ofthe surface runoff Problem there is a lot of runoffthat is not accessible for example in Amazon We are heading towards some major problems Water about the future Estimates pt our appropriation at a total of 70 of freshwater by 2025 What do we do about it e lmproyements ln theefflclency of wateruse Example lsrael d person per year 7 modern technology and hlghly efflclerlt 7 Water l5 often wasted because it l5 underpnced Water l5 commonly subsldlzed especlally for agrlcultural use in both deyeloped and developan countnes suc subsidies and lettlrlg water pnces nse can provlde lncentlyes for conser lrlvestrnerlts needed to spread LO more efflclerlt technologles Why is Earth so comfortable 91208 What does it mean to be comfortable Greenhouse versus icehouse During most of its history as far as we can tell the Earth has had a temperature close to 15 C Why could Earth be uncomfortable Distance from Sun Strength of Sun What is temperature Temperature is a measure of the speed with which the molecules of a body move Fahrenheit Kelvm Celsius 2931 quot 5773 quot Sun39s surface temperature 19 Boilingpointol water What determines Earth s temperature Energy that comes from the Sun An body that has a temperature gt 0K emits some sort of ra iative energy lfwe plot the amount of energy emitted as a function of its wavelength it will be bell shaped The higher the temperature the more the body emits into the shorter more energy wavelengths see graph When energy from a star hits a planet it warms it up But since the temp of the planet rises the planet itself emits radiative energy into space When the two incoming and outgoing are equal the planet s temperature stays constant If Earth wasjust a rock what would its temperature be There are some simple rules about how energy from the Sun travels to Earth this is not the focus of this class though As it turns out if Earth was simply a giant ball of rock without an atmosphere it should be on the average at about 15 C ie it should be completely frozen 91208 Are there any other planets in the solar 7 What IS Earth s actual temperature System like Earth As mentioned above the average Well except for Mercury almost all other temperature on Earth is about 15 C but planets in the Solar system have higher also temperature than they should have Natural Greenhouse Effect It has been like that for quite some time i l l l Vquot A 600 ObseNed I a 500 Raldialtize Equilibrium It varies relatively little from day to day tural Greenhouse Effect season to season year to year F Why do planets have higher than The emission spectra of the Sun and predicted temperatures Earth Black Body Emission Curves of the Sun and Earth Because most planets have an atmosphere The gases in the atmosphere trap some of w the heat and as a result the temperature of the planet goes up see slides that follow Sun scaled by a lactnr ml 10 Radiative Flux in Wm2 pm 0 01 02 03 04 05 GB 4 5 678 390 20 30 405060 30100 2 3 Wavelength 3 in um The adsorption spectra of greenhouse Exactly how does the greenhouse effect gases work A BLACK BODY CURVES SUN II l lllllll I l KllTlllI ll lllllll 0l 015 02 03 05 I I5 2 3 5 l0 l520 3O 50 In B WAVELENGTH p 2100 r m l FL 7 23 I I l fill f w 1 m N r in lJI3 nil IHZIO Lilliui c n zlzln z L032 H20rnlatlnn H29 Ell I H4 H20 HDI EH4 91208 The faint young sun paradox For the last 45 billion years the Sun s output has increased by 2030 That means that during the first 3 billion years of its existence Earth should have been completely frozen yet evidence in the rocks indicates that there was always liquid water The explanation is that something kept the Earth warmer than it should have been That gives us a second problem as the Sun s energy output went up the Earth should have then gotten much ho er than it is ow The explanation to that is that whatever was keeping Earth warm in the beginning stopped working as the Sun s energy output increased It seems that Earth has a thermostat There must be some sort ofa feedback control that works like a thermostat Well then where is the thermostat and who sets it There are a variety of hypotheses on what could have been the thermostat and how it adjusted itself The most reasonable explanation is that the concentration of greenhouse gases in the atmosphere somehow changed in order to work as a thermostat Could CO2 be involved CO2 is by farthe best candidate The reason for that there are mechanisms on Earth that can add and remove CO2 from the atmosphere and some ofthose mechanisms seem to be affected by climate Where is Earth s carbon Most of Earth s carbon is in its rocks Some is found as coal oil and natural gas Very little resides in the atmosphere however Carbon can move between those reservoirs Where is Earth s carbon Vegetation em Amosphere 500 pwindusuial iSails 1560 7 Deep ocean 33000 Sediments and rocks 55000000 A Major carbon reservoirs gigatons 91208 The carbon cycles between different component of the planet Atmosphere Ocean uni ed layer 7 l 39 Deep ocean Sediments and rocks 1quot 02 B Carbon exchange rates gigatonsyear What kinds of processes could alter the amount of CO2 in the different reservoirs Volcanoes can input CO2 into the atmosphere Chemical weathering removes CO2 from the atmosphere What controls volcanic activity and could volcanoes be Earth s thermostat Volcanic activity is driven by heat sources deep into the Earth crust Those heat sources cannot actually be modified by climate What is chemical weathering C02 333 f Silicate rock CaSiOs CaSio3 H2C03 Ca2 5 HCO Ions dissolved Sio2 Caco3 Silicate Carbonic acid Shells 0F bedrock in soils ocean plankton In river water Weathering Transport Deposition on land in rivers in ocean Can climate affect the rate of chemical weathering Yes because Temperature Precipitation Vegetation Can chemical weathering act as Earth s Warmer Colder 39V 39quot e a dim Initial Reduwoquot 0f Initial Reduction of Change initial warming change initial cooling Increased Decreased temperature temperature precipitation precipitation vegetation vegetation Increased Decreased CO2 removal CO2 removal by weathering by weathering Increased Decreased chemical chemical weathering weathering A B 91208 The adsorption spectra of greenhouse Could water vapor be Earth s thermostat gases A BLACKBODY waves No because water acts as a posmve feed back SUN EARTH I 1 I Illllll I l l lllllll l I I lllllll 101502 03 05 I 152 3 5 10152030 50 100 WAVELENGTH 11 Jilile L TF1 yquot 03 D AJU I i3 I I I I l l H a rotation cultqu saunas 2 N20 N 502 I Cl CH4 HUI EH4 W O nuances oooooo Ill ASSURP TION 3 II l I Wait H20 Could life control Earth s climate The Gaia hypothesis Proposed by James Lovelock and Lynn Margulis Well does life react to changes in climate Can living things alter climate Life is the ultimate control of climate on Earth Moderate Gaia versus extreme Gaia What are the arguments Has the thermostat always worked Is the thermostat working now Nowadays we have ice sheets in the poles and tropical forest near the equator There is evidence that 750550 Myr ago Earth might have come very close to a complete freeze m parts per million w m Even if we account for lower solar output 6 lower than today the amount of 002 in the atmosphere would have had to be almost nothing for that to have happened 3 M O Fm I This suggests the thermostat temporarily failed 280 I loO 97O lQSL I900 2300 Too The effect of Earth s orbit on climate Nordl Pole 235 Sour Pole 91208 What does Earth s orbit look like today Earth is like a giant tilted top rotating around the Sun Revolution Rotation Precession Circular mum rev I o 140 Wobbling motion precession Angle oftilr l Spinning motion rotation 9 Tilt Earth rotates around an axis that passes through its poles Earth s rotation axis is tilted with respect to the plane of its revolution around the Sun The angle and direction of the tilt are constant during the course of a yearly revolution Tilt North Pole South Pole Tilt seasons solstices and equinoxes Because it is tilted Earth has seasons Different latitudes experience different seasonality Not much seasonality in tropics Moderate seasonality in temperate regions like Ml Extreme seasonality at the poles Seasonality is described with certain milestones of the orbit around the Sun Equinoxes day night March 20 September 22 Solstices shortest day Dec 21 in NH and June 21 in SH longest day Jun 21 in NH and Dec 21 in SH Eccentricity Earth s orbit around the Sun is not a perfect circle Earth rotates on a slightly eccentric or elliptical orbit Because its orbit is not a perfect circle Earth s distance to the Sun changes throughout the year Eccentricity Equinox March 20 F I l I Empty I Perihelion 5 391 153 million km gt Solstice June 21 July 4 January 3 W 158 million km Sun at Solsnce I one facus December 21 September 22 91208 Changes in tilt over time Discovered by French astronomer Leverrier The tilt varies from as low as 222 to as high as 245quot Currently it is 235 and it is decreasing Changes in tilt over time WQ The change in the tilt is on 0539 23 a very regular cycle both in 39 One frequency and strength We Myr ago Changes in tilt over time Does it matter ifthe tilt changes a little B 90quot tilt Changes in tilt over time Smaller angles tend to reduce seasonality Larger angles tend to increase seasonality The effect of the tilt is strongest at the poles Changes in Earth s orbit over time Two kinds of changes Change in eccentricity Precession Changes in eccentricity over time 1 a2 39 b2 2 EccentrICIty E 6 91208 Changes in eccentricity over time Eccentricity varies from almost circular 0005 to not quite so circular 00607 Currently we are close to circular 00167 The variation is in two cycles 100000 years 413000 years Wobble Axial precession 00 I ears North Polarls 1Q l Spin axis N today Precession of Earth s spin axis wobble Precession of the ellipse vemartian x 9 9 Precession of the equinoxes The combined effect of the wobble and the precession of the ellipse is that the exact timing of equinoxes along the orbit moves through the years Why does precession matter Because of the eccentricity in Earth s orbit the preces5ion means the amount of solar insolation in a given season changes Currently we are closest to the Sun perihelion around the winter solstice and farthest from the sun aphelion around the time of the summer solstice About 11000 years ago or 11000 years from now it will be the other way around Why does precession matter June N solstice Minimum distance p aphelion y perihelion V Dace ber solstice 91208 How do Earth s orbital patterns affect climate Tilt causes seasons Changes in tilt leads to changes in how pronounced seasons are Precessions changes the distance ofthe Earth to the Sun relative to the equinoxessolstices so it also affects how pronounced seasons will be Ul imately the combined effect oftilt and precession can result in major changes In the climate Those changes are of cyclical nature
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