Geography 3A Lecture Notes - University of California, Santa Barbara
Geography 3A Lecture Notes - University of California, Santa Barbara
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Chapter 6 Ocean Chemistry 2514 1047 PM Lecture 1 September 27 2013 Bring water bottle to section tomorrow Midterm on October 28 his birthday Chapter 6 7 and 8 Chemistry science of matter its composition structure properties and behavior Chemical oceanography involves physics biology and geology of the world ocean Interdisciplinary Figure 64 Classi cation of Matter Matter is solid material with mass physics mass and energy Mixtures different types of matter separable by physical means Substances elements and compound Elements atoms neutrons protons electrons eg H O Na Molecules two or more atoms united i e H20 where H is hydrogen atom O is oxygen atom inorganic and organic Compounds atoms chemically united like H2O and NaCl Motivation Chemistry affects life in ocean and vice versa i e biochemistry Chemistry is important for climate Physical properties affected by chemistry i e salinity Atmosphere is affected by ocean chemistry and vice versa Pollution is often chemical issue Santa Barbara Oil Spill British ship HMS Challenger 18721876 First oceanography expedition refit warship 200 ft long 2300 tons engine and sail Sailed during the Civil War before Industrial Revolution where CO2 came out Captain Cook made explorations of Alaska Route of the HMS Challenger 713 days at sea out of port 1606 days 69000 nt miles or about 79000 statute miles Went near Antarctica Challenger Facts C Wyville Thomson led expedition John Murray led analyses Captain George Nares and 200 crew onboard Took place just after US Civil War and during early polar exploration through early 190039s British Empire was near its peak Why Challenger Expedition Samplers and Labs Instrument and sampling platform Shallow water dredge Buchanan Water sampler Carbonic acid analysis apparatus Natural history laboratory Chemistry laboratory British ship HMS Challenger 18721876 Why so important quotthe greatest advance in the knowledge of our planet since the celebrated discoveries of the 15th and 16th centuriesquot John Murray in 1895 Provided data concerning composition and structure of the ocean Data are still useful Why Lecture 2 October 2 2013 Captain James Cook 17281779 Endeavour replica in Cooktown Queensland harbor anchored where the original Endeavour was beached for seven weeks in 1770s Challenger Advances 492 soundings with depth using lead lines 144 miles of sounding rope and 125 miles of piano wire 263 water hydrographic stations 133 otto dredges 151 open water trawls for organisms 4700 new species Measured currents Did excellent chemical analyses i e relevant to carbon etc Discovered Mid Atlantic Ridge and Mariana39s Trench Found life in deep sea disproved azoic dead zone No primordial slime on sea oor postulated by Ernest Haeckel Data stored in UK 50 volumes of reports still used What is in Seawater Composed of H20 and many dissolved elements and compounds Geometry of a water H20 molecule Covalent bonding sharing electrons between H and 0 atoms Important Properties of Water Molecules Water has high surface tension hard to pull molecules apart Capillary waves restoring force depends on polar property of H20 molecules and H bonding H20 is very good at dissolving materials Water exists as solid liquid and gas Water Is An Excellent Solvent Elements like Na with 11 electrons readily donates its quotextraquot outer shell electron while those like Cl with 17 electrons quotmissingquot an outer shell electron readily accepts an electron 0uter shell of electrons wants to be stable i e 2 electrons in 1st 8 electrons in 2nd and 3rd shells etc Periodic Table Na ion and Cl ion together make a stable molecule When together they form NaCl via ionic bonding How does Material Enter Oceans Volcanoes hot springs vents i e chloride Cl Weathering rock i e sodium Na Rivers Rain and atmospheric deposition Biological processes recycling really Meteors from space Age of Earth is estimated to be over 4 Billion years so long time for oceans materials to enter and distribute hence Dittmar39s Principle next Constituents of ocean salinity Note NaCl makes up 86 of dissolved elements Approximate Composition of Open 0cean Seawater Seawater by weight percent Water 965 or 965 ppt Dissolved material 35 or 35 ppt Total 100 or 1000 ppt Ppt parts per thousand like percent but using 1000 for reference base instead of 100 1 What percent by weight is water in the human body 5060 2 What percent of human body is Na Cl 015 015 Definition of Salinity Number of grams of dissolved material in 1 kilogram 1000 gm of seawater Units in parts per thousand ppt or practical salinity units psu or PSU Salinity Determination Given 70 gm of dissolved material i n2 kg or 2000 gm of seawater what is the salinity S 70 gm2000gm o 35 gm1000gm 35gm1000gm gm cancels out o 35 ppt or PSU Dittmar39s Principle In open ocean total amount of dissolved materials may change but ratios of the elements remain very nearly the same Thus we can calculate salinity from chlorinate using formula s 18 X Cl Example Given C1 20 ppt what is the salinity S 18 X Cl 18X20ppt36ppt Where does this method fail o Rivers estuaries bays near coasts Lecture 3 October 4 2013 Measurements of Salinity Devices Refractometer uses light refraction CTD conductivity temp depth Salinometer Satellite sensors using microwave energy Salinity affects waver conductivity Biologically Important Nutrients for Supporting Phytoplankton Phytoplankton drifting algae are fundamental to life on Earth Biologically important nutrients nitrogen nitrate nitrite silicate phosphate ammonia iron Eutrophic high in macronutrients Oligotrophic low in macronutrients Dittmar39s Principle does not work for rivers bays estuaries and nearshore ocean waters Dittmar39s Principleaka Law of Constant Proportions Why does S 18 X Cl For open ocean we might measure the total mass of our sample of dissolved matter to be 350 gm for our total seawater mass of 1 kg We also determine the mass of the Chlorine ions to be 192 gm Then the ratio of ClS 192 gm 350 gm 055 55 ClS 055 or C1 055 S And by rearranging S Cl 055 and S 18 X Cl Global Carbon Cycle Exchange rate in Gtons Cyr Gtons C stored in each reservoir Note Gtons 109 tons Lecture 4 October 7 2013 Atmospheric CO2 at Mauna Loa Observatory Keeling curved showing increase of atmospheric CO2 at Mauna Loa Observatory most important curve in science today Higher CO2 leads to lower pH Acid Threat If CO2 continues to rise unchecked computer models show that acidification will deplete carbonate ions in much of the ocean by 2100 turning the waters corrosive for many shell building animals Ocean acidification ongoing decrease in the pH of the Earth39s oceans caused by the uptake of anthropogenic carbon dioxide from the atmosphere Chapter 7 Ocean Physics 2514 1048 PM Lecture 4 October 7 2013 Physics study of matter forces motion waves momentum heat radiation and all forms of energy and their transformations exchanges and propagations Physical Oceanography involves chances of energy and matter between atmosphere and ocean and within the ocean Forms of Energy Important to Oceanographers The law of conservation of energy energy can be neither created nor destroyed but it can change forms Thus one form of energy may in principle be converted to another Radiant or solar energy energy in electromagnetic radiation that comes from the Sun important in heating of Earth the ocean and the atmosphere and essential to photosynthesis Example sunlight Kinetic energy energy of motion of moving objects 12 x mass x velocity 2 Example movement of wind across the ocean surface or collisions of water molecules in a glass Thermal energy or heat energy of random motion of molecules which results in the exchange of heat between objects Example ocean warming the overlying air or vice versa Chemical energy energy stored within the chemical bonds of substances Example chemical reactions that occur within the cells of marine organisms Potential energy energy related to the position of objects or the position of atoms in molecules Example a rock sitting on top of a ledge or the spacing between water molecules Temperature of the Ocean Conversions K C 273 F 18 C 32 C 056 F32 Freezing point 0 degrees C 32 degrees F Boiling point 100 degrees C 212 degrees F Room temperature 25 degrees C 77 degrees F Human body temperature 37 degrees C 986 degrees F Absolute zero 27315 degrees C 45958 degrees F where all motion stops CTDRosette for measuring temp salinity pressure and obtain water samples Expendable Bathytermograph XBT measures temperature as function of depth launched from a ship Observational and Modeling Issues Time space resolution and ranges Sufficient variables to represent processes Synoptic sampling is critical Heat and the Ocean Heat capacity heat needed to raise the entire mass or volume of an object or system Specific heat specific mass or volume Why is heat capacity important for the ocean Thermal inertia ywheel effect for heating and cooling water Stop a spinning bike wheel Temperature swings Concept of Heat Transfer Heat transfer occurs when two systems have different temperatures When two systems reach thermal equilibrium heat transfer stops Heated by conduction convection and radiation Convection transfers heat through movements of molecules Radiation transfers heat through radiation of electromagnetic energy which may travel through a vacuum Review of Properties of Seawater Density mass over volume What affects density of seawater Pressure p increase gives density increase p decrease gives density decrease Salinity S increase gives density increase S decrease gives density decrease Temperature T increase gives density decrease T decrease gives density increase What processes affect seawater density in the ocean Processes that increase density processes that decrease density Hydrostatic Pressure P p g h p density massvolume g acceleration of gravity h water depth Note 10 m of water depth is equivalent of 1 atmos Of pressure Concept of Buoyancy Positive oats negative sinks neutral stays same depth Archimede s Principle Buoyant force weight of uid displaced by object o If object is more dense than water it sinks less dense rises same density stays put Argo Floats use of buoyancy to collect CTD data Principle used for submarines profiling moorings gliders AUVs The electromagnetic energy spectrum including light Note 1 nanometer 1 nm 10 A 9 meters Wein s Law is represented as kmax 2890T Where T is in K with K C 273 Example Where is the hottest part of the volcano s lava Note kmax and T are inversely proportional Yellow has shorter wavelength than red And rearranging Wein s Law equation T 2890 A Blackbody Radiation Stefan Boltzmann E 0 TA4 Earth is cooler than Sun so wavelengths of Earth radiation IR are longer than those of Sun visible We call these Earth s emitted longwave and Sun s emitted shortwave radiation What Happens to Light That Enters the Ocean Wavelength is important light energy is critical for photosynthesis life incl phytoplankton and heating of the upper ocean Light is re ected scattered and absorbed Beer s Law light intensity decreases exponentially with depth in the ocean 0 Most of life in ocean exists down to depth where light is at least 1 of surface value euphotic zone 0 Phytoplankton are major absorbers and scatterers of light in the ocean Coccolithophorid Blooms these are important scatterers of light and produce DMS a major green gas As aerosols DMS provides seeds for clouds Chalk cliffs of Dover and elsewhere are massive deposits of coccoliths Radiation Fluxes in the Atmosphere and Ocean Greenhouse Gases carbon dioxide CO2 Methane CH4 Water vapor H20 Nitrous oxide N20 Dimethylsulfide DMS CH32S Halocarbons CFC Schloro uorocarbons Shortwave radiations makes it through green house glass while longwave radiation are trapped within the green house glass leading to heating Seasons What are seasons o a subdivision of the year marked by changes in weather ecology and hours of daylight Why do we care o Affects our atmosphere climate daily lives Why are there seasons Changes in the overhead position of the Sun causes variations in the amount of solar radiation incident on a unit area of the Earth s surface Thus on a seasonal basis the area of the Earth s surface heated most directly changes day to day What is the tilt of the Earth s axis of rotation o 235 Color Vision Do sea lions have color vision o They do but very limited see only blue green area of the spectrum o Likely an adaptation for living in marine coastal habitats Do dogs have color vision Dichromats and have color vision but limited can see blue and yellow but difficult to differentiate red and green They have two spectral types of cones photoreceptors while normal humans have three cones Use color instead of brightness to differentiate light or dark blueyellow Midnight Sun Effect The apparent solar path across the sky as viewed by observers at different latitudes Note height of the sun in the sky decreases as an observer moves towards the poles Seasonal changes in solar path are less than regional differences but their effects are pronounced Sun remains below the visible horizon for observers at the poles during winter months All of these patterns result solely from the orbit of a tilted Earth around the sun Chapter 8 Ocean Atmosphere 25141048 PM Definitions Fluids substances that flow air and seawater Weather for both the atmosphere and ocean Weather describes the physical conditions at a particular time and place Study meteorology Climate for both geophysical uids climate is the average Weather for specified time periods and geographic areas or locations Study climatology o Note We have both atmospheric and oceanic Weather and climate o Global climate change re ects evolution of Weather conditions over longer time scales Motivation Weather affects daily lives politics agriculture Extreme weather and climate change take lives and affect national and world economics Atmosphere drives ocean s currents Waves and thermodynamics heating and cooling Goal prediction of future oceanic and atmospheric conditions using data and models Meteorological Measurements Instrumentation Wind speed Wind direction Barometric pressure Solar SW radiation Longwave radiation Air temperature Relative humidity Rainfall Heat Momentum and Mass Fluxes Wind stress at sea surface causes exchange of momentum energy and mass Cause waves and currents as well as turbulent mixing Cooking at ocean surfaces causes convective mixing and vertical currents Ice and Its Effects Affects heat exchangebiology Produces fresh Water Production of brine as sea ice forms causes convection Ice has high albedo Ice melting on land leads to raised sea level Ice formation lowers sea level Critical factor for global climate change Albedo Re ected Radiation Incident Radiation Which of the objects in the picture have the highest albedo Surfer Girl iiki Lowest albedo Theodore Nansen If there were more Great Pyrs in the world what would happen to Earth s albedo Increase Could they reduce global warming Doubt it Climate warming decreases ice which decreases albedo and albedo and leads to even more warming positive feedback Climate cooling causes more ice which causes greater albedo which causes even more cooling positive feedback Coriolis Effect occurs because Earth is spherical and rotates Angular momentum is conserved Need a component of velocity toward or away from axis of rotation Note the different speeds of a person standing still at the North Pole at 40 N and one at the equator As a cloud moves northward in the NH it moves the location which has slower tangential velocity than where it came from resulting in a deflection rightward from its path Try for southward cloud movement Satellite launches at equator Why o Southward goes faster till you pass the equator Coriolis Effect Accounts for rotation of Earth when we study motions of the Atmosphere and the Ocean from Earth reference frame From our fixed frame of reference moving objects such as winds and currents de ect to thright of their trajectories in the NH and to the left of their trajectories in the SH Increases with latitude For horizontal motion is zero at the equator Proportional to the velocity of the parcel of seawater or air faster moving objects experience greater e ections due to Coriolis Effect Most important for large scale motions that is over scale greater than tens of kilometers tens of milse such as the circulation of the ocean and atmosphere Newton s 2 Law F ma applies for inertial reference frame Need to account for rotational effects on Earth Baseball train problem General Circulation of the Atmosphere Horizontal Pressure Gradients A key to understanding atmospheric and oceanic motions in the forms of winds and currents What would atmospheric circulation look like if the Earth stopped rotating and the Earth were only water covered Halley s Theory would work Ferrel s 3 cell model of atmosphere circulation Models and theories simplify and conceptualize but they are not perfect Why are there 3 cells of meridional circulation in each hemisphere How many cells for faster a rotating planet assume same heating For a slower rotating or non rotating planet Note waves in these flow fields Flow patterns of a uid in a rotating annulus when the inner and outer cylinders are at different temperatures Lines correspond to isotherms at mid depth Transition from laminar to turbulent flow in this sequence of figures starting at the top left is a consequence of an increase in the rate of rotation from one figure to the next Figure 8 19 Rossby waves encircle the whole Earth and are important for the weather patterns we observe especially in the NH mid latitudes which are highly in uenced by these waves Waves can allow very cold dry air masses to move south and warm moist air masses to move north Rossby waves are planetary waves as they have very long wavelengths and wrap around the Earth in the atmosphere also waves in the ocean which propagate west Rossby waves result from variation In the Coriolis effect with latitude and conservation of angular momentum Jet Stream Jet Stream brings cold air to the central US warm air to the eastern seaboard effecting a poleward transport of heat Northern Hemisphere Polar Stream can reach 100200 knots in core Located about 10 km Actual weather patterns are more complicated than simple theories depict Why Mountains Continent ocean ice contrasts NH more land SH more ocean Seasonality What causes temperature distributions map color images Warmest equatorial regions low latitudes Less radiation more radiation Radiation exposure is much greater in lower latitudes than higher latitudes Seasonal contrasts Salinity the amount of dissolved minerals in a gram of water What affects sea surface salinity SSS Rainprecipitation decrease salinity because diluting salt water with fresh water Evaporation causes salinity increases as H20 leaves sfc and salts remain behind If P gt E decrease SSS If P lt E increase SSS If P E no change in SSS P E and SSS distributions as function of latitude How are they related o Inversely related Why are there seasonal differences Distributions of temperature and salinity across the Atlantic Ocean Cooler water is heavier Average depth of the ocean is 4000 meters Where is the thermocline and pycnocline o Thermocline between warmer and cooler water line o Pycnocline density change o Change in temperature leads to change in density What affects deep distributions Hurricanes Typohoons Cyclones WillyWilly s Hurricane for Atlantic Can we infer Hadley cell from this map of rising or sinking air YES Lots of rising air and convection close to the equator inner tropical convergence zone air is converging moving towards the equator and rising Heated air rises up ows with circulation pattern Where do tropical storms hurricanes and typhoons generally form Near equator where air convects strongly What is the ITCZ intertropical convergence zone air is converging moving towards the equator and rising Why more cyclones in the northern hemisphere Bias towards northern hemisphere because there is more land mass Typhoon Phailin Strikes India October 2013 160 mph winds Cat 5 1 million evacuated from low areas death toll so far is 43 Cyclone Odisha made landfall in the same region in 1999 and killed 10000 people At the peak of Phailin s power Recipe for a Hurricane a Whirling Heat Engine 1 Heat 200 ft of ocean water about 80F required for enough water to evaporate 2 Converge winds near surface and with cyclonic counterclockwise rotation 3 Make air unstable allow to rise 4 Humidify about 18000 ft of air as you pull it into storm Extra water vapor supplies more latent heat energy 5 Avoid ripping storm apart maintain pre eXisting winds those not created by storm at same direction and speed at all altitudes 6 Pump away air rising in the storm with a high pressure area in the upper atmosphere a Note These ingredients are rare fewer than 10 of tropical weather disturbances become tropical storms Keep trying How Powerful is a Hurricane A severe storm may have a total power to 10quot15 Equivalent to exploding 500000 atomic bombs per day Named by both men and women names in alphabetical order Hurricanes Continued Category 15 depending on wind speeds interior pressure and damage Hurricane Fabian Hit Bermuda as Category 3 hurricane on September 52003 Worst hurricane to strike Bermuda since 1926 winds 100 kts 50 ms 8 people died 300 million damage to Bermuda Hurrican Sandy Perfect Storm Also known as Super StormFrankenstorm Oct 2012 Sandy moved few mph northward as Cat 2 hurricane Merging of an extra tropical low over NYC with Hurricane Sandy Fujiwhara Effect 192123 Cat 1Definition Problem Lowest bar Press Of 930 mb Largest in diameter in history 1100 mi No model had attempted to predict such a phenomenon but it had occurred in 1954 1972 and 1989 Bad or biased news reporting 13 foot storm surge 45 million people were affected loss of power to 10 million peoplestill out some places FEMA issues government promises like during Katrina unkept 66 billion in damage initial est 1B only Katrina more at 108 billion affected 24 states plus Caribbean Islands 253 people killed in 11 countries iatrina had over 1835 deaths Hurricanes Continued Are hurricanes and typhoons becoming more frequent and more intense because of global warming Argument severe loss of summertime Arctic sea ice attributed to greenhouse warming appears to enhance NH jet stream meandering intensity Arctic air mass invasions toward middle latitudes and increase the frequency of atmospheric blocking events like the one that steered Hurricane Sandy west into the densely populated NYC World Ocean Circulation 2514 1048 PM Transport of nutrients organisms pollutants fisheries and sediment Affect weather Climate transport of heat Search and rescue Track pollution trajectories Energy from currents Navigation and shipping routes Matthew Maury Matthew Maury 18061843 Pathfinder of the Seas Father of Modern Oceanography The Physical Geography of the Sea Use of windscurrents to plan shipping Mapping of ocean depths Planning of Arctic expeditions Helped found Naval AcadV a Tech Methods of Measuring Currents Directly Direct Methods Spinning propeller type Acoustics Doppler effect High Frequency Radar Backscatter from Surface Waves Doppler effect Drifters Floats Bermuda Testbed Mooring Vector Measuring Current Meters and OPL Engineers Profiling Current Meter Acoustic Doppler Current Profiler ADCP High Frequency HF Coastal Radars HF Radars are also at Coal Oil Point Sands Beach Eventually all along California and US coastlines Methods of Measuring Currents Indirectly Take some data and insert into formulastheory Indirect Methods Ekman currentstransport Need wind data from buoys ships and satellites Geostrophy balance between pressure and Coriolis forces need satellite altimetry or ship based CTD data Satellite altimeter measurements of ocean surface and bottom features Like atmosphere barometer pressure maps to see High and Low pressure systems and inferred air currents In this case it is changes in sea surface height Need meas Accuracy to a few cm s or inches FIGURE 97 The hills and valleys of the sea surface measurements of ocean dynamic topography SSH across the World ocean contribute to a wide range of scientific activities including determination of sea level calculation of Earth s geoid estimation of geostrophic currents measurements of tides and waves and many others Some Average Current Speeds 1 knot 115 mph 05 msec 1 msec 2 knots Currents de ect to right in NH left in SH WHY Upper ocean currents driven by winds Deep currents forced by density and buoyancy effects called Thermohaline Circulation Western Boundary Currents faster than Eastern Boundary Currents Example of each What Causes Currents of Upper Ocean Atmospheric circulation and wind belts of the world Subtropical gyre surface circulation patterns winds drive currents Gyre surface circulation pattern winds drive currents What causes gyres circulation patterns Ekman Currents and Transport RV Fram used by Fridtjof Nansen to observe veer of ice to right of the wind The Ekman spiral and Ekman transport Theory by VW Ekman key to upper ocean circulation patterns Summary of Ekman s Theory Ideally under no other in uences surface currents are directed 45 degrees to the right of the direction of the wind in the Northern Hemisphere to the left of the direction of wind in the Southern Hemisphere The speed of wind driven currents decreases with depth Deeper currents move sequentially toward the right Think of a stack of note cards with each successive card moving farther to the right Plots of current vectors on a graph results in a spiral pattern called the Ekman spiral Note that the spiral is the pattern obtained when velocity and direction are graphed as vectors the Ekman spiral is not a whirlpool or eddy a common misconception The Ekman layer depth is defined as the depth where the speed has decreased to a value of about 37 of its surface value This is the depth where a current vector is pointing in the opposite direction 180 degrees to that of the surface current vector The depth of the Ekman layer depends on the Coriolis parameter For a given wind stress higher latitudes have shallower Ekman layer depths while lower latitudes have deeper Ekman layer depths except for the equator Ekman transport defined as the summation of the ow direction and velocity from the surface to the Ekman layer depth is directed 90 degrees to the right of the surface wind stress in the Northern Hemisphere and 90 degrees to the left of the surface wind stress in the Southern Hemisphere The magnitude of the Ekman transport is proportional to the wind stress and inversely proportional to the Coriolis effect and seawater density Convergence of waters in center of subtropical gyre note convergence and elevation of surface toward center of gyre and downwelling of water Geostrophic Balance and Currents Center of gyre is elevated kind of like an upside down bowl so pressure gradient forces water away from center But Coriolis force enters and is directed in opposite direction The balance of forces is called geostrophic balance Resulting flow is called geostrophic ow these balances and ows occure for large scale flows in both the atmosphere and the ocean Geostrophic means earth turning The combined effects of Ekman transport geostrophic ow and wind curl generate the ow pattern illustrated at right when summed over the entire depth of the water column Why are currents faster on the western side of ocean basins The Coriolis effect s variation with latitude is key along with the conservation of angular momentum Model at top does not allow for increase of Coriolis effect with latitude Model at bottom does include this effect and explains why there is western intensification of currents Gulf Stream and Kuroshio among others Henry Stommel and Walter Munk Walter Munk o Born in Vienna in 1917 Greatest living oceanographer Predicted waves for Normandy D Day invasion of June 6 1944 other invasions Coined the term wind driven gyres and developed ocean circulation models Showed surface waves propagate long distances from Southern Hemisphere to NH OOOOO Has received virtually all possible awards and prizes accessible to an oceanographer 4 Steps to Explain Gyre Circulation and Gulf Stream Wind forces Ekman transport Geostrophic currents Variation of Coriolis effect with latitude Gulf Stream Kuroshio and other western boundary currents Mesoscale Eddies The high and low pressure systems of the ocean Baroclinic instability is the cause First observed with swallow oats like Argo oats and later with satellites o Sea surface center enter is lower for cold ring SS center is higher for warm ring A depiction of the formation of cold and warm core rings through Gulf Stream meanders Eddies or rings 100 300 km in diameter 68 180 mi in diameter Speeds 100 cmsec Lifetimes 1 mo to gt 1yr Cold Rings Cool waters rise upwell toward surface Nutrient rich waters rise toward surface With nutrients and light phytoplankton grow Other organisms graze phytoplankton More productive waters toward center More carbon ux to deep sea Coastal Upwelling NH coastal upwelling 0 Cool nutrient rich waters upwelled o Phytoplankton grow well in upper well lit layer with the input of nutrient o Zooplankton eat phytoplankton 0 Fish eat Zooplankton 0 Thus coastal areas are often very biologically productive Why are coastal California waters cool the ocean currents that carry water from up north The dominant current that ows past California is part of the North Pacific Gyre a giant spiraling circle of water that takes up most of the Pacific Ocean Coriolis effect northern breeze goes up into atmosphere 9 comes down when earth rotates and hits slightly different spot which is our location Ekman spiral water pushes westward shearing the top layer away in a different direction upwelling with top layer gone cold deeper water rises What wind conditions lead to strong upwelling along our coast Monsoons of the Indian Ocean and the Arabian Sea Monsoons of the Arabian Sea Monsoon word is derived from Arabic word mausim meaning season Northeast Monsoon Southwest Monsoon Biogeochemical responses Antarctic Circumpolar Current What is unique about this current system Currents encircle continent of Antarctica like a race track Fast moving over 150 cmsec Many eddies MiX master region of the world ocean where different waters merge Important for global climate change and life of the ocean Some of the biggest waves occur here Hazardous for ships The Arctic Ocean Uncovered Ice cover and thickness have reached lowest value since satellite obs Began in 1979 Cause Human i e CO2 CH4 andor natural i e weather oscillations The Changing Arctic Ocean AO Est of ice free AO summer by 20152080 Decreased albedo warming feedback Reduced or increased CO2 Open ocean or permafrost dominate Shift of weather patterns dur to sfc Boundary condition change Ocean circulation ie Atlantic amp Pacific waters moving north No more fishing from ice for Inupiats Many want oil product Migration of killer whales and other species northward previously bowheads ruled walruses southward to get on land Huge economic and political implications for US Canada Russia Norway Denmark Opening of oil and gas fields est of 15 of world s oil and 30 world s gas may lie here Book The Eskimo and the Oilman Other natural resources i e diamonds and gold Transport of goods via Arctic Ocean and Northwest Passage National defense issues already Russian y bys and ag at NP Equatorial Upwelling and Currents Ekman transport of water away from the equator Water from depth upwells into the upper well lit layer Brings cool nutrient rich H20 biologically productive Pacific covers almost 50 of Earth s water surface and is bigger than all of land surface Width at equator is about 7000 miles Earth circumference is about 25000 mi The Southern Oscillation El Nino occur at intervals of roughly 27 years Last really strong one was in 1997 also 1982 La Nina La Nada Southern Oscillation Index SOI and Walker Circulation Walker circulation pattern consists of descending air over the South Pacific and ascending air over Indonesia and Australia The Southern Oscillation Index rates the strength of the Walker circulation cell on the basis of differences in atmospheric pressure between Tahiti and Darwin Austrailia The greater the pressure difference the greater the strength of southeasterly trade winds If the pressure difference is exceptionally great then the southeasterly trade winds produce La Nina conditions When the pressure difference weakens or reverses El Nino conditions are produced Equatorial upwelling appears as a tongue of colder water bisecting warmer water Ribbon of green water near equator indicates biologically productive waters with high concentrations of phytoplankton resulting from upwelled nutrient rich waters into well lit upper layer ENSO is a large scale phenomenon that involves interactions of the atmosphere and ocean Effects of ENSO global teleconnections and siasters related to ENSO Atmospheric Oscillations All interacting and superimposed on Global Climate Change Southern Oscillation ENSO Arctic Oscillation North Atlantic Oscillation Antarctic OscillationSouthern Annular Mode Pacific Decadal Oscillation PacificNorth American teleconnection PNA Atlantic Multi decadal Oscillation Sir Gilbert Walker 18681958 British Physicist and Statistician Educated and researched at Cambridge Top undergrade mathematician Senior Wrangler Greatest intellectual achievement attainable in Britain Wrangler ceremonies began in 1748 Other Senior Wranglers John Herschel George Stokes Lord Rayleigh Studied Indian Ocean Monsoons Director of Observatories in the Indian Meterological Service in 1904 Concern about lack of Monsoon rains in 1899Prediction goal Discovered Large scale teleconnectionseasaw between Indian and Pacific atmospheric pressure Correlations with temperature and rainfall Key work for Southern OscillationLarge scale climate Deep Sea Circulation Thermohaline Circulation What drives currents of deep ocean Temperature and salinity are good tracers Today other chemical and manmade and natural tracers are used as well to give more information including time scales The Great Ocean Conveyor Belt model of ocean circulation While highly oversimplified Broecker s illustration identifies the surface and deep circulation and the general linkages between them The world ocean circulation showing the coupled surface and deep circulation Note that waters from all three major basins the Atlantic Pacific and Indian intermingle in the Southern Ocean This model by Ray Schmitz is more detailed and likely accurate than Broecker s What is the importance of deep circulation and the Great Ocean Conveyor Belt 1 Deep circulation is slower than upper ocean circulation 2 It may take roughly 25 years for a water parcel to go around the North Atlantic gyre but several hundred to a thousand years or more for a parcel to track thought the deep ocean 3 Formation of deep water in North Atlantic may stop because of global warming with high latitude fresh ice metl waters and more precip Capping off upper layer and causing stoppage of deep circulation This occurred about 8200 years ago 4 If this happens extreme weather and an ice age could be triggered This is a negative feedback for global warming This was the storyline of the movie The Day After Tomorrow which way speeded up the time scale Ocean Models Use data theories computers to aid in understanding and making predictions about the ocean Chapter 10 Ocean Waves 2514 1048 PM Why are surface waves important Ships at sea Perfect Storm Military naval operations D Day Marine organisms and animals surfing critters Transport of sand and sediments Beachfront damage Recreation eg surfing etc Energy source Current meters Tide gauges and wave staffs Bottom pressure sensors Wave rider buoys Coastal radar Satellites Altimeters Microwave scatterometers Why is there an Equatorial Undercurrent Bottom pressure sensors are used to measure passages of tsunamis at sea Can resolve 1 cm wave height variations in 6000m depth waters Changes in hydrostatis pressure occur with the passing of a wave and can be used to detect surface waves using pressure sensors on the sea oor Most importantly these pressure sensors can detect the passing of a tsunami They are the first line of defense in tsunami warning systems TOPEXPOSEIDON satellite altimeter to measure wave heights to within a few cm s Jacob Bjerknes 18971975 Norwegian son of Vilhelm Father of Modern Meteorology PhD University of Oslo Taught at MIT founded Meterology Dept at UCLA Support meteorologist for Amundsen s airship crossing of NP How can we define and quantify waves and their characteristics 0 A amplitude H2 o S steepness HL o C wave speed o Where T wave period h water depth o Wave frequency 1T in cycles per second or Hertz Hz o Wave period T in seconds What are the classes of surface gravity waves Trans tidal waves long period waves infra gravity waves ultra gravity waves capillary waves What causes surface gravity waves Caused by disturbances such as Winds and atmospheric pressure Earthquakes submarine landslides and volcanoes Ship movement Meteors Disturbing force 9 sun and moon earthquakes storms wind What are restoring forces Gravity the passage of wave energy causes water parcels to have positive or negative buoyancy relative to sea level The force of gravity restores uid particles to their resting level which is why ocean surface and internal waves are called gravity waves Surface Tension Coriolis Effect How do wind waves develop and evolve What is wave fetch Capillary and gravity waves capillary waves ruf e the surface of an estuary Surface slicks appear where natural and man made organic substances prevent the propagation of capillary waves creating a smooth glassy appearance to the water s surface Mile s Theory Sustained winds over large expanses of the ocean such as those produced by storm systems generate most of the waves observed along the shore Conceptual model of wave development from capillaries to ripples to ocean swell Not fetch windsea and groundswell What affects surface gravity wave phase speed c Recall c LT where L is wavelength and T is wave period Wave Speed Versus Wavelength for Different Water Depths A family of curves based on Equation 102 illustrating the mathematical relationship between wave speed wavelength and water depth In Shallow waters wave speed for nearly all wavelengths is governed solely by water depth In deeper waters wave speeds generally increase with increasing wavelength Shallow Versus Deep Water Waves Deep Water Waves Deep water waves are surface waves that travel in waters with depth h gt L2 where L wavelength Note Wave speed depends on L and longer waves travel faster These waves have circular orbital motion decreasing rapidly with depth For deep water wave case longer wavelength and period waves travel faster Therefore these waves disperse meaning move away from each other Wave Orbitals for Deep Water Waves Deep water waves are defined as waves traveling in water depths greater than 12 the wavelength Intermediate water waves are defined as waves traveling in water depths less than 12 the wavelength but greater than 120 the wavelength Shallow water waves traveling in depths less than 120 the wavelength Shallow Water Waves Shallow water waves are surface waves that travel in waters with depth h lt L20 Note Tsunamis are shallow waves even though they often travel in the deep ocean as their wavelengths are long Note Speed depends on depth and waves in deeper water travel faster Note Orbitals are elliptical Wave Orbitals for Shallow Water Waves Shallow water waves traveling in depths less than 120 the wavelength Wave Steepness and Breaking Surf zone what happens to wave speed and steepness as waves move into shallower waters o If h decreases then c decreases as c ghquotl2 o L decreases H increases o S HL increases when S reaches a value of S 17 wave breaks Steepness S HL When S gt 17 or S gt 014 waves typically break Check out three examples at right Breakers What value is wave steepness for this breaker Wave Interference and Rogue Waves Constructive vs Destructive vs Mixed Example of two waves with same wavelengths and periods Constructive Destructive Mixed Rogue waves along the wild coast off South Africa wave current interactions Wave re ection similar to re ection of light Wave refraction similar to light refraction o Refraction along a straight shoreline wave speed changes which results from waves moving obliquely into shallower waters causes refraction Wave shadowing by islands Similar to light shadowing Wave diffraction similar to light diffraction o Wave diffraction of ocean surface waves o Light wave diffraction is similar phenomenon famous double slit experiments often shown in physics classes o Diffraction occurs when the size the opening between barrier is similar to that of the wavelength of the impinging waves Rip currents beaches and sand movements Waves for surfers a great way to review surface waves What factors affect surf 1 Location and strength of storms how far are you from source of waves Windsea or groundswell 2 Direction of winds and fetch 3 Season waves produced in NH or SH 4 Tides 5 Sea breeze effects steepen or atten local waves 6 Water depth or bathymetry changes with sand movement tides and storm surge and slope 7 Coastal shape points or bays 8 Angle of impingement of waves on shoreline 9 Refraction re ection diffraction shadowing 10 Wave interference constructive or destructive 1 1 Current interaction with waves Waves for surfers a great way to review surface waves What Factors Affect Surf 1 Location and strength of storms how far are you from source of waves Windsea or groundswell 2 Direction of winds and fetch 3 Season waves produced in NH or SH 4 Tides 5 Sea breeze effects steepen or atten local waves 6 Water depth or bathymetry changes with sand movement tides and storm surge and slope 7 Coastal shape points and bays 8 Angle of impingement of waves on shoreline 9 Refraction reflection diffraction shadowing 10 Wave interference constructive or destructive 1 1 Current interaction with waves Development of a cutoff low good for producing big surf Development of a major low cyclogenesis good for producing big surf far away Waves Break for Different Tidal Conditions Wave Groups Groupiness and Settiness Surf Tips Tsunami Between storm center and coast waves organize into groups or sets Groups of waves travel at group velocity which is 12 of individual phase velocity for deep water waves Be careful of rip currents Avoid water after storms waterborne bacteria and viruses Sharks hang out around river in ow areas especially after storms Harbor wave in Japanese Colloquially called a Tidal wave A tsunami is a special ocean surface wave caused by a sudden large scale disturbance resulting in the vertical displacement up or down of the ocean surface What causes a tsunami Earthquakes Landslides Volcanoes also meteors Generation of a tsunami via an earthquake that causes vertical displacement of sea oor and Water column above up or down Subduction thrust type earthquakes are most effective for producing a tsunami A New Tsunami Theory A No energy transferred B No energy transferred Potential energy transferred Kinetic energy transferred Tsunami Characteristics Tsunami speed 800 km hour jet plane speed Wave length Wave height Reaches shore Rip currents beaches and sand movement How fast do tsunamis travel in the deep sea Speed c ghquotl2 G acceleration due to gravity constant 322 ftsec 2 H water depth 12 124 ft ave in deep sea But waves slow rapidly in shallow waters and water piles up creating large pulses of Water onshore called run up Near shore height near shore can reach over 100 ft Chapter 1 1 Tides 2514 1048 PM Why are tides important Ships and boats at sea water depth and currents Tide clocks on churches in England Military naval operations landing units Marine organisms and animals tidal zone Transport of sand sediment and pollutants Beachfront damage coupling of high tides large waves and storm surge Mixing and energy dissipation in ocean friction Renewable energy source When to go surfing Electromagnetic field of Earth MHD Solid Earth and atmospheric tides Slowing of Earth s rotation Causing seismic activity and earthquakes Important for life on other planets and moons Tides have fascinated man from earliest times Aristotle studied tides in ancient Greece with great frustration Chinese observed tides and moon in 1 AD Modern theory of tides is based on work of Sir Isaac Newton Bernoulli and later Laplace Also Lord Kelvin built tide prediction machine and the Kelvin wave is key part of tidal theory How can we measure tides Tide gauges and wave staffs Bottom pressure sensors Current meters High frequency radar Satellite altimeters What causes tides Earth Moon Sun The gravitational forces between the Earth moon and sun exert the strongest in uence on ocean tides Differences in their gravitational attraction at different points on Earth give rise to the tide producing force Astronomical constants useful for computing tide causing forces and calculation of the relative force of the sun and the moon Semi diurnal tide The semi diurnal tide has a period of 125 h about 2 high and 2 low tides per day This is caused primarily by rotation of earth and orbiting of moon about the earth What are the three types of tides Semi diurnal tide with period of 125 h Diurnal tide with period of 250 h Mixed tide with both semi diurnal and diurnal tide important Amplitudes and phases of tides Tidal Bores 1 Formed when incoming tidal wave is forced to move faster than a shallow water wave and exceeds outgoing river current ow 2 A shock wave like a sonic boom space shuttle landing forms and moves up a bay river or fjord this is a tidal bore river ow then reverses direction 0 The size of the bore depends on geometry of bottom and the dimensions of the bay river or fjord narrowing or funneling and resonance come into play 4 Big bores usually produced where tidal range is great 5 Name bore comes from old Norse word bara meaning wave or swell 6 They can come in as a single wave or as a series of peaks called solitons or solitary waves like tsunamis l There are both surface and internal tidal bores and solitary waves 00 Large internal solitary waves off LA resuspend DDT Solitary waves also exist in open ocean Solitary waves are used for fiber optic communication low power loss Tides are caused by balance of Gravity forces between Earth and moon and sun and Earth Tide generating force TGF is given by TGF prop To mass of moon or sun distance Is the Moon or Sun more important for tides Tide generating force is proportional to mass of moon or sun distancequot3 Since moon is much closer to the earth the moon is more important despite much smaller mass Note Sun force is less than half that due to moon
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