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Oceanography Notes Midterm Corrections o Lines of latitude measure north-south with respect to the equator o Old, cold oceanic lithosphere more dense than: underlying warm aesthenosphere continental lithosphere younger oceanic lithosphere o Continental Margin order: Shelf, Slope, Rise o Oceanic crust floats lower on mantle because it is denser o Free oxygen produced by photosynthesis o Evaporation is a warming process Chapter 6 o o o o o o o o o o o o o o o o o o o o o atmosphere and ocean interdependent surface currents correlate with wind belts interchangeable results b/w ocean/atmos radiant energy from sun responsible for motion in atmos and ocean ecliptic: the plane traced by earth’s orbit earth tilts at 23.5% earth axis is always pointing in same direction, toward Polaris [N Star] -causes seasons vernal equinox: occur about 21 March, sun directly overhead along equator. -during this, all placed on earth experience same length night and day -N hemis, this is spring summer solstice: june 21. sun at most northerly point in sky, directly above tropic of cancer -at noon this day, sun seems to pause in sky. Tropic of cancer: 23.5 degrees N lat Autumnal equinox: sept 23. sun directly overhead along eq again. -also known as fall equinox in N hemis. winter solstice: dec 22. directly overhead at tropic of Capricorn -S hemis seasons reversed, this is when S hemis most directly facing sun. This is beginning of S hemis summer. tropic of Capricorn: 23.5 degrees S lat declination: angular distance from equatorial plane -sun’s declination varies b/w 23.5 degrees N and S lats on yearly cycle tropics: region b/w Capricorn and Cancer -receive greater annual radiation that poles N hemis: longest day-summer solstice, shortest day-winter solstice Exceptions to daily cycles of light and dark: Arctic circle: 66.5 degrees N lat Antarctic Circle: 66.5 degrees S lat -during N hemis winter, area N of arctic circle experiences 6 months darkness, area S of Antarctic circle experiences 6 months daylight half a year later, this situation reversed sunlight strikes low lat at high angle; radiation concentrated in small area sunlight strikes high lat at low angle; same amount of radiation spread over larger area atmosphere absorbs radiation, so less radiation at high lat, b/c passes through more atmosphere Albedo: percentage of incident radiation that is reflected back to space. -avg albedo of earth’s surface: 30% -ice has higher albedo than soil or vegetation so more radiation reflected back into space at high lats o o o o o o o o o o o o o o o o o o -angle at which sunlight strikes ocean surface determines how much absorbed and how much reflected -directly: 2% reflected -5 degree above horizon: 40% reflected -so, ocean reflects more radiation at high lats Elevation of sun above atmosphere: 90 60 30 15 5 Reflected radiation [%] 2 3 6 20 40 absorbed radiation [%] 98 97 94 80 60 amount of radiation varies annually due to Earth’s seasons amount of radiation varies daily b/c of day and night due to rotation temperature difference b/w equatorial zone and poles remains the same, b/c excess heat transferred from equatorial zone to poles [circulation atmos and ocean] Composition of dry air: Nitrogen 78.1% Oxygen 20.9% Argon .9% CO2 .037% Other trace troposphere: surface-12km[7m]. all weather produced here. much atmospheric mixing. -temperature is cooler with altitude in troposphere air has density higher temperature, lower density [for air] -warm air rises, cool air falls convection cell: rising and sinking air moving in circular fashion warm air holds more water vapor because it has more contact with water vapor due to quick moving particles. warm air moist, cool air dry -warm breezy air-evaporation more water vapor in air=decreased density atmospheric pressure= 1.o atmosphere [14.7lbs/sq inch] at sea lvl -decreases with increasing altitude [pressure depends on weight of air column above] column of cool dense air: high pressure at surface; leads to sinking air -movement toward surface and compression column of warm, less dense air; low pressure at surface; leads to rising air -movement away from the surface and expansion air always moves from high to low pressure areas principles that drive physical movement of air remain same whether earth is spinning or not Coriolis Effect: changes the intended path of a moving body. Gaspard Hustave de Coriolis [1835]. does not influence the body’s speed [not a force] this effect causes moving objects on earth to follow curved paths N hemis; object goes right S hemis; object goes left the directions right and left are the viewer’s perspective looking I the direction in which the object is traveling -ball thrown b/w two people will curve slightly to right in N hemis from the thrower’s point of view -greater effect on objects going long-distance, especially N-S result of earth’s eastward rotation the difference in the speed of Earth’s rotation at difference lats causes this effect o o o o o o o o o o o maximized at poles and zero at the equator. merry-go-round; fall off tangent to circle Coriolis effect perspective; the one looking in direction object is moving distance that a point must travel in a day shorter with increasing lat 1600 km/hr earth sping rate [0 at poles] this change in velocity w/ lat is true cause of Coriolis effect 1400km/hr at 30 degrees lat N and S missile launched straight at target will curve right [to the eye], but really, that target [point on earth] has a faster or slower velocity that the launch point friction not taken into account; has a great effect rate of change of rotational velocity [per degree of lat] increases as the pole is approached from equator [from 200km/hr b/w eq and 30 deg N lat to 600km/hr b/w 30 deg N lat and 60 deg N lat] 60 deg N lat- N pole -> 800km/hr difference max Coriolis effect at poles, no Coriolis effect at equator Coriolis effect summary: -caused by earth rotation and resulting decrease in velocity with increased latitude -influences all moving objects, esp those moving over large distances -changes only direction, not speed -deflection to the right in N hemis, left in S hemis -O at equator; increases with increasing lat; strongest at poles. Hadley Cells: George Hadley [1658-1768] circulation cells resulting from dry air mass at equatorial zone traveling N or S of equator at 30 deg lat becoming dense enough to sink and complete the loop Ferrel cell: 30deg-60deg lat. William Ferrel [1817-1891]. Invented 3-cell [er hemis model. Cell moves coinciding with adjacent cells. Polar cells: 60deg-90deg lat. subtropical highs: high rpessure cones caused by descending air at 30deg N and S lat. polar highs: high pressure regions caused by descending air at poles -both areas: warm under own weight; dry, clear, fair conditions. Not necessarily warm equatorial low: rising air causing a band of low pressure at the equator subpolar low: rising air causing a band of low pressure at 60 deg lat. -both areas: cloudy with much precipitation, because rising air cools and cannot hold its water vapor trade winds: massed of air moving from subtropical high pressure belts to equatorial low pressure belts -steady winds named from “to blow trade” [to blow in regular course] -if earth did not rotate, trade winds blow NS N hemis; northeast trade winds: curve to right; from NE to SW S hemis; southeast trade winds: curve to left; from SE to NE -the coriolis effect curves these winds prevailing westerly wind belts: some of descdending air in subtrops moves along surface to highest lat -SW to NE in N hemis; NW to SE in S hemis polar easterly wind belts: air moving away from high pressure at poles -Coriolis effect at poles strongly deflects winds -blow from: NE in N hemis, SE in S hemis. When polar easterlies collide with prevailing westerlies at subpolar low pressure belts [60 deg lat], the warmer, less dense air of westerlies rises above. o o o o o o o o o doldrums: boundary between trade belts. Lack of winds here. Intertropical Convergence Zone [ITCZ]: doldrums. Between where trade winds converge. Horse latitudes: boundary between prevailing westerlies and trade winds [30 deg lat] -high pressure, clear, dry, fair conditions -air is sinking and surface winds are light and variable [not much rain] polar front: boundary between westerlies and easterlies [60 deg lat] -cloudy, much precipitation. Battelground for different air masses poles are cold deserts [not much precipitation] Ferrel 3-cell idea is only general. Other factors: 1] tilt of earth’s rotational axis, producing seasons 2] low heat capacity of continental rock: colder winter, hotter summer than over oceans 3] Uneven distribution of land, particularly affecting N hemis patterns during winter on continent: atmospheric high pressure, summer: low pressure. such seasonal atmospheric pressure over Asia causes Monsoon Winds. Christopher Columbus: Italian navigator. Toscanelli: astronomer -reached canary islands Aug 3, 1942 -called West Indies inhabitants “Indians” because he thought they were near India -1498; South America 1502; Central America Chapter 6 Lecture Solar energy creates winds Example of interactions: El Nino, Greenhouse Effect Theory: Earth tilt due to Mar’s affect. 35degN-35degS->heat gained Other lats, heat lost Heat gained moves to poles troposphere: 60degC-50degC at min temp Topopause-Stratosphere-Ozone layer-Mesosphere dry air and cool air sink <-more dense moist air and warm air rise<-less dense -moist air less dense than dry air because water has less mass than N2+O2 high pressure->air coming down; low pressure->air rising deserts have cool/dry air coming down cool dense air, higher surface pressure Chapter 6 cont… o weather: conditions in atmosphere at given time and place o climate: long-term average of weather o cyclonic flow: CCW flow of air around low pressure cells as a result of Coriolis effect on air moving from high to low pressure curving it to the right [N hemis] o anticyclonic flow: air leaving high pressure region and curves right, establishes CW flow of air around high pressure cells [N hemis] o low pressure->clouds high pressure->sun o winter high pressure cells replaced by summer low pressure over continents, so continental wind patterns often reverse themselves seasonally. o land breeze: cool air sinking, blowing over ocean in early morning hours. -due to cool sinking air over continents at night as a results of continents having low heat capacity o sea breeze: warm air rising, blowing cool air from ocean over continent in afternoon. -due to warm air rising over/above continents during day as a result of continental low heat capacity. o Region 0-5 5-30 30-60 60 60-90 Poles o o o o o o o o o o o o o o o o o o o Wind Belts and Boundaries: Name Pressure Doldrums L Characteristics Light variable wind. Cloudy/Precip. Hurricanes breed here Trade Winds Strong, steady winds generally from E Horse Latitudes H Light, variable wind. Dry, clear, fair. Little precip. Major deserts here Prevailing W Winds generally from W. Brings USinfluencing storms Polar Front L Variable wind. Stormy/cloudy year-round Polar E Cold, dry winds generally form E Polar High H Variable winds. Clear, dry, fair, cold Pressure temp, min precip. Cold deserts here. Very high and very low lats, little daily and minor seasonal change in weather midlatitudes: where storms are common storms: atmosphere disturbances: strong wind, precip, thunder/lightning air masses: large volumes of air: definite area of origin, distinctive characteristics. -polar and tropical air masses influence US -most originate over sea. those from land are drier -US influenced more by: polar air masses in winter/tropical air masses in summer -[c]continental [m]maritime [T]tropical [A]arctic [P]polar warm front: contact between warm air mass moving into area of cold air -as air masses move to midlats, they move E some cold front: contact between cold air mass into warm-air area jet stream: narrow, fast, Eastward-flowing air mass. Causes fronts. -above mid lats just below top of troposphere, 6miles high -follows wavy path; causes unusual weather by steering [P] or [T] too far N or S warm always rises above cold temperature difference across cold front greater than warm front -so, rain of cold front usually heavier, briefer Tropical cyclones: huge, rotating masses of low pressure: strong wind, torrential rain -largest systems on Earth -no associated with fronts hurricanes: name in N, S America typhoons: W N Pacific ocean cyclones: Indian ocean energy of single hurricane greater than all that created in US in 20 years. tropical cyclone begins as low pressure cells break from equatorial low pressure belt, grows as heat energy from ocean picked up -the surface winds feed moisture [water vapor] into storm -the release of vast amounts of water’s latent-heat of condensation power tropical cyclone. Tropical cyclone classification: tropical depression: winds below 38mph tropical storm: 38<winds<74mph tropical cyclone: 74mph<winds Saffir-Simpson Scale: hurricane intensity; further classifies; wind speed, dmg 250mph a high 100 tropical cyclones each year. conditions to create: ocean water temperature > 25C -> for evaporation warm/moist air -> supplies latent heat Coriolis effect; cyclone spin CCW in N hemis, CW in S hemis o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o No cyclone directly on equator, because Coriolis is zero. Happens on equator once every 300-400 years June 1-Nov 30 “hurricane season” [not limited to this time frame] hurricanes typically remain in tropics. Driven by trade winds so they move E to W. Last 5-10 days. If more over land, energy source is lost, so they dissipate diameter avg 124miles but can be 500+ eye of the hurricane: low pressure center: air here spirals upward; usually calm spiral rain bands compose hurricanes; several inches of rainfall per hour storm surge: responsible for most of a hurricane’s dmg. [90% deaths]. Hill of water -low pressure center produces hill up to 40ft high. -hill where wind blowing shoreward climbs shallow water onto shore. Very bad at high tide. -dramatic increase in sea lvl at shoer -where onshore winds further pile water hit most severely Galveston Texas, 1900; 7000 dead. Category 4. Category 5 3x; 1935[Keys], 1969[Mississippi], 1992[Andrew FL] Mitch [Central America 11k dead] most of world’s tropical cyclone formed in water N of equator in West pacific ocean. 1970 [Bangladesh 40ft Storm Surge killed 1 million] another in 1972; 500k dead. ’91; 200k ocean climate patterns run E-W, are stable. modified by ocean surface currents. equatorial: region spanning equator. abundance solar radiation. Major air movement upward. -storms form here. tropical: regions N/S to cancer, Capricorn. Strong trade winds. NE in N hemis, SE in S hemis. Rough seas. -storms gain energy here. subtropical: regions beyond tropics. High surface salinity. belts of high pressure. little precipitation, much evaporation. Winds weak, currents sluggish. strong boundary currents N-S, particularly along west margins. temperate: regions [midlats] strong westerly winds; from SW in N hemis, NW in S hemis. severe storms, heavy precip. winter esp subpolar: regions; extensive precip due to subpolar low. sea-iced-covered in winter, melts in summer. icebergs common, surface temp rarely greater than 41F in summer polar: region; temps remain at or near freezing. covered with ice, most of year. No sun in winter, all sun in summer sea ice: masses of frozen ice. low temp/high lat icebergs: break off [calve] from glaciers that originate on land pancake ice: forming slush into thin sheet broken by wind and waves ice floes: layer of ice when further freezing occurs to pancakes rate of ice form slows as it thickens, because top ice insulates water below calm water and low temp aid ice formation most of dissolved substances remain in water, notice. Salinity increases under ice. -decreases the freezing point of water -ice becomes ink below surface-> lower surface salinity water freezes in place 17% decrease in overall ice extent accelerated melting at interior poles -due to shifts in N hemis atmosphere circulation patterns most breaking-up [calving] occurs in summer high temps icebergs from in Greenland narrow valleys to ocean. o o o o o o o o o o o o o o o o o o o o o o o o -E and W Greenland current carry bergs into N Atlantic shipping lanes -may take years to melt shelf ice: thick floating sheets of ice formed at edges of glaciers in Antarctica [B-15 4250 sw mile iceberg from shelf ice breaking off] 90% icebergs mass below sea lvl flat tops up to 650ft high. Most below 530ft high Larsen ice shelf decreased by 40% since 1997 rate of warming; .5C per decade Argo located Titanic 1985 Robert Ballard World average temp Earth and troposphere: 15c [59F] greenhouse effect: keeps Earth’s surface and lower atmosphere warm. most of sun energy that reaches earth surface: short wavelength, visible almost longer-wavelength infrared radiation; heat; short-wavelength energy converted to this energy when it strikes the surface. energy trapped in atmosphere by ozone layer heat budget: 100 units shortwave solar radiation reflected, absorbed, scattered by various components of Earth 47% of solar radiation absorbed by oceans and continents 23% absorbed by atmosphere and clouds 20% reflected to space by backscatter, clouds, and Earth’s surface peak of intensity of energy of sun; .0002inch wavelength, within visible spectrum earth materials that absorb energy reradiate it back to space as longer wavelengths: infrared [heat. .004 inch long] rates of absorption and reradiation are equal greenhouse effect produced by heat-trapping gases trapping reradiated heat, and reradiating this heat once more. change of wavelength from visible to infrared is the key to understand how greenhouse effect works solar radiation received at the surface is retained for a time in the atmosphere; moderates temp day/night/seasons water vapor contributes more to greenhouse effect more than any other gas. unaffected by human activity CO2 concentration increase 30% over 200years -increase by 1.2ppm/yr the other greenhouse gases, though lesser concentrations, are important, because they absorb far more infrared radiation per molecule than CO2. But still, not as important as CO2. Melting glaciers, early springs, species distribution shift, rise in average temp all indications Avg temp up .6C in last 130yrs. Possible effects: -higher sea-surface temp [more tropical storms, alteration in deep water currents] -most severe drought, more intense precip -water contamination [larger outbreaks disesase] -longer/more intense heat waves -shift in distribution of life -melting ice caps [rising sea lvl] possible that ice caps enlarge. how?: Warmer temp->more evp->more precip on land->potentially increasing snowfall for creation of ice caps->lower sea lvl some positives: increased growing season some places, plant like flourish w/ CO2 CO2 estimates prior to 1958 estimated from air bubbles in ice cores Intergov’l Panel on clamate change [IPCC] 1988; 200 scientists begin studying human effects on global warming; conclude that human impact exists. o o o o o o o o o o o o o o o sedimentary rock and forests are natural storage places for organic CO2; being released. Kyoto Protocol: 1997; 60 nations; voluntary reduce emissions. US to reduce emissions 7% below 1992 emissions by 2007: WE FUCKING WITHDREW! Also to transfer technology to other countries with them becoming producers of much greenhouse gas 2nd IPCC: 2001: 1.4-5.8C temp increase between 1990-2100 Oceans absorb lots of CO2 CO2 30x more soluble in water than other gases more CO2 found in ocean than in atmosphere most of this CO2 incorporated into organisms ->photosynthesis ocean acts as sink for CO2; soaks it up, deposits it as sea floor deposits. by removing more CO2 from ocean, it can absorb more iron hypothesis: John Martin 1987; productivity low in tropical regions because absence of iron, he proposed fertilizing ocean with iron. adding iron to ocean increase productivity up to 30x long term effects adding iron and CO2 to ocean are unknown fear of oxygen depletion in these areas. some companies filed patents pump emissions into deep-ocean reservoirs SOFAR channel: layer of ocean at 1000m caused by temperature and pressure conditions causing sounds from above and below to become bent in layer. Sound is trapped, transmitted long distances Walter Munk: to use channel to detect global warming. ATOC exp speed of sound in seawater increase as temp increase. Lecture Chapter 6 continued o Low pres; CCW rot o high pres ; CW rot o more evaporation over low pressure o most weather generated at seas o hurricane wind speed: at least 74mph o air exiting eye of hurricane comes out at left, but then once free, curves right o Coriolis affect ocean and atmosphere: causes Hadley cells causes W ocean basin current intensity [Gulf Stream] causes CCW; tornadoes, hurricanes o “Fixed Reference Frame” -> “intertial frame” o gravity does not affect direction Wrong Answers from Site o Air rises at 60 degrees latitude and falls at 30 and 90. o Sun is directly over equator at both vernal and autumnal equinox o Water vapor contributes the most to greenhouse warming o Land breeze flows from land to sea o Wind belts created by lowermost portion of circulation cell o Surface winds of anticyclone in S hemis go CCW o most abundant gas in atmos is nitrogen o least abundant gas is carbon dioxide o polar easterlies between 60-90 degrees o polar front at about 60 degrees o increase earths tilt; warmer summers, cooler winters o Coriolis; CW rot around high, CCW rot around lows o air moves in and up in low pressure areas o surface winds in tropics [trade] blow W and toward equator o midlat storms: contrasting air masses, jet stream, westerlies, polar front o o cause hurricanes: trade winds, warm ocean, water vapor rich warm air, jet stream more intense storms maybe with global warming Chapter 7 o o o o o o o o o o o o o o o o o o o o o ocean current: masses of ocean water from one place to another. Any mass, Any depth, simple or complex. huge current system dominates surfaces, transfer heat from warmer to cooler areas. transfer 1/3 of heat, wind belts transfer 2/3 sun drives surface currents closely follow windbelt patterns cold currents flowing toward equator on W sides of continents produce arid conditions warm currents flowing poleward on E sides of continents produce warm, humid conditions ocean currents contribute to mild climate of N Europe and Iceland; conditions at similar lats along Atlantic coast of N America much colder. currents deliver ocygen in cold, dense water, and they helped prehistoric peoples travel currents either wind or density driven surface currents: caused by wind belts parallel to the surface. Horizontal deep currents: caused by cold, dense water sinking. vertical surface currents rarely flow in same direction at same rate -measuring is difficult: can be measured directly or indirectly -some consistency exists in overall surface current pattern Direct measurement: 1]floating device placed into current; tracked through time 2]place device in current from fixed position Indirect measurement: 1]determine the internal distribution of density and the corresponding pressure gradient across an area of the ocean 2] radar altimeters [TOPEX/Poseidon satellite 1992]: determine bulge’s in sea surface which are results of the shape of the underlying sea floor and current flow. dynamic topographic maps produced from this data that show speed/direction of surface currents 3]Doppler flow meter to transmit low-frequency sound signals through the water. measures shift in frequency between the sounds water emitted and those backscattered by particles in the watter to determine current movement. deep current measurement: -more difficult to measure because of depth -mapped by: -device carried with current -tracking telltale chemical tracers -some traces absorb into seawater, other intentionally added -useful tracers [tritium from atom bomb tests][chlorofluorocarbons freons and other gases] -measure temp/salin characteristics of deep ocean currents surface currents occur within/above pycnocline to a depth of 1km surface currents only affect 10% of ocean water due to friction with wind 2% of winds energy transferred to ocean surface. 50-knot wind produces a 1knot current if not continents, surface currents would follow major wind belts. o o o o o o o o o o o o o o -interaction between trade winds and prevailing westerlies creates circularmoving loops of water in Atlantic ocean gyre: large, circular-moving loops of water driven by major windbelts. subtropical gyres: 1]North Atlantic 2]South Atlantic 3]North Pacific 4]South Pacific 5]Indian Ocean [mostly S] -coincide with subtropics at 30 N, S lats -CCW in S hemis. CW in N hemis Each composed of 4 mains currents that flow into one another: equatorial currents: motion trade winds b/w tropics. From SE in S hemis, NE in N hemis. -travel westward along equator: form equatorial boundary current of subtropical gyre. western boundary currents: caused by coriolis effect deflecting the equatorial currents that have reached a continent away from the equator. -Western boundary of subtrop gyres Northern/Southern boundary currents: B/w 30 and 60 lat: caused by prevailing westerlies from NW in S hemis and SW in N hemis. Direct currents easterly. -comprise Northern for N subtrop gyres, visa verse for S eastern boundary currents: Coriolis effect and continental barriers turn currents toward equator when they flow back across the ocean basins -eastern boundaries of subtrop gyres equatorial countercurrents: water on western margins flowing downhill under influence of gravity due to avg sea lvl at westward margins being as much as 2m higher than on eastern side. -flow east -apparent in pacific -affected by shape of continents in Atlantic -strongly influenced by monsoons in Indian ocean. subpolar gyres: currents [of prevailing westerlies] moving westerly by polar easterlies -at 60 lat -rotate opposite the adjacent subtrop gyre -smaller and fewer than subtrop gyres Fridtjof Nansen: 1861-1930; Norwegian explorer; voyage in unexplored Arctic Fram: his ship. 39m. wooden; designed to be pushed to surface by freezing water nansen bottle: for collecting water samples at depth Arctic ocean ice moves 20-40 to the right of wind blowing across its surface -in S hemis, surface currents move to the left of wind direction V. Walfrid Ekman: [1874-1954]; Swedish physicist; developed: Ekman Sprial: explains Nansen’s observations in accordance with Coriolis effectl describes speed/direction of flow of surface waters at various depths o -assumes a uniform column of water set in motion by wind blowing across surface o -N hemis: immediate surface water flow 45 to right of wind [S hemis left] o -as surface water moves, it sets in motion other “layers” beneath it current speed decreases with incrasing depth, and coriolis effect increase curvature to right at same depth, water may move exactly opposite the direction the wind that started it is going. deep enough water, friction consumes energy of wind and there’s no motion: normally occurs at 100meters. Ekman Transport: All layers combine to create new water movement that is 90 from the direction of the wind. 90 right of wind in N hemis, left in S hemis o o o o o o o o o o o o o o o o o -nothing is ideal: Ekman Transport in open ocean is typically 70, nearly same direction as wind in shallow coastal waters subtropical convergence: water in middle of a gyre, causing water to literally pile up in center of subtrop gyre. caused by Ekman transport causing CW rotation within ocean basin -resulting in all subtrop gyres having a 2meter high hill geostrophic current: when coriolis effect and gravity balance, causing the water wanting to fall down the hill to move around it. -path of the ideal geostrophic flow -hill has a steeper westward slope -path of actual geostrophic flow: friction results in this current eventually downhill El nino event affects currents greatly S Pacific less intense than other gyres, because large area, many islands. there is a narrow and strong flow to north on western side of subtrop gyres in N hemis. narrow strong flow to South in S hemis [still on W boundary of gyre] general: western boundaries of subtrop gyres faster, narrower, deeper -due to apex being closer to W side -Kuroshio 15x faster, 20x narrower, 5x as deep as Cali current western intensificiation: this phenomenon: currents affected by this are western intensified -ALL W boundaries of subtrop gyres are western intensified -Coriolis effects eastward, high lat water, making it turn toward equator more strongly; -causes wide, slow, shallow flow of water toward equator across subtrop gyres [picture a funnel] -surface currents directly influence climate of adjoining landmasses -warm current; warm air; rain over continent -continental margins with warm offshore currents typically have humid climate [E coast] -temperature migrate N-S with seasons -continental margins with cold offshore currents typically have drier climate [W coast] Upwelling: vertical movement of cold, deep, nutrient-rich water to surface Downwelling: surface water -> deeper productivity: presence of microscopic algae -cold water= better productivity supports larger marine life downwelling less productivity, but carries oxygen dissolved to deep-ocean life current divergence: surface water away from an area on ocean’s surface: equator geographical equator: 0 lat meteorlogical equator: ~5lat N equatorial upwelling: caused by trade winds causing current divergence -> Ekman transport causes surface water N of equator to veer right [Northward] and water south of equator to veer left [southward]: divergence of surface current along geographical equator -high productivity current convergence caused by currents movement toward each other ex] N Atlantic; Gulf Stream, Labrado, E Greenland currents come together water piles, sinks coastal winds can cause either welling due to Ekman transport coastal upwelling: caused by coastal wind from the S [in S hemis] causing Ekman transport to move coastal water to the left, away from coast [on a western coast of continent] Water from below rises to replace this water o o o o -W coast US experience this. Natural air conditioner in the summer coastal downwelling: just the opposite. both upwelling and downwelling common in high latitudes absence of pycnocline allows lots of vertical mixing upwelling also caused by: offshore winds, seafloor obstructions, sharp bend in coast. Chapter 7 Lecture o Most productivity in coastal areas o summer in Arabian sea, wind blows SW->NW with respect to India o eastern boundary currents greatly affected by coriolis effect o ice dam cold water into oceans would hinder N Atlantic circulation Chapter 7 cont… Antarctic circulation dominated by movement of water mass South of 50 S lat anarctic Circumpolar Current [West Wind Drift]: main Antarctic current; encircle antarctica W->E at 50 S lat, but varies b/w 40 and 65 S lat directed from Antarctica subtropical convergence: 40 S lat; N boundary of ACC ACC powered by prevailing westerly wind belt “Roaring Forties, Furious Fifties, Screaming Sixties” Antarctic Convergence [Antarctic Polar Front]: 50 S lat: cold dense Antarctic meets and sinks below warm less-dense sub-antarctic waters. Marks N boundary of southern/Antarctic ocean East Wind Drift: surface current propelled by polar easterlies. E->W -most developed in Wedell and Ross seas. -directed toward Antarctica. closer to cont than ACC Antarctic divergence: around Antarctica where East wind drift scrapes ACC -much marine life during S hemis summer b.c of upwelling created here Gulf Stream: N along US coast. Best studied of all ocean currents. W-boundary current. 31-47m wide. Fastest in world. W boundary of gulf stream is abrupt. E boundary not so much. Sargossa Sea: the water that circulates round rotation center of N atlantic gyre. “stagnant eddy” transport off Chespeak bay 100 sverdrups [ more than 100x great than combined flow of all world rivers]: water from Sargossa sea combining with Florida current -this water from Sargossa sea returns at Newfoundland. meanders: snaked-like bends in current which often disconnect from gulf Stream and form large rotating masses of water called vortexes, eddies, or rings. -mechanisms that produce the dramatic water loss as Gulf S moves N yet to be determined warmcore rings: warm Sargossa sea water surrounded by cooler water. Shallow bowl-shaped, 1k deep. 68m wide. These spin off the Gulf Stream to the North, rotating CW coldcore rings: cold nearshore ring. cone-shaped. 2.2m deep. 310+ miles wide, increasing with depth, sometimes reaching sea floor. These spin off of Gulf Stream to the South, CCW. move SW 2-4m/day; often rejoin GS at Cape Hateras. Impact sea floor sed. -both rings: unique temp chars, biological pops; warm-water organism in cold ocean and visa versa; can survive as long as ring does, 2yrs sometimes.Coldcore rings last longer, and have more life. Ben Franklin postmaster discovered Gulf Stream. Labrador current: with the gulf stream form much fog in N atl, then break into Irminger current along Iceland’s W coast and Norweigan current moving N on Norway’s coast North Atlantic Current: crosses N atlantic. turns south to become canary current. Gulf Stream moderates E coast temp and N Europe temp, so temps across atlantic in Europe much higher even though on same lat, b/c of heat transfer from GS to Europe. Spain, Portugal at same lat as NE states. -as much as 20F warmer -the difference b/w S and N temp on E coast much greater than b/w N and S coasts of Europe. equatorial counter current of pacific better developed in pacific Walker Circulation Cell: in equatorial S pac: caused by pressure difference between W and E pacific. SE trade winds blow across pacific. -1920 effect first describe; Sir Gilbert Walker. Normal conditions: walker cell rotates CW. Low pressure in the West, high pressure in the E pacific warm pool: warm water flowing in equatorial regions creating a wedge of warm water on the western pacific. Thermocline below 100m -thermocline in E is generally within 30m of surface El Nino: current equatorial around Christmas: intense rainfall. CC air rotation southern oscillation: name given to phenomenon of E-W pressure seesaw accompanying the warm current. El Nino South Oscillation [ENSO] o El Nino; low pressure along equatorial regions in S America. SE trade winds diminish, sometimes reverse. CCW air rotation -warm pool flows back from west -begins to move in sept: at S American in dec/jan -water off S American coast up to 18F warmer than normal -sea lvl increase as much as 8in [thermal expansion along coast] -increases number of tropical storms -thermocline flattens; more horizontal -downwelling sometimes occurs -productivity diminishes, life reduced -high pressure replace Indonesian low; dry conditions -La nina [cool phase] -closer to normal conditions -stronger walker cell instead of reverse one -stronger trade winds -more upwelling -shallower thermocline in e pac -band of cooler than norm water stretch across equatorial S pac -commonly occur right after Nino ENSO Index: show alternating conditions since 1950 between Nina, Nino. -Calculated by atmospheric pressure, winds, sea surface temp -possitive numbers=Nino negative numbers=Nina zero=normal conds El Nino occurs avg every 2-10 years. Irregular pattern -lasts 12-18 months -some can last for years -more El Ninos in early 22nd century -most severe in 20th: 1982-1983 Pacific Decadal Oscillation [PDO]: lasts 20-30 yrs. Influence Pac surface temps -pac in warm stage of PDO from 1977-1999, just having entered cool phase [Marine Galapagos Iguanas shrink] -mild nino affect only S pac ocean. severe affect world temp -difficult to predict -can result in: flooding, erosion, droughts, fires, tropical storms, and effect marine life. La Nina sea surface temp and weather opposite of Nino El Nino events do occur in ocean basins Tropical Ocean-Global Atmosphere [TOGA]: 1985 study how El Nino event develop. predict el nino 1 yr Tropical Atmosphere and Ocean [TAO]: After TOGA: continues to monitor. 70 moored buoys. Indian counter current flow between 2 and 8 S of equator instead of N b/c Indian ocean is mostly in S hemis. monsoon: N Indian ocean wind pattern northeast monsoon; atmospheric masses off Asian continent into Indian ocean. From NE>SW during winter because of low heat capacity of land, continent heats faster than ocean in summer, creating low pressure area, resulting in the winds reversing: southwest monsoon: thought of as continuation of SE trade winds across equator. North equatorial current gone during summer, replaced by southwest monsoon current W to E Agulhas current: S along African coast, joins ACC Aghulas Retroflection: abrupt turn as current collide [ACC] deep ocean current affect 90% of ocean water. moves more water slower 6-12 miles per year. take 1 year for 1 hr travel of surface current for deep current thermohaline circulation: deep ocean circulation because differences in temperature and salinity cause dense differences density and salinity remain mostly unchanged in deep ocean temperature-salinity diagram: identify deep water masses by temperature, salinity, and density. isothermal water column makes for easier up and down welling. Antarctic bottom water: formed under sea ice in s subpolar lats in Antarctic continental margins. Sink down Antarctica continental slope. Densest water in open ocean. spreads into all ocean basins. returns to surface in 1000yrs. North Atlantic Deep Water: from: Irminger Sea, Labrador Sea, Med Sea, Norwegian sea. moves to all ocean basins. less dense; sits on top of Antarctic bottom water no sinking at subtrop convergences arctic convergences: mass sinking occurs antartic intermeiate water: formed sinking at Antarctic convergence. ;east studied water mass. no vertical mixing at low lat, much vertical much at high lat ocean common waters: mix of antarctic bottom water and north atlantic deep water. lines basins of Indian and pacific oceans because no access to N hemis deep water. surface water of pac to salin to sink, Indian too warm to sink difficult to identify where verticle flow to surface occurs. every liter water that sinks much rise supposedly greater in low lat areas also, deep water moving along rugged topography produces upwelling most intense deep water flow along western side due to coriolis and bathymetric features conveyer belt circulation: model combing deep and surface currents cold water dissolve more oxygen than warm water. in past, warm water probably was more a part of deep water conveyer belt circulation initiated in Atlantic. Chapter 7 Online Wrong o ocean currents driven and energized by solar heat o transfer 30% heat from tropics to poles o West Wind Drift part of: North pac gyre, S Atl gyre, Indian gyre o Surface water does NOT move at angle to wind direction o Ekman transport results in water piling at center of gyre o areas with well-developed pycnocline have little downwelling o NOT result of El Nino climate: inc water temp/destruction coral in E pac inc sea lvl E pac more hurricanes E pac o cold downwelling water=100 amazon river volumes. Chapter 8 o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o disturbing force: energy that cause ocean waves -rock thrown into pond: release of eng causes waves wind generates most waves; radiate in all directions waves created between fluids [water, air] and within them ocean waves: air-water interface [movement air across ocean] atmospheric waves: air-air interface. movement of different air masses. common at cold fronts. ripple-like clouds internal waves: water-water. movement of different water densities, along boundaries. associated with pycnocline. larger than ocean waves. can be seen from space. dangerous for submarines. can’t “break” except in essence. created by tidal movement, turbidity currents, wind stress, passing ships. sea floor movement->large waves waves are energy in motion. the energy moves within them but does not affect their movement. progressive waves: oscillate uniformly, travel without breaking: longitudinal, traverse, orbital longitudinal waves: [push-pull waves] particles push and pull in same direction the the energy travel sound is longitudinal waves longitudinal can be in all forms of matter traverse waves: [side to side] eng travel at right angles to direction of vibrating particles rope to doorknob, wave rope up and down to produce waves traverse only through solids longitudinal and traverse waves called body waves ocean waves are body waves, and since they involve aspects of longitudinal waves and traverse waves, they are orbital waves sine waves: idealized waveforms that do not exist in nature crests: high parts of waves trophs: low parts of waves still water lvl: halfway b/w crest and troph. zero energy lvl. lvl of water if not waves wave height [H]: verticle distance b/w crest and troph wavelength [L]: crest to crest. troph to troph. wave steepness: ratio of height to wavelength-> H/L exceeds 1/7, wave breaks, b/c it cannot support itself 1/7 is also the maximum height wave period [T]: time for 1 wavelength to pass a fixed position. typically 6-16s frequency: 1/T circular orbital motion: water moving in a circular motion to pass wave energy along floating objects move up and back as crest approached up and forward as it passes down and forward after it passes down and back as troph approaches. so, object moves in a circle to return to a spot slightly forward of its original position wave drift: orbit in the troph is slower than at the crest. accounts for slight forward movement. water particles orbit but waves more forward circular orbit of an object at surface has diameter=wavelength wave base: where circular orbital movement is negligible= L/2, measured from still water lvl. longer the wave, deeper the base easier to swim below waves than to fight them at the surface o o o o o o o o o o o o o o o o o o o o o o o o o o deep water waves: if water depth [d]> L/2. have no interference with ocean bottom wave speed [S]: rate at which a wave travels L/T. celerity celerity used only in relation to waves no mass moving, just wave form speed depends on wavelength longer the wavelength, faster the wave travels so, fast wave not neceissarily have great height, b/c S only dependent on L shallow water waves: wave with d<1/20 of L. long waves S=d/T ocean floor interferes with their orbital motion speed of these waves influenced by gravitational acceleration [g] and depth [d]. mostly by depth deeper the water, faster the wave include: tsunami, tides, and wind-generated waves moved into shallow nearshore areas. tsunami, tides very long L [greater so than ocean depth] particle movement: flat elliptical orbit transitional waves: some characteristics of shallow and deep water waves. L b/w 2 and 20 times the water depth. Speed depends on L and d. wind creates pressure, stress capillary waves: L-1.74cm. ripples. small, rounded, v-shaped troph restoring force: destroy capillary waves, restore smooth surface. Capillarity dominant gravity waves: symmetric waves with L>1.74cm. gravity more dominant restoring force. L is 15-35x their height. trochoidal waveform. “Sea”: where wind-driven waves are generated. choppy, many direc. energy in waves: 1] wind speed 2] duration [of wind in 1 direction] 3]fetch [distance wind blows] whitecaps: open ocean breakers Beaufort Wind Scale: describes all appearances of sea sir Francis Beaufort of British Navy Ramapo and wave H 1935 fully developed sea: equilibrium condition. when waves can no longer grow swells: long-crested part of “sea.” waves that have traveled out of their area of origination reason for waves at windless shore wave trains: groups of waves that follow out of the sea area the faster waves wave dispersion: the sorting of waves by their L longer waves outrun shorter waves decay distance: distance waves change from choppy sea to uniform swell. can be hundred miles as train moves, front wave disappears over and over, but # of waves remain, b/c new wave forms in back of train train moves at ½ velocity of any individual wave in group, b/c of this progression interference patterns: swells from different storms run together. sum of disturbance that each wave would have produced individually. constructive interference; wave with same L->crest to crest, troph to troph-> height increases destructive interference: wave with same L->crest to troph->height decreases mixed interference: different L surf beat: varied sequence of high and lower waves surf zone: zone of breaking wave at continental margins shoaling: becoming shallower any sunken obstacle causes waves to lose energy breaking wave indicates shallow water o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o wave speed decreases as water shoal. L decreases. H increases. increase wave steepness [breaks at 1/7] swell from far off storm break near shore. parallel lines of uniform breakers local wind waves not swell break further off shore; rough, choppy, irregular depth of water where waves breaking is 1.33x breaker height waves break in surf zone because particle motion at bottom of wave restricted bottom wave slower than top, which subsequently topples over rogue waves: unusually large waves spilling breaker: turbulent mass of air and water running down slope of wave. low overall eng. result at gently sloped ocean bottoms. long, boring surfing. plunging breaker: curling crest move over air pocket. particles in crest outrun the wave. form on steep beach slopes. surging breaker: build up and break right at shoreline. caused by abrupt slope. refraction: bending of each wave crest as wave approaches shore waves bend almost parallel to shore refratction of waves along irregular shoreline distributes wave energy unevenly along shore orthogonal lines: wave rays. indicate direction waves travel: spread so that energy between lines is equal at all time. -converge on headlands jutting into sea -diverge in bays wave reflection¨: wave reflected back into ocean with min loss of eng. reflected most often at angle. the wedge: W of jetty that protects harbor entrance at Newport, Cali. standing waves: stationary wave. produced by waves reflecting at 90 deg. sum of 2 waves with ame L traveling in dir directions. no circular motion. nodes; no movement. horizontal antinodes; movement. vertical tsunami: large destructive waves. NOT tidal waves. seismic sea waves most cause by fault movement; vertical, not horizontal displacement. splash waves: above water landslides or meteor impact tsunamis tsunami L-125miles avg can be felt 62 miles deep. S=435mph in opean ocea. 5meteres high they are more like an increase/decrease in sea lvl than a breaking wave typically are a series of waves. largest surface in generally the later surge extremely large/destructive every 15-20years. 57 noticeable tsunami per decade. 86% in pacific. Krakatu eruption [1883] 36k dead from tsunami. Pacific Tsunami Warning Center [PTWC]: coordinates infor from 25 pacific rim countries. HQ in hawii. 50 measuring stations tsunamigenic->capable of producing tsunami transform faults do not create tsunami best to move ships out to sea open ocean 10 megawatts per .6m of shoreline with wave power harnessing LIMPET 500: 1st commercial wave power plant. 2000 more wave energy along W coast than E coast. largest waves associated with prevailing westerlies. Chapter 8 Wrong o internal wave occur at strong steady pycnocline most o tsunami from Hawaii 5 hours to reach W coast. o surf zone is where waves are actively breaking o velocity of wave decreases once it touches bottom o wave fronts of storms are beyond the “limit of the storm” o storms and tidal movements are also disturbing forces o o o o o o o o ocean waves cannot: be described by the way they form, be described by T, L, H, and not by the way they form Orbital waves=Swell!!!!! ocean waves are oribital waves body waves: longitudinal and traverse 1 meter high tsunami with a bigger wave base than 1000m long wave we can determine S if we know L, T, F either interferences [destruc, construc] caused by either refraction or reflection Chapter 9 tides: periodic raising and lower of avg sea lvl. 450 BC Hertodotus observe tides in writing. Issac Newton 1642-1727 universal law gravitation barycenter: 1k miles beneath surface earth. earth and moon rotate around these. gravity pulls all water on earth to moon and sun tides generated by forces imposed on earth generated by combination of gravity and motion among earth, moon and sun gravitational force: derived from Newton’s law: every particle of mass in the universe attracts every other particle if mass increases, gravitational force increases if distance increases, gravitational force greatly decreases the greater the mass of objects and the closer they are, the greater they attract zenith: pt closest to moon, greatest grav attraction nadir: pt furthest from moon, weakest grav attraction at angles. causing grav attraction b/w each particle and moon be slightly different centripetal force: required to keep planets in orbit. inward center-seeking force. provided by grav attraction b/w planets and sun broken string, ball flies tangent to orbital pattern gravity supplies centripetal force particles identical mass rotate in identical sized paths due to E moon rot sys each req identical centrip force to maintain circular path supplied force: [gravitational attraction between particle and moon] dif from required force [b/c grav att varies with ditance from moon] resultant forces: b/c of above difference. the mathematical dif between two sets of arrows [centripetal force=req force; gravitational force=supplied force] red arrow to black area at pt of beginning avg 1 million the magn E grav if res force vertical; at nadir and zenith arrow outward, and along “equator” N and S arrows downward. no tide effect tide-generating forces: if resultant force significant horizontal to E surface: produce tidal bulges. small forces, but max at 45deg relative to NS “equator” gravitational attraction inversely proportionate to the square of the distance between two masses. tide-gen force inversely proporationate to the ccube of the distance between each point on earth and center of moon or sun distance more highly weighed variable for tide-gen force tide-gen force pushes water into bulges oat zenith and nadir [Lunar bulges] side facing moon bulge is because grav force>centripetal. side away from moon is because centripetal>grav force. bulges are equal. all pts on earth experience 2 tides per day except the poles atmospheric tides: can be miles high. solid-body/Earth tides: within interior of Earth; stretch skin of earth by centimeters there is tide in glass of water tidal period: time b/w each tide [2 per day] 12 hours ideally at equator lunar day: 24hr 50m, moon overhead to overhead solar day: 24hr, sun overhead to overhead moon rises 50min later each day, high tides occur 50 mins later each consecutive day. solar bulges: caused by sun; at closest and furthest distance from thereof sun 27mx bigger than moon sun tidal attract is less than moon because sun is 390x farther from earth solar bulges 46% of lunar bulges flood tide: tides appear move toward shore ebb tide: away shore but; earth’s rotation carries various location into and out of the tidal bulges, which are fixed relative to sun and moon monthly tidal cycle 29.5 days; this is how long it take moon to orbit earth new moon: moon between earth and sun; can’t be seen at night/ conjunction full moon: moon opposite side of sun. fully visible. opposition quarter moon: half lit half dark. moon at 90 deg angles with E relative to sun tidal range: vertical difference between high and low tides very large at new and full moons spring tide: max tidal range. 2x per month syzygy: call the moon during full and new. at quarter moon, lunar/solar tide working at right angles neap tide: small tidal range; destructive interference quadrature: call the moon at quarter moon time b/w spring tides or neap tides is ½ monthly lundar cycle: 2 weeks time b/w spring and neap tides is ¼ monthly lunar cycle: 1 week waxing crescent: new moon to first quarter moon waxing gibbous: first quarter moon to full moon waning gibbous: full moon to third-quarter waning crescent: third quarter to new moon moon has synchronous rotation: identical periods of rotation “blue moon” once every 2.72 years. declination: angular distance of sun or moon above or below Earth’s equatorial plane ecliptic: imaginary plane containing the invisible ellipse on which E revolves around the sun. max declination of sun relative to Earth’s equator is 23.5 plane of moon’s orbit tilted 5deg with respect to ecliptic so, max declination of moons orbit relative to Earths equator= 28.5 changes dec from N to S during the miltiple lunar cycles within 1 year so, tidal bulges are rarely aligned with the equator [as is ideal] earth 92.2million miles from sun during N hemis winter. 94.5 million miles during summer distance b/w E and sun varies 2.5% over course of year perihelion: earth nearest to sun. tidal ranges large. January aphelion: earth furthest from sun. tidal ranges small greatest tidal ranges in Jan each year moon around earth elliptical, E-M distance varies 8% perigee: moon closest to earth. largest tidal ranges apogee: moon furthest from earth. smallest tidal ranges moon cycle: perigee, apogee, back to perigee every 27.5 days proxigean: spring tide coincide with perigee. especially high tides. storms heavy dmg now. also, spring tide graeter range during N hemis winter max spring tide once every 1600 yrs declination of moon determines position of tidal bulges neither the 2 high or 2 low tides of same H b/c of declination of moon and sun tidal moves more as forced waves with their speed determined by ocean depth 435mph avg. bulges don’t exists, because they’re too slow cells: what ocean tides break up into instead amphidromic point: near center of each cell, around which crests and trophs of tide wave rotate. no tidal range here cotidal lines: radiate from amphidromic point: connects point where high tide occurs simultaneously. tide wave rotates CCW in N hemis, CW in S hemis wave complete 1 rotation during tidal period [12 lunar hours] limits size of cells. low occurs 6 hrs after high in amph cell high on “10” cotidal line, low must be occurring on “4” cotidal line of cell inc turbulence and mixing strongly affect tides. tidal waves breaking conts produces internal waves over 150 factors affect tides at given coast effect: high tide rarely occurs when moon at apogee. vary place to place mathematical model beyond limits of scientists diurnal tidal pattern: single high and low tide each lunar day. tidal period= 24hr 50m. common in shallow inland seas semidiurnal tidal pattern: 2 high and low tides each luner day. H of successive H and L tides approx the same, NEVER exactly. tidal period: 12hr, 25m common along atlantic coasts of us mixed tidal pattern: character of both above. successive H and L very different H [condition called diurnal inequality]. Tidal period typically 12hr 25m, but can exhibit diurnal period too. most common type; pac coast N America bay of Fundy: largest tidal range rotary current: produced by current rotation CCW in N hemis basin. In open portion of basin reversing current: moves into and out of restricted passages along coast. caused by increased friction in nearshore shoaling waters. once a rotary current. rotary currents less .6mph. reversing currents up to 28mph in restricted channels. rev currents in mouths of bays flood current: produced when water rush into bay/river with incoming high tide. ebb current: produced when water drains from bay/river because low tide approaching high slack water: occurs at peak of each high tide low slack water: peak of each low tide during these times, no currents occur more some minutes reversing currents cause navigational hazards, but prevent sed build-up and replenish bay nutrients tidal current significant even at depths whirlpool/vortex: rapidly spinning body of water. cause by rev currents. most common in shallow passages connecting 2 large bodies water with difference tidal patterns/cycles up to 10 mph Maelstrom off N coast Norway is strongest in world Datum: MLLW; avg of 2 low slack waters tidal bore: wall of water that moves up low-lying rivers due to incoming tide. to 5m high/14 mph. develop where large tidal range, loww-lying river exists. due to resistance of river flow. Chientang River [China] has the largest bore. grunion: slender silvery fish that spawns on land. Chapter 9 Wrong no neap tide during solar eclipse open ocean tidal current rotary strongest gravitational force=highest tide go collecting during spring tide [great tidal range] ideal high tide interval; 12hr 25m force of gravity not related to velocity plane of solar system= eclictic plane moon over equator will not describe tropical tides tidal waves are thousands of kilometers, and are deep water waves centripetal force act perpendicular to the solar gravitational force side of earth closest to sun, high tides not form due to gravitational forces tidal forces not greatest at sygyzy semidiurnal tides result in 2 predicatable lows every day Chapter 10 US 80% pop coastal waves crash on most coasts 10k per day shore: zone between lowest tide lvl and highest elevation on land affected by storm waves coast: inland from shore as far as ocean-related features can be found shore and coast greatly vary coastline: boundary between shore and coast backshore: above high tide shoreline-> water covered only during storms foreshore: submerged at high tide, exposed at low tide. shoreline: water’s edge. follows tide nearshore: seaward from low tide shoreline to low tide breaker line -never exposed. affected by waves offshore zone: beyond low-tide breakers. waves rarely affect bottom beach: a deposit of the shore area wave-cut bench: flat, wave-eroded surface bench is the entire active area of coast that experience changes due to breaking waves recreational beach: area of beach above shoreline berm; dry, gently sloping region at foot of coastal cliffs or dunes. beach face: wet, sloping surface extend from berm to shoreline more exposed low tide. also called low tide terrace longshore bars: beyond beach face: 1 or more; sand bars parallel coast. these “trip” water longshore troph: separate longshore bar from beachface. notch: between coastline and berm. order: coastline-notch-berm-high tide shoreline-beach face-low tide shoreline-wace cut bench-longshore troph-longshore bar-low tide breaker line beach sediment finer from rivers that drain lowland areas than highland areas mud coasts: Suriname, SW India beaches: material in transit along shoreline movement parallel and perpendicular to coast swash: water from broken wave running up beach face. soaks in. backwash: drains back. picking up sed whichever is dominant dictates deposition or erosion light wave activity – more swash. wide, developed beach heavy wave activity-less swash, more backwash. New wave swash on top of old wave backwash. removed sand creates bars Chapter 10 wrong a beach on low relief tropical island made mostly of calcium carbonate isostatic rebound CANNOT produce global sea lvl rise barrier flat is the woodland above the salt marshes, which are closest to lagoon shore includes from low tide line to notch COPYRIGHT 2007 BY LITERAL, INC.